dpf 2002, colonial williamsburg, va may 25, 2002 1 leslie groer columbia universityjet and electron...
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DPF 2002, Colonial Williamsburg, VA May 25, 20021
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Leslie GroerColumbia University, New York
DPF 2002, Colonial Williamsburg, VA May 25, 2002
Jet and Electron Identification in Jet and Electron Identification in the Run 2 DØ Detectorthe Run 2 DØ Detector
Tevatron Run 2 DØ Detector upgrade
SMT CFT Preshower + ICD Calorimeter
Jet ID Algorithms NADA Trigger Selection Energy Scale QCD Results
EM ID Reconstruction Trigger Profile Scale
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DPF 2002, Colonial Williamsburg, VA May 25, 20022
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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DØ roll-in
Run II start
First Collisions
Detector Commissioning;Timing in; Improve electronics,DAQ and offline
Main Injector(new)
Tevatron
DØCDF
Chicago
Booster
1.961.8s (TeV)
36x366x6#bunches
Run 2aRun 1b
Tevatron Run 2
p source
4.82.32.5interactions/xing
1323963500bunch xing (ns)
10517.33.2 Ldt (pb-1/week)
5.2x10328.6x10311.6x1030typ L (cm-2s-1)
1.96
140x103
Run 2b
New Main Injector and Recycler rings Increased luminosity and energy 48 pb-1 delivered 15.2 pb-1 recorded physics events L dt expected for 2002: 300 pb-1
Run 2a: 2 fb-1
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DPF 2002, Colonial Williamsburg, VA May 25, 20023
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Overview of Run 2a DØ Upgrade
Muon, Calorimeter, Silicon fully commissioned and operational
Fiber tracker and preshowers fully instrumented. Central electronics complete, forward in a few weeks—commissioning this summer
Upgrade Calorimeter electronics readout and trigger
Add scintillator in muon for fast trigger and extended coverage for drift chambers
Replace inner tracking volume with Silicon and Fiber trackers with 2T solenoid magnetic field for central tracking and momentum measurement
Add preshower detectors and replace intercryostat detectors
Pipelined 3 Level trigger Increase DAQ capability for 132 ns
bunch crossings
azimuthal angle
pseudorapidity = -ln tan(/2)
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Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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SS: single sidedDS: double sided
More in Harald Fox’s talk
Silicon Microstrip Tracker
6 Barrels
12 F-Disks4 H-Disks
Tracking up to || = 3 Provide good position resolution for
vertexing Innermost layer at r = 2.6 cm Central region
6 barrels, 4 layers, axial + 2o/90o stereo12 cm long each, SS+DS
12 F-disks (SS) Forward region
4 H-disks (SS) 793k channels Radiation hard up to 1 Mrad >90% channels operational S:N > 10:1
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DPF 2002, Colonial Williamsburg, VA May 25, 20025
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Central Fiber Tracker0 p.e.
1 p.e.
2 p.e.
3 p.e.
CFT axial + stereo + SMT
d~42 m
pT > 3 GeV
Beam spot ~28 m
FPS
d
Tracking out to || = 1.7 Good momentum resolution
20 cm < r < 51 cm, 1.8 / 2.6 m fibers 8 double layers (axial, stereo 3o) 77,000 830m fibers readout with
VLPC Operate at 9 K, 85% Q.E., good S/N ~10 photons/m.i.p. get to the VLPC Impact parameter resolution ~42 m
for SMT+CFT tracks with pt > 3 GeV
No individual ladder or layer alignments yet
Beam spot size is about 28 m Trackers shifted in z by 2.9 cm w.r.t
calorimeter shifts zo
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Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Preshowers and Intercryostat Detector
Central and Forward Preshowers Central mounted on solenoid (|| < 1.2) Forward on calorimeter endcaps
(1.4 < || < 2.5) CPS: 7,680 FPS: 14,000 channels Extruded triangular scintillator strips
with embedded WLS fibers and Pb absorber Improve energy resolution measurements Trigger on low-pT EM showers Reduce overall electron trigger rate by x3-5 Same readout electronics as CFT
Intercryostat Detector (ICD) 384 scintillator tiles with WLS fiber to
phototubes in low-B field region for readout Improve coverage for the region 1.1 < || < 1.4 Improves jet ET and missing-ET
Readout through Calorimeter electronics LED pulsers used for PMT calibration Relative yields measured > 20 p.e./m.i.p.
