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Fayyazuddin

Publications and source records attributed to Fayyazuddin.

At least 19 recordsLinked to original sources
arXiv2022

W-exchange contribution in hadronic decays of bottom baryon

The nonleptonic decays of \Lambda_{b} that are dominated by W exchange are studied. In particular, the decay modes \varLambda_{b}\to\varDelta^{0}D^{0},\varDelta^{-}D^{+},\Sigma^{*-}D_{s}^{+}, \Lambda_{b}\to\Sigma_{c}^{*+}\pi^{-},\Sigma_{c}^{*0}\pi^{0},\Xi_{c}^{*0}K^{0} and \varLambda_{b}\to\Sigma_{c}^{+}\pi^{-} are analyzed. In an another aspect, the decay \Lambda_{b}\to\Lambda_{c}^{+}\pi^{-} in the factorization anstaz is studied. It is shown that factorization contributes to parity-violating (s-wave) amplitude A only. Hence factorization gives asymmetry parameter \alpha=0. However, the dominant contribution to parity conserving (p-wave) amplitude B comes from W exchange, i.e., from the baryon pole, giving asymmetry parameter \alpha=-0.77.

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arXiv2021

W exchange contributions in hadronic decays of charmed baryons

The nonleptonic decays of $\Xi_c^0$ and $\Lambda_c^+$ that are dominated by $W$-exchange are studied. In particular, we anlayse the decay modes $\Xi_c^0 \rightarrow \Xi^{*-} \pi^+, \Sigma^{*+}K^-, \Omega^-K^+$ and $\Lambda_c^+\rightarrow \Sigma^0\pi^+, \Xi^0 K^+$, $\Xi^0_c\rightarrow \Sigma^+K^-$.

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arXiv2021

W-exchange contributions in hadronic decays of bottom baryon $\Lambda_{b}$

The nonleptonic decays $\Lambda_{b}\rightarrow\Sigma_{c}^{*-}\pi^{+},\Xi_{c}^{*0}K^{0}$ and $\Lambda_{b}\rightarrow\Delta^{0}D^{0},\Sigma^{*-}D_{0}^{+}$ are studied. In addition, the decays $\Lambda_{b}\rightarrow\Xi_{c}^{0}K^{0},\Sigma^{-}D_{s}^{+}$ are analyzed. For all these decays the dominant contribution comes from $W-$exchange, and for the decay $\Lambda_{b}\rightarrow\Lambda_{c}^{+}\pi^{-}$, in addition to factorization, baryon pole contribution to the $p$-wave (parity conserving) decay amplitude $B$ is discussed.

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arXiv2020

Radiative Baryonic Decay $\mathcal{B}^{*}\left(\frac{3}{2}\right)\to\mathcal{B}\left(\frac{1}{2}\right)+\gamma$ in Constituent Quark Model: A Tutorial

The radiative baryonic decay $\mathcal{B}^{*}\left(\frac{3}{2}\right)\to\mathcal{B}\left(\frac{1}{2}\right)+\gamma$ is a magnetic dipole $(M1)$ transition. It requires the transition magnetic moment $\mu_{\mathcal{B}\left(3/2\right)\to\mathcal{B}\left(1/2\right)}$. The transition magnetic moments for the helicities $1/2$ and $3/2$ are evaluated in the frame work of constituent quark model in which the intrinsic spin and the magnetic moments of quarks $u,d$ and $s$ play a key role. Within this framework, the radiative decays $\Delta^{+}\to p +\gamma$, $\Sigma^{*0}\to \Lambda+\gamma$, $\Sigma^{*+}\to \Sigma^{+}+\gamma$ and $\Xi^{*0}\to \Xi^{0}+\gamma$ are analyzed in detail. The branching ratio for these decays is found to be in good agreement with the corresponding experimental values.

