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).