9,952 research outputs found
Lattice analysis of semi-leptonic form factors
We present preliminary results from simulations done on 170
lattices at using quenched Wilson fermions. This talk focuses on
the behavior of the form-factors, extrapolation in quark masses,
dependence on renormalization scheme, and comparison with heavy-quark effective
theory (HQET). Even though we cannot estimate errors due to quenching and
discretization, our results are consistent with experimental results for
decays. We present results for the Isgur-Wise function and estimate .Comment: 4 pages. Talk presented at Lattice 95. Latex. Modified "axis" source
for figures also include
Wilson versus Clover fermions: A case for improvement
We present evidence for improvement with tadpole improved clover fermions
based on an analysis of the chiral behavior of and the quark condensate.
Also presented are a comparison of the mass splittings in the baryon octet and
decuplet, a calculation of using standard 2-point correlation functions,
and the problem of zero modes of the Dirac operator.Comment: 3 pages. Makefile and sources included. Talk presented at LATTICE98
(matrixelement
Testing the chiral behavior of the hadron spectrum
We analyze the chiral behavior of the hadron spectrum obtained with quenched
Wilson fermions on 170 lattices at . We calculate
masses of hadrons composed of both degenerate and non-degenerate quarks. We
reduce the statistical errors in mass splittings by directly fitting to the
ratio of correlation functions. We find significant deviations from a linear
dependence on the quark mass, deviations that are consistent with the higher
order terms predicted by quenched chiral perturbation theory. Including these
corrections yields splittings in the baryon octet that agree with those
observed experimentally. Smaller higher order terms are also present in
and . By contrast, the decuplet baryons are well described by a
linear mass term. We find the decuplet splittings to be 30% smaller than
experiment. We extrapolate our data to by combining with the GF11
results, and the best fit suggests that the quenched approximation is only good
to .Comment: 4 pages. Poster presented at Lattice 95. Latex with modified "axis"
source for figures also include
The Direct Detection of Boosted Dark Matter at High Energies and PeV events at IceCube
We study the possibility of detecting dark matter directly via a small but
energetic component that is allowed within present-day constraints. Drawing
closely upon the fact that neutral current neutrino nucleon interactions are
indistinguishable from DM-nucleon interactions at low energies, we extend this
feature to high energies for a small, non-thermal but highly energetic
population of DM particle , created via the decay of a significantly more
massive and long-lived non-thermal relic , which forms the bulk of DM. If
interacts with nucleons, its cross-section, like the neutrino-nucleus
coherent cross-section, can rise sharply with energy leading to deep inelastic
scattering, similar to neutral current neutrino-nucleon interactions at high
energies. Thus, its direct detection may be possible via cascades in very large
neutrino detectors. As a specific example, we apply this notion to the recently
reported three ultra-high energy PeV cascade events clustered around PeV
at IceCube (IC). We discuss the features which may help discriminate this
scenario from one in which only astrophysical neutrinos constitute the event
sample in detectors like IC.Comment: v1: 6 pages, 4 figures; v2: More references added, minor text changes
for clarification; v3: Title change, major revision, updated references; v4:
Corrected Fig. 1b, Version published in JCA
Fixed-point pure gauge action using RGT
We present a status report on the construction of the classical perfect
action using the renormalization group transformation (RGT). We
investigate finite volume corrections and map the locality of the fixed-point
action by tuning the RGT parameter, . We compare results with the
previous calculation for b=2 RGT.Comment: 3 pages. Contribution to LATTICE99(Improvement and Renormalization),
June 1999, Pisa, Ital
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