Quark Mass Effects in Fermionic Decays of the Higgs Boson in O(αs2)O(\alpha_s^2) Perturbative QCD

The results of analytical evaluation of $O(\alpha_s^2)$ QCD contributions due to the nonvanishing quark masses to $\Gamma_{H\rightarrow q_f\overline{q}_f}$ are presented. The ``triangle anomaly'' type contributions are included. As a byproduct the $O(\alpha_s^3)$ logarithmic contributions are evaluated. The results are presented both in terms of running and pole quark masses. The partial decay modes $H \rightarrow b\overline{b}$ and $H \rightarrow c\overline{c}$ are considered. The calculated corrections decrease the absolute value of large and negative $O(\alpha_s^2)$ massless limit coefficient by $\leq 1\%$ 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 $H \rightarrow t\overline{t}$ 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 $\Gamma_{H\rightarrow q_f\overline{q}_f}$ 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.

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

Studies of neutron dissociation at FermiLab energies

The characteristics of diffraction dissociation of neutrons into p$pi$$sup -$ systems at high energies were examined. A substantial correlation is observed between the mass and the t of the produced system. The spin structure of the p$pi$$sup -$ amplitudes at low mass is very complex, but is described surprisingly well by the simple Deck Mechanism. Both $pi$-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

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 $\Lambda$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

Photons from Quark Gluon Plasma and Hot Hadronic Matter

The productions of real photons from quark gluon plasma and hot hadronic matter formed after the nucleus - nucleus collisions at ultra-relativistic energies are discussed. The effects of the spectral shift of the hadrons at finite temperature on the production of photons are investigated. On the basis of the present analysis it is shown that the photon spectra measured by WA98 collaboration in Pb + Pb collisions at CERN SPS energies can be explained by both QGP as well as hadronic initial states if the spectral shift of hadrons at finite temperature is taken into account. Several other works on the analysis of WA98 photon data have also been briefly discussed.Comment: Latex file, six eps figures include