5,557 research outputs found
Studies of neutron dissociation at FermiLab energies
The characteristics of diffraction dissociation of neutrons into p systems at high energies were examined. A substantial correlation is observed between the mass and the t of the produced system. The spin structure of the p amplitudes at low mass is very complex, but is described surprisingly well by the simple Deck Mechanism. Both -exchange and proton-exchange contributions are evident in diffractive production. The t- channel and s-channel helicity amplitudes contain comparable contributions from flip and nonflip terms and the produced states are not restricted to those expected on the basis of the Morrison rule. (auth
Prospects for probing the gluon density in protons using heavy quarkonium hadroproduction
We examine carefully bottomonia hadroproduction in proton colliders,
especially focusing on the LHC, as a way of probing the gluon density in
protons. To this end we develop some previous work, getting quantitative
predictions and concluding that our proposal can be useful to perform
consistency checks of the parameterization sets of different parton
distribution functions.Comment: LaTeX, 14 pages, 6 EPS figure
Quark Mass Effects in Fermionic Decays of the Higgs Boson in Perturbative QCD
The results of analytical evaluation of QCD contributions due
to the nonvanishing quark masses to
are presented. The ``triangle anomaly'' type contributions are included. As a
byproduct the logarithmic contributions are evaluated. The
results are presented both in terms of running and pole quark masses. The
partial decay modes and are considered. The calculated corrections decrease the absolute
value of large and negative massless limit coefficient by in the intermediate mass region and by 1\%20\% in the low mass region
which, however, is experimentally ruled out.
The results are relevant for decay mode for the
higher Higgs mass region where the mass effects are large and important. The
high order corrections remove a very large discrepancy between the results for
in terms of running and pole quark
masses almost completely and reduce the scale dependence from about 40\% to
nearly 5\%.Comment: 16 pages, LATeX, +5 figures available upon request, preprint OITS-543
(University of Oregon, USA, May 1994). ( Additions are made: Previous general
result for the H-->qq is applied to the H-->tt decay mode where the
calculated corrections are significant.
THGEM operation in Ne and Ne/CH4
The operation of Thick Gaseous Electron Multipliers (THGEM) in Ne and Ne/CH4
mixtures, features high multiplication factors at relatively low operation
potentials, in both single- and double-THGEM configurations. We present some
systematic data measured with UV-photons and soft x-rays, in various Ne
mixtures. It includes gain dependence on hole diameter and gas purity,
photoelectron extraction efficiency from CsI photocathodes into the gas,
long-term gain stability and pulse rise-time. Position resolution of a 100x100
mm^2 X-rays imaging detector is presented. Possible applications are discussed.Comment: Submitted to JINST, 25 pages, 33 figure
Gravitational clustering of relic neutrinos and implications for their detection
We study the gravitational clustering of big bang relic neutrinos onto
existing cold dark matter (CDM) and baryonic structures within the flat
CDM model, using both numerical simulations and a semi-analytical
linear technique, with the aim of understanding the neutrinos' clustering
properties for direct detection purposes. In a comparative analysis, we find
that the linear technique systematically underestimates the amount of
clustering for a wide range of CDM halo and neutrino masses. This invalidates
earlier claims of the technique's applicability. We then compute the exact
phase space distribution of relic neutrinos in our neighbourhood at Earth, and
estimate the large scale neutrino density contrasts within the local
Greisen--Zatsepin--Kuzmin zone. With these findings, we discuss the
implications of gravitational neutrino clustering for scattering-based
detection methods, ranging from flux detection via Cavendish-type torsion
balances, to target detection using accelerator beams and cosmic rays. For
emission spectroscopy via resonant annihilation of extremely energetic cosmic
neutrinos on the relic neutrino background, we give new estimates for the
expected enhancement in the event rates in the direction of the Virgo cluster.Comment: 38 pages, 8 embedded figures, iopart.cls; v2: references added, minor
changes in text, to appear in JCA
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