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Search Results: 1 - 10 of 544662 matches for " C. M. Ko "
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Medium effects on the flow of strange particles in heavy ion collisions
C. M. Ko
Physics , 2000, DOI: 10.1088/0954-3899/27/3/310
Abstract: Strange particles such as the kaon and lambda are useful in probing the properties of dense matter formed in heavy ion collisions. We review in this talk the theoretical understandings of their properties in nuclear medium based on both the effective chiral Lagrangian and the phenomenological hadronic model. We further review the effects due to changes in their in-medium properties on their collective flow in heavy ion collisions.
Secondary phi meson peak as an indicator of QCD phase transition in ultrarelativistic heavy ion collisions
M. Asakawa,C. M. Ko
Physics , 1994, DOI: 10.1103/PhysRevC.50.3064
Abstract: In a previous paper, we have shown that a double phi peak structure appears in the dilepton invariant mass spectrum if a first order QCD phase transition occurs in ultrarelativistic heavy ion collisions. Furthermore, the transition temperature can be determined from the transverse momentum distribution of the low mass phi peak. In this work, we extend the study to the case that a smooth crossover occurs in the quark-gluon plasma to the hadronic matter transition. We find that the double phi peak structure still exists in the dilepton spectrum and thus remains a viable signal for the formation of the quark-gluon plasma in ultrarelativistic heavy ion collisions.
Seeing the QCD phase transition with phi mesons
M. Asakawa,C. M. Ko
Physics , 1994, DOI: 10.1016/0370-2693(94)90487-1
Abstract: A double phi peak structure in the dilepton invariant mass spectrum from ultrarelativistic heavy ion collisions is proposed as a signal for the phase transition from the quark-gluon plasma to the hadronic matter. The low mass phi peak results from the decay of phi mesons with reduced in-medium mass during the transition. Furthermore, the measurement of the transverse momentum distribution of these low mass phi mesons offers a viable means for determining the temperature of the phase transition.
Hadronization via Coalescence
V. Greco,C. M. Ko
Physics , 2004, DOI: 10.1556/APH.24.2005.1-4.32
Abstract: We review the quark coalescence model for hadronization in relativistic heavy ion collisions and show how it can explain the observed large baryon to meson ratio at intermediate transverse momentum and scaling of the elliptic flows of identified hadrons. We also show its predictions on higher-order anisotropic flows and discuss how quark coalescence applied to open- and hidden-charm mesons can give insight to charm quark interactions in the quark-gluon plasma and $J/\Psi$ production in heavy ion collisions.
Cross sections for pentaquark baryon production from protons in reactions induced by hadrons and photons
W. Liu,C. M. Ko
Physics , 2003, DOI: 10.1103/PhysRevC.68.045203
Abstract: Using hadronic Lagrangians that include the interaction of pentaquark $\Theta^+$ baryon with $K$ and $N$, 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 $\mu$b in proton-proton reactions, and 40 nb in photon-proton reactions.
$J/Ψ$ suppression in nuclear collisions at SPS energies
W. Cassing,C. M. Ko
Physics , 1996, DOI: 10.1016/S0370-2693(97)00115-9
Abstract: We have carried out a first calculation of $J/\Psi$ production from nuclear collisions within the covariant transport approach HSD, which has been very successful in describing both hadronic and electromagnetic observables from heavy-ion collisions at intermediate and high energies. The production of $J/\Psi$'s is based on the Lund string fragmentation model, while its interactions with hadrons are included by conventional cascade-type two-body collisions. Adopting 6 mb for the $J/\Psi$-baryon cross sections and 3 mb for the $J/\Psi$-meson cross sections above the $D\bar{D}$ threshold, we find that data on $J/\Psi$ suppression from both proton-nucleus and nucleus-nucleus collisions (including Pb + Pb) can be explained without assuming the formation of a quark-gluon plasma in these collisions. Our microscopic studies thus confirm the suggestion of Gavin et al. that $J/\Psi$ suppression observed in nuclear collisions is largely due to absorption by comovers, i.e., the produced mesons.
Dilepton production from resonance scattering in hot hadronic matter
Chungsik Song,C. M. Ko
Physics , 1995, DOI: 10.1103/PhysRevC.53.2371
Abstract: Dilepton production from resonance scattering in hot hadronic matter is studied. Including the widths of these resonances, which enhance the phase space for dilepton production, we find that the production rate is significantly increased if a resonance appears in the extended phase space. For the reaction $\pi+\rho\to l^++l^-$, the finite $\rho$ meson width extends the invariant mass below the $\omega$-meson mass, so a peak at the $\omega$ meson mass is seen in the dilepton spectrum. Similarly, a $\rho$-meson peak appears in the reaction $\rho+\rho\to l^++l^-$. On the other hand, the effect of particle widths in the reaction $\pi+a_1\to l^++l^-$ is small since the extended phase space does not include any resonance.
Pentaquark baryon production in nuclear reactions
C. M. Ko,W. Liu
Physics , 2004,
Abstract: Using a hadronic model with empirical coupling constants and form factors, we have evaluated the cross sections for the production of exotic pentaquark $\Theta^+$ and/or $\Xi_5^+$ and $\Xi_5^{--}$ in reactions induced by photons, nucleons, pions, and kaons on nucleon targets. We have also predicted the $\Theta^+$ yield in relativistic heavy ion collisions using a kinetic model that takes into account both $\Theta^+$ production from the coalescence of quarks and antiquarks in the quark-gluon plasma and the effects due to subsequent hadronic absorption and regeneration.
Charm meson production from meson-nucleon scattering
W. Liu,C. M. Ko
Physics , 2002, DOI: 10.1016/S0370-2693(02)01661-1
Abstract: Using an effective hadronic Lagrangian with physical hadron masses and coupling constants determined either empirically or from SU(4) flavor symmetry, we study the production cross sections of charm mesons from pion and rho meson interactions with nucleons. With a cutoff parameter of 1 GeV at interaction vertices as usually used in studying the cross sections for $J/\psi$ absorption and charm meson scattering by hadrons, we find that the cross sections for charm meson production have values of a few tenth of mb and are dominated by the s channel nucleon pole diagram. Relevance of these reactions to charm meson production in relativistic heavy ion collisions is discussed.
Pentaquark baryon production from photon-neuteron reactions
W. Liu,C. M. Ko
Physics , 2003, DOI: 10.1016/j.nuclphysa.2004.06.028
Abstract: Extending the hadronic Lagrangians that we recently introduced for studying pentaquark $\Theta^+$ baryon production from meson-proton, proton-proton, and photon-proton reactions near threshold to include the anomalous interaction between $\gamma$ and $K^*K$, we evaluate the cross section for $\Theta^+$ production from photon-neutron reactions, in which the $\Theta^+$ was first detected in the SPring-8 experiment in Japan and the CLAS experiment at Thomas Jefferson National Laboratory. With empirical coupling constants and form factors, and assuming that the decay width of $\Theta^+$ is 20 MeV, the predicted cross section is found to have a peak value of about 280 nb, which is substantially larger than that for $\Theta^+$ production from photon-proton reactions.
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