arXiv subjects
Publications and source records attributed to Rathin Adhikari.
We propose the novel lepton-number relationship $L_τ= L_e + L_μ$, which is uniquely realized by the interaction $(\hat ν_e \hat μ- \hat e \hat ν_μ) \hat τ^c$ in supersymmetry and may account for a possibly large muon anomalous magnetic moment. Neutrino masses (with bimaximal mixing) may be generated from the spontaneous and soft breaking of this lepton symmetry.
We present a solution of the solar neutrino deficit using three flavors of neutrinos within the R-parity non-conserving supersymmetric model. In vacuum, mass and mixing is restricted to the nu(mu)-nu(tau) sector only, which we choose in consistency with the requirements of the atmospheric neutrino anomaly. The nu(e) is massless and unmixed. The flavor changing and flavor diagonal neutral currents present in the model and an energy-dependent resonance-induced nu(e)-nu(mu) mixing in the sun result in the new solution to the solar neutrino problem. The best fit to the solar neutrino rates and spectrum (1258-day SK data) requires a mass square difference of 10^{-5} eV^2 in vacuum between the two lightest neutrinos. This solution cannot accommodate a significant day-night effect for solar neutrinos.
The mass matrix of three Majorana neutrinos of equal mass is not necessarily proportional to the identity matrix, but expressible in terms of two angles and one phase. We discuss how such a mass matrix may be stable or unstable against radiative corrections. We then propose a model with additional explicit breaking of the threefold degeneracy to account for the atmospheric neutrino data, while the radiative breaking explains the solar neutrino data, using the large-angle Mikheyev-Smirnov-Wolfenstein solution. Our model requires a nonzero effective $ν_e$ mass for neutrinoless double beta decay close to the present experimental upper limit of 0.2 eV.
With only three flavors it is possible to account for various neutrino oscillation experiments. The masses and mixing angles for three neutrinos can be determined from the available experimental data on neutrino oscillation and from the astrophysical arguments. We have shown here that such masses and mixing angles which can explain atmospheric neutrino anomaly, LSND result and the solar neutrino experimental data, can be reconciled with the R-parity violating Supersymmetric Models through lepton number violating interactions. We have estimated the order of magnitude for some lepton number violating couplings. Our analysis indicates that the lepton number violation is likely to be observed in near future experiments. From the data on neutrino oscillation and the electric dipole moment of electron, under some circumstances it is possible to obtain constraint on the complex phase of some supersymmetry breaking parameters in R-parity violating Supersymmetric models.
We propose a simple scenario for baryogenesis in supersymmetric models where baryon number is broken alongwith R-parity. The lightest supersymmetric particle (neutralino) decays to three quarks and $CP-$ violation comes from interference of tree and one loop box diagrams. The bounds on the $R-$parity breaking couplings from the out-of-equilibrium condition are considerably relaxed in this scenario.
We consider generation of baryon asymmetry of the universe through $R-$parity violation in a scenario in which out-of-equilibrium condition is satisfied by making the electroweak phase transition to be first order. We study all the $R-$parity violating interaction which can generate $(B-L)$ asymmetry which then converts to baryon asymmetry of the universe. We demonstrate that CP--violating sfermion deudy all the $R-$parity violating interaction which can generate $(B-L)$ asymmetry which then converts to baryon asymmetry of the universe. We demonstrate that CP--violating sfermion decays contribute more than that of the neutralino decays in the generation of $(B-L)$ asymmetry.
We consider the signals of pair-produced charginos in an $e^{+}e^{-}$ collider, in a scenario where R-parity is spontaneously broken. The possibility of lepton-chargino mixing, together with the presence of a Majoron, opens up the two-body decay channel of a chargino into a tau and a Majoron. We have studied the regions where this is the dominant decay of a chargino, and have shown that over a large region of the parameter space the ensuing signals, namely tau-pairs with missing-$p_T$, may rise well above standard model backgrounds at LEP-II. Such signals can also enable one to distinguish between spontaneous and explicit R-parity breaking.
If a light gaugino sector exists in the supersymmetric standard model then the mass of lightest neutralino may be of the order of 1 GeV or less. As a consequence of neutral flavor violation in supersymmetric theories $B_s$-meson may decay into a pair of lightest neutralinos in such a case. It is found that the parameter space for such light neutralinos can be appreciably constrained by looking for such decays. We also show how a rare B-decays ($B \longrightarrow K(K^{*}) + invisible$ channels) can help us in probing a light neutralino in B-factories in a reasonably model- independent manner. Finally, we observe that that the decay of a tau-lepton into a muon and a pair of light neutralinos can cause a violation of weak universality which is larger in magnitude than that from any source known so far.
In a supersymmetric model with the lightest supersymmetric particle (LSP) $χ$ in the range of a few hundred MeV's, the decay $τ{\longrightarrow} μχχ$ is going to be allowed. We investigate the departure from tau-universality caused by this decay. It is found that the universality violation in this way can be greater than both non-universal electroweak radiative corrections and supersymmetric one-loop corrections over a considerable region of the parameter space allowed by experiments so far. Thus it suggests a method of constraining the parameter space with light LSP's using data from tau-factories.
If a light gaugino sector exists, then the lightest supersymmetric particle (LSP) has a chance of being pair-produced in rare B-decays. As a consequence of neutral flavour violation in most supersymmetric models, such decays can occur at the tree-level and reinforce the channels $B \longrightarrow K(K^{*}) + invisible$. We discuss how a study of such decay spectra in B-factories can help us either identify or exclude a light LSP.
If massive invisible particles are pair-produced in a three-body decay, then the energy distribution of the other (visible) product is sensitive to the mass of the invisible pair. We use this fact in the context of a Higgs boson decaying into (i)a Z-boson and two massive neutrinos of a fourth generation, and (ii)a Z and two lightest particles in the minimal supersymmetric standard model. We discuss how the Z-energy spectrum in each case can reflect the values of the parameters in such models. (3 figures, hard copies available from authers on request).