RPV SUSY Research Articles

Slepton searches in the trilinear RPV SUSY scenarios at the HL-LHC and HE-LHC

Slepton searches in the trilinear RPV SUSY scenarios at the HL-LHC and HE-LHC

Multi-Jet Event classification with Convolutional neural network at Large Scale

We present an application of Scalable Deep Learning to analyze simulation data of the LHC proton-proton collisions at 13 TeV. We built a Deep Learning model based on the Convolutional Neural Network (CNN) which utilizes detector responses as two-dimensional images reflecting the geometry of the Compact Muon Solenoid (CMS) detector. The model discriminates signal events of the R-parity violating Supersymmetry (RPV SUSY) from the background events with multiple jets due to the inelastic QCD scattering (QCD multi-jets). With the CNN model, we obtained x1.85 efficiency and x1.2 expected significance with respect to the traditional cut-based method. We demonstrated the scalability of the model at a Large Scale with the High-Performance Computing (HPC) resources at the Korea Institute of Science and Technology Information (KISTI) up to 1024 nodes.

Ξb → ${\Xi }_{c} \tau \bar {\nu }_{\tau }$ Decay in New Physics Models

Motivated by several hints of lepton flavor universality (LFU) violation in $b\to c\tau \bar {\nu }_{\tau }$ transitions, we investigate the baryonic semi-leptonic Ξb → ${\Xi }_{c} \tau \bar {\nu }_{\tau }$ decay in Supersymmetry with R-parity violation (RPV SUSY) model and $W^{\prime }$ model. Using the parameter space of these two new physics (NP) models constrained from the up-to-date experimental data, we calculate the branching ratio ${\mathscr{B}}\left ({\Xi }_{b} \to {\Xi }_{c}\tau \bar {\nu }_{\tau }\right )$ and the integrated ratio $R_{{\Xi }_{c}}$ , and also show the effects of these two NP models on some observables, such as the differential branching ratio $\frac {d{\mathscr{B}}}{dq^{2}}({\Xi }_{b} \to {\Xi }_{c}\tau \bar {\nu }_{\tau })$ , the differential ratio $R_{{\Xi }_{c}}\left (q^{2}\right )$ , the lepton-side forward-backward asymmetry $A_{FB}\left (q^{2}\right )$ , the convexity parameter $C_{F}^{\tau }\left (q^{2}\right )$ , the longitudinal polarizations $P_{L}^{\tau }\left (q^{2}\right )$ and $P_{L}^{{\Xi }_{c}}\left (q^{2}\right )$ . We find that: (i) Comparing the SM predictions, ${\mathscr{B}}({\Xi }_{b} \to {\Xi }_{c}\tau \bar {\nu }_{\tau })$ and $R_{{\Xi }_{c}}$ can be enhanced by about 3σ level in the $W^{\prime }$ model, respectively. (ii) Both $\frac {d{\mathscr{B}}}{dq^{2}}({\Xi }_{b} \to {\Xi }_{c}\tau \bar {\nu }_{\tau })$ and $R_{{\Xi }_{c}}\left (q^{2}\right )$ can be enhanced significantly by the $W^{\prime }$ model effects, but for $A_{FB}\left (q^{2}\right )$ , $C_{F}^{\tau }\left (q^{2}\right )$ , $P_{L}^{\tau }\left (q^{2}\right )$ and $P_{L}^{{\Xi }_{c}}\left (q^{2}\right )$ , these two NP models have no effects on these observables, since these two NP models do not generate new operators beyond the SM ones.

