R-parity Violating SUSY Models Research Articles

Confronting recent AMS-02 positron fraction and Fermi-LAT extragalactic γ-ray background measurements with gravitino dark matter

Recent positron flux fraction measurements in cosmic-rays (CR) made by the AMS-02 satellite confirm and extends the evidence on the existence of a new (yet unknown) source of high energy positrons. To explain this excess, we use the gravitino of bilinear R-parity violating SUSY models as a decaying Dark Matter candidate, as the source of those high energy particles. Being a long lived weak-interacting and spin 3/2 particle, it offers several particularities which makes it an attractive candidate. We compute the electron, positron and $\gamma$-ray\ fluxes produced by each gravitino decay channel at the Earth. Combining the flux from the different decay modes we can fit AMS-02 measurements of the positron fraction, as well as the electron and positron fluxes, with a gravitino mass in the range $1-2$ TeV and lifetimes of $\sim 1.0-0.8\times 10^{26}$ s. . Then, we study the viability of these scenarios through their implications in $\gamma$-ray observations. We set limits on the gravitino lifetime using the Extragalactic $\gamma$-ray Background recently reported by the {\it Fermi}-LAT Collaboration and a state-of-the-art model of its known contributors. These limits exclude the gravitino parameter space which provides an acceptable explanation of the AMS-02 data. Therefore, we conclude that the gravitino of bilinear R-parity violating models is ruled out as the unique primary source of electrons and positrons needed to explain the rise in the positron fraction.

Way to crosscheckμ−econversion in the case of no signals ofμ→eγandμ→3e

We consider the case that the $\ensuremath{\mu}\ensuremath{-}e$ conversion signal is discovered but other charged lepton flavor violating (cLFV) processes will never be found. In such a case, we need other approaches to confirm the $\ensuremath{\mu}\ensuremath{-}e$ conversion and its underlying physics without conventional cLFV searches. We study R-parity violating (RPV) SUSY models as a benchmark. We briefly review that our interesting case is realized in RPV SUSY models with reasonable settings in light of current theoretical and experimental status. We focus on the exotic collider signatures at the LHC ($pp\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ensuremath{-}}{e}^{+}$ and $pp\ensuremath{\rightarrow}jj$) as the other approaches. We show the correlations between the branching ratio of the $\ensuremath{\mu}\ensuremath{-}e$ conversion process and cross sections of these processes. It is the first time that these correlations have been graphically shown. We exhibit the RPV parameter dependence of the branching ratio and the cross sections and discuss the feasibility of determining the parameters.

Search for R-parity violating Supersymmetry using the CMS detector

In this talk, the latest results from CMS on R-parity violating Supersymmetry are reviewed. We present results using up to 20/fb of data from the 8 TeV LHC run of 2012. Interpretations of the experimental results in terms of production of squarks, gluinos, charginos, neutralinos, and sleptons within R-parity violating susy models are presented.

Stau kinks at the LHC

The kink signature of charged tracks is predicted in some SUSY models, and it is very characteristic signal at collider experiments. We study the kink signature at LHC using two models, SUSY models with a gravitino LSP and a stau NLSP, and R-parity violating SUSY models with a stau (N)LSP. We find that a large number of kink events can be discovered in a wide range of the SUSY parameters, when the decay length is O(10-10^5)mm. Model discrimination by identifying the daughter particles of the kink tracks is also discussed.

Hadronic electric dipole moments inR-parity violating supersymmetry

We calculate the electric dipole moments (EDM) of the neutral {sup 199}Hg atom, neutron and deuteron within a generic R-parity violating SUSY model (Re{sub p} SUSY) on the basis of a one-pion-exchange model with CP-odd pion-nucleon interactions. We consider two types of the Re{sub p} SUSY contributions to the above hadronic EDMs: via the quark chromoelectric dipole moments (CEDM) and CP-violating 4-quark interactions. We demonstrate that the former contributes to all the three studied EDMs while the latter appears only in the nuclear EDMs via the CP-odd nuclear forces. We find that the Re{sub p} SUSY induced 4-quark interactions arise at tree level through the sneutrino exchange and involve only s and b quarks. Therefore, their effect in hadronic EDMs is determined by the strange and bottom-quark sea of the nucleon. From the null experimental results on the hadronic EDMs we derive the limits on the imaginary parts of certain products Im({lambda}{sup '}{lambda}{sup '}*) of the trilinear Re{sub p}-couplings and show that the currently best limits come from the {sup 199}Hg EDM experiments. We demonstrate that some of these limits are better than those existing in the literature. We argue that future storage ring experiments on the deuteron EDM aremore » able to improve these limits by several orders of magnitude.« less

