CP-violation in the heavy quark systems
We present a review of general picture in the sector of electroweak symmetry breaking with the CP-violation in the heavy quark interactions.
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arXiv subjects
V. V. Kiselev
Publications and source records attributed to V. V. Kiselev.
Heavy quark potential in the static limit of QCD
Following the procedure and motivations developed by Richardson, Buchmuller and Tye, we derive the potential of static quarks consistent with both the three-loop running of QCD coupling constant under the two-loop perturbative matching of V and MS-bar schemes and the confinement regime at long distances. Implications for the heavy quark masses as well as the quarkonium spectra and leptonic widths are discussed.
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Baryons with two heavy quarks
We consider general physical characteristics of doubly heavy baryons: the spectroscopy in the framework of potential approach and sum rules of QCD, mechanisms of production in various interactions on the basis of fragmentation model with account of preasymptotic corrections caused by higher twists over the transverse momentum of baryon, inclusive decays and lifetimes in the operator product expansion over the inverse powers of heavy quark masses as well as the exclusive decays in the sum rules of QCD. We generalize the methods developed in the effective theory of heavy quarks towards the description of systems with two heavy quarks and a single light quark. The calculations are presented for the masses, decay widths and yields of baryons with two heavy quarks in the running and planned experimental facilities. We discuss the prospects of search for the baryons and possibilities of experimental observation. The most bright physical effects concerning these baryons as well as their position in the system for the theoretical description of heavy quark dynamics are considered.
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Doubly heavy baryons Omega_QQ' vs. Xi_QQ' in sum rules of NRQCD
In the framework of two-point sum rules of NRQCD, the masses and couplings of doubly heavy baryons to the corresponding quark currents are evaluated with account of coulomb-like corrections in the system of doubly heavy diquark as well as the contribution of nonperturbative terms determined by the quark, gluon, mixed condensates and the product of gluon and quark condensates. The introduction of nonzero light quark mass destroys the factorization of baryon and diquark correlators even at the perturbative level and provides the better convergency of sum rules. We estimate the difference M_Omega - M_Xi = 100+/- 10 MeV. The ratio of baryonic constants |Z_Omega|^2/|Z_Xi|^2 is equal to 1.3+/-0.2 indicating the violation of SU(3) flavor symmetry for the doubly heavy baryons.
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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.
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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.
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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.
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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.
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Doubly heavy baryons in sum rules of NRQCD
The masses of baryons containing two heavy quarks and their couplings to the corresponding quark currents are evaluated in the framework of NRQCD sum rules. The coulomb-like corrections in the system of doubly heavy diquark are taken into account, and the contribution of nonperturbative terms coming from the quark, gluon and mixed condensates as well as the product of quark and gluon condensates, is analyzed. The higher condensates destroy the factorization of baryon and diquark correlators and provide the convergency of sum rule method. As a result the accuracy of estimates is improved.
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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.
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Perturbative fragmentation of vector colored particle into bound states with a heavy antiquark
The fragmentation function of vector particle into possible bound S-wave states with a heavy antiquark is calculated in the leading order of perturbative QCD for the high energy processes at large transverse momenta with the different behaviour of anomalous chromomagnetic moment. One-loop equations are derived for the evolution of fragmentation function moments, which is caused by the emission of hard gluons by the vector particle. The integrated probabilities of fragmentation are given. The distribution of bound state over the transverse momentum with respect to the axis of fragmentation is calculated in the scaling limit.
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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$.
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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.
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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.
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Neutrino masses and Z' physics
The characteristic scale of neutral current, provided by an extension of Standard Model with a local group over the right-handed fermions, determines the smallness of neutrino masses of Dirac kind. The experimental observation of neutrino oscillations imposes the stringent limit on the $Z^\prime$ physics appearance at low energies.
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Two-loop anomalous dimensions for currents of baryons with two heavy quarks in NRQCD
We present analytical results on the two-loop anomalous dimensions of currents for baryons, containing two heavy quarks $J = [Q^{iT}CΓτQ^j]Γ' q^kε_{ijk}$ with arbitrary Dirac matrices $Γ$ and $Γ'$ in the framework of NRQCD in the leading order over both the relative velocity of heavy quarks and the inverse heavy quark mass. It is shown, that in this approximation the anomalous dimensions do not depend on the Dirac structure of the current under consideration.
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Model for three generations of fermions
A model is constructed for a chiral abelian gauge-interaction of fermions and a potential of three higgses, so that the potential possesses a discrete symmetry of the vacuum state, which provides the introduction of three generations for the fermions. For the model including charged currents, a matrix of the flavor mixing is described, and a phase giving the violation of CP-invariance is determined. Some approximate relations connecting the values of mixing matrix to the mass ratios for the fermions in different generations are derived.
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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 $τ_{Ξ_{cc}^{+}}=0.11\pm 0.01~ps$.
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