Neutral Pion Distributions in PHENIX at RHIC

Transverse momentum spectra for identified $\pi^0$'s in the range 1 GeV/c $< p_T <$ 4 GeV/c have been measured by the PHENIX experiment in Au-Au collisions at $\sqrt{s}=130$ GeV. The spectra from peripheral nuclear collisions are consistent with the simple expectation of scaling the spectra from p+p collisions by the average number of nucleon-nucleon binary collisions. The spectra from central collisions and the ratio of central/peripheral spectra are significantly suppressed when compared to point-like scaling.Comment: 6 pages, 3 figure

Two Particle Azimuthal Correlation Measurements in PHENIX

Two particle azimuthal correlation functions are presented for charged hadrons produced in Au-Au collisions at RHIC sqrt(s_NN)=200 GeV.The correlation functions indicate sizeable asymmetries and anisotropies. The trend of the asymmetries is compatible with the presence of emission patterns associated with mini-jets. The magnitude and the trend of the differential anisotropies v_2(p_T) and v_2(N_Part), provide important model constraints.Comment: 4 pages 3 fig

Results on Photon Production in Au+Au Collisions at RHIC

The status of the search for direct photons in Au+Au collisions at sqrt{s_NN} = 130 GeV and sqrt{s_NN} = 200 GeV with the PHENIX experiment is presented. Within errors, no excess of direct photons was found in a first analysis pass done on a limited data set. Significantly reduced systematic and statistical uncertainties are expected in future analyses.Comment: 4 pages, 3 figures. Talk presented at the Quark Matter 2002 conference, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

Point-to-point readout for the ALICE EMCal detector

AbstractIt is anticipated that the LHC will deliver Pb+Pb collisions at a minimum bias interaction rate of about 50kHz after the second long shutdown of the LHC in 2018. This will be roughly two orders of magnitude greater than the current data recording rate capability of the ALICE experiment. Therefore a major upgrade of the ALICE detector is planned for the next shutdown to enable ALICE to record data at the full Pb+Pb minimum bias interaction rate delivered by the LHC. A new point-to-point readout system for the electromagnetic calorimeter (EMCal) of ALICE has been developed, to replace the legacy readout bus, that essentially accomplishes this goal, and is being installed during the current LHC shutdown (2013–2014). The new readout uses the existing EMCal front end electronics yet provides more than an order of magnitude decrease in the readout time, to about 21μs, with modest cost and effort

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-$x$ 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

Search for direct photons in p+Pb and p+C collisions at sqrt(sNN) = 17.4 GeV

Upper limits on direct photon production were determined as a function of the transverse momentum for 0.7 < pT <= 3.2 GeV/c with the WA98 experiment in p+C and p+Pb collisions at sqrt(sNN) = 17.4 GeV. The results are compared to direct photon measurements in Pb+Pb collisions at sqrt(sNN) = 17.3 GeV by WA98. Implications for a possible thermal direct photon contribution are discussed.Comment: 4 pages, 3 figures, to appear in the proceedings of the Quark Matter 2008 conference, Jaipur, India, 4-10 Feb 200

Event Reconstruction in the PHENIX Central Arm Spectrometers

The central arm spectrometers for the PHENIX experiment at the Relativistic Heavy Ion Collider have been designed for the optimization of particle identification in relativistic heavy ion collisions. The spectrometers present a challenging environment for event reconstruction due to a very high track multiplicity in a complicated, focusing, magnetic field. In order to meet this challenge, nine distinct detector types are integrated for charged particle tracking, momentum reconstruction, and particle identification. The techniques which have been developed for the task of event reconstruction are described.Comment: Accepted for publication in Nucl. Instrum. A. 34 pages, 23 figure

Azimuthal Anisotropy of Photon and Charged Particle Emission in Pb+Pb Collisions at 158 A GeV/c

The azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in Pb + Pb collisions at 158 A GeV/c in the WA98 experiment at the CERN SPS. The anisotropy of the azimuthal distributions is characterized using a Fourier analysis. For both the photon and charged particle distributions the first two Fourier coefficients are observed to decrease with increasing centrality. The observed anisotropies of the photon distributions compare well with the expectations from the charged particle measurements for all centralities.Comment: 8 pages and 6 figures. The manuscript has undergone a major revision. The unwanted correlations were enhanced in the random subdivision method used in the earlier version. The present version uses the more established method of division into subevents separated in rapidity to minimise short range correlations. The observed results for charged particles are in agreement with results from the other experiments. The observed anisotropy in photons is explained using flow results of pions and the correlations arising due to the decay of the neutral pion

Measurement of the mid-rapidity transverse energy distribution from sNN=130\sqrt{s_{NN}}=130 GeV Au+Au collisions at RHIC

The first measurement of energy produced transverse to the beam direction at RHIC is presented. The mid-rapidity transverse energy density per participating nucleon rises steadily with the number of participants, closely paralleling the rise in charged-particle density, such that E_T / N_ch remains relatively constant as a function of centrality. The energy density calculated via Bjorken's prescription for the 2% most central Au+Au collisions at sqrt(s_NN)=130 GeV is at least epsilon_Bj = 4.6 GeV/fm^3 which is a factor of 1.6 larger than found at sqrt(s_NN)=17.2 GeV (Pb+Pb at CERN).Comment: 307 authors, 6 pages, 4 figures, 1 table, submitted to PRL 4/18/2001; revised version submitted to PRL 5/24/200

Event-by-event fluctuations in Mean pTp_T and Mean eTe_T in sqrt(s_NN) = 130 GeV Au+Au Collisions

Distributions of event-by-event fluctuations of the mean transverse momentum and mean transverse energy near mid-rapidity have been measured in Au+Au collisions at sqrt(s_NN) = 130 GeV at RHIC. By comparing the distributions to what is expected for statistically independent particle emission, the magnitude of non-statistical fluctuations in mean transverse momentum is determined to be consistent with zero. Also, no significant non-random fluctuations in mean transverse energy are observed. By constructing a fluctuation model with two event classes that preserve the mean and variance of the semi-inclusive p_T or e_T spectra, we exclude a region of fluctuations in sqrt(s_NN) = 130 GeV Au+Au collisions.Comment: 10 pages, RevTeX 3, 7 figures, 4 tables, 307 authors, submitted to Phys. Rev. C on 22 March 2002. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (will be made) publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm