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R. C. Verma

Publications and source records attributed to R. C. Verma.

At least 19 recordsLinked to original sources
arXiv2025

SU(3) analysis of nonfactorizable contributions to bottom mesons decays

This paper is the extension of our previous work [arXiv:2108.03296] entitled Searching a systematics for nonfactorizable contributions to B hadronic decays. In order to realize the full impact of isospin analysis, and to relate decays of strange bottom meson with those of nonstrange bottom mesons, we generalize it to the SU(3) flavor symmetry to investigate the nonfactorizable contributions to CKM-enhanced and CKM-suppressed decays. We start with expressing total weak decay amplitude as sum of the factorizable and nonfactorizable parts, then obtain the factorizable part of the decay amplitude numerically using the known meson decay constants and relevant form-factors, then express the nonfactorizable parts in terms of SU(3)-reduced matrix elements. Using measured branching fractions of a few CKM-favored modes, we fix the reduced matrix elements, and predict branching ratios of the remaining CKM-favored decays and all CKM-suppressed B to PP decays processes.We find that the measured branching fractions agree well with our results, and other predicted values may be tested in the future experiments.

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arXiv2021

Searching a systematics for nonfactorizable contribution to B-and B0 mesons

Two-body weak decays / and are examined under isospin analysis to study nonfactorizable contributions. After extracting the strong phases and obtaining the factorizable contributions from spectator-quark diagrams for Nc=3, we determine nonfactorizable isospin amplitudes from the experimental data for these modes. Our results support the universality of ratio of nonfactorizable isospin reduced amplitudes for these decays within experimental errors. In order to show that this systematics is not coincidental, we also plot our results w. r. t. this ratio.

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arXiv2017

Quark Diagram Analysis of Bottom Meson Decays Emitting Pseudoscalar and Vector Mesons

This paper presents the two body weak nonleptonic decays of B mesons emitting pseudoscalar (P) and vector (V) mesons within the framework of the diagrammatic approach at flavor SU(3) symmetry level. Using the decay amplitudes, we are able to relate the branching fractions of B PV decays induced by both b c and b u transitions, which are found to be well consistent with the measured data. We also make predictions for some decays, which can be tested in future experiments.

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arXiv2015

The First Estimates of Kinematically Forbidden D Meson Decays

The weak hadronic decay D^+ -> K^0\bar a_1^+ is kinematically forbidden at the peak mass values of the particles involved. However, occurrence of this decay has been reported with branching fraction (9.1 \plusminus 1.8) \cross 10^{-3} in the analysis of D^+ -> K^\bar0 4 πdecay data. This is due to smearing effects on this decay caused mainly by the large width of a_1-resonance, which extends the phase space and allows this decay. Using a factorization model to evaluate decay amplitudes for external and internal W-emission diagrams, and incorporating Breit-Wigner smearing using the total a_1 width of 400 MeV, we obtain the first estimate for branching fraction of this decay to be 3.3 \cross 10^{-3} and 7.0 \cross 10^{-3}, for |V_1^{Da1} (0)|=0.40 and 1.50 respectively corresponding to different theoretical models, where |V_1^{Da1} (q^2)| is the vector form factor appearing in the D -> a_1 s-wave transition. The estimates are of the desired order of magnitude. We also predict branching fractions of its counterpart decays D^0 -> K^-\bar a_1^+ and D^0 -> K^0\bar a_1^0.

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arXiv2013

Magnetic Moments of Bottom Baryons: Effective mass and Screened Charge

We calculate the magnetic moments of low lying heavy flavor bottom baryons using effective quark mass and shielded quark charge scheme. We obtain the magnetic moments of both $J^P = 1/2^+$ and $J^P = 3/2^+$ baryon states. We compare our predictions with other theoretical approaches.