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arXiv2019

Neutrino Mass Matrix in a gauge group $SU(2)_L \times U(1)_e \times U(1)_\mu \times U(1)_\tau$

The electroweak unification group $G\equiv SU(2)_L\times U(1)_e\times U(1)_\mu\times U(1)_\tau$ in which each fermion multiplet has its own $U(1)$ factor was proposed in 1986 to get the neutrino mass matrix. In this paper, the gauge group G is restricted to lepton section only, leaving quark multiplets as in the standard model. In addition to lepton multiplets $L_e$, $L_\mu$ and $L_\tau$, there are three $SU(2)$singlet right handed neutrinos $N_{R}^{(i)}$'s. WIth the breaking of G to $SU(2)_L\times U(1)$, the right handed neutrinos acquire heavy Majorana masses. Three heavy right handed neutrinos $N_{R}^{(i)}$'s are available to generate a $3\times 3$ non-diagonal neutrino mass matrix in terms of three Yukawa couplings $h^{(2)}_{1}$, $h^{(3)}_{2}$, $h^{(1)}_{3}$ of the Higgs scalar doublet to $L_e$, $L_\mu$, $L_\tau$ with $N_{R}^{(1)}$, $N_{R}^{(2)}$ and $N_{R}^{(3)}$ respectively. Three Yukawa couplings can be arranged and expressed in terms of masses $m_e$, $m_\mu$, $m_\tau$ in three different ways to obtain the results of interest for Case 1: ($\nu_e \rightarrow \nu_\tau$); Case 2: ($\nu_e \rightarrow \nu_\mu$); Case 3: ($\nu_\mu \rightarrow \nu_\tau$). The results obtained for the three cases are compared with the experimental data from neutrino oscillations. Cases 1 and 2 are relevant for solar neutrino oscillations whereas Case 3 is relevant for atmospheric neutrino oscillations.

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arXiv2018

Lepton Flavor Violating Decays of $B$ and $K$ Mesons in Models with Extended Gauge Group

Lepton Flavor Violating (LFV) decays are forbidden in the Standard Model (SM) and to explore them one has to go beyond it. The flavor changing neutral current induced Lepton Flavor Conserving and LFV decays of $K$ and $B$ mesons are discussed in the gauge group $G = SU(2)_L\times U(1)_{Y_1}\times SU(2)_X$. The lepto-quark $X^{\pm 2/3}_{\mu}$ corresponding to gauge group $ SU(2)_X$ allows the quark-lepton transitions and hence giving a framework to construct the effective Lagrangian for the LFV decays. The mass of lepto-quark $m_{X}$ provides a scale at which the gauge group $G$ is broken to the SM gauge group. Using the most stringent experimental limit $\mathcal{B}(K^{0}_{L}\to \mu^{\mp}e^{\pm}) < 1.7 \times 10^{-12}$, the upper bound on the effective coupling constant $(\frac{G_{X}}{G_F})^2 < 1.1 \times 10^{-10}$ is obtained for certain pairing of lepton and quark generations in the representation $(2, \bar{2})$ of the group $G$. Later, the effective Lagrangian for the LFV meson decays for the gauge group $G = \left[SU(2)_{L}\times SU(2)_{R}\times U(1)_{Y_1^{\prime}}\right]\times SU(2)_{X}$ is constructed. Using $\mathcal{B}(K^{-} \to \pi^{-}\nu \bar{\nu}) = (1.7 \pm 1.1)\times 10^{-10}$, the bound on the ratio of effective couplings is obtained to be $\left(\frac{G_{X}}{G_{F}}\right)^2 < 10^{-10}$. A number of decay modes are discussed which provide a promising area to test this model in the current and future particle physics experiments.

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arXiv2017

Hadronic Weak Decay $\mathcal{B}_{b}(\frac{1}{2}^+) \to \mathcal{B}(\frac{1}{2}^{+},\; \frac{3}{2}^{+}) +V$