The [formula omitted] puzzle and supersymmetric models

In the light of new experimental results on B→Kπ decays, we study the decay processes B→Kπ in the framework of both R-parity conserving (SUGRA) and R-parity violating supersymmetric models. We find that any possible deviations from the Standard Model indicated by the current data for the branching ratios and the direct CP asymmetries of B→Kπ can be explained in both R-parity conserving SUGRA and R-parity violating SUSY models. However, there is a difference between the predictions of both models to the time-dependent CP asymmetry observable SKSπ0 whose current experimental results include large uncertainties. We demonstrate that this difference can be useful for testing both models with more accurate data for SKSπ0 and ACP+− in the near future.

CP asymmetries of [formula omitted] and [formula omitted] decays using a global fit in QCD factorization

We analyze the CP asymmetries of B→ϕK and B→η(′)K modes in the QCD improved factorization framework. The phenomenological parameters are determined from the global fit for the available B→PP and VP modes (without the subprocess b→ss¯s). The large negative sin(2ϕ1)ϕKs and the large branching ratio for B±→η′K± can be simultaneously explained in the context of R-parity conserving SUGRA models and R-parity violating SUSY models satisfying all possible experimental data. The SUSY models are also consistent with the available data on the CP asymmetries for different B±(0)→ϕK±(0) and B±(0)→η(′)K±(0) modes.

Constraining R-parity violating couplings using dimuon data at Tevatron Run-II

The dimuon plus dijet signal is analyzed in the top squark pair production at Tevatron Run-II experiment and the total event rate is compared with the existing dimuon data. This comparison rules out top squark mass upto 188 (104) GeV for the branching fraction 100% (50%) of top squark decay into the muon plus quark via lepton number violating coupling. Interpretation of this limit in the framework of R-parity violating (RPV) SUSY model puts limit on relevant RPV coupling for a given top squark mass and other supersymmetric model parameters. If m t ˜ 1 ≲ 180 GeV we found that the RPV couplings are roughly restricted to be within ∼ 10 − 4 which is at the same ballpark value obtained from the neutrino data. The limits are very stringent for a scenario where top squarks appear to be the next lightest supersymmetric particles.

Particle physics implications of the WMAP neutrino mass bound

The recently published cosmological bound on the absolute neutrino masses obtained from the Wilkinson microwave anisotropy probe (WMAP) data has important consequences for neutrino experiments and models. Taken at face value, the new bound excludes the determination of the absolute neutrino mass in the KATRIN experiment and disfavors a neutrino oscillation interpretation of the LSND experiment. Combined with the KamLAND and Super-K data, the WMAP bound defines an accessible range for the neutrinoless double beta decay amplitude. The bound also impacts the Z-burst annihilation mechanism for resonant generation of extreme-energy cosmic rays on the cosmic neutrino background in two ways: it constrains the local over-density of neutrino dark matter which is not helpful, but it also limits the resonant energy to a favorable range. In R-parity violating SUSY models, neutrino masses are generated by trilinear and bilinear lepton number violating couplings. The WMAP result improves the constraints on these couplings by an order of magnitude.

Large enhancement of D±→e±ν and D±s→e±ν in R-parity violating SUSY models

The purely leptonic decays D±→e±ν and D±s→e±ν, for which no experimental limits exist, are highly suppressed in the Standard Model. Mere observation of these decays at the B factories Belle/BaBar or forthcoming CLEO-c would be a clear signal of physics beyond the SM. We show that R-parity violating slepton contributions can give rise to spectacular enhancements of the decay rates, resulting in branching ratios as large as 5×10−3, which strongly motivates a search in these channels.

