R-parity Violation Research Articles

Search for pair production of squarks or gluinos decaying via sleptons or weak bosons in final states with two same-sign or three leptons with the ATLAS detector

A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb−1 of proton-proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of the WZ + jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models considering gluino (squark) pair production, gluino (squark) masses up to 2.2 (1.7) TeV are excluded at 95% confidence level.

Search for electroweakinos in R-parity violating SUSY with long-lived particles at HL-LHC

We investigate the R-parity violating (RPV) supersymmetric (SUSY) model at the High-Luminosity Large Hadron Collider (HL-LHC) in the context of compact muon solenoid (CMS) experiment assuming a total integrated luminosity of L\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{L} $$\\end{document} = 3000 fb−1 at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 14 TeV. We focus on the pair production of electroweakinos, specifically, χ20\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_2^0 $$\\end{document} and χ1±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_1^{\\pm } $$\\end{document} in wino and higgsino states in a particular scenario where χ20\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_2^0 $$\\end{document} and χ1±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_1^{\\pm } $$\\end{document} decay into a Higgs boson and W boson, respectively, along the long-lived lightest supersymmetric particle (LSP), χ10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_1^0 $$\\end{document}, which decays to three quarks via λ′′ RPV couplings leading to the prompt as well as displaced signatures in the final state. To select events at the level-1 (L1) trigger system, we employ dedicated and standard triggers followed by an offline analysis integrating information from the tracker, electromagnetic calorimeter (ECAL) and minimum ionising particle (MIP) timing detector (MTD). We observe that wino-like χ20/χ1±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_2^0/{\\chi}_1^{\\pm } $$\\end{document} with a mass of 1900 GeV and χ10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_1^0 $$\\end{document} with a mass greater than 800 GeV can be probed across a decay length ranging from 1 cm to 200 cm. In the case of higgsino-like pair production of χ20/χ1±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_2^0/{\\chi}_1^{\\pm } $$\\end{document}, we can probe χ20/χ1±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_2^0/{\\chi}_1^{\\pm } $$\\end{document} with a mass of 1600 GeV, and χ10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\chi}_1^0 $$\\end{document} with a mass greater than 700 GeV, across a decay length range of 1 cm to 200 cm.

Search for Evidence of Baryogenesis and Dark Matter in B^{+}→ψ_{D}+p Decays at BABAR.

A new dark sector antibaryon, denoted ψ_{D}, could be produced in decays of B mesons. This Letter presents a search for B^{+}→ψ_{D}+p (and the charge conjugate) decays in e^{+}e^{-} annihilations at 10.58GeV, using data collected in the BABAR experiment. Data corresponding to an integrated luminosity of 398 fb^{-1} are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from 10^{-7}-10^{-5} are obtained at 90% confidence level for masses of 1.0<m_{ψ_{D}}<4.3 GeV/c^{2}. The result is also reinterpreted to provide the first limits on a supersymmetric model with R-parity violation and a light neutralino.

Recasting bounds on long-lived heavy neutral leptons in terms of a light supersymmetric R-parity violating neutralino

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.

Type III seesaw with R-parity violation in light of m (CDF)

Motivated by the recently reported measurement of the $W$ boson mass $M_W = 80.4335 \pm 0.0094$ GeV by the CDF collaboration, we propose a type III seesaw extension of the minimal supersymmetric standard model (MSSM) which also includes an R-parity violating term. Without taking potential SUSY radiative corrections into account, we show that the CDF measurement of $M_W$ and the LEP measurement of the $\rho$ parameter can be simultaneously accommodated at the $2 \sigma$ level. A long-lived gravitino in a few GeV mass range is a unique viable dark matter candidate in this framework.

