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A. N. Kamal

Publications and source records attributed to A. N. Kamal.

At least 19 recordsLinked to original sources
arXiv1999

Helicity and partial wave amplitude analysis of D -> K^* ρdecay

We have carried out an analysis of helicity and partial-wave amplitudes for the process D -> K^* ρin the factorization approximation using several models for the form factors. All the models, with the exception of one, generate partial-wave amplitudes with the hierarchy $\mid S\mid >\mid P\mid >\mid D\mid$. The one exception gives $\mid S \mid >\mid D \mid >\mid P \mid$. Even though in most models the D-wave amplitude is an order of magnitude smaller than the S-wave amplitude, its effect on the longitudinal polarization could be as large as 30%. Due to a misidentification of the partial-wave amplitudes in terms of the Lorentz structures in the relevant literature, we cast doubt on the veracity of the listed data, particularly the partial-wave branching ratios. (PACS numbers: 13.25.-k, 13.25.Ft)

hep-ph↗
arXiv1999

Resonant final-state interactions in D^0 -> \bar{K}^{0} η, \bar{K}^{0} η' Decay

We have investimated the effect of the isospin 1/2, J^P = 0^+ resonant state K^*_0(1950) on the decays D^0 ->\bar{K}^{0}ηand D^0 ->\bar{K}^0 η' as a function of the branching ratio sum r =Br(K^*_0(1950)->\bar{K}^0η)+ Br(K^*_0(1950)->\bar{K}^0 η' and coupling constants g_{K^*_0\bar{K}^0η}, g_{K^*_0\bar{K}^0η'}. We have used a factorized input for D^0 -> K^*_0(1950) weak transition through a πK loop. We estimated both on- and off-shell contributions from the loop. Our calculation shows that the off-shell effects are significant. For $r\geq 30%$ a fit to the decay amplitude A(D^0 -> \bar{K}^0 η') was possible, but the amplitude A(D^0 ->\bar{K}^0 η) remained at its factorized value. For small values of r, $r\leq 18 %$, we were able to fit A(D^0 -> \bar{K}^0 η), and despite the fact that A(D^0 -> \bar{K}^0 η') could be raised by almost 100 % over its factorized value, it still falls short of its experimental value. A simultaneous fit to both amplitudes A(D^0 -> \bar{K}^0 η') and A(D^0 -> \bar{K}^0 η) was not possible. We have also determined the strong phase of the resonant amplitudes for both decays. PACS numbers:13.25.Ft, 13.25.-k, 14.40.Lb

hep-ph↗
arXiv1999

Long-range two-body final-state interactions and direct CP asymmetry in {B}^{+}\toπ^{+} {K}^{0} decay

We present a calculation of the direct CP asymmetry, $A_{CP}^{dir}$, for the process $B^+ \to π^+ K^0$ including the effects of long-range inelastic final-state interactions (FSI). We admit three channels in our calculation: $B^+ \to (π^+ K^0), (ηK^+)$, and $(D_s^+ \bar{D}^0)$. The strong scattering is described in terms of Pomeron and Regge exchanges. We find that the direct CP asymmetry is enhanced by a factor of $\sim 3$ as a result of FSI, but remains well short of the claims of (10 - 20)% in recent literature. A critical assessment of papers claiming large CP asymmetries is also presented.

hep-ph↗
arXiv1999

Factorization and Nonfactorization in B Decays

Using NLL values for Wilson coefficients and including the contributions from the penguin diagrams, we estimate the amount of nonfactorization in two-body hadronic B decays. Also, we investigate the model dependence of the nonfactorization parameters by performing the calculation using different models for the form factors. The results support the universality of nonfactorizable contributions in both Cabibbo-favored and Cabibbo-suppressed B decays.

hep-ph↗
arXiv1999

Nonfactorization in Cabibbo-Favored B Decays

We assume universal values for the color-singlet ($ε_1$) and color octet ($ε_8$) nonfactorization parameters in B Decays. Two sets of color-favored processes and one set of color-suppressed processes were used to give quantitative estimates of these parameters. It has been found (by calculating the branching ratios for a large number of Cabibbo-favored B Decays) that the values $ε_1(μ_0) = - 0.06 +/- 0.03$ and $ε_8(μ_0) = 0.12 +/- 0.02$ improve significantly the predictions of the factorization model.

