Bilinear R-parity Violation Research Articles

SIGNALS FOR LIGHT DARK MATTER AXINO

Light dark matter aims at explaining the 511 keV γ-ray line emission from the galactic bulge as well as cold dark matter in our universe. The former is achieved via the annihilations or decays of light dark matter particles, which implies interesting observational consequences in addition to 511 keV γ-rays. We consider the axino in the 1 ~ 10 MeV mass range as the light dark matter particle and discuss the particle physics models for it, its cosmological production, and its decay arising from R-parity violation. For additional observational signals, we consider the connection to the neutrino data made by bilinear R-parity violations and the continuum γ-ray emission from light dark matter particles.

Higgs and neutrino sector, EDM and εK in a spontaneously CP and R-parity breaking supersymmetric model

We construct an extension of the supersymmetric standard model where both CP symmetry and R-parity are spontaneously broken. We study the electroweak symmetry breaking sector of the model and find minima consistent with the experimental bounds on Higgs boson masses. Neutrino masses and mixing angles are generated through both seesaw and bilinear R-parity violation. We show that the hierarchical mass pattern is obtained, and mixings are consistent with measured values. Due to the spontaneous CP and R-parity violation, the neutrino sector is CP violating, and we calculate the corresponding phase. We further restrict the parameter space to agree with the limits on the electric dipole moment of the neutron. Finally, we study the CP violation parameter εK in the kaon system and show that we obtain results consistent with the experimental value.

Axino light dark matter and neutrino masses with R-parity violation

Motivated by the recent observation of the 511 keV $\gamma$-ray line emissions from the galactic bulge and an explanation for it by the decays of light dark matter particles, we consider the light axino whose mass can be in the 1-10 MeV range, particularly, in the context of gauge-mediated supersymmetry breaking models. We discuss the production processes and cosmological constraints for the light axino dark matter. It is shown that the bilinear R-parity violating terms provide an appropriate mixing between the axino and neutrinos so that the light axino decays dominantly to $e^+ e^- \nu$. We point out that the same bilinear R-parity violations consistently give both the lifetime of the axino required to explain the observed 511 keV $\gamma$-rays and the observed neutrino masses and mixing.

A new mechanism of neutrino mass generation in the NMSSM with broken lepton number

In the Minimal Supersymmetric Standard Model with bilinear R-parity violation, only one neutrino eigenstate acquires a mass at tree level, consequently experimental data on neutrinos cannot be accommodated at tree level. We show that in the Next-to-Minimal extension, where a gauge singlet superfield is added to primarily address the so-called $\mu$-problem, it is possible to generate two massive neutrino states at tree level. Hence, the global three-flavour neutrino data can be reproduced at tree level, without appealing to loop dynamics which is vulnerable to model-dependent uncertainties. We give analytical expressions for the neutrino mass eigenvalues and present examples of realistic parameter choices.

Study of a neutrino mass texture generated in supergravity with bilinear R-parity violation

We study a particular texture of the neutrino mass matrix generated in supergravity with bilinear R-Parity violation. The relatively high value of $\tan\beta$ makes the one-loop contribution to the neutrino mass matrix as important as the tree-level one. The atmospheric angle is nearly maximal, and its deviation from maximal mixing is related to the smallness of the ratio between the solar and atmospheric mass scales. There is also a common origin for the small values of the solar and reactor angles, but the later is much smaller due the large mass ratio between the lightest two neutrinos. There is a high dependence of the neutrino mass differences on the scalar mass $m_0$ and the gaugino mass $M_{1/2}$, but a smaller one of the mixing angles on the same sugra parameters. Measurements of branching ratios for the neutralino decays can give important information on the parameters of the model. There are good prospects at a future Linear Collider for these measurements, but a more detailed analysis is necessary for the LHC.

Neutrinos in anomaly mediated supersymmetry breaking withR-parity violation

We show that a supersymmetric standard model exhibiting anomaly mediated supersymmetry breaking can generate naturally the observed neutrino mass spectrum as well mixings when we include bilinear R-parity violation interactions. In this model, one of the neutrinos gets its mass due to the tree level mixing with the neutralinos induced by the R-parity violating interactions while the other two neutrinos acquire their masses due to radiative corrections. One interesting feature of this scenario is that the lightest supersymmetric particle is unstable and its decay can be observed at high energy colliders, providing a falsifiable test of the model.

Collider tests for neutrino mass generation in a supersymmetric world with R-parity violation

We summarize the low energy features of a supersymmetric class of models with bilinear R-parity violation. We analyze two cases where the supersymmetry breaking is mediated either by supergravity or by anomaly induced contributions to the soft parameters and compare both scenarios in the context of recent neutrino conversion data and collider physics. We show that both classes of models have a large potential to discoveries in collider experiments as well as in neutrino experiments.

