alexander kup co for the d˜ collaboration · calor’04, perugia march 29 - april 2, 2004...

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CALOR’04, Perugia

March 29 - April 2, 2004

Alexander Kupco

for the DØ collaboration

CEA Saclay, France

visitor from Institute of Physics, Academy of Sciences of the Czech Republic

Run II upgrade of the DØ detector

Tracking SystemTracking System: Silicon, Fiber Tracker,: Silicon, Fiber Tracker,Solenoid, Central & ForwardSolenoid, Central & Forward Preshowers Preshowers

ShieldingShielding

Fiber Tracker/Fiber Tracker/Preshower Preshower VLPC Readout SystemVLPC Readout System

NN SSMuon ToroidMuon Toroid

Muon Muon ScintillationScintillationCountersCountersForward Mini-Forward Mini-

Drift TubesDrift Tubes

PDTsPDTs

PlatformPlatform

CCCC

ECEC ECEC

Alexander Kupco, CEA Saclay, France CALOR’04, Perugia page 2

Calorimeter

DO LIQUID ARGON CALORIMETER

1m

CENTRAL CALORIMETER

END CALORIMETER

Outer Hadronic (Coarse)

Middle Hadronic (Fine & Coarse)

Inner Hadronic (Fine & Coarse)

Electromagnetic

Coarse Hadronic

Fine Hadronic

Electromagnetic

� uniform and hermetic

- coverage up to � η � < 4.2

� nearly compensating

� fine segmentation

- ∆η � ∆ϕ = 0.1 � 0.1

(3rd EM layer: 0.05 � 0.05)

� particle energy resolution

e : σE = 15%√

E

� 0.3%

π : σE = 45%√

E

� 4%

� ��

- shorter time between bunch crossings (396 ns) � faster trigger and readout electronics

- more material in front of calorimeter (magnet, new tracker) � new preshower detector


Jets

q

Tim

e

p p

q g

K

“part

on

jet”

“part

icle

jet

”“ca

lori

met

er j

et”

hadrons

CH

FH

EM

. calorimeter jet- calorimeter - main tool for jet measurement

- jet is a collection of towers

- geometrical definition (cone algorithms)

- pQCD motivated algorithms (kT )

. particle jet- after hadronization

- a spread of particles running roughly in thesame direction as the parton

. parton jet- parton hard scattering

- parton showers


Run II cone algorithm

. a collection of towers within a given cone R =√

∆2ϕ + ∆2η

- ϕ is the azimuthal angle

- pseudorapidity η is related to the polar angle ϑ : η = � log tan (ϑ/2)

. recombination scheme - E-scheme

Ejet =∑

towers

Ei , ~pjet =∑

towers

~pi

. cone axis - stable directions

- iterative procedure starts only fromseeds above some threshold

- using midpoints as an additional start-ing seeds

. splitting and merging overlapping jets

. accept only jets with ET > 8 GeV

eta

-4.7 -3

-2 -1

0 1

2 3

4.7

phi180

0

360

ET(GeV)

385

Bins: 481Mean: 2.32Rms: 23.9Min: 0.00933Max: 384

mE_t: 72.1phi_t: 223 deg

Run 178796 Event 67972991 Fri Feb 27 08:34:03 2004


Jet energy scale

correction of the jet energy measured on the detector level to the jetenergy on the particle level

Ejetptcl =

Ejetdet

� �

Rjet S

�� ( � ) - energy not associated with the hard interaction (U noise,pile-up from previous crossings, additional pp interactions)

� � � �� (Rjet)

- calorimeter response to the jet

- EM part calibrated on Z � ee mass peak

- measured from ET balance in γ + jet events

� � �� (S) - losses due to showering the energy in the calorimeterout of the jet cone


Offset - ( � � � cone)�� ( � ) - energy not associated with the hard interaction (U noise,

pile-up from previous crossings, additional pp interactions)

|ηDetector |0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

)φ×η∆(G

eV/

TE

D

0.2

0.4

0.6

0.8

1

1.2

1.4

|ηDetector |0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

)φ×η∆(G

eV/

TE

D

0.2

0.4

0.6

0.8

1

1.2

1.4

L = 32.5E30

L = 19.5E30

L = 11.5E30

� average tower ET density

� ET=

∑

φ ET (η)

2π ∆η Nevents

� � ETmeasured in two dif-

ferent samples

- zero bias (accelerator clock)

- minimum bias (inelastic scat-

tering)

� offset for R = 0.7 cone is about 1 GeV


Jet response� deposited energy is different from the measured one

- calorimeter is not perfectly compensated : eπ

� 1.05 for E > 30 GeV

- dead material, module-to-module fluctuations, . . .

