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M. Jamil Aslam

Publications and source records attributed to M. Jamil Aslam.

At least 55 records · Page 3Linked to original sources
arXiv2011

Analysis of B_{C} --> D_{s}^{*}l^{+}l^{-} in the Standard Model Beyond Third Generation

The weak decays of B_{c} --> D_{s}^{*}l^{+}l^{-} (l=mu,tau) are investigated in the Standard Model with fourth generation (SM4). Taking fourth generation quark mass m_{t'} of about 300 to 600 GeV with the CKM matrix elements V_{t'b}^{*}V_{t's} in the range (0.03-1.2)*10^{-2} and using the new CP odd phase (phi_{sb}) to be 90^{o} the analysis of decay rates, forward-backward asymmetries, lepton polarization asymmetries and the helicity fractions of D_{s}^{*} meson in B_{c} --> D_{s}^{*}l^{+}l^{-} (l=mu,tau) is made. It is shown that the values of these physical observables are greatly influenced by the effects of extra sequential quark generation in the SM. It is found that the zero position of the forward-backward asymmetry in B_{c} --> D_{s}^{*} mu^{+} mu^{-} deviates significantly from that of the SM value while the effects in the decay rate, helicity fractions of D_s^{*} meson and the lepton polarization asymmetries are also quite promising. In B_{c} --> D_{s}^{*} tau^{+} tau^{-} decay, the SM4 the NP effects are somewhat mild in the decay rate and forward-backward asymmetry but they have shown them up in the longitudinal and transverse lepton polarization and also in the helicity fractions of the D_{s}^{*} meson which differ distinctively from the SM values. Thus the study of these physical observables will provide us useful information to probe new physics and helps us to search for the fourth generation of quarks (t',b') in an indirect way.

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arXiv2011

Semileptonic B to Scalar meson Decays in the Standard Model with Fourth Generation

We study the effects of the fourth generation of quarks on the total branching ratio and the lepton polarizations in $\bar{B}_{0}\rightarrow K_{0}^{\ast}(1430)l^{+}l^{-}$($l$ = $μ$, $τ$) decay. Taking fourth generation quark mass $m_{t{\prime}}$ of about $400$ to $600$ GeV with the mixing angle $|V_{t^{\prime}b}^{\ast}V_{t^{\prime}s}|$ in the range $(0.05-1.4)\times 10^{-2}$ and using the phase to be $80^{o}$%, it is found that the branching ratio and lepton polarizations are quite sensitive to these fourth generation parameters. In future the experimental study of this decay will give us an opportunity to study new physics effects, precisely, to search for the fourth generation of quarks $% (t^{\prime},b^{\prime})$ in an indirect way.

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arXiv2011

Semileptonic charmed $B$ meson decays in Universal Extra Dimension Model

Form factors parameterizing the semileptonic decay $B_{c}\rightarrow D_{s}^{\ast}l^{+}l^{-}$ ($l=μ,τ$) are calculated using the frame work of Ward Identities. These form factors are then used to calculate the physical observables like branching ratio and helicity fractions of final state $D_{s}^{\ast}$ meson in these decay modes. The analysis is then extended to the the universal extra dimension (UED) model where the dependence of above mentioned physical variables to the compactification radius R, the only unknown parameter in UED model, is studied. It is shown that the helicity fractions of $D_{s}^{\ast}$ are quite sensitive to the UED model especially when have muons as the final state lepton. Therefore, these can serve as a useful tool to establish new physics predicted by the UED model.

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arXiv2011

Model Independent Analysis of the Forward-Backward Asymmetry for the $B\to K_{1}μ^{+}μ^{-}$ Decay

The sensitivity of the zero position of the forward backward asymmetry $\mathcal{A}_{FB}$ for the exclusive $B\rightarrow K_{1}(1270)μ^{+}μ^{-}$ decay is examined by using most general non-standard 4-fermion interactions. Our analysis shows that the zero position of the forward backward asymmetry is very sensitive to the sign and size of the Wilson coefficients corresponding to the new vector type interactions, which are the counter partners of the usual Standard Model operators but have opposite chirality. In addition to these, the other significant effect comes from the interference of Scalar-Pseudoscalar and Tensor type operators. These results will not only enhance our theoretical understanding about the axial vector mesons but will also serve as a good tool to look for physics beyond the SM.

