arXiv subjects

Alexey S. Zhevlakov

Publications and source records attributed to Alexey S. Zhevlakov.

22 records · Page 2Linked to original sources

arXiv2020

Deuteron EDM induced by CP violating couplings of pseudoscalar mesons

We analyze contributions to the electric dipole (EDM) and Schiff (SFM) moments of deuteron induced by the CP-violating three-pseudoscalar meson couplings using phenomenological Lagrangian approach involving nucleons and pseudoscalar mesons $P=π, K, η, η'$. Deuteron is considered as a proton-neutron bound state and its properties are defined by one- and two-body forces. One-body forces correspond to a picture there proton and neutron are quasi free constituents of deuteron and their contribution to the deuteron EDM (dEDM) is simply the sum of proton and neutron EDMs. Two-body forces in deuteron are induced by one-meson exchange between nucleons. They produce a contribution to the dEDM, which is estimated using corresponding potential approach. From numerical analysis of nucleon and deuteron EDMs we derive stringent limits on CP-violating hadronic couplings and $\barθ$ parameter. We showed that proposed measurements of proton and deuteron EDMs at level of $\sim 10^{-29}$ by the Store Ring EDM and JEDI Collaborations will provide more stringent upper limits on the CP violating parameters.

hep-ph↗

arXiv2019

Updated limits on the CP violating $ηππ$ and $η'ππ$ couplings derived from the neutron EDM

We complete our derivation of upper limits on the CP violating $ηππ$ and $η'ππ$ couplings from an analysis of their two-loop contributions to the neutron electric dipole moment (nEDM). We use a phenomenological Lagrangian approach which is formulated in terms of hadronic degrees of freedom - nucleons and pseudoscalar mesons. The essential part of the Lagrangian contains the CP violating couplings between $η(η')$ and pions. Previously, we included photons using minimal substitution in case of the proton and charged pions. Now we extend our Lagrangian by adding the nonminimal couplings, i.e. anomalous magnetic couplings of nucleons with the photon. The obtained numerical upper limits for the $ηππ$ and $η'ππ$ couplings $|f_{ηππ}(M_η^2)|<4.4 \times10^{-11}$ and $|f_{η^\primeππ}(M_{η'}^2)|<3.8 \times10^{-11}$ can be useful for the related, planned experiments at the JLab Eta Factory. Using present experimental limits on the nEDM, we derive upper limits on the CP violating $\barθ$ parameter of $\bar{\mathrmθ}<4.7 \times 10^{-10}$.

hep-ph↗

arXiv2018

Bounds on rare decays of $η$ and $η^\prime$ mesons from the neutron EDM

We provide model-independent bounds on the rates of rare decays $η(η^\prime) \to ππ$ based on experimental limits on the neutron electric dipole moment (nEDM). Starting from phenomenological $η(η^\prime) ππ$ couplings, the nEDM arises at two loop level. The leading-order relativistic ChPT calculation with the minimal photon coupling to charged pions and a proton inside the loops leads to a finite, counter term-free result. This is an improvement upon previous estimates which used approximations in evaluating the two loop contribution and were plagued by divergences. While constraints on the $η(η^\prime) ππ$ couplings in our phenomenological approach are somewhat milder than in the picture with the QCD $θ$-term, our calculation means that whatever the origin of these couplings, The decays $η(η') \to 2 π$ will remain unobservable in the near future.

hep-ph↗

arXiv2018

Deep inelastic $e-τ$ and $μ-τ$ conversion in the NA64 experiment at the CERN SPS

We study the Lepton Flavor Violating (LFV) $e(μ)-τ$ conversion in Deep Inelastic Scattering (DIS) of electron (muon) on fixed-target nuclei. Our model-independent analysis is based on the set of the low-energy effective four-fermion LFV operators composed of leptons and quarks with the corresponding mass scales $Λ_{k}$ for each operator. Using the estimated sensitivity of the search for this LFV process in events with large missing energy in the NA64 experiment at the CERN SPS, we derive lower limits for $Λ_{k}$ and compared them with the corresponding limits existing in the literature. We show that the DIS $e(μ)-τ$ conversion is able to provide a plenty of new limits as yet non-existing in the literature. We also analyzed the energy spectrum of the final-state $τ$ and discussed viability of the observation of this process in the NA64 experiment and ones akin to it. The case of polarized beams and targets is also discussed.

hep-ph↗