Probing R-parity violation in B-meson decays to a baryon and a light neutralino

We propose a search for B meson decays to a baryon plus missing energy at the Belle II experiment to probe supersymmetry with a GeV-scale lightest neutralino {overset{sim }{chi}}_1^0 and R-parity violation (RPV). We perform analytic computations of the signal branching fractions in the framework of effective field theory, with a single nonzero RPV operator {lambda}_{ij3}^{prime prime }{overline{U}}_i^c{overline{D}}_j^c{overline{D}}_3^c , where i, j = 1, 2. The hadronic form factors are calculated using an SU(3) phenomenological Lagrangian approach for the proton, as well as several hyperons and charmed baryons. Since the decay of the neutralino is kinematically and CKM suppressed in this theoretical scenario, it decays outside the detector and appears experimentally only as missing energy. We detail the analysis techniques at the experimental level and estimate the background in the {B}^{+}to p{overset{sim }{chi}}_1^0 search using published results for {B}^{+}to {K}^{+}nu overline{nu} . Our final sensitivity plots are shown for both {lambda}_{113}^{prime prime } versus the squark mass {m}_{tilde{q}} and {lambda}_{113}^{prime prime }/{m}_{tilde{q}}^2 versus the neutralino mass {m}_{{overset{sim }{chi}}_1^0} . We find that the search at Belle II could probe {lambda}_{113}^{prime prime }/{m}_{tilde{q}}^2 down to the order of 10−8 GeV−2 in the kinematically allowed {m}_{{overset{sim }{chi}}_1^0} range. We also obtain current limits on {lambda}_{123}^{prime prime } by recasting an existing search interpreted as {B}^0to {Lambda}^0{overset{sim }{chi}}_1^0 , and comment about searches for {B}^{+}to {Sigma}^{+}{overset{sim }{chi}}_1^0 , {B}^0to {Sigma}^0{chi}_1^0 , {B}^{+}to {Lambda}_c^{+}{overset{sim }{chi}}_1^0 , and {B}^{+}to {Xi}_c^{+}{overset{sim }{chi}}_1^0 . In closing, we briefly discuss potential searches at the LHCb and BESIII experiments.

Searching for a single photon from lightest neutralino decays in R-parity-violating supersymmetry at FASER

In this work, we propose a search for a single photon at FASER and FASER2, 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 \U0001d4aa(0.1) − \U0001d4aa(1) TeV. We find a sensitivity reach for RPV couplings beyond the current bounds by orders of magnitude at FASER and FASER2.

Determination of coupling patterns by parallel searches for μ− → e+ and μ− → e− in muonic atoms

We investigate a possibility that the μ−→e+ conversion is discovered prior to the μ−→e− conversion, and its implications to the new physics search. We focus on the specific model including the mixing of the SU(2)L doublet- and singlet-type scalar leptoquarks, which induces not only the lepton flavor violation but also the lepton number violation. Such a structure is motivated by R-parity violating (RPV) supersymmetric models, where a sbottom mediates the conversion processes. We formulate the μ−→e+ rate in analogy with the muon capture in a muonic atom, and numerically evaluate it using several target nuclei. The lepton flavor universality test of pion decay directly limits the μ−→e+ rate, and the maximally allowed μ−→e+ branching ratio is ∼10−18 under the various bounds on RPV parameters. We show that either μ−→e− or μ−→e+ signals can be discovered in near future experiments. This indicates that parallel searches for these conversions will give us significant information on the pattern of coupling constants.

Fixed points in supersymmetric extensions of the standard model

We search for weakly interacting fixed points in extensions of the minimally supersymmetric standard model (MSSM). Necessary conditions lead to three distinct classes of anomaly-free extensions involving either new quark singlets, new quark doublets, or a fourth generation. While interacting fixed points arise prolifically in asymptotically free theories, their existence is significantly constrained as soon as some of the non-abelian gauge sectors are infrared free. Performing a scan over sim 200k different MSSM extensions using matter field multiplicities and the number of superpotential couplings as free parameters, we find mostly infrared conformal fixed points, and a small subset with ultraviolet ones. All settings predict low-scale supersymmetry-breaking and a violation of R-parity. Despite of residual interactions, the running of couplings out of asymptotically safe fixed points is logarithmic as in asymptotic freedom. Some fixed points can be matched to the Standard Model though the matching scale comes out too low. Prospects for higher matching scales and asymptotic safety beyond the MSSM are indicated.

