arXiv subjects

Yu. Volkotrub

Publications and source records attributed to Yu. Volkotrub.

6 recordsLinked to original sources

arXiv2024

$τ$-lepton pair spin in proton-proton LHC collisions for anomalous dipole moments

The spin correlations in the pair of $τ$ leptons produced in the high-energy proton-proton collisions are studied. The invariant mass of the $τ$-lepton pair is chosen close to $Z$-boson mass, in these conditions $Z$-boson exchange gives the dominant contribution to the Drell-Yan mechanism. The interaction of $Z$ boson with $τ$ lepton, in addition to the Standard Model couplings, can include weak anomalous magnetic and electric dipole moments (or form-factors) of the $τ$ lepton. Dependence of elements of the $pp$ spin-correlation matrix on the weak anomalous moments is determined for various regions of the rapidity of the $τ$-lepton pair. Based on this calculation, we construct a semi-realistic observable built on the momenta of pions in the $τ^\mp \to π^\mp ν_τ$ and $τ^\pm \to ρ^\pm ν_τ\to π^\pm π^0 ν_τ$ decay channels, and show that this observable can be sensitive to the weak anomalous dipole moments.

hep-ph↗

arXiv2022

Correlations among neutron-proton and neutron-deuteron elastic scattering observables

We employ two models of the nucleon-nucleon force: the OPE-Gaussian as well as the chiral N4LO and N4LO+ interactions with semilocal regularization in momentum space to study correlations among two-nucleon and three-nucleon elastic scattering observables. These models contain a number of free parameters whose values and covariance matrices are evaluated from a fit to the two-nucleon data. Such detailed knowledge of parameters allows us to create, using various sets of statistically generated parameters, numerous versions of these potentials and next apply them to two- and three-nucleon scattering to make predictions of various observables at the reaction energies up to 200 MeV. This permits a systematic analysis of correlations among two-nucleon and three-nucleon observables, basing on a relatively big sample of predictions. We found that most observables in neutron-proton and neutron-deuteron systems are uncorrelated, but there are exceptions revealing strong correlations, which depend on the reaction energy and scattering angle. This information may be useful for precise fixing free parameters of two-nucleon and three-nucleon forces and for understanding dependencies and correlations between potential parameters and observables.

nucl-th↗

arXiv2020

Light nuclei with semilocal momentum-space regularized chiral interactions up to third order

We present a systematic investigation of few-nucleon systems and light nuclei using the current LENPIC interactions comprising semilocal momentum-space regularized two- and three-nucleon forces up to third chiral order (N$^2$LO). Following our earlier study utilizing the coordinate-space regularized interactions, the two low-energy constants entering the three-body force are determined from the triton binding energy and the differential cross section minimum in elastic nucleon-deuteron scattering. Predictions are made for selected observables in elastic nucleon-deuteron scattering and in the deuteron breakup reactions, for properties of the $A=3$ and $A=4$ nuclei, and for spectra of $p$-shell nuclei up to $A = 16$. A comprehensive error analysis is performed including an estimation of correlated truncation uncertainties for nuclear spectra. The obtained predictions are generally found to agree with experimental data within errors. Similar to the coordinate-space regularized chiral interactions at the same order, a systematic overbinding of heavier nuclei is observed, which sets in for $A \sim 10$ and increases with $A$.

nucl-th↗

arXiv2020

Uncertainty of three-nucleon continuum observables arising from uncertainties of two-nucleon potential parameters

Propagation of uncertainties from two-nucleon potential parameters to three-nucleon observables, that is statistical errors for the neutron-deuteron elastic scattering and the deuteron breakup reaction at neutron laboratory energies up to 200 MeV is investigated. To that end we use the chiral nucleon-nucleon interaction with the semi-local momentum-space regularization at various orders of the chiral expansion, exploiting knowledge of the covariance matrix of its parameters. For both reactions we compare statistical uncertainties for chiral predictions with the uncertainties obtained in the same way but for the semi-phenomenological One-Pion-Exchange two-nucleon force. In addition for the elastic scattering we show also the truncation errors arising from restriction to a given order of chiral predictions, estimated among others within the Bayesian method, and the cutoff dependence of chiral predictions. We find that the resulting statistical uncertainty is smaller than the truncation errors for the chiral force at lower orders of the chiral expansion. At the higher orders of the chiral expansion and at low energies the statistical errors exceed the truncation ones but at intermediate and higher energies truncation errors are more important. Overall, magnitudes of the theoretical uncertainties are small and amount up to 0.5\%-4\%, depending on the observable and energy. We also find that the magnitudes of statistical uncertainties for the chiral and semi-phenomenological potentials are similar and that the dependence of predictions on the regularization parameter values is important at all investigated energies.

nucl-th↗

arXiv2018

Theoretical uncertainties of the elastic nucleon-deuteron scattering observables

Theoretical uncertainties of various types are discussed for the nucleon-deuteron elastic scattering observables at the incoming nucleon laboratory energies up to 200 MeV. We are especially interested in the statistical errors arising from uncertainties of parameters of a nucleon-nucleon interaction. The obtained uncertainties of the differential cross section and numerous scattering observables are in general small, grow with the reaction energy and amount up to a few percent at 200 MeV. We compare these uncertainties with the other types of theoretical errors like truncation errors, numerical uncertainties and uncertainties arising from using the various models of nuclear interaction. We find the latter ones to be dominant source of uncertainties of modern predictions for the three-nucleon scattering observables. To perform above mentioned studies we use the One-Pion-Exchange Gaussian potential derived by the Granada group, for which the covariance matrix of its parameters is known, and solve the Faddeev equation for the nucleon-deuteron elastic scattering. Thus beside studying theoretical uncertainties we also show a description of the nucleon-deuteron elastic scattering data by the One-Pion-Exchange Gaussian model and compare it with results obtained with other nucleon-nucleon potentials, including chiral N$^4$LO forces from the Bochum-Bonn and Moscow(Idaho)-Salamanca groups. In this way we confirm the usefulness and high quality of the One-Pion-Exchange Gaussian force.

nucl-th↗

arXiv2018

Nucleon-deuteron scattering with the JISP16 potential

The nucleon-nucleon J-matrix Inverse Scattering Potential JISP16 is applied to elastic nucleon-deuteron (Nd) scattering and the deuteron breakup process at the lab. nucleon energies up to 135 MeV. The formalism of the Faddeev equations is used to obtain 3N scattering states. We compare predictions based on the JISP16 force with data and with results based on various NN interactions: the CD Bonn, the AV18, the chiral force with the semi-local regularization at the 5th order of the chiral expansion and with low-momentum interactions obtained from the CD Bonn force as well as with the predictions from the combination of the AV18 NN interaction and the Urbana IX 3N force. JISP16 provides a satisfactory description of some observables at low energies but strong deviations from data as well as from standard and chiral potential predictions with increasing energy. However, there are also polarization observables at low energies for which the JISP16 predictions differ from those based on the other forces by a factor of two. The reason for such a behavior can be traced back to the P-wave components of the JISP16 force. At higher energies the deviations can be enhanced by an interference with higher partial waves and by the properties of the JISP16 deuteron wave function. In addition, we compare the energy and angular dependence of predictions based on the JISP16 force with the results of the low-momentum forces obtained with different values of the momentum cutoff parameter. We found that such low-momentum forces can be employed to interpret the Nd elastic scattering data only below some specific energy which depends on the cutoff parameter. Since JISP16 is defined in a finite oscillator basis, it has properties similar to low momentum interactions and its application to the description of Nd scattering data is limited to a low momentum transfer region.

nucl-th↗