Muons from /K
CSC samples vs generator
predictions: preliminary
comparisons
CSC Samples
Single 
• pT vs h distribution extracted
from min bias and J1-J8 di-jets
PYTHIA generated sample
–
–
–
–
csc11.005001.pythia_minbias
csc11.005010.J1_pythia_jetjet
…
csc11.005017.J8_pythia_jetjet
• Get all pions coming from
interaction point
• pT>2.5GeV
• |h|<2.7
• Average  multiplicity per
event <n> = 0.38
• 1M events simulated with
PionDecayer at various pT
Minimum bias
• 124k events
simulated with
PionDecayer
• Selected one light
meson forced to
decay
• Muon mother decay
before calorimeter
Old predictions
• Differential cross-sections
s
pT h
2
typically used to compute rates for kaons,  m, from
generators:
– PYTHIA 5.7 (JETSET 7.4)
– DPMJET II.3 and II.4
from Oren Y. and Nisati L.
• Assumed cross-section from minimum bias only
s=80 mbarn
Decay weight for CSC samples
Events reweighted for
 probability of
decaying into a m
m 
w
p   c
l
m
p

c
maximum path
 mass
 momentum
 life time
light speed
Ratio of pT distribution
for unweighted and
weighted events
Cross-sections (mbarn)
PYTHIA(*)
DPMJET (*)
(all)
( only)
(all)
( only)
Minimum
bias ( only)
3<pT<45
GeV
38.4
22.8
81.2
38.1
18.3
35.1
36.7
21.9
77.8
36.6
17.0
32.6
4<pT<45
GeV
10.3
5.98
20.3
9.48
4.80
11.0
9.85
5.73
19.5
9.10
4.50
10.2
5<pT<45
GeV
3.56
2.04
6.51
3.04
1.58
4.32
3.42
1.96
6.25
2.92
1.48
4.0
6<pT<45
GeV
1.48
0.83
2.59
1.21
0.63
1.96
1.42
0.79
2.49
1.16
0.60
1.81
sot(m)
Single 
|h|<2.7
|h|<2.4
(*) Oren Y. and Nisati L.
DPMJET default for rates computation (more conservative)
pT and h projections
PYTHIA
DPMJET
Single 
Min bias
4000<pT<45000 MeV
h
|h|<2.4
pT
In the following we will
restrict to:
4000<pT<45000 MeV
(min bias: pT<20000 MeV)
|h|<2.4
PYTHIA / DPMJET all light hadrons
pT
h
PYTHIA  / DPMJET 
pT
h
PYTHIA  / single 
pT
h
DPMJET  / single 
pT
h
PYTHIA  / min bias,  only
pT
h
DPMJET  / min bias,  only
pT
h
Conclusions
• There are differences between old
predictions from PYTHIA and DPMJET
(within a factor 1.5)
• New samples give cross-section predictions
in agreement within a factor of 2
– We have good samples suitables for studying
rejection of muons from light mesons