Searching for light neutralinos with a displaced vertex at the LHC

We study a bino-like light neutralino (χ~10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\overset{\\sim }{\\chi}}_1^0 $$\\end{document}) produced at the LHC from the decay of a scalar lepton (e~L\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ ilde{e}_L $$\\end{document}) through the process pp →e~L\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ ilde{e}_L $$\\end{document}→eχ~10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ e{\\overset{\\sim }{\\chi}}_1^0 $$\\end{document} in the context of R-parity-violating (RPV) supersymmetry where χ~10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\overset{\\sim }{\\chi}}_1^0 $$\\end{document} is the lightest supersymmetric particle. For small masses and RPV couplings, the neutralino is naturally long-lived and its decay products can be identified as displaced tracks. Following existing searches, we propose a displaced-vertex search strategy for such a light neutralino with a single RPV coupling switched on, λ111′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\lambda}_{111}^{\\prime } $$\\end{document}, in the mass range 10 GeV ≲ mχ~10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {m}_{{\\overset{\\sim }{\\chi}}_1^0} $$\\end{document} ≲ 230 GeV. We perform Monte Carlo simulations and conclude that at the high-luminosity LHC, the proposed search can probe values of λ111′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\lambda}_{111}^{\\prime } $$\\end{document} down to two orders of magnitude smaller than current bounds and up to 40 times smaller than projected limits from monolepton searches.

Sleptonic SUSY: from UV framework to IR phenomenology

We study an attractive scenario, “Sleptonic SUSY”, which reconciles the 125 GeV Higgs scalar and the non-observation of superpartners thus far with potentially pivotal roles for slepton phenomenology: providing viable ongoing targets for LHC discovery, incorporating a co-annihilation partner for detectable thermal relic dark matter, and capable of mediating the potential muon g − 2 anomaly. This is accomplished by a modestly hierarchical spectrum, with sub-TeV sleptons and electroweakinos and with multi-TeV masses for the other new states. We study new elements in the UV MSSM realization of Sleptonic SUSY based on higher-dimensional sequestering and the synergy between the resulting gaugino-mediation, hypercharge D-term mediation and Higgs-mediation of SUSY-breaking, so as to more fully capture the range of possibilities. This framework stands out by harmoniously solving the flavor, CP and μ − Bμ problems of the supersymmetric paradigm. We discuss its extension to orbifold GUTs, including gauge-coupling and b-tau unification. We also develop a non-minimal model with extra Higgs fields, in which the electroweak vacuum is more readily cosmologically stable against decay to a charge-breaking vacuum, allowing a broader range of sleptonic spectra than in the MSSM alone. We survey the rich set of signals possible at the LHC and future colliders, covering both R-parity conservation and violation, as well as for dark matter detection. While the multi-TeV squarks imply a Little Hierarchy Problem, intriguingly, small changes in parameter space to improve naturalness result in dramatic phase transitions to either electroweak-preservation or charge-breaking. In a Multiverse setting, the modest unnaturalness may then be explained by the “principle of living dangerously”.

Supersymmetric explanation of the muon g – 2 anomaly with and without stable neutralino

In this paper we explore the possibility of explaining the muon g − 2 anomaly in various types of supersymmetric extensions of the Standard Model. In particular, we investigate and compare the phenomenological constraints in the MSSM with stable neutralino and the other types of scenarios where the neutralino is unstable. For the latter case we study the Gauge Mediated SUSY Breaking (GMSB) scenario with very light gravitino and the UDD-type R-Parity Violating (RPV) scenario. In the MSSM with stable neutralino, the parameter region favoured by the (g − 2)μ is strongly constrained by the neutralino relic abundance and the dark matter direct detection experiments, as well as by the LHC searches in the lepton plus missing transverse energy channel. On the other hand, the scenarios without stable neutralino are free from the dark matter constraints, while the LHC constraints depends strongly on the decay of the neutralino. We find that in GMSB the entire parameter region favoured by the muon g − 2 is already excluded if the Next Lightest SUSY Particle (NLSP) is the neutralino. In the GMSB scenario with a stau NSLP and in the RPV scenario, LHC constraints are weaker than the stable neutralino case and a larger region of parameter space is available to fit the (g − 2)μ anomaly.

