Electron Triggering and B-Physics at L3(BJ/Ks, where J/ ee)

Abid Patwa, André Turcot, and Sailesh Chopra

B-id Vertical ReviewDØ, Fermilab

Wednesday, April 4, 2001

• Motivations for Study and Trigger Constraints

• Summary of Previous Studies and Work– L1 and L2 study of J/ ISAJET events

• Current Work & Studies – L3 filtering using TRK, CPS and CAL information – Progress report

• Overview• Resolution Study: Matching, Invariant Mass• Preliminary efficiency results

• Future Plans and Proposals

AGENDA

Motivation for Study

• Maintain B-physics analysis with high statistical sample

• Use electron decays of J/’s in addition to muons• Calibration of detectors in low energy range

– reconstructed J/ mass

• understand detector alignments fit M J/ to alignment constants

• Establishing relative energy scales between the CC and EC

– coupled to preshower readout capabilities • AFE12 board -- dual threshold, charge division, etc…

Constraints for J/ ee trigger

• L1 accept rates defines J/ trigger rate ~ 1.5kHz for both central/forward region

• L2 accept rate below a maximum of ~100 Hz• L3 accept rate kept below ~1-5 Hz

Necessary to understand trigger resolution and efficiencies for all of the above issues

Summary of Trigger Studieswith electrons from J/’s

• Initial L1 and L2 studies performed (mainly upgrade GEANT):– DØ Note 3249 by Y. Gershtein

• low pT electrons from b-quarks

• central region: -1.5 1.5• algorithm: combined CFT tracks and CPS hits

– DØ Note 3506 by P. Grannis • J/ trigger in central region (ISAJET) • algorithm: combined CPS and CC info• Results: efficiencies ~6-10% achieved, dependent on

CC thresholds• Reasonable trigger rates: L1 1 kHz and L2 50 Hz

– DØ Note 3566 by A. Lucotte• J/ trigger in forward region (ISAJET)• algorithm: combined FPS and EC info• reconstructed events processed with upgrade GEANT• Efficiencies as function of FPS strip and ECEM

thresholds, Inv. Mass dist.,... see DØ Notes for details

• Further studies at L1, L2 ?– Recently started using tsim_l1 and l2, dØtrigsim– Progressing…

• Studies at L3: (Patwa, Turcot, Chopra)

– Also recently started, progressing well – will outline general scope here

L3 Electron Studies (J/ ee)A. Patwa, A. Turcot, et. al.

• Initial work in past ~4-5 months: – Unsuccessful for physics studies

• Modified electron results — CAL and CPS info • Number of code breaks, tsim_l3 output crashes• incompatible datafiles with L3 code: require

generating files with RawDataChunks

• Short-term:– Given limited statistics in MC, develop machinery

for future studies with larger samples “standard” Root macro

– Establish foundation

• Long-term:– Extract efficiencies, purity, invariant mass dist.,

…– Understand backgrounds, etc...

Proposal

• Sample:– processed under dØsim p07.00.03

• J/ ee, 1000 events total (two 0.5K files)

• Event selected: pythia+QQ; PT (B) 3.0 GeV

• at least 2 electrons with PT (e) 1.0 GeV, || 2.5

– Avg. min. bias overlay: |NMB|=1.1, Poisson distribution

– Sample processed under p06.00.01 (mod) dØTrigSim

• Modifications in dØTrigSim:– l3fanalyze:

• change track extrapolation to 73.96 cm (CPS) from 60 cm (Solenoid)

– l3fcps: • change max number of SLCs from 31 to 63

– l3femtools: • change call to L3TCPS to not use z information • change call to L3TCPS to use log weighted Phi position• Note: CAL cluster is taken wrt to PV, but PV used is not

stored (p06.00.01)…

– trig_mcc3.lst:• change PT(e) threshold for CFT tracks from 3 to 1 GeV

• Study concentrates on L3 output: – e+/e-: TRKing, CPS, and CAL information– RootTuples, variable definitions:

• some L3 variables straightforward to understand; other variable descriptions difficult must look at code to understand; little documentation

• see http://www-d0.fnal.gov/~abid/b_id_studies.html

– L3 Tracking: CFT only

L3 Electron Studies: J/ee (cont.)

