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Search Results: 1 - 10 of 618139 matches for " C. M. Liu "
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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.
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.
Photoproduction of pentaquark cascades from nucleons
W. Liu,C. M. Ko
Physics , 2003, DOI: 10.1103/PhysRevC.69.045204
Abstract: The cross sections for production of pentaquark $\Xi^+_5$ from the reaction $\gamma p\to K^0K^0\Xi^+_5$ and $\Xi^{--}_5$ from the reaction $\gamma n\to K^+K^+\Xi^{--}_5$ are evaluated in a hadronic model that includes their couplings to both $\Sigma\bar K$ and $\Sigma\bar K^*$. With these coupling constants determined from the empirical $\pi NN(1710)$ and $\rho NN(1710)$ coupling constants by assuming that $\Xi^+_5$, $\Xi^{--}_5$, and N(1710) belong to the same antidecuplet of spin 1/2 and positive parity, and using form factors at strong interaction vertices similar to those for pentaquark $\Theta^+$ production in photonucleon reactions, we obtain a cross section of about 0.03-0.6 nb for the reaction $\gamma p\to K^0K^0\Xi^+_5$ and about 0.1-0.6 nb for the reaction $\gamma n\to K^+K^+\Xi^{--}_5$ at photon energy $E_\gamma=4.5$ GeV, depending on the value of the coupling constant $g_{K^*\Sigma\Xi_5}$.
Even and odd q-deformed charge coherent states and their nonclassical properties
X. -M. Liu,C. Quesne
Physics , 2003, DOI: 10.1016/j.physleta.2003.08.048
Abstract: Even and odd q-deformed charge coherent states are constructed, their (over)completeness proved and their generation explored. A $D$-algebra realization of the SU$_q$(1,1) generators is given in terms of them. They are shown to exhibit SU$_q$(1,1) squeezing and two-mode $q$-antibunching, but neither one-mode, nor two-mode $q$-squeezing.
Effect of three-body elastic scattering on heavy quark momentum degradation in the quark-gluon plasma
W. Liu,C. M. Ko
Physics , 2006,
Abstract: Heavy quark drag coefficients in the quark-gluon plasma are evaluated in the perturbative QCD. It is found that for charm quarks the contribution from three-body elastic scattering is comparable to those from two-body elastic and radiative scatterings while for bottom quarks it becomes dominant. Using a schematic expanding fireball model, effects of both two-body and three-body scatterings on the transverse momentum spectra of heavy quarks produced in Au+Au collisions at center of mass energy $\sqrt{s_{NN}}=200$ GeV are studied. Results on electrons from resulting heavy meson decays are compared with available experimental data.
Magnetic Neutron Scattering in Solid Oxygen and its Applications to Ultracold Neutron Production
C. -Y. Liu,C. M. Lavelle,C. M. Brown
Physics , 2011,
Abstract: Using neutron scattering, we investigate the static and dynamic structure functions $S(Q,\omega)$ of 3 distinct solid phases (using powder average techniques), and characterize the corresponding modes of energy excitation, focusing primarily on the dynamics of spin interaction. With the $S(Q,\omega)$ maps, we extract the temperature dependent production rate and upscattering cross section, that are relevant for understanding experimental data on ultracold neutron production in solid oxygen at the saturated vapor pressure.
Superconductivity Modulated by Binary Doping in Nd1-xBaxFeAsO1-2xF2x  [PDF]
C. Q. Qu, Z. Y Liu, Y. M Lu, C. Z Chen, C. B Cai, A. H Fang, F. Q Huang, M. F Wang, X. M Xie
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.26056
Abstract: Binary doping effect is studied for the Fe-based superconductors of Nd1-xBaxFeAsO1-2xF2x(x = 0.02, 0.05, 0.1, 0.15, 0.2). The X-ray diffractions show that the c-axis lattice constant decreases monotonously with the doping content, in contrast to the little change in the a-axis. Temperature dependences of electric resistivity and magnetic susceptibility reveal that the superconductivity for the studied system emerges at x = 0.1, and enhances together with Hc2(0) as the doping content x increases further. In case of x = 0.2, the superconducting critical temperature reaches as high as 50 K, which is the first demonstration of superconductivity with a high fluorine-doping induced by both electron and hole doping in this family. Negative Hall coefficient (RH) indicates that electron-type carriers are dominated in the present samples. The complicated temperature dependence of RH, is believed to arise from a multiband effect together with a complicated scattering, especially at the tem-perature near the TC.
Seasonal changes in gaseous elemental mercury in relation to monsoon cycling over the northern South China Sea
C. M. Tseng, C. S. Liu,C. Lamborg
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: The distribution of gaseous elemental mercury (GEM) was determined in the surface atmosphere of the northern South China Sea (SCS) during 12 SEATS cruises between May 2003 and December 2005. The sampling and analysis of GEM were performed on board ship by using an on-line mercury analyzer (GEMA). Distinct annual patterns were observed for the GEM with a winter maximum of 5.7 ± 0.2 ng m 3 (n = 3) and minimum in summer (2.8 ± 0.2; n = 3), with concentrations elevated 2–3 times global background values. Source tracking through backward air trajectory analysis demonstrated that during the northeast monsoon (winter), air masses came from Eurasia, bringing continental- and industrial-derived GEM to the SCS. In contrast, during summer southwest monsoon and inter-monsoon, air masses were from the Indochina Peninsula and Indian Ocean and west Pacific Ocean. This demonstrates the impact that long-range transport, as controlled by seasonal monsoons, has on the Hg atmospheric distribution and cycling in the SCS.
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