51428350
Soft RPV through the baryon portal
A bstractSupersymmetric (SUSY) models with R-parity generically predict sparticle decays with invisible neutralinos, which yield distinctive missing energy events at colliders. Since most LHC searches are designed with this expectation, the putative bounds on sparticle masses become considerably weaker if R-parity is violated so that squarks and gluinos decay to jets with large QCD backgrounds. Here we introduce a scenario in which baryonic R-parity violation (RPV) arises effectively from soft SUSY breaking interactions, but leptonic RPV remains accidentally forbidden to evade constraints from proton decay and FCNCs. The model features a global R-symmetry that initially forbids RPV interactions, a hidden R-breaking sector, and a heavy mediator that communicates this breaking to the visible sector. After R-symmetry breaking, the mediator is integrated out and an effective RPV A-term arises at tree level; RPV couplings between quarks and squarks arise only at loop level and receive additional suppression. Although this mediator must be heavy compared to soft masses, the model introduces no new hierarchy since viable RPV can arise when the mediator mass is near the SUSY breaking scale. In generic regions of parameter space, a light thermally-produced gravitino is stable and can be a viable dark matter candidate.
119264520
LHC coverage of RPV MSSM with light stops
A bstractWe examine the sensitivity of recent LHC searches to signatures of supersymmetry with R-parity violation (RPV). Motivated by naturalness of the Higgs potential, which would favor light third-generation squarks, and the stringent LHC bounds on spectra in which the gluino or first and second generation squarks are light, we focus on scenarios dominated by the pair production of light stops. We consider the various possible direct and cascade decays of the stop that involve the trilinear RPV operators. We find that in many cases, the existing searches exclude stops in the natural mass range and beyond. However, typically there is little or no sensitivity to cases dominated by UDD operators or LQD operators involving taus. We propose several ideas for searches which could address the existing gaps in experimental coverage of these signals.
118457630
SUSY stops at a bump
A bstractWe discuss collider signatures of the “natural supersymmetry” scenario with baryon-number violating R-parity violation. We argue that this is one of the few remaining viable incarnations of weak scale supersymmetry consistent with full electroweak naturalness. We show that this intriguing and challenging scenario contains distinctive LHC signals, resonances of hard jets in conjunction with relatively soft leptons and missing energy, which are easily overlooked by existing LHC searches. We propose novel strategies for distinguishing these signals above background, and estimate their potential reach at the 8 TeV LHC. We show that other multi-lepton signals of this scenario can be seen by currently existing searches with increased statistics, but these opportunities are more spectrum-dependent.
10018306
Minimal flavor violation, seesaw mechanism, and R parity
The minimal flavor violation hypothesis (MFV) is extended to the R-parity violating minimal supersymmetric standard model, supplemented with a simple seesaw mechanism. The requirement of MFV is shown to suppress lepton- and baryon-number violating couplings sufficiently to pass all experimental bounds, in particular, those for proton decay, and is thus a viable alternative to R parity. The phenomenological consequences for flavor-changing neutral currents, lepton flavor violation, and colliders are briefly discussed. Typically, MFV predicts sizable baryon-number violation in some characteristic channels, like single stop resonant production.
119196390
MFV SUSY: A Natural Theory for R-Parity Violation
We present an alternative approach to low-energy supersymmetry. Instead of imposing R-parity we apply the minimal avor violation (MFV) hypothesis to the Rparity violating MSSM. In this framework, which we call MFV SUSY, squarks can be light and the proton long lived without producing missing energy signals at the LHC. Our approach diers from that of Nikolidakis and Smith in that we impose holomorphy on the MFV spurions. The resulting model is highly constrained and R-parity emerges as an accidental approximate symmetry of the low-energy Lagrangian. The size of the small R-parity violating terms is determined by the avor parameters, and in the absence of neutrino masses there is only one renormalizable R-parity violating interaction: the baryon-number violating u d d superpotential term. Low energy observables (proton decay, dinucleon decay and n n oscillation) pose only mild constraints on the parameter space. LHC phenomenology will depend on whether the LSP is a squark, neutralino, chargino or slepton. If the LSP is a squark it will have prompt decays, explaining the non-observation of events with missing transverse energy at the LHC.
