Analysis of B→a1(1260)(b1(1235))K∗B \to a_1(1260)(b_1(1235))K^* decays in the perturbative QCD approach

Within the framework of perturbative QCD approach, we study the charmless two-body decays $B\to a_1(1260)K^*, b_1(1235)K^*$. Using the decays constants and the light-cone distribution amplitudes for these mesons derived from the QCD sum rule method, we find the following results: (a) Our predictions for the branching ratios are consistent well with the QCDF results within errors, but much larger than the naive factorization approach calculation values. (b) We predict that the anomalous polarizations occurring in the decays $B\to \phi K^*, \rho K^*$ also happen in the decays $B\to a_1K^*$, while do not happen in the decays $B\to b_1K^*$. Here the contributions from the annihilation diagrams play an important role to explain the lager transverse polarizations in the decays $B\to a_1K^*$, while they are not sensitive to the polarizations in decays $B\to b_1K^*$. (c) Our predictions for the direct CP-asymmetries agree well with the QCDF results within errors. The decays $\bar B^0\to b^{+}_1K^{*-}, B^-\to b^{0}_1K^{*-}$ have larger direct CP-asymmetries, which could be measured by the present LHCb experiments.Comment: 12pages, 1figures. arXiv admin note: substantial text overlap with arXiv:1203.5913, arXiv:1203.591

Constraining the Unitarity Triangle with B -> V gamma

We discuss the exclusive radiative decays $B\to K^{*}\gamma$, $B \to\rho\gamma$, and $B\to\omega\gamma$ in QCD factorization within the Standard Model. The analysis is based on the heavy-quark limit of QCD. Our results for these decays are complete to next-to-leading order in QCD and to leading order in the heavy-quark limit. Special emphasis is placed on constraining the CKM-unitarity triangle from these observables. We propose a theoretically clean method to determine CKM parameters from the ratio of the $B\to\rho l\nu$ decay spectrum to the branching fraction of $B\to\rho\gamma$. The method is based on the cancellation of soft hadronic form factors in the large energy limit, which occurs in a suitable region of phase space. The ratio of the $B\to\rho\gamma$ and $B\to K^{*}\gamma$ branching fractions determines the side $R_{t}$ of the standard unitarity triangle with reduced hadronic uncertainties. The recent Babar bound on $B(B^0\to\rho^0\gamma)$ implies $R_t < 0.81 (\xi/1.3)$, with the limiting uncertainty coming only from the SU(3) breaking form factor ratio $\xi$. This constraint is already getting competitive with the constraint from $B_{s}$-$\bar B_{s}$ mixing. Phenomenological implications from isospin-breaking effects are briefly discussed.Comment: 23 pages, 8 figure

R-Parity Violation and Non-Abelian Discrete Family Symmetry

We investigate the implications of R-parity violating operators in a model with family symmetry. The family symmetry can determine the form of R-parity violating operators as well as the Yukawa matrices responsible for fermion masses and mixings. In this paper we consider a concrete model with non-abelian discrete symmetry Q_6 which contains only three R-parity violating operators. We find that ratios of decay rates of the lepton flavor violating processes are fixed thanks to the family symmetry, predicting BR(tau to 3e)/BR(tau to 3mu) ~ 4 m_{mu}^2/m_{tau}^2.Comment: 20 pages, 3 figure

The B-->pi K Puzzle and Supersymmetry

At present, there are discrepancies between the measurements of several observables in B-->pi K decays and the predictions of the standard model (the ``B-->pi K puzzle''). Although the effect is not yet statistically significant -- it is at the level of \gsim 3\sigma -- it does hint at the presence of new physics. In this paper, we explore whether supersymmetry (SUSY) can explain the B-->pi K puzzle. In particular, we consider the SUSY model of Grossman, Neubert and Kagan (GNK). We find that it is extremely unlikely that GNK explains the B-->pi K data. We also find a similar conclusion in many other models of SUSY. And there are serious criticisms of the two SUSY models that do reproduce the B-->pi K data. If the B-->pi K puzzle remains, it could pose a problem for SUSY models.Comment: 14 pages, 2 figures; added reference

Supersymmetric Contributions to Bs->K+K-

Inspired by the existing calculation of B->piK decays in supersymmetry (SUSY), we evaluate the dominant SUSY contributions to Bs->K+K-. We show that the observables of this process can be significantly modified in the presence of SUSY. In particular, the branching ratio can be increased considerably compared to the prediction of the standard model (SM). The effect is even more dramatic for the CP-violating asymmetries A_dir and A_mix. These asymmetries, expected to be small in the SM (A_dir is predicted to take only positive values), change drastically with SUSY contributions. The measurement of these observables can therefore be used to detect the presence of physics beyond the SM, and put constraints on its parameters.Comment: 17 pages, 2 figures. This new version contains one added reference and some minor style change

Can there be any new physics in b -> d penguins

We analyze the possibility of observing new physics effects in the $b \to d$ penguin amplitudes. For this purpose, we consider the decay mode $B \to K^0 \bar K^0$, which has only $b \to d$ penguin contributions. Using the QCD factorization approach, we find very tiny CP violating effects in the standard model for this process. Furthermore, we show that the minimal supersymmetric standard model with $LR$ mass insertion and R-parity violating supersymmetric model can provide substantial CP violation effects. Observation of sizable CP violation in this mode would be a clear signal of new physics.Comment: Published versio