Implementation of the CMS-EXO-17-030 analysis in the MadAnalysis 5 framework (production of a pair of resonances decaying each into three jets; 35.9 fb−1)

We present the MadAnalysis 5 implementation and validation of the CMS-EXO-17-030 search. The search targets pair-produced resonances, each of which decaying into three jets. The results are interpreted within an [Formula: see text]-parity violating supersymmetric (RPV SUSY) model, that predicts that pair-produced gluinos decay into three jets. This leads to a six-jet event. For this study, proton–proton collision data which was collected with the CMS detector in 2016 at a center of energy of 13 TeV is used, with a corresponding luminosity of 35.9 fb[Formula: see text]. In the search, the resonance mass is expected to range from 200 GeV to 2000 GeV so that the analysis comprises four signal regions (SRs). To validate the results, we have selected four gluino benchmark masses of 200, 500, 900, and 1600 GeV, each of which being representative of a given signal region (that are denoted SR1, SR2, SR3, and SR4). We have simulated signal events and calculated the signal acceptance within the MadAnalysis 5 framework in each signal region. To validate the recast, our predicted acceptances have been compared with the official values for those benchmark scenarios. An agreement at the level of about 10% has been obtained.

Probing the effects of some new physics models in Bs→ [formula omitted] decay

Recent measurements on the semi-leptonic b→cℓν¯ℓ and b→sℓ+ℓ− decays imply possible hints of Lepton Flavor Universality (LFU) violation and therefore have attracted much attention. In this paper, motivated by these anomalies, we analyze the Bs→Dsτν¯ decay in some New Physics (NP) models, such as the Supersymmetry with R-parity violation (RPV SUSY) model, the W′ model, the vector leptoquark model and the aligned two-Higgs-doublet model (A2HDM). Using the parameter spaces obtained from various flavor constraints, we calculate the branching fraction B(Bs→Dsτν¯) and the ratio RDs of this decay process, and also show the effects of NP models on the differential branching fraction dBdq2, the differential ratio RDs(q2), the lepton-side forward-backward asymmetry AFB(q2), the convexity parameter CFτ(q2) and the τ polarization fraction PLτ(q2). We find that: (i) the effects of NP models are significant for B(Bs→Dsτν¯), but RDs is only sensitive to the effect of A2HDM; (ii) both dBdq2 and RDs(q2) in the four NP models show obvious deviations from the SM predictions; (iii) for AFB(q2), CFτ(q2) and PLτ(q2), only the A2HDM presents obvious effect because the scalar type interactions can be generated in such model.

R -parity violating supersymmetry and the 125 GeV Higgs boson signals

We study the impact of R-parity violating Supersymmetry (RPV SUSY) on the 125 GeV Higgs production and decay modes at the LHC. We assume a heavy SUSY spectrum with multi-TeV squarks and SU(2) scalar singlets as well as the decoupling limit in the SUSY Higgs sector. In this case the lightest CP-even Higgs is SM-like when R-parity is conserved. In contrast, we show that when R-parity violating interactions are added to the SUSY framework, significant deviations may occur in some production and decay channels of the 125 GeV Higgs-like state. Indeed, we assume a single-flavor (mostly third generation) Bilinear RPV (BRPV) interactions, which generate Higgs-sneutrino mixing, lepton-chargino mixing and neutrino-neutralino mixing, and find that notable deviations of ${\cal O}(20-30\%)$ may be expected in the Higgs signal strength observables in some channels, e.g., in $p p \to h \to \mu^+ \mu^-, \tau^+ \tau^-$. Moreover, we find that new and detectable signals associated with BRPV Higgs decays to gauginos, $h\rightarrow\nu_{\tau}\tilde{\chi}_{2}^{0}$ and $h\rightarrow\tau^{\pm}\chi_{2}^{\mp}$, may also arise in this scenario. These decays yield a typical signature of $h \to \tau^\pm \ell^\mp + {{\not\!\! E_T}}$ ($\ell =e,\mu,\tau$) that can be much larger than in the SM, and may also be accompanied by an ${\cal O}(20-30\%)$ enhancement in the di-photon signal $pp \to h \to \gamma \gamma$. We also examine potential interesting signals of Trilinear R-parity violation (TRPV) interactions in the production and decays of the Higgs-sneutrino BRPV mixed state (assuming it is the 125 GeV scalar) and show that, in this case also, large deviations up to ${\cal O}(100\%)$ are expected in e.g., $p p \to h \to \mu^+ \mu^-, \tau^+ \tau^-$, which are sensitive to the BRPV$\times$TRPV coupling product.