It is shown that for the effective Lagrangian with factorization ansatz considered here, the two body hadronic decay $\mathcal{B}_{b}(\frac{1}{2}^+) \to \mathcal{B}(\frac{1}{2}^{+},\; \frac{3}{2}^{+}) + V$, for $\mathcal{B}_{b}(\frac{1}{2}^{+})$ belonging to the representation $\bar{3}$, only allowed decay channel is $\mathcal{B}_{b}(\frac{1}{2}^+) \to \mathcal{B}(\frac{1}{2}^{+})+ V$, where $\mathcal{B}(\frac{1}{2}^{+})$ belongs to the representation $8$ of $SU(3)$. However, for $\mathcal{B}_{b}(\frac{1}{2}^{+})$ belonging to the sextet representation $6$, the allowed decay channels are $\mathcal{B}_{b}(\frac{1}{2}^+) \to \mathcal{B}(\frac{1}{2}^{+},\; \frac{3}{2}^{+}) + V$, where $\mathcal{B}(\frac{1}{2}^{+})$ and $\mathcal{B}(\frac{3}{2}^{+})$ belongs to the octet representation $8^{\prime}$ and the decuplet $10$ of $SU(3)$, respectively. The decay channel $\mathcal{B}_{b}(\frac{1}{2}^+) \to \mathcal{B}(\frac{1}{2}^{+}) + V$ is analyzed in detail. The decay rate ($\Gamma$) and the asymmetry parameters $\alpha\;, \alpha^{\prime}\;, \beta\;, \gamma$ and $\gamma^{\prime}$ are expressed in terms of four amplitudes. In particular for the decay $\Lambda_b \to \Lambda + J/\psi$ it is shown that within the factorization framework, using heavy quark spin symmetry, the decay rate and the asymmetry parameters can be expressed in terms of two form factors $F_1$ and $F_{2}/F_{1}$, which are to be evaluated in some model. For other heavy quarks belonging to the triplet and sextet representation, the results can be easily obtained by using $SU(3)$ symmetry and phase space factor. Finally, the decay $\Omega_{b}^{-} \to \Omega^{-} + J/\psi$ is analyzed within the factorization framework. It is shown that the asymmetry parameter $\alpha$ in this particular decay is zero. The branching ratio obtained in the first approximation is compared with the experimental value.

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arXiv2017

Two Body Hadronic Decays $\Lambda_{b}(\frac{1}{2}^{+})\rightarrow B^{\ast}(\frac{3}{2}^{+})+P$ in a quark model

The framework under which decays $\Lambda_{b}(\frac{1}{2}^{+})\rightarrow B(\frac{1}{2}^{+})+M$ are analyzed is not applicable for the decays $\Lambda_{b}(\frac{1}{2}^{+})\rightarrow B^{\ast}(\frac{3}{2} ^{+})+M$. These decays occur through a baryon pole $\Sigma^{0}_{c}$ which is generated by the W-exchange diagram in the process $b+u \xrightarrow {W} c+d$. The effective Hamiltonian which arises from the W-exchange diagram is expressed in the non relativistic limit. Since $% \Sigma^{0}_{c}$ belongs to representation $6$ of SU(3), it contributes to two sets of decays: $\Lambda_{b}\rightarrow\Delta^{0}D^{0},\Delta^{-}D^{+},% \Sigma^{*-}D_s^{+}$ and $\Lambda_{b}\rightarrow\Sigma^{\ast-}_{c}\pi^{+},% \Sigma^{\ast 0}_{c}\pi^{0}\;, \Xi^{\ast 0}_{c}K^{0}$. The branching ratios for these decays are evaluated which can be compared with their experimental values when the data become available. Other prediction of the model is that asymmetry parameter $\alpha = 0$, since baryon pole contributes to parity conserving (p-wave) amplitude and does not contribute to parity violating (d-wave) amplitude.

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arXiv2016

Lepton flavour violating decays of $\mu$ and $\tau$ lepton in a gauge group $SU_L(2)\times SU_R(2)\times SU_l(2)$

The electroweak unification group $ SU(2)_L\times SU(2)_R\times SU(2)_Y $ is proposed for the charged lepton flavor violating decays of the muon ($\mu$) and tau ($\tau$) leptons. The group $SU(2)_Y$ is in the lepton space. The left-handed leptons and anti-leptons are assigned to the fundamental representation $(2,2,\bar{2})$ of the semi-simple group. The gauge group $SU(2)_Y$ is spontaneously broken to $U(1)_{Y_1}$, where $Y_1=-L=\pm1$ is the hypercharge, by introducing a scalar multiplet $\Sigma$ which belongs to the triplet representation 3 of the $SU(2)_Y$ and is singlet under $SU(2)_L\times SU(2)_R$. At this stage charged vector bosons $Y^\pm$ of $SU(2)_Y$ which mediate the lepton flavor violating decays acquire masses and are decoupled with one Higgs scalar $H_\Sigma^0$. The residual group $SU(2)_L\times SU(2)_R\times U(1)_{Y_1}$ has all the features of the left-right electroweak unification group extensively studied in the literature. The probability for lepton flavor violating decays is $\left(\frac{\sin^2\theta_W}{1-2\sin^2\theta_W}\right)^2\left(\frac{m_{W_L}}{m_Y}\right)^4$.