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arXiv2010

Tetraquark interpretation of the BELLE data on the anomalous $Υ(1S) π^+π^-$ and $Υ(2S) π^+π^-$ production near the $Υ(5S)$ resonance

We analyze the Belle data [K. F. Chen {\it et al.} (Belle Collaboration), Phys.\ Rev.\ Lett.\ {\bf 100}, 112001 (2008); I. Adachi {\it et al.} (Belle Collaboration), arXiv:0808.2445] on the processes $e^+ e^- \to Υ(1S)\; π^+π^-, Υ(2S)\; π^+π^-$ near the peak of the $Υ(5S)$ resonance, which are found to be anomalously large in rates compared to similar dipion transitions between the lower $Υ$ resonances. Assuming these final states arise from the production and decays of the $J^{PC}=1^{--}$ state $Y_b(10890)$, which we interpret as a bound (diquark-antidiquark) tetraquark state $[bq][\bar{b}\bar{q}]$, a dynamical model for the decays $Y_b \to Υ(1S)\; π^+π^-, Υ(2S)\; π^+π^-$ is presented. Depending on the phase space, these decays receive significant contributions from the scalar $0^{++}$ states, $f_0(600)$ and $f_0(980)$, and from the $2^{++}$ $q\bar{q}$-meson $f_2(1270)$. Our model provides excellent fits for the decay distributions, supporting $Y_b$ as a tetraquark state.

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arXiv2010

A case for hidden $b\bar{b}$ tetraquarks based on $e^+e^- \to b\bar{b}$ cross section between $\sqrt{s}=10.54$ and 11.20 GeV

We study the spectroscopy and dominant decays of the bottomonium-like tetraquarks (bound diquarks-antidiquarks), focusing on the lowest lying P-wave $[bq][\bar{b}\bar{q}]$ states $Y_{[bq]}$ (with $q=u,d$), having $J^{PC}=1^{--}$. To search for them, we analyse the BABAR data \cite{:2008hx} obtained during an energy scan of the $e ^+ e^- \to b \bar{b}$ cross section in the range of $\sqrt{s}=10.54$ to 11.20 GeV. We find that these data are consistent with the presence of an additional $b \bar{b}$ state $Y_{[bq]}$ with a mass of 10.90 GeV and a width of about 30 MeV apart from the $Υ(5S)$ and $Υ(6S)$ resonances. A closeup of the energy region around the $Y_{[bq]}$-mass may resolve this state in terms of the two mass eigenstates, $Y_{[b,l]}$ and $Y_{[b,h]}$, with a mass difference, estimated as about 6 MeV. We tentatively identify the state $Y_{[bq]}(10900)$ from the $R_b$-scan with the state $Y_b(10890)$ observed by BELLE \cite{Abe:2007tk} in the process $e^+e^- \to Y_b(10890) \to Υ(1S, 2S) π^+ π^-$ due to their proximity in masses and decay widths.

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arXiv2009

$B \to K^{\ast}_0(1430) l^{+} l^{-}$ decays in supersymmetric theories

The weak decays of $B \to K^{\ast}_0(1430) l^{+} l^{-}$ ($l=μ, τ$) are investigated in Minimal Supersymmetric Standard Model (MSSM) and also in Supersymmetric (SUSY) SO(10) Grand Unified Models. Neutral Higgs bosons are the point of main focus in MSSM because they make quite a large contribution in exclusive $B \to X_{s} l^{+} l^{-}$ decays at large $\tanβ$ regions of parameter space of SUSY models, as part of SUSY contributions is proportional to $\tan^{3}β$. The analysis of decay rate, forward-backward asymmetries and lepton polarization asymmetries in $B \to K^{\ast}_0(1430) l^{+} l^{-}$ show that the values of these physical observables are greatly modified by the effects of neutral Higgs bosons. In SUSY SO(10) GUT model, the new physics contribution comes from the operators which are induced by the neutral Higgs boson penguins and also from the operators with chirality opposite to that of the corresponding Standard Model (SM) operators. SUSY SO(10) effects show up only in the decay $B \to K^{\ast}_0 μ^{+} μ^{-}$ where the transverse lepton polarization asymmetries deviate significantly from the SM value while the effects in the decay rate, forward-backward asymmetries, the longitudinal and normal lepton polarization asymmetries are very mild. The transverse lepton polarization asymmetry is almost zero in SM and in MSSM model, whereas it can reach to -0.3 in SUSY SO(10) GUT model which could be seen at the future colliders; hence this asymmetry observable can be used to discriminate between different SUSY models.

