18 research outputs found
Order alpha_s^2 beta_0 Correction to the Charged Lepton Spectrum in b \to c \ell \bar\nu_\ell decays
We compute the \alpha_s^2\beta_0 part of the two-loop QCD corrections to the
charged lepton spectrum in b \to c \ell \bar\nu_\ell decays and find them to be
about 50\% of the first order corrections at all lepton energies, except those
close to the end point. Including these corrections we extract the central
values \bar\Lambda=0.33 GeV and \lambda_1=-0.17 GeV^2 for the HQET matrix
elements and use them to determine the b and c quark
masses, and |V_{cb}|.Comment: 15 pages, 1 Postscript figur
Updated Analysis of a_1 and a_2 in Hadronic Two-body Decays of B Mesons
Using the recent experimental data of , , and various model calculations on form
factors, we re-analyze the effective coefficients a_1 and a_2 and their ratio.
QCD and electroweak penguin corrections to a_1 from and
a_2 from are estimated. In addition to the
model-dependent determination, the effective coefficient a_1 is also extracted
in a model-independent way as the decay modes are related by
factorization to the measured semileptonic distribution of at . Moreover, this enables us to extract model-independent
heavy-to-heavy form factors, for example,
and
. The determination of the magnitude of
a_2 from depends on the form factors ,
and at . By requiring that a_2 be
process insensitive (i.e., the value of a_2 extracted from and
states should be similar), as implied by the factorization
hypothesis, we find that form factors are severely constrained;
they respect the relation . Form factors and at
inferred from the measurements of the longitudinal
polarization fraction and the P-wave component in are
obtained. A stringent upper limit on a_2 is derived from the current bound on
\ov B^0\to D^0\pi^0 and it is sensitive to final-state interactions.Comment: 33 pages, 2 figures. Typos in Tables I and IX are corrected. To
appear in Phys. Rev.
Hadron Spectra for Semileptonic Heavy Quark Decay
We calculate the leading perturbative and power corrections to the hadronic
invariant mass and energy spectra in semileptonic heavy hadron decays. We apply
our results to the system. Moments of the invariant mass spectrum, which
vanish in the parton model, probe gluon bremsstrahlung and nonperturbative
effects. Combining our results with recent data on meson branching ratios,
we obtain a lower bound and an upper bound
GeV. The Brodsky-Lepage-Mackenzie scale setting
procedure suggests that higher order perturbative corrections are small for
bottom decay, and even tractable for charm decay.Comment: 24 pages, uses REVTeX, 5 EPS figures embedded with epsf.sty, slightly
modified version to appear in Phys. Rev.
Phenomenology of the Expansion in Inclusive and Meson Decays
We apply a recent theoretical analysis of hadronic observables in inclusive
semileptonic heavy hadron decays to the phenomenology of and mesons.
Correlated bounds on the nonperturbative parameters and
are derived by considering data from decays and, independently,
data from decays. The two sets of bounds are found to be consistent with
each other. The data from decays are then are used to extract a lower limit
on the CKM matrix element . We address the issue of the convergence
of the perturbative expansions used in the analysis, and compare our bounds on
and to lattice and QCD sum rule results. Finally, we
argue that a comparison of the analyses of and decays provides
evidence for the applicability of parton-hadron duality in the semileptonic
decay of charmed hadrons.Comment: 18 pages, 3 embedded figures, uses REVTeX and epsf.sty; this is the
slightly revised version to appear in Physical Review
Final-State Phases in Charmed Meson Two-Body Nonleptonic Decays
Observed decay rates indicate large phase differences among the amplitudes
for the charge states in and but
relatively real amplitudes in the charge states for . This
feature is traced using an SU(3) flavor analysis to a sign flip in the
contribution of one of the amplitudes contributing to the latter processes in
comparison with its contribution to the other two sets. This amplitude may be
regarded as an effect of rescattering and is found to be of magnitude
comparable to others contributing to charmed particle two-body nonleptonic
decays.Comment: 19 pages, latex, 4 figures, to be submitted to Phys. Rev.