L3 Electron Studies (cont.)

Primary L3 Ntuple variables studied: (Global.L3DebugE)• currently available in l3fanalyze (I.e., running d0trigsim)• TRK

– L3DEntracks -- Number of tracks– L3DETrphi -- Track Phi– L3DETrZ -- Track Z (wrt PV)

– L3DETrPtinv -- Track 1/PT

– L3DETrR -- Track radius of curvature R– L3DETrTanl -- Track Tan(), = track’s dip angle

• CAL– L3DEncal -- Number of CAL clusters found by L3TCalCluster– L3DECalPhi -- Cal cluster Phi (vector sum)– L3DECalEta -- Cal cluster Eta (vector sum)– L3DECalWZ, WR, Wphi -- Cal (log-weighted sum) Z, R, phi – L3DECalEt -- Cal cluster measured Et– L3DECalEmfr -- Cal cluster EM fraction– L3DECalEfr1, … L3DECalEfr5 -- Cal cluster E frac. in EM1,

…,EM4, FH1

• CPS a.) Form Single Layer Clusters (SLCs): cycle through hit CPS strips, ganging adjacent hit strips into clusters.b.) Form 3D clusters -- matching hits in all three layers.

– L3DEncps -- Number of CPS clusters– L3DECpsN1, N2, N3 -- Number of CPS strips above threshold in

CPS layers 1, 2, 3– L3DECpsE1, E2, E3, -- CPS-SLC energy in CPS layers 1, 2, 3 – L3DECpsE -- CPS 3D cluster energy (E1+E2+E3)– L3DECpsPhi -- CPS Phi– L3DECpsZ -- CPS hit z-position– L3DECpsChic2 -- CPS 2

– L3DECpsRes -- CPS hit residuals

L3 J/ Studies: Matching Resolution

• Use MC information

– identify only e in data sample, PT 1 GeV

• Electrons “tagged” by matched tracks– Require R = (2+ 2) 0.07

• Basic Approach:– Study matching performance for “tagged” e by

cycling/pairing subsystems: CFT, CPS and CAL

Comparison: MC electrons with tracks (TRK) and CAL

CAL-MC TRK-MC

CAL-MC TRK-MC

J/ electrons — Matching Resolution: TRK-CAL

• Resolution in : RMS = 63 mrad– okay central core, dominated by tails– may need some improvements… – Benchmark: compare to other L3 electron studies (Z

ee, Upsilon ee ): RMS (10-25 mrad) -matching long tails:

– Track assumes zo of track as primary

– under investigation… probable effect: from CAL determination (primary vertex info…)

“Tagged” e: CFT tracks and CAL clusters

R

J/ electrons — Matching Resolution: CPS-CAL

• Resolution in : RMS = 29 mrad– better, but may need some more work...

-matching long tails:– Similar to TRK-CAL

– CPS assumes zo of tagging track as primary

“Tagged” e: CPS clusters and CAL clusters

R

J/ electrons — Matching Resolution: CFT-CPS

• Improved resolution in : RMS = 6.1 mrad– Two peak distribution from track propogation (B-Field)

• separated ve and ve tracks at ~ 0• effect known, see: A. Turcot’s study on “Electron-ID

using CPS, L3fcps” — on b-id “documents” web-page for ve tracks improves RMS = 4.5 mrad

• z-matching: needs work– indications are that z(trk) is dominant

“Tagged” e: CFT tracks with CPS clusters

z

z

-

J/ electrons — Invariant Mass

• Calculation based on:

For “tagged” e: MC, CAL, CAL-TRK, TRK

M(ee)

12122121 2 coscoshEEeeM TT

• TRK gives mass closest to expected• CAL energy scale is off

– requires work...

