The Muon Detector Update

Transcription

1 The Muon Detector Update Sarah K. Phillips The University of New Hampshire June 5, 2013 HPS Collaboration Meeting at Jefferson Lab, June 3-6, 2013

2 The Muon Group Muon Group Members Keith Griffioen, Leader Yuri Gershtein, Deputy Leader Maurik Holtrop Stepan Stepanyan Sarah Phillips Kyle McCarty Muon Software Group Members Sarah Phillips, Leader analysis of simulated data from each design Yuri Gershtein, Deputy Leader pi/mu separation optimization study Maurik Holtrop geometry, geometry description for input into SLIC Kyle McCarty starting on monitoring for the system

3 General System Design Located behind the ECAL (rendering in GEMC)

4 General System Design General Design from the Proposal: Four-layer design 4 Iron absorbers 30/15/15/15cm (transparent here) 4 double layers of scintillator 256 channels (fits in one VME/VXS crate); signals sent to a FADC First absorber ~180cm from target Two halves to minimize effects of the low-energy particles in the horizontal plane

5 General System Design General Design from the Proposal: Hodoscopes extruded scintillator strips with embedded wavelengthshifting fiber and phototube readout same as CLAS12 Preshower Calorimeter Borrow electronics and HV system Strips are 45mm x 10mm cross-section; cut to any length

6 General System Design General Design from Proposal: Front scintillator layer in each plane (looking in the beam direction) Back scintillator layer in each plane (viewed against the beam direction)

7 System Design for Studies Not the one that will be built! 15-double layer design for these studies 15 double layers of scintillator separated by 5 cm of iron

8 Yuri's μ/π Separation Studies Conclusions: In terms of mu/pi separation 3 layers of hodoscopes is enough Can use one of the four planned to trigger on & identify pions To get good separation at high p, one needs to put the last HS behind as much steel as we have in the simulation To get a maximum effect on pions, have the first HS behind just 5 cm of steel (or even less?) To get good efficiency for low p muons we should have the HS somewhere close, looks like cm after HS1. The HS3 should be somewhere in the middle between 2 and 4. So, absorbers of cm or cm Likely necessary to have ECAL-HS matching in the trigger. Might need cross-system triggers (i.e. >=1 ECAL cluster + >=1 muon).

9 EGS5 Background Studies For these studies: Events generated in EGS5; used as input to the GEANT4 simulation CEBAF beam bunch structure simulated by sending one bunch equivalent of electrons, 5,625 e s (6.6 GeV), through the target to generate secondaries and scattered beam particles The secondaries were followed through the apparatus to simulate the detector response Lots of plots (15 double layers!), so just showing a sampling here

10 EGS5 and Degraded Electrons EGS5 small angle multiple scattering of EGS5 likely more accurate than GEANT4 But EGS5 was missing some electrons which caused a significant background on the large negative x side of the plots. Degraded beam electrons hit edge of the vacuum box inside muon detector. Need to extend the vacuum box further. Following studies include the degraded electrons EGS5 rate (left), GEANT4 (right) at layer 6 after 30 cm of iron absorber. The z-scale is in khz/mm2.

11 Singles Rates Rates are in MHz! Pretty high for first layer (not a surprise) Cross bar is the little paddle

12 Singles Rates Rates are in MHz! Rates much more manageable than in previous versions of design Rates get lower as the layer number increases

13 30/15/15/15 cm Configuration Coincidence rates between planes studied using a 16 ns coincidence time window Left, Middle, Right Rates in khz! Note that these rates are just between front and back layers in each plane

14 30/15/15/15 cm Configuration Note that these rates are just between front and back layers in each plane

15 30/15/15/15 cm Configuration Coincidence rates between planes Note rates for two-layer (250 khz) and two-plane (20 khz) Mostly uncorrelated background

16 30/15/15/15 cm Configuration Coincidence rates between planes

17 30/15/15/15 cm Configuration Double coincidence rates between planes 7 combinations: LTxRB, LTxMB, RTxLB, RTxMB, MTxLB, MTxRB, and MTxMB Didn't have enough events in higher coincidence plots to get a significant result

18 30/15/15/15 cm Configuration Double coincidence rates between layers 7 combinations: LTxRB, LTxMB, RTxLB, RTxMB, MTxLB, MTxRB, and MTxMB

19 30/15/15/15 cm Configuration Double coincidence rates between layers 7 combinations: LTxRB, LTxMB, RTxLB, RTxMB, MTxLB, MTxRB, and MTxMB

20 5/10/30/30 cm Configuration (Yuri's) Coincidence rates between planes studied using a 16 ns coincidence time window Left, Middle, Right Rates in khz! Rates pretty high for early layers Note that these rates are just between front and back layers in each plane

21 5/10/30/30 cm Configuration Note that these rates are just between front and back layers in each plane

22 5/10/30/30 cm Configuration Coincidence rates between planes Note rates for two-layer (4 MHz) and two-plane (250 khz) Mostly uncorrelated background

23 5/10/30/30 cm Configuration Coincidence rates between planes

24 5/10/30/30 cm Configuration Double coincidence rates between layers 7 combinations: LTxRB, LTxMB, RTxLB, RTxMB, MTxLB, MTxRB, and MTxMB

25 5/10/30/30 cm Configuration Double coincidence rates between layers 7 combinations: LTxRB, LTxMB, RTxLB, RTxMB, MTxLB, MTxRB, and MTxMB

26 5/10/30/30 cm Configuration Double coincidence rates between planes 7 combinations: LTxRB, LTxMB, RTxLB, RTxMB, MTxLB, MTxRB, and MTxMB Didn't have enough events in higher coincidence plots to get a significant result

27 Threshold Studies I was using a threshold of 0.5 MeV as Stepan suggested, but then we did a study to see if we could do a higher threshold. Study Steps: Uniformly generate the hit position, Generate the deposited energy according to a Laudau distribution (mean = 2 MeV, FWHM = 0.3 MeV, Calculate the attenuated energy, Calculate the average number of photoelectrons, Generate the number of photoelectrons using a Poisson probability with the average number of photoelecrons, Calculate the measured energy, and Calculate what this is without the attenuation to find the threshold for the simulation, which applies the threshold to the hits, not to what is measured in the PMTs.

28 Threshold Studies Did the study for long strips (hits between 50cm to 110cm, 50 cm from end to PMT) and short strips (less than 15 cm long, fiber length of 30 cm. Long Short Looks like we could raise the threshold a little The studies in this talk were done with a threshold of 0.5 MeV

29 Summary Progress is being made, even though we became an appendix in the proposal! Many iterations on the vacuum box, cutout, detector segmentation, with more to come Plots from my studies are posted online, so if you are interested, I can give you the link(s). Plans: These are just the beam backgrounds using EGS5 events Working on muon rates and muon acceptance studies When we reach a final design (or close to it), geometry needs to be put into SLIC Wait for funding...