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I. M. Narodetskii

Publications and source records attributed to I. M. Narodetskii.

At least 37 records · Page 2Linked to original sources
arXiv2002

Spectroscopy of Baryons Containing Two Heavy Quarks in Nonperturbative Quark Dynamics

We have studied the three quark systems in an Effective Hamiltonian approach in QCD. With only two parameters: the string tension sigma and the strong coupling constant alpha_s we obtain a good description of the ground state light and heavy baryons. The prediction of masses of the doubly heavy baryons not discovered yet are also given. In particular, a mass of 3620 MeV for the lightest (ccu) baryon is found by employing the hyperspherical formalism to the three quark confining potential with the string junction.

hep-ph↗
arXiv2002

The bound state corrections to the semileptonic decays of the heavy baryons

We present an investigation of the lepton energy distributions in the inclusive semileptonic weak decays of heavy baryons performed within a relativistic quark model formulated on the light front (LF). Using the heavy-quark LF distribution functions related to the equal time momentum wave functions taken from the Kalman--Tran--D'Souza model we compute the electron energy spectra and the total semileptonic widths of the Lambda_Q and Xi_Q (Q=c,b) baryons and confront the results with existing data.

hep-ph↗
arXiv2002

The doubly heavy baryons

We present the results for the masses of the doubly heavy baryons $Ξ_{QQ'}$ and $Ω_{Q'Q}$ where $Q,Q'=b,c$ obtained in the framework of the simple approximation within the nonperturbative string approach.

hep-ph↗
arXiv2002

The doubly heavy baryons in the nonperturbative QCD approach

We present some piloting calculations of the masses of the doubly heavy baryons in the framework of the simple approximation within the nonperturbative string approach. The simple analytical results for dynamical masses of heavy and light quarks and eigenvalues of the effective QCD Hamiltonian are presented.

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arXiv2001

Baryons in the nonperturbative string approach

We present some piloting calculations of masses and short-range correlation coefficients for the ground states of light and heavy baryons in the framework of the simple approximation within the nonperturbative QCD approach.

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arXiv2001

The heavy baryons in the nonperturbative string approach

We present some piloting calculations of the short-range correlation coefficients for the light and heavy baryons and masses of the doubly heavy baryons $Ξ_{QQ'}$ and $Ω_{QQ'}$ ($Q,Q'=c,b$) in the framework of the simple approximation within the nonperturbative QCD approach.

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arXiv2001

The bound state corrections to the semileptonic decays of the B meson. The light-front approach versus ACM model

A generalization of the parton-like formula is used for the first time to find the differential distributions in the inclusive semileptonic weak decays of the B meson. The main features of this new approach are the treatment of the b-quark as an on-mass-shell particle and the inclusion of the effects arising from the b-quark transverse motion in the B-meson. Using the b-quark light-front (LF) distribution function related to the equal time momentum wave function taken from the ACM model we compute the electron energy spectra and the total semileptonic widths of the B meson. We find an impressive agreement between the electron energy spectra calculated in the LF approach and the ones obtained in the ACM model, provided the b quark mass is identified with the average of the floating b quark mass in the ACM model. In spite of the simplicity of the model we obtain a fair good description of the CLEO data for V_{cb}=0.042.

hep-ph↗
arXiv2001

The Kalman-Tran-D'Souza Model and the Semileptonic Decay Rates of Heavy Baryons

We present an investigation of the inclusive semileptonic decay widths of the heavy baryons Lambda_Q and Xi_Q, (Q=b,c) performed within a relativistic constituent quark model, formulated on the light-front. In a way conceptually similar to the deep-inelastic scattering case, the H_Q baryon inclusive width is expressed as the integral of the free Q-quark partial width multiplied by a bound-state factor related to the Q-quark distribution function in the H_Q. The non-perturbative meson structure is described through the quark-model wave functions, constructed via the Hamiltonian light-front formalism using as input the Kalman-Tran-D'Souza equal time wave functions. A link between spectroscopic quark models and the H_Q decay physics is obtained in this way. It is shown that the bound-state effects and the Fermi motion of the b-quark remarkably reduce the decay rate with respect to the free-quark result. Our predictions for the BR(Lambda_c ->X_s e nu_e) and BR(Lambda_b->X_c e nu_e) decays are in good agreement with existing data.

