6 research outputs found
Novel Bose-Einstein Interference in the Passage of a Fast Particle in a Dense Medium
When an energetic particle collides coherently with many medium particles at
high energies, the Bose-Einstein symmetry with respect to the interchange of
the exchanged virtual bosons leads to a destructive interference of the Feynman
amplitudes in most regions of the phase space but a constructive interference
in some other regions of the phase space. As a consequence, the recoiling
medium particles have a tendency to come out collectively along the direction
of the incident fast particle, each carrying a substantial fraction of the
incident longitudinal momentum. Such an interference appearing as collective
recoils of scatterers along the incident particle direction may have been
observed in angular correlations of hadrons associated with a high-
trigger in high-energy AuAu collisions at RHIC.Comment: 10 pages, 2 figures, invited talk presented at the 35th Symposium on
Nuclear Physics, Cocoyoc, Mexico, January 3, 2012, to be published in IOP
Conference Serie
Exploring Early Parton Momentum Distribution with the Ridge from the Near-Side Jet
In a central nucleus-nucleus collision at high-energies, medium partons
kicked by a near-side jet acquire a momentum along the jet direction and
subsequently materialize as the observed ridge particles. They carry direct
information on the early parton momentum distribution which can be extracted by
using the ridge data for central AuAu collisions at \sqrt{s_{NN}}=200 GeV. The
extracted parton momentum distribution has a thermal-like transverse momentum
distribution but a non-Gaussian, relatively flat rapidity distribution at
mid-rapidity with sharp kinematic boundaries at large rapidities that depend on
the transverse momentum.Comment: In Proceedings of 20th International Conference on Ultra-Relativistic
Nucleus Nucleus Collisions, Jaipur, India, Feb. 4-10, 200
System size, energy, centrality and pseudorapidity dependence of charged-particle density in Au+Au and Cu+Cu collisions at RHIC
Charged particle pseudorapidity distributions are presented from the PHOBOS
experiment at RHIC, measured in Au+Au and Cu+Cu collisions at sqrt{s_NN}=19.6,
22.4, 62.4, 130 and 200 GeV, as a function of collision centrality. The
presentation includes the recently analyzed Cu+Cu data at 22.4 GeV. The
measurements were made by the same detector setup over a broad range in
pseudorapidity, |eta|<5.4, allowing for a reliable systematic study of particle
production as a function of energy, centrality and system size. Comparing Cu+Cu
and Au+Au results, we find that the total number of produced charged particles
and the overall shape (height and width) of the pseudorapidity distributions
are determined by the number of nucleon participants, N_part. Detailed
comparisons reveal that the matching of the shape of the Cu+Cu and Au+Au
pseudorapidity distributions over the full range of eta is better for the same
N_part/2A value than for the same N_part value, where A denotes the mass
number. In other words, it is the geometry of the nuclear overlap zone, rather
than just the number of nucleon participants that drives the detailed shape of
the pseudorapidity distribution and its centrality dependence.Comment: 5 pages, 4 figures. Presented at the 20th International Conference on
Nucleus-Nucleus Collisions (Quark Matter 2008), Jaipur, Rajasthan, India,
4-10 February 200
Scaling properties in bulk and p-dependent particle production near midrapidity in relativistic heavy ion collisions
The centrality dependence of the midrapidity charged-particle multiplicity
density (1) is presented for Au+Au and Cu+Cu collisions at RHIC over
a broad range of collision energies. The multiplicity measured in the Cu+Cu
system is found to be similar to that measured in the Au+Au system, for an
equivalent N, with the observed factorization in energy and
centrality still persistent in the smaller Cu+Cu system. The extent of the
similarities observed for bulk particle production is tested by a comparative
analysis of the inclusive transverse momentum distributions for Au+Au and Cu+Cu
collisions near midrapidity. It is found that, within the uncertainties of the
data, the ratio of yields between the various energies for both Au+Au and Cu+Cu
systems are similar and constant with centrality, both in the bulk yields as
well as a function of p, up to at least 4 GeV/. The effects of
multiple nucleon collisions that strongly increase with centrality and energy
appear to only play a minor role in bulk and intermediate transverse momentum
particle production.Comment: Submitted for publication in Phys. Rev. C, 5 pages, 3 figure