Testing exotic scalars with HiggsBounds

The program HiggsBounds is a well-established tool for testing Beyond-the-Standard Model (BSM) theories with an extended Higgs sector against experimental limits from collider searches at LEP, Tevatron and LHC. Thus far, it could be applied to any neutral or charged Higgs bosons originating from the modified Higgs sector. Implicitly, these particles were assumed to exhibit a somewhat hierarchical Yukawa structure as present in the Standard Model, where in particular the couplings to first generation fermions could be neglected. In this work, we extend the HiggsBounds functionalities to go beyond these restrictions, thus making the code applicable to any neutral or charged BSM scalars. Moreover, we develop a new approach to implement experimental searches whose kinematic acceptance depends significantly on the values of the involved couplings. We achieve this by recasting the searches to general scalar models. Using this approach we incorporate relevant current experimental limits from LHC searches for exotic scalars, and present the implications of these limits for a dark matter scalar mediator model, a flipped Two-Higgs-Doublet Model and a supersymmetric model with R-parity violation.

Seesaw mechanism in the R-parity-violating supersymmetric standard model with the gauged flavor U(1)X symmetry

Abstract We study the seesaw mechanism in the supersymmetric standard model (SSM) with the ${\mathbb {Z}}_3$ symmetry called matter triality (M3). The Abelian discrete symmetry prohibits the baryon number violation operators at the (non-)renormalizable level, which ensures proton longevity. The cubic coupling by right-handed neutrinos generates the Majorana mass term after the right-handed sneutrinos develop into the vacuum expectation values. Due to the R-parity violation, the active neutrino masses can be generated not only from the mixings with the right-handed neutrinos but also from those with the minimal SSM neutralinos. We propose a model where M3 is embedded in the gauged flavor symmetry. The flavor charges are constrained by the anomaly cancellation conditions and the requirements to realize the fermion masses and mixing angles in the quark and lepton sectors. We analyze the assignments of the flavor charge, and show that the sterile neutrino mass is allowed to be below the soft supersymmetry-breaking scale, which is constrained by the half-lifetime of the neutrinoless double beta decay.

R-parity violation axiogenesis

We show that the rotation of the QCD axion field, aided by B−L violation from supersymmetric R-parity violating couplings, can yield the observed baryon abundance. Strong sphaleron processes transfer the angular momentum of the axion field into a quark chiral asymmetry, which R-parity violating couplings convert to the baryon asymmetry of the Universe. We focus on the case of dimensionless R-parity violating couplings with textures motivated by grand unified theories and comment on more general scenarios. The axion decay constant and mass spectrum of supersymmetric particles are constrained by Big Bang nucleosynthesis, proton decay from the R-parity violation, and successful thermalization of the Peccei-Quinn symmetry breaking field. Axion dark matter may be produced by the axion rotation via the kinetic misalignment mechanism for axion decay constants below 1010 GeV, or by the conventional misalignment mechanism for 1011-12 GeV. The viable parameter region can be probed by proton decay and axion searches. This scenario may also have connections with collider experiments, including searches for long-lived particles, and observations of gravitational waves.

