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RPC_sim Optimization w ith Positrons (+ Pions). Burak Bilki Argonne National Laboratory University of Iowa. (S)DHCAL Meeting January 15, 2014 Lyon, France. DHCAL Simulation Strategy. GEANT4 → points in the gas gap with energy loss - PowerPoint PPT Presentation
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1
RPC_sim Optimizationwith Positrons (+ Pions)
Burak Bilki
Argonne National LaboratoryUniversity of Iowa
(S)DHCAL MeetingJanuary 15, 2014
Lyon, France
2
DHCAL Simulation Strategy
GEANT4 → points in the gas gap with energy loss
RPC_sim → generates and distributes the charge over pads applies a threshold to determine pad hits
Simulated data → pad hits
RPC_sim tuning
Tune major parameters to reproduce the muon response (José)Match number of hits per layer in the clean regions
Tune charge at edges of chambers to reproduce tapering off of efficiency
Tune the remaining parameters to reproduce the positron response (Kurt → Burak)Match mean and sigma of Nhits distributions, longitudinal profiles, density plots
No tuning based on pion response
3
RPC_sim_ Spread functions Comments
3 R e-ar + (1-R) e-br To help the tail
4 e-ar Measurement from STAR
5 R e-(r/σ1)^2+ (1-R) e-(r/σ2)^2 Commonly used
6 1/(a + r2)3/2 Recently came across
RPC_sim_ Slope a Slope b Sigma1 Sigma2 R Q0 dcut T
3 0.0678 0.671 0.345 0.201 0.262 0.3645
4 0.0843 0.199 0.092 0.286
5 0.120 0.983 0.241 0.114 0.092 0.250
6 0.0761 0.384 0.092 0.3405
The 4 RPC_sim Versions
4
rdcut
1
weight
A
dcut
1
weight
recut
B1
weight
r
(tanh(A*(r-B))+1)/2
C
3 Versions of the dcut
dcut suppresses avalanches close to othersCan not be tuned with μ‘s
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Tuning of dcut Values
Use Positron distributions at 8 GeV
Mean of hit distribution Sigma of hit distribution Density distribution (0÷8) Longitudinal profile
Measure difference to measured distributions
Define a χ2
Tuning
Identify smallest χ2
6
RPC_sim_3_A
Best result for dcut = 0.1
MeanSigmaDensityLongitudinal profile
Simulation index
dcut
0 01 0.0012 0.0053 0.014 0.055 0.066 0.077 0.088 0.099 0.1
10 0.1511 0.212 0.2513 0.314 0.3515 0.416 0.4517 0.5
2 exponential lateral charge distribution1 dcut parameter
χ2
Simulation index
7
RPC_sim_3_A with dcut = 0.1DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
8
Simulation index
dcut
0 01 0.0012 0.0053 0.014 0.055 0.16 0.157 0.28 0.259 0.3
10 0.3511 0.412 0.4513 0.5
No best solution
RPC_sim_4_A1 exponential lateral charge distribution1 dcut parameter
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
RPC_sim_4_A with dcut = 0.05DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
10
Simulation index
dcut
0 01 0.0012 0.0053 0.014 0.055 0.16 0.157 0.168 0.179 0.18
10 0.1911 0.212 0.2513 0.314 0.3515 0.416 0.4517 0.5
Best result for dcut = 0.18
RPC_sim_5_A1 Gaussian lateral charge distribution1 dcut parameter
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
11
RPC_sim_5_A with dcut = 0.18DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
12
Simulation index
dcut
0 01 0.0012 0.0053 0.014 0.055 0.16 0.157 0.28 0.259 0.3
10 0.3511 0.412 0.4513 0.5
RPC_sim_6_ALateral charge distribution with 1(a+r2)3/2
1 dcut parameter
No best solution
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
13
Check 0.01/0.35
Simulation index dcut ecut
0 0.01 0.31 0.01 0.352 0.01 0.43 0.01 0.454 0.01 0.55 0.01 0.556 0.01 0.67 0.05 0.38 0.05 0.359 0.05 0.4
10 0.05 0.4511 0.05 0.512 0.05 0.5513 0.05 0.614 0.1 0.315 0.1 0.3516 0.1 0.417 0.1 0.4518 0.1 0.519 0.1 0.5520 0.1 0.621 0.15 0.322 0.15 0.3523 0.15 0.424 0.15 0.4525 0.15 0.526 0.15 0.5527 0.15 0.628 0.2 0.329 0.2 0.3530 0.2 0.431 0.2 0.4532 0.2 0.533 0.2 0.5534 0.2 0.635 0.25 0.336 0.25 0.3537 0.25 0.438 0.25 0.4539 0.25 0.540 0.25 0.5541 0.25 0.642 0.3 0.3543 0.3 0.444 0.3 0.4545 0.3 0.546 0.3 0.5547 0.3 0.648 0.35 0.449 0.35 0.4550 0.35 0.551 0.35 0.5552 0.35 0.6
