3,749 research outputs found
Top mass dependent alpha_s^3 corrections to B-meson mixing in the MSSM
We compute the top mass dependent NLO strong interaction matching conditions
to the Delta F=2 effective Hamiltonian in the general MSSM. We study the
relevance of such corrections, comparing its size with that of previously known
NLO corrections in the limit mt->0, in scenarios with degeneracy, alignment,
and hierarchical squarks. We find that, while these corrections are generally
small, there are regions in the parameter space where the contributions to the
Wilson coefficients C1 and C4 could partially overcome the expected suppression
m_t/M_SUSY.Comment: 15 pages, 6 figure
B -> K* mu+ mu- optimised observables in the MSSM
We provide a detailed analysis of the impact of the newly measured optimised
observables in the B -> K* mu+ mu- decay by the LHCb experiment. The analysis
is performed in the MSSM, both in the context of the usual constrained
scenarios, and in the context of a more general set-up where the SUSY partner
masses are independent. We show that the global agreement of the MSSM solutions
with the data is still very good. Nevertheless, especially in the constrained
scenarios, the limits from B -> K* mu+ mu- are now very strong, and are at the
same level as the well-known b -> s gamma constraints. We describe the
implications of the B -> K* mu+ mu- measurements both on the Wilson
coefficients and on the SUSY parameters.Comment: 20 pages, 6 figure
Natural SUSY and Kaon Mixing in view of recent results from Lattice QCD
Lattice results are available for Delta S=2 matrix elements for the first
time in full QCD, which improve considerably the status of hadronic
uncertainties in K-Kbar mixing with respect to earlier phenomenological
studies. Using an average of the ETMC and RBC results, we analyze epsilonK in
Natural SUSY. This scenario arises as a consistent BSM framework after the
latest results from the LHC. The analysis is improved with respect to previous
studies including next-to-leading order matching conditions of order
(alpha_s)^3. We derive new bounds for SUSY mass insertions in the scenario with
a light third generation and study the implications for squark and gluino
masses, compared with direct searches at the LHC. Assuming natural values for
the flavor violating SUSY couplings of both chiralities, we find that the
sbottom must be heavier than 3 TeV for a gluino mass up to 10 TeV. In this
scenario no natural values for squark and gluino masses can satisfy the flavor
bounds.Comment: v3: Results updated with the latest (September 2012) lattice QCD
results. Version published in Physical Review
Updated NNLO QCD predictions for the weak radiative B-meson decays
Weak radiative decays of the B mesons belong to the most important flavor
changing processes that provide constraints on physics at the TeV scale. In the
derivation of such constraints, accurate standard model predictions for the
inclusive branching ratios play a crucial role. In the current Letter we
present an update of these predictions, incorporating all our results for the
O(alpha_s^2) and lower-order perturbative corrections that have been calculated
after 2006. New estimates of nonperturbative effects are taken into account,
too. For the CP- and isospin-averaged branching ratios, we find B_{s gamma} =
(3.36 +_ 0.23) * 10^-4 and B_{d gamma} = 1.73^{+0.12}_{-0.22} * 10^-5, for
E_gamma > 1.6GeV. Both results remain in agreement with the current
experimental averages. Normalizing their sum to the inclusive semileptonic
branching ratio, we obtain R_gamma = ( B_{s gamma} + B_{d gamma})/B_{c l nu} =
(3.31 +_ 0.22) * 10^-3. A new bound from B_{s gamma} on the charged Higgs boson
mass in the two-Higgs-doublet-model II reads M_{H^+} > 480 GeV at 95%C.L.Comment: journal version, 5 pages, no figure
Some Remarks on the Pade Unitarization of Low-Energy Amplitudes
We present a critical analysis of Pade-based methods for the unitarization of
low energy amplitudes. We show that the use of certain Pade Approximants to
describe the resonance region may lead to inaccurate determinations. In
particular, we find that in the Linear Sigma Model the unitarization of the low
energy amplitude through the inverse amplitude method produces essentially
incorrect results for the mass and width of the sigma. Alternative sequences of
Pades are studied and we find that the diagonal sequences (i.e., [N/N]) have
much better convergence properties.Comment: 12 pages, 4 fig
Flavour constraints on scenarios with two or three heavy squark generations
We re-assess constraints from flavour-changing neutral currents in the kaon
system on supersymmetric scenarios with a light gluino, two heavy generations
of squarks and a lighter third generation. We compute for the first time limits
in scenarios with three heavy squark families, taking into account QCD
corrections at the next-to-leading order. We compare our limits with those in
the case of two heavy families. We use the mass insertion approximation and
consider contributions from gluino exchange to constrain the mixing between the
first and second squark generation. While it is not possible to perform a
general analysis, we assess the relevance of each kind of flavour- and
CP-violating parameters. We also provide ready to use magic numbers for the
computation of the Wilson coefficients at 2 GeV for these scenarios.Comment: 23 pages, 14 figures; v3: matches published version (contains
improvements in the presentation and clarifications
Bd^0(t)->pi^+pi^- and Bs^0(t)-> K^+ K^- Decays: A Tool to Measure New-Physics Parameters
If physics beyond the standard model is present in B decays, experimental
measurements seem to suggest that it principally affects those processes with
significant b->s penguin amplitudes. It was recently argued that, in general,
such new-physics (NP) effects can be parametrized in terms of a single NP
amplitude A^q and phase \Phi_q, for q=u,d,s,c. In this paper, we show that the
study of the decays Bs(t) -> K^+ K^- and Bd(t) -> \pi^+\pi^- allows one to
measure the NP parameters A^u and \Phi_u. We examine the implications for this
method of the latest experimental results on these decays. If NP is found in
Bs(t) -> K^+ K^-, it can be partially identified through measurements of
Bs(t)-> K^0 \bar K^0.Comment: 12 pages, 2 figures, LaTeX. Changed reference
Complete Anatomy of B -> K*ll and its angular distribution
We present a complete and optimal set of observables for the exclusive 4-body
B meson decay B -> K*(->K pi) l+l- in the low dilepton mass region, that
contains a maximal number of clean observables. This basis of observables is
built in a systematic way. We show that all the previously defined observables
and any observable that one can construct, can be expressed as a function of
this basis. This set of observables contains all the information that can be
extracted from the angular distribution in the cleanest possible way. We
provide explicit expressions for the full and the uniangular distributions in
terms of this basis. The conclusions presented here can be easily extended to
the large-q^2 region. We study the sensitivity of the observables to
right-handed currents and scalars. Finally, we present for the first time all
the symmetries of the full distribution including massive terms and scalar
contributions.Comment: 37 pages, 12 Figures. Corrected typo in Eqs. (29) and (44). Results
and conclusions unchange
Factores de riesgo y supervivencia libre de tumor en pacientes con trasplante renal de cadáver
[Background] There is an agreement in the fact that cancer incidence in transplant recipients increases at a rate disproportionately greater than in the general population. Several clinical studies have identified cancer risk factors, such as age, male gender, tobacco, UV radiation, viral infections, previous malignancies, intensity and duration of immunosuppressive therapies, HLA matches and time in waiting list.
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