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arXiv2012

Lepton flavor violating decays of mesons to lepton-pairs in a gauge group $SU_L(2)\times U_{Y_1}(1) \times SU_X(2)$

The lepton flavor conserving and lepton flavor violating decays of $K$ and $B$ mesons to lepton pairs in the gauge group $G=SU_L(2)\times U_{Y_1}(1) \times SU_X(2)$ are discussed. The quark-lepton transitions mediated by the lepto-quark bosons $X_{\mu}^{\pm2/3}$ of the group $SU_{X}(2)$ provide a framework to construct an effective Hamiltonian for these decays. The effective coupling constant $\frac{G_{X}}{\sqrt{2}}=\frac{g^{2}_{X}}{8m^{2}_{X}}$; $m_{X}$ is the mass at which the group $G$ is broken to the SM group. The upper bound on ($G_{X}/G_{F}$)is obtained from the most stringent experimental limit on the $B.R(K^{0}_{L}\to \mu^{\mp}e^{\pm})$. Several cases of pairing three generations of leptons and quarks in the representation $(2,\bar{2})$ of the group are analyzed. For some pairing, the upper bound on $(G_{X}/G_{F})$ is of the order $(6-9)\times 10^{-6}$ and is compatible with the upper limits on various LF violating $K$-decays . In particular for these cases, we find the upper limit on the branching ratio $B.R(K^{0}_{L}\to\mu^{-}\mu^{+})\sim (1.9-8.3)\times10^{-9}$. It is shown that for LF violating B-decays to lepton pairs, the time integrated decay rate $B^{0}_{d,s}\to\ell^{-}\tau^{+}(\tau^{-}\ell^{+})$ is a promising area to test the model.

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arXiv2011

Electroweak unification of quarks and leptons in a gauge group $SU_{C}(3)\times SU(4)\times U_{X}(1)$

A model for electroweak unification of quarks and leptons, in a gauge group $SU_{C}(3)\times SU(4)\times U_{X}(1)$ is constructed. The model requires, three generations of quarks and leptons which are replicas (mirror) of the standard quarks and leptons. The gauge group $SU(4)\times U_{X}(1)$ is broken in such a way so as to reproduce standard model and to generate heavy masses for the vector bosons ($W^{\pm}_{R_{\mu}}$, $Z^{\prime}_{\mu}$,$Z^{\prime\prime}_{\mu}$), the leptoquarks and mirror fermions. It is shown lower limit on mass scale of mirror fermions is $m_{E}\geq\frac{m_{Z}}{2}$, $E^{-}$ being the lightest mirror fermion coupled to Z boson. As the universe expands, the heavy matter is decoupled at an early stage of expansion and may be a source of dark matter. Leptoquarks in the model connect the standard model and mirror fermions. Baryon genesis in our Universe implies antibaryon genesis in mirror Universe.

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arXiv2011

Particle Mixing and CP-Violation

In this review, the $X^{0}-\bar{X}^{0}$\ mixing ($% X^{0}=B^{0},B_{s}^{0},K^{0}$) and its implication for CP\ violation in the standard model are discussed. Both direct and mixing induced CP\ violation for $K^{0}(\bar{K}^{0})$, $B^{0}(\bar{B}^{0})$\ and $B_{s}^{0}(% \bar{B}_{s}^{0})$\ are reviewed.

