4,985 research outputs found
Lattice-Constrained Parametrizations of Form Factors for Semileptonic and Rare Radiative B Decays
We describe the form factors for semileptonic B to rho l nu and radiative B
to K* gamma decays with just two parameters and the two form factors for
semileptonic B to pi l nu decays with three parameters. The parametrizations
are constrained by lattice results and are consistent with heavy quark
symmetry, kinematic constraints and light cone sum rule scaling relations.Comment: 3 pages, latex, 2 eps files, uses epsf.sty and espcrc2.sty, poster
presented at Lattice 97, Edinburgh, 22-26 July 199
Coordinated thermal and optical observations of Trans-Neptunian object (20000) Varuna from Sierra Nevada
We report on coordinated thermal and optical measurements of trans-Neptunian
object (20000) Varuna obtained in January-February 2002, respectively from the
IRAM 30-m and IAA 1.5 m telescopes. The optical data show a lightcurve with a
period of 3.176+/-0.010 hr, a mean V magnitude of 20.37+/-0.08 and a
0.42+/-0.01 magnitude amplitude. They also tentatively indicate that the
lightcurve is asymmetric and double-peaked. The thermal observations indicate a
1.12+/-0.41 mJy flux, averaged over the object's rotation. Combining the two
datasets, we infer that Varuna has a mean 1060(+180/-220) km diameter and a
mean 0.038(+0.022/-0.010) V geometric albedo, in general agreement with an
earlier determination using the same technique.Comment: Accepted for publication in Astronomy & Astrophysics (7 pages,
including 3 figures
Finite-Size Scaling of Vector and Axial Current Correlators
Using quenched chiral perturbation theory, we compute the long-distance
behaviour of two-point functions of flavour non-singlet axial and vector
currents in a finite volume, for small quark masses, and at a fixed gauge-field
topology. We also present the corresponding predictions for the unquenched
theory at fixed topology. These results can in principle be used to measure the
low-energy constants of the chiral Lagrangian, from lattice simulations in
volumes much smaller than one pion Compton wavelength. We show that quenching
has a dramatic effect on the vector correlator, which is argued to vanish to
all orders, while the axial correlator appears to be a robust observable only
moderately sensitive to quenching.Comment: version to appear in NP
B_K from quenched overlap QCD
We present an exploratory calculation of the standard model Delta S=2 matrix
element relevant for indirect CP violation in K -> pi pi decays. The
computation is performed with overlap fermions in the quenched approximation at
beta=6.0 on a 16^3x32 lattice. The resulting bare matrix element is
renormalized non-perturbatively. Our preliminary result is B_K^{NDR}(2
GeV)=0.61(7), where the error does not yet include an estimate of systematic
uncertainties.Comment: 3 pages, 2 figures, Lattice2002(matrixel). Parallel session talk by
L. Lellouch at the 20th International Symposium on Lattice Field Theory
(Lattice 2002), Boston, Massachusetts, 24-29 June 200
The Thin Gap Chambers database experience in test beam and preparations for ATLAS
Thin gap chambers (TGCs) are used for the muon trigger system in the forward
region of the LHC experiment ATLAS. The TGCs are expected to provide a trigger
signal within 25 ns of the bunch spacing. An extensive system test of the ATLAS
muon spectrometer has been performed in the H8 beam line at the CERN SPS during
the last few years. A relational database was used for storing the conditions
of the tests as well as the configuration of the system. This database has
provided the detector control system with the information needed for
configuration of the front end electronics. The database is used to assist the
online operation and maintenance. The same database is used to store the non
event condition and configuration parameters needed later for the offline
reconstruction software. A larger scale of the database has been produced to
support the whole TGC system. It integrates all the production, QA tests and
assembly information. A 1/12th model of the whole TGC system is currently in
use for testing the performance of this database in configuring and tracking
the condition of the system. A prototype of the database was first implemented
during the H8 test beams. This paper describes the database structure, its
interface to other systems and its operational performance.Comment: Proceedings IEEE, Nuclear Science Symposium 2005, Stockholm, Sweeden,
May 200
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