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)

Feb 24, 2008 2

Outline

• TB04– Events observed, analysis of TB04 data

• Geant4 Simulations– PMTs added– Muons, pions, jets

• FNAL Feb. 08 testbeam – Preliminary results

Feb 24, 2008 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.

Feb 24, 2008 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.

Feb 24, 2008 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.

Feb 24, 2008 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.

Feb 24, 2008 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)

Feb 24, 2008 8

150 GeV Muons

Depth 3 & 4(PMT window sim_hits)

Feb 24, 2008 9

Use of Pythia for u-quark Jets

Pt: 20GeVeta: 3 - 4phi: 0 - 360 deg

Feb 24, 2008 10

Hits in Depths 3 &4

Pt 20 GeV jets (up quarks) Pt 100 GeV jets (up quarks)(100,000 events) (90,000 events)

Feb 24, 2008 11

Pt of Abnormal Events20 GeV jets 100 GeV jets

Pt (GeV) Pt (GeV)

Depth 3 & 4 Depth 3 & 4

Feb 24, 2008 12

Abnormal Event Rates

Pt 20 GeV jets (100k events) Pt 100 GeV jets (90k events)

Pt (GeV) Pt (GeV)

Feb 24, 2008 13

η of Abnormal Events (20 GeV jets)

genrated

Pt > 80GeV

Pt >40GeV

Pt>160GeV

Feb 24, 2008 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.

Feb 24, 2008 15

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

Feb 24, 2008 16

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)

Feb 24, 2008

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)

Feb 24, 2008 18

Angle Study

PMTLYSO

Histograms have 10k eventsBeam: 16 GeV proton without HF Absorber

BeamBeam

30 degrees

Pedestal

ADC SaturationADC Saturation

Pedestal

PMT

PMT

LYSO

Feb 24, 2008 19

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