hep-ph↗
arXiv2000

The Lambda_b lifetime in the light front quark model

The enhancement of the Lambda_b decay width relative to B decay one due to the difference of Fermi motion effects in Lambda_b and B is calculated in the light--front quark model with the simplifying assumption that Lambda_b consists of the heavy quark and light scalar diquark. In order to explain the large deviation from unity in the experimental result for tau(Lambda_b)/tau(B), it is necessary that diquark be light and the ratio of the squares of the Lambda_b and B wave functions at the origin be \le 1.

hep-ph↗
arXiv1999

A connection between inclusive semileptonic decays of bound and free heavy quarks

A relativistic constituent quark model, formulated on the light-front, is used to derive a new parton approximation for the inclusive semileptonic decay width of the B-meson. A simple connection between the decay rate of a free heavy-quark and the one of a heavy-quark bound in a meson or in a baryon is established. The main features of the new approach are the treatment of the b-quark as an on-mass-shell particle and the inclusion of the effects arising from the b-quark transverse motion in the B-meson. In a way conceptually similar to the deep-inelastic scattering case, the B-meson inclusive width is expressed as the integral of the free b-quark partial width multiplied by a bound-state factor related to the b-quark distribution function in the B-meson. The non-perturbative meson structure is described through various quark-model wave functions, constructed via the Hamiltonian light-front formalism using as input both relativized and non-relativistic potential models. A link between spectroscopic quark models and the B-meson decay physics is obtained in this way. Our predictions for the B -> X_c l nu_l and B -> X_u l nu_l decays are used to extract the CKM parameters |V_cb| and |V_ub| from available inclusive data. After averaging over the various quark models adopted and including leading-order perturbative QCD corrections, we obtain |V_cb| = (43.0 +/- 0.7_exp +/- 1.8_th) 10^-3 and |V_ub| = (3.83 +/- 0.48_exp +/- 0.14_th) 10^-3, implying |V_ub / V_cb| = 0.089 +/- 0.011_exp +/- 0.005_th, in nice agreement with existing predictions.

hep-ph↗
arXiv1999

The non-perturbative corrections to the $\bar B \to X_sγ$ photon spectrum in a parton-like model

We derive a new parton-like formula, which establishes a simple connection between the electroweak decay rate $Γ(\bar B \to X_sγ$) and the rate of a free b-quark decay. The main features of our approach are the treatment of the b-quark as an on-mass-shell particle and the inclusion of the effects arising from the b-quark transverse motion in the $\bar B$-meson. Using various b-quark light-front (LF) distribution functions, both phenomenological one and the ones derived from current constituent quark models, and neglecting perturbative corrections we compute the photon energy spectra and the moments of the shape function. It is shown that the parton-like approach is fully consistent with the Heavy Quark Effective Theory (HQET) provided the b-quark constituent mass is redefined in the way similar to that used in HQET to define the pole mass of the b quark. In this way the correction to first order in $1/m_b$ can be eliminated from the total width in agreement with the general statement of HQET. We have also found that the photon energy spectra calculated in the LF approach agree well with the ones obtained in the ACM model, provided the same distribution function is used as input in both cases. In spite of the simplicity of the model our results show a fair good agreement both with the HQET predictions and available experimental data.

hep-ph↗
arXiv1998

The B_c Meson Lifetime in the Light--Front Constituent Quark Model

We present an investigation of the total decay rate of the (ground state) B_c meson within the framework of the relativistic constituent quark model formulated on the light-front (LF). The exclusive semileptonic (SL) and nonleptonic (NL) beauty and charm decays of the B_c meson are described through vector and axial hadronic form factors, which are calculated in terms of a constituent quark model LF wave functions. The latter ones are derived via the Hamiltonian LF formalism using as input the update versions of the constituent quark model. The inclusive SL and NL partial rates are calculated within a convolution approach inspired by the partonic model and involving the same B_c wave function which is used for evaluation of the exclusive modes. The framework incorporates systematically 84 exclusive and 44 inclusive partial rates corresponding to the underlying \bar{b}\to\bar{c} and c\to s quark decays. Based on our approach we findτ_{B_c}=0.59 \pm 0.06 ps where the theoretical uncertainty is dominated by the uncertainty in the choice of LF wave functions and the threshold values for the hadron continuum. For the branching fractions of the B^+_c \to J/ψμ^+ν_μ and B_c^+\to J/ψπ^+ decays we obtain 1.6 % and 0.1 %, respectively.

