Strong and radiative decays of the Ds0*(2317) meson in the DK-molecule picture

We consider a possible interpretation of the new charm-strange meson Ds0*(2317) as a hadronic molecule - a bound state of D and K mesons. Using an effective Lagrangian approach we calculate the strong Ds0* to Ds pi0 and radiative Ds0* to Ds* gamma decays. A new impact related to the DK molecular structure of the Ds0*(2317) meson is that the presence of u(d) quarks in the D and K mesons gives rise to a direct strong isospin-violating transition Ds0* to Ds pi0 in addition to the decay mechanism induced by eta-pi0 mixing considered previously. We show that the direct transition dominates over the eta-pi0 mixing transition in the Ds0* to Ds pi0 decay. Our results for the partial decay widths are consistent with previous calculations.Comment: 22 pages, 4 figures, accepted for publication in Phys. Rev.

Ds0*(2317) and Ds1(2460) mesons in two-body B-meson decays

We analyze the branching ratios of B to D(*) + Ds0*(Ds1) decays using the factorization hypothesis. The B to D(*) transition form factors are taken from a model-independent analysis done by Caprini, Lellouch and Neubert based on heavy quark spin symmetry and dispersive constraints, including short-distance and power corrections. The leptonic decay constants fDs0* and fDs1 are calculated assuming a molecular structure for the Ds0* and Ds1 mesons. The calculated branching ratios of B-meson two-body decays are compared with experimental data and other theoretical results.Comment: 12 pages, 2 figure

Исследование методов расчета матриц рассеяния аналоговых трактов активных фазированных антенных решеток

The paper is devoted to determining the optimal method for calculating the cascade connection of scattering matrices according to the criterion of the least computational complexity and the highest accuracy. The analysis is carried out for several methods: the block N-matrices method, the block T-matrices method, and the method of free and coupled ports. The article presents a numerical analysis of the accuracy of the presented methods, as well as numerical indicators of computational complexity. Zaikov K. D., Anikin A. S., Yarkov K. A. Methods for calculating scattering matrices of analog path of active phased array antennas. Ural Radio Engineering Journal. 2022;6(2):205–221. (In Russ.) DOI: 10.15826/urej.2022.6.2.005. В статье приведен анализ существующих методов и алгоритмов расчета каскадного соединения матриц рассеяния. В работе рассматривались три метода: метод блочных S-матриц, метод блочных T-матриц, метод свободных и связанных портов. Было проведено исследование точности и вычислительной сложности методов, что позволило определить оптимальный метод расчета каскадного соединения матриц рассеяния по критерию наименьшей вычислительной сложности и наибольшей точности. Зайков К. Д., Аникин А. С., Ярков К. А. Исследование методов расчета матриц рассеяния аналоговых трактов активных фазированных антенных решеток. Ural Radio Engineering Journal. 2022;6(2):205–221. DOI: 10.15826/urej.2022.6.2.005

SU(2)xSU(2) nonlocal quark model with confinement

The nonlocal version of the SU(2)xSU(2) symmetric four-quark interaction of the NJL type is considered. Each of the quark lines contains the form factors. These form factors remove the ultraviolet divergences in quark loops. The additional condition on quark mass function m(p) ensures the absence of the poles in the quark propagator(quark confinement). The constituent quark mass m(0) is expressed thought the cut-off parameter Lambda, m(0)=Lambda=340 MeV in the chiral limit. These parameters are fixed by the experimental value of the weak pion decay and allow us to describe the mass of the light scalar meson, strong decay rho -> pi pi and D/S ratio in the decay a_1 -> rho pi in satisfactory agreement with experimental data.Comment: 8 pages, 1 figure

Light baryon magnetic moments and N -> Delta gamma transition in a Lorentz covariant chiral quark approach

We calculate magnetic moments of light baryons and N -> Delta gamma transition characteristics using a manifestly Lorentz covariant chiral quark approach for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons.Comment: 29 pages, 10 figures, accepted for publication in Phys. Rev.