hep-ph↗
arXiv1998

$πΛ$ scattering phase shifts and CP violation in $Ξ\to πΛ$ decay

CP-violating signals in weak $ Ξ\to πΛ$ decay require the knowledge of $πΛ$ $S$- and $P$-wave scattering phases at ${m}_Ξ$ center-of-mass energy. We have calculated these phases in baryon chiral perturbation theory with the ground-state $Σ$ in $s$ and $u$ channels and ${3 \over 2}^{+}$ $Σ(1385)$ in the $u$ channel. We do not treat the baryons as heavy. We find $δ_{S} = {1.2}^{\circ}$ and $δ_{P} = -{1.7}^{\circ}$ with the central value of the strong coupling parameter $D$. We also investigate the variation of the scattering phases as functions of the parameter $D$. We compare this result with previous calculations, and discuss its relevance to CP-asymmetry parameters.

hep-ph↗
arXiv1998

Nonfactorization and Final State Interactions in (B, B_s) --> ψP and ψV Decays

Available experimental data on decay rates for B --> ψK, and decay rates and transversity amplitudes for B --> ψK^* are used to investigate nonfactorization contributions in these decays using five different theoretical models for the formfactors. Using the knowledge on nonfactorization so gained, we study the processes B_s --> ψ(η, η'), B_s --> ψϕand B --> ψ(2S) K^*. We find that present experimental data for the last two processes are consistent with the predictions of most of the models considered.

hep-ph↗
arXiv1997

Final-State Interactions in Heavy Quark Decays

We study the role played by the final-state interactions (fsi) in heavy quark decays using Pomeron and Regge exchanges to describe high energy scattering. At center of mass energy $\sqrt{s}\sim 5GeV $, Pomeron dominance does not apply. We study the behavior of the decay amplitudes as $\sqrt{s} $ is varied close to the B mass. We also investigate the behavior of the decay amplitude as $\sqrt{s}\to \infty $. Our conclusion is that the decay amplitudes approach a real value asymptotically.

hep-ph↗
arXiv1997

CP Asymmetries in Single Isospin Channels in B Decays and the Role of Inelastic Final State Interactions

The role of inelastic final state interactions in CP asymmetries is investigated in single isospin two-body hadronic decays of the B meson. We demonstrate that in a channel where the CP asymmetry vanishes in absence of inelastic final state interactions, a coupling to a second channel where the asymmetry is nonvanishing can result in an asymmetry in the first channel of the same order as in the second.

hep-ph↗
arXiv1997

Direct CP Violation Asymmetries in Exclusive B Decays in a Bethe-Salpeter Approach

CP asymmetry in some exclusive decays of charged B meson are calculated in a Bethe-Salpeter approach. Hadronic final state interactions are ignored. Complex decay amplitudes are assumed to arise entirely from perturbative quark-antiquark loops. Calculations are done both with and without the gluon quark-antiquark vacuum polarization loops. The effects of neglecting the imaginary parts arising from the diagonal quark-antiquark loops are also studied.

hep-ph↗
arXiv1996

Non-Factorization in $(B, B_s) \to P(V) ψ$ Decays

Available experimental data on decay rate and polarization are used to investigate non-factorization contribution to processes of the kind $B \rightarrow K ψ$, and $B \rightarrow K^* ψ$ using five theoretical models for the formfactors. Using the knowledge on non-factorization gained from $B$ decays we study the processes $B_s \rightarrow (η', η) ψ$, and $B_s \rightarrow ϕψ$ where experimental data are very limited.

hep-ph↗
arXiv1996

What are effective $a_1$ and $a_2$ in two-body hadronic decays of D and B mesons?