Missing ET projection method

- jet response determined fromthe pT imbalance in γ+jet events

~ETγ + ~ETrecoil = 0 (ideal)

Rγ~ETγ + Rrecoil

~ETrecoil = � ~ET� (real)

- after EM energy calibration from the

Z � ee mass peak (Rγ = 1)

Rrecoil = 1 +~nTγ · ~ET6

ETγ

- select nice, back-to-back, γ+jet events

Rjet = Rrecoil


EM scale

Di-Electron Mass (GeV)0 20 40 60 80 100 120

Eve

nts

/ 2

GeV

0

20

40

60

80

100

Number of Entries: 604

Peak Mass: 90.8 +- 0.2 GeV

Width: 3.6 +- 0.2 GeV

D0 Run II Preliminary

� determined from Z � e+e−

mass peak

� typical size of EM scale is between 1-5%


Response in central and forward cryostats

E’ [GeV]10 210

jet

R

0.65

0.7

0.75

0.8

0.85

0.9

CC

ECS

ECN

= 0.7coneR

Events are placed in various E ′ bins

E′ = ETγ cosh(ηjet)

- photon energy and jet direction are well

measured quantities

- smearing effects are minimazed

CC - jet in the central cryostat

ECS - jet in the south end-cap

ECN - jet in the north end-cap

� different response in cryostats � cryostat factors


Response

[GeV]detE10 210

jet

R

0.6

0.65

0.7

0.75

0.8

0.85

0.9

det log E1 + p0 p 0.013± = 0.425 0p 0.004± = 0.082 1p

= 0.7coneR

0.006± = 0.916 ECSFcr

0.007± = 0.948 ECNFcr

� mapping from E ′ to measuredjet energies Edet

� statistical error

< 1% for 20 � 250 GeV

� systematic error

� 4 � 5% for 20 � 250 GeV- variation of selection cuts

- closure tests on MC and different

data samples (Z + jet)

� for jets in the end-caps, corresponding cryostat factor is applied

� special treatment in the inter-cryostat region (ICR)


Response in ICR

Detector Eta0 0.5 1 1.5 2 2.5 3

Detector Eta0 0.5 1 1.5 2 2.5 3

Res

po

nse

/Fit

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

1.1 Data Response/Fit

15 < E_T < 22.5

22.5 < E_T <30.0

E_T > 30.0

Data Response/Fit

� η dependence studied in γ+jetevents

� expect log-linear dependence inuniform detector

Rjet(η) = a + b log[cosh(η)]

ICR correction

- obtained from the response deviation from the log-linear dependence

- applied in the region 0.5 < � η � < 1.5


Showering -(

� � cone

)

� � �� (S) - losses due to showering the energy in the calorimeterout of the jet cone

Method

- study energy flow as a function ofdistance from the jet axis

r =√

(η � ηjet)2 + (φ � φjet)2

R = 0.7 R = 0.5

Central 0.99 0.92

ICR 0.96 0.89

Forward 0.94 0.85

� 5% systematic error


Overall jet energy correction

(GeV)uncorrE50 100 150 200 250 300 350 400 450 500

(GeV)uncorrE50 100 150 200 250 300 350 400 450 500

0.6

0.8

1

1.2

1.4

1.6

1.8

2

=0jet

η=0.7, coneR

Correction vs. E

(GeV)uncorrE50 100 150 200 250 300 350 400 450 500

(GeV)uncorrE50 100 150 200 250 300 350 400 450 500

0

0.05

0.1

0.15

0.2

0.25

0.3

total error

Stat. error

Correction error vs. E

|η|0 0.5 1 1.5 2 2.5

|η|0 0.5 1 1.5 2 2.5

0.8

1

1.2

1.4

1.6

1.8

2

=50 GeV uncorr

jet=0.7, EconeR

|ηCorrection vs. |

|η|0 0.5 1 1.5 2 2.5

|η|0 0.5 1 1.5 2 2.5

0

0.05

0.1

0.15

0.2

0.25

0.3

total error

Stat. error

|ηCorrection error vs. |


Jet T resolution

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

< 100 GeVT 80 GeV < p

A� dijet events for E > 50 GeV

- select nice back-to-back dijet events

- pT asymmetry

� = � pT1

� pT2 �

pT1 + pT2

is directly related to pT resolution

σpT

pT= 2σA

- corrected for the soft radiation (additional jets below the 8 GeV recon-struction cut) and for jet imbalance on hadron level


Jet T resolution

)/2 [GeV]T2 + pT1(p0 50 100 150 200 250 300

0

0.05

0.1

0.15

0.2

0.25

0.3

T)/pT(pσ | < 0.5 (R=0.7) η |T)/pT(pσ

)/2 [GeV]T2 + pT1(p0 50 100 150 200 250 300

0

0.05

0.1

0.15

0.2

0.25

0.3

T)/pT(pσ| < 2. (R=0.7) η 1.5 < |T)/pT(pσ

σpT

pT=

√

√

√

√

N2

p2T

+S2

pT+ C2

N - noise term

S - sampling term

C - constant term

� larger value of resolution than in Run I� reason is being investigated now

- more dead material, larger noise

� we are working currently on deter-mination of jet response from γ+jetsample


Summary� Calibrating jet energies and understanding jet energy resolutions are es-

sential parts of the DØ Run II program and is needed by most physicsanalyses

� Although in Run II, the calorimeter is the same as in Run I, jet energyscale and resolutions need to be derived from the very beginning due tonew electronics and more dead material.

� Run II jet energy scale has been derived for data and MC for two differentcones, R = 0.5 , 0.7- currently, the error is 7% in data for central jets in the 30 � 250GeV region

- the goal is to reach the understanding of the scale on the level of 2-3%

� Run II resolutions larger than in Run I- improvements are expected from advanced algorithms combining different subdetector

information

� In future we expect further progress using: Z � bb, W � qq in tt events


alexander kup co for the d˜ collaboration · calor’04, perugia march 29 - april 2, 2004...

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