From: Flemming Videbaek (videbaek@rcf.rhic.bnl.gov)
Date: Thu Mar 06 2003 - 19:47:52 EST
Dear Collaborator, By now the Au run has been going on for a long time, but lost of problems on both machine and detector side. Never the less we have collected lots of good data that should serve us well for analysis in the coming year. There has been discussion on extending the d-Au run at the obvious expense of pp running. Our position has been that the highest priority is to complete the d-Au run this year. It obviously costs lots of beam time to start a ‘new’ beam combination. At the exp-RHIC coordination meeting it was decided not to decide until March 19 i.e. 2 (two) days before the nominal end of –Au run if additional running is needed. This places us in the unfortunate dilemma of potentially having problems manning the shifts vs. asking people to stick around when no beam may be here. I would think that the next week run (in term of collected data from all experiments) will clarify this more. Based on the problems with background, as well as discussions with the RHIC machine experts we decided to pursue the option of having the beams at BRAHMS collide with beta(*) of 3 instead of nominal 2. This will reduce the luminosity by 2/3, but also reduce the beam size in the triplets, thus eliminating a potential limiting aperture, that can cause scraping of the beam. This was implemented last night, and seems very good for the experimental conditions at the BRAHMS IR. We have very good background ratios, reduced hits in TPC and so far no detector trips. The uptime of the experiments seems much better, and it seems thus wise to continue with this setting, and probably also use this for future running (Au-Au, pp etc). The overall run-plan is now to focus on high pt measurements. In FS at 4 and 12 deg, and in MRS at 90 now with C4 in place and hopefully with the next day or so connected to the DAQ (delay cables missing). Also with TOF-II (Tfw2) in place we should be able to extend the pt coverage and pion identification at y~0 using these detectors. Best regards Flemming -- Flemming Videbaek Brookhaven National Laboratory Physics Department tlf 631-344-4106 fax 631-344-1334 e-mail: videbaek@bnl.gov
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