From: J.H. Lee (jhlee@sgs1.hirg.bnl.gov)
Date: Fri Jun 27 2003 - 14:18:06 EDT
Dear Claus, Let me ask a couple of questions on plots in the latest draft. 1. The yield at eta~2.2 has been significantly increased (by a factor of "~2") comparing figures shown at colloquium and the one in the latest draft. Is it due to a simple mistake in the previous plot making or "new and improved" analysis? 2. I don't understand why R_AA(eta~2) is similar as before. If you look at HIro's figures (http://pii3.brahms.bnl.gov/~hito/pp/UA1_Correction.html) at pt = 3-4 GeV/c, there is a factor of ~2-2.5 difference in the correction factor between h-(2<|eta|<2.2)/h+-/2 (|eta|<2.5) and h+-(2<|eta|<2.2)/h+- (|eta|<2.5). This should change the R factor significantly at eta~2.2. Why no change? Are we looking at obsolete figures? 3. You mentioned about the systematic errors in the previous message: "...................A lot of the systematic errors cancel out when you make the central to "semi-peripheral" (Rcp) ratios, but not the errors introduced in the Nbin calculation! Actually this is to 1st approximation the only systematic error in this ratio. Errors introduced by correcting for acceptance will cancel out, errors in efficiencies will cancel out (the dependence on centrality is very little, especially for high field runs) and of course the reference normalization will cancel out." I don't think it's quite true. As Dana pointed out, there is kinky feature in the 40-60% ratios in Fig. 2, which is much bigger than statistical uncertainties. This might be due to some unknown centrality dependences (background?) which don't cancel out. That means there is some point-by-point uncertainties don't cancel out. There is another overall uncertainty from different systematics in normalizing centrality on top of uncertainties from using Nbin calculated from models. They might be some overlaps between two of them, but certainly they are different kind of uncertainties. JH ----- Original Message ----- From: Jens Jørgen Gaardhøje To: brahms-l@bnl.gov Cc: gardhoje@nbi.dk ; Claus O. E. Jorgensen ; Ian Bearden Sent: Thursday, June 26, 2003 5:57 PM Subject: high pt paper Dear collaborators, Enclosed please find an updated version of the high pt paper. Quite a number of comments have found their way as you will see. No work on refs. is included. This is a job for the weekend. You will also see that the present philosophy is to try to eliminate the dependency on syst errors as much as possible. These afflict primarily the y=2 setting, but of course also the y=0 settings to a lesser degree. The former setting suffers from a high degree of model dependence of the p+p ref. However, we fell that we can arrive at the central arguments by discussing the ratios of spectra for central and peripheral collisions, and the ratios of such ratios at the two rapidities, thus making us independent of the p+p ref. spectra and even of N_bin. This, we feel give us a good confidence in stating that we see significant suppression also at Y=2. This is a statement that only BRAHMS can make and which will have to be taken into account in the model picture of RHIC physics. Thus, the R_AA at Y=2 (uppermost 2 right panels in fig. 2) suffer from large syst. uncertainties, but we think that the main arguments, notably those implied by fig. 3 and 4 , are nevertheless quite 'clean'. In particular we see few effects that can dramatically change the bottom panels of fig 2 and fig.3. We also suggest that it is of very high importance for the BRAHMS collaboration to make public our results on high pt suppression very rapidly. We suggest that a target date for a submission to PRL should be the press conference +14 days, i.e next tuesday. The implicit aim here, is that a BRAHMS paper can appear in the same issue as the papers submitted by the other 3 experiments. This is a very tight deadline and will require continued (very) hard work from the main players and several others. If this is to be possible we request your kind input to the discussion before the weekend, with both positive and negative criticism, so that we may gauge the sentiment of the collaboration. The suggested plan is therefore the following: - continued analysis aiming at weeding out inconsistencies in the basic data and shrinking systematic uncertainties (ongoing) - improvements of the text and main arguments, including serious work on finding the appropriate references.(weekend) - improvements of the presentation quality of the figures.(monday) with inclusions of bands of syst, errors etc. - final revision and submission by tuesday. Naturally we will need to evaluate the entire affair Monday again before proceeding to the last item. With tired cheers and thanks to those who have already contributed with comments and input Claus, Ian, Peter and JJ. ____________________________________________________________ Jens Jørgen Gaardhøje, Assoc. Prof., Dr. Sc. Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark. Tlf: (+45) 35 32 53 09, secr. (+45) 35 32 52 09, Fax: (+45) 35 32 50 16. UNESCO Natl. Comm., secr. (+45) 33 92 52 16. Email: gardhoje@nbi.dk. ____________________________________________________________
This archive was generated by hypermail 2.1.5 : Fri Jun 27 2003 - 14:22:09 EDT