84 research outputs found
Subleading Power Factorization in
We analyze the factorization to subleading power in the flavor changing
neutral current process . In particular, we
compute the so-called resolved contributions and explore the numerical impact
on observables. In these contributions the virtual photon couples to light
partons instead of connecting directly to the effective weak-interaction
vertex. They represent an irreducible uncertainty in the inclusive decay which cannot be removed by relaxing the experimentally
necessary cuts in the hadronic mass spectrum.Comment: 32 pages,18 figure
Long-Distance Dominance of the CP Asymmetry in B->X_{s,d}+gamma Decays
We show that in the Standard Model the parametrically leading (by a factor
1/alpha_s) contribution to the inclusive CP asymmetry in B->X_{s,d}+gamma
decays arises from a long-distance effect in the interference of the
electromagnetic dipole amplitude with the amplitude for an up-quark penguin
transition accompanied by soft gluon emission. This contribution is governed by
a single hadronic parameter Lambda_{17}^u related to a matrix elements of a
non-local operator. In view of current experimental data, a future precision
measurement of the flavor-averaged CP asymmetry in B->X_s+gamma will signal the
presence of new physics only if a value below -2% is found. A cleaner probe of
new physics is offered by the difference of the CP asymmetries in charged
versus neutral B-meson decays.Comment: 4 page
Resolved contributions to and
In view of the importance of the nonperturbative resolved contributions for
the overall uncertainties of the two inclusive penguin decays and we reanalyse these contributions
using new estimates of moments of the subleading shape functions and of other
input parameters. Within a systematic approach we find a significant reduction
of the nonperturbative uncertainties in the inclusive decay , but a much less pronounced reduction in the inclusive decay
compared to a recent analysis on the resolved
contributions to the inclusive decay . We identify the
reasons for this discrepancy.Comment: minor changes, matches published versio
Prompt neutrinos from atmospheric charm in the general-mass variable-flavor-number scheme
We present predictions for the prompt-neutrino flux arising from the decay of
charmed mesons and baryons produced by the interactions of high-energy cosmic
rays in the Earth's atmosphere, making use of a QCD approach on the basis of
the general-mass variable-flavor-number scheme for the description of charm
hadroproduction at NLO, complemented by a consistent set of fragmentation
functions. We compare the theoretical results to those already obtained by our
and other groups with different theoretical approaches. We provide comparisons
with the experimental results obtained by the IceCube Collaboration in two
different analyses and we discuss the implications for parton distribution
functions.Comment: 43 pages, 21 figures, updated version, to be published in JHE
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
in the Two Higgs Doublet Model up to Next-to-Next-to-Leading Order in QCD
We compute three-loop matching corrections to the Wilson coefficients
and in the Two Higgs Doublet Model by applying expansions for small,
intermediate and large charged Higgs boson masses. The results are used to
evaluate the branching ratio of to next-to-next-to
leading order accuracy, and to determine an updated lower limit on the charged
Higgs boson mass. We find \mhplus \ge 380 GeV at 95% confidence level when
the recently completed BABAR data analysis is taken into account. Our results
for the charged Higgs contribution to the branching ratio exhibit considerably
weaker sensitivity to the matching scale , as compared to previous
calculations.Comment: 20 pages, 15 figures; v2: minor modifications, matches published
version in JHE
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