17,908 research outputs found
The Narrowing of Charge Balance Function and Hadronization Time in Relativistic Heavy Ion Collisions
The widths of charge balance function in high energy hadron-hadron and
relativistic heavy ion collisions are studied using the Monte Carlo generators
PYTHIA and AMPT, respectively. The narrowing of balance function as the
increase of multiplicity is found in both cases. The mean parton-freeze-out
time of a heavy-ion-collision event is used as the characteristic hadronization
time of the event. It turns out that for a fixed multiplicity interval the
width of balance function is consistent with being independent of hadronization
time.Comment: 4 pages, 7 figure
Pure Even Harmonic Generation from Oriented CO in Linearly Polarized Laser Fields
The first high harmonic spectrum, containing only the odd orders, was
observed in experiments 30 years ago (1987). However, a spectrum containing
pure even harmonics has never been observed. We investigate the generation of
pure even harmonics from oriented CO molecules in linearly polarized laser
fields employing the time-dependent density-functional theory. We find that the
even harmonics, with no odd orders, are generated with the polarization
perpendicular to the laser polarization, when the molecular axis of CO is
perpendicular to the laser polarization. Generation of pure even harmonics
reveals a type of dipole acceleration originating from the permanent dipole
moment. This phenomenon exists in all system with permanent dipole moments,
including bulk crystal and polyatomic molecules
Systematic analysis of the incoming quark energy loss in cold nuclear matter
The investigation into the fast parton energy loss in cold nuclear matter is
crucial for a good understanding of the parton propagation in hot-dense medium.
By means of four typical sets of nuclear parton distributions and three
parametrizations of quark energy loss, the parameter values in quark energy
loss expressions are determined from a leading order statistical analysis of
the existing experimental data on nuclear Drell-Yan differential cross section
ratio as a function of the quark momentum fraction. It is found that with
independence on the nuclear modification of parton distributions, the available
experimental data from lower incident beam energy rule out the incident-parton
momentum fraction quark energy loss. Whether the quark energy loss is linear or
quadratic with the path length is not discriminated. The global fit of all
selected data gives the quark energy loss per unit path length {\alpha} =
1.21\pm0.09 GeV/fm by using nuclear parton distribution functions determined
only by means of the world data on nuclear structure function. Our result does
not support the theoretical prediction: the energy loss of an outgoing quark is
three times larger than that of an incoming quark approaching the nuclear
medium. It is desirable that the present work can provide useful reference for
the Fermilab E906/SeaQuest experiment
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