Showing papers by "Ahmed Ali published in 1999"
TL;DR: In this paper, a comparative study of the profile of the CKM unitarity triangle, and the resulting CP asymmetries in B decays, in the standard model and in several variants of the minimal supersymmetric standard model (MSSM), characterized by a single phase in the quark flavour mixing matrix, is presented.
Abstract: We report on a comparative study of the profile of the CKM unitarity triangle, and the resulting CP asymmetries in B decays, in the standard model and in several variants of the minimal supersymmetric standard model (MSSM), characterized by a single phase in the quark flavour mixing matrix. The supersymmetric contributions to the mass differences \(\Delta M_d\), \(\Delta M_s\) and to the CP-violating quantity \(\vert\epsilon\vert\) are, to an excellent approximation, equal to each other in these theories, allowing for a particularly simple way of implementing the resulting constraints on the elements of \(V_{CKM}\) from the present knowledge of these quantities. Incorporating the next-to-leading-order corrections and applying the current direct and indirect constraints on the supersymmetric parameters, we find that the predicted ranges of \(\sin 2 \beta\) in the standard model and in MSSM models are very similar. However, precise measurements at B-factories and hadron machines may be able to distinguish these theories in terms of the other two CP-violating phases \(\alpha\) and \(\gamma\). This is illustrated for some representative values of the supersymmetric contributions in \(\Delta M_d\), \(\Delta M_s\) and \(\vert \epsilon\vert\).
106 citations
TL;DR: In this article, a theoretical reappraisal of the branching ratios and CP asymmetries for the decays is presented, taking into account current theoretical uncertainties in the description of the long-distance contributions, an improved treatment of the renormalization scale dependence, and other parametric dependencies.
Abstract: We present a theoretical reappraisal of the branching ratios and CP asymmetries for the decays \(B \to X_q \ell^+ \ell^-\), with \(q=d,s\), taking into account current theoretical uncertainties in the description of the inclusive decay amplitudes from the long-distance contributions, an improved treatment of the renormalization scale dependence, and other parametric dependencies. Concentrating on the partial branching ratios \(\Delta{\cal B}(B \to X_q \ell^+ \ell^-)\), integrated over the invariant dilepton mass region \(1 \mbox{GeV}^2 \leq s \leq 6 \mbox{GeV}^2\), we calculate theoretical precision on the charge-conjugate averaged partial branching ratios \(\langle \Delta{\cal B}_q \rangle= (\Delta{\cal B}(B \to X_q \ell^+ \ell^-) + \Delta{\cal B}(\bar{B} \to \bar{X}_q \ell^+ \ell^-))/2\), CP asymmetries in partial decay rates \((a_{CP})_q=(\Delta{\cal B}(B \to X_q \ell^+ \ell^-) - \Delta{\cal B}(\bar{B} \to \bar{X}_q \ell^+\ell^-))/(2 \langle \Delta{\calB}_q \rangle)\), and the ratio of the branching ratios \(\Delta{\cal R} = \langle \Delta{\cal B}_d \rangle/\langle \Delta{\cal B}_s \rangle\). For the central values of the CKM parameters, we find \(\langle \Delta{\cal B}_s \rangle =(2.22^{+0.29}_{-0.30}) \times 10^{-6}\), \(\langle \Delta{\cal B}_d \rangle =(9.61^{+1.32}_{-1.47}) \times 10^{-8}\), \((a_{CP})_s =-(0.19^{+0.17}_{-0.19})\%\), \((a_{CP})_d =(4.40^{+3.87}_{-4.46})\%\), and \(\Delta{\cal R} =(4.32 \pm 0.03)\%\). The dependence of \(\langle \Delta{\cal B}_d \rangle\) and \(\Delta{\cal R}\) on the CKM parameters is worked out and the resulting constraints on the unitarity triangle from an eventual measurement of \(\Delta{\cal R}\) are illustrated.
37 citations
TL;DR: In this article, the authors calculated the hadron spectra and hadronic moments in the decay of the B-meson wave function using a Fermi motion model, taking into account both the short-distance and long-distance contributions of the decay amplitude.
Abstract: Hadron spectra and hadronic moments in the decay $B \to X_s \ell^+ \ell^-$ are calculated taking into account both the short-distance and long-distance contributions in the decay amplitude using a Fermi motion (FM) model to incorporate the $B$-meson wave-function effects. The measured branching ratios for the inclusive decays $B \to X_s+ (J/\psi,\psi^\prime,...)\to X_s \ell^+ \ell^-$ are used to fix the normalization of the long-distance contribution. The momentum distribution of the $J/\psi$ measured by the CLEO collaboration is fitted in the FM model which is then used to calculate the hadronic spectra from the resonant contribution also away from the $J/\psi$-resonance. We also study the effect of various descriptions of the resonant and non-resonant $c\bar{c}$ contributions in $B \to X_s \ell^+ \ell^-$ existing in the literature on the hadron energy and invariant mass spectra, and in the Forward-Backward asymmetry. Selective cuts on the hadron and dilepton invariant masses can be used to reduce the $B\bar{B}$ background and resonant contribution and, as an example, we work out the hadron spectra with the experimental cuts used by the CLEO collaboration in searching for the decay $B \to X_s \ell^+ \ell^-$. We show that data from the forthcoming B facilities could be used effectively to measure the short-distance contribution in $B \to X_s \ell^+ \ell^-$, enabling precise determination of the FM model and heavy quark effective theory parameters $\lambda_1$ and $\bar{\Lambda}$.
10 citations
TL;DR: In this paper, a new cardenolide(-)-14-methoxy-rcanoside (1) was isolated from the aqueous extract of the seeds of Securigera securidacea (L.) Deg. (Fabaceae) together with five new dihydrobenzofuran derivatives named securigran I-V (2-6).
Abstract: A new cardenolide(-)-14-methoxy-rcanoside (1) was isolated from the aqueous extract of the seeds of Securigera securidacea (L.) Deg. et Dörfl. (Fabaceae) together with five new dihydrobenzofuran derivatives named securigran I-V (2-6). Kaempferol and astragalin were also isolated from the aqueous extract of the flowers. (-)-14-Methoxyhyrcanoside and the total aqueous extract of the seeds showed marked chronotropic activity. The total aqueous extract also showed a marked diuretic and severe hypokalemic effects on the K(+)-level in serum. The hypoglycemic effect of the seeds was also confirmed.
9 citations
TL;DR: In this article, a comparative study of the profile of the CKM unitarity triangle, and the resulting CP asymmetries in B decays, in the standard model and in several variants of the minimal supersymmetric standard model (MSSM), characterized by a single phase in the quark flavour mixing matrix, is presented.
Abstract: We report on a comparative study of the profile of the CKM unitarity triangle, and the resulting CP asymmetries in B decays, in the standard model and in several variants of the minimal supersymmetric standard model (MSSM), characterized by a single phase in the quark flavour mixing matrix. The supersymmetric contributions to the mass differences \Delta M_d, \Delta M_s and to the CP-violating quantity |\epsilon| are, to an excellent approximation, equal to each other in these theories, allowing for a particularly simple way of implementing the resulting constraints on the elements of V_{CKM} from the present knowledge of these quantities. Incorporating the next-to-leading-order corrections and applying the current direct and indirect constraints on the supersymmetric parameters, we find that the predicted ranges of \sin 2 \beta in the standard model and in MSSM models are very similar. However, precise measurements at B-factories and hadron machines may be able to distinguish these theories in terms of the other two CP-violating phases \alpha and \gamma. This is illustrated for some representative values of the supersymmetric contributions in \Delta M_d, \Delta M_s and |\epsilon|.
8 citations