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Slow particles analysis. Acceptance/efficiency factors Embedding tracks Raw 1/N ev 1/ p T d 2 N/d dp T at mid-rapidity PR01, PR00 data Hijing data reconstruction STAR spectra todo list. F. X[cm]. E. D. C. B. A. Z[cm]. Algorithm. - PowerPoint PPT Presentation
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Slow particles analysis
Acceptance/efficiency factorsEmbedding tracks
Raw 1/Nev 1/pT d2N/ddpT at mid-rapidityPR01, PR00 dataHijing data reconstruction STAR spectra
todo list
Algorithm
Z[cm]
X[c
m]
AB
CD
EF
Algorithm is tuned for finding particles which range out in plane E
To find efficiency and acceptance embedding single tracks within full MC events is done within “window”:
x x p
window size depends on Zvertcentrality bin: 15%Z vertex: -7cm to 15cmeach arm done separately
adding tracks until reconstruction is successful (with 4 or 5 hits / track)
Angular Acceptance
Zvert Zvert
primary cos, uniformly distributed between bands.
Momenta Ranges
Zvert
momentum
p,p
K+,K-
+,-
momenta uniformly distributed within bands
Efficiency/acceptance examples
1/eff within embedding window for pions within full 4/angular window size
SpecN
o SpecP
ZvertZvert
Experimental check for efficiency factors
Zvert
SpecN
o SpecP
Zvert distributions of reconstructed pions scaled by arm-efficiency
Number of reconstructed tracks in PR01 and PR00 data
Selected 15% most central with Zvert from -7cm to 15cm
PR01: 216000 ev.
PR00: 25800 ev.
PR00 PR01
Nrec 565 4849
NKrec 67 520
Nprec 24 157
dE/dx for reconstructed pions: PR01 vs MC
after energy recalibration by 1.13
Raw 1/Nev 1/pT d2N/ddpT at mid-rapidity
PT
[MeV/C]PR00
In brackets number of tracks
PR01
52 7700(150) 8100(1249)
K 129 180( 16) 168( 144)
p 202 14( 5) 22( 60)
||<0.25, Zvert from 5cm to 15cm,
Nev=11700/ 97900 for PR00/PR01
Enough data only for pion PR01 sample at midrapidity
Reconstruction of PR01 MC data
reconstructed MC pions (473)
slow pions62%
contamin.12%
random26%
primary54%
decay/inter.8%
K5%
p7%
stopping28%
non-stop. 26%
15% centrality, Zvert: -7cm-15cmNev=18600primary/all = 0.54
slow pion = pion having hits in A-D or A-E
Reconstruction of PR00 MC data
reconstructed MC pions (237)
slow pions70%
contamin.5%
random25%
primary59%
decay/inter.11%
K2%
p3%
stopping28%
non-stop. 31%
Nev=12400primary/all = 0.59
STAR 1/Nev 1/pT d2N/ddpT for h-+h+
130GeV
centrality 5%
||<0.1
A(1+pT/p0)n
crude estimate of PHOBOS -point @ 52MeV:
7700 * 0.59(Hijing bkg) * 1.17(15%->6%) = 5300
pT[GeV/c]
todo
• Calculation of background factors - embedding of , K, p in proportions to increase statistics of bkg tracks.
• Recalculate efficiency and bkg factors with embedding into experimental data.
• Reconstruction of more PR01 data (crucial for K , p and negative ptls).
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