Closing the light gluino gap with electron-proton colliders

The future electron-proton collider proposals, LHeC and FCC-he, can deliver $\mathcal{O}$(TeV) center-of-mass energy collisions, higher than most of the proposed lepton accelerators, with $\mathcal{O}$(ab$^{-1}$) luminosity, while maintaining a much cleaner experimental environment as compared to the hadron machines. This unique capability of $e^- p$ colliders can be harnessed in probing BSM scenarios giving final states that look like hadronic noise at $pp$ machines. In the present study, we explore the prospects of detecting such a prompt signal having multiple soft jets at the LHeC. Such a signal can come from the decay of gluino in RPV or Stealth SUSY, where there exists a gap in the current experimental search with $m_{\tilde{g}} \approx 50 - 70$ GeV. We perform a simple analysis to demonstrate that, with simple signal selection cuts, we can close this gap at the LHeC at 95 % confidence level, even in the presence of a reasonable systematic error. More sophisticated signal selection strategies and detailed knowledge of the detector can be used to improve the prospects of signal detection.

Hunting for neutral, long-lived exotica at the LHC using a missing transverse energy signature

Searches at the Large Hadron Collider (LHC) for neutral, long-lived particles have historically relied on the detection of displaced particles produced by their decay $\textit{within}$ the detector volume. In this paper we study the potential of the complementary signature comprising of the missing transverse energy ($E_T^{miss}$) signal, traditionally used to look for dark matter, e.g., the lightest supersymmetric particle (LSP), to extend the LHC coverage to models with long-lived (LL) particles when they decay $\textit{outside}$ the detector. Using CMS and ATLAS analyses at the 8 TeV LHC, we set an upper limit at the 95% confidence level (CL) on the production cross sections for two specific scenarios: (i) a model with a heavy non-standard model Higgs boson decaying to a LL scalar and (ii) an R-parity violating RPV SUSY model with a LL neutralino. We show that this method can significantly extend the LHC sensitivity to neutral, LL particles with arbitrary large lifetimes and that the limits obtained from a $E_T^{miss}$ signal are comparable to those from displaced particle searches for decay distances above a few meters. Results obtained in this study do not not depend on the specific decay channel of the LL particle and therefore are model-independent in this sense. We provide limits for the whole two-dimensional plane in terms of the mass of the LL particle and the mass of the mediator up to masses of 2 TeV including particular benchmarks studied in the original experimental papers. We have made these limits available in the form of a grid which can be used for the interpretation of various other new physics models.

Exploring neutrino physics at LHC via R-parity violating SUSY

R-parity violating supersymmetric models (RPV SUSY) are becoming increasingly more appealing than its R-parity conserving counterpart in view of the hitherto non-observation of SUSY signals at the LHC. In this paper, RPV scenarios where neutrino masses are naturally generated are discussed, namely RPV through bilinear terms (bRPV) and the "μ from ν" supersymmetric standard model (μνSSM). The latter is characterised by a rich Higgs sector that easily accommodates a 125-GeV Higgs boson. The phenomenology of such models at the LHC is reviewed, giving emphasis on final states with displaced objects, and relevant results obtained by LHC experiments are presented. The implications for dark matter for these theoretical proposals is also addressed.

Searches for PromptR-Parity-Violating Supersymmetry at the LHC

Searches for supersymmetry (SUSY) at the LHC frequently assume the conservation ofR-parity in their design, optimization, and interpretation. In the case thatR-parity is not conserved, constraints on SUSY particle masses tend to be weakened with respect toR-parity-conserving models. We review the current status of searches forR-parity-violating (RPV) supersymmetry models at the ATLAS and CMS experiments, limited to 8 TeV search results published or submitted for publication as of the end of March 2015. All forms of renormalisable RPV terms leading to prompt signatures have been considered in the set of analyses under review. Discussing results for searches for promptR-parity-violating SUSY signatures summarizes the main constraints for various RPV models from LHC Run I and also defines the basis for promising signal regions to be optimized for Run II. In addition to identifying highly constrained regions from existing searches, also gaps in the coverage of the parameter space of RPV SUSY are outlined.

