[Brahms-l] Brahms Minutes 20 April 2007

          Minutes of BRAHMS analysis meeting 20 April 2007
          =================================================
                                                Submitted by Michael  
Murray


Present: Chellis, Flemming, Steve, Michael, Hongyan, Selemon, Dipali

Agenda: http://indico.cern.ch/conferenceDisplay.py?confId=15145

09:30 	Flow Analysis of AuAu (30') ( Slides   )	Steve Sanders
10:00 	update on pp spectrum paper (15') ( Slides   )	F.Videbaek
10:59 	Final slides shown on April 18th at DIS07-Munich. 	JH Lee

Action Items:
=============
Steve: Will redo analysis with optimized resolutions to see if he can  
get more physics out.
Flemming: Is preparing a paper on pp at 62 and 200GeV.
Kris will put his data on the same plot as Flemming by next week.
Later  This comparison should include Hongyan's results.


Steve: Reaction Plane Resolution
================================
For QM06 we used Eric's package. He only used reaction planes and  
reaction plane resolutions that can be confirmed by a self-consistent  
BRAHMS analysis using three separate detector rings. However we may  
be able to improve on this for run 4 since we have
BBL (One ring of large detectors)
Si1
FlSi2
FlSi3
Tile
Eric required 3 detectors with independent eta coverage for each  
vertex range. Eric worked this out for each setting of the MRS.
Resolution is <cos[2(Phi - Phi_real)]>. Note we want this factor to  
be big. For the left side we are usually using the tile.

Try to improve using flow simulation package
Uniform (MB) centrality distribution.
dN/dη (η,centrality) based on BRAHMS 200 GeV AuAu results
v1(η,centrality) and v2(η,centrality) based on PHOBOS results
Particle spectra based on BRAHMS results, where available.  Otherwise  
HIJING is used to determine particle ratios. Everything is thrown  
into GEANT. Note he also includes the pt dependence of V2.

With this method he could improve the reaction plane resolution by  
20-30%  but he does not have a self consistent way to check. It would  
have to be an iterative analysis. Since we do no the number of  
particles hitting each detector we can remove effects of auto  
correlations by a subtraction procedure.

Chellis could you try the cumalative method. Hiro tried this but we  
should ask him about this. Flemming this would only improve the MRS  
stuff, which should not be driving the physics analysis.

Flemming pp at 62 GeV.
======================
He has kaons at y=3. (He thinks 4 & 6 degrees are not worth working on)

Note pbar/p < 0.5% so we cannot say much about the shape of the  
spectrum since pion leakage through RICH dominates.
Proton spectra are of course much easier. We a nice dN/dy results.
If we assume dN/dx = Constant, then dN/dy = 0.7 * exp (y-ybeam), this  
works pretty well.
Chellis this assumes something about <pt>.
Boltzman slopes drop from 180MeV at y=0 to 120MeV at y=3.

Our proton spectra aggree well with ISR data at the appropriate y-ybeam.

Comments on Pythia
Default pythia get dn/dy for pions below pt of one roughly right,  
both at y~0 and y~2.7, 3.3. At higher pt the yield grows above data.
The protons are completely off at higher pt (and larg y) . This is  
consistent with Ramiro’s observation of Hijing comp with protons at  
pp=200 geV. (same underlying Jetset and Lund model, though much  
earlier version.)
Note Pythia tuned to SPS and FNAL collidors.

He has started writing a paper. It would be nice to combine the 62  
and 200 GeV data for limiting fragmentation. He also wants some  
comparisons to generators, and if possible something outside the  
HiGing family.

Steve: Who is doing the different pp analysis
JH Spin, Natalie in Krakow 62GeV, Kris 200 GeV, Hongany is looking at  
200GeV, Alte is looking at 62GeV.

Kris has spectra from 90 and 45 degrees, which look reasonable except  
that they turn down at the bottom of the pt range.

Action item: Kris will put his data on the same plot as Flemming in 2  
or 3 weeks.

For Selemon some of the intermediate settings are not done yet.
Selemon: Do we have a pp reference. Note Flemming does not agree with  
STAR or PHENIX. There are significant differences between experiments  
because of the fraction of cross section that they see. There do seem  
to be some 10-15% differences between experiments.

JH Lee: His DIS07 talk is listed for reference.
===============================================

Next week Kris, pp at 200GeV.




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