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arXiv2008

Rare decays of $Λ_b \to Λγ$ and $Λ_b \to Λl^{+} l^{-}$ in universal extra dimension model

The exclusive weak decay of $Λ_b \to Λγ$ and $Λ_b \to Λl^{+} l^{-}$ are investigated in the Applequist-Cheng-Dobrescu model, which is an extension of the standard model in presence of universal extra dimensions. Employing the transition form factors obtained in the light-cone sum rues, we analyze how the invariant mass distribution, forward-backward asymmetry and polarization asymmetry of $Λ$ baryon of these decay modes can be used to constrain the only one additional free parameter with respect to the standard model, namely, the radius $R$ of the extra dimension. Our results indicate that the Kaluza-Klein modes can lead to approximately 25% suppression of the branching ratio of $Λ_b \to Λγ$, however, their contributions can bring about 10% enhancement to the decay rate of $Λ_b \to Λl^{+} l^{-}$. It is shown that the zero-position of forward-backward asymmetry of $Λ_b \to Λμ^{+} μ^{-}$ is sensitive to the compactification parameter $R$ in this scenario, while the measurement of polarizations of $Λ$ baryon in the $Λ_b$ decays is not suitable to provide some valuable information for the universal extra dimension model.

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arXiv2008

B \to 0^{+}(1^{+}) + missing energy in Unparticle Physics

We examine the effects of an unparticle $\mathcal{U}$ as a possible source of missing energy in the p-wave decays of $B$ meson. The dependence of the differential branching ratio on the $K_{0}^{\ast}(K_{1}) -$% meson's energy is discussed in the presence of scalar and vector unparticle operators and significant deviation from the standard model value is found after addition of these operators. Finally, we have shown the dependence of branching ratio for the above said decays on the parameters of the unparticle stuff like the effective couplings, cutoff scale $Λ_{% \mathcal{U}}$ and the scale dimensions $d_{\mathcal{U}}$.

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arXiv2008

Exclusive semileptonic decays of $Λ_b \to Λl^{+} l^{-}$ in supersymmetric theories

The weak decays of $Λ_b \to Λl^{+} l^{-}$ ($l=e, μ$) are investigated in Minimal Supersymmetric Standard Model (MSSM) and also in Supersymmetric (SUSY) SO(10) Grand Unified Models. In MSSM the special attention is paid to the Neutral Higgs Bosons (NHBs) as they make quite a large contribution in exclusive $B \to X_{s} l^{+} l^{-}$ decays at large $\tanβ$ regions of parameter space of SUSY models, since part of SUSY contributions is proportional to $\tan^{3}β$. The analysis of decay rate, forward-backward asymmetries, lepton polarization asymmetries and the polarization asymmetries of $Λ$ baryon in $Λ_b \to Λl^{+} l^{-}$ show that the values of these physical observables are greatly modified by the effects of NHBs. In SUSY SO(10) GUT model, the new physics contribution comes from the operators which are induced by the NHBs penguins and also from the operators having chirality opposite to that of the corresponding SM operators. SUSY SO(10) effects show up only in the decay $Λ_b \to Λ+τ^{+} τ^{-}$ where the longitudinal and transverse lepton polarization asymmetries are deviate significantly from the SM value while the effects in the decay rate, forward-backward asymmetries and polarization asymmetries of final state $Λ$ baryon are very mild. The transverse lepton polarization asymmetry in $Λ_b \to Λ+τ^{+} τ^{-}$ is almost zero in SM and in MSSM model. However, it can reach to -0.1 in SUSY SO(10) GUT model and could be seen at the future colliders; hence this asymmetry observable will provide us useful information to probe new physics and discriminate between different models.

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arXiv2008

Scalar mesons in weak semileptonic decays of $B_{(s)}$

The transition form factors of $B_{(s)} \to S$, with $S$ denoting a scalar meson, are investigated in the light-cone sum rules approach. The numerical values are approximately twice as large as that estimated in the light-front quark model and QCD sum rules approach. Using these form factors, we present the analysis of the decay rates for $B \to a_0(1450) l \barν_l $, $B \to K^{\ast}_0(1430) l \bar{l}$, $B_s \to K^{\ast}_0(1430) l \barν_l$ and $B_s \to f_0(1500) l \bar{l}$ with $l=e, μ, τ$. The results indicate that magnitudes of $BR(\bar{B}_0 \to a_0(1450) l \barν_l)$ and $BR(B_s \to K^{\ast}_0(1430) l \barν_l)$ can arrive at the order of $10^{-4}$, which can be measured in the future experiments to clarify the inner structure of scalar mesons. It is also observed that $BR(B \to K^{\ast}_0(1430) τ^+ τ^-)$ and $BR(B_s \to f_0(1500) τ^+ τ^-)$ are an order of magnitude smaller than the corresponding channels of $e^+ e^-$ and $μ^+ μ^-$ final states due to the heavily suppressed phase space . Moreover, the longitudinal lepton polarization asymmetry for $B \to K^{\ast}_0(1430) l \bar{l}$ and $B_s \to f_0(1500) l \bar{l}$ are also investigated, whose values are close to -1 for the $e^+ e^-$ and $μ^+ μ^-$ pair except the region close to the end points.

