An investigation of relatively light (GeV-scale), long-lived right-handed neutrinos is performed within minimal left-right symmetric models using the neutrino-extended Standard Model Effective Field Theory framework. Light sterile neutrinos can be produced through rare decays of kaons, $D$-mesons, and $B$-mesons at the Large Hadron Collider (LHC) and the Long-Baseline Neutrino Facility (LBNF) of Fermilab. Their decays could result in displaced vertices, which can be reconstructed. By performing Monte-Carlo simulations, we assess the sensitivities of the future LHC far-detector experiments ANUBIS, CODEX-b, FACET, FASER(2), MoEDAL-MAPP1(2), MATHUSLA, the recently approved beam-dump experiment SHiP, and the upcoming neutrino experiment DUNE at the LBNF, to the right-handed gauge-boson mass $M_{W_R}$ as functions of neutrino masses. We find that DUNE and SHiP could be sensitive to right-handed gauge-boson masses up to $\sim 25$ TeV. We compare this reach to indirect searches such as neutrinoless double beta decay, finding that displaced-vertex searches are very competitive.
Proton decay, although unobserved so far, is a natural expectation when attempting to explain the baryon asymmetry of the universe. $p\to K^+\bar{\nu}$ or $p\to K^+\tilde{\chi}_1^0$, with $\tilde{\chi}_1^0$ a light exotic neutral particle, represent possible decay channels achievable in models of physics beyond the Standard Model, such as the MSSM with trilinear R-parity-violating terms, or the Standard Model extended by a heavy neutral lepton. Among the decay products of these modes, the neutral fermions would typically appear as missing energy in collider searches. The present study considers how such decay modes could be differentiated in experimental settings, as the exotic $\tilde{\chi}_1^0$ may further decay if it is not protected by a symmetry (such as R-parity in the MSSM). We assess the detection prospects of the proposed experiments DUNE, JUNO and Hyper-K in this context.
At the Deep Underground Neutrino Experiment (DUNE), a proton beam hits a fixed target leading to large production rates of mesons. These mesons can decay and potentially provide a source of long-lived neutral fermions. Examples of such long-lived fermions are heavy neutral leptons which can mix with the standard-model active neutrinos, and the bino-like lightest neutralino in R-parity-violating supersymmetry. We show that the Standard Model Effective Field Theory extended with right-handed singlet neutrinos can simultaneously describe heavy neutral leptons and bino-like neutralinos in a unified manner. We use the effective-field-theory framework to determine the sensitivity reach of the DUNE near detector in probing various scenarios of long-lived neutral fermions.
Sep 08 2023
hep-ph arXiv:2309.03727v1
Recently, Belle II announced evidence for the decay $B^+\to K^+ \nu \bar{\nu}$ at $3.6\sigma$ significance, and measured the corresponding decay branching ratio to be $2.4\times 10^{-5}$, which is $2.8\sigma$ above the standard-model prediction. Here, we provide a theoretical explanation based on a massless bino in R-parity-violating (RPV) supersymmetry. With a single non-vanishing RPV coupling $\lambda'_{i23/i32}$, $\lambda'_{i13/i33}$, or $\lambda'_{i12/i22}$, where $i=1,2,3$, the decay $B^+\to K^+ \overset{\scriptscriptstyle(-)}{\nu} \tilde{\chi}^0_1$ can be induced, which would lead to the same signature as $B^+\to K^+ \nu \bar{\nu}$. Taking into account both theoretical and experimental uncertainties, we derive the parts of the parameter space of the RPV coupling and sfermion masses that could accommodate the new measurement at various significance levels.
In R-parity-violating (RPV) supersymmetric models, light neutralinos with masses from the GeV-scale down to even zero are still allowed by all laboratory constraints. They are further consistent with dark matter observations, as they decay via RPV couplings. These RPV couplings are in general constrained to be small. Hence, such light neutralinos, if produced, e.g., at a beam-dump or collider experiment, appear as displaced vertices or missing energy at the detector level. The same signatures have been extensively searched for at various experiments in the theoretical context of sterile neutrinos which mix with active neutrinos. In this work, we recast the sensitivity of both past and present experiments to sterile neutrinos to obtain new bounds on RPV couplings associated with a light neutralino. We find experiments such as T2K, BEBC, FASER, DUNE, and MoEDAL-MAPP can improve the current bounds on RPV couplings by up to $3-4$ orders of magnitude in several benchmark scenarios.
In this paper, we propose a dedicated forward detector, FOREHUNT (FORward~Experiment~for~HUNdred~TeV), for 100 TeV FCC-hh for the detection of light long-lived particles (LLP) coming from $B$-meson decay. We calculate the signal acceptance as a function of mass and proper decay length of the LLP for 100 TeV and interpret our result in terms of model parameters for models of dark Higgs scalar and heavy neutral leptons. We also compare the sensitivity with proposed transverse detectors like MATHUSLA, CODEX-b for HL-LHC, and DELIGHT (Detector for long-lived particles at high energy of 100 TeV) for FCC-hh. Our analysis reveals that if the LLP is light ($\lesssim 4.4$ GeV) and has a low proper decay length ($<10$ m), a forward detector like FOREHUNT is the best option to look for the decaying LLP, while DELIGHT is preferable for higher proper decay lengths.
We perform a classification of all potential supersymmetric $R$-parity violating signatures at the LHC to address the question: are existing bounds on supersymmetric models robust, or are there still signatures not covered by existing searches, allowing LHC-scale supersymmetry to be hiding? We analyze all possible scenarios with one dominant RPV trilinear coupling at a time, allowing for arbitrary LSPs and mass spectra. We consider direct production of the LSP, as well as production via gauge-cascades, and find 6 different experimental signatures for the $LL\bar E$-case, 6 for the $LQ\bar D$-case, and 5 for the $\bar U\bar D\bar D$-case; together these provide complete coverage of the RPV-MSSM landscape. This set of signatures is confronted with the existing searches by \textttATLAS and \textttCMS. We find all signatures have been covered at the LHC, although not at the sensitivity level needed to probe the direct production of all LSP types. For the case of a dominant $LL\bar E$-operator, we use \textttCheckMATE to quantify the current lower bounds on the supersymmetric masses and find the limits to be comparable to or better than the $R$-parity conserving case. Our treatment can be easily extended to scenarios with more than one non-zero RPV coupling.
Oct 17 2022
hep-ph arXiv:2210.07253v1
The $R$-parity-violating Minimal Supersymmetric Standard Model (RPV-MSSM) can naturally accommodate massive neutrinos as required by the oscillation data. However, studying the phenomenology is complicated due to the large number of undetermined parameters involved. Thus, studies are usually restricted to specific submodels. In this work, we develop an approach that allows us to be less restrictive. Working in (almost) the completely general RPV-MSSM setting, we analyze the structure of the neutrino mass matrix, and identify -- for the case of two massive neutrinos -- only four minimal classes of structures that can solve the neutrino data; we call these Minimal Oscillation Models (MOMs). We study the general features of each MOM class, and present numerical fits to the oscillation data. Our approach allows us to study all RPV models satisfying the neutrino data in a unified manner, as long as they satisfy the MOM criteria. Through several examples, we show that this indeed holds for many interesting scenarios.