ICD
FPS
CPS
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Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Calorimeter Overview
L. Ar in gap 2.3 mm
Ur absorber
Cu pad readout on 0.5 mm
G10 with resistive coat epoxy
Liquid argon sampling Stable, uniform response, rad. hard, fine spatial seg. LAr purity important
Uranium absorber (Cu (CC) or Steel (EC) for coarse hadronic) Compensating e/ 1, dense compact
Uniform, hermetic with full coverage < 4.2 ( 2o), int total)
Single particle energy resolution e: E / E = 15% /E+ 0.3% : E / E = 45% /E + 4%
Drift time 430 ns
South End CapSouth End CapNorth End CapNorth End Cap Central Cal.Central Cal.
50k readout cells (<0.1% bad) Fine segmentation,
5000 semi-projective towers (0.1x0.1) 4 EM layers, shower-max (EM3): 0.05 x 0.05 4/5 Hadronic (FH + CH)
L1/L2 fast Trigger readout 0.2x0.2 towers
ICD
EM
FH
CH OH
MH
IHEM
MG
FPS
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Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Calorimeter Electronics Calibration
Electronic readout “live” sampled energy in L.Ar. calibrated energy scale
Determine electronic calibration coefficients for absolute and channel-to-channel variations from pulser charge injection (DACADC)
Dual gain readout with analog storage in switched capacitor arrays (SCA)
Non-linear behavior of SCA chip observed for low energies ADC to GeV about 300 MeV underestimation
per cell Nonlinearity < 0.5% for cells > 1 GeV Has significant effect in low energy region
(jet widths and resolutions etc) Can apply universal parametrized correction for
all channels Residuals after correction are better than 5 ADC counts on the whole range for both gains
Correct energy in cells before clustering
In calibration, correct for signal shape difference with simulation
Also correct for cell-to-cell gain (ADC/DAC) dispersion (5 to 10%)
Apply intercalibration comparing slices in -- flat within 2% after correction
Improves both Zmass mean and resolution
Parameterized correction based onresiduals compared to linear fit
1 ADC ~ 4 MeV
ADC
8 1
pulser ADC readout
pulser shaper output
dual gain
ADC vs DAC
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DPF 2002, Colonial Williamsburg, VA May 25, 20029
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Jet Finding
22 ΔηΔR
Parton jet Parton hard scattering and parton
showers well described by pQCD
Higher cross-section expected in Run 2 for higher c.m.s s=1.96TeV x2 for pT > 400 GeV
Calorimeter jet Jet is collection of towers with a given cone R
Cone direction maximizes the total ET of the jet Various clustering algorithms
Particle jet After hadronization A spread of particles running roughly in the same direction as
the parton Correct for finite energy resolution Subtract underlying event (modeled by minimum bias data)
Jet inclusive pT spectrum
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DPF 2002, Colonial Williamsburg, VA May 25, 200210
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Run 2 Jet Algorithms Run 1 Legacy Cone
Draw a cone of fixed size around a seed Compute jet axis from ET-weighted
mean and jet ET from ET’s Draw a new cone around the new jet
axis and recalculate axis and new ET
Iterate until stable Algorithm is sensitive to soft radiation
Improved Run 2 cone Use 4-vectors instead of ET
Add additional midpoint seeds between pairs of close jets
Split/merge after stable protojets found Algorithm is infrared safe
kT-algorithm Recombination algorithm based on
relative momentum between ‘particles’ Theoretically favored, no split-merge To reduce computation time, start with
0.2 x 0.2 preclusters
Cell Nearest Neighbor Floor-by-floor clustering starting with EM3 Each local maximum starts a floor cluster then
add in neighbors Energy sharing according to transverse shape
parameterization Angular matching of floor clusters Search for minima in longitudinal energy
distribution to separate EM and hadronic showers
Energy Flow algorithm use tracking information to better characterize
the contributions from charged particles In development
Most results using simple cone for now
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Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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NADA NADA = New Anomalous Deposit
Algorithm Identify anomalous isolated energy
deposits in the calorimeter = “Hot Cells” Source: electronics, U noise,
beam splash, cosmics etc
