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Status of PSD A.Ivashkin (INR, Moscow)

Status of PSD A.Ivashkin (INR, Moscow). PSD structure. In-beam performance in Be run. Performance in Pb test run. PSD trigger in Be run. Status of calibration. Future steps. PSD – Projectile Spectator Detector. PSD in 2011. Compensating calorimeter

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Status of PSD A.Ivashkin (INR, Moscow)

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  1. Status of PSDA.Ivashkin (INR, Moscow) • PSD structure. • In-beam performance in Be run. • Performance in Pb test run. • PSD trigger in Be run. • Status of calibration. • Future steps.

  2. PSD – Projectile Spectator Detector PSD in 2011 • Compensating calorimeter • Pb/scintillator (4/1) 60 sandwiches in one module • Modules 10 x 10 x 120 cm3 – central part • Modules 20 x 20 x 120 cm3- outer part • 10 longitudinal sections with 10 MAPDs readout • Precise measurement of the energy • of projectile spectators. • Centrality selection (on trigger level) • Measurement of event-by-event fluctuations (to reduce Npartfluctuations) • Reconstruction of the reaction plane PSD modules in 2011 Be-run 16 central modules in trigger

  3. Photo of PSD after full construction (Feb.2012) Rear side before FEE installation Front 44 modules 440 MAPDs and readout channels 17 tons

  4. PSD performance in 2011 7Be run

  5. Energy in PSD vs Z-detector (Be-run 2011) 40 AGeV Run 15258 special, target IN trigger S1 75 AGeV Run 15161, target IN Trigger T4 Be Be He d He d Off-time particles 150 AGeV Run 14946, target OUT All triggers Be He d

  6. Energy in PSD for beam trigger 40 AGeV Run 15258 special, target IN trigger S1 75 AGeV Run 15161, target IN Trigger T4 150 AGeV Run 14946, target OUT All triggers d He He Be d Be Be He d Beam energy (AGeV) 40 75 150 Etotal (GeV) Resol. ( %) Etotal (GeV) Resol. (%) Etotal (GeV) Resol. (%) 2H 80 11.8 150 9.2300 6.6 4He 160 8.1 300 7.0600 6.7 7Be 280 6.4 525 6.11050 4.1 The PSD on-line resolution ~90%/sqrt(E) is about 1.5 times worse of expected one. Further improvement needs the accurate energy calibration.

  7. 7Be-1024 GeV 4He- 520 GeV 2H-253 GeV PSD spectrum for 150 GeV beam(calibration of scale) E1n(7Be)=150 GeV But E1n(4He)=130 GeV Why? The reason is rigidity of beam r=P/Z=const. P1n(4He)x4/2=P1n(7Be)x7/4 P1n(7Be)x7=P1n(4He)x4/2x4=P1n(4He)x8

  8. Pb+Pb@80 AGeV (test runs) Pb energy peak ~11 TeV Expected -16 TeV (ADC saturation) ADC saturation is avoided T1 All triggers Minimum bias spectrum Calibration needed after HV changes T2 T2 Runs 15418 - IN The same HV as for Be runs Run 15438 – IN HV for 2 beam modules are decreased For heavy ions the HV adjustment of in-beam modules is required to avoid the ADC saturation

  9. Deposited energies in PSD modules 7Be + 9Be@75 AGeV 7Be + 9Be@40 AGeV Pb + Pb@80 AGeV neutrons Pb-beam position at PSD is not optimized!

  10. PSD trigger in 2011 7Be run

  11. PSD trigger - T2 (interaction): deposited energy in PSD is less of some thresholds To avoid the contribution from e/m particles first section in each central module was out of trigger 7Be + 9Be@75 AGeV Sharp cut according to trigger threshold non-interacting beam ions Energy of first sections is added W/o section 1 To avoid the contribution of non-interacting beam ions first section must be in trigger!

  12. Energy in PSD (central part): triggers T1(beam) and T2 (interaction) 40A GeV 7Be + 9Be 75A GeV 150A GeV Significant part of T2 triggers has no interactions because of exclusion of first section from trigger. Problem is fixed now! First section is in trigger!

  13. 300 ns 60 ns Future plan: Modification of PSD trigger (faster PSD signal) MAPD signal M~5x104 ADC signal integrated signal M~107 At present:the PSD trigger signal comes after integrators with rise time ~60 ns: too slow and too large time-amplitude walk. Needs careful adjustment for each beam energy. Future plans: trigger signal after MAPD – fast signal, no problem with time walk and delay. Test of fast trigger to be done in June, 2012. Modification in 2013. First section is in trigger from Feb.2012!

  14. Status of PSD calibration

  15. Matrix method of energy calibration with protons Ten sequential events are used to find 10 unknown calibration parameters in 10 sections of one PSD module Aj1-10 – amplitudes of the signals in sections 1-10 for event j C1-10 – calibration parameters for sections 1–10 (to be found) Calibration was done with p@158 GeV , each module was scanned

  16. Deposited energy in clusters reconstructed with final calibration parameters CLUSTER 1: hit module – small module 6 Beam spots Cluster 1 Deposited energy 155.8 GeV Resolution 7.6% 25 Cluster 2 Module 6 CLUSTER 2: hit module – large module 25 Deposited energy 153.7 GeV Resolution 7.1% Module 25 MC expected resolution ~6.5%

  17. Resolution Comparison of energy reconstruction with all modules and with clusters Reconstruction with all modules Reconstruction with clusters Mean value Resolution According to MC the resolution should be 6.5% We see larger mean values and worse resolution for all modules comparing with clusters: • Larger contribution of electronic noise? - unlikely – see next slide. • Additional energy from background events ? One needs to understand why 1/3 of modules has significantly worse resolution Accuracy of calibration parameters depends on beam spot position at front of PSD module

  18. Dependence of energy resolution on noise cut •reconstr. with all modules • reconstr. with clusters (noise cuts – 7/10 ch - small and large) • reconstr. with all modules • reconstr. with clusters (noise cuts – 10/12 ch - small and large) Reconstruction with all modules Reconstruction with clusters (noise cuts – 5 /7 ch – small/large) sE/E~70%/sqrt(E) sE/E=60%/sqrt(E) Noise is not responsible for worse resolution

  19. Strategy ofPSD calibration in June, 2012 2007 SPS muon beam pedestal Muon peak 1. Calibration of each module with ~100 GeV muons. - straightforward evaluation of calibration parameters from muon peaks. But… very close to pedestal. 2. Calibration of each module with 158 MeV/c protons. Matrix method of calibration. One needs accurate beam positioning at the module centers. Remote control on PSD platform is requested! Backup option – two web-cameras for X- and Y-axis of PSD platform.

  20. Future steps on PSD activity • Calibration of all modules with protons (158 GeV/c) and muons – June, 2012 • Evaluation of new set of calibration parameters for 2012 beam run. • Improvement of calibration algorithm and energy resolution. Our goal is sE/E~60%/sqrt(E). • Development of cluster algorithm in energy reconstruction. Suppression of contributions from secondaries. • Test of new fast trigger scheme – June, 2012 • Implementation of fast trigger scheme for all modules – 2013.

  21. Thank you!

  22. Energy in PSD: trigger T2 (interaction) 7Be + 9Be@75 AGeV Non-calibrated data Calibrated data All sections W/o section 1 First section must be in trigger!

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