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arXiv2009

CP-Violation in B_{q} Decays and Final State Strong Phases

Using the unitarity, SU(2) and $C$-invariance of hadronic interactions, the bounds on final state phases are derived. It is shown that values obtained for the final state phases relevant for the direct CP-asymmetries $A_{CP}(B^{0}\to K^{+}\pi ^{-},K^{0}\pi ^{0})$ are compatiable with experimental values for these asymmetries. For the decays $B^{0}\to D^{(\ast)-}\pi ^{+}$ $(D^{(\ast)+}\pi ^{-})$ described by two independent single amplitudes $A_{f}$ and $A_{\bar{f}}^{\prime}$ with differnt weak phases (0 and $\gamma $) it is argued that the $C$-invariance of hadronic interactions implies the equality of the final state phase $\delta_{f}$ and $\delta_{\bar{f}}^{\prime}$. This in turn implies, the CP-asymmetry $% \frac{S_{+}+S_{-}}{2}$ is determined by weak phase ($2\beta +\gamma)$ only whereas $\frac{S_{+}-S_{-}}{2}=0.$ Assuming factorization for tree graphs, it is shown that the $B\to D^{(\ast)}$ form factors are in excellent agreement with heavy quark effective theory. From the experimental value for $(\frac{S_{+}+S_{-}}{2})_{D^{\ast}\pi},$ the bound $% \sin (2\beta +\gamma)\geq 0.69$ is obtained and $(\frac{S_{+}+S_{-}}{2%}) _{D_{S}^{\ast -}K^{+}}\approx -(0.41\pm 0.08)\sin \gamma $ is predicted. For the decays described by the amplitudes $A_{f}\neq A_{\bar{f}}$ such as $B^{0}\longrightarrow \rho ^{+}\pi ^{-}:$ $A_{\bar{f}}$ and $% B^{0}\longrightarrow \rho ^{-}\pi ^{+}:A_{f}$ where these amplitudes are given by tree and penguin diagrams with differnt weak phases, it is shown that in the limit $\delta_{f,\bar{f}}^{T}\to 0,r_{f,\bar{f}}\cos \delta_{f,\bar{f}}=\cos \alpha $ and $\frac{S_{\bar{f}}}{S_{f}}=\frac{% S+\Delta S}{S-\Delta S}=-\frac{\sqrt{1-C_{\bar{f}}^{2}}}{\sqrt{1-C_{f}^{2}}}% . $

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arXiv2008

$SU_{L}(4)\times U(1)$ model for electroweak unification and sterile neutrinos

Some of basic problems in neutrino physics such as new energy scales, the enormous gap between neutrino masses and the lightest charged fermion mass, possible existance of sterile neutrinos in eV mass range are studied in the local gauge group $SU_{L}(4)\times U(1)$ for electroweak unification, which does not contain fermions with exotic electric charges. It is shown that neutrino mass spectrum can be decoupled from that of the other fermions. Further normal seesaw mechanism for neutrinos, with right handed neutrino Majorana masses to be of order $M\gg M_{\text{weak}}$ as well a new eV-scale can be accomodated. The eV-scale seesaw may manifest itself in experiments like Liquid Scintilation Neutrino Detector (LSND) and MiniBooNE (MB) experimental results and future neutrino experiments.

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arXiv2007

Baryon Modes of B Meson Decays

The baryon decay modes of B,bar{B}-> N_{1}bar{N}_{2}(f), bar{N}_{1}N_{2}(bar{f}) provide a frame work to test CP-invariance in baryon sector. It is shown that in the rest frame of B, N_{1} and bar{N}_{2} come out with longitudnal polarization lambda_{1}=lambda_{2}=\pm 1 with decay width Gamma_{f}=Gamma_{f}^{++}+Gamma_{f}^{--} and the asymmetry parameter alpha _{f}=ΔΓ_{f}=Γ_{f}^{++}-Gamma_{f}^{--} . It is shown that CP invariance prediction alpha_{f}=-\bar{alpha}_{bar{f}} can be tested in these decay modes; especially in the time dependent decays of B_{q}^{0}-bar{B}_{q}^{0} complex. Apart from this, it is shown that decay modes B(bar{B})->N_{1}bar{N}_{2}(bar{N}_{1}N_{2}) and subsequent non leptonic decays of N_{2},bar{N}_{2} or (N_{1},bar{N}_{1}) into hyperon (antihyperon) also provide a frame work to study CP-odd observables in hyperon decays.

