arXiv subjects

S. Demidov

Publications and source records attributed to S. Demidov.

5 recordsLinked to original sources

arXiv2023

Numerical study of multiparticle production in $λϕ^4$ theory

We study multiparticle production in the unbroken $(3+1)$-dimensional $λϕ^4$ theory using the semiclassical method of singular solutions. We show that the probabilities of these processes are exponentially suppressed in terms of a small coupling constant $λ\ll 1$ if the multiplicity of the final state is large: $n \gg 1$. At $ n \ll λ^{-1}$ the probabilities agree with well-known perturbative results. At $ n \gg λ^{-1}$ they are dominated by loop effects and decrease exponentially with $n$, as we show for the first time.

hep-ph↗

arXiv2022

Gravitational waves from first-order electroweak phase transition in a model with light sgoldstinos

We study previously unexplored possibility of triggering the first order electroweak phase transition (EWPT) by interactions of the Standard Model (SM) particles with the sector responsible for low scale supersymmetry breaking. The low-energy theory apart from the SM particles contains additional scalar degrees of freedom -- sgoldstinos -- which contribute to the effective scalar potential and thus can trigger the first order EWPT. Remarkably, the latter requires only moderate couplings in the scalar sector. The perturbative description in terms of the effective theory seems formally to be applicable upto the scale of supersymmetry breaking: the Landau pole in the scalar sector is above $10^8$-$10^9$ GeV. We calculate the gravitational wave signal generated at this transition (it can be tested, e.g. by LISA, BBO and DECIGO) and briefly discuss the collider phenomenology of this scenario.

hep-ph↗

arXiv2021

Lunar neutrinos

Cosmic rays bombard the lunar surface producing mesons, which attenuate inside the regolith. They get slower and decay weakly into mostly sub-GeV neutrinos leaving the surface. Thus the Moon shines in neutrinos. Here we calculate spectra of low energy neutrinos, which exhibit bright features potentially recognisable above isotropic neutrino background in the direction towards the Moon. Their observation, though a very challenging task for future neutrino large volume experiments, would make the Moon the nearest astrophysical source for which the concept of multimessenger astronomy works truly. Remarkably, some features of the lunar neutrino flux are sensitive to the surface mass density of the Moon.

hep-ph↗

arXiv2020

Sgoldstino signature in $hh$, $W^+W^-$ and $ZZ$ spectra at the LHC

In a supersymmetric extension of the Standard Model of particle physics (SM) with low scale of supersymmetry breaking, sgoldstino of (sub)TeV mass can be observed at the Large Hadron Collider (LHC) as a peak in diboson mass spectra. Moreover, as a singlet with respect to the SM gauge group, scalar sgoldstino can mix with the SM-like Higgs boson and interfere in all neutral channels providing with the promising signatures of new physics if superpartners are heavy. Sgoldstino couplings to the SM particles are determined by the pattern of soft supersymmetry breaking parameters. Here we concentrate on the cases with a noticeable sgoldstino contribution to di-Higgs channel. Having found a phenomenologically viable region in the model parameter space where scalar sgoldstino, produced at the LHC in gluon fusion, decays into a pair of the lightest Higgs boson we give predictions for corresponding cross section. Using the results of the LHC searches for scalar resonances we place bounds on the supersymmetry breaking scale $\sqrt{F}$ in this region of parameter space. Remarkably, in this region sgoldstino may also be observed in $W^+W^-$ and $ZZ$ channels, yielding independent signatures, since their signal strengths are related to that of di-Higgs channel.

hep-ph↗

arXiv2019

Light hidden photon production in high energy collisions

The visible and dark sectors of particle physics can be connected via kinetic mixing between ordinary and hidden photons. If the latter is light its production in high energy collisions of ordinary particles proceeds via oscillations with ordinary photons similarly to the neutrino processes. Generically, the experiments are insensitive to mass of the hidden vector, if it is lighter than 1\,MeV, and it does not decay into $e^+e^-$-pair. Still, one can use the missing energy and scattering off the detector material as signatures to search for the light vectors. Presence of media suppresses production of the light vectors making the experiments insensitive to the entire model. We present analytic formulas for the light hidden photon production, propagation and detection valid for searches at colliders and beam-target experiments and apply them to estimate the impact on the sensitivities of a set of experiments --- NA64, FASER, MATHUSLA, SHiP, T2K, DUNE, NA62 --- in a zero-background case.

hep-ph↗