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A. K. Likhoded

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

At least 91 records · Page 5Linked to original sources
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

Decays and Lifetime of B_c in QCD Sum Rules

In the framework of three-point QCD sum rules, the form factors for the semileptonic decays of B_c^+ -> B_s(B_s^*) l νare calculated with account for the Coulomb-like alpha_s/v-corrections in the heavy quarkonium. The generalized relations due to the spin symmetry of HQET/NRQCD for the form factors are derived at the recoil momentum close to zero. The nonleptonic decays are studied using the assumption on the factorization. The B_c meson lifetime is estimated by summing up the dominating exclusive modes in the c -> s transition combining the current calculations with the previous analysis of b -> c decays in the sum rules of QCD and NRQCD.

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↗
arXiv2000

B_c Decays and Lifetime in QCD Sum Rules

In the framework of three-point QCD sum rules, the form factors for the semileptonic decays of B_c --> B_s(B_s^*) l νare calculated with account for the Coulomb-like alpha_s/v-corrections in the heavy quarkonium. The generalized relations due to the spin symmetry of HQET/NRQCD for the form factors are derived at the recoil momentum close to zero. The nonleptonic decays are studied using the assumption on the factorization. The B_c meson lifetime is estimated by summing up the dominating exclusive modes in the c --> s transition combining the current calculations with the previous analysis of b --> c decays in the sum rules of QCD and NRQCD.

hep-ph↗
arXiv2000

Spectroscopy of doubly heavy baryons

Spectra of masses are calculated for the families of doubly heavy baryons in the framework of nonrelativistic quark model with the QCD potential by Buchmuller--Tye. We suppose the quark-diquark structure for the wave functions and take into account the spin-dependent splittings. The physical reasons causing the existence of quazi-stable excited states in the subsystem of heavy diquark are considered for the heavy quarks of identical flavors.

hep-ph↗
arXiv2000

Charmed hadrons production in high-energy $Σ^-$ beam

We present the calculation of the inclusive x_F-distributions of charmed hadrons, produced in high-energy $Σ^-$-beam. Our calculation is based on the modified mechanism of charmed quarks fragmentation as well as on the mechanism of c-quark recombination with the valence quarks from initial hadrons.

hep-ph↗
arXiv1999

Lifetimes of doubly heavy baryons

We perform a detailed investigation of total lifetimes for the doubly heavy baryons $Ξ_{QQ'}$, $Ω_{QQ'}$ in the framework of operator product expansion over the inverse heavy quark mass, whereas, to estimate matrix elements of operators obtained in OPE, approximations of nonrelativistic QCD are used.

hep-ph↗
arXiv1999

Semileptonic B_c-meson decays in sum rules of QCD and NRQCD

The semileptonic B_c-meson decays into the heavy quarkonia J/ψ(η_c) and a pair of leptons are investigated in the framework of three-point sum rules of QCD and NRQCD. Calculations of analytical expressions for the spectral densities of QCD and NRQCD correlators with account for the Coulomb-like α_s/v terms are presented. The generalized relations due to the spin symmetry of NRQCD for the form factors of B_c\to J/ψ(η_c)lν_l transitions with l denoting one of the leptons e, μor τ, are derived at the recoil momentum close to zero. This allows one to express all NRQCD form factors through a single universal quantity, an analogue of Isgur-Wise function at the maximal invariant mass of lepton pair. The gluon condensate corrections to three-point functions are calculated both in full QCD in the Borel transform scheme and in NRQCD in the moment scheme. This enlarges the parameteric stability region of sum rule method, that makes the results of the approach to be more reliable. Numerical estimates of widths for the transitions of B_c\to J/ψ(η_c)lν_l are presented.

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↗
arXiv1999

Spectroscopy of doubly charmed baryons: $Ξ_{cc}^{+}$ and $Ξ_{cc}^{++}$

Using the quark-diquark approximation in the framework of Buchm\" uller-Tye potential model, we investigate the spectroscopy of doubly charmed baryons: $Ξ_{cc}^{++}$ and $Ξ_{cc}^{+}$. Our results include the masses, parameters of radial wave functions of states with the different excitations of both diquark and light quark-diquark system. We calculate the values of fine and hyperfine splittings of these levels and discuss some new features, connected to the identity of heavy quarks, in the dynamics of hadronic and radiative transitions between the states of these baryons.

hep-ph↗
arXiv1999

Lifetimes of Xi_{bc}^{+} and Xi_{bc}^{0} baryons

Estimates of lifetimes and partial branching ratios for the baryons $Ξ_{bc}^{+}$ and $Ξ_{bc}^{0}$ are presented using the inverse heavy quark mass expansion technique carried out in the Operator Product Expansion approach. We take into account both the perturbative QCD corrections to the spectator contributions and, depending on the quark contents of hadrons, the Pauli interference and weak scattering effects between the constituents, using a potential model for the evaluation of the non-perturbative parameters.

hep-ph↗
arXiv1998

Lifetimes of doubly charmed baryons: $Ξ_{cc}^{+}$ and $Ξ_{cc}^{++}$

We have performed a detailed investigation of total lifetimes for the $Ξ_{cc}^{++}$ and $Ξ_{cc}^{+}$ baryons in the framework of operator product expansion over the inverse mass of charmed quark, whereas, to estimate matrix elements of operators obtained in OPE, some approximations of nonrelativistic QCD are used. This approach allows one to take into account the corrections to the spectator decays of $c$-quarks, which reflect the fact, that these quarks are bound, as well as the contributions, connected to the effects of both the Pauli interference for the $Ξ_{cc}^{++}$-baryon and the weak scattering for the $Ξ_{cc}^{+}$-baryon. The realization of such program leads to the following estimates for the total lifetimes of doubly charmed baryons: $τ_{Ξ_{cc}^{++}}=0.43\pm 0.1~ps$ and $τ_{Ξ_{cc}^{+}}=0.11\pm 0.01~ps$.

hep-ph↗
arXiv1997

On Mechanism of Charmed c-Quarks Fragmentation in Hadronic Collisions

We propose a modification of the mechanism of charmed quarks fragmentation into $D$ mesons in hadronic collisions. It is shown that the distinction in valence quark distributions in the initial $π^{\pm}$ and $K^{\pm}$ mesons leads to different inclusive spectra of $D$ and $D_s$ mesons produced in $π^{\pm}$ and $K^{\pm}$ beams.

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↗