BRAHMS weekly analysis meeting 9 March 2007 =========================================== Submitted by Michael Murray who was a little late. Present: Chellis, Flemming, JH, Ramiro, Hongyan, Kris, Michael, Steve, Selemon Slides are at http://indico.cern.ch/conferenceDisplay.py?confId=13446 09:30 d+Au analysis spectra with centrality dependence Hongyan Yang (UiB) 10:00 CuCu_at_200 GeV analysis and drift velocity calibration SELEMON BEKELE Action Items: 1) The dAu normalization should follow the Group A, B and C approach outlined in http://indico.cern.ch/conferenceDisplay.py?confId=13148 For the run with cross talk in the INEL counters the INEL will be ignored and BB will be used. A correction factor based off INEL/BB, derived from the good runs of group C, will be used. For group B runs the INEL vertex or spectrometer vertex will not be used to keep things simple. She will aslo look into using the ZDC to track the stability of various detectors since this benefited from benign neglect by MM. 2) The histograms different vertex bins current all have the same number of events. This should not be case and she will investigate. 3) Hongyan will refine her PID cuts for kaons and perhaps limit the Pt range where she produces spectra at y=1. 4) Selemon will finish the gtr and dst files by Wednesday of next week. 5) He will settle on a standard momentum cut for the RICH analysis, possible p_threshold * 1.1 as suggested by Flemming and check it for the protons using TOF information on H2. 6) He will use H2 to get low momentum protons. 7) Next week we should have updates by Flemming and hopefully Catalyn. ----------------------------------------------------------------------- dAu spectra and centrality dependence: Hongyan ============================================== Hongyan still has significant problems matching spectra from different settings. She had thought it was tracking efficiency but most of the discussion concerned how she is normalizing the data. Slide 11, shows big difference in efficiency, a factor 1.7 for different runs. JH and Ramero were concerned about consistency between data and Monte Carlo. Count INEL and BB for trigger 3 in different vertex bins. The vertex bin is selected by the INEL counter. The ratio depends on the vertex, it seems to dip in the central region, by a factor of 2. JH thinks this makes partial sense because of the poor resolution of the inelastic counter. Note the histograms for each vertex bin have the same number of events. She is not sure why this is but will get back to us. She looked at runs that are effected by cross talk, runs 8076 to 8306. The INEL/BB ratio seems to rise with run number. JH: ZDC/INEL is quite stable, it seems that BB drops. He suggest that she compare to the ZDC. Steve: Why does "cross talk" problem grow gradually rather than from a sudden turn on. Hongyan remarked that for runs (8076-8306) which have “cross talk” she has no idea how to do the normalization - FV: Remember that INEL counters in group A, B, C from last week. We cannot use the INEL counter for any normalisation or vertex in group B. Thus we should use BB or ZDC and rescale for group A or C. JH: ZDC is most stable. RD: For normalisation stay away from spectrometer info, since this introduces an extra complication. For group C, look for exclusive trigger 5 and exclusive trigger 1 and at the end make the ratios. JH commented that even for group C INEL/BB is not constant with run number. BB is biased toward more central, yes, but this bias is constant accross run. That is precisely why we use a renormalisation factor. (Note BB covers about 50% of our min bias cross section.) For the runs with cross talk she should just ignore INEL vertex information. She has ignored runs with cross talk and find dN/dy~12 but from our paper PRL 94 032301 dN/dEta~9 (They may be consistent after the Jacobian.) For peripheral data she needs more statistics. JH has some concerns about kaon PID. She uses a 2 sigma cut in mass^2 which gets her out to P=2GeV, or Pt=1.6GeV at y=1. RD: comments that the spectra are not changing very much with centrality. Thus we should show ratios of spectra. JH: Would like 0-20 centrality since we have lots of events there. Note this was done by PHENIX and STAR. Steve can look at wheither 0-20 can be done. Selemon: Drift velocity calibrations and CuCu at 200GeV ======================================================= For drift velocity calibration Selemon has trouble with about 7 runs. These problems have been overcome by taking the calibrations from nearby runs. He has produced new ltr files and is working on gtr and dst files. Most of these runs correspond to the higher field settings and will in improvestatistics at high pt Selemon has produces spectra for those runs he currently has. The low pt part of the spectrum for kaons and protons had a problem. This drop seemed to be because we are not applying the same cuts to the acceptance maps and data. So in acceptance maps he zeroed a Pt,y bin if the momentum was below threshold. When he increases this by the spectra become much better behaved. The reason is that it is very difficult to find rings when the momentum is near the threhold. They are small and have only a few photons. Flemming suggested that one only use the RICH for PID when a track has momentum 10% over threshold. He is trying to decide what momentum cut to use. For the protons he can use H2 to check this. In the future he plans to repeat analysis with complete dataset; check the TFW2 calibration and analyze Spectra with MRS2. There was then a general discussion about what we hope to publish? It was decided that we should go for a complete analysis, including low Pt via the time of flight. _______________________________________________ Brahms-l mailing list Brahms-l_at_lists.bnl.gov http://lists.bnl.gov/mailman/listinfo/brahms-l
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