arXiv subjects

Debrupa Chakraverty

Publications and source records attributed to Debrupa Chakraverty.

9 recordsLinked to original sources

arXiv2003

Effects of Universal Extra Dimensions on $B^0 - {\bar B^0}$ Mixing

We study contributions coming to $Δm_B$ from one or more universal extra dimensions (UED) in which all the Standard Model fields can propagate. In the model with a single UED, the box diagrams for mixing are convergent and therefore insensitive to the cutoff scale of the theory. In the case of two UEDs, the result is not very sensitive to the cut-off scale due to GIM mechanism. Within the present range of the parameters at $1 σ$ level, the lower bound on the compactification scale 1/R has been estimated to be 165 GeV for one UED and 280 GeV for two UEDs. The bound increases drastically if one can have a better determination of the $B$ meson decay constant $f_B$ and the QCD correction parameter $B_B$. For example, it rises to 740 GeV (for one UED) if the error (at $1σ$) in the determination of $f_B\sqrt{B_B}$ from quenched lattice calculation is reduced to one-third from its present value. The UED contributions to the $K$ system are strongly suppressed.

hep-ph↗

arXiv2001

Heavy quark production via supersymmetric interaction at a neutrino factory

We investigate b-quark production in both charged and neutral current channels through neutrino-nucleon scattering at a neutrino factory, mediated by the lepton flavour violating interactions present in a supersymmetric theory with broken R-parity. Using values of the effctive interaction strengths well below the current and projected experimental bounds, we are still able to predict markedly enhanced event rates, especially for the neutral current events which are not allowed at the lowest order in the standard model (SM). Data from neutrino factories can therefore be used to probe strengths of such interactions to considerably higher precision than what can be envisioned in other experiments.

hep-ph↗

arXiv2001

A nonsupersymmetric resolution of the anomalous muon magnetic moment

The recent result from the E821 experiment at BNL on the anomalous magnetic moment of the muon shows a distinct discrepancy with the Standard Model predictions. We calculate the additional correction that the anomalous magnetic moment receives in a model with scalar leptoquarks. We find that such models can account for the deviation from the SM value even for small leptoquark couplings.

hep-ph↗

arXiv2000

B-physics constraints on baryon number violating couplings: grand unification or R-parity violation

We investigate the role that baryon number violating interactions may play in $B$ phenomenology. Present in various grand unified theories, supersymmetric theories with R-parity violation and composite models, a diquark state could be quite light. Using the data on B decays as well as $B - {\bar B}$ mixing, we find strong constraints on the couplings that such a light diquark state may have with the Standard Model quarks.

hep-ph↗

arXiv2000

b --> s gamma confronts B-violating scalar couplings: R-parity violating supersymmetry or diquark

We investigate the possible role that baryon number violating Yukawa interactions may take in the inclusive decay $ B \to X_s γ$. The constraints, derived using the experimental results of the CLEO collaboration, turn out, in many cases, to be more stringent than the existing bounds.

hep-ph↗

arXiv1998

Dispersive Bounds on The Shape Of Lambda_b to Lambda_c l {\bar ν_l} Formfactors

We derive a theoretically allowed domain for the charge radius $ρ$ and curvature $c$ of the Isgur-Wise function describing the decay $Λ_b \to Λ_c l {\bar ν_l}$. Our method uses crossing symmetry, dispersion relations and analyticity in the context of the Heavy Quark Effective Theory but is independent of the specifics of any given model. The experimentally determined values of the $Υ$ masses have been used as input information. The results are of interest for testing different models employed to calculate the heavy baryon formfactors which are used for the extraction of $| V_{cb} |$ from the experimental data.

hep-ph↗

arXiv1996

Non-relativistic Model for the Semileptonic Λ_b \to Λ_c Decay

We calculate the decay width for $Λ_b \to Λ_c e {\bar ν}$ in the frame work of a nonrelativistic quark (NRQ) model of heavy baryons where the light quarks play the role of spectators. Our calculation does not make an explicit use of the heavy quark symmetry. The branching ratio for the above process as calculated here agrees reasonably well with the experimental value.

hep-ph↗

arXiv1996

Applicability of Heavy Quark Effective Theory to the Radiative Decay $B\to K^* + γ$

In the context of the observed decay $B \rightarrow K^* γ$ the applicability of the Heavy Quark Effective Theory (HQET), treating both b and s as heavy quarks, is examined. We show that the heavy s-quark approximation, as can be found in the literature, is not reliable.

hep-ph↗

arXiv1995

Constraints on a General Higgs Sector from $K^0-\bar K^0$, $B_d- \bar B_d$ Mixing and the $ε$ Parameter

The scalar sector of the Standard Model is extended to include an arbitrary assortment of scalars. In the case where this assignment does not preserve $ρ=1$ at the tree-level, the departure from unity itself puts the most stringent constraint on the scalar sector, and where $ρ_{tree}=1$ is maintained, useful bounds on the parameter space of the charged Higgs mass and the doublet-nondoublet mixing angle can arise from data on $\bbbar$, $\kkbar$ mixing and the $\e$ parameter. These constraints turn out to be comparable (and in some cases, better) to those obtained from $\zbb$ data.

hep-ph↗