Reconstructing neutrino properties from collider experiments in a Higgs triplet neutrino mass model

We extend the minimal supersymmetric standard model with bilinear R-parity violation to include a pair of Higgs triplet superfields. The neutral components of the Higgs triplets develop small vacuum expectation values (VEVs) quadratic in the bilinear R-parity breaking parameters. In this scheme the atmospheric neutrino mass scale arises from bilinear R-parity breaking while for reasonable values of parameters the solar neutrino mass scale is generated from the small Higgs triplet VEVs. We calculate neutrino masses and mixing angles in this model and show how the model can be tested at future colliders. The branching ratios of the doubly charged triplet decays are related to the solar neutrino angle via a simple formula.

Neutrino physics from charged Higgs boson and slepton associated production in anomaly mediated supersymmetry breaking

In the Minimal Supersymmetric Standard Model with bilinear R-Parity violation, terms that violate R-Parity and lepton number are introduced in the superpotential, and sneutrino vacuum expectation values are induced. As a result, neutrino masses and mixing angles are generated via a low energy see-saw mechanism. We show that this model embedded into an anomaly mediated supersymmetry breaking scenario is testable at a linear collider using charged Higgs boson production in association with a stau. This is possible in regions of parameter space where the charged Higgs and stau have similar mass, producing an enhancement of the charged scalar mixing angles. We show that the bilinear parameter and the sneutrino vev can be determined from charged scalar observables, and estimate the precision of this determination.

Bi-large neutrino mixing from bilinear R-parity violation with non-universality

We investigate how the bi-large mixing required by the recent neutrino data can be accommodated in the supersymmetric standard model allowing bilinear R-parity violation and non-universal soft terms. In this scheme, the tree-level contribution and the so-called Grossman–Haber one-loop diagrams are two major sources of the neutrino mass matrix. The relative size of these two contributions falls into the right range to generate the atmospheric and solar neutrino mass hierarchy. On the other hand, the bi-large mixing is typically obtained by a mild tuning of input parameters to arrange a partial cancellation among various contributions.

Probing neutrino properties with charged scalar lepton decays

Supersymmetry with bilinear R-parity violation provides a predictive framework for neutrino masses and mixings in agreement with current neutrino oscillation data. The model leads to striking signals at future colliders through the R-parity violating decays of the lightest supersymmetric particle (LSP). Here we study charged scalar lepton decays and demonstrate that if the scalar tau is the LSP (i) it will decay within the detector, despite the smallness of the neutrino masses, (ii) the relative ratio of branching ratios $\mathrm{Br}({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\tau}}}_{1}\ensuremath{\rightarrow}e\ensuremath{\sum}{\ensuremath{\nu}}_{i})/\mathrm{Br}({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\tau}}}_{1}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\sum}{\ensuremath{\nu}}_{i})$ is predicted from the measured solar neutrino angle, and (iii) scalar muon and scalar electron decays will allow us to test the consistency of the model. Thus, bilinear R-parity breaking SUSY will be testable at future colliders also in the case where the LSP is not the neutralino.

Charged lepton flavor violation in supersymmetry with bilinearR-parity violation

The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R-parity violation naturally predicts a hierarchical neutrino mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. We study whether the individual violation of the lepton numbers L_{e,mu,tau} in the charged sector can lead to measurable rates for BR(mu->e gamma)and $BR(tau-> mu gamma). We find that some of the R-parity violating terms that are compatible with the observed atmospheric neutrino oscillations could lead to rates for mu->e gamma measurable in projected experiments. However, the Delta m^2_{12} obtained for those parameters is too high to be compatible with the solar neutrino data, excluding therefore the possibility of having measurable rates for mu->e gamma in the model.

Basis independent neutrino masses in theRpviolating minimal supersymmetric standard model

We calculate the neutrino mass matrix up to one loop order in the MSSM without R-parity, including the bilinears in the mass insertion approximation. This introduces additional diagrams usually neglected in the literature. We systematically consider the possible new diagrams, and find a few missing from our previous work. We provide analytic expressions for the mass matrix elements in the neutrino flavour basis, which are independent of the $H_d - L_i$ basis choice in the Lagrangian. We compare the contributions from different diagrams, and make ``Lagrangian-basis-independent'' estimates of when the new diagrams need to be included. We briefly discuss the phenomenology of a toy model of bilinear R-parity violation.

Neutrino masses and mixings in the minimal supersymmetric standard model with soft bilinearRpviolation

We analyse a simple RPV extension of the MSSM, with bilinear R-parity violation in the soft terms and vevs, but not between the terms in the superpotential. The model gives two massive neutrinos, and can fit all constraints from neutrino data. We show analytically how to compute the lepton number violating Lagrangian parameters from neutrino masses and mixing angles. Conversely, we numerically vary the bilinear couplings as input parameters to determine the allowed ranges that are consistent with neutrino data. We briefly comment on the implications of our bounds for low energy LFV processes.