In this work, we propose a search for a single photon at \textttFASER and \textttFASER2, produced from decays of bino-like, sub-GeV lightest neutralinos in the theoretical framework of the R-parity-violating (RPV) Minimal Supersymmetric Standard Model (MSSM). We consider a list of representative benchmark scenarios with one or two non-vanishing RPV couplings. The photon has an energy $\mathcal{O}\left(0.1\right)-\mathcal{O}\left(1\right)$ TeV. We find a sensitivity reach for RPV couplings beyond the current bounds by orders of magnitude at \textttFASER and \textttFASER2.
May 18 2022
hep-ph arXiv:2205.08141v2
We study the phenomenology associated with a light bino-like neutralino with mass under the tau mass in the context of the R-parity violating Minimal Supersymmetric Standard Model. This is a well-motivated example of scenarios producing potentially light and long-lived exotic particles, which might be testable in far-detector experiments, such as the FASER experiment at the Large Hadron Collider. A quantitative assessment of the discovery potential or the extraction of limits run through a detailed understanding of the interactions of the light exotic fermion with Standard Model matter, in particular, the hadronic sector. Here, we propose a systematic analysis of the decays of such a particle and proceed to a model-independent derivation of the low-energy effects, so that this formalism may be transposed to other UV-completions or even stand as an independent effective field theory. We then stress the diversity of the possible phenomenology and more specifically discuss the features associated with the R-parity violating supersymmetric framework, for example neutron-antineutron oscillations.
Jonathan L. Feng, Felix Kling, Mary Hall Reno, Juan Rojo, Dennis Soldin, Luis A. Anchordoqui, Jamie Boyd, Ahmed Ismail, Lucian Harland-Lang, Kevin J. Kelly, Vishvas Pandey, Sebastian Trojanowski, Yu-Dai Tsai, Jean-Marco Alameddine, Takeshi Araki, Akitaka Ariga, Tomoko Ariga, Kento Asai, Alessandro Bacchetta, Kincso Balazs, et al (216) High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). In this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. FPF experiments will be sensitive to a broad range of BSM physics through searches for new particle scattering or decay signatures and deviations from SM expectations in high statistics analyses with TeV neutrinos in this low-background environment. High statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. We report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the FPF's physics potential.
A final state consisting of one charged lepton, at least one jet, and little missing transverse energy can be a very promising signature of new physics at the LHC across a wide range of models. However, it has received only limited attention so far. In this work we discuss the potential sensitivity of this channel to various new physics scenarios. To demonstrate our point, we consider its application to lepton parton density functions (PDFs) at the LHC in the context of supersymmetry. These lepton PDFs can lead to resonant squark production (similar to leptoquarks) via lepton number violating couplings present in R-parity Violating Supersymmetry (RPV-SUSY). Unlike leptoquarks, in RPV-SUSY there are many possible decay modes leading to a wide range of signatures. We propose two generic search regions: (a) A single first or second generation charged lepton, exactly 1 jet and low missing transverse energy, and (b) A single first or second generation charged lepton, at least 3 jets, and low missing transverse energy. We demonstrate that together these cover a large range of RPV-SUSY signatures, and have the potential to perform better than existing low-energy bounds, while being general enough to extend to a wide range of possible models hitherto not explored at the LHC.
Large numbers of $\tau$ leptons are produced at Belle II. These could potentially decay into sterile neutrinos that, for the mass range under consideration, are typically long-lived, leading to displaced-vertex signatures. Here, we study a displaced-vertex search sterile-neutrino-extended Standard Model Effective Field Theory. The production and decay of the sterile neutrinos can be realized via either the standard active-sterile neutrino mixing or higher-dimensional operators in the effective Lagrangian. We perform Monte-Carlo simulations to estimate the Belle II sensitivities to such interactions. We find that Belle II can probe non-renormalizable dimension-six operators involving a single sterile neutrino up to a few TeV in the new-physics scale.
Luis A. Anchordoqui, Akitaka Ariga, Tomoko Ariga, Weidong Bai, Kincso Balazs, Brian Batell, Jamie Boyd, Joseph Bramante, Mario Campanelli, Adrian Carmona, Francesco G. Celiberto, Grigorios Chachamis, Matthew Citron, Giovanni De Lellis, Albert De Roeck, Hans Dembinski, Peter B. Denton, Antonia Di Crecsenzo, Milind V. Diwan, Liam Dougherty, et al (61) The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.
Dec 23 2020
hep-ph arXiv:2012.11623v1
We present a reanalysis of nucleon decay in the context of the R-parity violating MSSM, updating bounds on R-parity violating parameters against recent experimental and lattice results. We pay particular attention to the derivation of these constraints and specifically to the hadronic matrix elements, which usually stand as the limiting factor in order to derive reliable bounds, except for these few channels that have been studied on the lattice.
Shehu S. AbdusSalam, Fruzsina J. Agocs, Benjamin C. Allanach, Peter Athron, Csaba Balázs, Emanuele Bagnaschi, Philip Bechtle, Oliver Buchmueller, Ankit Beniwal, Jihyun Bhom, Sanjay Bloor, Torsten Bringmann, Andy Buckley, Anja Butter, José Eliel Camargo-Molina, Marcin Chrzaszcz, Jan Conrad, Jonathan M. Cornell, Matthias Danninger, Jorge de Blas, et al (55) Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at https://doi.org/10.5281/zenodo.4322283.
Oct 16 2020
hep-ph arXiv:2010.07305v2
We study the prospects of a displaced-vertex search of sterile neutrinos at the Large Hadron Collider (LHC) in the framework of the neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT). The production and decay of sterile neutrinos can proceed via the standard active-sterile neutrino mixing in the weak current, as well as through higher-dimensional operators arising from decoupled new physics. If sterile neutrinos are long-lived, their decay can lead to displaced vertices which can be reconstructed. We investigate the search sensitivities for the ATLAS/CMS detector, the future far-detector experiments: AL3X, ANUBIS, CODEX-b, FASER, MATHUSLA, and MoEDAL-MAPP, and at the proposed fixed-target experiment SHiP. We study scenarios where sterile neutrinos are predominantly produced via rare charm and bottom mesons decays through minimal mixing and/or dimension-six operators in the $\nu$SMEFT Lagrangian. We perform simulations to determine the potential reach of high-luminosity LHC experiments in probing the EFT operators, finding that these experiments are very competitive with other searches.