Long-lived stop at the LHC with or without R-parity

We consider scenarios of gravitino LSP and DM with stop NLSP both within R-parity conserving and R-parity violating supersymmetry (RPC and RPV SUSY, respectively). We discuss cosmological bounds from Big Bang Nucleosynthesis (BBN) and the gravitino abundance and then concentrate on the signals of long-lived stops at the LHC as displaced vertices or metastable particles. Finally we discuss how to distinguish R-parity conserving and R-parity breaking stop decays if they happen within the detector and how to suppress SM backgrounds.

RPV SUSY effects in $\tau^- \to e^-(\mu^-) K\bar{K}$ decays

In this paper, we investigate [Formula: see text] decays in the framework of the RPV SUSY model. We discuss the tree-level contribution of the sparticles [Formula: see text] and [Formula: see text] to these decay branching ratios. In the two channels, the [Formula: see text]-mediated channel is more sensitive to the parameter product [Formula: see text] than the [Formula: see text]-mediated channel to [Formula: see text]. And the parameter product [Formula: see text] is severely constrained to the order of [Formula: see text] by the experiment data with [Formula: see text], which is one order of magnitude more stringent than before. In the calculation of hadronic matrix elements, the resonant effects are large than those of nonresonant terms. Especially, the resonant contribution of scalar meson f(980) plays a dominate role in [Formula: see text]-mediated channel.

Pulling out all the stops: searching for RPV SUSY with stop-jets

If the lighter stop eigenstate decays directly to two jets via baryonic R-parity violation, it could have escaped existing LHC and Tevatron searches in four-jet events, even for masses as small as 100 GeV. In order to recover sensitivity in the face of increasingly harsh trigger requirements at the LHC, we propose a search for stop pairs in the highly-boosted regime, using the approaches of jet substructure. We demonstrate that the four-jet triggers can be completely bypassed by using inclusive jet-H_T triggers, and that the resulting QCD continuum background can be processed by substructure methods into a featureless spectrum suitable for a data-driven bump-hunt down to 100 GeV. We estimate that the LHC 8 TeV run is sensitive to 100 GeV stops with decays of any flavor at better than 5-sigma level, and could place exclusions up to 300 GeV or higher. Assuming Minimal Flavor Violation and running a b-tagged analysis, exclusion reach may extend up to nearly 400 GeV. Longer-term, the 14 TeV LHC at 300/fb could extend these mass limits by a factor of two, while continuing to improve sensitivity in the 100 GeV region.

