294 research outputs found
The Angular Power Spectrum of Heavy Ion Collisions
Particles produced in heavy ion collisions carry information about
anisotropies present already in the early state of the system and play a
crucial role in understanding the Quark Gluon Plasma and its evolution. We
explore the angular power spectrum of particle multiplicities in such heavy ion
collisions to extract fluctuations in particle multiplicities on the surface a
sphere. Results are presented for Pb-Pb data at , extracted from the ALICE open data portal. We find that odd
modes of the power spectrum display a power-law behavior with corresponding
index , which is found to be close to unity. We also demonstrate that
the angular power spectrum allows us to extract accurately the flow
coefficients of non-central collisions
The Laser Calibration System of the ALICE Time Projection Chamber
A Large Ion Collider Experiment (ALICE) is the only experiment at the Large
Hadron Collider (LHC) dedicated to the study of heavy ion collisions. The Time
Projection Chamber (TPC) is the main tracking detector covering the pseudo
rapidity range . It is designed for a maximum multiplicity \dNdy =
8000. The aim of the laser system is to simulate ionizing tracks at predifined
positions throughout the drift volume in order to monitor the TPC response to a
known source. In particular, the alignment of the read-out chambers will be
performed, and variations of the drift velocity due to drift field
imperfections can be measured and used as calibration data in the physics data
analysis. In this paper we present the design of the pulsed UV laser and
optical system, together with the control and monitoring systems.Comment: 4 pages, 3 figure
Transverse Momentum Spectra in Au+Au and d+Au Collisions at =200 GeV and the Pseudorapidity Dependence of High p Suppression
We present spectra of charged hadrons from Au+Au and d+Au collisions at
GeV measured with the BRAHMS experiment at RHIC. The
spectra for different collision centralities are compared to spectra from collisions at the same energy scaled by the number of binary
collisions. The resulting ratios (nuclear modification factors) for central
Au+Au collisions at and evidence a strong suppression in
the high region (2 GeV/c). In contrast, the d+Au nuclear
modification factor (at ) exhibits an enhancement of the high
yields. These measurements indicate a high energy loss of the high
particles in the medium created in the central Au+Au collisions. The lack of
suppression in d+Au collisions makes it unlikely that initial state effects can
explain the suppression in the central Au+Au collisions.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Rapidity Dependence of Charged Antiparticle-to-Particle Ratios in Au+Au Collisions at GeV
We present ratios of the numbers of charged antiparticles to particles
(pions, kaons and protons) in Au + Au collisions at GeV as
a function of rapidity in the range =0-3. While the particle ratios at
midrapidity are approaching unity, the and ratios
decrease significantly at forward rapidities. An interpretation of the results
within the statistical model indicates a reduction of the baryon chemical
potential from MeV at =3 to MeV at
=0.Comment: 4 pages, 4 figure
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