arXiv subjects

S. G. Salnikov

Publications and source records attributed to S. G. Salnikov.

At least 19 recordsLinked to original sources

arXiv2026

Near-threshold resonances in $e^+e^-$ annihilation

Near-threshold resonances have been discovered in many hadron pair production processes, resulting in a significant increase in reaction cross sections at low relative velocities of the produced particles. The natural cause of such resonances is the interaction between slow hadrons in the final state. Our review demonstrates that, in virtually all known cases, final-state interactions successfully explain the results of numerous experiments demonstrating a nontrivial energy dependence of cross sections for processes near reaction thresholds. A comprehensive study of near-threshold resonances in various processes can provide new information about the interaction between hadrons at large distances.

hep-ph↗

arXiv2026

Charge asymmetry in $e^{+}e^{-}\to B^{()}\bar{B}^{()}$ processes in the vicinity of $Υ(4S)$

The effects of isotopic invariance violation in the processes $e^{+}e^{-}\to B\bar{B}$, $e^{+}e^{-}\to B^{*}\bar{B}$, and $e^{+}e^{-}\to B^{*}\bar{B}^{*}$ are considered in the energy range between the thresholds of $B^{+}B^{-}$ and $B_{s}^{0}\bar{B}_{s}^{0}$ production. The analysis is based on taking into account the final-state interaction in a six-channel problem. Our approach allowed us to obtain good agreement with recent Belle-II results for the ratio of the $B^{0}\bar{B}^{0}$ and $B^{+}B^{-}$ production cross sections in $e^{+}e^{-}$ annihilation in the vicinity of $Υ(4S)$. It is shown that at higher energies the ratios of the cross sections for pairs of neutral and charged $B^{(*)}$ mesons can differ significantly from unity. A detailed measurement of this effect will provide evidence that the nontrivial energy dependence of the $B^{(*)}\bar{B}^{(*)}$ production cross sections is a consequence of interference of the particle production amplitudes in the multichannel problem.

hep-ph↗

arXiv2024

Production of $D^{()}\bar{D}^{()}$ near the thresholds in $e^{+}e^{-}$ annihilation

It is shown that the nontrivial energy dependencies of $D\bar{D}$, $D\bar{D}^{*}$, and $D^{*}\bar{D}^{*}$ pair production cross sections in $e^{+}e^{- }$ annihilation are well described within the approach based on account for the final-state interaction of produced particles. This statement is valid for production of charged and neutral particles. Interaction of $D^{(*)}$ and $\bar{D}^{(*)}$ is taken into account using the effective potential method. Its applicability is based on the fact that for near-threshold resonance the characteristic width of peak in the wave function is much larger than the interaction radius. The transition amplitudes between all three channels play an important role in the description of cross sections. These transitions are possible since all channels have the same quantum numbers $J^{PC}=1^{--}$.

hep-ph↗

arXiv2023

Meson production in $J/ψ$ decays and $J/ψ\to N\bar{N}γ$ process

It is shown that an account for the final-state interaction of real or virtual nucleon and antinucleon produced in the processes $J/ψ\to p\bar{p}γ$, $ψ(2S)\to p\bar{p}γ$, $J/ψ\to p\bar{p}ω$, and $J/ψ\to3\left(π^{+}π^{-}\right)γ$ near the threshold of $N\bar{N}$ pair production allows one to obtain self-consistent description of these processes. Predictions of our model are in good agreement with experimental data available. The proposed potential model also reproduces the corresponding partial cross sections of $p\bar{p}$ scattering.

hep-ph↗

arXiv2023

Near-threshold resonance in $e^{+}e^{-}\rightarrowΛ_{c}\barΛ_{c}$ process

We discuss the influence of various contributions of the $Λ_{c}\barΛ_{c}$ potential on the energy dependence of the cross section $e^{+}e^{-}\rightarrowΛ_{c}\barΛ_{c}$ near the threshold. New BESIII experimental data on the cross section and electromagnetic form factors $G_{E}$ and $G_{M}$ are taken into account. Our predictions are in good agreement with experimental data. We predict a bound state of $Λ_{c}\barΛ_{c}$ at energy $\sim 38~\textrm{MeV}$ below the threshold that may manifest itself in anomalous behavior of light meson production cross sections in a given energy region.

hep-ph↗

arXiv2023

Coupled channels and production of near-threshold $B^{()}\bar{B}^{()}$ resonances in $e^{+}e^{-}$ annihilation