Aug 19 2020
hep-ph arXiv:2008.07539v2
In R-parity-violating supersymmetry the lightest neutralino can be very light, even massless. For masses in the range $500$ MeV$\lesssim m_{\tilde\chi^0_1}\lesssim 4.5$ GeV the neutralino can be produced in hadron collisions from rare meson decays via an R-parity violating coupling, and subsequently decay to a lighter meson and a charged lepton. Due to the small neutralino mass and for small R-parity violating coupling the lightest neutralino is long-lived, leading to displaced vertices at fixed-target and collider experiments. In this work, we study such signatures at the proposed experiments ANUBIS and MAPP at the LHC. We also compare their sensitivity reach in these scenarios with that of other present and proposed experiments at the LHC such as ATLAS, CODEX-b, and MATHUSLA. We find that ANUBIS and MAPP can show complementary or superior sensitivity.
Jan 16 2020
hep-ph arXiv:2001.05000v1
We consider pair production of LSP staus at the LHC within R-parity violating supersymmetry. The staus decay into Standard Model leptons through the LLĒ operator. Using CheckMATE we have recast multileptonic searches to test such scenarios. We show for the first time that using these analyses the stau mass can be constrained up to 345 GeV, depending on the stau decay mode, as well as the stau mixing angle. However, there is for all scenarios a significant gap between the lower LEP limit on the stau mass and the onset of the LHC sensitivity. This approach can be used in the future to constrain the stau sector in the context of RPV lepton-number violating models.
Nov 07 2018
hep-ph arXiv:1811.01995v1
Recently Gligorov $\textit{et al.}$ [arXiv:1810.03636] proposed to build a cylindrical detector named '$\texttt{AL3X}$' close to the $\texttt{ALICE}$ experiment at interaction point (IP) 2 of the LHC, aiming for discovery of long-lived particles (LLPs) during Run 5 of the HL-LHC. We investigate the potential sensitivity reach of this detector in the parameter space of different new-physics models with long-lived fermions namely heavy neutral leptons (HNLs) and light supersymmetric neutralinos, which have both not previously been studied in this context. Our results show that the $\texttt{AL3X}$ reach can be complementary or superior to that of other proposed detectors such as $\texttt{CODEX-b}$, $\texttt{FASER}$, $\texttt{MATHUSLA}$ and $\texttt{SHiP}$.
Oct 22 2018
hep-ph arXiv:1810.08228v2
We update the bounds on $R$-parity violating supersymmetry originating from meson oscillations in the $B^0_{d/s}$ and $K^0$ systems. To this end, we explicitly calculate all corresponding contributions from $R$-parity violating operators at the one-loop level, thereby completing and correcting existing calculations. We apply our results to the derivation of bounds on $R$-parity violating couplings, based on up-to-date experimental measurements. In addition, we consider the possibility of cancellations among flavor-changing contributions of various origins, e.g. from multiple $R$-parity violating couplings or $R$-parity conserving soft terms. Destructive interferences among new-physics contributions could then open phenomenologically allowed regions, for values of the parameters that are naively excluded when the parameters are varied individually.
Oct 10 2018
hep-ph arXiv:1810.03617v2
The $LQ\bar D$ operator in R-parity-violating supersymmetry can lead to meson decays to light neutralinos and neutralino decays to lighter mesons, with a long lifetime. Since the high-luminosity LHC is expected to accumulate as much as 3/ab of data, several detectors proposed to be built at the LHC may probe unexplored regions in the parameter space, for long-lived neutralinos. We estimate the sensitivity of the recently proposed detectors, CODEX-b, FASER, and MATHUSLA, for detecting such light neutralinos singly produced from $D$- and $B$-meson decays in a list of benchmark scenarios, and discuss the advantages and disadvantages of the proposed detectors in this context. We also present our results in a model independent fashion, which can be applied to any long-lived particle with mass in the GeV regime.
Jul 10 2018
hep-ph arXiv:1807.02530v1
We propose a complete R-parity violating supersymmetric model with baryon triality that contains a Dine-Fischler-Srednicki-Zhitnitsky axion chiral superfield. We parametrize supersymmetry breaking with soft terms, and determine under which conditions the model is cosmologically viable. As expected we always find a region of parameter space in which the axion is a cold dark matter candidate. The mass of the axino, the fermionic partner of the axion, is controlled by a Yukawa coupling. When heavy [${\mathcal O}$(TeV)], the axino decays early and poses no cosmological problems. When light [$\mathcal{O}$(keV)] it can be long lived and a warm dark matter candidate. We concentrate on the latter case and study in detail the decay modes of the axino. We find that constraints from astrophysical X- and gamma rays on the decay into photon and neutrino can set new bounds on some trilinear supersymmetric R-parity violating Yukawa couplings. In some corners of the parameter space the decays of a relic axino can also explain a putative 3.5 keV line.
We investigate the phenomenology of the MSSM extended by a single R-parity violating coupling at the unification scale. For all R-parity violating couplings, we discuss the evolution of the particle spectra through the renormalization group equations and the nature of the lightest supersymmetric particle (LSP) within the CMSSM, as an example of a specific complete supersymmetric model. We use the nature of the LSP to classify the possible signatures. For each possible scenario we present in detail the current LHC bounds on the supersymmetric particle masses, typically obtained using simplified models. From this we determine the present coverage of R-parity violating models at the LHC. We find several gaps, in particular for a stau-LSP, which is easily obtained in R-parity violating models. Using the program CheckMATE we recast existing LHC searches to set limits on the parameters of all R-parity violating CMSSMs. We find that virtually all of them are either more strongly constrained or similarly constrained in comparison to the R-parity conserving CMSSM, including the $\bar U\bar D\bar D$ models. For each R-parity violating CMSSM we then give the explicit lower mass bounds on all relevant supersymmetric particles.
Herbi K. Dreiner, Max Becker, Mikolaj Borzyszkowski, Maxim Braun, Alexander Faßbender, Julia Hampel, Maike Hansen, Dustin Hebecker, Timo Heepenstrick, Sascha Heinz, Katharina Hortmanns, Christian Jost, Michael Kortmann, Matthias U. Kruckow, Till Leuteritz, Claudia Lütz, Philip Mahlberg, Johannes Müllers, Toby Opferkuch, Ewald Paul, et al (9) We present the screenplay of a physics show on particle physics, by the Physikshow of Bonn University. The show is addressed at non-physicists aged 14+ and communicates basic concepts of elementary particle physics including the discovery of the Higgs boson in an entertaining fashion. It is also demonstrates a successful outreach activity heavily relying on the university physics students. This paper is addressed at anybody interested in particle physics and/or show physics. This paper is also addressed at fellow physicists working in outreach, maybe the experiments and our choice of simple explanations will be helpful. Furthermore, we are very interested in related activities elsewhere, in particular also demonstration experiments relevant to particle physics, as often little of this work is published. Our show involves 28 live demonstration experiments. These are presented in an extensive appendix, including photos and technical details. The show is set up as a quest, where 2 students from Bonn with the aid of a caretaker travel back in time to understand the fundamental nature of matter. They visit Rutherford and Geiger in Manchester around 1911, who recount their famous experiment on the nucleus and show how particle detectors work. They travel forward in time to meet Lawrence at Berkeley around 1950, teaching them about the how and why of accelerators. Next, they visit Wu at DESY, Hamburg, around 1980, who explains the strong force. They end up in the LHC tunnel at CERN, Geneva, Switzerland in 2012. Two experimentalists tell them about colliders and our heroes watch live as the Higgs boson is produced and decays. The show was presented in English at Oxford University and University College London, as well as Padua University and ICTP Trieste. It was 1st performed in German at the Deutsche Museum, Bonn (5/'14). The show has eleven speaking parts and involves in total 20 people.
