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

1

Leslie GroerColumbia University, New York


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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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)

dpf 2002, colonial williamsburg, va may 25, 2002 1 leslie groer columbia universityjet and electron...

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