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Abnormal Events in HF: TB04, Simulation, and Feb.08 Fermi Testbeam

Abnormal Events in HF: TB04, Simulation, and Feb.08 Fermi Testbeam. Anthony Moeller (U. Iowa) Shuichi Kunori (U. Maryland) Taylan Yetkin (U. Iowa) Jim Freeman (Fermi). Outline. TB04 Events observed, analysis of TB04 data Geant4 Simulations PMTs added Muons, pions, jets

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Abnormal Events in HF: TB04, Simulation, and Feb.08 Fermi Testbeam

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  1. Abnormal Events in HF:TB04, Simulation, and Feb.08 Fermi Testbeam Anthony Moeller (U. Iowa) Shuichi Kunori (U. Maryland) Taylan Yetkin (U. Iowa) Jim Freeman (Fermi)

  2. Outline • TB04 • Events observed, analysis of TB04 data • Geant4 Simulations • PMTs added • Muons, pions, jets • FNAL Feb. 08 testbeam • Preliminary results

  3. TB04 analysis from 2005 • 100 GeV pions from TB04 • While analyzing TB04 data during the summer of 2005, abnormally high energy events were seen in several pion runs.

  4. Abnormal Events • These events are most likely to be from Cerenkov radiation from particles directly hitting the PMT window. • peak of muon signal ~ 200 GeV • The glass window is plano-convex. • 1mm thick in center • 6.1mm thick at the edges • These events were also seen in TB07 by Freeman et. al.

  5. 300 GeV Pions • Out of 186878 events for 300 Gev pions aimed at tower 2: • 4056(2.2%) have at least 1 channel with more than 600 GeV. • 3625(1.9%) have at least 1 channel with more than 600 GeV when excluding channels 1 and 14. • 42679(22.8%) have more than 600 GeV per event when summing over all channels. • 7513(4.0%) have more than 600 Gev per event when summing over all channels except 1 and 14.

  6. Assorted comments on TB04 Analysis • Event filters using S/(L+S) and timing have been studied. • Using a value of 0.2 for Δcut from the mean value of S/(L+S) for normal pions: • ~5% of “normal” events would be rejected. • ~85% of “abnormal” events would be rejected. • We looked at several electron runs, abnormal events were not observed. • A CMS internal note has been submitted on this analysis • See talk from last CMS week. • Event filters need to be test for jets at the LHC • New HF simulation is under development • Preliminary results – today.

  7. Geant4 HF Simulation • The original HF simulation only had two depths, one for long fibers, and another for short fibers. • In order to correctly identify abnormal events that were hitting the PMT windows, it was necessary to add the PMT windows to the simulation, these were added as discs located behind HF. • The hits recorded in these discs are represented by two additional depths, one for PMTs corresponding to long fibers, and another corresponding to short fibers. • There are now four total depths for HF. • Working in CMSSW_1_7_0. Rough schematic of PMTs behind HF. The two different colors represent long and short PMTs. Actually 48 PMTs per wedge, only 8 shown. (see Sunanda’s talk today)

  8. 150 GeV Muons Depth 3 & 4 (PMT window sim_hits)

  9. Use of Pythia for u-quark Jets Pt: 20GeV eta: 3 - 4 phi: 0 - 360 deg

  10. Hits in Depths 3 &4 Pt 20 GeV jets (up quarks) Pt 100 GeV jets (up quarks) (100,000 events) (90,000 events)

  11. Pt of Abnormal Events 20 GeV jets 100 GeV jets Depth 3 & 4 Depth 3 & 4 Pt (GeV) Pt (GeV)

  12. Abnormal Event Rates Pt 20 GeV jets (100k events) Pt 100 GeV jets (90k events) Pt (GeV) Pt (GeV)

  13. η of Abnormal Events (20 GeV jets) genrated Pt >40GeV Pt>160GeV Pt > 80GeV

  14. Feb. 08 Testbeam at Fermi • The goal of this testbeam was to test the possibility of placing a crystal in front of the PMT window to help identify abnormal events. • LYSO, BGO • As particles go through the crystals, scintillation should occur. • A large delay in the signal should also be observed. • Involvement from Fermi (Jim Freeman, Rick Vidal), University of Iowa, and Princeton.

  15. Beam Setup Lucite* Crystal Mount* 0.5mm Wire Chamber Iron and Lead Absorber Beam PMT 167cm Absorber* (full HF length)‏ Trigger Scints Scint Counter 3 Scint Counter for rates Scint Counter 2 PMT Stage * These items were not present in all beam configurations.

  16. Nb. of Events vs. Charge (pC)‏ Beam: 120 GeV proton without HF Absorber (~30k)‏ NoXtal NoXtal NoXtal NoXtal NoXtal NoXtal Delay: 32 ns Delay: 96 ns Delay: 128 ns Delay: 64 ns Delay: 0 ns Delay: 160 ns Single hit requirement. No muon id tag. w/ block: 0.3% (293/85288)‏ w/o block: 31.6% (9327/2953)‏ Beam: 120 GeV proton with HF Absorber (~85k)‏ NoXtal NoXtal NoXtal NoXtal NoXtal NoXtal Delay: 160 ns Delay: 32 ns Delay: 96 ns Delay: 128 ns Delay: 64 ns Delay: 0 ns

  17. Nb. of Events vs. Charge (pC)‏ Beam: 120 GeV proton with HF Absorber, No crystal (~85k)‏ NoXtal NoXtal NoXtal NoXtal NoXtal NoXtal Delay: 32 ns Delay: 96 ns Delay: 128 ns Delay: 64 ns Delay: 0 ns Delay: 160 ns Beam: 120 GeV proton with HF Absorber, LYSOcrystal (50k)‏ LYSO LYSO LYSO LYSO LYSO LYSO Delay: 32 ns Delay: 96 ns Delay: 128 ns Delay: 64 ns Delay: 0 ns Delay: 160 ns Beam: 120 GeV proton with HF Absorber, BGO crystal (50k)‏ BGO BGO BGO BGO BGO BGO Delay: 32 ns Delay: 96 ns Delay: 128 ns Delay: 64 ns Delay: 0 ns Delay: 160 ns

  18. PMT PMT LYSO LYSO Angle Study Beam: 16 GeV proton without HF Absorber Histograms have 10k events Beam 30 degrees Beam PMT ADC Saturation ADC Saturation Pedestal Pedestal

  19. Nb. of Events vs. Charge (pC) for Three Cases Beam: 120 GeV proton with HF Absorber • LYSO shifts the signal more than BGO. • The pedestal location (red ovals) shifts with changes in amplification. • The testbeam just finished on Wednesday; more detailed analysis continues. NoXtal LYSO BGO

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