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arXiv2008

Lepton polarization asymmetry and forward backward asymmetry in exclusive B->K_1 tau^(+)tau^(-) decay in universal extra dimension scenario

Decay rate, forward-backward asymmetry and polarization asymmetries of final state leptons in B-> K_{1}tau ^{+}tau ^{-}, where K_{1} is the axial vector meson, are calculated in Standard Model and in the universal extra dimension (UED) model. The sensitivity of the observables on the compactification radius $R$, the only unknown paramter in UED model, is studied. Finally, the helicity fractions of the final state K_{1} are calculated and their dependence on the compactification radius is discussed. This analysis of helicity fraction is briefly extended to B->K^{*}l ^{+}l ^{-}(l =e,mu) and compared with the other approaches exist in the literature

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arXiv2008

Exclusive B-> K_{1}l ^{+}l ^{-} decay in model with single universal extra dimension

Decay rate and forward-backward asymmetries in B -> K_{1} l^{+} l ^{-}, K_{1} is the axial vector meson, are calculated in the universal extra dimension (UED) model. The dependence of these physical quantities on the compactification radius $R$, the only unknown parameter in UED model, is studied and it is shown that zero of forward-backward asymmetry is sensitive to the UED model, therefore they can be very useful tool to establish new physics predicted by the UED model. This work is briefly extended to B -> K^{*}l^{+}l^{-}.

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arXiv2007

Form factors, branching ratio and forward-backward asymmetry in B -> K_{1}ell ^{+} ell ^{-} decays

We study long-distance effects in rare exclusive semileptonic decays B -> K_{1}ell ^{+}ell ^{-}, K_{1} is the axial vector meson.The form factors, describing the meson transition amplitudes of the effective Hamiltonian, are calculated using Ward identites which are then used to calculate branching ratio and forward-backward asymmetry in these decay modes. The zero of forward-backward asymmetry is of special interest and provide us the precission test of Standard model.

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arXiv2007

Form factors and branching ratio for the B -> l nu gamma decay

Form factors parameterizing radiative leptonic decays of heavy mesons $% (B^{+}\to γl^{+}ν_{l}) $ for photon energy are computed in the language of dispersion relation. The contributing states to the absorptive part in the dispersion relation are the multiparticle continum, estimated by quark triangle graph and resonances with quantum numbers $1^{-}$ and $1^{+}$ which includes $B^{*}$ and $B_{A}^{*}$ and thier radial excitations, which model the higher state contributions. Constraints provided by the asymptotic behavior of the structure dependent amplitude, Ward Identities and gauge invariance are used to provide useful information for parameters needed. The couplings $g_{BB^{*}γ}$ and $% f_{BB_{A}^{*}γ}$ are predicted if we restrict to first radial excitation; otherwise using these as an input the radiative decay coupling constants for radial excitations are predicted. The value of the branching ratio for the process $B^{+}\to γμ^{+}ν_μ$ is found to be in the range $0.5\times 10^{-6}$. A detailed comparison is given with other approaches.

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arXiv2006

Branching Ratio and CP-asymmetry for B-> 1^{1}P_{1}gamma decays

We calculate the branching ratios for B_{d}^{0}->(b_{1},h_{1})gamma at next-to-leading order (NLO) of alpha_{s} where b_{1} and h_{1} are the corresponding radially excited axial vector mesons of rho and omega respectively. Using the SU(3)symmetry for the form factor, the branching ratio for B_{d}^{0}->(b_{1},h_{1})gamma is expressed in terms of the branching ratio of the B_{d}^{0}-> K_{1}gamma and it is found to be B(B_{d}^{0}->b_{1}gamma)=0.71* 10^{-6} and B(B_{d}^{0}-> h_{1}gamma) =0.74*10^{-6}. We also calculate direct CP asymmetry for these decays and find, in confirmity with the observations made in the literature, that the hard spectator contributions significantely reduces the asymmetry arising from the vertex corrections alone. The value of CP-asymmetry is 10% and is negative like rho and omega in the Standard Model.

hep-ph↗
arXiv2006

Annihilation Contributions in B -> K_1 gamma decay in next-to-leading order in LEET and CP-asymmetry

The effect of weak annihilation and u-quark penguin contribution on the branching ratio B -> K_1 gamma at next-to-leading order of alpha_s are calculated using LEET approach. It is shown that the value of LEET form factor remains the same in the range of unitarity triangle phase alpha favored by the Standard Model. CP-asymmetry for above mentioned decay has been calculated and its suppression due to the hard spectator correction has also been incorporated. In addition, the sensitivity of the CP-asymmetry on the underlying parameters has been discussed.

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