2,288 research outputs found
Interference in Exclusive Vector Meson Production in Heavy Ion Collisions
Photons emitted from the electromagnetic fields of relativistic heavy ions
can fluctuate into quark anti-quark pairs and scatter from a target nucleus,
emerging as vector mesons. These coherent interactions are identifiable by
final states consisting of the two nuclei and a vector meson with a small
transverse momentum. The emitters and targets can switch roles, and the two
possibilities are indistinguishable, so interference may occur. Vector mesons
are negative parity so the amplitudes have opposite signs. When the meson
transverse wavelength is larger than the impact parameter, the interference is
large and destructive.
The short-lived vector mesons decay before amplitudes from the two sources
can overlap, and so cannot interfere directly. However, the decay products are
emitted in an entangled state, and the interference depends on observing the
complete final state. The non-local wave function is an example of the
Einstein-Podolsky-Rosen paradox.Comment: 13 pages with 3 figures; submitted to Physical Review Letter
Traces of Thermalization from Transverse Momentum Fluctuations in Nuclear Collisions
Scattering of particles produced in Au+Au collisions at RHIC can wrestle the
system into a state near local thermal equilibrium. I illustrate how
measurements of the centrality dependence of the mean transverse momentum and
its fluctuations can exhibit this thermalization.Comment: 4 pages, 2 eps figures, final version to appear in PR
Hot Topics in Ultra-Peripheral Collisions
Ultra-peripheral collisions of relativistic heavy ions involve long-ranged
electromagnetic interactions at impact parameters too large for hadronic
interactions to occur. The nuclear charges are large; with the coherent
enhancement, the cross sections are also large. Many types of photonuclear and
purely electromagnetic interactions are possible. We present here an
introduction to ultra-peripheral collisions, and present four of the most
compelling physics topics. This note developed from a discussion at a workshop
on ``Electromagnetic Probes of Fundamental Physics,'' in Erice, Italy, Oct.
16-21, 2001.Comment: 7 pages, with 3 figures. This developed from a discussion at the
workshop on "Electromagnetic Probes of Fundamental Physics," Oct. 16-21,
Erice, Ital
Coherent photon-photon interactions in very peripheral relativistic heavy ion collisions
Heavy ions at high velocities provide very strong electromagnetic fields for
a very short time. The main characteristics of ultraperipheral relativistic
heavy ion collisions are reviewed, characteristic parameters are identified.
The main interest in ultraperipheral heavy ion collisions at relativistic ion
colliders like the LHC is the interactions of very high energy (equivalent)
photons with the countermoving (equivalent) photons and hadrons (protons/ions).
The physics of these interactions is quite different from and complementary to
the physics of the strong fields achieved with current and future lasers.Comment: 5 pages, 5 figures, invited talk presented at the ELI Workshop and
School on Fundamental Physics with Ultra-high Fields (September 29- October
2, 2008, Frauenwoerth, German
Physics of Ultra-Peripheral Nuclear Collisions
Moving highly-charged ions carry strong electromagnetic fields that act as a
field of photons. In collisions at large impact parameters, hadronic
interactions are not possible, and the ions interact through photon-ion and
photon-photon collisions known as {\it ultra-peripheral collisions} (UPC).
