Dear Collaborator,
At the collaboration meeting we talked on the need to coordinate analysis in the near term to
obtain physics results first for quark matter and secondly for other presentations and publications.
Along those lines we have produced a first list of issues that should be resolved to get results
from the mid-rapidity spectrometer. You should all have seen the very detailed list from Ian on
the forward spectrometer analysis. There are obvious a large degree of overlap in the issues given
below and the efforts should be coordinated. I would like to see a brief report from the Global
analysis outlining the goal and issues.
We will all benefit from your input and help in achieving these goals
in the short timeframe before QM.
MRS analysis goals - plans and issues related to these.
(preliminary.)
Goal 1: particle ratios at y=0.
Process More Data:
o 90 Degree, A, B-pol (2.1KG) |Vz| < 15/20cm, 2 centrality selections?
o Settled for a set of runs that shall be analyzed
Data Selection
o Trigger, Vertex, Minimum Bias, Centrality
o Cut Parameters
o Track Quality, Matching, t0.
o Path Length: . At 90 deg we always thought this would be small. This was checked
looking at MC calculations and found rms(path length) < 1cm. This should be taken into
account but is not significant.
o Track-TOFW matching; looking at the hit isolation, picking best ones etc.
Analysis
o .Background Estimate: Doesn't "cancel out"
- Make PID cuts twodimensionally to minimize effect of back-ground. For pions there
is a significant electron yield at low momenta.
For protons cleaner cuts can be made this way than say in projected M**2 plots.
o .Ratio: pbar/p, pi+/pi- (K-/K+ ?) . pi+/pi- vs pt.
-
Goal 2 Charged spectra; Proton, pion spectra: 0.5 < pt < ~2 - 2.5 GeV/c
o Geometrical Acceptance Map by Geant [Vertex (3-5), Field (2), Charge(2)]. As a first
step we have started generating pure geometric acceptance running GBRAHMS for
single pions, protons. Needs to be generated for different vertices ( 0,+-5,+-10,+-15 )
magnetic fields etc.
o The geometric acceptance is evaluated in bins of .2 in P (or pt) from .2 to 2.2 (20 bins)
and in units of 0.01 from -.1 to .1.
.Correction Factors:
Tracking, PID Efficiencies, Decay, Multiple Scattering Corrections
The charged particle spectra does not require the PID efficiencies,
decay corrections and can be done first.
.Proton pt spectra: 0.4 - ~1.5-2.0 GeV/c, 0.2 GeV/c bin size
This may not be achievable in short term. Statistics is limited, and corrections
important
Analysis issues forth goals
o Estimates of Lambda->p , p-bar in the MRS and FS. Also the higher mass hyperons.
For typical Lambda distributions how many of the p/p-bars from lambda's are with
the normal cuts of( +-4cm +-2cm ) used to identify vertex in z and y .
(2-sigma level)
o Multiplicity selection - can this be done with two cuts. What is the multiplicity
distribution for matched tracks so far.
o Describe data in pt**2 , in mt
o Local Tracking parameters for TPM1, TPM2. Note the goal is to get the data from a
vertex +-20 cm. Not over a very wide range. This might help to settle good cut values.
o
Model comparisons.
One useful reference will be estimates of p,p-bar yields in terms of the cuts in eta and p(pt) the
spectrometers impose, not the dn/dy that we do not measure. The amount of lambda, and other
hyperons are important to estimate the effects of down-feeding.
------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory
tlf: 631-344-4106
fax 631-344-1334
e-mail: videbaek@bnl.gov
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