206,121 research outputs found

    Cross sections for pentaquark baryon production from protons in reactions induced by hadrons and photons

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    Using hadronic Lagrangians that include the interaction of pentaquark Θ+\Theta^+ baryon with KK and NN, 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 μ\mub in proton-proton reactions, and 40 nb in photon-proton reactions.Comment: 14 pages, 7 figure

    TT-adic exponential sums of polynomials in one variable

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    The TT-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 CC-function of the T-adic exponential sum. This bound gives lower bounds for the Newton polygon of the LL-function of exponential sums of pp-power order

    Jet conversions in a quark-gluon plasma

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    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 q(qˉ)g→gq(qˉ)q(\bar q)g\to gq(\bar q) and the inelastic qqˉ↔ggq\bar q\leftrightarrow gg 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 p/π+p/\pi^+ and pˉ/π−{\bar p}/\pi^- 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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