Hadron colliders like the Relativistic Heavy Ion Collider (RHIC), the Tevatron
and the Large Hadron Collider (LHC) produce photonuclear and two-photon
interactions at luminosities and energies beyond that accessible elsewhere; the
LHC will reach a energy ten times that of the Hadron-Electron Ring
Accelerator (HERA). Reactions as diverse as the production of anti-hydrogen,
photoproduction of the , transmutation of lead into bismuth and
excitation of collective nuclear resonances have already been studied. At the
LHC, UPCs can study many types of `new physics.'Comment: 47 pages, to appear in Annual Review of Nuclear and Particle Scienc
Photoproduction at collider energies: from RHIC and HERA to the LHC
We present the mini-proceedings of the workshop on ``Photoproduction at
collider energies: from RHIC and HERA to the LHC'' held at the European Centre
for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Trento)
from January 15 to 19, 2007. The workshop gathered both theorists and
experimentalists to discuss the current status of investigations of high-energy
photon-induced processes at different colliders (HERA, RHIC, and Tevatron) as
well as preparations for extension of these studies at the LHC. The main
physics topics covered were: (i) small- QCD in photoproduction studies with
protons and in electromagnetic (aka. ultraperipheral) nucleus-nucleus
collisions, (ii) hard diffraction physics at hadron colliders, and (iii)
photon-photon collisions at very high energies: electroweak and beyond the
Standard Model processes. These mini-proceedings consist of an introduction and
short summaries of the talks presented at the meeting
Heavy-flavour and quarkonium production in the LHC era: from proton-proton to heavy-ion collisions
This report reviews the study of open heavy-flavour and quarkonium production
in high-energy hadronic collisions, as tools to investigate fundamental aspects
of Quantum Chromodynamics, from the proton and nucleus structure at high energy
to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is
given to the lessons learnt from LHC Run 1 results, which are reviewed in a
global picture with the results from SPS and RHIC at lower energies, as well as
to the questions to be addressed in the future. The report covers heavy flavour
and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus
collisions. This includes discussion of the effects of hot and cold strongly
interacting matter, quarkonium photo-production in nucleus-nucleus collisions
and perspectives on the study of heavy flavour and quarkonium with upgrades of
existing experiments and new experiments. The report results from the activity
of the SaporeGravis network of the I3 Hadron Physics programme of the European
Union 7th Framework Programme
The STAR Time Projection Chamber: A Unique Tool for Studying High Multiplicity Events at RHIC
The STAR Time Projection Chamber (TPC) is used to record collisions at the
Relativistic Heavy Ion Collider (RHIC). The TPC is the central element in a
suite of detectors that surrounds the interaction vertex. The TPC provides
complete coverage around the beam-line, and provides complete tracking for
charged particles within +- 1.8 units of pseudo-rapidity of the center-of-mass
frame. Charged particles with momenta greater than 100 MeV/c are recorded.
Multiplicities in excess of 3,000 tracks per event are routinely reconstructed
in the software. The TPC measures 4 m in diameter by 4.2 m long, making it the
largest TPC in the world.Comment: 28 pages, 11 figure
Centrality dependence of charged hadron production in deuteron+gold and nucleon+gold collisions at sqrt(s_NN)=200 GeV
We present transverse momentum (p_T) spectra of charged hadrons measured in
deuteron-gold and nucleon-gold collisions at \sqrts = 200 GeV for four
centrality classes. Nucleon-gold collisions were selected by tagging events in
which a spectator nucleon was observed in one of two forward rapidity
detectors. The spectra and yields were investigated as a function of the number
of binary nucleon-nucleon collisions, \nu, suffered by deuteron nucleons. A
comparison of charged particle yields to those in p+p collisions show that the
yield per nucleon-nucleon collision saturates with \nu for high momentum
particles. We also present the charged hadron to neutral pion ratios as a
function of p_T.Comment: 330 authors, 15 pages text, 16 figures, 3 tables. Submitted to Phys.
Rev. Lett. v2 has minor changes to reflect revisions during review process.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Azimuthal Angle Correlations for Rapidity Separated Hadron Pairs in d+Au Collisions at sqrt(s_NN) = 200 GeV
We report on two-particle azimuthal angle correlations between charged
hadrons at forward/backward (deuteron/gold going direction) rapidity and
charged hadrons at mid-rapidity in deuteron-gold (d+Au) and proton-proton (p+p)
collisions at sqrt(s_NN) = 200 GeV. Jet structures are observed in the
correlations which we quantify in terms of the conditional yield and angular
width of away side partners. The kinematic region studied here samples partons
in the gold nucleus carrying nucleon momentum fraction x~0.1 to x~0.01. Within
this range, we find no x dependence of the jet structure in d+Au collisions.Comment: 330 authors, 6 pages text, 4 figures, no tables. Submitted to Phys.
Rev. Lett. Plain text data tables for the points plotted in figures for this
and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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