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A. V. Berezhnoy

Publications and source records attributed to A. V. Berezhnoy.

53 records · Page 3Linked to original sources
arXiv2003

The pair production of charmed mesons in the photon-photon interaction

In the framework of the constituent quark model the exclusive pair production of the charmed mesons in the photon-photon interaction is calculated. The comparison of these predictions with the ones of the heavy quark effective theory is performed. It is shown, that the light valence quark of D-meson plays the essential role not only in the hadronization process, but also in the production of the heavy c-quark. Moreover, it is shown, that because of the strong interaction between the initial photon field and the light quark charge the similar situation is kept even in the limit (m_{Q}\to \infty), whence it is concluded, that the application of the heavy quark effective theory in the case of the photon-photon interaction is not valid because it does not take into account one of the dominant mechanisms of the heavy meson production.

hep-ph↗
arXiv2002

The charm contribution into the proton structure function in DIS at the HERA ep-collider

In the framework of perturbative QCD and a model for the production of charmed hadrons the structure function $F^c_2$ is calculated and compared with the experimental data of H1 and ZEUS Collaborations. We show that the spectator mechanism of the $D^*$-meson production independent of a hadronic remnant is valid at $p_T>10$ GeV, only. We find that the evolution of $F^c_2(x,Q^2)$ versus the virtuality $Q^2$ can be neglected in the kinematic region of HERA.

hep-ph↗
arXiv2001

Diffractive charm photoproduction at HERA ep-collider

The cross section of the $D^*$-meson diffractive photoproduction at the HERA collider has been calculated in the framework of perturbatively motivated model for the different kinematic regions. The camparison between the different Pomeron models has been performed.

hep-ph↗
arXiv2000

The contribution of the hadronic component of the photon into the $D^*$-meson photoproduction at HERA

In the framework of the vector dominance model (VDM) new contribution into the cross-section of $D^*$-meson photoproduction at HERA has been estimated. This contribution is due to the interaction of the virtual vector $c\bar c$-mesons from photon with the proton. It has been shown that the mechanism under discussion plays the essential role for all values of transverse momentum of $D^*$-mesons at HERA. Taking into account for the contribution of this mechanism improves the description of the experimental cross section distribution.

hep-ph↗
arXiv2000

Photoproduction and electroproduction of charm at high energies

We estimate the differential and total cross sections for both the photoproduction of vector D*-meson and its yield in deep inelastic scattering at the HERA collider in the framework of model motivated by perturbative calculations in QCD. The offered model allows us to take into account higher twists over the transverse momentum of meson at p_T ~ m_c and to correctly approach the dominance of $c$-quark fragmentation at p_T >> m_c. We consider a possibility for the hadronization of color-octet c q-bar state into the meson. The combined contribution by the singlet and octet-color terms results in a good agreement with the experimental data for both the photoproduction and the production in deep inelastic scattering.

hep-ph↗
arXiv1999

New Insight into the Photoproduction of D-star meson in QCD

In the framework of the model motivated by perturbative calculations in the fourth $O(α^3_sα)$-order, the estimates for the $γp$ cross-section of the $D^*$-meson production in the ZEUS experiment are performed. We factorize the hadronization of $(c\bar q)$-state hardly produced in perturbative QCD, which allows us to take into account the higher twist terms in the powers of $1/p_T$ at $p_T\sim m_c$ and to correctly reproduce the c-quark fragmentation dominant at high $p_T\gg m_c$ to the given order of $α_s$. We find a good agreement with the experimental data on the photoproduction, if the color-octet $(c\bar q)$-state is taken into account, which yields $ \approx 0.33-0.49 GeV^3$.

hep-ph↗
arXiv1997

Doubly Charmed Baryon Production in Hadronic Experiments

In the leading order of perturbative QCD one calculates the total and differential cross-sections for the hadronic production of doubly charmed baryons $Ξ_{cc}$ and $Ξ_{cc}^*$ in different experiments. The experimental evaluation of cross-sections for the $J/Ψ+D + \bar D$ production would allow one to decrease the uncertainty in the determination of cross-sections for the doubly charmed baryons due to the choice of $α_s$ and $m_c$. One shows that in the HERA-B and E781 experiments with fixed tagets the suppression of the $Ξ_{cc}$ and $Ξ_{cc}^*$ production to the yield of $c \bar c$-pairs is the value of the order of $10^{-6}-10^{-5}$, whereas at the TEVATRON and LHC colliders it is about $10^{-4}-10^{-3}$. In the E781 experiment the observation of $Ξ_{cc}$ and $Ξ_{cc}^*$ is practically unpossible. At the HERA-B and TEVATRON facilities one can expect $10^5$ events with the double charm, and at LHC one has about $10^9$ ones.

hep-ph↗
arXiv1997

$B_c$ Meson at LHC

In the framework of perturbative QCD and potential models of heavy quarkonium, total cross-sections and differential characteristics of hadronic production for different spin states of the $B_c$-meson family are calculated at energies of LHC. Theoretical predictions for masses and branching ratios of $B_c$ decays are given, which allows one to make estimates for an expected number of reconstructed events with $B_c$.

hep-ph↗
arXiv1996

Hadronic production of heavy mesons in perturbative QCD

In the framework of perturbative QCD in the fourth order over the $α_s$ coupling constant for the production of two pairs of quarks and in the model of weak binding of the quarks into meson, the analysis of the hadronic production of mesons, containing $b$-quark, is performed, and a minimal transverse momentum is determined, so that at the momenta greater than the found one, the meson differential spectrum can be reliably described in the model of factorization of the hard $b$-quark production and the subsequent fragmentation into the mesons. At low transverse momenta of the meson, nonfragmentational contributions are essential. They are determined by the complete set of QCD diagrams in the given order over $α_s$, so that the latters result in the effect of destructive interference with the diagrams of fragmentation at $z=2E/\sqrt{s}$ close to $1$.

hep-ph↗
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.

hep-ph↗
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↗
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↗