The effects of final-state interaction of hadrons, produced in $e^{+}e^{-}$ annihilation near the threshold, are discussed. If there is a loosely bound state or a virtual state in a system of produced hadrons, then the energy dependence of hadroproduction cross section is very strong. Our approach is based on the use of the effective potentials accounting for the interaction between hadrons in the final state. The cases of a few channels with nonzero transition amplitudes between them are considered. It is shown that these transitions drastically change the energy dependence of the cross sections. In particular, a narrow resonance below the threshold in one channel leads to a broad peak in another channel. We explained the non-trivial energy dependence of the production cross sections of $B\bar{B}$, $B^{*}\bar{B}$, $B\bar{B}^{*}$, $B^{*}\bar{B}^{*}$ near the thresholds in $e^{+}e^{-}$ annihilation and obtained good agreement between our predictions and the experimental data available.

hep-ph↗

arXiv2023

Natural explanation of recent results on $e^{+}e^{-}\toΛ\barΛ$

We show that the recent experimental data on the cross section of the process $e^{+}e^{-}\toΛ\barΛ$ near the threshold can be perfectly explained by the final-state interaction of $Λ$ and $\barΛ$. The enhancement of the cross section is related to the existence of low-energy real or virtual state in the corresponding potential. We present a simple analytical formula that fits the experimental data very well.

hep-ph↗

arXiv2022

$N\bar{N}$ production in $e^{+}e^{-}$ annihilation near the threshold revisited

Production of $p\bar{p}$ and $n\bar{n}$ pairs in $e^{+}e^{-}$ annihilation near the threshold of the process is discussed with account for the new experimental data appeared recently. Since a significant part of these new data was obtained at energies noticeably exceeding the threshold, we also take into account the form factor describing the amplitude of $N\bar{N}$ pair production at small distances. The effective optical potential, which describes a sharp dependence of the $N\bar{N}$ production cross sections near the threshold, consists of the central potential for $S$ and $D$ waves and the tensor potential. These potentials differ for the states with isospin $I=0$ and $I=1$ of $N\bar{N}$ pair. The optical potential describes well $N\bar{N}$ scattering phases, the cross sections of $p\bar{p}$ and $n\bar{n}$ production in $e^{+}e^{-}$ annihilation near the threshold, the electromagnetic form factors $G_{E}$ and $G_{M}$ for protons and neutrons, as well as the cross sections of the processes $e^{+}e^{-}\to6π$ and $e^{+}e^{-}\to K^{+}K^{-}π^{+}π^{-}$.

hep-ph↗

arXiv2022

Bremsstrahlung on noble gases at low energies

A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argon and xenon is carried out. It is shown that the approximate formulas widely used for the description of bremsstrahlung spectra lead to predictions that significantly differ from the exact results. In the limit when the photon frequency tends to zero, a rigorous proof of the relationship between the spectrum of the bremsstrahlung with a transport cross section of electron scattering on an atom is given. This proof does not require any assumptions about the dependence of the scattering phases on energy. For electron energies lower than the luminescence threshold, it is shown that the predictions for a number of radiated photons obtained by the exact formula are in good agreement with the available experimental data.

physics.atom-ph↗

arXiv2022

Effects of isospin violation in the $e^+e^- \rightarrow B^{()}\bar B^{()}$ cross sections

Model estimates are obtained for the influence of Coulomb effects on the ratio of the cross sections for the production of charged and neutral $B\bar B$ and $B^*\bar B^*$ pairs in $e^+e^-$ annihilation. It is shown that the difference between the masses of charged and neutral mesons obtained under the assumption that this ratio is constant on a scale of the order of the beam energy spread can differ from the true one by $δM \sim 0.03\,\mbox{MeV}$ at the energy of $Υ(5S)$ and by $δM \sim 0.4\,\mbox{MeV}$ at the energy of $Υ(4S)$. Thus, the errors given in the PDG for the difference between the masses of charged and neutral $B$ mesons, based on the results obtained at the energy of $Υ(4S)$, are strongly underestimated. Similar measurements at the energy of $Υ(5S)$ will have an order of magnitude smaller systematic shift for the mass difference. This circumstance should be taken into account when planning future experiments at the $B$ factory in KEK.

hep-ph↗

arXiv2022

Final-state interaction in the process $e^{+}e^{-}\rightarrowΛ_{c}\barΛ_{c}$

We show that the final-state interaction explains the nontrivial near-threshold energy dependence of the cross section of the process $e^{+}e^{-}\rightarrowΛ_{c}\barΛ_{c}$ observed by the Belle and BESIII collaborations. This energy dependence is the result of the mixture of $S$-wave and $D$-wave components of the $Λ_{c}\barΛ_{c}$ wave function due to a tensor interaction. The Coulomb potential is important only in the narrow energy region about a few MeV above the threshold of the process. It is shown that the widely used assumption that the impact of the Coulomb interaction on the cross sections of hadron production is reduced to the Sommerfeld-Gamow-Sakharov factor is not correct.

hep-ph↗

arXiv2021

Invariant-mass spectrum of $Λ\barΛ$ pair in the process $e^+e^-\rightarrowϕΛ\barΛ$