119221926
Gauging the way to MFV
A bstractWe present a UV complete model with a gauged flavor symmetry which approximately realizes holomorphic Minimal Flavor Violation (MFV) in R-parity violating (RPV) supersymmetry. Previous work has shown that imposing MFV as an ansatz easily evades direct constraints and has interesting collider phenomenology. The model in this work spontaneously breaks the flavor symmetry and features the minimum “exotic” field content needed to cancel anomalies. The flavor gauge bosons exhibit an inverted hierarchy so that those associated with the third generation are the lightest. This allows low energy flavor constraints to be easily satisfied and leaves open the possibility of flavor gauge bosons accessible at the LHC. The usual MSSM RPV operators are all forbidden by the new gauge symmetry, but the model allows a purely exotic operator which violates both R-parity and baryon number. Since the exotic fields mix with MSSM-like right handed quarks, diagonalizing the full mass matrix after flavor-breaking transforms this operator into the trilinear baryon number violating operator $ \overline{U}\overline{D}\overline{D} $ with flavor coefficients all suppressed by three powers of Yukawa couplings. There is a limit where this model realizes exact MFV; we compute corrections away from MFV, show that they are under theoretical control, and find that the model is viable in large regions of parameter space.
119293724
New patterns of natural R-parity violation with supersymmetric gauged flavor
A bstractWe point out that supersymmetric gauged flavor models provide a realization of R-parity violation (RPV) that is natural in the sense that it does not lead to catastrophic proton decay for natural values of parameters in the theory. Within specific realizations of the idea, the relative strengths of the ΔB = 1 ucdcdc type RPV operators can be predicted. In particular, we present examples of gauged flavor models where RPV couplings depend on quark masses as $ {{\left( {{{{{m_{{{u_i}}}}{m_{{{d_j}}}}{m_{{{d_k}}}}}} \left/ {{m_t^3}} \right.}} \right)}^n} $ where n = 1 or n = 1/2. Some phenomenological implications of these models are discussed.
119186971
A collective breaking of R-parity
A bstractSupersymmetric theories with an R-parity generally yield a striking missing energy signature, with cascade decays concluding in a neutralino that escapes the detector. In theories where R-parity is broken the missing energy is replaced with additional jets or leptons, often making traditional search strategies ineffective. Such R-parity violation is very constrained, however, by resulting B and L violating signals. The R-parity violating couplings must be so small that there is tension for LSP decays to occur within the detector, unless couplings to different flavors are strongly hierarchical. In theories with additional matter fields, R-parity can be broken collectively, such that R-parity is not broken by any single coupling, but only by an ensemble of couplings. Cascade decays can proceed normally, with each step only sensitive to one or two couplings at a time, but B and L violation requires the full set, yielding a highly suppressed constraint. s-channel production of new scalar states, typically small for standard RPV, can be large when RPV is broken collectively. While missing energy is absent, making these models difficult to discover by traditional SUSY searches, they produce complicated many object resonances (MORes), with many different possible numbers of jets and leptons. We outline a simple model and discuss its discoverability at the LHC.
119265557
Breaking local baryon and lepton number at the TeV scale
Simple models are proposed where the baryon and lepton number are gauged and spontaneously broken near the weak scale. The models use a fourth generation that is vector-like with respect to the strong, weak and electromagnetic interactions to cancel anomalies. One does not need large Yukawa couplings to be consistent with the experimental limits on fourth generation quark masses and hence the models are free of coupling constants with Landau poles near the weak scale. We discuss the main features of simple non-supersymmetric and supersymmetric models. In these models the light neutrino masses are generated through the seesaw mechanism and proton decay is forbidden even though B and L are broken near the weak scale. For some values of the parameters in these models baryon and/or lepton number violation can be observed at the Large Hadron Collider.
