3,669 research outputs found
The Mass Definition in Hqet and a New Determination of V
Positive powers of the mass parameter in a physical quantity calculated with
the help of heavy quark effective theory originate from a Wilson coefficient in
the matching of QCD and HQET Green function. We show that this mass parameter
enters the calculation as a well--defined running current mass. We further
argue that the recently found ill--definition of the pole mass, which is the
natural expansion parameter of HQET, does not affect a phenomenological
analysis which uses truncated perturbative series. We reanalyse inclusive
semileptonic decays of heavy mesons and obtain the quark mass
where the error
is almost entirely due to scale--uncertainties. We also obtain
and
where the errors come
from the uncertainty in the kinetic energy of the heavy quark inside the meson,
in the experimental branching ratios, in QCD input parameters, and
scale--uncertainties.Comment: 21 p., 5 figs, all style files incl., TUM-T31-56/R (Sec. 2 revised,
phenomenological results unchanged
Journal Staff
Primary Immunodeficiencies (PID) are genetically inherited disorders characterized by defects of the immune system, leading to increased susceptibility to infection. Due to the variety of clinical symptoms and the complexity of current diagnostic procedures, accurate diagnosis of PID is often difficult in daily clinical practice. Thanks to the advent of "next generation'' sequencing technologies and target enrichment methods, the development of multiplex diagnostic assays is now possible. In this study, we applied a selector-based target enrichment assay to detect disease-causing mutations in 179 known PID genes. The usefulness of this assay for molecular diagnosis of PID was investigated by sequencing DNA from 33 patients, 18 of which had at least one known causal mutation at the onset of the experiment. We were able to identify the disease causing mutations in 60% of the investigated patients, indicating that the majority of PID cases could be resolved using a targeted sequencing approach. Causal mutations identified in the unknown patient samples were located in STAT3, IGLL1, RNF168 and PGM3. Based on our results, we propose a stepwise approach for PID diagnostics, involving targeted resequencing, followed by whole transcriptome and/or whole genome sequencing if causative variants are not found in the targeted exons
Higher Order Corrections at Zero Recoil
The general structure of the corrections at zero recoil is studied. The
relevant matrix elements are forward matrix elements of local higher
dimensional operators and their time ordered products with higher order terms
from the Lagrangian. These matrix elements may be classified in a simple way
and the analysis at the non recoil point for the form factor of heavy quark
currents simplifies drastically. The second order recoil corrections to the
form factor of the axial vector current, relevant for the
determination from decays, are estimated to be .Comment: LaTeX, 25 pages, one figure, appended after \end{document} as
uu-encoded and compressed eps file, uses epsf, CERN-TH.7162/9
Sum rules in the heavy quark limit of QCD
In the leading order of the heavy quark expansion, we propose a method within
the OPE and the trace formalism, that allows to obtain, in a systematic way,
Bjorken-like sum rules for the derivatives of the elastic Isgur-Wise function
in terms of corresponding Isgur-Wise functions of transitions to
excited states. A key element is the consideration of the non-forward
amplitude, as introduced by Uraltsev. A simplifying feature of our method is to
consider currents aligned along the initial and final four-velocities. As an
illustration, we give a very simple derivation of Bjorken and Uraltsev sum
rules. On the other hand, we obtain a new class of sum rules that involve the
products of IW functions at zero recoil and IW functions at any . Special
care is given to the needed derivation of the projector on the polarization
tensors of particles of arbitrary integer spin. The new sum rules give further
information on the slope and also on the curvature
, and imply, modulo a very natural assumption, the
inequality , and therefore the absolute bound
.Comment: 64 pages, Late
On the Determination of from Inclusive Semileptonic Decay Spectra
We propose a model independent method to determine from the energy
spectrum of the charged lepton in inclusive semileptonic decays. The method
includes perturbative QCD corrections as well as nonperturbative ones.Comment: LaTeX, 19 pages, 8 figures appended after \end{document} as
uu-encoded and compressed .eps files, uses epsf, Technion-PH-94/9,
CERN-TH.7308/9
Determining V(ub) from B+ --> D*+(s) e+ e- and B+ --> D*+ e+ e-
It was recently pointed out that the decays B^+ --> D^{*+}_s gamma and B^+
--> D^{*+} gamma can be used for an extraction of |V_{ub}|. The theory of these
decays is poorly understood. It was shown that in a world of almost degenerate
b and c-quarks the decay would be computable. The severe difficulties that are
encountered in the realistic calculation stem primarily from the very hard
photon produced in the two body decay. We point out that in the decays B^+ -->
D^{*+}_s e^+e^- and B^+ --> D^{*+} e^+e^- the photon vertex is soft when the
charmed meson is nearly at rest (in the B^+ rest frame). This allows us to
compute with some confidence the decay rate in a restricted but interesting
kinematic regime. Given enough data the extraction of V_{ub} with reasonably
small uncertainties could proceed through an analysis of these exclusive decays
much as is done in the determination of V_{cb}.Comment: 9 pages, latex (revtex), replaced with published versio
Model independent results for and at order
Exclusive semileptonic B decays into and mesons are
investigated including order corrections using the
heavy quark effective theory. At zero recoil, the
corrections can be written in terms of the leading Isgur-Wise function for
these transitions, , and known meson mass splittings. We obtain an almost
model independent prediction for the shape of the spectrum near zero recoil,
including order corrections. We determine
from the measured branching ratio. Implications for B
decay sum rules are discussed.Comment: 11 pages, revte
1/m_b^2 correction to the left-right lepton polarization asymmetry in the decay B -> X_s mu^+ mu^-
Using a known result by Falk et al. for the 1/m_b^2 correction to the
dilepton invariant mass spectrum in the decay B \rightarrow X_s \mu^+ \mu^-, we
calculate the 1/m_b^2 correction to the left-right muon polarization asymmetry
in this decay. Employing an up-to-date range of values for the non-perturbative
parameter \lambda_1, we find that the correction is much smaller than it should
have been expected from the previous work by Falk et al.Comment: 8 pages, 2 figures included. Uses epsf.sty and rotate.sty. To appear
in Physical Review D. The complete postscript file is also available from URL
ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/ tum_t31_98_96.ps.g
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