Jun 29 2016
hep-ph arXiv:1606.08811v2
It has been proposed that the observed diphoton excess at 750 GeV could be explained within the constrained minimal supersymmetric standard model via resonantly produced stop bound states. We reanalyze this scenario critically and extend previous work to include the constraints from the stability of the electroweak vacuum and from the decays of the stoponium into a pair of Higgs bosons. It is shown that the interesting regions of parameter space with a light stop and Higgs of the desired mass are ruled out by these constraints. This conclusion is not affected by the presence of the bound states because the binding energy is usually very small in the regions of parameter space which can explain the Higgs mass. Thus, this also leads to strong constraints on the diphoton production cross section which is in general too small.
Nov 25 2015
hep-ph arXiv:1511.07436v1
We study the sensitivity of the proposed SHiP experiment to the LQD operator in R-parity violating supersymmetric theories. We focus on single neutralino production via rare meson decays and the observation of downstream neutralino decays into charged mesons inside the SHiP decay chamber. We provide a generic list of effective operators and decay width formulae for any LQD coupling and show the resulting expected SHiP sensitivity for a widespread list of benchmark scenarios via numerical simulations. We compare this sensitivity to expected limits from testing the same decay topology at the LHC with ATLAS.
Philip Bechtle, Jose Eliel Camargo-Molina, Klaus Desch, Herbert Dreiner, Matthias Hamer, Michael Kramer, Ben O'Leary, Werner Porod, Bjoern Sarrazin, Tim Stefaniak, Mathias Uhlenbrock, Peter Wienemann Aug 26 2015
hep-ph arXiv:1508.05951v1
We investigate the constrained Minimal Supersymmetric Standard Model (cMSSM) in the light of constraining experimental and observational data from precision measurements, astrophysics, direct supersymmetry searches at the LHC and measurements of the properties of the Higgs boson, by means of a global fit using the program Fittino. As in previous studies, we find rather poor agreement of the best fit point with the global data. We also investigate the stability of the electro-weak vacuum in the preferred region of parameter space around the best fit point. We find that the vacuum is metastable, with a lifetime significantly longer than the age of the Universe. For the first time in a global fit of supersymmetry, we employ a consistent methodology to evaluate the goodness-of-fit of the cMSSM in a frequentist approach by deriving p-values from large sets of toy experiments. We analyse analytically and quantitatively the impact of the choice of the observable set on the p-value, and in particular its dilution when confronting the model with a large number of barely constraining measurements. Finally, for the preferred sets of observables, we obtain p-values for the cMSSM below 10%, i.e. we exclude the cMSSM as a model at the 90% confidence level.
An unidentified 3.5 keV line from X-ray observations of galaxy clusters has been reported recently. Although still under scrutiny, decaying dark matter could be responsible for this signal. We investigate whether an axino with a mass of 7 keV could explain the line, keeping the discussion as model independent as possible. We point out several obstacles, which were overlooked in the literature, and which make the axino an unlikely candidate. The only viable scenario predicts a light metastable neutralino, with a mass between 0.1 and 10 GeV and a lifetime between $10^{-3}$ and $10^4$ s.
Jalal Abdallah, Henrique Araujo, Alexandre Arbey, Adi Ashkenazi, Alexander Belyaev, Joshua Berger, Celine Boehm, Antonio Boveia, Amelia Brennan, Jim Brooke, Oliver Buchmueller, Matthew Buckley, Giorgio Busoni, Lorenzo Calibbi, Sushil Chauhan, Nadir Daci, Gavin Davies, Isabelle De Bruyn, Paul De Jong, Albert De Roeck, et al (77) Jun 11 2015
hep-ph arXiv:1506.03116v3
This document outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For s-channel, spin-0 and spin-1 mediation is discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented.
Sergey Alekhin, Wolfgang Altmannshofer, Takehiko Asaka, Brian Batell, Fedor Bezrukov, Kyrylo Bondarenko, Alexey Boyarsky, Nathaniel Craig, Ki-Young Choi, Cristóbal Corral, David Curtin, Sacha Davidson, André de Gouvêa, Stefano Dell'Oro, Patrick deNiverville, P. S. Bhupal Dev, Herbi Dreiner, Marco Drewes, Shintaro Eijima, Rouven Essig, et al (65) This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (Search for Hidden Particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, $\tau\to 3\mu$ and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the Standard Model and describe interactions between new particles and four different portals - scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the Standard Model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation
Nov 17 2014
hep-ph arXiv:1411.3731v2
We study the impact of large trilinear R-parity violating couplings on the lightest CP-even Higgs boson mass in supersymmetric models. We use the publicly available computer codes SARAH and SPheno to compute the leading two-loop corrections. We use the effective potential approach. For not too heavy third generation squarks (< 1 TeV) and couplings close to the unitarity bound we find positive corrections up to a few GeV in the Higgs mass.
Philip Bechtle, Klaus Desch, Herbert K. Dreiner, Matthias Hamer, Michael Krämer, Ben O'Leary, Werner Porod, Björn Sarrazin, Tim Stefaniak, Mathias Uhlenbrock, Peter Wienemann Oct 23 2014
hep-ph arXiv:1410.6035v1
Constrained supersymmetric models like the CMSSM might look less attractive nowadays because of fine tuning arguments. They also might look less probable in terms of Bayesian statistics. The question how well the model under study describes the data, however, is answered by frequentist p-values. Thus, for the first time, we calculate a p-value for a supersymmetric model by performing dedicated global toy fits. We combine constraints from low-energy and astrophysical observables, Higgs boson mass and rate measurements as well as the non-observation of new physics in searches for supersymmetry at the LHC. Using the framework Fittino, we perform global fits of the CMSSM to the toy data and find that this model is excluded at more than 95% confidence level.
Jul 10 2014
hep-ph arXiv:1407.2248v2
In order to accommodate the observed Higgs boson mass in the CMSSM, the stops must either be very heavy or the mixing in the stop sector must be very large. Lower stop masses, possibly more accessible at the LHC, still give the correct Higgs mass only if the trilinear stop mixing parameter $|A_t|$ is in the multi-TeV range. Recently it has been shown that such large stop mixing leads to an unstable electroweak vacuum which spontaneously breaks charge or colour. In this work we therefore go beyond the CMSSM and investigate the effects of including baryon number violating operators $\lambda'' \bar{\bf U} \bar{\bf D}\bar{\bf D}$ on the stop and Higgs sectors. We find that for $\lambda'' \simeq {\mathcal{O}}(0.3)$ light stop masses as low as 220 GeV are consistent with the observed Higgs mass as well as flavour constraints while allowing for a stable vacuum. The light stop in this scenario is often the lightest supersymmetric particle. We furthermore discuss the importance of the one-loop corrections involving R-parity violating couplings for a valid prediction of the light stop masses.
