203,718 research outputs found
Cross sections for pentaquark baryon production from protons in reactions induced by hadrons and photons
Using hadronic Lagrangians that include the interaction of pentaquark
baryon with and , we evaluate the cross sections for its
production from meson-proton, proton-proton, and photon-proton reactions near
threshold. With empirical coupling constants and form factors, the predicted
cross sections are about 1.5 mb in kaon-proton reactions, 0.1 mb in rho-nucleon
reactions, 0.05 mb in pion-nucleon reactions, 20 b in proton-proton
reactions, and 40 nb in photon-proton reactions.Comment: 14 pages, 7 figure
-adic exponential sums of polynomials in one variable
The -adic exponential sum of a polynomial in one variable is studied. An
explicit arithmetic polygon in terms of the highest two exponents of the
polynomial is proved to be a lower bound of the Newton polygon of the
-function of the T-adic exponential sum. This bound gives lower bounds for
the Newton polygon of the -function of exponential sums of -power order
Jet conversions in a quark-gluon plasma
Quark and gluon jets traversing through a quark-gluon plasma not only lose
their energies but also can undergo flavor conversions. The conversion rates
via the elastic and the inelastic scatterings are evaluated in the lowest order in QCD.
Including both jet energy loss and conversions in the expanding quark-gluon
plasma produced in relativistic heavy ion collisions, we have found a net
conversion of quark to gluon jets. This reduces the difference between the
nuclear modification factors for quark and gluon jets in central heavy ion
collisions and thus enhances the and ratios at high
transverse momentum. However, a much larger net quark to gluon jet conversion
rate than the one given by the lowest-order QCD is needed to account for the
observed similar ratios in central Au+Au and p+p collisions at same energy.
Implications of our results are discussed.Comment: version to appear in PR
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