10,995,908 research outputs found
Mass splittings and matrix elements of mesons and baryons containing a single heavy quark
We present a study in the quenched approximation of the parameter
and the decay constant using heavy-quark propagators implemented in the
static approximation, and light-quark propagators computed using an
-improved fermion action. We find a value of \Bbstat close unity, and
discuss the systematic errors entering into the calculation. \fbstat is
extracted using a variational fitting technique in order to obtain a reliable
estimate of the ground state.
In the second part of the talk, we describe an exploratory study of baryons
containing a single heavy quark, computed using the -improved fermion
action. We obtain masses generally in good agreement with experiment in both
the charm and beauty sectors. We also report preliminary results for the form
factor in the semi-leptonic transition.Comment: 6 pages, uuencoded compressed postscript file, to be published in the
Proceedings of Lattice 9
Results from Lattice QCD for baryons containing a heavy quark
We present the calculation of the spectrum of baryons containing one heavy
quark. Heavy baryon and meson mass splittings are computed and compared with
experiment. We give preliminary results for the form factor for the
semileptonic decay and
investigate its flavour symmetry.Comment: 3 pages, uuencoded, Proceedings of the EPS/HEP95 conferenc
Charmed Meson Spectroscopy and Matrix Elements with an O(a)-Improved Clover Fermion Action
We present preliminary results for the spectrum and decay matrix elements for
heavy-light and heavy-heavy mesons, obtained on the 64-node Meiko Computing
Surface at the University of Edinburgh. Quark propagators are computed with an
O(a)-improved fermion action on 24^3x48 lattices at beta = 6.2, using three
values of the quark mass up to around the strange quark mass, and four values
of the quark mass in the region of the charm quark mass. We compare results for
the hyperfine splitting in charmonium with those obtained using the
conventional Wilson fermion action and find that the splitting is 1.83(15)
times larger with the improved action. Our measurements of f_B indicate
non-scaling corrections of the order of 20% to the Heavy Quark Effective Theory
expectation. A comparison is made with results obtained on 16^3x48 lattices at
beta = 6.0.Comment: at Lattice '92, 4 pages latex + 3 postscript figures, Edinburgh
Preprint 92/51
Measurement of the hadronic cross section at KLOE using the radiative return
We report on the measurement of the hadronic cross section below 1GeV at the
electron-positron-collider DAPHNE, using the multiple purpose detector KLOE.
The radiative return, which is due to initial state radiation (e+ e- \to gamma
+ hadrons), allows us to obtain the cross section for variable
center-of-mass-energies of the hadronic system from the 2m_pi threshold up to
1.02GeV. This measurement can be performed while DAPHNE is running with a fixed
accelerator energy on the phi mass (1.02 GeV). For the exclusive process e+ e-
\to pi+ pi- gamma, the status of the analysis and first preliminary results of
the invariant mass spectrum of the two-pion-state are presented.Comment: Invited talk at the workshop "e+e- Physics at Intermediate Energies",
SLAC, April 30 - May 2, 2001 (T07
Study of Gamma-Ray Bursts of energy E>10 GeV with the ARGO-YBJ detector
The study of high energy gamma-ray bursts can be performed by large area air
shower arrays operating at very high mountain altitudes. ARGO-YBJ is a detector
optimized to observe small size air showers, to be constructed at the
Yangbajing Laboratory (Tibet, P.R. China) at an altitude of 4300 m. One of the
goals of the experiment is the study of Gamma-Ray Bursts of energies E > 10
GeV. This can be achieved using the "single particle" technique, more
profitable in the energy region E < 50 GeV, and the "low multiplicity"
technique, suitable to observe GRBs at higher energies. The sensitiviy of
ARGO-YBJ allows the detection of GRBs with energy fluences in the range 1--100
GeV as low as F~10^{-6} -- 10^{-5} erg cm^{-2}, depending on the spectral
characteristics of the burst.Comment: 4 pages, 2 figures, to appear in the proceedings of 26th
International Cosmic Ray Conference (Salt Lake City, 1999
Quenched Light Hadron Spectroscopy: Comparing the Wilson and O(a)-Improved Fermion Actions
We have studied the light hadron spectrum and decay constants for quenched
QCD at beta=6.2 on a 24^3x48 lattice. We compare the results obtained using a
nearest-neighbour O(a)-improved ("clover") fermion action with those obtained
using the standard Wilson fermion action on the same gauge configurations. For
pseudoscalar meson masses in the range 330-800 MeV, we find no significant
difference between the results for the two actions. The scales obtained from
the string tension and mesonic sector are consistent, but higher than those
derived from baryon masses. The ratio of the pseudoscalar decay constant to the
vector meson mass is roughly independent of quark mass as observed
experimentally.Comment: at Lattice '92, 4 pages, Edinburgh Preprint: 92/51
Gamma-Hadron Discrimination with a Neural Network in the ARGO-YBJ Experiment
The structure of a neural network developed for the gamma hadron separation
in the ARGO-YBJ detector is presented. The discrimination power in the full
ARGO-YBJ energy range is shown in detail and the improvement in the detector
sensitivity is also discussed.Comment: 4 pages, 4 figures, to appear in the proceedings of the 26th
International Cosmic Ray Conference (Salt Lake City, 1999
Performance of RPCs operated at the YangBaJing Laboratory
The ARGO-YBJ experiment will be installed at YangBaJing Cosmic Ray Laboratory
(Tibet, P.R. China), 4300 m a.s.l. . It consists of a full coverage of about
10^4 m^2 realized with RPC chambers.
A small carpet of about 50 m^2 has been operated at YangBaJing in order to
check the RPC performance in these high altitude conditions.
Results concerning efficiency and time resolution are reported.Comment: 4 pages, 4 figures, to appear in the proceedings of 26th
International Cosmic Ray Conference (Salt Lake City, 1999
Underground Muons in Super-KAMIOKANDE
The largest underground neutrino observatory, Super-Kamiokande, located near
Kamioka, Japan has been collecting data since April 1996. It is located at a
depth of roughly 2.7 kmwe in a zinc mine under a mountain, and has an effective
area for detecting entering-stopping and through-going muons of about for muons of . These events are collected at a rate of 1.5 per
day from the lower hemisphere of arrival directions, with 2.5 muons per second
in the downgoing direction.
We report preliminary results from 229 live days analyzed so far with respect
to zenith angle variation of the upcoming muons. These results do not yet have
enough statistical weight to discriminate between the favored hypothesis for
muon neutrino oscillations and no-oscillations. We report on the search for
astrophysical sources of neutrinos and high energy neutrino fluxes from the sun
and earth center, as might arise from WIMP annihilations. None are found. We
also present a topographical map of the overburden made from the downgoing
muons. The detector is performing well, and with several years of data we
should be able to make significant progress in this area.Comment: 4pages, 6 figure
Compactly presented groups
This survey purports to be an elementary introduction to compactly presented
groups, which are the analogue of finitely presented groups in the broader
realm of locally compact groups. In particular, compact presentation is
interpreted as a coarse simple connectedness condition on the Cayley graph, and
in particular is a quasi-isometry invariant. In the appendix, an example of a
Lie group, not quasi-isometric to any homogeneous graph, is given; the short
argument relies on results of Trofimov and Pansu, anterior to~1990.Comment: Preliminary version (13 pages). Comments welcome
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