1,586,957 research outputs found
B(s)-B(s)bar Mixing in Supersymmetric Grand Unified Models
We study B_s-\bar{B}_s mixing in grand unified SO(10), SU(5) models where the
mixings among the second and third generation squarks arise due to the
existence of flavor violating sources in the Dirac and Majorana couplings which
are responsible for neutrino mixings. We find that when the branching ratio of
tau->mu gamma decay is enhanced to be around the current experimental bound,
B_s-\bar{B}_s mixing may also contain large contribution from supersymmetry in
the SO(10) boundary condition. Consequently, the phase of B_s-\bar{B}_s mixing
is large (especially for small tan beta and large scalar mass m_0) and can be
tested by measuring CP asymmetries of B_s decay modes.Comment: 5 pages, 3 figures. Modifications in the text and the title,
references added, results unchanged, to appear in PR
Complete next-to-leading order gluino contributions to b--> s gamma and b--> s g
We present the first complete order alpha_s corrections to the Wilson
coefficients (at the high scale) of the various versions of magnetic and
chromomagnetic operators which are induced by a squark-gluino exchange. For
this matching calculation, we work out the on-shell amplitudes b--> s gamma and
b --> s g, both in the full and in the effective theory up to order alpha_s^2.
The most difficult part of the calculation is the evaluation of the two-loop
diagrams in the full theory; these can be split into two classes: a) diagrams
with one gluino and a virtual gluon; b) diagrams with two gluinos or with one
gluino and a four-squark vertex. Accordingly, the Wilson coefficients can be
split into a part a) and a part b). While part b) of the Wilson coefficients is
presented in this paper for the first time, part a) was given in (Bobeth et
al.). We checked their results for the coefficients of the magnetic operators
and found perfect agreement. Moreover, we work out the renormalization
procedure in great detail. Our results for the complete next-to-leading order
Wilson coefficients are fully analytic, but far too long to be printed. We
therefore publish them in the form of a C++ program. They constitute a crucial
building block for the phenomenological next-to-leading logarithmic analysis of
the branching ratio Bbar --> X_s gamma in a supersymmetric model beyond minimal
flavor violation.Comment: 38 pages, including c++ cod
The large CP phase in B(s)-anti-B(s) mixing from primary scalar unparticles
In this letter we consider the case of primary scalar unparticle
contributions to B(d,s) mixing. With particular emphasis on the impact of the
recent hint of new physics in the measurement of the B(s) mixing phase, phi(s),
we determine the allowed parameter space and impose bounds on the unparticle
couplings.Comment: 8 pages, 8 jpeg figures, using pdflatex. Typo corrected, reference
adde
The b -> s gamma decay revisited
In this work we compute the leading logarithmic corrections to the b -> s
gamma decay in a dimensional scheme which does not require any definition of
the gamma5 matrix. The scheme does not exhibit unconsistencies and it is
therefore a viable alternative to the t'Hooft Veltman scheme, particularly in
view of the next-to-leading computation. We confirm the recent results of
Ciuchini et al.Comment: 11 pages RevTeX + 2 EPSF figures, report IFUP-TH 2/94, HUTP-93/A038.
PostScript file or hardcopy available from the authors upon reques
Natural Supersymmetry and b -> s gamma constraints
We investigate constraints from the observed branching ratio for b -> s gamma
and fine-tuning in the framework of natural supersymmetry. The natural
supersymmetry requires the large trilinear coupling of the stop sector, light
higgsinos (a small mu parameter) and light stops, in order to reduce the
fine-tuning in the Higgs sector while avoiding the LEP constraint. It is found
that in such a scenario 5% (10%) level of fine-tuning is inevitable due to the
b -> s gamma constraint even if the messenger scale is as low as 10^5 GeV (10^4
GeV), provided that the gaugino masses satisfy the GUT relation.Comment: 13 pages, 4 figures; version to be published in PL
Cornering New Physics in b --> s Transitions
We derive constraints on Wilson coefficients of dimension-six effective
operators probing the b --> s transition, using recent improved measurements of
the rare decays Bs --> mu+mu-, B --> K mu+mu- and B --> K* mu+mu- and including
all relevant observables in inclusive and exclusive decays. We consider
operators present in the SM as well as their chirality-flipped counterparts and
scalar operators. We find good agreement with the SM expectations. Compared to
the situation before winter 2012, we find significantly more stringent
constraints on the chirality-flipped coefficients due to complementary
constraints from B --> K mu+mu- and B --> K* mu+mu- and due to the LHCb
measurement of the angular observable S_3 in the latter decay. We also list the
full set of observables sensitive to new physics in the low recoil region of B
--> K* mu+mu-.Comment: 18 pages, 6 figures, 4 tables. v3: typos correcte
Transverse Momentum Distribution in b-> s Gamma
We present the complete calculation of the transverse momentum distribution
for the decay b->s Gamma. The contributions of the leading operator O_7 are
computed: infrared logarithms are resummed with next-to-leading accuracy,
according to usual techniques of resummation. Non logarithmic terms are
evaluated to O(alpha_S) by calculating one loop diagrams.Comment: Talk given 10th International QCD Conference (QCD 03), Montpellier,
France, 2-9 Jul 2003. 4 page
Measurements of the branching fractions of the decays B°s â Dâs K± and B°s â DÂŻsÏ+
The decay mode B°s â Dâs K± allows for one of the theoretically cleanest measurements of the CKM angle Îł through the study of time-dependent CP violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode B°s â DÂŻsÏ+ based on a data sample corresponding to 0.37 fbÂŻÂč of proton-proton collisions at âs = 7TeV collected in 2011 with the LHCb detector. In addition, the ratio of B meson production fractions fs/fd, determined from semileptonic decays, together with the known branching fraction of the control channel B°s â DÂŻsÏ+ is used to perform an absolute measurement of the branching fractions: B(B°s â DÂŻsÏ+) = (2.95 ± 0.05 ± 0.17 -0.22 +0.18) Ă 10ÂŻÂł ; B(B°s â Dâs K±) = (1.90 ± 0.12 ± 0.13 -0.14 +0.12) Ă 10ÂŻ4 ; where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to f s/f
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