2,196 research outputs found
B_s to K^(*)0 \bar K^(*)0 decays: the golden channels for new physics searches
We point out that time-dependent CP asymmetries in B_s to K^{*0} \bar K^{*0}
decays probe the presence of new physics in b to s transitions with an
unprecedented theoretical accuracy. We show that, contrary to the case of B_d
to phi K_S, it is possible to obtain a model-independent prediction for the
coefficient S(B_s to K^{*0} \bar K^{*0}) in the Standard Model. We give an
estimate of the experimental precision achievable with the next generation of B
physics experiments. We also discuss how this approach can be extended to the
case of B_s to \bar K^{*0} K^0, B_s to K^{*0} \bar K^0 and B_s to K^0 \bar K^0
decays and the different experimental challenges for these channels.Comment: 4 pages, 1 figure. v2: Corrected dependence on CKM angles, expanded
discussion of multiple polarizations, conclusions strengthened. Final version
to appear in PR
Charming Penguins in B decays
Full expressions of the and
amplitudes, given in terms of matrix elements of operators of the effective
weak Hamiltonian, are used to study the dependence of the relevant branching
ratios on the different contributions. The uncertainty in the extraction of the
weak phase from the measurement of the time-dependent asymmetry in
decays is also analyzed. We find that, among several
effects which may enhance the branching ratio, the most
important is due to ``charming penguin" diagrams that have never been studied
before. These diagrams easily increase up to a
value of . The same effect produces, however, a large error
in the extraction of from the measurement of the time-dependent asymmetry. We show that it is possible to determine
charming-penguin amplitudes from the experimental measurement of many decay
rates. Their effect is impressive in and decays, where charming-penguin contributions easily give values of
and of about . Among other possibilities, we also suggest to use , the BR of which can be as large as , to determine the
size of charming-penguin amplitudes.Comment: LaTeX, 28 pages, 8 figure
b -> s Transitions: A New Frontier for Indirect SUSY Searches
The present unitarity triangle fit, whose essential input is represented by
the s to d and b to d transition processes, fully agrees with the SM. However,
most of the phenomena involving b to s transitions are still largely unexplored
and hence b to s phenomenology still constitutes a place for new physics
manifestations, in spite of the tremendous experimental and theoretical
progress on B to X_s gamma. We perform a systematic study of the CP conserving
and violating SUSY contributions to b to s processes in a generic MSSM. We
consider gluino exchange contributions including NLO QCD corrections and
lattice hadronic matrix elements for Delta B = 2 and Delta B = 1 processes. We
take into account all available experimental information on processes involving
b to s transitions (B to X_s gamma, B to X_s l^+ l^- and the lower bound on the
B_s - bar B_s mass difference Delta M_s). We study the correlations among the
relevant observables under scrutiny at present or in a not too far future:
Delta M_s and the amount of CP violation in B to phi K_s, B_s to J/psi phi, B
to X_s gamma. In particular we discuss the recent data by BaBar and BELLE on
the time-dependent CP asymmetry in the decay B to phi K_s which suggest a
deviation from the SM expectation. Our results show that the processes
involving b to s transitions represent a splendid opportunity to constrain
different MSSM realizations, and, even more important, that they offer concrete
prospects to exhibit SUSY signals at B factories and hadron colliders in spite
of all the past frustration in FCNC searches of new physics hints.Comment: 20 pages, 8 figures. Bug in the code corrected, figures for RL and
RL=RR cases and some conclusions change
Penguin Contractions and Factorization in B -> K pi Decays
We study Lambda_{QCD}/m_B corrections to factorization in B -> K pi decays.
First, we analyze these decay channels within factorization, showing that,
irrespectively of the value of gamma, it is not possible to reproduce the
experimental data. Then, we discuss Lambda_{QCD}/m_B corrections to these
processes, and argue that there is a class of doubly Cabibbo enhanced
non-factorizable contributions, usually called charming penguins, that cannot
be neglected. Including these corrections, we obtain an excellent agreement
with experimental data. Furthermore, contrary to what is obtained with
factorization, we predict sizable rate asymmetries in B^\pm -> K^\pm \pi^0 and
B -> K^\pm pi^\mp.Comment: 4 pages, 3 figures. Talk given by L. Silvestrini at BCP4, Ise-Shima,
Japan, 18-23 Feb 200
Charming Penguins Saga
We briefly recall the main formulae for computing the B -> K pi branching
ratios within the "charming penguin" approach, present an updated fit to the
data, and explain why we believe that, in general, these fits can hardly be
used to extract gamma.Comment: Invited talk at FPCP '02 given by M. Ciuchini, uses econfmacros.tex.
Final version with minor changes to appear in the proceeding
Two Body B Decays, Factorization and LambdaQCD/mb Corrections
By using the recent experimental measurements of B -> pi pi and B -> K pi
branching ratios, we find that the amplitudes computed at the leading order of
the LambdaQCD/mb expansion disagree with the observed BRs, even taking into
account the uncertainties of the input parameters. Beyond the leading order,
Charming and GIM penguins allow to reconcile the theoretical predictions with
the data. Because of these large effects, we conclude, however, that it is not
possible, with the present theoretical and experimental accuracy, to determine
the CP violation angle gamma from these decays. We compare our results with
those obtained with the parametrization of the chirally enhanced
non-perturbative contributions by BBNS. We also predict large asymmetries for
several of the particle--antiparticle BRs, in particular BR(B+ -> K+ pi0),
BR(Bd -> K+ pi-) and BR(Bd -> pi+ pi-).Comment: 14 pages 3 figures uses aippro
Worries and Hopes for SUSY in CKM Physics: The b to s Example
We discuss the twofold role of flavor and CP violation as a constraint in
model building and as a signal of SUSY. Considering as an example b to s
transitions, we analyze present bounds on SUSY parameters, discuss possible
deviations from SM predictions in Bd and Bs physics and present strategies to
reveal SUSY signals in present and future experiments in the CKM domain.Comment: Invited talks given by A. Masiero and L. Silvestrini at the Workshop
on the CKM Unitarity Triangle, IPPP Durham, April 2003 (eConf C0304052). 9
pages, 5 figure
Upper bounds on SUSY contributions to b to s transitions from B_s - B_sbar mixing
We study the constraints on supersymmetric contributions to b to s
transitions from the recent allowed range and measurement of Bs-Bsbar mixing
obtained by the D0 and CDF collaborations at the Tevatron. We compute the upper
bounds on the relevant off-diagonal squark mass terms and compare them with the
bounds coming from Delta F=1 decays. We find that the constraints on
chirality-flipping mass insertions are unaffected. Conversely, the measurement
of Bs-Bsbar mixing is effective in constraining chirality-conserving mass
insertions, and it has striking effects in the case in which left- and
right-handed insertions have similar size. Finally, we discuss the phase of the
Bs-Bsbar mixing amplitude in the presence of SUSY contributions.Comment: 4 pages, 4 figures; v2: CDF measurement include
- âŠ