We show that the final-state interaction perfectly explains the recent experimental data of BESIII Collaboration on the near-threshold invariant-mass spectrum of $Λ\barΛ$ in the process $e^+e^-\rightarrowϕΛ\barΛ$. The position of peak in invariant-mass spectrum is above the threshold though the interaction of $Λ$ and $\barΛ$ is due to an attractive potential. This potential has a simple form and depends only on two parameters. We show that the invariant-mass spectrum is consistent with the quantum numbers $J^{PC}=1^{++}$ and $2^{++}$ of $Λ\barΛ$ pair but contradicts to $J^{PC}=2^{-+}$.

hep-ph↗

arXiv2021

Coulomb effects in the decays $Υ(4S) \rightarrow B\bar B$

A simple exactly solvable model is proposed for describing the decays $Υ(4S) \rightarrow B^0\bar B^0$ and $Υ(4S) \rightarrow B^+B^-$. Our predictions agree with available experimental data. Using this model, we analyze the Coulomb effects in the spectra of these decays. It is shown that the frequently used assumption of factorization of Coulomb effects is not fulfilled. The Coulomb interaction leads to the difference in the positions and heights of the peaks corresponding to the charged and neutral modes. As a result, the ratio of probability of $Υ(4S)\rightarrow B^+B^-$ decay and $Υ(4S) \rightarrow B^0\bar B^0$ decay is a nontrivial function of energy.

hep-ph↗

arXiv2021

Possible studies at the first stage of the NICA collider operation with polarized and unpolarized proton and deuteron beams

This paper contains suggestions for experiments with usage of the Spin Physics Detector (SPD) at the first stage of the SPD NICA Programme developing at JINR. Double polarized pp-, dd- and pd- collisions at c.m.s. NN energies of 3.4-10 GeV, which will be accessible at the initial stage of experiments, allow one to study spin dependence of the NN interaction, search for multiquark states at double strangeness, charm and beauty thresholds, study the short-range structure of the deuteron. Double polarized pd scattering offer a possibility to test the Standard Model through the search for T-invariance violation.

hep-ph↗

arXiv2020

Parity violation in proton-deuteron scattering

The effects of parity violation in the interaction of relativistic polarized protons and deuterons are discussed. Within Glauber's approach, estimates are obtained for P-odd asymmetries in the total and elastic scattering cross sections, in the deuteron dissociation cross section, and in the inelastic cross section with meson production in a final state. It is shown that, from the point of view of the magnitude of the P-odd effects, the interaction of polarized deuterons with unpolarized protons has an advantage over the interaction of polarized protons with unpolarized deuterons. A significant P-odd asymmetry was found in the dissociation channel of the polarized deuteron.

hep-ph↗

arXiv2020

Parity violation in high-energy proton-proton scattering

A new approach is proposed to describe the parity violation in the process of scattering of a polarized proton by a proton at high energies. It is shown that in the tree approximation the P-odd amplitude of proton-proton scattering is substantially smaller than the P-odd amplitude in proton-neutron scattering. The main source of P-odd asymmetry in proton-proton scattering is radiative corrections due to the charge-exchange strong interaction. We predict that the asymmetry in the inelastic cross section is substantially less than the asymmetry in the elastic cross section.

hep-ph↗

arXiv2019

Possibility to investigate P-parity violation in nuclear collisions at facility NICA

A possible experimental setup for measuring the effect of parity violation in the interaction of the polarized proton or deuteron beams with an unpolarized target is discussed. One possibility is investigation of scattering of the proton or deuteron polarized beams on a thick internal target in one of the rings of the NICA collider. In this case, the spin of a circulating particles is transformed into a mode precessing in the horizontal plane using an RF flipper. The effect of parity violation will be studied by measuring the correlation of the interaction cross section of particles and the direction of their spins. In an alternative approach, the flipper transforms the spins of particles into a horizontal plane and the beam is extracted into the channel in a certain phase of the precession. In this more traditional experimental setup, the total cross section of the passage of particles through a dense target is measured, depending on the sign of the helicity of the polarization of the beam.

hep-ex↗

arXiv2018

Fine structure of the cross sections of $e^{+}e^{-}$ annihilation near the thresholds of $p\bar{p}$ and $n\bar{n}$ production

The energy dependence of the cross sections of $p\bar p$, $n\bar n$, and meson production in $e^+e^-$ annihilation in the vicinity of the $p\bar p$ and $n\bar n$ thresholds is studied. The proton-neutron mass difference and the $p\bar p$ Coulomb interaction are taken into account. The values of the cross sections are very sensitive to the parameters of the optical potential. It is shown that the commonly accepted factorization approach for the account of the Coulomb interaction does not work well enough in the vicinity of the threshold due to the finite size of the optical potential well.

hep-ph↗