arXiv subjects

A. K. Likhoded

Publications and source records attributed to A. K. Likhoded.

102 records · Page 6Linked to original sources

arXiv1996

Hadronic production of S- and P-wave states of (b-bar c)-quarkonium

In the leading $O(α_s^4)$ order of the perturbative QCD, the hadronic production cross-sections of $S$- and $P$-wave states of $B_c$ meson are calculated. The results for the $S$-wave levels are compared with the values given in other papers as well as in the model of the $b$ quark fragmenatation into $B_c$. In the given order, the cross-sections of the hadronic production of the $P$-wave states are calculated for the first time. Their contribution into the $B_c$ meson production is less than 10\%. There is a strong difference between the predictions of the fragmentation model and the exact perturbative calculations. These difeerences are discussed in details for the differential distributions over various kinematical quantities.

hep-ph↗

arXiv1995

Some Features of the Hadronic $B_c^{(*)}$-meson Production at Large $p_T$

Calculations of the hadronic $B^{(*)}_c$-mesons production performed in the framework of the perturbative QCD taking into account $O(α_s^4)$ Feynmann diagrams are presented. A comparison of the exact calculations with those based on the fragmentation model of $\bar b\rightarrow B^{(*)}_c+X$ shows the large discrepancy between them. The exact calculations of the $B^{(*)}_c$-mesons production cross-sections as the function of $p_T$ at the energy of the FNAL Tevatron ($\sqrt{s}=1.8$ TeV) are given. The predicted ratio of the vector to the pseudoscalar state cross-sections is about $R\sim 3$ instead of $R\sim 1.4$ for the fragmentation model.

hep-ph↗

arXiv1995

Photonic production of P-wave states of B_c mesons

Numerical calculations for the production of $P$-wave levels of $B_c$ quarkonium in $γγ$ collisions are performed in the leading $O(α_s^2α_{em}^2)$ order of perturbation theory. The total cross-section of $P$-wave state production is about 10 \% of that for the $S$-wave levels. The contribution of fragmentation component ($6+6$ diagrams) is low, and the basic contribution is determined by the recombination mechanism ($8$ Feynman diagrams). The gauge invariant term of the $\bar b\to B_c$ fragmentation ($6$ diagrams) quite accurately reproduces the result of the fragmentation model, whereas there is a strong deviation of the $c\to B_c$ fragmentation term from the predictions of the fragmentation model.

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arXiv1995

Hadronic production of baryons, containing two heavy quarks

In the framework of QCD perturbation theory, total and differential cross sections of the $Ξ_{bc}'$, $Ξ_{bc}^{(*)}$ and $Ξ_{cc}^{(*)}$ baryons production in gluon collisions are calculated in the leading order over $α_s$ for the doubly heavy ($b c$) and ($ c c$) diquarks. At both small and large transverse momenta of the baryons, a use of the mechanism of the heavy quark fragmentation into the heavy diquark is shown to underestimate the cross section values in comparison with the exact numerical calculations of complete set of diagrams. The expected in Tevatron experiments yield of baryons with two heavy quarks is evaluated as $(1.3\pm 0.3) \cdot 10^5 \,\, bcq$-baryons and $(1.6\pm 0.3) \cdot 10^4 \,\, ccq$-baryons at $p_T>5$ GeV and $|y|<1$ of the baryon momentum and rapidity cuts, with account for the antiparticle yields.

hep-ph↗

arXiv1995

Physics of B_c mesons

In the framework of potential models for heavy quarkonium the mass spectrum for the system ($\bar b c$) is considered. Spin-dependent splittings, taking into account a change of a constant for effective coulomb interaction between the quarks, and widths of radiative transitions between the ($\bar b c$) levels are calculated. In the framework of QCD sum rules, masses of the lightest vector $B_c^*$ and pseudoscalar $B_c$ states are estimated, scaling relation for leptonic constants of heavy quarkonia is derived, and the leptonic constant $f_{B_c}$ is evaluated. The $B_c$ decays are considered in the framework of both the potential models and the QCD sum rules, where the significance of Coulomb-like corrections is shown. The relations, following from the approximate spin symmetry for the heavy quarks in the heavy quarkonium, are analysed for the form factors of the semileptonic weak exclusive decays of $B_c$. The $B_c$ lifetime is evaluated with the account of the corrections to the spectator mechanism of the decay, because of the quark binding into the meson. The total and differential cross sections of the $B_c$ production in different interactions are calculated. The analytic expressions for the fragmentational production cross sections of $B_c$ are derived. The possibility of the practical $B_c$ search in the current and future experiments at electron-positron and hadron colliders is analysed.

hep-ph↗

arXiv1994

Double charmed baryon production at B-factory

The cross-section for the double charmed baryon production at a $B$-factory is estimated on the basis of the perturbative QCD calculations for the $c c$-diquark production as well as of the quark-hadron duality.

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arXiv1994

Photonic production of B_c-mesons

The cross section of the $γγ\rightarrow B_c(B_c^*) \bar b c $ process is calculated. It is shown that near threshold the pseudoscalar state production is much suppressed with respect to the vector one. At large energies their ratio becaims $σ(B_c^*)/sigma(B_c)\sim 4$. The process of heavy quark recombination dominates in the production of $B_c(B_c^*)$ states. The fragmentation process $b\to B_c$ comes to play at high $p_t$ values only, while its contribution will remain nondominant.

hep-ph↗

arXiv1994

Hadronic production of B_c-mesons

On the basis of the exact formulas of QCD perturbation theory and parton model the hadronic production cross-sections for $B_c({B_c}^*)$-mesons ($1^1S_0,1^3S_1,2^1S_0,2^3S_1$-states) are calculated. The method used is the direct calculation of appropriate amplitudes with the help of a FORTRAN program and subsequent Monte-Carlo integration over the phase space and convolution with the structure functions.

hep-ph↗

arXiv1994

$B_c$ spectroscopy

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arXiv1994

Model for anomalous $Υ'' \to Υππ$ transition with account of chiral phase shift in hadron bag of quarkonium

We assume that a rather large bag of the $Υ''(3S b\bar b)$ heavy quarkonium is in the phase of spontaneously broken chiral symmetry, in contrast to the $Υ(1S b \bar b)$ hadron bag, having small size and being in the phase of exact chiral symmetry, so that the shift of the phases in the $Υ'' \to Υππ$ transition is the additional source for the $ππ$ pairs. This source causes an anomalous $ππ$ invariant mass distribution, which is experimentally observed.

hep-ph↗

arXiv1994

Production of four heavy quarks and $B_c$-mesons at the $Z^0$-boson pole

The cross-section for the production of $b{\bar b} c{\bar c}$ quarks in $e^+e^-$ annihilation, that proves to be at a level of $σ(e^+e^- \rightarrow b{\bar b} c{\bar c})/ σ(e^+e^- \rightarrow b{\bar b}) \sim 10^{-2}$ for ${\sqrt s}=M_Z$ is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of $1S$- and $2S$-wave states of $B_c$-meson in the reaction $e^+e^- \rightarrow B_c b{\bar c}$ were calculated in the nonrelativistic model of a heavy quarkonium. The fragmentation function of $b\to B_c^{(*)}$ is analysed in the scaling limit. The number of $Λ_{bc}$-hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality.

hep-ph↗

arXiv1993

$B_c$ Physics at Hadron Colliders

In this paper we summarize the results of the theory working group dedicated to the analysis of $B_c$ production at hadron colliders.

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