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Low mass dimuon acceptance
Shiuan-Hal Shiu
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Contents Introduction The result of varying M1 current
Dump/Target separation Conclusion
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The location of M1 and M2 Configuration file
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Why varying the magnet current
Original Want
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Why varying the magnet current
In low mass region the dimuon events have small opening angle
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Fix M2 current and vary M1 current
Use the E906 Fast Monte Carlo simulation for study configuration data. The configuration file is “fe198v5.dat”. By changing the entry “current and step to scale” we can adjust the M1 or M2 current. The input to the simulation is decided by Ykick*input/2000 and the tracking plane from #2 to #13 will affected by this factor.
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The top diagram is the mass distribution of generated dimuon pairs.
The middle diagram is the mass distribution of accepted dimuon pairs. The bottom diagram “Acceptance” as a function of dimuon mass.
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The mass range of generated dimuon pairs is from 0.2Gev to 15Gev
Green line is the acceptance value with the original M1 current setting. By increasing the current we find that the peak of acceptance is shifting to high mass end. Reducing the M1 current can increase the acceptance in the low- mass region. /Fastmc/090413/im2 m=2
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Fix M1 current and vary M2 current
Fix the M1 current, and change the M2 current (Ykick).
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M2*1.5 M2*1 M2*0.5
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M2*1.5 M2*1 M2*0.5
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M2*1.5 M2*1 M2*0.5
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Dump/Target separation
Cuts conditions Purple: all events Green: xF>0 and M>4.5 GeV and pz>20 GeV Blue: Green and |ytrack|>2.25 in at z=0 (zdump) Red: Blue and |ytrack|<10.0 in at z=-60 (zstart) Target Dump
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Dump/Target separation
Runrunscan#dump Target retrace and dump retrace can be separated Target retrace and dump retrace can not be separated
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Dump/Target separation
1 3 /anachcurrent/zrtr.kumac exe zrtr#runse 2 4
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Dump/Target separation
1 3 /anachcurrent/zrtr.kumac exe zrtr#runse 2 4 Reducing the M1 current will lead the z resolution bad.
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Change the target location
/layout/qqq.kumac The target original location is at -70 to We change it to -150 to -130.
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Change the target location
M1*0.5 1 3 2 4
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Change the target location
M1*0.1 1 3 2 4 Changing target location can not improve the z resolution.
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Moving the cut condition at zdump to Station 1 and change the value.
Cuts conditions Purple: all events Green: xF>0 and M>4.5 GeV and pz>20 GeV Blue: Green and |ytrack|>2.25 in at z=0 (zdump) Red: Blue and |ytrack|<10.0 in at z=-60 (zstart) Moving the cut condition at zdump to Station 1 and change the value.
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Cutana&cutana#dc Original Changed
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Changed Original Try |ytrack|>8 in at z=238 (before station1)
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M1*0.5 1 3 2 4
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Changing cut condition can not improve the z resolution.
1 3 2 4 Changing cut condition can not improve the z resolution.
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Check the relations of retrace mass and retrace z
Left diagram is using the original cut condition. The mass cut is “>4.5Gev” here. After applied the cut(mass >4.5 Gev) , we can see that the events are almost spread in the region which less than z=0. Mrtrvszrtr#run
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Check the relations of retrace mass and retrace z
Left diagram is using the original cut condition but mass cut is “<4.5Gev”. After applied the cut , we can see that the events are still scattered throughout the x axis. M1*0.5 M1*0.1
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Momentum Difference(X) (M1*0.5)
/FastMC/anachcurrent/diffkin#mainc
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Momentum Difference(Y) (M1*0.5)
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Momentum Difference(Z) (M1*0.5)
/FastMC/anachcurrent/diffkin#mainc
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Pt/Pz(positive) (M1*0.5)
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Pt/Pz(negative) (M1*0.5)
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Opening angle of muon pairs
fe198v5m101 mrtr.le.4.5 zrtr.le.0 fe198v5m101 mrtr.le.4.5 zrtr.ge.0 fe198v5m101_dump mrtr.le.4.5 zrtr.le.0 fe198v5m101_dump mrtr.le.4.5 zrtr.ge.0
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Momentum Difference(X) (M1*0.1)
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Momentum Difference(Y) (M1*0.1)
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Momentum Difference(Z) (M1*0.1)
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Pt/Pz(positive) (M1*0.1)
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Pt/Pz(negative) (M1*0.1)
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Opening angle of muon pairs
fe198v5m101 mrtr.le.4.5 zrtr.le.0 fe198v5m101 mrtr.le.4.5 zrtr.ge.0 fe198v5m101_dump mrtr.le.4.5 zrtr.le.0 fe198v5m101_dump mrtr.le.4.5 zrtr.ge.0
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Conclusion Reducing the M1 current can increase the acceptance of low mass dimuons. Adjusting the M2 current does not change the acceptance significantly. Howerer, decreasing M2 current can enlarge the acceptance. After reducing the M1 current, the z resolution is become bad. Changing target location and cut condition can not improve the Dump/Target resolution. Low mass events are affected by the multiple scattering seriously.
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backup
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Theta y distribution of positive muon at zstart
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Theta y distribution of positive muon at zstart
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Theta y distribution of negative muon at zstart
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Theta y distribution of negative muon at zstart
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Momentum distribution of positive muon at zstart
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Momentum distribution of positive muon at zstart
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Momentum distribution of negative muon at zstart
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Momentum distribution of negative muon at zstart
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X distribution of positive muon at zstart
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X distribution of positive muon at zstart
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X distribution of negative muon at zstart
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X distribution of negative muon at zstart
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Theta x distribution of positive muon at zstart
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Theta x distribution of positive muon at zstart
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Theta x distribution of negative muon at zstart
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Theta x distribution of negative muon at zstart
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Xf distribution of muon at zstart
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Xf distribution of muon at zstart
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X1 distribution of muon at zstart
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X1 distribution of muon at zstart
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X2 distribution of muon at zstart
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X2 distribution of muon at zstart
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Total momentum distribution of muon at zstart
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Total momentum distribution of muon at zstart
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Station 1 Chamber Rates Occasionally a muon showers in the absorber
Absorber and B Field Occasionally a muon showers in the absorber If this happens in the center of the absorber, no effect is seen as shower is also absorbed If this happens in the last few inches of the absorber, shower can create extremely large rates in Station 1 (of low momentum particles) Solution is to have an absorber- free region at the end of the field volume and use field as a sweeper In Solid Iron magnet, there is no absorber-free sweeper region! (Can we find a wide gap sweeper magnet?) Requires GEANT MC to see magnitude of effect Absorber and B Field Absorber and B Field B Field only
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