118652092
Supersymmetry with a sister Higgs boson
Within the context of supersymmetric theories, explaining a 125 GeV Higgs motivates a consideration of a broader range of models. We consider a simple addition to the MSSM of a \Sister Higgs" ( d), a Higgs eld that participates in electroweak symmetry breaking but does not give any direct masses to Standard Model matter elds. While a relatively minor addition, the phe
119267303
Natural supersymmetry’s last hope: R-parity violation via UDD operators
Here we give a broad overview of the more natural spectra allowed by the LHC when $UDD$ $R$-parity violation is allowed. Because $R$-parity violation removes the missing energy signals in colliders, the experimental constraints on the gluino, stops, sbottoms, and Higgsinos are relatively mild. We also show that $UDD$ $R$-parity violation and lepton number conservation can be made consistent with grand unification. This feat is achieved through the product unification, $SU(5)\ifmmode\times\else\texttimes\fi{}U(3)$. In this model, mixing of the standard model quarks with additional quarklike particles charged under the $U(3)$ generate a $UDD$ $R$-parity violating operator. Furthermore, these models are also capable of generating a ``natural'' spectra. The emergence of these more natural low-scale spectra relies heavily on the fact that the gaugino masses are nonuniversal, a natural consequence of product unification.
122823298
R parity violating minimal supergravity model
We present the minimal supersymmetric standard model with general broken R-parity, focusing on minimal supergravity (mSUGRA). We discuss the origins of lepton number violation in supersymmetry. We have computed the full set of coupled one-loop renormalization group equations for the gauge couplings, the superpotential parameters and for all the soft supersymmetry breaking parameters. We provide analytic formule for the scalar potential minimization conditions which may be iterated to arbitrary precision. We compute the low-energy spectrum of the superparticles and the neutrinos as a function of the small set of parameters at the unification scale in the general basis. Specializing to mSUGRA, we use the neutrino masses to set new bounds on the R-parity violating couplings. These bounds are up-to five orders of magnitude stricter than the previously existing ones. In addition, new bounds on the R-parity violating couplings are also derived demanding a non-tachyonic sneutrino spectrum. We investigate the nature of the lightest supersymmetric particle and find extensive regions in parameter space, where it is not the neutralino. This leads to a novel set of supersymmetric signatures, which we classify.
117455725
Gravitino dark matter and cosmological constraints
Gravitino is a good candidate for dark matter when it is the lightest supersymmetric particle and R‐parity is conserved. Here I give the possibility of Gravitino as Dark Matter and the implications in the Constrained Minimal Supersymmetric Standard Model (CMSSM) with the recently improved constraints especially from cosmological considerations. After that the cosmological importance of Gravitino dark matter to solve the cosmic Lithium problems and to probe the reheating temperature after inflation is discussed.
55395343
Baryonic violation of R parity from anomalous U ( 1 ) H
Supersymmetric scenarios with $R$-parity conservation are becoming very constrained due to the lack of missing energy signals associated to heavy neutral particles, thus motivating scenarios with $R$-parity violation. In view of this, we consider a supersymmetric model with $R$-parity violation and extended by an anomalous horizontal $U(1{)}_{H}$ symmetry. A self-consistent framework with baryon-number violation is achieved along with a proper suppression for lepton-number violating dimension-five operators, so that the proton can be sufficiently stable. With the introduction of right-handed neutrinos, both Dirac and Majorana masses can be accommodated within this model. The implications for collider physics are discussed.
10493446
Bounds on R-parity violating couplings at the weak scale and at the GUT scale
We analyse bounds on trilinear R-parity violating couplings at the unification scale by renormalising the weak scale bounds. We derive unification scale upper bounds upon the couplings which are broadly independent of the fermion mass texture assumed. The R-parity violating couplings are factors of two to five more severely bounded at the unification scale than at the electroweak scale. In the presence of quark mixing, a few of the bounds are orders of magnitude stronger than their weak scale counterparts due to new R-parity violating operators being induced in the renormalisation between high and low scales. These induced bounds are fermion mass texture dependent. New bounds upon the weak scale couplings are obtained by the requirement of perturbativity between the weak and unification scales. A comprehensive set of the latest limits is included.
