arXiv subjects

N. B. Demchuk

Publications and source records attributed to N. B. Demchuk.

3 recordsLinked to original sources

arXiv1998

Heavy quark limit in the light front quark model

An explicit relativistic light-front model is presented which gives the momentum transfer dependent form factors of weak hadronic currents among heavy pseudoscalar and vector mesons in the whole accessible kinematical region $0\leq q^2 \leq q^2_{\max} $. It is shown that in the limit of infinite masses of active quarks these form factors can be expressed in terms of universal Isgur-Wise function. The explisit expression for this function is obtained. It is shown that neglecting of pair creation from the vacuum in calculations of form factors does not violate Luke's theorem.

hep-ph↗

arXiv1997

The Light-Front Model for Exclusive Semileptonic B- and D-decays

An explicit relativistic light-front quark model is presented which gives the momentum transfer dependent form factors of weak hadronic currents among heavy pseudoscalar and vector mesons in the whole accessible kinematic region $ 0\leq q^2 \leq q^2_{max} $. For the numerical investigations of the $ B \to D^* l ν_l $, $ B \to ρl ν_l $, $ D\to K^* l ν_l $ and $ D \to ρl ν_l $ semileptonic decays the equal time wave functions corresponding to the updated version of the ISGW model are adopted. Using the available experimental information on branching fractions $ BR(B \to D^* l ν_l) $ and $ BR(B \to ρl ν_l) $ the CKM parameters $ V_{cb} $ and $ V_{ub} $ were estimated: $ |V_{cb}| = 0.036 \pm 0.004 $, $ |V_{ub}| = 0.0033 \pm 0.0004 $. The model is further tested by comparison with experimental data, QCD sum rules and lattice calculations.

hep-ph↗

arXiv1996

Heavy-to-heavy and heavy-to-light weak decay form factors in the light-front approach: the exclusive $ 0^- $ to $ 0^- $ case

Weak transition form factors among heavy pseudoscalar mesons are investigated within a relativistic quark model formulated on the light-front. It is shown that the light-front result derived in the time-like region for the matrix elements of the plus component of the weak vector current coincides with the spectator pole term of the quark triangle diagram. For the first time, the dependence of the form factors on the squared four-momentum transfer $q^2$ is calculated in the whole accessible kinematical region $0 \leq q^2 \leq q^2_{max}$. For the numerical investigations of the semileptonic $B \to D \ell ν_{\ell}$, $B \to π\ell ν_{\ell}$, $D \to K \ell ν_{\ell}$ and $D \to π\ell ν_{\ell}$, the equal-time wave functions corresponding to the updated version of the ISGW model are adopted. Our results for the form factors and the decay rates are presented and compared with available experimental data and predictions of different approaches. Moreover, the $K^0_L \to π^{\pm} ~ e^{\mp} ~ ν_e$ decay is briefly discussed. Our approach is consistent with experimental data.

hep-ph↗