58 research outputs found
Flavour-Conserving CP Phases in Supersymmetry and Implications for Exclusive B Decays
We study rare exclusive B decays based on the quark-level transition
b->s(d)l^+l^-, where l=e or mu, in the context of supersymmetric theories with
minimal flavour violation. We present analytic expressions for various mixing
matrices in the presence of new CP-violating phases, and examine their impact
on observables involving B and \bar{B} decays. An estimate is obtained for
CP-violating asymmetries in B->K^(*)l^+l^- and B->rho(pi)l^+l^- decays for the
dilepton invariant mass region 1.2 GeV < M_{l^+l^-}< M_{J/psi}. As a typical
result, we find a CP-violating partial width asymmetry of about -6% (-5%) in
the case of B->pi (B->rho) in effective supersymmetry with phases of O(1),
taking into account the measurement of the inclusive b->s gamma branching
fraction. On the other hand, CP asymmetries of less than 1% are predicted in
the case of B->K^(*). We argue that it is not sufficient to have additional CP
phases of O(1) to observe large CP-violating effects in exclusive b->s(d)l^+l^-
decays.Comment: 34 pages, REVTeX, 6 figures, final version to appear in Phys. Rev. D,
with some minor addition
Form Factors
The bounds on the form factors for decay are
studied. Constrained by lattice data and a constrained conformal mapping, the
more informations can be obtained for form-factor which dominates
the decay rate at large . Specifically, we confirm a moderately increasing
behavior of this form factor.Comment: 15 pages, Latex, 4 figure
Evidence for Factorization in Three-body B --> D(*) K- K0 Decays
Motivated by recent experimental results, we use a factorization approach to
study the three-body B --> D(*) K- K0 decay modes. Two mechanisms are proposed
for kaon pair production: current-produced (from vacuum) and transition (from B
meson). The Bbar0 --> D(*)+ K- K0 decay is governed solely by the
current-produced mechanism. As the kaon pair can be produced only by the vector
current, the matrix element can be extracted from e+ e- --> K Kbar processes
via isospin relations. The decay rates obtained this way are in good agreement
with experiment. Both current-produced and transition processes contribute to
B- --> D(*)0 K- K0 decays. By using QCD counting rules and the measured B- -->
D(*)0 K- K0 decay rates, the measured decay spectra can be understood.Comment: 17 pages, 6 figure
New Physics in b -> s mu+ mu-: CP-Conserving Observables
We perform a comprehensive study of the impact of new-physics operators with
different Lorentz structures on decays involving the b -> s mu+ mu- transition.
We examine the effects of new vector-axial vector (VA), scalar-pseudoscalar
(SP) and tensor (T) interactions on the differential branching ratios and
forward-backward asymmetries (A_{FB}'s) of Bsbar -> mu+ mu-, Bdbar -> Xs mu+
mu-, Bsbar -> mu+ mu- gamma, Bdbar -> Kbar mu+ mu-, and Bdbar -> K* mu+ mu-,
taking the new-physics couplings to be real. In Bdbar -> K* mu+ mu-, we further
explore the polarization fraction f_L, the angular asymmetry A_T^{(2)}, and the
longitudinal-transverse asymmetry A_{LT}. We identify the Lorentz structures
that would significantly impact these observables, providing analytical
arguments in terms of the contributions from the individual operators and their
interference terms. In particular, we show that while the new VA operators can
significantly enhance most of the asymmetries beyond the Standard Model
predictions, the SP and T operators can do this only for A_{FB} in Bdbar ->
Kbar mu+ mu-.Comment: 54 pages, JHEP format, 45 figures (included). 5/6/2013: typos in K*
mu mu angular coefficients corrected, typos in Eq. (D.12) corrected, added a
missing term in I3LT in Eq. (D.16). Numerical analysis unchange
Phenomenology of non-standard Z couplings in exclusive semileptonic b -> s transitions
The rare decays , and
are analyzed in a generic scenario where New Physics effects
enter predominantly via penguin contributions. We show that this
possibility is well motivated on theoretical grounds, as the vertex
is particularly susceptible to non-standard dynamics. In addition, such a
framework is also interesting phenomenologically since the coupling
is rather poorly constrained by present data. The characteristic features of
this scenario for the relevant decay rates and distributions are investigated.
We emphasize that both sign and magnitude of the forward-backward asymmetry of
the decay leptons in , , carry sensitive information on New Physics. The observable is proposed as a useful probe of
non-standard CP violation in couplings.Comment: Minor modifications; version to appear in Phys. Rev.