119037734
Effective R-parity violation from supersymmetry breaking
We present a scenario in which Yukawa-like R-parity violating (RPV) couplings are naturally suppressed. In our framework, RPV is assumed to originate from the SUSY breaking mechanism and then transmitted into the SUSY Lagrangian only through soft SUSY breaking operators in the scalar potential. The RPV Yukawa-like operators of the superpotential, conventionally parametrized by the couplings \lambda, \lambda' and \lambda'', are then generated through loops containing the SUSY scalars, the gauginos and the soft RPV interactions and are, therefore, manifest as effective operators with a typical strength of order 10^{-3}.
14510985
R-parity violation effects through soft supersymmetry-breaking terms and the renormalization group.
We present full renormalization group equations for the MSSM with {ital R}-parity violation, including all soft supersymmetry-breaking terms. The inclusion of dimensionless {ital R}-parity-violating couplings can generate many possible low energy effects through the generation of off-diagonal soft masses violating lepton and quark flavor, and through the generation of lepton{endash}Higgs-superfield mixing. We discuss the relation between the weak and unification scale {ital R}-parity violation and study the effects on neutrino mass generation and {mu}{r_arrow}{ital e}{gamma}. {copyright} {ital 1996 The American Physical Society.}
12637636
R-parity violation and general soft supersymmetry breaking
We consider the most general class possible of soft supersymmetry breaking terms that can be added to the MSSM, with and without R-parity violation, consistent with the sole requirement that no quadratic divergences are induced. We renormalise the resulting theory through one loop and give an example of how a previously ignored term might affect the sparticle spectrum.
124698732
R-Parity-violating supersymmetry
Theoretical and phenomenological implications of R-parity violation in supersymmetric theories are discussed in the context of particle physics and cosmology. Fundamental aspects include the relation with continuous and discrete symmetries and the various allowed patterns of R-parity breaking. Recent developments on the generation of neutrino masses and mixings within different scenarios of R-parity violation are discussed. The possible contribution of R-parity-violating Yukawa couplings in processes involving virtual supersymmetric particles and the resulting constraints are reviewed. Finally, direct production of supersymmetric particles and their decays in the presence of R-parity-violating couplings is discussed together with a survey of existing constraints from collider experiments.
119229429
Two-loop R-parity violating Renormalisation Group Equations for non-standard soft supersymmetry breaking in the context of the MSSM
We present the two-loop $\beta$-functions for non-standard soft supersymmetry-breaking couplings including non-standard R-parity violating soft terms in the Minimal Supersymmetric Standard Model
118919354
R-symmetry breaking versus supersymmetry breaking
Abstract We point out a connection between R-symmetry and supersymmetry breaking. We show that the existence of an R-symmetry is a necessary condition for supersymmetry breaking and a spontaneously broken R-symmetry is a sufficient condition provided two conditions are satisfied. These conditions are: genericity, i.e. the effective lagrangian is a generic lagrangian consistent with the symmetries of the theory (no fine tuning), and calculability, i.e. the low-energy theory can be described by a supersymmetric Wess-Zumino effective lagrangian without gauge fields. All known models of dynamical supersymmetry breaking possess such a spontaneously broken R-symmetry and therefore contain a potentially troublesome axion. However, we use the fact that genericity is not a feature of supersymmetric theories, even when non-perturbative renormalization is included, to show that the R-symmetry can in many cases be explicitly broken without restoring supersymmetry and so the axion can be given an acceptably large mass.