Improve object resolution and MET Run 1: AIDA
Only examine neighbors in the same tower for Ecell > 10 GeV
99% efficient, BUT 5-10% misidentification rate
Not used for cells on boundaries of layers
FH1 and CH1 have more material
ETthresold
ETneighbour> 100 MeV or 0.02Ecell
Examine all cells with > 1 GeV Remove cells < -1 GeV & > 500 GeV ET < 5 GeV removed if no neighbor with
E > 100 MeV ET < 500 GeV removed if no neighbor
with E > 2% Ecell
High efficiency (90%) and low misidentification ET > 1 GeV : ~0.5% ET > 10 GeV : ~0%
On average about 0.8 cells / event
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DPF 2002, Colonial Williamsburg, VA May 25, 200212
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Jet Selection Central jets (Run 2 cone, R=0.7) Event Quality Cuts
Number of jets 1 Etotal in the calorimeter 2 TeV Missing ET 70% of the
leading jet pT
Zvtx < 50 cm Leading Jet Cuts
Jet pT > 8 GeV (offline cut) 0.05 EMF 0.95 CHF 0.4 (0.25 tight) HotF 10 (5 tight)
(HotF = ET1st cell / ET
2nd cell ) n90 > 1 (number of towers that
contain 90% of jet ET) Efficiencies from MC
Loose: ~100% Tight: ~ 98% ~Flat in eta
DØ Run 2 Preliminary
CHFEMF
n90HotF
Data
— MC
Non-linearity of SCA included in MC
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DPF 2002, Colonial Williamsburg, VA May 25, 200213
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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jet
Jet Energy Scale Correct Jet Energy back to the particle level
conejet
calojet
offsetmeasjetptcl
jet RR
EEE
Eoffset energy offset from underlying event, pile-up,
Uranium noise determined from Min. Bias Events
Rcalo calorimeter response Calibrate EM response on Zee mass peak Measure from ET balance in +jet events
Rcone energy contained in jet cone Correct for losses due to out-of-cone showering Use MC-energy in cones around the jet axis
Photon-jet Events
Preliminary correction being applied with ~10% systematic uncertainty
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DPF 2002, Colonial Williamsburg, VA May 25, 200214
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Central Jet Triggers
L1 single jet efficiencies Ask for one or two hadronic trigger towers (0.2x0.2)
above threshold Use muon trigger as unbiased reference for statistics to
measure turn-ons Ask for one and only one reconstructed jet in ||<0.7 L1 hadronic response about 40% low for current data set
L2 jet Cluster 3x3 or 5x5 trigger
towers around L1 seed towers
L3 jet Simple cone or tower NN
algo’s 0.1x0.1 towers 3 single jet triggers
(single tower): JT_LO L1: 5 GeV,
L3:10 GeV JT_HI L1:10 GeV,
L3:15 GeV CJT40: L1:40 GeV
Efficiency Standard jet selection,
offline pT > 8 GeV Very sharp turn on
All L1 trigger towers at || <0.8 are instrumented, complete coverage coming soon
L1 Trigger efficiency CJT(1,x) L1 Trigger efficiency CJT(2,x)
Efficiency vs jet pTCJT(1,3)CJT(1,5)CJT(1,7)CJT(1,10)
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DPF 2002, Colonial Williamsburg, VA May 25, 200215
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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First Run 2 QCD Physics
Central jets Not fully corrected distributions:
Preliminary correction for jet energy scale(but no unsmearing or resolution effects) 30-50% systematic error in cross-section
No trigger selection efficiency corrections
Highest 3-jet eventE
Tjet1 : 310 GeV
Etjet2 : 240 GeV
ET
jet3 : 110 GeV E
tmiss : 8 GeV
Only statistical errors
Inclusive jet pT spectrum at 1.96 TeV
Only statistical errors
Dijet mass spectrum at 1.96 TeV
Ldt = 1.9 ± 0.2 pb-1 Ldt = 1.9 ± 0.2 pb-1
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DPF 2002, Colonial Williamsburg, VA May 25, 200216
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Tuned on MC in bins of 0.1, < 3.2 for different energies
HMx8 / HMx9 / Hmx41 Energy fractions in each
floor (PS), EM1, EM2, EM3, EM4
, in EM3 grid (6,6)
log(Etot)
Z/z vertex
EM ID and Reconstruction Hmatrix
Measure compatibility of EM cluster with an electron shower 2
Discriminate against hadronic () decays that pass EM fraction and isolation cuts
Use longitudinal and transverse shower shapes to take into account correlations between energy in cells
Concentrate on high PT objects Look for
narrow isolated clusters with high EM fraction, track match for electrons, none for
Electron object reconstruction PTmin>1.5 GeV EM fraction > 0.9 Isolation
