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Riazuddin

Publications and source records attributed to Riazuddin.

34 records · Page 2Linked to original sources
arXiv2004

Neutrinos: recent developments and origin of neutrino mass matrix

Certainly one of the most exciting areas of research at present is neutrino physics. The neutrinos are fantastically numerous in the universe and as such they have bearing on our understanding of the universe. Therefore, we must understand the neutrinos, particularly their mass. There is compelling evidence from solar and atmospheric neutrinos and those from reactors for neutrino oscillations implying that neutrinos mix and have nonzero mass but without pinning down their absolute mass. This is reviewed. The implications of neutrino oscillations and mass squared splitting between neutrinos of different flavor on pattern of neutrino mass matrix is discussed. In particular, a neutrino mass matrix, which shows approximate flavor symmetry where the neutrino mass differences arise from flavor violation in off-diagonal Yukawa couplings is elaborated on. The implications in double beta decay are also discussed.

hep-ph↗
arXiv2004

Role of Mathematics in Physical Sciences

The role of mathematics in physical sciences is discussed, particularly how higher mathematics found applications in empirical problems. Several examples are given to illustrate this role.

math.HO↗
arXiv2003

Neutrino Mass Matrix with Approximate Flavor Symmetry

Phenomenological implications of neutrino oscillations implied by recent experimental data on pattern of neutrino mass matrix are disscussed. It is shown that it is possible to have a neutrino mass matrix which shows approximate flavor symmetry; the neutrino mass differences arise from flavor violation in off-diagonal Yukawa couplings. Two modest extensions of the standard model, which can embed the resulting neutrino mass matix have also been discussed.

hep-ph↗
arXiv2003

Ward Identities, B-> ρForm Factors and |V_ub|

The exclusive FCNC beauty semileptonic decay B-> ρis studied using Ward identities in a general vector meson dominance framework, predicting vector meson couplings involved. The long distance contributions are discussed which results to obtain form factors and |V_ub|. A detailed comparison is given with other approaches.

hep-ph↗
arXiv2003

Particle Aspects of Cosmology and Baryogenesis

An introduction to particle aspects of cosmology with particular refrence to primordial nucleosynthesis, dark matter and baryogenesis is provided. In particular, various scenarios-GUT baryogenesis, electroweak baryogenesis and baryogenesis through leptogenesis are reviewed.

hep-ph↗
arXiv2002

Role of lepton flavor violating (LFV) muon decay in Seesaw model and LSND

The aim of the work is to study LFV in a newly proposed Seesaw model of neutrino mass and to see whether it could explain LSND excess. The motivation of this Seesaw model was that there was no new physics beyond the TeV scale. By studying μ\to 3e in this model, it is shown that the upper bound on the branching ratio requires Higgs mass m_{h} of a new scalar doublet with lepton number L=-1 needed in the model has to be about 9 TeV. The predicted branching ratio for μ\to eν_{l}\barν_{l} is too small to explain the LSND. PACS: 11.30.Hv, 14.60.Pq

hep-ph↗
arXiv2002

Role of gauge invariance in B -> V gamma radiative weak decays

The role of gauge invariance in calculating B -> V gamma radiative weak decays is clarified. It is shown that the gauge invariance severely restricts the contributions mediated by the usual weak non-leptonic Hamiltonian dominated by u and c quaks with one photon attachment. Such contributions are found to be almost negligible.

hep-ph↗
arXiv2001

The sigma and rho in D and B decays

We study the D^{+} -> sigma pi^{+}, D^{+} -> rho^0 pi^{+}, B^{-} -> sigma pi^{-}, B^{-} -> rho^0 pi^{-} and \bar{B}^0 -> rho^{\pm} pi^{\mp} decays in a valence quark triangle model, incorporating chiral symmetries. We find a good agreement with recent experimental data for D^{+} -> sigma pi^{+} and for D^{+} -> rho^0 pi^{+}. We point out that a "long-distance" contribution due to the axial vector a_1 meson pole, calculated by using chiral symmetry, can be relevant to explain D^{+}-> rho^0 π^{+} and for lowering the ratio R=Br(\bar{B}^0 -> rho^{\pm} pi^{\mp})/Br(B^{-} -> rho^0 pi^{-}) to be consistent with its phenomenological determination, within the large experimental uncertainity.