Computation of neutrino masses in R-parity violating supersymmetry: SOFTSUSY3.2

The program SOFTSUSY can calculate tree-level neutrino masses in the R-parity violating minimal supersymmetric standard model (MSSM) with real couplings. At tree-level, only one neutrino acquires a mass, in contradiction with neutrino oscillation data. Here, we describe an extension to the SOFTSUSY program which includes one-loop R-parity violating effectsʼ contributions to neutrino masses and mixing. Including the one-loop effects refines the radiative electroweak symmetry breaking calculation, and may result in up to three massive, mixed neutrinos. This paper serves as a manual to the neutrino mass prediction mode of the program, detailing the approximations and conventions used. Program summary Program title: SOFTSUSY Catalogue identifier: ADPM_v3_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADPM_v3_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 93 291 No. of bytes in distributed program, including test data, etc.: 1 288 618 Distribution format: tar.gz Programming language: C++, Fortran Computer: Personal computer Operating system: Tested on Linux 4.x Word size: 32 bits Classification: 11.1, 11.6 Catalogue identifier of previous version: ADPM_v2_0 Journal reference of previous version: Comput. Phys. Comm. 181 (2010) 232 Does the new version supersede the previous version?: Yes Nature of problem: Calculation of neutrino masses and the neutrino mixing matrix at one-loop level in the R-parity violating minimal supersymmetric standard model. The solution to the renormalisation group equations must be consistent with a high or weak-scale boundary condition on supersymmetry breaking parameters and R-parity violating parameters, as well as a weak-scale boundary condition on gauge couplings, Yukawa couplings and the Higgs potential parameters. Solution method: Nested iterative algorithm. Reasons for new version: Added functionality (computation of all three neutrino masses and their mixings) and bug-fixes. Summary of revisions: • Additional error flags for which particle has become tachyonic. • Allowing tanb(MX) boundary condition. New SOFTSUSY Block 7 allows the user to change the number of loops in calculating Higgs mass and electroweak symmetry breaking calculation to be 1 or 2. • mGMSB fine tuning fixed: thanks to Matthias Hamer for pointing out the bug. • RPV SUSY couplings now able to be set at MZ as well as at SUSY breaking scale. • Default output format from softpoint.x is SLHA. • Fixed third-family mixing contribution to gluino mass. MIXING = − 1 now banned. • Small bug-fix in charged Higgs loop calculation, in gaugino contribution. Now respects Z2 (U1R-PQ) flip exactly due to bug-fixes in gluino mass. • Gravitino default mass changed to Planck scale. • Added one-loop RPV loop corrections to neutrino masses allows computation of neutrino oscillation parameters. Restrictions: SOFTSUSY will provide a solution only in the perturbative régime and it assumes that all couplings of the MSSM are real (i.e. CP-conserving). Running time: A second per parameter point.

Bs→K(*)−K(*)+,K(*)−π+,K(*)−ρ+decays in R-parity violating supersymmetry

With the first measurements of the branching ratios and the direct CP asymmetries of B{sub s}{yields}K{sup -}K{sup +}, K{sup -}{pi}{sup +} decays by the CDF collaboration, we constrain the relevant parameter space of the minimal supersymmetric standard model with R-parity violation. Using the constrained R-parity violating couplings, we further examine their possible effects in B{sub s}{yields}K{sup -}*{pi}{sup +}, K{sup (*)-}{rho}{sup +} and K{sup (*){+-}}K{sup (*){+-}} decays. We find that some branching ratios and CP asymmetries are very sensitive to the R-parity violating couplings. The direct longitudinal CP asymmetries of tree-dominated process B{sub s}{yields}K*{sup -}{rho}{sup +} could be enlarged to {approx}70% and the longitudinal polarizations of B{sub s}{yields}K*{sup -}K*{sup +}, K*{sup -}{rho}{sup +} decays could be suppressed very much by the squark exchange couplings. Near future experiments at CERN LHC can test these predictions and shrink/reveal the parameter spaces of RPV SUSY.

Neutrinoless doubleβdecay and effective field theory

We analyze neutrinoless double $\ensuremath{\beta}$ decay $(0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay) mediated by heavy particles from the standpoint of effective field theory. We show how symmetries of the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay quark operators arising in a given particle physics model determine the form of the corresponding effective, hadronic operators. We classify the latter according to their symmetry transformation properties as well as the order at which they appear in a derivative expansion. We apply this framework to several particle physics models, including R-parity violating supersymmetry (RPV SUSY) and the left-right symmetric model (LRSM) with mixing and a right-handed Majorana neutrino. We show that, in general, the pion exchange contributions to $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay dominate over the short-range four-nucleon operators. This confirms previously published RPV SUSY results and allows us to derive new constraints on the masses in the LRSM. In particular, we show how a nonzero mixing angle $\ensuremath{\zeta}$ in the left-right symmetry model produces a new potentially dominant contribution to $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay that substantially modifies previous limits on the masses of the right-handed neutrino and boson stemming from constraints from $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay and vacuum stability requirements.