The distinguishing feature of the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) axion is that it couples to the electroweak Higgs fields. There is thus an immediate connection between the Peccei-Quinn (PQ) scale and the weak scale. We wish to incorporate the DFSZ axion in a complete supersymmetric model, valid at all scales, and then to implement it in a numerical code connecting the high scale and the low scale physics on a quantitative level. We find that the simplest supersymmetric DFSZ model, as proposed by Rajagopal et al. in 1990, is inconsistent when we consider the minimization of the scalar potential. The problem is that we obtain a negative squared mass for the saxion, the scalar partner of the axion, at the minimum. We then consider the minimal extension in order to get a consistent model for all scales: one has to include an additional explicit sector to spontaneously break the PQ symmetry. In the complete model we can determine the mass of the axino, the fermionic partner of the axion. It is useful to distinguish two cases: (1) the supersymmetry (SUSY) breaking scale is lower than the PQ breaking scale, and (2) the scales are comparable. We find that the axino is very light in (1), while its mass is generically of the order of the other soft SUSY breaking masses in (2). We have implemented SUSY breaking via generic soft breaking terms, and thus make no explicit statement about the form and mediation of SUSY breaking. This complete model can then be incorporated in a numerical code connecting the two scales. We briefly discuss the renormalization group equations and the couplings of the axion to gluons and photons.
In the first three years of running, the LHC has delivered a wealth of new data that is now being analysed. With over 20 fb$^{-1}$ of integrated luminosity, both ATLAS and CMS have performed many searches for new physics that theorists are eager to test their model against. However, tuning the detector simulations, understanding the particular analysis details and interpreting the results can be a tedious task. CheckMATE (Check Models At Terascale Energies) is a program package which accepts simulated event files in many formats for any model. The program then determines whether the model is excluded or not at 95% C.L. by comparing to many recent experimental analyses. Furthermore the program can calculate confidence limits and provide detailed information about signal regions of interest. It is simple to use and the program structure allows for easy extensions to upcoming LHC results in the future. CheckMATE can be found at: http://checkmate.hepforge.org
Theories with dark forces and dark sectors are of interest for dark matter models. In this paper we find the region in parameter space that is constrained by supernova cooling constraints when the models include dark sector particles with masses around 100 MeV or less. We include only interactions with electrons and positrons. The constraint is important for small mixing parameters.
Philip Bechtle, Klaus Desch, Herbert K. Dreiner, Matthias Hamer, Michael Krämer, Ben O'Leary, Werner Porod, Xavier Prudent, Björn Sarrazin, Tim Stefaniak, Mathias Uhlenbrock, Peter Wienemann We present preliminary results from the latest global fit analysis of the constrained minimal supersymmetric standard model (CMSSM) performed within the Fittino framework. The fit includes low-energy and astrophysical observables as well as collider constraints from the non-observation of new physics in supersymmetric searches at the LHC. Furthermore, the Higgs boson mass and signal rate measurements from both the LHC and Tevatron experiments are included via the program HiggsSignals. Although the LHC exclusion limits and the Higgs mass measurements put tight constraints on the viable parameter space, we find an acceptable fit quality once the Higgs signal rates are included.
Sep 09 2013
hep-ph arXiv:1309.1735v1
The recent measurements of $B_s^0 \to \mu\bar{\mu}$ decay candidates at the LHC consistent with the standard model rate, and the improving upper limits for $B_d^0 \to \mu\bar{\mu}$ can strongly constrain beyond the standard model physics. For example, in supersymmetric models with broken R-parity (RpV), they restrict the size of the new couplings. We use the combination of the public software packages SARAH and SPheno to derive new bounds on several combinations of R-parity violating couplings. We improve existing limits for the couplings which open tree-level decay channels and state new limits for combinations which induce loop contributions. This is the first study which performs a full one-loop analysis of these observables in the context of R-parity violation. It turns out that at one-loop despite the strong experimental limits only combinations of R-parity violating couplings are constrained which include third generation fermions. We compare our limits with those obtained via $B\to X_s\gamma$ and discuss the differences.
Aug 02 2013
hep-ph arXiv:1308.0332v1
The Froggatt-Nielsen mechanism provides an elegant explanation for the hierarchies of fermion masses and mixings in terms of a U(1) symmetry. Promoting such a family symmetry to an R-symmetry, we explicitly construct supersymmetric Froggatt-Nielsen models which are gauged, family dependent U(1)_R completions of the Z_4^R symmetry proposed by Lee, Raby, Ratz, Ross, Schieren, Schmidt-Hoberg and Vaudrevange in 2010. Forbidden by Z_4^R, the mu-term is generated around the supersymmetry breaking scale m_3/2 from either the Kahler potential or the superpotential. Neutrinos acquire their mass via the type I seesaw mechanism with three right-handed neutrino superfields. Taking into account the Green-Schwarz anomaly cancellation conditions, we arrive at a total of 3 x 34 distinct phenomenologically viable charge assignments for the standard model fields, most of which feature highly fractional charges.
The white dwarf luminosity function, which provides information about their cooling, has been measured with high precision in the past few years. Simulations that include well known Standard Model physics give a good fit to the data. This leaves little room for new physics and makes these astrophysical objects a good laboratory for testing models beyond the Standard Model. It has already been suggested that white dwarfs might provide some evidence for the existence of axions. In this work we study the constraints that the white dwarf luminosity function puts on physics beyond the Standard Model involving new light particles (fermions or bosons) that can be pair-produced in a white dwarf and then escape to contribute to its cooling. We show, in particular, that we can severely constrain the parameter space of models with dark forces and light hidden sectors (lighter than a few tens of keV). The bounds we find are often more competitive than those from current lab searches and those expected from most future searches.
Mar 15 2013
hep-ph arXiv:1303.3348v1
Effective field theories provide a simple framework for probing possible dark matter (DM) models by reparametrising full interactions into a reduced number of operators with smaller dimensionality in parameter space. In many cases these models have four particle vertices, e.g. qqXX, leading to the pair production of dark matter particles, X, at a hadron collider from initial state quarks, q. In this analysis we show that for many fundamental DM models with s-channel DM couplings to qq-pairs, these effective vertices must also produce quark contact interactions (CI) of the form qqqq. The respective effective couplings are related by the common underlying theory which allows one to translate the upper limits from one coupling to the other. We show that at the LHC, the experimental limits on quark contact interactions give stronger translated limits on the DM coupling than the experimental searches for dark matter pair production.
