R-parity Violation Operators Research Articles

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.

R-parity violation in F-theory

We discuss R-parity violation (RPV) in semi-local and local F-theory constructions. We first present a detailed analysis of all possible combinations of RPV operators arising from semi-local F-theory spectral cover constructions, assuming an $SU(5)$ GUT. We provide a classification of all possible allowed combinations of RPV operators originating from operators of the form $10\cdot \bar 5\cdot \bar 5$, including the effect of $U(1)$ fluxes with global restrictions. We then relax the global constraints and perform explicit computations of the bottom/tau and RPV Yukawa couplings, at an $SO(12)$ local point of enhancement in the presence of general fluxes subject only to local flux restrictions. We compare our results to the experimental limits on each allowed RPV operator, and show that operators such as $LLe^c$, $LQd^c$ and $u^cd^cd^c$ may be present separately within current bounds, possibly on the edge of observability, suggesting lepton number violation or neutron-antineutron oscillations could constrain F-theory models.

Phenomenology of a long-lived LSP with R-parity violation

We present the leading experimental constraints on supersymmetric models with R-parity violation (RPV) and a long-lived lightest superpartner (LSP). We consider both the well-motivated dynamical RPV scenario as well as the conventional holomorphic RPV operators. Guided by naturalness, we study the cases of stop, gluino, and higgsino LSPs with several possible leading decay channels in each case. The CMS displaced dijet and the ATLAS multitrack displaced vertex searches have been fully recast, with all cuts and vertex reconstruction algorithms applied. Heavy charged stable particle searches by CMS are also applied. In addition, we consider representative bounds for prompt LSP decays that are directly applicable. Our main results are exclusion plots in the $m_{\rm LSP}-\tau_{\rm LSP}$ plane for the various scenarios. We find that the natural parameter space ($m_{\tilde{t}} <800$ GeV, $m_{\tilde{g}}<1500$ GeV, $m_{\tilde{H}}<800$ GeV) is excluded for a long-lived LSP ($\tau_{\rm LSP} \gtrsim 1$ mm).

R-parity violating chargino decays at the LHC

Supersymmetric models with R-parity violation (RPV) have become more popular following the lack of any excess of missing energy events at the 8 TeV LHC. To identify such models, the suggested searches generally rely on the decay products of the (effectively) lightest supersymmetric particle (LSP), with signals that depend on the identity of the LSP and the relevant RPV operators. Here we look at the prospects for detecting RPV chargino decays at the LHC and find substantial patches of parameter space in the Minimal Supersymmetric Standard Model with possibly spectacular signatures, such as three charged-lepton resonances.

DynamicalR-Parity Violation

We present a new paradigm for supersymmetric theories with R-parity violation (RPV). At high scale, R parity is conserved in the visible sector but spontaneously broken in the supersymmetry-breaking sector. The breaking is then dynamically mediated to the visible sector and is manifested via nonrenormalizable operators at low energy. Consequently, RPV operators originate from the Kähler potential rather than the superpotential, and are naturally suppressed by the supersymmetry-breaking scale, explaining their small magnitudes. A new set of nonholomorphic RPV operators is identified and found to often dominate over the standard RPV ones. We study the relevant low-energy constraints arising from baryon-number violating processes, proton decay, and flavor changing neutral currents, which may all be satisfied if a solution to the standard model flavor puzzle is incorporated. The chiral structure of the RPV operators implies new and distinct collider signatures, indicating the need to alter current techniques in searching for RPV at the LHC.

Gauging the way to MFV

We 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 UDD 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.

New patterns of natural R-parity violation with supersymmetric gauged flavor

We 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 u c d c d c 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.

LHC coverage of RPV MSSM with light stops

We 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.

R-Parity Violation and Family Symmetry

In this talk, we investigate the implications of R-parity violating (RPV) operators in a model with family symmetry 1. Family symmetry can determine the form of RPV operators as well as the Yukawa matrices. We consider a concrete model with non-abelian discrete symmetry Q6, which has only three RPV trilinear operators with no baryon number violating terms. We find that ratios of decay rates of the lepton flavor violating processes are fixed thanks to the family symmetry, predicting [Formula: see text].