Testing radiative neutrino mass generation via R-parity violation at the Tevatron

An R-parity violating SUSY model with lepton-number violating couplings λ′ i33 , i=2,3, can generate a neutrino mass spectrum that explains the recent results from neutrino oscillation experiments. These R-parity violating couplings lead to a clean signal with at least one isolated lepton and at least three tagged b jets that is accessible in chargino and neutralino production at the Tevatron collider. This signature can be probed at 3 σ up to m 1/2=230 GeV (320 GeV) with an integrated luminosity of 2 fb −1 (30 fb −1).

Search for single leptoquark and squark production in electron-photon scattering at $\sqrt{s_{\rm ee}}=189$ GeV at LEP

A search for first generation scalar and vector leptoquarks (LQ) as well as for squarks in R-parity violating SUSY models has been performed using e+e- collisions collected with the OPAL detector at LEP at an e+e- centre-of-mass energy sqrt(s_ee) of 189 GeV. The data correspond to an integrated luminosity of about 160 pb-1. The dominant process for this search is e q -> LQ/squark -> e q, nu q, where a photon, which has been radiated by one of the beam electrons, serves as a source of quarks. The numbers of selected events found in the two decay channels are in agreement with the expectations from Standard Model processes. This result allows to set lower limits at the 95% confidence level on the mass of first generation scalar and vector leptoquarks, and of squarks in R-parity violating SUSY models. For Yukawa couplings lambda to fermions larger than sqrt{4 pi alpha_em}, the mass limits range from 121 GeV/c^2 to 175 GeV/c^2 (149 GeV/c^2 to 188 GeV/c^2) depending on the branching ratio beta of the scalar (vector) leptoquark state. Furthermore, limits are set on the Yukawa couplings lambda for leptoquarks and lambda'_1jk for squarks, and on beta as a function of the scalar leptoquark/squark mass.

Search for leptoquarks in electron–photon scattering at up to 209 GeV at LEP

Searches for first generation scalar and vector leptoquarks, and for squarks in R-parity violating SUSY models with the direct decay of the squark into Standard Model particles, have been performed using e+e− collisions collected with the OPAL detector at LEP at e+e− centre-of-mass energies between 189 and 209 GeV. No excess of events is found over the expectation from Standard Model background processes. Limits are computed on the leptoquark couplings for different values of the branching ratio to electron–quark final states.

Particle physics implications of neutrinoless double beta decay

Neutrinoless double beta decay is a sensitive probe of the patterns of neutrino masses and mixings if the neutrinos are Majorana particles as well as other new physics scenarios beyond the standard model. In this talk, the present experimental lower bound on the lifetime for ββ 0 ν is used to constrain the neutrino mixings and set limits on the parameters of the new physics scenarios such as the left-right symmetric models, R-parity violating SUSY models etc which lead to neutrinoless double beta decay. We then discuss proposed high precision searches for ββ 0 ν decay that can provide extremely valuable insight not only into the nature of neutrino mixings and masses but also put constraints on (or even rule out) new physics scenarios.

R-parity violating SUSY or leptoquarks: virtual effects in dilepton production

In the Standard Model (SM), dilepton production in hadron-hadron collisions proceeds through the conventional Drell-Yan mechanism q q → l +l − with the exchange of a gauge boson. Some extensions of the SM contain a quark-lepton contact interaction via a qlΦ Yukawa coupling, where Φ is a scalar. Theories with scalar leptoquarks and R-parity violating SUSY models are the most important examples of such extensions. These Yukawa couplings induce a different dynamical configuration compared to the SM ( t-channel vs. s-channel) in the q q → l +l − process and thus offer the possibility of being identifiable upon imposition of suitable kinematic cuts. We discuss these effects in the context of the dilepton production in the CDF experiment, and explore consequences in the forthcoming Large Hadron Collider (LHC).

R-parity violating SUSY model

This is a phenomenological review of $R$ parity violating SUSY models, with particular emphasis on explicit $R$ parity violation.

Squark and gluino mass limits in R-parity violating SUSY model from the Tevatron dilepton data

We consider a R-parity-violating SUSY model, containing lepton-number-violating Yukawa couplings. Analysing the Tevatron dilepton data in terms of this model we get a lower mass limit of 100 GeV for squark and gluino. This is comparable to the corresponding limit obtained from the Tevatron missing- p T data in the R-conserving SUSY model. Taken together, they imply a lower squark/gluino mass limit of 100 GeV for any value of the relevant lepton-number-violating Yukawa couplings.