hep-ph↗
arXiv1998

Exclusive and Inclusive Decays of the B_c Meson in the Light-Front ISGW Model

We investigate the total decay rate of the (ground state) $B_c$ meson within the framework of the relativistic constituent quark model formulated on the light-front (LF). The exclusive semileptonic (SL) and nonleptonic (NL) beauty and charm decays of the $B_c$ meson are described through vector and axial hadronic form factors, which are calculated in terms of the overlap of the parent and daughter LF wave functions. The latters are derived via the Hamiltonian LF formalism using as input the update version of the ISGW model. The inclusive SL and NL partial rates are calculated within a convolution approach inspired by the partonic model and involving the same $B_c$ wave function which is used for evaluation of the exclusive modes. We predict the partial rates for 74 exclusive SL and NL channels and 43 inclusive partial rates corresponding to the underlying $\bar{b}\to \bar{c}$ and $c\to s$ quark decays. Based on our approach we find $Γ^{\bar{b}}(B_c)= 0.52 \pm 0.02 ps^{-1}$, $Γ^{c}(B_c)= 0.98 \pm 0.07 ps^{-1}$, where the theoretical uncertainty is dominated by the uncertainty in the choice of the threshold values at which the hadron continuum starts. For the $B_c$ lifetime we obtain $τ_{B_c}= 0.63 \pm 0.02 ps$ in a good agreement with the prediction obtained using the nonrelativistic operator product expansion. We also predict decay rates for many specific weak transitions of $B_c$. In particular, for the branching fractions of the $B^+_c \to J/ψμ^+ν_μ$, $B_c^+\to J/ψπ^+$ and $B_c^+ \to J/ψ+X $ decays we obtain 1.7%, 0.1 % and 13.2%, respectively.

hep-ph↗
arXiv1997

Exclusive and inclusive weak decays of the B-meson

A relativistic quark model is applied to the description of semileptonic and non-leptonic charmed decays of the B-meson. The exclusive semileptonic modes B -> D l νand B -> D* l νare described through the universal Isgur-Wise form factor, which is calculated in terms of a constituent quark model wave function for the B-meson. Different approximations for the latter, either based on a phenomenological ansatz or derived from analyses of the meson spectra, are adopted. In particular, two wave functions, constructed via the Hamiltonian light-front formalism using a relativized and a non-relativistic constituent quark model, are considered, obtaining a link between standard spectroscopic quark models and the B-meson decay physics. The inclusive semileptonic and non-leptonic branching ratios are calculated within a convolution approach, inspired by the partonic model and involving the same B-meson wave function used for the evaluation of the exclusive semileptonic modes. Our results for the major branching ratios are consistent with available experimental data and the sum of all the calculated branching ratios turns out to be close to unity. In particular, we found that: i) a remarkable fraction (~ 35%) of semileptonic decay modes occur in non-D, non-D* final states; ii) non-perturbative effects enhance the inclusive b -> c \bar{u} d decay channels, with a sizable contribution provided by internal decays into heavy mesons and baryon-antibaryon pairs; the resulting reduction of the semileptonic branching ratio brings the theoretical prediction in agreement with the experimental value without increasing at the same time the charm counting.

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

Charmed decays of the B-meson in the quark model

Exclusive and inclusive, semileptonic and non-leptonic, charmed decays of the B-meson are investigated in the context of a phenomenological quark model. Bound-state effects are taken care of by adopting a single (model-dependent) non-perturbative wave function, describing the motion of the light spectator quark in the B-meson. A nice reproduction of both exclusive and inclusive semileptonic data is obtained. Our predictions for the electron spectrum are presented and compared with those of the Isgur-Scora-Grinstein-Wise quark model. Finally, our approach is applied to the calculation of inclusive non-leptonic widths, obtaining a remarkable agreement with experimental findings.

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