dcut
1
weight
recut
B
RPC_sim_3_B
Best solution with 0.01/0.35
2 exponential lateral charge distribution2 dcut parameters
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
14
RPC_sim_3_B with dcut /ecut = 0.01/0.35DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
15
Best result with 0.15/0.40
RPC_sim_5_B2 exponential lateral charge distribution2 dcut parameters
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
16
RPC_sim_5_B with dcut /ecut = 0.15/0.40DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
17
Simulation index A B0 10 0.11 10 0.152 10 0.23 10 0.254 10 0.35 10 0.356 10 0.47 10 0.458 10 0.59 10 0.55
10 20 0.111 20 0.1512 20 0.213 20 0.2514 20 0.315 20 0.3516 20 0.417 20 0.4518 20 0.519 20 0.5520 30 0.121 30 0.1522 30 0.223 30 0.2524 30 0.325 30 0.3526 30 0.427 30 0.4528 30 0.529 30 0.5530 40 0.131 40 0.1532 40 0.233 40 0.2534 40 0.335 40 0.3536 40 0.437 40 0.4538 40 0.539 40 0.5540 50 0.141 50 0.1542 50 0.243 50 0.2544 50 0.345 50 0.3546 50 0.447 50 0.4548 50 0.549 50 0.5550 60 0.151 60 0.1552 60 0.253 60 0.2554 60 0.355 60 0.3556 60 0.457 60 0.4558 60 0.559 60 0.55
1
weight
r
C
Best result with 20.0/0.225
RPC_sim_3_C
2 exponential lateral charge distributionSmooth transition with 2 parameters
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
18
RPC_sim_3_C with A/B = 20.0/0.225DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
19
Best result with 40.0/0.40
RPC_sim_5_C2 exponential lateral charge distributionSmooth transition with 2 parameters
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
20
RPC_sim_5_C with A/B = 40.0/0.40DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
21
RPC_sim Charge Generation
Default Sample distribution measured with cosmic rays
dE/dx based sampling Model the gas with heed++ pC
μ
# of
prim
ary
ioni
zatio
ns
βγ
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Charge Generation using βγ
Q=5.46(1-tanh(60.8(d-0.1012)))
βγ→ d → Q
Sample βγ from cosmic muon spectrum Sample ionization location d inside gas gap from heed++
Generate charge spectrum using empirical function
23
Simulation index
dcut
0 01 0.0012 0.0053 0.014 0.055 0.16 0.157 0.28 0.259 0.3
10 0.3511 0.412 0.4513 0.5
Best result with dcut = 0.01
RPC_sim_3_A with βγ1 exponential lateral charge distribution1 dcut parameter
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
24
RPC_sim_3_A with dcut = 0.01 and βγ DataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
25
Simulation index
dcut
0 01 0.0012 0.0053 0.014 0.055 0.16 0.157 0.28 0.259 0.3
10 0.3511 0.412 0.4513 0.5
Best result with dcut = 0.01
RPC_sim_5_A with βγ2 exponential lateral charge distribution1 dcut parameter
MeanSigmaDensityLongitudinal profile
χ2
Simulation index
26
RPC_sim_5_A with dcut = 0.01 and βγDataRPC_sim
Number of hitsNumber of hits
Layer number Density bin Number of hits
Not use
d for t
uning
e+
e+
e+
π+
μ+
27
Conclusions
Even though muons are well simulated, the simulation of positrons is not trivial
The simulation of positrons depends strongly on the RPC_sim version, even though all reproduce the muons quite well
The simulation of positrons depends strongly on the dcut parameter/implementation
Treating the energy loss in the gap properly (using βγ) might be necessary Current implementation of ionization losses not yet successful Other approaches are being explored
None of the digitizers satisfactory yet
RPC_sim_5 with 2 Gaussians performs best
(I have been told that OPAL never succeeded in simulating their high granularity gaseous HCAL response)
