arXiv subjects
Publications and source records attributed to A. K. Likhoded.
We present a heavy quark fragmentation mechanism based on a modified version of the standard model of quark fragmentation, taking into account peculiarities of the Regge trajectories of quarkonia containing heavy quarks. The modified model describes the experimental data more satisfactorily both for meson and baryon production.
Rare decays of the Higgs boson into quarkonia-pairs are studied within the framework of NRQCD approach. The main decay mechanisms and their interference are studied in detail. One-loop corrections to the widths of these decays are taken into account for the first time.
Various models of tetraquark generation in the reaction $K^{+} p \rightarrow T (us; \bar{s}\bar{s})X$ are considered. The predictions for corresponding inclusive spectra were evaluated at the energy 32 and 250 GeV.
The hadronic production of $D$-wave states of $\bar b c$ is studied. The relative yield of such states is estimated for kinematic conditions of LHC experiments.
The cross section values of $J/ψ η_c$ and $J/ψ J/ψ$ production in $e^+e^-$ annihilation are estimated within one-loop approximation near $Z$ pole, as well as at higher energies. Both intermediate bosons, $γ$ and $Z$, are taken into account. It is shown that at $Z$ mass the NLO contribution increases the cross-section values by 3.5 times.
The exclusive decays of the Higgs boson to $B_c B_c$ and $B_c^\ast B_c^\ast$ pairs are studied. The hard parts of the decay amplitudes are estimated within the perturbative Standard Model up to one-loop corrections. The soft fusion of heavy quarks to the quarkonium is described in framework of the relativistic quark model.
Exclusive decays of the $Ξ_{bc}^+$ with light mesons production, $Ξ_{bc}^+\toΞ_{cc}^{++}\mathcal{R}$ are analyzed. In the framework of the factorization model the matrix elements of the considered reactions are written as a product of $Ξ_{bc}\toΞ_{cc}W$ and $W\to\mathcal{R}$ transition amplitudes. As a result theoretical and experimental investigation of these decays allow us to test the physics of heavy and light quarks' sectors. Presented are the branching fractions of these reactions, as well as the distributions over the invariant mass of the light system and some other kinematical variables. Our calculations show that the probabilities of the considered reactions are high enough, so presented results could help with observation of yet unseen $Ξ_{bc}$ baryon.
In the framework of diquark model for production we discuss the yields and observation prospects for excited states of doubly heavy baryons at LHC kinematic conditions.
The $2S$ $B_c$ states observed by ATLAS, CMS and LHCb Collaborations are discussed. The observation perspectives of $B_c^*$, $2P$ wave, $3P$ wave and $D$ wave states of $B_c$ at LHC experiments are estimated.
The yield of doubly charmed baryons with excited heavy diquark in $S$ wave and $P$ wave states has been estimated at LHC energies. The observation possibility of such baryons is discussed.
The theoretical analysis of production, lifetime, and decays of doubly heavy baryons is presented. The lifetime of $Ξ_{cc}^{++}$ baryon recently measured by the LHCb Collaboration is used to estimate the lifetimes of other doubly heavy baryons. The production and the possibility of observation of $Ξ_{bc}$ baryon at LHC are discussed.
This article is devoted to systematic analysis of double charmonium production in exclusive $Z$ boson decays in the framework of Nonrelativistic Quantum Chromodynamic (NRQCD) and leading twist light-cone (LC) models. Theoretical predictions for branching fractions of all considered decays are presented. According to obtained results in the case of allowed by helicity suppression rule processes the effect of internal quark motion increases the branching fraction by a factor 1.5, while for forbidden reactions LC predictions are strictly zero, while NRQCD ones are significantly smaller than for allowed.
The finite size of doubly heavy diquark gives a positive correction to the masses of baryons calculated in the local diquark approximation. We evaluate this correction for the basic states of doubly charmed baryons to give quite accurate predictions actual for current searches of those baryons at LHCb: $m[{Ξ_{cc}^{1/2}}^{+}]\approx m[{Ξ_{cc}^{1/2}}^{++}]=3615\pm 55$ MeV and $m[{Ξ_{cc}^{3/2}}^{+}]\approx m[{Ξ_{cc}^{3/2}}^{++}]=3747\pm 55$ MeV.
Recent LHCb measurements of the $J/ψ$ meson production in jets is analyzed using fragmentation jet function formalism. It is shown that disagreement with theoretical predictions for distribution over the fraction of $J/ψ$ transverse momentum $z(J/ψ)$ in the cases of prompt production can be explained if one takes into account evolution of the fragmentation function and contributions from double parton scattering mechanism.
We present theoretical analysis of paired $B_c$ mesons production in $e^+e^-$ annihilation at different energy scales taking into account full next-to-leading order QCD corrections. Both possible electroweak channels are considered: production via virtual photon and via virtual $Z$-boson. We study in detail the role of radiative QCD corrections, which were found to be significant especially at low energies. It is shown that the contribution from $Z$-boson is significant at high energies ($\sqrt{s} > M_Z/2$) especially in the case of paired production of pseudo-scalar and vector ($B_c + B_c^*$) mesons. Azimuthal asymmetry induced by a $P$-violating weak interaction with $Z$-boson is also analyzed.
In the present work we study production of $J/ψ+ χ_c$ and $J/ψ+ J/ψ$ in LHC. The first process is forbidden at the leading order in gluon fusion due to the $C$-parity conservation, and the first non-vanishing contribution is given by the process with additional emission of real gluon. Considering the direct production of $J/ψ+ J/ψ$, where the leading order is allowed, we have found that the contribution from the higher order process with real gluon emission is comparable and even more significant than the leading order. Moreover, account of this higher order effect dramatically changes kinematical distributions. Through the present paper we study in details different channels of paired $J/ψ+ J/ψ$ production: direct $J/ψ+ J/ψ$ production, feed-down from $J/ψ+ χ_c$ channel, double parton scattering. We also try to find kinematical distributions that are most suitable to separate these different channels.
In the present paper we study the production of $χ_b + c\bar c$ at the LHC within single parton scattering approach. A special attention payed to the feed-down from $χ_b$ states to the associated $Υ+ c\bar c$ production, which was recently studied by the LHCb. We have found that this feed-down is about percents of the total cross section seen in the experiment. It is shown that the shapes of the differential distributions are almost same as found by the LHCb except the azimuthal asymmetry, which is almost flat in the experiment. We conclude that the precise study of the single parton scattering contributions is necessary for the correct isolation of other possible production channels such as double parton scattering.
Involving of elastic rescattering and annihilation of quark-antiquark pairs in a final state allows us to explain a dependence of ratio for cross sections of $η'$ and $η$ mesons versus transfer momentum in charge exchange reactions. We estimate the mixing angle of mesons with isoscalar states of $\bar u u+\bar d d$ and $\bar s s$ of hidden strangeness. The evaluation includes the consistent description of yield ratio for $η'$ and $η$ mesons in decays of $B^0$, $B^0_s$ and $J/ψ$ mesons.