Resummation of Running Coupling Effects in Semileptonic B Meson Decays and Extraction of
We present a determination of from semileptonic B decays that
includes resummation of supposedly large perturbative corrections, originating
from the running of the strong coupling. We argue that the low value of the BLM
scale found previously for inclusive decays is a manifestation of the
renormalon divergence of the perturbative series starting already in third
order. A reliable determination of from inclusive decays is possible
if one either uses a short-distance b quark mass or eliminates all unphysical
mass parameters in terms of measured observables, such that all infra-red
contributions of order cancel explicitly. We find that using the
running mass significantly reduces the perturbative
coefficients already in low orders. For a semileptonic branching ratio of
we obtain from
inclusive decays, in good agreement with the value extracted from exclusive
decays.Comment: 37 pages + 4 figures, final version accepted for publication in Phys.
Rev.
Hidradenitis suppurativa/acne inversa: a practical framework for treatment optimization – systematic review and recommendations from the HS ALLIANCE working group
Hidradenitis suppurativa (HS)/acne inversa is a debilitating chronic disease that remains poorly understood and difficult to manage. Clinical practice is variable, and there is a need for international, evidence-based and easily applicable consensus on HS management. We report here the findings of a systematic literature review, which were subsequently used as a basis for the development of international consensus recommendations for the management of patients with HS. A systematic literature review was performed for each of nine clinical questions in HS (defined by an expert steering committee), covering comorbidity assessment, therapy (medical, surgical and combinations) and response to treatment. Included articles underwent data extraction and were graded according to the Oxford Centre for Evidence-based Medicine criteria. Evidence-based recommendations were then drafted, refined and voted upon, using a modified Delphi process. Overall, 5310 articles were screened, 171 articles were analysed, and 65 were used to derive recommendations. These articles included six randomized controlled trials plus cohort studies and case series. The highest level of evidence concerned dosing recommendations for topical clindamycin in mild disease (with systemic tetracyclines for more frequent/widespread lesions) and biologic therapy (especially adalimumab) as second-line agents (following conventional therapy failure). Good-quality evidence was available for the hidradenitis suppurativa clinical response (HiSCR) as a dichotomous outcome measure in inflammatory areas under treatment. Lower-level evidence supported recommendations for topical triclosan and oral zinc in mild-to-moderate HS, systemic clindamycin and rifampicin in moderate HS and intravenous ertapenem in selected patients with more severe disease. Intralesional or systemic steroids may also be considered. Local surgical excision is suggested for mild-to-moderate HS, with wide excision for more extensive disease. Despite a paucity of good-quality data on management decisions in HS, this systematic review has enabled the development of robust and easily applicable clinical recommendations for international physicians based on graded evidence
Flucloxacillin-associated hepatic injury
Eleven cases of hepatic injury attributed to the intake of flucloxacillin were reported to the Netherlands Center for Monitoring of Adverse Reactions to Drugs between 1982 and 1992. They concerned four men and seven women, with a mean age of 57 years, treated for 2-28 days with an oral dose varying from 1500-4000 mg per day. Symptoms mostly appeared 10 to 30 days after starting treatment with flucloxacillin. Biochemically, the pattern was compatible with cholestatic hepatitis in seven cases, with a mixed cholestatic-hepatocellular type of injury in one case, a hepatocellular pattern in two cases, and mild liver enzyme elevations in one patient. Two patients died, one due to fatal bleeding from the liver after biopsy, and the second patient to a combination of hepatic and cardiac failure. The other patients recovered, on average 72 days after peaking of serum aminotransferase values. Histology in seven cases showed cholestatic hepatitis in five, with cholangitis or cholangiolitis in four of these patients. In the other two patients, there was centrilobular cholestasis with extensive bridging fibrosis and portal-central bridging necrosis, respectively