Abnormal Events in HF: TB04, Simulation, and Feb.08 Fermi Testbeam
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Transcript of Abnormal Events in HF: TB04, Simulation, and Feb.08 Fermi Testbeam
Feb 24, 2008 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)
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Outline
• TB04– Events observed, analysis of TB04 data
• Geant4 Simulations– PMTs added– Muons, pions, jets
• FNAL Feb. 08 testbeam – Preliminary results
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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.
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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.
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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.
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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.
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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)
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150 GeV Muons
Depth 3 & 4(PMT window sim_hits)
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Use of Pythia for u-quark Jets
Pt: 20GeVeta: 3 - 4phi: 0 - 360 deg
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Hits in Depths 3 &4
Pt 20 GeV jets (up quarks) Pt 100 GeV jets (up quarks)(100,000 events) (90,000 events)
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Pt of Abnormal Events20 GeV jets 100 GeV jets
Pt (GeV) Pt (GeV)
Depth 3 & 4 Depth 3 & 4
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Abnormal Event Rates
Pt 20 GeV jets (100k events) Pt 100 GeV jets (90k events)
Pt (GeV) Pt (GeV)
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η of Abnormal Events (20 GeV jets)
genrated
Pt > 80GeV
Pt >40GeV
Pt>160GeV
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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.
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Beam Setup
Beam
Lucite*
167cm Absorber*(full HF length)
PMT Stage
0.5mm Wire Chamber
PMT
Crystal Mount*
Scint Counterfor rates
Scint Counter 2 Scint Counter 3
Iron and Lead Absorber
* These items were not
present in all beam configurations.
Trigger Scints
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Nb. of Events vs. Charge (pC)
NoXtal
Delay: 0 ns Delay: 0 ns Delay: 32 ns Delay: 32 ns Delay: 64 ns Delay: 64 ns Delay: 96 ns Delay: 96 ns Delay: 160 ns Delay: 160 ns
Beam: 120 GeV proton without HF Absorber (~30k)
Delay: 128 ns Delay: 128 ns
NoXtal NoXtal NoXtal NoXtal NoXtal
NoXtal
Delay: 0 ns Delay: 0 ns Delay: 32 ns Delay: 32 ns Delay: 64 ns Delay: 64 ns Delay: 96 ns Delay: 96 ns Delay: 160 ns Delay: 160 ns
Delay: 128 ns Delay: 128 ns
NoXtal NoXtal NoXtal NoXtal NoXtal
Beam: 120 GeV proton with HF Absorber (~85k)
Single hit requirement.No muon id tag.w/ block: 0.3% (293/85288)w/o block:31.6% (9327/2953)
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Beam: 120 GeV proton with HF Absorber, No crystal (~85k)
LYSO
Delay: 0 ns Delay: 0 ns Delay: 32 ns Delay: 32 ns Delay: 64 ns Delay: 64 ns Delay: 96 ns Delay: 96 ns Delay: 160 ns Delay: 160 ns Delay: 128 ns Delay: 128 ns
LYSO LYSO LYSO LYSO LYSO
Beam: 120 GeV proton with HF Absorber, LYSO crystal (50k)
BGO
Delay: 0 ns Delay: 0 ns Delay: 32 ns Delay: 32 ns Delay: 64 ns Delay: 64 ns Delay: 96 ns Delay: 96 ns Delay: 160 ns Delay: 160 ns Delay: 128 ns Delay: 128 ns
BGO BGO BGO BGO BGO
Beam: 120 GeV proton with HF Absorber, BGO crystal (50k)
NoXtal
Delay: 0 ns Delay: 0 ns Delay: 32 ns Delay: 32 ns Delay: 64 ns Delay: 64 ns Delay: 96 ns Delay: 96 ns Delay: 160 ns Delay: 160 ns Delay: 128 ns Delay: 128 ns
NoXtal NoXtal NoXtal NoXtal NoXtal
Nb. of Events vs. Charge (pC)
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Angle Study
PMTLYSO
Histograms have 10k eventsBeam: 16 GeV proton without HF Absorber
BeamBeam
30 degrees
Pedestal
ADC SaturationADC Saturation
Pedestal
PMT
PMT
LYSO
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Nb. of Events vs. Charge (pC) for Three Cases
• 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.
Beam: 120 GeV proton with HF Absorber
NoXtalLYSO BGO