DVCS amplitude at tree level: Transversality, twist-3, and factorization

We study the virtual Compton amplitude in the generalized Bjorken region (q^2 -> Infinity, t small) in QCD by means of a light-cone expansion of the product of e.m. currents in string operators in coordinate space. Electromagnetic gauge invariance (transversality) is maintained by including in addition to the twist-2 operators 'kinematical' twist-3 operators which appear as total derivatives of twist-2 operators. The non-forward matrix elements of the elementary twist-2 operators are parametrized in terms of two-variable spectral functions (double distributions), from which twist-2 and 3 skewed distributions are obtained through reduction formulas. Our approach is equivalent to a Wandzura-Wilczek type approximation for the twist-3 skewed distributions. The resulting Compton amplitude is manifestly transverse up to terms of order t/q^2. We find that in this approximation the tensor amplitude for longitudinal polarization of the virtual photon is finite, while the one for transverse polarization contains a divergence already at tree level. However, this divergence has zero projection on the polarization vector of the final photon, so that the physical helicity amplitudes are finite.Comment: 34 pages, revtex, 1 eps figure included using epsf. Misprints corrected, one reference adde

Two-loop matching of the dipole operators for b→sγb \to s \gamma and b→sgluonb \to s gluon

The order $\alpha_s$ corrections to the Wilson coefficients of the dipole operators ($O_7,O_8$) at the matching scale $\mu =m_W$ are a crucial ingredient for a complete next- to-leading logarithmic calculation of the branching ratio for $b \to s \gamma$. Given the phenomenological relevance and the fact that this two-loop calculation has been done so far only by one group [1], we present a detailed re-calculation using a different method. Our results are in complete agreement with those in ref. [1].Comment: 24 pages, latex, 6 figures include

Pion light-cone wave function and pion distribution amplitude in the Nambu-Jona-Lasinio model

We compute the pion light-cone wave function and the pion quark distribution amplitude in the Nambu-Jona-Lasinio model. We use the Pauli-Villars regularization method and as a result the distribution amplitude satisfies proper normalization and crossing properties. In the chiral limit we obtain the simple results, namely phi_pi(x)=1 for the pion distribution amplitude, and = -M / f_pi^2 for the second moment of the pion light-cone wave function, where M is the constituent quark mass and f_pi is the pion decay constant. After the QCD Gegenbauer evolution of the pion distribution amplitude good end-point behavior is recovered, and a satisfactory agreement with the analysis of the experimental data from CLEO is achieved. This allows us to determine the momentum scale corresponding to our model calculation, which is close to the value Q_0 = 313 MeV obtained earlier from the analogous analysis of the pion parton distribution function. The value of is, after the QCD evolution, around (400 MeV)^2. In addition, the model predicts a linear integral relation between the pion distribution amplitude and the parton distribution function of the pion, which holds at the leading-order QCD evolution.Comment: mistake in Eq.(38) correcte

Exclusive Nonleptonic Decays of Bottom and Charm Baryons in a Relativistic Three-Quark Model: Evaluation of Nonfactorizing Diagrams

Exclusive nonleptonic decays of bottom and charm baryons are studied within a relativistic three-quark model with a Gaussian shape for the momentum dependence of the baryon-three-quark vertex. We include factorizing as well as nonfactorizing contributions to the decay amplitudes. For heavy-to-light transitions Q -> q u d the total contribution of the nonfactorizing diagrams amount up to approximately 60% of the factorizing contributions in amplitude, and up to approximately 30% for b -> c u d transitions. We calculate the rates and the polarization asymmetry parameters for various nonleptonic decays and compare them to existing data and to the results of other model calculations.Comment: 49 pages, LaTeX-fil

Dirac neutrino magnetic moment and a possible time evolution of the neutrino signal from a supernova

We analyze the influence of neutrino helicity conversion, $\nu_L \to \nu_R$, on the neutrino flux from a supernova caused by the interaction of the Dirac neutrino magnetic moment with a magnetic field. We show that if the neutrino has a magnetic moment in the interval $10^{-13} \, \mu_{\rm B} < \mu_\nu < 10^{-12} \, \mu_{\rm B}$ and provided that a magnetic field of $\sim 10^{13} - 10^{14}$ G exists in the supernova envelope, a peculiar kind of time evolution of the neutrino signal from the supernova caused by the resonance transition $\nu_L \to \nu_R$ in the magnetic field of the envelope can appear. If a magnetar with a poloidal magnetic field is formed in a supernova explosion, then the neutrino signal could have a pulsating behavior, i.e., a kind of a neutrino pulsar could be observed, when it rotates around an axis that does not coincide with its magnetic moment and when the orientation of its rotation axis is favourable for our observation.Comment: 9 pages, LaTeX, 2 EPS figures, based on the talk presented by A.V. Kuznetsov at the XVI International Seminar Quarks'2010, Kolomna, Moscow Region, June 6-12, 2010, to appear in the Proceeding