Non-factorizable Contributions to B→ππB \to \pi\pi Decays

We investigate to what extent the experimental information on $B \to \pi\pi$ branching fractions and CP asymmetries can be used to better understand the QCD dynamics in these decays. For this purpose we decompose the independent isospin amplitudes into factorizable and non-factorizable contributions. The former can be estimated within the framework of QCD factorization for exclusive $B$ decays. The latter vanish in the heavy-quark limit, $m_b \to \infty$, and are treated as unknown hadronic parameters. We discuss at some length in which way the non-factorizable contributions are treated in different theoretical and phenomenological frameworks. We point out the potential differences between the phenomenological treatment of power-corrections in the ``BBNS approach'', and the appearance of power -suppressed operators in soft-collinear effective theory (SCET). On that basis we define a handful of different (but generic) scenarios where the non-factorizable part of isospin amplitudes is parametrized in terms of three or four unknowns, which can be constrained by data. We also give some short discussion on the implications of our analysis for $B \to \pi K$ decays. In particular, since non-factorizable QCD effects in $B \to \pi \pi$ may be large, we cannot exclude sizeable non-factorizable effects, which violate $SU(3)_F$ flavour symmetry, or even isospin symmetry (via long-distance QED effects). This may help to explain certain puzzles in connection with isospin-violating observables in $B \to \pi K$ decays.Comment: published version, minor correction

Exploring the Unitarity Triangle through CP violation observables in Bs→K+K−B_s \to K^+ K^-

We discuss the determination of the CKM parameters from the forthcoming $CP$ violation observables in $B_s \to K^+ K^-$ decays. Combining the information on mixing induced CP violation in $B_s \to K^+ K^-$, with the $B_d \to J/\psi K_s$ precision observable $\sin 2\beta$ and the $B^0_s$--$\bar{B^0_s}$ mixing phase $\phi_s$, we propose a determination of the unitarity triangle $(\bar\rho, \bar\eta)$. Computing the penguin parameters $(r, \theta)$ within QCD factorization yield precise determination of $(\bar\rho, \bar\eta)$, reflected by a weak dependence on the $\theta$ which is shown as a second order effect. The impact of the direct CP violation observable $C_{KK}$ on the penguin parameters are investigated and a lower bound on $C_{KK}$ is extracted. We also discuss the effect of the $B^0_s$--$\bar{B^0_s}$ new physics mixing phase on the penguin parameters $(r, \theta)$ and $S_{KK}$. Using the SU(3)-flavour symmetry argument and the current $B$-factories data provided by the $B_d \to \pi^+ \pi^-$ modes, we complement the $B_s \to K^+ K^-$ CP-violating observables in a variety of ways, in particular we find that $S_{KK}>0$. Finally we analyze systematically the SU(3)-symmetry breaking factor within QCD factorization.Comment: 22 pages, 6 figures, typos corrected, reference and some remarks adde

The 2004 UTfit Collaboration Report on the Status of the Unitarity Triangle in the Standard Model

Using the latest determinations of several theoretical and experimental parameters, we update the Unitarity Triangle analysis in the Standard Model. The basic experimental constraints come from the measurements of |V_ub/V_cb|, Delta M_d, the lower limit on Delta M_s, epsilon_k, and the measurement of the phase of the B_d - anti B_d mixing amplitude through the time-dependent CP asymmetry in B^0 to J/psi K^0 decays. In addition, we consider the direct determination of alpha, gamma, 2 beta + gamma and cos(2 beta) from the measurements of new CP-violating quantities, recently performed at the B factories. We also discuss the opportunities offered by improving the precision of the various physical quantities entering in the determination of the Unitarity Triangle parameters. The results and the plots presented in this paper can also be found at http://www.utfit.org, where they are continuously updated with the newest experimental and theoretical results.Comment: 32 pages, 17 figures. High resolution figures and updates can be found at http://www.utfit.org v2: misprints correcte

Direct CP Violation, Branching Ratios and Form Factors B→πB \to \pi, B→KB \to K in BB Decays

The $B \to \pi$ and $B \to K$ transitions involved in hadronic B decays are investigated in a phenomenological way through the framework of QCD factorization. By comparing our results with experimental branching ratios from the BELLE, BABAR and CLEO Collaborations for all the B decays including either a pion or a kaon, we propose boundaries for the transition form factors $B \to \pi$ and $B \to K$ depending on the CKM matrix element parameters $\rho$ and $\eta$. From this analysis, the form factors required to reproduce the experimental data for branching ratios are $F^{B \to \pi}= 0.31 \pm 0.12$ and $F^{B \to K}= 0.37\pm 0.13$. We calculate the direct CP violating asymmetry parameter, $a_{CP}$, for $B \to \pi^{+} \pi^{-} \pi$ and $B \to \pi^{+} \pi^{-} K$ decays, in the case where $\rho-\omega$ mixing effects are taken into account. Based on these results, we find that the direct CP asymmetry for $B^{-} \to \pi^{+} \pi^{-} \pi^{-}$, $\bar{B}^{0} \to \pi^{+} \pi^{-} \pi^{0}$, $B^{-} \to \pi^{+} \pi^{-} K^{-}$, and $\bar{B}^{0} \to \pi^{+} \pi^{-} \bar{K}^{0}$, reaches its maximum when the invariant mass $\pi^{+} \pi^{-}$ is in the vicinity of the $\omega$ meson mass. The inclusion of $\rho-\omega$ mixing provides an opportunity to erase, without ambiguity, the phase uncertainty mod$(\pi)$ in the determination of the CKM angles $\alpha$ in case of $b\to u$ and $\gamma$ in case of $b \to s$.Comment: 74 pages, 15 figures, 8 tables. A few misprints corrected, two references adde