1. Parasitic Run Physics Simulations
HPS Collaboration Meeting
October 17 – 19, 2011
Parasitic Run Physics Simulations
Takashi Maruyama
SLAC

2. Introduction
The goal of the parasitic run is to commission the HPS apparatus and check the performance.
Physics simulation is used to estimate the rates in Ecal and Tracker.
Ecal
One cluster trigger
EM trigger
MIP trigger
Two cluster trigger
 e+e-
Energy calibration
0
High rate trigger and DAQ
Tracker
Tracking performance
Pattern recognition
Tracking efficiency
Momentum resolution
Different B field
Vertex resolution
 e+e- , 0/K0+-
Mass resolution
K0, ,  decays
Tracker alignment
No field data

3. Rate estimates in the parasitic run
Beam
107 ’s/sec with 1/k (kmin=0.20Ebeam, kmax=0.95Ebeam , Ebeam=4.4 GeV )
Use 1.4107 ’s/sec (kmin = 0.5 GeV, kmax = 4.4 GeV)
Target
0.1% X0 Gold at z= -60 cm
Detector
Dead zone is 10 mrad
Ecal
10 mr
y= 20 mm
Target
y = 7mm
3 mm (uncollimated)
1.5 mm (collimated)
Z = -60 cm
Z= 137 cm

4. Simulation +Au interactions are simulated. Acceptance EM interaction
Geant 4 and EGS5
Hadronic interaction
Geant 4 and FLUKA
Cross sections are not well known. Use measured p cross sections and scale them to estimate Au cross sections. Large uncertainties.
Acceptance
Particles that came out of the target are tracked in the PS field.
Acceptance is B field dependent.
We want 5 kG, the test run field.
Geometrical acceptance is calculated.
10 mrad dead zone
For charged hadrons, FLUKA generated particles are used.
0 and K0+- decays are simulated.
2.5 kG kG kG
Pmin (GeV)

5. EM interactions pair  50 b, 14 kHz compton 100 mb, 28 Hz
Pairs polar angle  me/E
Not many pairs reaching Ecal at |Y| > 2 cm.
compton 100 mb, 28 Hz
 e+e- at Ecal
Y (cm)
X (cm)

6. Pairs at large angles
Geant4 and EGS5 are in good agreement for pair production rate.
However, EGS5 predicts more pairs at large angles.
This is due to an exp-based angular distribution ( exp(-/0)) used in Geant4.
Only e+ or e- reaches Ecal at |Y| > 2 cm. The double rate is 1 Hz.
y (e+)
y (e-)

7. Hadron photo-production
A dependence
J. Ballam et al,
Phys. Rev. D5, 545 (1972)
 +/-
  100 b
1/A d/d A
Assume (A)A(p)
p  p
 0
H. Van Pee et al,
v1 [nucl-ex]
  100 b

8. Hadron photo-production
 K+/K-/K0
 
A. Salam et al, PRC 74, (2006)
E. Anciant et al, PRL 85, 4682 (2000)
  0.5 b
  1.5 b

9. Rates  (A) Total rate Single Rate in Ecal
Single Rate in Ecal/Tracker
Double rate in Ecal
Double rate in Ecal/Tracker
e+e-
50 b
14 kHz
39 Hz
24 Hz
1.0 Hz
0.6 Hz
e-
100 mb
28 Hz
4.6 Hz
0.9 Hz -
A +x
20 mb
5.6 Hz
0.2 Hz
0.09 Hz *
A0 +x,
0
4 Hz
0.1 Hz
AK +x
300 b
0.08 Hz
AK0 +x,
K0+-
A+x,
K+K-
100 b
0.03 Hz
* Test run tracker/Ecal does not have an acceptance at M > 250 MeV.

10. Summary The Ecal single rate is 50 Hz, dominated by pairs.
The Ecal double rate is 2 Hz.
The tracker rate is 1/2 Ecal rate.
To test high rate Ecal trigger and DAQ, we need to increase the rate by using higher beam current, thicker converter and lowering/turning-off magnetic field.
There are enough 0 for Ecal calibration.
Although K0/ decays would be useful for vertexing and mass calibration, the test run apparatus does not have an acceptance at M > 250 MeV.

11. K0 +-
Target
Tracker
Ecal