hep-ph↗
arXiv2001

Potential Models for Radiative Rare B Decays

We compute the branching ratios for the radiative rare decays of B into K-Meson states and compare them to the experimentally determined branching ratio for inclusive decay b -> s gamma using non relativistic quark model, and form factor definitions consistent with HQET covariant trace formalism. Such calculations necessarily involve a potential model. In order to test the sensitivity of calculations to potential models we have used three different potentials, namely linear potential, screening confining potential and heavy quark potential as it stands in QCD.We find the branching ratios relative to the inclusive b ->s gamma decay to be (16.07\pm 5.2)% for B -> K^* (892)gamma and (7.25\pm 3.2)% for B -> K_2^* (1430)gamma for linear potential. In the case of the screening confining potential these values are (19.75\pm 5.3)% and (4.74\pm 1.2)% while those for the heavy quark potential are (11.18\pm 4.6)% and (5.09\pm 2.7)% respectively. All these values are consistent with the corresponding present CLEO experimental values: (16.25\pm 1.21)% and (5.93\pm 0.46)%.

hep-ph↗
arXiv2000

Off-diagonal structure of neutrino mass matrix in see-saw mechanism and electron-muon-tau lepton universality

By a simple extension of the standard model in which ($e-μ-τ$) universality is not conserved, we present a scenario within the framework of see-saw mechanism in which the neutrino mass matrix is strictly off-diagonal in the flavor basis. We show that a version of this scenario can accomodate the atmospheric $ν_μ-ν_τ$ neutrino oscillations and $ν_μ-ν_e$ oscillations claimed by the LSND collaboration. PACS: 14.60.Pq; 14.60.St;13.15.+g

hep-ph↗
arXiv2000

Form factors for $B-->πlν$ decay in a model constrained by chiral symmetry and quark model

The form factors for the $B-->π$ transition are evaluated in the entire momentum transfer range by using the constraints obtained in the framework combining the heavy quark expansion and chiral symmetry for light quarks and the quark model. In particular, we calculate the valence quark contributions and show that it together with the equal time commutator contribution simulate a B-meson pole q^2-dependence of form factors in addition to the usual vector meson B^{*}-pole diagram for $B --> πlν$ in the above framework. We discuss the predictions in our model, which provide an estimate of |V_{ub}|^2.

hep-ph↗
arXiv1999

Analysis of the Three-Body $B \to D^+ D^- π^0$ Decay

The decay process $B\to D^+ D^- π^0$ is an interesting channel for the investigation of CP violating effects in the $b-$ sector. We write down a decay amplitude constrained by a low-energy theorem, which also includes the contribution of resonant $S-$ and $P-$wave beauty and charmed mesons, and we determine the relevant matrix elements in the infinite heavy quark mass limit, assuming the factorization ansatz. We estimate the rate of the decay: ${\cal B}(B \to D^+ D^- π^0)\simeq 1 \times 10^{-3}$. We also analyze the time-independent and time-dependent differential decay distributions, concluding that a signal for this process should be observed at the B-factories. Finally, we give an estimate of the decay rate of the Cabibbo-favoured process $B\to D^+ D^- K_S$.

hep-ph↗
arXiv1998

Two body non-leptonic $Λ_b$ decays in quark model with factorization ansatz

The two body non-leptonic $Λ_b$ decays are analyzed in factorization approximation, using quark model, $ξ= 1 / N_c$ as a free parameter. It is shown that the experimental branching ratio for $Λ_b \longrightarrow Λ{J/ψ}$ restricts $ξ$ and this ratio can be understood for a value of $ξ$ which lies in the range $ 0 \leq ξ\leq 0.5 $ suggested by two body B meson decays. The branching ratios for $Λ_b \longrightarrow Λ_{c} D^*_s(D_s) $ are predicted to be larger than the previous estimates. Finally it is pointed that CKM-Wolfenstein parameter $ρ^2 + η^2$, where $η$ is CP phase, can be determined from the ratio of widths of $Λ_b \longrightarrow Λ\bar{D}$ and $Λ_b \longrightarrow Λ{J/ψ}$ or that of $Λ_b \longrightarrow p D_s$ and $Λ_b \longrightarrow Λ_c D_s$ independent of the parameter $ξ$.

hep-ph↗
arXiv1997

Double Counting Ambiguities in the Linear Sigma Model

We study the dynamical consequences imposed on effective chiral field theories such as the quark-level SU(2) linear $σ$ model (L$σ$M) due to the fundamental constraints of massless Goldstone pions, the normalization of the pion decay constant and form factor, and the pion charge radius. We discuss quark-level double counting L$σ$M ambiguities in the context of the Salam-Weinberg $Z = 0$ compositeness condition. Then SU(3) extensions to the kaon are briefly considered.

hep-ph↗