arXiv subjects
Publications and source records attributed to Sergey Kovalenko.
We study possible contributions of heavy sterile neutrinos $ν_h$ to the decays $τ^-\to e^{\pm}(μ^{\pm})π^{\mp}π^-$. From the experimental upper bounds on their rates we derive new constraints on the $ν_h-ν_τ$ mixing in the mass region $140.5{MeV}\leq m_{ν_h}\leq 1637$ MeV. We discuss cosmological and astrophysical status of $ν_h$ in this mass region and compare our constraints with those recently derived by the NOMAD collaboration.
We discuss some generic properties of lepton number violating (\Lv) processes and their relation to different entries of the Majorana neutrino mass matrix. Present and near future experiments searching for these processes, except the neutrinoless double beta decay, are unable to probe light(eV mass region) and heavy(hundred GeV mass region) neutrinos. On the other hand due to the effect of a resonant enhancement, some of \Lv decays can be very sensitive to the intermediate mass neutrinos with typical masses in hundred MeV region. These neutrinos may appear as admixtures of the three active and an arbitrary number of sterile neutrino species. We analyze the experimental constraints on these massive neutrino states and discuss their possible cosmological and astrophysical implications.
Recently an upper bound on the rate of the lepton number violating decay $K^+\to μ^+μ^+π^-$ has been significantly reduced by the E865 experiment at BNL and further improvement is expected in the near future. We study this process as a possible source of information on neutrino masses and mixings. We find that it is insensitive to the light(eV domain) and heavy(GeV domain) neutrinos. However due to the effect of a resonant enhancement this decay is very sensitive to neutrinos $ν_j$ in the mass region $245{MeV}\leq m_{ν_j}\leq 389$ MeV. At present experimental sensitivity we deduce new stringent limits on the neutrino mixing matrix element $U_{μj}$ for neutrino masses in this region.
We study the possibility of a large CP/T-violation in lepton pair production in the collisions of polarized protons at RHIC-BNL. We propose the single transverse spin asymmetry which quantifies the possible CP/T-violating effect in this reaction as a sensitive indicator of physics beyond the standard model(SM). We consider two examples of mechanisms beyond the SM which can generate a non-zero asymmetry of this type. They rely on the R-parity violating interactions of supersymmetric models and on phenomenological tensor interactions. We estimate the prospects for observing this effect in future experiments.
The exotic neutrinoless $μ^- - e^-$ nuclear conversion is studied within the conventional extensions of the standard model as well as in the minimal supersymmetric (SUSY) models with and without R-parity conservation. The dependence of the $μ^- - e^-$ conversion rates on the nucleon and nuclear structure is consistently taken into account. Using our calculated transition matrix elements and the available experimental data on the branching ratio $R_{μe^-}$ for $^{48}$Ti and $^{208}$Pb as well as the expected experimental sensitivity for $^{27}$Al employed as a target in the planned at Brookhaven $μ^--e^-$ conversion (MECO) experiment, we extract very severe constraints for the flavor violation parameters. We especially emphasize on the constraints resulting for SUSY R-parity violating parameters.
The paper has been withdrawn by the authors for modification.
We consider the neutrino oscillations within the minimal supersymmetric standard model with R-parity violation. The Super-Kamiokande atmospheric neutrino data are used to set limits on the bilinear R-parity violating terms. These very stringent limits are out of reach of the other experiments at present and in the near future.
We examine the pion realization of the short ranged supersymmetric (SUSY) mechanism of neutrinoless double beta decay. It originates from the R-parity violating quark-lepton interactions of the SUSY extensions of the standard model of the electroweak interactions. We argue that pions are dominant SUSY mediators in neutrinoless double beta decay. The corresponding nuclear matrix elements for various isotopes are calculated within the proton-neutron renormalized quasiparticle random phase approximation. We define those isotopes which are most sensitive to the SUSY signal and outlook the present experimental situation with the double beta decay searches for the SUSY. Upper limits on the R-parity violating 1st generation Yukawa coupling are derived from various double beta decay experiments.
We discuss some phenomenological issues of the effective quark-lepton operators emerging from the bilinear lepton-Higgs couplings in the superpotential and in the soft supersymmetry (SUSY) breaking sector of the supersymmetric models without R-parity. The contribution of these operators to the neutrinoless double beta decay is derived. The corresponding nuclear matrix elements are calculated within the renormalized quasiparticle random phase approximation, which includes the Pauli effect of fermion pairs and does not collapse for the physical values of the nuclear force strength. On this basis we extract from the experimental data new stringent limits on the 1st generation mass parameter characterized the lepton-Higgs bilinear coupling and on the electron sneutrino vacuum expectation value.
We examine the pion exchange mode of neutrinoless double beta decay induced by the R-parity violating quark-lepton operators of the supersymmetric (SUSY) extensions of the standard model of the electroweak interactions. The corresponding nuclear matrix elements are evaluated within the renormalized quasiparticle random phase approximation with proton-neutron pairing, which includes the Pauli effect of fermion pairs and does not collapse for a physical value of the nuclear force strength. It is argued that the pion-exchange mode of neutrinoless double beta decay dominates over the conventional two-nucleon mode in the case of the SUSY mechanism. As a result sensitivity of neutrinoless double beta decay to the SUSY contribution turns out to be significantly better that previously expected from the two-nucleon mode calculations. An upper limit on the R-parity violating coupling $λ'_{111}$ is derived from non-observation of neutrinoless double beta decay. This limit is much stronger than that expected from the near future accelerator experiments.
We present a new contribution of the R-parity violating supersymmetry (SUSY) to neutrinoless double beta decay via the pion exchange between decaying neutrons. The pion coupling to the final state electrons is induced by the R-parity violating SUSY interactions. We have found this pion-exchange mechanism to dominate over the conventional two-nucleon one. The latter corresponds to direct interaction between quarks from two decaying neutrons without any light hadronic mediator like pion. The constraints on the certain R-parity violating SUSY parameters are extracted from the current experimental neutrinoless double beta decay half-life limit. These constraints are significantly stronger than those previously known or expected from the ongoing accelerator experiments.