Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session K2: Jet Reconstruction in a High-Multiplicity Environment |
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Sponsoring Units: DNP DPF Chair: Saskia Mioduszewski, Texas A&M University Room: Thurgood Marshall East |
Sunday, February 14, 2010 3:30PM - 4:06PM |
K2.00001: New Jet Methods for High-Multiplicity Environments Invited Speaker: Accurate jet reconstruction in high multiplicity environments is essential to maximize what we learn both in heavy-ion collisions at RHIC and LHC, and in searches of new (beyond standard model) physics in high-luminosity LHC proton-proton (pp) running. State of the art jet-physics methods, developed in parallel for these two environments, have recently been used by the STAR collaboration for the first ever measurements of jets in gold-gold collisions. This talk will outline the theoretical basis of these methods and examine the issues that are relevant in optimizing their performance, highlighting the different considerations that should be taken into account when using them for heavy-ion as opposed to high-luminosity pp collisions. [Preview Abstract] |
Sunday, February 14, 2010 4:06PM - 4:42PM |
K2.00002: Full Jet Reconstruction at RHIC Invited Speaker: Partonic energy loss (jet quenching) within the hot and colored medium created in heavy-ion collisions at Relativistic Heavy-Ion Collider (RHIC) is one of the essential tools to provide quantitative understanding of Quark Gluon Plasma. Measurements of jet quenching via single and di-hadron observables have provided initial estimates of the energy density of this hot QCD medium. However, these hadron-triggered observables suffer from well-known biases since they fold production cross-sections with the energy loss itself, providing limited information on the initial energy of the propagating jet. Fully reconstructed jets - in terms of energy flow - will allow a complete exploration of fragmentation patterns and will not suffer from geometrical biases, providing complementary and perhaps exhaustive understanding of partonic energy loss. In this talk we review the complexity and recent progress in full jet reconstruction techniques in heavy-ion collisions. We recall the pioneering hadron triggered measurements, summarize their impact and put them in contrast to the first measurements of fully reconstructed jets in heavy-ions at RHIC. [Preview Abstract] |
Sunday, February 14, 2010 4:42PM - 5:18PM |
K2.00003: Direct jet reconstruction in $p + p$ and $\mathrm{Cu} + \mathrm{Cu}$ collisions at PHENIX Invited Speaker: Jet reconstruction in heavy ion collisions provides a direct measurement of the medium-induced parton energy loss and the in- medium fragmentation properties, and therefore can significantly enhance our understanding of the energy loss mechanism and medium property. However, the presence of a high multiplicity background prevents the direct application of traditional jet reconstruction techniques, which is e.g.\ known to give rise to a false apparent jet yield. Unlike at the LHC, the small jet cross section relative to the large background fluctuation makes the application to RHIC particularly difficult. We developed an algorithm that reconstructs jets using a Gaussian filter, which is both collinear/infrared safe and cone-like, but enhances the core versus periphery signal and therefore stabilizes the jet definition at the presence of a strongly fluctuating background and/or any detector aperture edges. This is then combined with a fake jet rejection strategy that can suppress the false background jet yield well below the jet production rate at RHIC. We show results from its application to the PHENIX $p + p$ and $ \mathrm{Cu} + \mathrm{Cu}$ data, including jet spectra, $R_ {AA}$, jet-jet correlations, and fragmentation functions. Their theoretical implications will be discussed. [Preview Abstract] |
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