Late decaying axino as CDM and its lifetime bound

The axino with mass in the GeV region can be cold dark matter (CDM) in the galactic halo. However, if R-parity is broken, for example by the bilinear terms μ α , then axino (ã) can decay to ν + γ . In this case, the most stringent bound on the axino lifetime comes from the diffuse photon background and we obtain that the axino lifetime should be greater than 3.9×10 24 Ω a ̃ h [s] which amounts to a very small bilinear R-parity violation, i.e., μ α <1 keV. This invalidates the atmospheric neutrino mass generation through bilinear R-violating terms within the context of axino CDM.

Anomaly mediated supersymmetry breaking without R-parity

We analyze the low energy features of a supersymmetric standard model where the anomaly-induced contributions to the soft parameters are dominant in a scenario with bilinear R-parity violation. This class of models leads to mixings between the standard model particles and supersymmetric ones which change the low energy phenomenology and searches for supersymmetry. In addition, R-parity violation interactions give rise to small neutrino masses which we show to be consistent with the present observations.

SpontaneousR-parity violation bounds

We investigate bounds from tree-level and one-loop processes in generic supersymmetric models with spontaneous R-parity breaking in the superpotential. We analyse the bounds from a general point of view. The bounds are applicable both for all models with spontaneous R-parity violation and for explicit bilinear R-parity violation based on general lepton-chargino and neutrino-neutralino mixings. We find constraints from semileptonic B, D and K decays, leptonic decays of the mu and tau, electric dipole moments, as well as bounds for the anomalous magnetic moment of the muon.

Neutrino masses and mixings from supersymmetry with bilinearR-parity violation: A theory for solar and atmospheric neutrino oscillations

The simplest unified extension of the minimal supersymmetric standard model with bilinear R-parity violation naturally predicts a hierarchical neutrino mass spectrum, in which one neutrino acquires mass by mixing with neutralinos, while the other two get mass radiatively. We have performed a full one-loop calculation of the neutralino-neutrino mass matrix in the bilinear ${R}_{p}$ minimal supersymmetric standard model, taking special care to achieve a manifestly gauge invariant calculation. Moreover we have performed the renormalization of the heaviest neutrino, needed in order to get meaningful results. The atmospheric mass scale and maximal mixing angle arise from tree-level physics, while solar neutrino scale and oscillations follow from calculable one-loop corrections. If universal supergravity assumptions are made on the soft-supersymmetry breaking terms then the atmospheric scale is calculable as a function of a single ${R}_{p}$ violating parameter by the renormalization group evolution due to the nonzero bottom quark Yukawa coupling. The solar neutrino problem must be accounted for by the small mixing angle Mikheyev-Smirnov-Wolfenstein (MSW) solution. If these assumptions are relaxed then one can implement large mixing angle solutions. The theory predicts the lightest supersymmetic particle decay to be observable at high-energy colliders, despite the smallness of neutrino masses indicated by experiment. This provides an independent way to test this solution of the atmospheric and solar neutrino anomalies.

Bilinear R-parity violation and small neutrino masses: a self-consistent framework

We study extensions of supersymmetric models without R-parity which include an anomalous U(1) H horizontal symmetry. Bilinear R-parity violating terms induce a neutrino mass at tree level m ν tree≈( θ 2) δ eV where θ≃0.22 is the U(1) H breaking parameter and δ is an integer number that depends on the horizontal charges of the leptons. For δ=1 a unique self-consistent model arises in which (i) all the superpotential trilinear R-parity violating couplings are forbidden by holomorphy; (ii) m ν tree falls in the range suggested by the atmospheric neutrino problem; (iii) radiative contributions to neutrino masses are strongly suppressed resulting in Δm 2 solar≈ few 10 −8 eV 2 which only allows for the LOW (or quasi-vacuum) solution to the solar neutrino problem; (iv) the neutrino mixing angles are not suppressed by powers of θ and can naturally be large.

Lepton flavor violation and bilinear r-parity violation

We examine some flavor changing processes such as rare leptonic decays of the long-lived neutral kaon, muon-electron conversion in nuclei and radiative muon decay which are induced by the combined effects of bilinear and trilinear R-parity violations. These processes are used to put strong constraints on certain products of the bilinear and trilinear couplings. We also discuss the constraints on R-parity violation from neutrino masses and compare them with the constraints from flavor changing decay processes. Large range of parameter space satisfying the constraints from neutrino masses can be excluded by the flavor changing processes considered in this paper, and also vice versa.