118574892
“L = R” — U(1)R as the origin of leptonic ‘RPV’
A bstractA classification of phenomenologically interesting supersymmetric extensions of the Standard-Model with a U(1)R symmetry is presented. Some of these are consistent with subsets of leptonic or baryonic “R-parity violating” (RPV) operators, thereby providing a natural motivation for them. We then focus on a particular class of models in which the U(1)R symmetry coincides with lepton number when restricted to the SM sector. In this case, the extension of lepton number to the superpartners is “non-standard”, implying, in particular, the existence of the leptonic RPV operators LLEc and LQDc, and a vacuum structure where one of the left-handed sneutrinos acquires a significant vacuum-expectation-value, while not being constrained by neutrino mass bounds. The model can be naturally consistent with bounds from electroweak precision measurements and flavor-changing processes. It can also easily accommodate the recently measured Higgs mass due to the existence of a scalar triplet that couples to the Higgs with an order one coupling, with only moderate fine-tuning. The phenomenology is rather rich and distinctive, with features such as heavy-but-natural Dirac gauginos, relaxed bounds on squarks, resonant slepton/sneutrino production, lepto-quark signals, as well as an interesting connection to neutrino physics arising from R-breaking. The broad qualitative features are discussed in this paper, with a more detailed phenomenological study carried out in a companion paper [1].
7628980
Dirac gaugino masses and supersoft supersymmetry breaking
We introduce a new supersymmetric extension of the standard model in which the gauge sector contains complete N = 2 supersymmetry multiplets. Supersymmetry breaking from the D-term vev of a hidden sector U(1) gauge field leads to Dirac soft supersymmetry breaking gaugino masses, and a new type of soft scalar trilinear couplings. The resulting squark and slepton masses are finite, calculable, positive and flavor universal. The Higgs soft mass squared is negative. The phenomenology of these theories differs significantly from the MSSM. We discuss a variety of possible origins for the soft operators and new fields, including models in both four and higher dimensions.
119178658
Flavor in Supersymmetry with an Extended R-symmetry
We propose a new solution to the supersymmetric flavor problem without flavor-blind mediation. Our proposal is to enforce a continuous or a suitably large discrete R-symmetry on weak scale supersymmetry, so that Majorana gaugino masses, trilinear A terms, and the μ term are forbidden. We find that replacing the minimal supersymmetric standard model with an R-symmetric supersymmetric model allows order one flavor-violating soft masses, even for squarks of order a few hundred GeV. The minimal R-symmetric supersymmetric model contains Dirac gaugino masses and R-symmetric Higgsino masses with no left-right mixing in the squark or slepton sector. Dirac gaugino masses of order a few TeV with vanishing A terms solve most flavor problems, while the R-symmetric Higgs sector becomes important at large tanβ. ∈ K can be accommodated if CP is preserved in the SUSY breaking sector, or if there is a moderate flavor degeneracy, which can arise naturally. ∈'/∈, as well as neutron and electron electric dipole moments, are easily within experimental bounds. The most striking phenomenological distinction of this model is the order one flavor violation in the squark and slepton sector, while the Dirac gaugino masses tend to be significantly heavier than the corresponding squark and slepton masses.
119674376
Astrophysical methods to constrain axions and other novel particle phenomena
Various extensions of the standard model of elementary particle interactions predict the existence of new particles such as axions, or “exotic” properties of known particles such as neutrino magnetic moments. If these particles are sufficiently light, they emerge in large numbers from the hot and dense interior of stellar bodies. For appropriate ranges of particle parameters, this “invisible” energy loss would lead to observable changes in the evolution of stars. We review the theoretical methods as well as the observational data that have been employed in order to use stars as “particle physics laboratories” in the spirit of this argument. The resulting constraints on the properties of axions are systematically explored, and the application of the general methods to other cases are mentioned and referenced. Cosmological axion bounds and experiments involving galactic or solar axions are briefly reviewed.
