693 research outputs found
Energy Dependence of Jet Quenching and Life-time of the Dense Matter in High-energy Heavy-ion Collisions
Suppression of high hadron spectra in high-energy heavy-ion collisions
at different energies is studied within a pQCD parton model incorporating
medium induced parton energy loss. The dependence of the nuclear
modification factor is found to depend on both the energy
dependence of the parton energy loss and the power-law behavior of the initial
jet spectra. The high hadron suppression at GeV and its
centrality dependence are studied in detail. The overall values of the
modification factor are found to provide strong constraints on the lifetime of
the dense matter.Comment: 6 pages in RevTex with 3 postscript figure
Evidance for an Oxygen Diffusion Model for the Electric Pulse Induced Resistance Change Effect in Oxides
Electric pulse induced resistance (EPIR) switching hysteresis loops for
Pr0.7Ca0.7MnO3 (PCMO) perovskite oxide films were found to exhibit an
additional sharp "shuttle peak" around the negative pulse maximum for films
deposited in an oxygen deficient ambient. The device resistance hysteresis loop
consists of stable high resistance and low resistance states, and transition
regions between them. The resistance relaxation of the "shuttle peak" and its
temperature behavior as well as the resistance relaxation in the transition
regions were studied, and indicate that the resistance switching relates to
oxygen diffusion with activation energy about 0.4eV. An oxygen diffusion model
with the oxygen ions (vacancies) as the active agent is proposed for the
non-volatile resistance switching effect in PCMO.Comment: 7 pages, 5 figure
High Pt hadron-hadron correlations
We propose the formulation of a dihadron fragmentation function in terms of
parton matrix elements. Under the collinear factorization approximation and
facilitated by the cut-vertex technique, the two hadron inclusive cross section
at leading order (LO) in e+ e- annihilation is shown to factorize into a short
distance parton cross section and the long distance dihadron fragmentation
function. We also derive the DGLAP evolution equation of this function at
leading log. The evolution equation for the non-singlet and singlet quark
fragmentation function and the gluon fragmentation function are solved
numerically with the initial condition taken from event generators.
Modifications to the dihadron fragmentation function from higher twist
corrections in DIS off nuclei are computed. Results are presented for cases of
physical interest.Comment: 7 pages, 8 figures, Latex, Proceedings of Hot Quarks 2004, July
18-24, Taos, New Mexic
A NLO analysis on fragility of dihadron tomography in high energy collisions
The dihadron spectra in high energy collisions are studied within the
NLO pQCD parton model with jet quenching taken into account. The high
dihadron spectra are found to be contributed not only by jet pairs close and
tangential to the surface of the dense matter but also by punching-through jets
survived at the center while the single hadron high spectra are only
dominated by surface emission. Consequently, the suppression factor of such
high- hadron pairs is found to be more sensitive to the initial gluon
density than the single hadron suppression factor.Comment: 4 pages, 4 figures, proceedings for the 19th international Conference
on ultra-relativistic nucleus-nucleus collisions (QM2006), Shanghai, China,
November 14-20, 200
Spectra of Baryons Containing Two Heavy Quarks in Potential Model
In this work, we employ the effective vertices for interaction between
diquarks (scalar or axial-vector) and gluon where the form factors are derived
in terms of the B-S equation, to obtain the potential for baryons including a
light quark and a heavy diquark. The concerned phenomenological parameters are
obtained by fitting data of mesons instead of the heavy quarkonia.
The operator ordering problem in quantum mechanics is discussed. Our numerical
results indicate that the mass splitting between and
is very small and it is consistent with the heavy quark effective
theory (HQET).Comment: 16 page
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