Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. 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

IMRT of Prostate Cancer: A Comparison of Fluence Optimization with Sequential Segmentation and Direct-Step-and-Shoot Optimization

BACKGROUND AND PURPOSE: Intensity-modulated radiation therapy (IMRT) has shown its superiority to three-dimensional conformal radiotherapy in the treatment of prostate cancer. Different optimization algorithms are available: algorithms which first optimize the fluence followed by a sequencing (IM), and algorithms which involve the machine parameters directly in the optimization process (DSS). The aim of this treatment-planning study is to compare both of them regarding dose distribution and treatment time. PATIENTS AND METHODS: Ten consecutive patients with localized prostate cancer were enrolled for the planning study. The planning target volume and the rectum volume, urinary bladder and femoral heads as organs at risk were delineated. Average doses, the target dose homogeneity H, D(5), D(95), monitor units per fraction, and the number of segments were evaluated. RESULTS: While there is only a small difference in the mean doses at rectum and bladder, there is a significant advantage for the target dose homogeneity in the DSS-optimized plans compared to the IM-optimized ones. Differences in the monitor units (nearly 10% less for DSS) and the number of segments are also statistically significant and reduce the treatment time. CONCLUSION: Particularly with regard to the tumor control probability, the better homogeneity of the DSS-optimized plans is more profitable. The shorter treatment time is an improvement regarding intrafractional organ motion. The DSS optimizer results in a higher target dose homogeneity and, simultaneously, in a lower number of monitor units. Therefore, it should be preferred for IMRT of prostate cancer