• TRK-CAL calculation – driven by CAL energy scale

• Comment: substantial improvement in M(ee) with CFT PT = 3 1 GeV (trigger list modification)

M(ee)

M(ee)

M(ee)

MC CAL

CAL-TRK TRK

J/ electrons — Matching Efficiency

For “tagged” e: Initial Result on Matching Performance

• Very Preliminary; but a start…

• Substantial improvement with CFT PT = 3 1 GeV (trigger list modification)

Bin Description No. of e % of e

1 GeV 3 GeV 1 GeV 3 GeV 1 MC (all e) 2130 2130 — —

2 e matched TRK 1395 333 65.5 15.6

3 MC-TRK in CPS fid. 1130 271 53.0 12.7

4 e matched CPS 551 222 25.8 10.4

5 TRK-CPS, matched CAL 551 222 25.8 10.4

6 e matched CAL 1290 330 60.5 15.5

7 TRK-CAL in CPS fid. 1025 265 48.1 12.4

8 TRK-CAL, matched CPS 548 232 25.7 10.8

Selection Criteria

• Develop electron selection criteria– Try at best to optimize selection, very preliminary– again, No L1 and L2 applied

• Basic selection cuts:– kept loose (now)

– CAL ET 1 GeV, || 2.0, Efrac 0.8

– Define CAL-TRK match: || 0.07– Define CAL-CPS match: || 0.05

• Classify electrons in four categories:– 1) “Golden Electron” — TRK, CPS, CAL– 2) CPS-CAL only– 3) TRK-CAL only– 4) CAL only

• For J/:– consider only Type 1 and 3 electrons – controlling trigger rates requires at least a track

• Apply cuts for each:– Type 1: TRK-CPS: |z| 20 mm, || 12 mrad

– Type 3: TRK-CAL: || 50 mrad, Efrac 0.95

J/ electrons — Selection Criteria & e-types (cont.)

• BJ/Ks, where J/ ee: 1K sample

• Most candidates are “Golden”

J/ Signal: Event Selection

J/ electrons — Selection Criteria (cont.)

• Calculation based on:

Invariant Mass: electron selection criteria applied

M(ee)

12122121 2 coscoshEEeeM TT

• Similar to results from MC tagged e

– CAL energy scale shift

– at PT 6 GeV, p-scale of CFT-only tracking becomes non-linear

M(ee)

M(ee)

CAL info TRK

CAL-CPS

J/ electrons — Selection Criteria (cont.)

• 8K QCD_20 and 9K QCD_40 samples processed with p07.00.01 dØsim

• Background studies have just started…– at the moment, results — a day old– but: a move forward...

Invariant Mass: Look at Type 1 & 3 Combinations

with Background

M(ee)

Preliminary Results

J/1 K Sample

TRK onlyresult

QCD20 GeV8 K sample

TRK onlyresult

M(ee)

Closing Remarks

• Initial work by A. Lucotte, P. Grannis, et. al. provides useful benchmark for future trigger studies – At all trigger levels, L1 L3

• L3 studies (finally) underway– Very preliminary but tremendous progress has

been made!– Analysis machinery being developed– Distribution shapes and cross-checks being done

with Zee and Upsilon(1s) ee samples– Large amount of work still needed...

– Future Work:• Aim for larger statistical sample• Efficiencies and Purity studies…• Improvements in invariant mass distributions... • Background studies: QCD events• Perform studies with SMT+CFT tracks (L3 global

tracking, d0trigsim)• Incorporate L1 and L2 information…

– will require LARGE samples

Reference Slides

Preshower Readout Logic

• AFE12 board -- dual threshold, charge division scheme

• Two-arms:– High-gain Low PT physics

• CP-violation, B-Physics, J/,…

– Low-gain High PT physics

• Higgs, Top, W/Z physics, …