18919900
The R axion from dynamical supersymmetry breaking
Abstract All generic, calculable models of dynamical supersymmetry breaking have a spontaneously broken R -symmetry and therefore contain an R -axion. We showthat the axion is massive in any model in which the cosmological constant is fine-tuned to zero through an explicit R -symmetry-breaking c constant. In visible-sector models, the axion mass is in the 100 MeV range and thus evades astrophysical bounds. In nonrenormalizable hidden-sector models, the mass is of order of the weak scale and can have dangerous cosmological consequences similar to those already present from other fields. In renormalizable hidden-sector models, the axion mass is generally quite large, of order 10 7 GeV. Typically, these axions are cosmologically safe. However, if the dominant decay mode is to gravitinos, the potentially large gravitino abundance that arises from axion decay after inflation might affect the successful predictions of big-bang nucleosynthesis. We show that the upper bound on the reheat temperature after standard inflation can be competitive with or stronger than bounds from thermal gravitino production, depending on the model and the gravitino mass.
118389137
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.
119210577
Search for pair production of massive particles decaying into three quarks with the ATLAS detector in $ \sqrt{s}=7\;\mathrm{TeV} $pp collisions at the LHC
A bstractA search is conducted for hadronic three-body decays of a new massive coloured particle in $ \sqrt{s}=7\;\mathrm{TeV} $pp collisions at the LHC using an integrated luminosity of 4.6 fb−1 collected by the ATLAS detector. Supersymmetric gluino pair production in the context of a model with R-parity violation is used as a benchmark scenario. The analysis is divided into two search channels, each optimised separately for their sensitivity to high-mass and low-mass gluino production. The first search channel uses a stringent selection on the transverse momentum of the six leading jets and is performed as a counting experiment. The second search channel focuses on low-mass gluinos produced with a large boost. Large-radius jets are selected and the invariant mass of each of the two leading jets is used as a discriminant between the signal and the background. The results are found to be consistent with Standard Model expectations and limits are set on the allowed gluino mass.
119105607
Boosted Multijet Resonances and New Color-Flow Variables
We use modern jet-substructure techniques to propose LHC searches for multijet-resonance signals without leptons or missing energy. We focus on three-jet resonances produced by $R$-parity-violating decays of boosted gluinos, showing that shape analyses searching for a mass peak can probe such gluinos up to masses of $\ensuremath{\sim}750\text{ }\text{ }\mathrm{GeV}$ (650 GeV) with $20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ ($5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$) at the LHC at 8 TeV. This complements existing search strategies, which also include counting methods that are inherently more prone to systematic uncertainties. Since $R$-parity-violating gluinos lighter than all squarks hadronize before decaying, we introduce new color-flow variables, ``radial pull'' and ``axis contraction,'' which are sensitive to the color structure of the $R$-hadron's decay. The former measures the inward pull of subjets in a fat jet, while the latter quantifies the inward drift of the $N$-subjettiness axes when changing the distance measure. We show that they can dramatically improve the discrimination of a boosted gluino signal vs QCD, $t\overline{t}$, and combinatoric background for ${m}_{\stackrel{\texttildelow{}}{g}}\ensuremath{\sim}{m}_{t}$. Cuts on axis contraction also noticeably improve the resonance shape for heavy gluinos with ${m}_{\stackrel{\texttildelow{}}{g}}\ensuremath{\gtrsim}500\text{ }\text{ }\mathrm{GeV}$. With minor adaptations, these variables could find application in substructure searches for particles in different color representations or with other decay topologies. We also compare how several different Monte Carlo generators model the high-multiplicity QCD background. This provides evidence that the discriminating power of our color-flow observables are robust, and provides useful guidance for future substructure studies.
119180406
Can R-parity violation hide vanilla supersymmetry at the LHC?
A bstractCurrent experimental constraints on a large parameter space in supersymmetric models rely on the large missing energy signature. This is usually provided by the lightest neutralino which stability is ensured by R-parity. However, if R-parity is violated, the lightest neutralino decays into the standard model particles and the missing energy cut is not efficient anymore. In particular, the U DD type R-parity violation induces the neutralino decay to three quarks which potentially leads to the most difficult signal to be searched at hadron colliders. In this paper, we study the constraints on R-parity violating supersymmetric models using a same-sign dilepton and a multijet signatures. We show that the gluino and squarks lighter than TeV are already excluded in the constrained minimal supersymmetric standard model with the R-parity violation if their masses are approximately equal. We also analyze constraints in a simplified model with the R-parity violation. We compare how the R-parity violation changes some of the observables typically used to distinguish a supersymmetric signal from standard model backgrounds.