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arXiv2007

SU(3) and CP violating weak and strong final state phases for B_{d}^{0} and B_{s}^{0} decays

Using rotation in SU(3) space, a set of relations between various decay modes of B_{d} and B_{s} are derived. The decays bar{B}_{d}^{0}-> K^{*-}pi ^{+}(rho ^{+}K^{-}), bar{B}_{s}^{0}-> K^{*-}K^{+} are expressed in terms of decay parameters of bar{B}_{d}^{0}->rho ^{-}pi ^{+}(rho ^{+}π^{-}). In particular the parameters r_{-+}(r_{+-}) of B_{d}->rho πdecays are obtained in terms of experimentally known decay rates R_{-+}(R_{+-})=frac{1}{2}left(Gamma_{rho ^{+}pi ^{-}(rho ^{-}pi ^{+})}+\ar{\amma}_{\ho ^{-}pi ^{+}(rho ^{+}pi ^{-})}), $ R_{-+}^{prime}(R_{+-}^{prime})=frac{1}{2}left(Gamma_{K^{*+}pi ^{-}(rho ^{-}K^{+})}+bar{Gamma}_{K^{*-}π^{+}(rho ^{+}K^{-})}), known parameters bar{lambda}, f_{K^{*}}/f_{rho}(f_{K}/f_{pi}) and two parameters B_{-+}=frac{R_{-+}}{left| T^{-+}right| ^{2}},B_{+-}=frac{R_{+-}}{| T^{+-}| ^{2}} which are determined by using factorization for tree amplitudes T^{-+} and T^{+-}. We find r_{-+}=0.21pm 0.04,r_{+-}=0.25pm 0.06. With these values the following bounds on left(z\equiv \cos γ\cos δ, x=\sin γsin δ) are derived: [-0.34(-0.33)\leq z_{-+}(z_{+-})\leq 0.28(0.27) ] and [0.16(0.43)\leq x_{-+}(x_{+-})\leq 0.58(1.00) ] From (x,z) plot we obtain following bounds on weak phase gamma and strong phases δ^{prime}s z_{-+}>0,gamma geq 70^{circ},10^{circ} leq δ_{-+}\leq 40^{circ}, z_{-+}<0,gamma geq 65^{\circ},$ $(180-δ_{-+})$. For $δ_{+-}$ we get $25^{\circ}leq δ_{+-}\leq 90^{circ} or (180-delta_{+-}).

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arXiv2007

B->rho pi decays and final state phases

Using the isospin analysis, the fact that penguin is pure Delta I=1/2 transition, the unitarity for tree graph and C-invariance of strong interactions, it is shown that delta_{t}=0=tilde{delta}_{t}, r_{-0}=tr_{0-},delta_{-0}-delta_{0-}=pm pi, 2tr_{f}r_{\bar{f}}\cos (δ_{f}-δ_{bar{f}})=(r_{f}^{2}+t^{2}r_{bar{f}}^{2})-r_{-0}^{2}, where delta 's are final state phases and r's are penguin to tree ratios defined in the text. Using the factorization for tree graph as input and the experimental data, we have obtained the following bounds on r_{f},r_{bar{f}},delta_{f} and delta_{bar{f}}:0.11leq r_{f}leq 0.21,0.18leq r_{bar{f}}leq 0.30; 11^{circ}leq delta_{f}\leq 57^{circ},23^{circ}leq delta_{bar{f}}leq 90^{circ} for the case z_{f,bar{f}}=cos alpha cos delta_{f,bar{f}}<0. For z_{f}<0 and z_{\bar{f}}>0, we obtain the following bounds for r_{bar{f}} and delta_{bar{f}}:0.14leq r_{bar{f}}leq 0.46; 90^{circ}leq delta_{bar{f}}leq 170^{circ}. From experimental data, for the decays B^{-}->rho ^{-}pi ^{0}(rho ^{0}pi ^{-}) we get epsilon_{-0}=0.28pm 0.10,epsilon_{0-}=0.51pm 0.10, frac{A_{CP}^{-0}}{A_{CP}^{0-}}=-0.8\pm 0.1 i.e. A_{CP}^{-0} and A_{CP}^{0-} have opposite sign, where 1+epsilon_{0-},_{0-}=frac{left| T^{-0,0-}+C^{0-,-0}right|}{left| T^{-0,0-}|}. In the naive quark model the above values imply a_{2}/a_{1}=0.39\pm 0.14 and a_{2}/a_{1}=0.37\pm 0.07 consistent with each other.

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