Through a specific example of two-body color-favored charm decay, $D_s ^+ \rightarrow ϕπ^+$, we illustrate how an effective and complex (unitarized) $a_1$, denoted by $a_1^{U,eff}$, may be defined such that it includes nonfactorized, annihilation and inelastic final state interaction (fsi) effects. The procedure can be generalized to color-suppressed processes to define an effective, and complex $a_2^{U,eff}$. We determine $|a_1^{U,eff}|$ and, where relevant, $|a_2^{U,eff}|$ for $D\rightarrow \bar{K}π, \bar{K} ρ, \bar{K}^{*} π, D_s^+ \rightarrow ηπ^+$, $η' π^+$, $ηρ^+ ,η' ρ^+$, and for $B^0 \rightarrow D^- π^+$ and $D^- ρ^+$ from the hadronic and semileptonic decay data.

hep-ph↗
arXiv1995

Nonfactorization in B and D decays

We discuss the role of nonfactorized contributions in $B \rightarrow ψ+ {K}^{*} $ and charmed meson decays. We demonstrate, using $ {D}^{+}_{S} \rightarrow ϕπ$ as a model, how nonfactorization, annihilation and final state interactions can be built into effective and unitarized $ {a}_{1} $ and $ {a}_{2} $.

hep-ph↗
arXiv1995

Nonfactorization in Hadronic Two-body Cabibbo-favored decays of D^0 and D^+

With the inclusion of nonfactorized amplitudes in a scheme with $N_c=3$, we have studied Cabibbo-favored decays of $D^0$ and $D^+$ into two-body hadronic states involving two isospins in the final state. We have shown that it is possible to understand the measured branching ratios and determined the sizes and signs of nonfactorized amplitudes required.

hep-ph↗
arXiv1995

Nonfactorization and the decays $D_s^+ \to ϕπ^+, ϕρ^+$ and $ϕl^+ ν_l$

In six chosen scenarios for the $q^2$ dependence of the form factors involved in $D_s^+ \rightarrow ϕ$ transition, we have determined the allowed domain of $x = A_2(0) / A_1(0)$ and $y = V(0)/A_1(0)$ from the experimentally measured ratios $R_{sl} = Γ(D_s^+ \rightarrow ϕl^+ ν_l)/Γ(D_s^+ \rightarrow ϕπ^+)$ and $R_h = Γ(D_s^+ \rightarrow ϕρ^+)/Γ(D_s^+ \rightarrow ϕπ^+)$ in a scheme that uses the $N_c =3$ value of the phenomenological parameter $a_1$ and includes nonfactorized contribution. We find that the experimentally measured values of $x$ and $y$ from semileptonic decays of $D_s^+$ favor solutions which have significant nonfactorized contribution, and, in particular, $R_{sl}$ favors solutions in scenarios where $A_1(q^2)$ is either flat or decreasing with $q^2$.

hep-ph↗
arXiv1995

Nonfactorization and Color-Suppressed $B \to ψ(ψ(2S))+K(K^*)$ Decays

Using $N_c=3$ value of the parameter $a_2=0.09$ but including a modest nonfactorized amplitude, we show that it is possible to understand all data, including polarization, for color-suppressed $B\toψ(ψ(2S))+K(K^*) $ decays in all commonly used models of form factors. We show that for $B\toψ+K$ decay one can define an effective $ a_2$, which is process-dependent and, in general, complex; but it is not possible to define an effective $a_2$ for $B\toψ+K^* $ decay. We also explain why nonfactorized amplitudes do not play a significant role in color-favored B decays.

hep-ph↗
arXiv1994

Probing Factorization in Color-Suppressed $B \rightarrow ψ(2S) + K(K^*)$ Decay

In order to probe the factorization hypothesis in color-suppressed $B \rightarrow ψ(2S) + K (K^*)$ decays we have studied three ratios: $ R \equiv B (B \rightarrow ψK) / B (B \rightarrow ψ(2S) K)$, $ R' \equiv B (B \rightarrow ψK^*) / B (B \rightarrow ψ(2S) K^*)$ and $ P_L^\prime \equiv Γ_L (B \rightarrow ψ(2S) K^*)/Γ(B \rightarrow ψ(2S) K^*)$ in several scenarios for the $ q^2$-dependence of the form factors involved. We find that measurements of R and $R' $, which exist, do not yield scenario-independent tests of factorization. However, the predicted range of $ P_L^\prime$ in all scenarios lies in a narrow range, $ 0.50 {\ \lower-1.2pt\vbox{\hbox{\rlap{$<$}\lower5pt\vbox{\hbox{$\sim$}}}}\ } P_L^\prime \leq 0.67$, and could test factorization.

hep-ph↗