337 research outputs found
Indirect search for supersymmetry in rare B decays
QCD corrections to the gluino induced contribution to b --> s gamma are shown
to be important in order to extract reliable bounds on the off-diagonal
elements of the squark mass matrices.Comment: 4 pages including 2 postscript figure
Towards the NNLL precision in
The present NLL prediction for the decay rate of the rare inclusive process
has a large uncertainty due to the charm mass
renormalization scheme ambiguity. We estimate that this uncertainty will be
reduced by a factor of 2 at the NNLL level. This is a strong motivation for the
on-going NNLL calculation, which will thus significantly increase the
sensitivity of the observable to possible new degrees
of freedom beyond the SM. We also give a brief status report of the NNLL
calculation.Comment: 5 pages, 2 figures, contribution to the proceedings of EPS-HEP 200
Smooth invariant densities for random switching on the torus
We consider a random dynamical system obtained by switching between the flows
generated by two smooth vector fields on the 2d-torus, with the random
switchings happening according to a Poisson process. Assuming that the driving
vector fields are transversal to each other at all points of the torus and that
each of them allows for a smooth invariant density and no periodic orbits, we
prove that the switched system also has a smooth invariant density, for every
switching rate. Our approach is based on an integration by parts formula
inspired by techniques from Malliavin calculus.Comment: 19 page
Reduction of Charm Quark Mass Scheme Dependence in at the NNLL Level
The uncertainty of the theoretical prediction of the
branching ratio at NLL level is dominated by the charm mass renormalization
scheme ambiguity. In this paper we calculate those NNLL terms which are related
to the renormalization of , in order to get an estimate of the
corresponding uncertainty at the NNLL level. We find that these terms
significantly reduce (by typically a factor of two) the error on induced by the definition of . Taking into account the
experimental accuracy of around 10% and the future prospects of the
factories, we conclude that a NNLL calculation would increase the sensitivity
of the observable to possible new degrees of freedom
beyond the SM significantly.Comment: 13 pages including 3 figure
in the Standard Model
We give a summary about the various contributions which have to be calculated
in order to obtain the next-to-leading logarithmic result for the branching
ratio . Combining all these ingredients, which were
obtained by different groups, a complete next-to-leading-logarithmic prediction
of the inclusive decay rate was recently presented in the literature. The
theoretical uncertainty in the partonic decay rate is now at the 10% level,
i.e., less than half of the error in the previous leading-logarithmic result.
We also mention the impact of non-perturbative corrections which scale like
and discuss in some more detail the recently discovered corrections
which scale like . It turns out that the - and the
terms lead to corrections to the branching ratio well
below the 10% level.Comment: 11 pages including 2 postscript figure
B\to X_s\gamma, X_s l^+ l^- decays and constraints on the mass insertion parameters in the MSSM
In this paper, we study the upper bounds on the mass insertion parameters
in the minimal supersymmetric standard model (MSSM).
We found that the information from the measured branching ratio of decay can help us to improve the upper bounds on the mass insertions
parameters \left (\delta^{u,d}_{AB})_{3j,i3}. Some regions allowed by the
data of are excluded by the requirement of a SM-like
imposed by the data of .Comment: 16 pages, 5 eps figure files, typos remove
Non-Canonical Perturbation Theory of Non-Linear Sigma Models
We explore the O(N)-invariant Non-Linear Sigma Model (NLSM) in a different
perturbative regime from the usual relativistic-free-field one, by using
non-canonical basic commutation relations adapted to the underlying O(N)
symmetry of the system, which also account for the non-trivial (non-flat)
geometry and topology of the target manifold.Comment: 11 pages, 1 figure, LaTe
NNLL QCD Contribution of the Electromagnetic Dipole Operator to Gamma(anti-B -> X(s) gamma)
We present an independent calculation of that part of the O(\alpha_s^2)
contribution to the decay width \Gamma(\bar B -> X_s \gamma) which arises from
the self-interference term of the electromagnetic dipole operator O_7. Using a
different method, we find complete agreement with a previous calculation. This
NNLL contribution is an important ingredient for the complete NNLL prediction
of \Gamma(\bar B -> X_s \gamma) which will resolve the charm quark mass
ambiguity appearing at NLL accuracy.Comment: 15 pages, uses axodraw.st
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