15012044
Direct Photon-Hadron Correlations Measured with PHENIX
Abstract Direct photon-hadron correlations greatly improve our ability to perform jet tomography in heavy-ion collisions because the momentum of the direct photon can be used to constrain the initial momentum of the opposing jet. By comparing the spectrum of away-side hadrons observed in heavy ion collisions to the spectrum seen in nucleon collisions we can quantify the medium modification to the fragmentation function due to energy loss of the away-side parton. High p T direct photon-hadron correlations have been measured with the PHENIX detector using a statistical subtraction method to remove the photon contribution from meson decays. The increased integrated luminosity in the most recent Au+Au RHIC run at s N N = 200 GeV provides substantially improved statistical precision and enhances the kinematic reach. These measurements are compared to PHENIX p+p results and several theoretical models of energy loss. In addition, we compare direct photon-hadron and π 0 -hadron correlations.
116389613
Direct Photon Tagged Jets in 200 GeV Au+Au Collisions at PHENIX
of the Dissertation Direct Photon Tagged Jets in 200 GeV Au+Au Collisions at PHENIX
121607826
Direct photon-hadron correlations measured with the PHENIX detector
Photon tagged jets are an excellent probe of the hot dense matter created in heavy ion collisions at RHIC. Since photons interact weakly and are not modified by the strongly coupled medium, the measured photon momentum approximately balances that of the away-side parton. Therefore, the modification of the fragmentation function can be obtained by comparing the spectra of the away-side yields in direct photon-hadron correlations in Au+Au collisions to those in p+p. Direct photon-hadron correlations are measured with the PHENIX detector in p+p and Au+Au collisions at sNN=200GeV at RHIC. We employ a statistical subtraction method to remove the contribution of decay photons from the inclusive photon-hadron correlations. For the p+p analysis, we developed event by event techniques to improve the systematic uncertainty in the baseline measurement. Compared to previous measurements, this Au+Au result extends to higher ξ (lower zT) where a medium-induced modification of jet fragmentation is observed.
119253162
Inclusive jet spectra in p–Pb collisions at ALICE
Abstract Jet suppression has been observed in central heavy ion collisions. This suppression is attributed to partonic energy loss in the Quark Gluon Plasma (QGP) formed in such collisions. However, this measurement is influenced by all stages of the collision. It is expected that in p–Pb collisions similar initial conditions occur as in Pb–Pb collisions without creating a QGP, allowing modification to the jet spectra due to cold nuclear matter effects to be quantified. Inclusive jet spectra in p–Pb collisions at s NN = 5.02 TeV measured by ALICE are presented. Jets are reconstructed via the anti- k T algorithm with different resolution parameters by combining charged tracks measured in the ALICE tracking system with the neutral energy deposited in the electromagnetic calorimeter. The jet spectra can be used to determine a nuclear modification factor R pPb while the jet profile in p–Pb is studied by dividing spectra measured with different resolution parameters and comparing to the same ratio measured in pp collisions.
119077476
Design, construction, operation and performance of a Hadron Blind Detector for the PHENIX experiment
Abstract A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure CF 4 . It has a 50 cm long radiator directly coupled in a windowless configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.
23594541
Initial performance of the PHENIX Hadron Blind Detector at RHIC
The PHENIX Hadron Blind Detector (HBD) was successfully operated during the 2009 high energy polarized proton run at RHIC. This was the first data taking run after the detector was rebuilt following its first commissioning run in 2007. The detector was operated for several months under actual beam conditions and showed greatly improved performance over the commissioning run. Results are given on the operation of the detector, determination and calibration of the gain using scintillation light produced by charged particles in CF4, stability of the CsI photocathodes, the ability to identify single and double electrons using the signal from Cherenkov light, and the level of sensitivity of the detector to charged hadrons. A description is also given on the methods used to reconstruct the detector that led to its improved performance.
54937918
Evidence for a Color Dependence in the Size Distribution of Main-Belt Asteroids
We present the results of a project to detect small (~1 km) main-belt asteroids with the 3.6 m Canada-France-Hawaii Telescope. We observed in two filters (MegaPrime g' and r') in order to compare the results in each band. Owing to the observational cadence we did not observe the same asteroids through each filter and thus do not have true color information. However, strong differences in the size distributions as seen in the two filters point to a color dependence at these sizes, perhaps to be expected in this regime, in which asteroid cohesiveness begins to be dominated by physical strength and composition rather than by gravity. The best-fit slopes of the cumulative size distributions (CSDs) in both filters tend toward lower values for smaller asteroids, consistent with the results of previous studies. In addition to this trend, the size distributions seen in the two filters are distinctly different, with steeper slopes in r' than in g'. Breaking our sample up according to semimajor axis, the difference between the filters in the inner belt is found to be somewhat less pronounced than in the middle and outer belt, but the CSD of those asteroids seen in the r' filter is consistently and significantly steeper than in g' throughout. The CSD slopes also show variations with semimajor axis within a given filter, particularly in r'. We conclude that the size distribution of main-belt asteroids is likely to be color-dependent at kilometer sizes and that this dependence may vary across the belt.