CC: 3x3 EM towers EC: All cells in cone of 20 cm radius
at EM3 around hottest channel Track match pT > 1.5, R<0.5
Preliminary fake rate calculated from 2nd unbiased jet passing standard EM selection in jet triggers 0.60.1% e
HM41 Run 1test beam+We
log2
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DPF 2002, Colonial Williamsburg, VA May 25, 200217
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Triggering on electrons L1 EM Trigger
Look for single EM trigger tower (0.2 x 0.2) over threshold
Scale calibrated ~10% No hadronic veto Use “bootstrap” method to
calculate efficiencies
L2 EM Trigger Use 3x3 NN algorithm with 1 GeV seed
L3 EM Trigger To measure the trigger efficiency,
select good EM objects: EM frac > 0.9, isolation < 0.2,
HM41 < 200, || < 0.8 L3EM(1,15,emfr) rejection 5.1 Add shower shape can drop energy
thresholdL3EM(1,12,emfr,shape) rejection 4.2
L1 TT vs Offline
L1 Trigger effic.CEM(1,x)
L3 Trigger effic. L3EM(1,15) L3EM(1,12,shape) L3EM(2,10)
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DPF 2002, Colonial Williamsburg, VA May 25, 200218
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Reconstructed EM profiles
EM4EM3
EM2EM1
Energy Fractions pT>20 GeV from EM_HI trigger— QCD MC
EM1 EM2
EM3 EM4
Energy Fractions good EM candidates that reconstruct to Z mass— Zee MC
Efficiency vs.
Efficiency from 2nd e in Zee sample (pT>20GeV, with track match) HMx9 < 100 : 94%
HMx9 < 25 : 82%
DØ Run 2 Preliminary
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DPF 2002, Colonial Williamsburg, VA May 25, 200219
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Energy Scale from Z ee
CC+EC
Not applied phi-intercalibration, pulser corrections etc. so calculate energy correction for each cryostat region to restore Z-peak to its expected value Gives correction < few %
Work underway to add tracking information, calibration for individual cryostat quadrants
Compare data and Zee MC Mass distributions to get absolute energy scale
Use standard EM selection with geometrical corrections (phi cracks, eta dependence etc) 2 EM objects, ET > 20 GeV isolation < 0.1 0.95 < EM fraction HMx8 < 100
Paramaterize Etrue = E(1 + ) Fit for Z mass with Breit-Wigner
and find which maximizes a likelihood
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DPF 2002, Colonial Williamsburg, VA May 25, 200220
Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Check Energy Scale with W e
EM clusterwith SMT track
em objects with track match el-id criteria
W selection
EM Object ET>25 GeV in || < 0.8 -0.05 < isolation < 0.1 0.95 < emf < 1.05 HM8<50, HM41<200
MET > 25 GeV
Search for cluster-global track match in EM sample (scale corrected)
Global tracks 10 < Nhits < 16 pT > 5 GeV
Track to EM cluster match < 0.05, < 0.2
E/p ~ 1
Fit the electron p spectrum
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Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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Summary Tevatron Run 2 well underway DØ detector performing extremely well but many new systems coming online
Complete readout and integration of tracking and preshowers L1: extend coverage in eta; track triggers L2: calorimeter and track triggers New EM/jet algorithms (e.g. did not discuss identification of softer electrons in
jets, especially useful for semileptonic b-decays – use road method)
Expect rich physics program from large statistics for high pT events Improve knowledge of QCD, proton structure functions Measurements of heavy flavor and Electroweak physics Searches for new phenomena, quark compositeness, extra dimensions, W’, Z’… The elusive Higgs boson
D0 detector poised to take full advantage of the higher instantaneous and integrated luminosities
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Leslie GroerColumbia University Jet and Electron Identification in the Run 2 DØ Detector
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EM geometric corrections and resolution
EM Geometric Correction Energy corrections for
geometric effects (e.g. phi cracks, eta dependence due to dead material in front of calorimeters)
Single electron MC EM Resolution
Single electron MC Calorimeter info only (no
preshower) Correcting for phi cracks
and eta correction Calculate from cluster position in EM3
Eta correction factor
)002.0004.0(
1)006.0202.0(
2/1)10.023.0(/)(
E
EEEsampling
noise
constant
EM resolution
E (GeV)
Eta correctionfactor
5 GeV electrons
E (GeV)