Dec 21 2012
hep-ph arXiv:1212.5074v3
We present the possibility of calculating the quark flavor changing neutral current decays $B_{s}^0\to \ell \bar \ell$ and $B_{d}^0\to \ell \bar \ell$ for a large variety of supersymmetric models. For this purpose, the complete one-loop calculation has been implemented in a generic form in the Mathematica package SARAH. This information is used by SARAH to generate Fortran source code for SPheno for a numerical evaluation of these processes in a given model. We comment also on the possibility to use this setup for non-supersymmetric models.
Using the example of selected decays driven by R-parity-violating supersymmetric operators, we demonstrate how strong final-state interactions can be controlled quantitatively with high precision, thus allowing for a more accurate extraction of effective parameters from data. In our examples we focus on the lepton-flavor-violating decays tau --> mu pi+ pi-. In R-parity violation these can arise due to the product of two couplings. We find bounds that are an order of magnitude stronger than previous ones.
Nov 30 2012
hep-ph arXiv:1211.6987v1
We study the possible LHC collider signatures in the next-to-minimal supersymmetric Standard Model (NMSSM). The general NMSSM consists of 29 supersymmetric (SUSY) particles which can be mass ordered in $29! \simeq 9 \cdot 10^{30}$ ways. To reduce the number of hierarchies to a more manageable amount we assume a degeneracy of the sfermions of the first two generations with the same quantum numbers. Further assumptions about the neutralino and chargino masses leave 15 unrelated parameters. We check all $15! \approx 10^{12}$ relevant mass orderings for the dominant decay chains and the corresponding collider signatures at the LHC. As preferred signatures, we consider charged leptons, missing transverse momentum, jets, and W, Z or Higgs bosons. We present the results for three different choices of the singlet to Higgs coupling $\lambda$: (a) small: $O(\lambda)< O(Y_{\tau})$, (b) large: $O(\lambda)\simeq O(Y_{top},Y_b, Y_\tau)$ and (c) dominant: $O(\lambda)>O(Y_{top})$. We compare these three scenarios with the MSSM expectations as well as among each other. We also mention a possible mass hierarchy leading to 7 jets plus 1 lepton signatures at the LHC and comment briefly on the consequence of possible R-parity violation.
Nov 22 2012
hep-ph arXiv:1211.4981v1
If Supersymmetry (SUSY) has a compressed spectrum the current limits from the LHC can be drastically reduced. We take possible `worst case' scenarios where combinations of the stop, squark and gluino masses are degenerate with the mass of the lightest SUSY particle. To accurately derive limits in the model, care must be taken when describing QCD radiation and we examine this in detail. Lower mass bounds are then produced by considering all the 7 TeV hadronic SUSY and monojet searches. The evolution of the limits as the mass splitting is varied is also presented.
Nov 13 2012
hep-ph arXiv:1211.2254v1
The WIMP (weakly interacting massive particle) paradigm for dark matter is currently being probed via many different experiments. Direct detection, indirect detection and collider searches are all hoping to catch a glimpse of these elusive particles. Here, we examine the potential of the ILC (International Linear Collider) to shed light on the origin of dark matter. By using an effective field theory approach we are also able to compare the reach of the ILC with that of the other searches. We find that for low mass dark matter (< 10 GeV), the ILC offers a unique opportunity to search for WIMPS beyond any other experiment. In addition, if dark matter happens to only couple to leptons or via a spin dependent interaction, the ILC can give an unrivalled window to these models. We improve on previous ILC studies by constructing a comprehensive list of effective theories that allows us to move beyond the non-relativistic approximation.
If supersymmetry (SUSY) has a compressed spectrum then the current mass limits from the LHC can be drastically reduced. We consider a possible 'worst case' scenario where the gluino and/or squarks are degenerate with the lightest SUSY particle (LSP). The most sensitive searches for these compressed spectra are via the final state LSPs recoiling against initial state radiation (ISR). Therefore it is vital that the ISR is understood and possible uncertainties in the predictions are evaluated. We use both MLM (with Pythia 6) and CKKW- L (with Pythia 8) matching and vary matching scales and parton shower properties to accurately determine the theoretical uncertainties in the kinematic distributions. All current LHC SUSY and monojet analyses are employed and we find the most constraining limits come from the CMS Razor and CMS monojet searches. For a scenario of squarks degenerate with the LSP and decoupled gluinos we find $M_{\tilde{q}}>340$ GeV. For gluinos degenerate with the LSP and decoupled squarks, $M_{\tilde{g}}>500$ GeV. For equal mass squarks and gluinos degenerate with the LSP, $M_{\tilde{q},\tilde{g}}>650$ GeV.
Jun 28 2012
hep-ph arXiv:1206.6305v2
The lack of experimental evidence for supersymmetry motivates R-parity violating realizations of the MSSM. Dropping R-parity, alternative symmetries have to be imposed in order to stabilize the proton. We determine the possible discrete R and non-R symmetries, which allow for renormalizable R-parity violating terms in the superpotential and which, at the effective level, are consistent with the constraints from nucleon decay. Assuming a gauge origin, we require the symmetry to be discrete gauge anomaly-free, allowing also for cancellation via the Green Schwarz mechanism. Furthermore, we demand lepton number violating neutrino mass terms either at the renormalizable or non-renormalizable level. In order to solve the mu problem, the discrete Z_N or Z_N^R symmetries have to forbid any bilinear superpotential operator at tree level. In the case of renormalizable baryon number violation the smallest possible symmetry satisfying all conditions is a unique hexality Z_6^R. In the case of renormalizable lepton number violation the smallest symmetries are two hexalities, one Z_6 and one Z_6^R.
Jun 15 2012
hep-ph arXiv:1206.3096v2
The ATLAS and CMS collaborations have recently reported tantalizing hints of the existence of a 125 GeV Higgs--like particle, whose couplings appear to match well the Standard Model (SM) expectations. In this work, we study implications of this observation for the neutralino sector of supersymmetric models, assuming that the Higgs signal gets confirmed. In general, the Higgs decay into neutralinos can be one of its dominant decay channels. Since a large invisible Higgs decay branching ratio would be in conflict with the data, this possibility is now constrained. In particular, we find that most of the region mu < 170 GeV, M_1 < 70 GeV at tan beta ~ 10 and mu < 120 GeV, M_1 < 70 GeV at tan beta ~ 40 is disfavored.
We present the possible signatures appearing in general realizations of the MSSM based on 14 unrelated mass parameters at the SUSY scale. The parameters of the general MSSM are reduced by assuming a degeneracy of the sfermions of the first two generations with the same quantum numbers. We also assume no mass-splitting between neutral and charged Higgsinos. We do allow for separate soft breaking terms for the third generation sfermons. We consider all possible resulting $14! \approx 9 \cdot10^{10}$ relevant mass orderings and check for the dominant decay cascades and the corresponding collider signatures. In determining the dominant decay modes we assume that mixing between sparticles is sub-dominant. As preferred signatures, we consider charged leptons, missing transverse momentum, jets, and $W, Z$ or Higgs bosons. We include also the cases of bi- and trilinear R-parity violation and show that specific signatures can be used to distinguish the different scenarios.