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arXiv2012

Effects of Flavor Dependence on Weak Decays of J/psi and Υ

We give the detailed analysis of effects of flavor dependence of average transverse quark momentum inside a meson on J/psi --> P and Υ--> Bc transition form factors and two-body weak hadronic decays of J/psi and Υemploying the factorization scheme. We predict the branching ratios of semileptonic and nonleptonic weak decays of J/psi and Υmesons in Cabibbo-angle-enhanced and Cabibbo-angle-suppressed modes.

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arXiv2011

Decay constants and form factors of s-wave and p-wave mesons in the covariant light-front quark model

We reanalyze the decay constants of s-wave and p-wave mesons and D, B ->M form factors, where M represents a pseudoscalar meson, a vector meson, a scalar meson, or an axial vector meson within a covariant light-front quark model. The parameter βfor wave-functions of most of s-wave mesons and of a few axial-vector mesons are fixed with latest experimental information, wherever available or using the lattice calculations. The treatment of masses and mixing angles for strange axial vector mesons is improved for the purpose. We extend our analysis to determine the form factors appearing in the transition of D_s, B_s->M transitions, and to the isoscalar final state mesons. Numerical results of the form factors for transitions between a heavy pseudoscalar meson and an s-wave or p-wave light meson and their momentum dependence are presented in detail. Further, their sensitivity to uncertainties of beta parameters of the initial as well as the final mesons is investigated. Some experimental measurements of the charmed and bottom meson decays are employed to compare the decay constants and transition form factors obtained in this and other works.

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arXiv2009

Branching ratios of Bc Meson Decaying to Pseudoscalar and Axial-Vector Mesons

We study Cabibbo-Kobayashi-Maskawa (CKM) favored weak decays of Bc mesons in the Isgur-Scora-Grinstein-Wise (ISGW) quark model. We present a detailed analysis of the Bc meson decaying to a pseudoscalar meson (P) and an axial-vector meson (A). We also give the form factors involving transition in the ISGW II framework and consequently, predict the branching ratios of decays.

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arXiv2009

Exclusive Semileptonic Decays of Bc Meson

We present a detailed analysis of exclusive semileptonic decays of Bc meson involving pseudoscalar and vector mesons in the BSW framework, by investigating the effects of the flavor dependence on the average transverse quark momentum inside a meson. Branching ratios of exclusive semileptonic decays of Bc meson are predicted.

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arXiv2007

Flavour structure of low-energy hadron pair photoproduction

We consider the process $γγ\to H_1\bar H_2$ where $H_1$ and $H_2$ are either mesons or baryons. The experimental findings for such quantities as the $p\bar p$ and $K_SK_S$ differential cross sections, in the energy range currently probed, are found often to be in disparity with the scaling behaviour expected from hard constituent scattering. We discuss the long-distance pole--resonance contribution in understanding the origin of these phenomena, as well as the amplitude relations governing the short-distance contribution which we model as a scaling contribution. When considering the latter, we argue that the difference found for the $K_SK_S$ and the $K^+K^-$ integrated cross sections can be attributed to the s-channel isovector component. This corresponds to the $ρω\to a$ subprocess in the VMD (vector-meson-dominance) language. The ratio of the two cross sections is enhanced by the suppression of the $ϕ$ component, and is hence constrained. We give similar constraints to a number of other hadron pair production channels. After writing down the scaling and pole--resonance contributions accordingly, the direct summation of the two contributions is found to reproduce some salient features of the $p\bar p$ and $K^+K^-$ data.

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arXiv1998

A Study of Weak Mesonic Decays of $Λ_c$ and $Ξ_c$ Baryons on the Basis of HQET Results

We investigate two-body Cabibbo-angle enhanced weak decays of charmed baryons into octet baryon and pseudoscalar meson in the current algebra framework with inclusion of the factorization terms which are evaluated using the HQET guided baryonic form factors. We obtain the branching ratios and asymmetry parameters for various Cabibbo-enhanced decays of $Λ_c^+$, $Ξ_c^+$ and $Ξ_c^0$ baryons. Sensitivity of the flavor dependence of the spatial wavefunction overlap on the branching ratios and asymmetry parameters is also investigated.

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