814 research outputs found
Hunting the CKM weak phase with time-integrated Dalitz analyses of Bs -> K pi pi decays
We present a new technique to extract information on the Unitarity Triangle
from the study of Bs -> K pi pi Dalitz plot. Using isospin symmetry and the
possibility to access the decay amplitudes from Dalitz analyses, we propose a
new strategy to extract the weak phase gamma from Bs to K pi pi.Comment: 2 pages. v2: Discussion of interference on Dalitz plot clarified. Bs
-> K K pi channels removed. v3: Improved discussion of experimental aspects.
Final version to appear in Phys. Lett.
CP violation in supersymmetric theories
We review the present status of CP violating problem in supersymmetric
extensions of the standard model. We analyze the constraints imposed by the
experimental limits of the electron, neutron, and mercury electric dipole
moments on the supersymmetric CP phases and show that only the scenarios with
flavour-off- diagonal CP violation remain attractive. These scenarios require
hermitian Yukawa matrices which naturally arise in models with left-right
symmetry or a SU(3) flavour symmetry. In this case, epsilon_K and
epsilon'/epsilon can be saturated by a small non-universality of the soft
scalar masses through the gluino and chargino contributions respectively. The
model also predicts a strong correlation between A_{CP}(b-> s gamma) and the
neutron electric dipole moment. In this framework, the standard model gives a
the leading contribution to the CP asymmetry in B ->psi K_S decay, while the
dominant chargino contribution to this asymmetry is < 0.2. Thus, no constraint
is set on the non-universality of this model by the recent BaBar and Belle
measureets.Comment: 34 pages, 10 figures. Invited review article for International
Journal of Modern Physics
The Chromomagnetic Dipole Operator and the B Semileptonic Branching Ratio
We consider the possibility of having a large branching ratio for the decay
coming from an enhanced Wilson coefficient of the chromomagnetic
dipole operator. We show that values of up to or
more are compatible with the constraints coming from the CLEO experimental
results on and . Such large values can
reconcile the predictions of both the semileptonic branching ratio and the
charm counting with the present experimental results. We also discuss a
supersymmetric model with gluino-mediated flavour violations, which can account
for such large values of .Comment: 19 pages, 3 eps figures included, replacement with minor change
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
The UTfit Collaboration Report on the Status of the Unitarity Triangle beyond the Standard Model I. Model-independent Analysis and Minimal Flavour Violation
Starting from a (new physics independent) tree level determination of rhobar
and etabar, we perform the Unitarity Triangle analysis in general extensions of
the Standard Model with arbitrary new physics contributions to loop-mediated
processes. Using a simple parameterization, we determine the allowed ranges of
non-standard contributions to |Delta F|=2 processes. Remarkably, the recent
measurements from B factories allow us to determine with good precision the
shape of the Unitarity Triangle even in the presence of new physics, and to
derive stringent constraints on non-standard contributions to |Delta F|=2
processes. Since the present experimental constraints favour models with
Minimal Flavour Violation, we present the determination of the Universal
Unitarity Triangle that can be defined in this class of extensions of the
Standard Model. Finally, we perform a combined fit of the Unitarity Triangle
and of new physics contributions in Minimal Flavour Violation, reaching a
sensitivity to a new physics scale of about 5 TeV. We also extrapolate all
these analyses into a "year 2010" scenario for experimental and theoretical
inputs in the flavour sector. All the results presented in this paper are also
available at the URL http://www.utfit.org, where they are continuously updated.Comment: 29 pages, 56 figure
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