Apr 27 2012
hep-ph arXiv:1204.5925v2
Many extensions of the leptonic sector of the Minimal Supersymmetric Standard Model (MSSM) are known, most of them leading to observable flavor violating effects. It has been recently shown that the 1-loop contributions to lepton flavor violating three-body decays $l_i \to 3 l_j$ involving the $Z^0$ boson may be dominant, that is, much more important than the usual photonic penguins. Other processes like $\mu$-$e$ conversion in nuclei and flavor violating $\tau$ decays into mesons are also enhanced by the same effect. This is for instance also the case in the MSSM with trilinear R-parity violation. The aim of this work is to derive new bounds on the relevant combinations of R-parity violating couplings and to compare them with previous results in the literature. For heavy supersymmetric spectra the limits are improved by several orders of magnitude. For completeness, also constraints coming from flavor violating $Z^0$-decays and tree-level decay channels $l \to l_i l_j l_k$ are presented for a set of benchmark points.
Philip Bechtle, Torsten Bringmann, Klaus Desch, Herbi Dreiner, Matthias Hamer, Carsten Hensel, Michael Kramer, Nelly Nguyen, Werner Porod, Xavier Prudent, Bjoern Sarrazin, Mathias Uhlenbrock, Peter Wienemann Apr 19 2012
hep-ph arXiv:1204.4199v1
We perform global fits to the parameters of the Constrained Minimal Supersymmetric Standard Model (CMSSM) and to a variant with non-universal Higgs masses (NUHM1). In addition to constraints from low-energy precision observables and the cosmological dark matter density, we take into account the LHC exclusions from searches in jets plus missing transverse energy signatures with about 5\u2009fb$^{-1}$ of integrated luminosity. We also include the most recent upper bound on the branching ratio $B_s\to\mu\mu$ from LHCb. Furthermore, constraints from and implications for direct and indirect dark matter searches are discussed. The best fit of the CMSSM prefers a light Higgs boson just above the experimentally excluded mass. We find that the description of the low-energy observables, $(g-2)_{\mu}$ in particular, and the non-observation of SUSY at the LHC become more and more incompatible within the CMSSM. A potential SM-like Higgs boson with mass around 126 GeV can barely be accommodated. Values for ${\cal B}(B_s\to\mu\mu)$ just around the Standard Model prediction are naturally expected in the best fit region. The most-preferred region is not yet affected by limits on direct WIMP searches, but the next generation of experiments will probe this region. Finally, we discuss implications from fine-tuning for the best fit regions.
We consider the ATLAS and CMS searches for dijet resonances, as well as the ATLAS search for like-sign dimuon pairs at the LHC with 7 TeV center of mass energy. We interpret their exclusions in terms of bounds on the supersymmetric R-parity violating parameter space. For this we focus on resonant slepton production followed by the corresponding decay.
It has been shown that very light or even massless neutralinos are consistent with all current experiments, given non-universal gaugino masses. Furthermore, a very light neutralino is consistent with astrophysical bounds from supernovæ and cosmological bounds on dark matter. Here we study the cosmological constraints on this scenario from Big Bang nucleosynthesis taking gravitinos into account and find that a very light neutralino is even favoured by current observations.
In the CP-violating Minimal Supersymmetric Standard Model, we study the production of a neutralino-chargino pair at the LHC. For their decays into three leptons, we analyze CP asymmetries which are sensitive to the CP phases of the neutralino and chargino sector. We present analytical formulas for the entire production and decay process, and identify the CP-violating contributions in the spin correlation terms. This allows us to define the optimal CP asymmetries. We present a detailed numerical analysis of the cross sections, branching ratios, and the CP observables. For light neutralinos, charginos, and squarks, the asymmetries can reach several 10%. We estimate the discovery potential for the LHC to observe CP violation in the trilepton channel.
Oct 07 2011
hep-ph arXiv:1110.1287v1
If SUSY is discovered at the LHC, the task will immediately turn to determining the model of SUSY breaking. Here, we employ a Mixed Modulus-Anomaly Mediated SUSY Breaking (MMAMSB) model with very similar LHC phenomenology to the more conventionally studied Constrained Minimal SUSY Model (CMSSM) and minimal Anomaly Mediated SUSY Breaking (mAMSB) models. We then study whether the models can be distinguished and measured. If we only fit to the various mass edges and mass end-points from cascade decay chains that are normally studied, a unique determination and measurement of the model is problematic without substantial amounts of LHC data. However, if event rate information is included, we can quickly distinguish and measure the correct SUSY model and exclude alternatives.
S. S. AbdusSalam, B. C. Allanach, H. K. Dreiner, J. Ellis, U. Ellwanger, J. Gunion, S. Heinemeyer, M. Kraemer, M. L. Mangano, K. A. Olive, S. Rogerson, L. Roszkowski, M. Schlaffer, G. Weiglein Sep 20 2011
hep-ph arXiv:1109.3859v3
We define benchmark models for SUSY searches at the LHC, including the CMSSM, NUHM, mGMSB, mAMSB, MM-AMSB and p19MSSM, as well as models with R-parity violation and the NMSSM. Within the parameter spaces of these models, we propose benchmark subspaces, including planes, lines and points along them. The planes may be useful for presenting results of the experimental searches in different SUSY scenarios, while the specific benchmark points may serve for more detailed detector performance tests and comparisons. We also describe algorithms for defining suitable benchmark points along the proposed lines in the parameter spaces, and we define a few benchmark points motivated by recent fits to existing experimental data.
Jun 23 2011
hep-ph arXiv:1106.4338v1
We discuss how the experimental neutrino oscillation data can be realized in the framework of the baryon triality ($B_3$) constrained supersymmetric Standard Model (cSSM). We show how to obtain phenomenologically viable solutions, which are compatible with the recent WMAP observations. We present results for the hierarchical, inverted and degenerate cases which illustrate the possible size and structure of the lepton number violating couplings. We work with a new, as yet unpublished version of SOFTSUSY, where we implemented full one--loop neutrino masses. Finally, we shortly discuss some phenomenological implications at the LHC.
May 27 2011
hep-ph arXiv:1105.5398v1
Both ATLAS and CMS have published results of SUSY searches putting limits on SUSY parameters and masses. A non-discovery of SUSY in the next two years would push these limits further. On the other hand, precision data of low energy measurements and the dark matter relic density favor a light scale of supersymmetry. Therefore we investigate if supersymmetry -- more specifically the highly constraint model mSUGRA -- does at all agree with precision data and LHC exclusions at the same time, and whether the first two years of LHC will be capable of excluding models of supersymmetry. We consider the current non observation of supersymmetry with 35 pb-1 as well as the possible non observation with 1,2 and 7 fb-1 in a global fit using the framework Fittino.