Searching for light long-lived neutralinos at Super-Kamiokande

Light neutralinos could be copiously produced from the decays of mesons generated in cosmic-ray air showers. These neutralinos can be long-lived particles in the context of R-parity violating (RPV) supersymmetric models, implying that they could be capable of reaching the surface of the earth and decay within the instrumental volume of large neutrino detectors. In this letter, we use atmospheric neutrino data from the Super-Kamiokande experiment to derive novel constraints for the RPV couplings involved in the production of long-lived light neutralinos from the decays of charged $D$-mesons and kaons. Our results highlight the potential of neutrino detectors to search for long-lived particles, by demonstrating that it is possible to explore regions of parameter space that are not yet constrained by any fixed-target nor collider experiments.

Search for top squarks in final states with two top quarks and several light-flavor jets in proton-proton collisions at s=13 TeV

Many new physics models, including versions of supersymmetry characterized by $R$-parity violation (RPV), compressed mass spectra, long decay chains, or additional hidden sectors, predict the production of events with top quarks, low missing transverse momentum, and many additional quarks or gluons. The results of a search for new physics in events with two top quarks and additional jets are reported. The search is performed using events with at least seven jets and exactly one electron or muon. No requirement on missing transverse momentum is imposed. The study is based on a sample of proton-proton collisions at $\sqrt{s} =$ 13 TeV corresponding to 137 fb$^{-1}$ of integrated luminosity collected with the CMS detector at the LHC in 2016-2018. The data are used to determine best fit values and upper limits on the cross section for pair production of top squarks in scenarios of RPV and stealth supersymmetry. Top squark masses up to 670 (870) GeV are excluded at 95% confidence level for the RPV (stealth) scenario, and the maximum observed local signal significance is 2.8 standard deviations for the RPV scenario with top squark mass of 400 GeV.

Long-lived light neutralinos at Belle II

We consider light neutralinos of mass about 1 GeV, produced from τ lepton rare decays at Belle II, in the context of R-parity-violating (RPV) supersymmetry. With large and clean samples of τ leptons produced at the Belle II experiment, excellent sensitivity to such light neutralinos with the exotic signatures of displaced vertices is expected. We focus on two benchmark scenarios of single RPV operators, {lambda}_{311}^{prime }{L}_3{Q}_1{overline{D}}_1 and {lambda}_{312}^{prime }{L}_3{Q}_1{overline{D}}_2 , which induce both the production and decay of the lightest neutralino. For the reconstruction of a displaced vertex, we require at least two charged pions in the final states. We perform Monte-Carlo simulations for both signal and background events, and find that Belle II can explore regions in the parameter space competitive with other probes. In particular, for the {lambda}_{311}^{prime } scenario, it can put limits up to two orders of magnitude stronger than the current bounds.

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.

Qualities of the axion and LSP in Pati-Salam unification with Z4R×ZN symmetry

In this paper we construct supersymmetric Pati-Salam (PS) models containing the minimal supersymmetric standard model and an invisible axion. The models include two discrete symmetries, ${\mathbb{Z}}_{4}^{R}\ifmmode\times\else\texttimes\fi{}{\mathbb{Z}}_{N}$, which maintain the quality of the accidental Peccei-Quinn (PQ) symmetry and thus the solution to the strong $CP$ problem. We require that the discrete anomaly conditions are satisfied for both ${\mathbb{Z}}_{4}^{R}\ifmmode\times\else\texttimes\fi{}{G}_{\mathrm{PS}}^{2}$ and ${\mathbb{Z}}_{N}\ifmmode\times\else\texttimes\fi{}{G}_{\mathrm{PS}}^{2}$. The vacuum expectation value of the PQ field spontaneously breaks all the discrete symmetries. R-parity is violated if any of the PQ field(s) has an odd charge under ${\mathbb{Z}}_{4}^{R}$. We present two explicit models which we refer to as a minimal model where R-parity violation is extremely suppressed, and a nonminimal model where R-parity violation is significant. In the latter model, the neutralino becomes unstable even if it is the lightest supersymmetric particle (LSP), and, in addition, there are new low-energy vectorlike states. In both examples, R-parity violation is sufficiently suppressed such that the proton is stable.