5,517 research outputs found

    Introduction to Nuclear and Particle Physics

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    Studies of neutron dissociation at FermiLab energies

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    The characteristics of diffraction dissociation of neutrons into ppipisupsup - 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 ppipisupsup - amplitudes at low mass is very complex, but is described surprisingly well by the simple Deck Mechanism. Both pipi-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

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    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 O(αs2)O(\alpha_s^2) Perturbative QCD

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    The results of analytical evaluation of O(αs2)O(\alpha_s^2) QCD contributions due to the nonvanishing quark masses to ΓHqfqf\Gamma_{H\rightarrow q_f\overline{q}_f} are presented. The ``triangle anomaly'' type contributions are included. As a byproduct the O(αs3)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 HbbH \rightarrow b\overline{b} and HccH \rightarrow c\overline{c} are considered. The calculated corrections decrease the absolute value of large and negative O(αs2)O(\alpha_s^2) massless limit coefficient by 1%\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 HttH \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 ΓHqfqf\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.

    THGEM operation in Ne and Ne/CH4

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    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

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    We study the gravitational clustering of big bang relic neutrinos onto existing cold dark matter (CDM) and baryonic structures within the flat Λ\LambdaCDM 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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