The Tevatron collaborations have searched for associated production of charginos and neutralinos via trilepton final states. No events above the Standard Model prediction were observed. We employ these results to put stringent bounds on R-parity violating models with a right-handed scalar electron as the lightest supersymmetric particle. We work in the framework of lepton number violating minimal supergravity. We find that within these models the complete parameter space consistent with the anomalous magnetic moment of the muon can be excluded at 90% confidence level. We also give prospects for Tevatron trilepton searches assuming an integrated luminosity of 10 fb^-1. We find that Tevatron will be able to test selectron LSP masses up to 170 GeV.
Feb 24 2011
hep-ph arXiv:1102.4693v1
We investigate the implications for supersymmetry from an assumed absence of any signal in the first period of LHC data taking at 7 TeV center-of-mass energy and with 1 to 7 fb^(-1) of integrated luminosity. We consider the zero-lepton plus four jets and missing transverse energy signature, and perform a combined fit of low-energy measurements, the dark matter relic density constraint and potential LHC exclusions within a minimal supergravity model. A non-observation of supersymmetry in the first period of LHC data taking would still allow for an acceptable description of low-energy data and the dark matter relic density in terms of minimal supergravity models, but would exclude squarks and gluinos with masses below 1 TeV.
We investigate the LHC discovery potential of R-parity violating supersymmetric models with a right-handed selectron or smuon as the lightest supersymmetric particle (LSP). These LSPs arise naturally in R-parity violating minimal supergravity models. We classify the hadron collider signatures and perform for the first time within these models a detailed signal over background analysis. We develop an inclusive three-lepton search and give prospects for a discovery at a center-of-mass energy of 7 TeV as well as 14 TeV. There are extensive parameter regions which the LHC can already test with 7 TeV and an integrated luminosity of 1 inverse femtobarn. We also propose a method for the mass reconstruction of the supersymmetric particles within our models at 14 TeV.
Dec 07 2010
hep-ph arXiv:1012.1035v2
The LEP experiments give a lower bound on the neutralino mass of about 46 GeV which, however, relies on a supersymmetric grand unification relation. Dropping this assumption, the experimental lower bound on the neutralino mass vanishes completely. Recent analyses suggest, however, that in the minimal supersymmetric standard model (MSSM), a light neutralino dark matter candidate has a lower bound on its mass of about 7 GeV. In light of this, we investigate the mass sensitivity at the ILC for very light neutralinos. We study slepton pair production, followed by the decay of the sleptons to a lepton and the lightest neutralino. We find that the mass measurement accuracy for a few-GeV neutralino is around 2 GeV, or even less if the relevant slepton is sufficiently light. We thus conclude that the ILC can help verify or falsify the MSSM neutralino cold dark matter model even for very light neutralinos.
Nov 11 2010
hep-ph arXiv:1011.2449v2
We study CP violation in the two-body decay of a scalar tau into a neutralino and a tau, which should be probed at the LHC and ILC. From the normal tau polarization, a CP asymmetry is defined which is sensitive to the CP phases of the trilinear scalar coupling parameter $A_\tau$, the gaugino mass parameter $M_1$, and the higgsino mass parameter $\mu$ in the stau-neutralino sector of the Minimal Supersymmetric Standard Model. Asymmetries of more than 70% are obtained in scenarios with strong stau mixing. As a result, detectable CP asymmetries in stau decays at the LHC are found, motivating further detailed experimental studies for probing the SUSY CP phases.
We investigate the discovery potential of the LHC experiments for R-parity violating supersymmetric models with a stau as the lightest supersymmetric particle (LSP) in the framework of minimal supergravity. We classify the final states according to their phenomenology for different R-parity violating decays of the LSP. We then develop event selection cuts for a specific benchmark scenario with promising signatures for the first beyond the Standard Model discoveries at the LHC. For the first time in this model, we perform a detailed signal over background analysis. We use fast detector simulations to estimate the discovery significance taking the most important Standard Model backgrounds into account. Assuming an integrated luminosity of 1 inverse femtobarn at a center-of-mass energy of 7 TeV, we perform scans in the parameter space around the benchmark scenario we consider. We then study the feasibility to estimate the mass of the stau-LSP. We briefly discuss difficulties, which arise in the identification of hadronic tau decays due to small tau momenta and large particle multiplicities in our scenarios.
May 19 2010
hep-ph arXiv:1005.3309v1
We consider the embedding of the supersymmetric Standard Model with broken R-parity in the minimal supergravity (mSUGRA) model. We restrict ourselves to the case of broken lepton number, the B3 mSUGRA model. We first study in detail how the tree-level neutrino mass depends on the mSUGRA parameters. We find in particular a strong dependence on the trilinear supersymmetry breaking A-parameter, even in the vicinity of the mSUGRA SPS1a point. We then reinvestigate the bounds on the trilinear R-parity violating couplings at the unification scale from the low-energy neutrino masses including dominant one-loop contributions. These bounds were previously shown to be very strict, as low as O(10^-6) for SPS1a. We show that these bounds are significantly weakened when considering the full mSUGRA parameter space. In particular the ratio between the tree-level and 1-loop neutrino masses is reduced such that it may agree with the observed neutrino mass hierarchy. We discuss in detail how and in which parameter regions this effect arises.
Mar 16 2010
hep-ph arXiv:1003.2648v1
We study the determination of supersymmetric parameters at the LHC from a global fit including cross sections and edges of kinematic distributions. For illustration, we focus on a minimal supergravity scenario and discuss how well it can be constrained at the LHC operating at 7 and 14 TeV collision energy, respectively. We find that the inclusion of cross sections greatly improves the accuracy of the SUSY parameter determination, and allows to reliably extract model parameters even in the initial phase of LHC data taking with 7 TeV collision energy and 1/fb integrated luminosity. Moreover, cross section information may be essential to study more general scenarios, such as those with non-universal gaugino masses, and distinguish them from minimal, universal, models.
Jan 27 2010
hep-ph arXiv:1001.4714v1
CP violation in the spin-spin correlations in chargino production and subsequent two-body decay into a tau and a tau-sneutrino is studied at the ILC. From the normal polarisation of the tau, an asymmetry is defined to test the CP-violating phase of the higgsino mass parameter \mu. Asymmetries of more than \pm70% are obtained, also in scenarios with heavy first and second generation sfermions. Bounds on the statistical significances of the CP asymmetries are estimated. As a result, the normal tau polarisation in the chargino decay is one of the most sensitive probes to constrain or measure the phase \phi_\mu at the ILC, motivating further detailed experimental studies.
Oct 09 2009
hep-ph arXiv:0910.1509v2
We consider first an interesting connection between the development of physics and the Boston Red Sox. We then discuss in detail the collider phenomenology, as well as precision electroweak observables of a very light neutralino. We conclude by considering also the astrophysics and cosmology of a very light neutralino. We find that a massless neutralino is consistent with all present data.
Braneshop, and
the US National Science Foundation.
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