Analysis of Neutral Higgs-Boson Contributions to the Decays B_s -> l^+l^- and B -> K l^+l^-
We report on a calculation of Higgs-boson contributions to the decays B_s ->
l^+l^- and B -> K l^+l^- (l=e, mu) which are governed by the effective
Hamiltonian describing b -> s l^+ l^-. Compact formulae for the Wilson
coefficients are provided in the context of the type-II two-Higgs-doublet model
(2HDM) and supersymmetry (SUSY) with minimal flavour violation, focusing on the
case of large tan(beta). We derive, in a model-independent way, constraints on
Higgs-boson-mediated interactions, using present experimental results on rare B
decays including b -> s gamma, B_s -> mu^+ mu^-, and B -> K^(*) mu^+ mu^-. In
particular, we assess the impact of possible scalar and pseudoscalar
interactions transcending the standard model (SM) on the branching ratio of B_s
-> mu^+ mu^- and the forward-backward (FB) asymmetry of mu^- in B -> K mu^+
mu^- decay. We find that the average FB asymmetry, which is unobservably small
within the SM, and therefore a potentially valuable tool to search for new
physics, is predicted to be no greater than 4% for a nominal branching ratio of
about 6x10^{-7}. Moreover, striking effects on the decay spectrum of B -> K
mu^+ mu^- are already ruled out by experimental data on the B_s -> mu^+ mu^-
branching fraction. In addition, we study the constraints on the parameter
space of the 2HDM and SUSY with minimal flavour violation. While the type-II
2HDM does not give any sizable contributions to the above decay modes, we find
that SUSY contributions obeying the constraint on b -> s gamma can affect
significantly the branching ratio of B_s -> mu^+ mu^-. We also comment on
previous calculations contained in the literature.Comment: 29 pages, REVTeX, 8 figures. Minor corrections in Eqs. (5.4), (5.11)
and (6.3) of the published versio
Ward Identities, B-> \rho Form Factors and |V_ub|
The exclusive FCNC beauty semileptonic decay B-> \rho is studied using Ward
identities in a general vector meson dominance framework, predicting vector
meson couplings involved. The long distance contributions are discussed which
results to obtain form factors and |V_ub|. A detailed comparison is given with
other approaches.Comment: 30 pages+four postscript figures, an Appendix adde
Model-independent constraints on new physics in b --> s transitions
We provide a comprehensive model-independent analysis of rare decays
involving the b --> s transition to put constraints on dimension-six Delta(F)=1
effective operators. The constraints are derived from all the available
up-to-date experimental data from the B-factories, CDF and LHCb. The
implications and future prospects for observables in b --> s l+l- and b --> s
nu nu transitions in view of improved measurements are also investigated. The
present work updates and generalises previous studies providing, at the same
time, a useful tool to test the flavour structure of any theory beyond the SM.Comment: 1+39 pages, 12 figures, 3 tables. v2: minor modifications, typos
corrected, references added, version to be published in JHE
Heavy to Light Meson Exclusive Semileptonic Decays in Effective Field Theory of Heavy Quark
We present a general study on exclusive semileptonic decays of heavy (B, D,
B_s) to light (pi, rho, K, K^*) mesons in the framework of effective field
theory of heavy quark. Transition matrix elements of these decays can be
systematically characterized by a set of wave functions which are independent
of the heavy quark mass except for the implicit scale dependence. Form factors
for all these decays are calculated consistently within the effective theory
framework using the light cone sum rule method at the leading order of 1/m_Q
expansion. The branching ratios of these decays are evaluated, and the heavy
and light flavor symmetry breaking effects are investigated. We also give
comparison of our results and the predictions from other approaches, among
which are the relations proposed recently in the framework of large energy
effective theory.Comment: 18 pages, ReVtex, 5 figures, added references and comparison of
results, and corrected signs in some formula
Phenomenological Profiles of the Inclusive Hadron Spectra in the Decay
Hadron spectra and hadronic moments in the decay
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 -meson wave-function effects. The measured branching ratios
for the inclusive decays are used to fix the normalization of the long-distance contribution.
The momentum distribution of the 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 -resonance. We also
study the effect of various descriptions of the resonant and non-resonant
contributions in 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 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 . We show that data from the forthcoming B facilities
could be used effectively to measure the short-distance contribution in , enabling precise determination of the FM model and heavy
quark effective theory parameters and .Comment: 24 pages, 21 figures (require epsf.sty
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