119228622
Boosting searches for natural supersymmetry with R -parity violation via gluino cascades
In the presence of even minuscule baryonic R-parity violation, the stop can be the lightest superpartner and evade LHC searches because it decays into two jets. In order to cover this interesting possibility, we here consider new searches for RPV stops produced in gluino cascades. While typical searches for gluinos decaying to stops rely on same-sign dileptons, the RPV cascades usually have fewer hard leptons, less excess missing energy, and more jets than R-parity conserving cascades. If the gluino is a Dirac fermion, same-sign dilepton signals are also often highly depleted. We therefore explore search strategies that use single-lepton channels, and combat backgrounds using HT, jet counting, and more detailed multijet kinematics or jet substructure. We demonstrate that the stop mass peaks can be fully reconstructed over a broad range of spectra, even given the very high jet multiplicities. This would not only serve as a "double-discovery" opportunity, but would also be a spectacular confirmation that the elusive top-partner has been hiding in multijets.
119114682
The same-sign dilepton signature of RPV/MFV SUSY
A bstractThe lack of observation of superpartners at the Large Hadron Collider so far has led to a renewed interest in supersymmetric models with R-parity violation (RPV). In particular, imposing the Minimal Flavor Violation (MFV) hypothesis on a general RPV model leads to a realistic and predictive framework. Naturalness suggests that stops and gluinos should appear at or below the TeV mass scale. We consider a simplified model with these two particles and MFV couplings. The model predicts a significant rate of events with same-sign dileptons and b-jets. We re-analyze a recent CMS search in this channel and show that the current lower bound on the gluino mass is about 800 GeV at 95% confidence level, with only a weak dependence on the stop mass as long as the gluino can decay to an on-shell top-stop pair. We also discuss how this search can be further optimized for the RPV/MFV scenario, using the fact that MFV stop decays often result in jets with large invariant mass. With the proposed improvements, we estimate that gluino masses of up to about 1.4 TeV can be probed at the 14 TeV LHC with a 100 fb−1 data set.
118594449
Exploring supersymmetric model with very light gravitino at the LHC
A bstractThe low-scale gauge mediation scenario of supersymmetry breaking predicts very light gravitino, which makes the next lightest supersymmetric particle (NLSP) quasi stable. We study the LHC phenomenology of the case that the NLSP is the stau. When the mass of the gravitino is of the order of 10 eV, the decay length of stau is about 0.1-1 mm, so that it decays before reaching the first layer of the inner silicon detector. We show, however, that, with utilizing the impact parameter of τ -jets from the stau decay, it is possible to determine the mass spectrum of sparticles precisely. It is also possible to estimate the lifetime of the stau by observing distribution of the impact parameter.
119114779
Displaced Supersymmetry
A bstractThe apparent absence of light superpartners at the LHC strongly constrains the viability of the MSSM as a solution to the hierarchy problem. These constraints can be significantly alleviated by R-parity violation (RPV). Bilinear R-parity violation, with the single operator LHu, does not require any special flavor structure and can be naturally embedded in a GUT while avoiding constraints from proton decay (unlike baryon-number-violating RPV). The LSP in this scenario can be naturally long-lived, giving rise to displaced vertices. Many collider searches, particularly those selecting b-jets or leptons, are insensitive to events with such detector-scale displaced decays owing to cuts on track quality and impact parameter. We demonstrate that for decay lengths in the window ∼1–103 mm, constraints on superpartner masses can be as low as ∼450 GeV for squarks and ∼40 GeV for LSPs. In some parts of parameter space light LSPs can dominate the Higgs decay width, hiding the Higgs from existing searches. This framework motivates collider searches for detector-scale displaced vertices. LHCb may be ideally suited to trigger on such events, while ATLAS and CMS may need to trigger on missing energy or multijet signatures.