Fits of the mt distributions at midrapidity of the real data and UrQMD events:
1. UrQMD source (*.evt file)
2. UrQMD source (*.evt file) passed through the acceptance matrix
3. UrQMD LVL1 events (from GeantKine from UrQMD dst files)
4. UrQMD LVL1 events passed through the acceptance matrix (from GeantKine from UrQMD dst files)
5. "sim" data = UrQMD data fully analyzed (tracking+PID+efficiency corrections)
6. real data
Fitted function is
1/m
2t*dN/dm
t = C
1*exp(-m
t/T
1) + C
2*exp(-m
t/T
2)
Range of fit is 50 ≤ m
t-m
pi < 550. This gives the same results for UrQMD data without and with the acceptance filter for both pi+ and pi-. For pi- we can decrease the lower range to 25, and the fit result do not change significantly for the real and "sim" data.
Only statistical errors are taken into account. Please note the chi
2 value of fits.
T1/T2 shows ratio of areas of one slope components of te distribution.
|
chi2/NDF |
T1 |
T2 |
T1/T2 |
pi+ urqmd primary |
79/16 |
30.6+-0.4 |
87.7+-0.1 |
0.15 |
pi- urqmd primary |
153/16 |
31.3+-0.3 |
87.7+-0.1 |
0.16 |
|
pi+ urqmd LVL1 |
30/16 |
41.3+-0.6 |
90.3+-0.2 |
0.24 |
pi- urqmd LVL1 |
61/16 |
40.8+-0.5 |
89.9+-0.2 |
0.24 |
|
pi+ urqmd sim |
352/16 |
45.1+-1.0 |
91.3+-0.4 |
0.25 |
pi- urqmd sim |
145/16 |
40.0+-0.9 |
90.7+-0.3 |
0.23 |
|
pi+ exp |
373/16 |
53.7+-0.5 |
93.6+-0.6 |
1.01 |
pi- exp |
538/16 |
48.6+-0.3 |
91.7+-0.5 |
1.20 |
now fit result of the real data if we assume the points errors 2.5% (from differences between distribution from different sectors)
pi+ exp |
17.0/16 |
47.7+-3.3 |
88.7+-1.7 |
0.60 |
pi- exp |
11.3/16 |
50.3+-2.0 |
94.0+-2.5 |
1.42 |
Some conclusions:
1)
UrQMD primary and UrQMD LVL1 differ - we get higher slopes for LVL1 -
looks that selection on sentrality makes pi mesons "harder".
2)
UrQMD LVL1 and "sim" agree - it shows that all analysis does not spoil the
urqmd original distributions.
Here are the figures with fits (results shown also in previous table):
- UrQMD primary (from *.evt files):
- UrQMD LVL1 (from urqmd dst's GeantKine):
GeantKine)" width="966" height="474" />
- "sim" - full analysis of UrQMD dsts:
- real data - statistical errors:
- real data - errors 2.5% (good chi2):
--
PavelTlusty - 31 Mar 2008