4,110 research outputs found
Discussing the possibility of observation of parity violation in heavy ion collisions
It was recently argued that in heavy ion collision the parity could be
broken. This Note addresses the question of possibility of the experimental
detection of the effect. We discuss how parity violating effects would modify
the final particle distributions and how one could construct variables
sensitive to the effect, and which measurement would be the (most) conclusive.
Discussing different observables we also discuss the question if the
``signals'' can be faked by ``conventional'' effects (such as anisotropic flow,
etc.) and make estimates of the signals.Comment: LaTeX, 5 pages; some corrections in chapter III; main results are
unchange
More nonperturbative corrections to the fine and hyperfine splitting in the heavy quarkonium
The leading nonperturbative effects to the fine and hyperfine splitting were
calculated some time ago. Recently, they have been used in order to obtain
realistic numerical results for the lower levels in bottomonium systems. We
point out that a contribution of the same order has been overlooked. We calculate it in this paper.Comment: 9 pages, LaTeX, More self-contained and lengthier version without
changing physical outputs. To be published in Phys. Rev.
Probe for the strong parity violation effects at RHIC with three particle correlations
In non-central relativistic heavy ion collisions, \P-odd domains, which might
be created in the process of the collision, are predicted to lead to charge
separation along the system orbital momentum \cite{Kharzeev:2004ey}. An
observable, \P-even, but directly sensitive to the charge separation effect,
has been proposed in \cite{Voloshin:2004vk} and is based on 3-particle mixed
harmonics azimuthal correlations. We report the STAR measurements using this
observable for Au+Au and Cu+Cu collisions at =200 and 62 GeV.
The results are reported as function of collision centrality, particle
separation in rapidity, and particle transverse momentum. Effects that are not
related to parity violation but might contribute to the signal are discussed.Comment: 4 pages, Quark Matter 2008 Poster proceeding
Methods for the Study of Transverse Momentum Differential Correlations
We introduce and compare three differential correlation functions for the
study of transverse momentum correlation in and collisions. These
consist of {\it inclusive}, {\it event-wise} and a differential version of the
correlation measure introduced by Gavin \cite{Gavin} for
experimental study of the viscosity per unit entropy of the matter produced in
collisions. We study the quantitative difference between the three
observables on the basis of PYTHIA simulations of collisions and
collisions consisting of an arbitrary superposition of collision events
at 200 GeV. We observe that {\it inclusive} and {\it event-wise}
correlation functions are remarkably identical to each other where as the
observable differs from the two. We study the robustness and
efficiency dependencies of these observables based on truncated Taylor
expansions in efficiency in collisions and on the basis of Monte Carlo
simulation using an adhoc detector efficiency parameterization. We find that
all the three observables are essentially independent of detector efficiency.
We additionally study the scaling of the correlation measures and find all the
observables exhibit an approximate dependence of the number of
participants ({\it N}) in collisions. Finally, we study the impact of
flow-like anisotropy on the {\it inclusive} correlation function and find flow
imparts azimuthal modulations similar to those observed with two-particle
densities.Comment: 19 pages, 8 figure
Holographic Hadro-Quarkonium
We consider the recently suggested model for some resonances near the open
charm threshold as bound states of charmonium inside excited light mesons. It
is argued in the soft-wall holographic model of QCD that such states of heavy
quarkonium necessarily exist at sufficiently large spin of the light meson. The
bound state is provided by the dilaton exchange through the 5D bulk. We also
argue that the decay of such bound systems into mesons with open heavy flavors
due to splitting of the heavy quarkonium can be treated as semiclassical
tunneling and is suppressed. This behavior is in agreement with the known
relative suppression of the decay of the discussed charmonium-like resonances
into channels with D mesons.Comment: 11 pages, 1 figur
Reconciling the X(3872) with the near-threshold enhancement in the D^0\bar{D}^{*0} final state
We investigate the enhancement in the D^0\bar{D}^0\pi^0 final state with the
mass M=3875.2\pm 0.7^{+0.3}_{-1.6}\pm 0.8 MeV found recently by the Belle
Collaboration in the B\to K D^0\bar{D}^0\pi^0 decay and test the possibility
that this is yet another manifestation of the well-established resonance
X(3872). We perform a combined Flatte analysis of the data for the
D^0\bar{D}^0\pi^0 mode, and for the \pi^+\pi^- J/\psi mode of the X(3872). Only
if the X(3872) is a virtual state in the D^0\bar{D}^{*0} channel, the data on
the new enhancement comply with those on the X(3872). In our fits, the mass
distribution in the D^0\bar{D}^{*0} mode exhibits a peak at 2-3 MeV above the
D^0\bar{D}^{*0} threshold, with a distinctive non-Breit-Wigner shape.Comment: RevTeX4, 17 pages, some references updated and corrected, version
published in Phys. Rev.
Centrality dependence of directed and elliptic flow at the SPS
New data with a minimum bias trigger for 158 GeV/nucleon Pb + Pb have been analyzed. Directed and elliptic flow as a function of rapidity of the particles and centrality of the collision are presented. The centrality dependence of the ratio of elliptic flow to the initial space elliptic anisotropy is compared to models
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