Prompt Photons + Jets in DIS - ppe › ~bussey › prph › DIS11 › 01_pr_photons_jets… · 1200...

Outline Data and MC samples Event Selection Cuts Control Plot fmax , δz fits Differential cross sections 1st and 2nd analysis Summary Preliminary Preliminary Preliminary Appendix

Prompt Photons + Jets in DIS

Peter Bussey, David Saxon, Ian Skillicorn,Oleg Kuprash, Nataliia Zhmak

(Glasgow / DESY / Kiev National University)

05. April 2011PCOOR meeting

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Outline

Data and MC samples

Event selection cuts

Q2 reweighting procedure redone !

Control plot

fmax, δz fits

Differential cross sections

1st and 2nd analysis comparison

Summary

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DIS ep collision

• Prompt photons are high transverse energy final state photons which areemitted directly during the hard scattering process• Prompt photons do not undergo the hadronization process, thereforetheoretical calculations can be done with better precision• The final state photon is a particle which arrives in the detector afterparticipating in the actual hard scattering process and so it can provide directinformation of the process and the proton structure• Must take account of ISR reffered as LL-diagrams

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Used Data and MC samples

Data040506e, 0607pR

Ldt = 332 pb−1

MCPYTHIA (signal)

ARIADNE (background)

NotationsLL = photons from leptons

QQ = photons from quarks

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Event Selection CutsPhase Space

10 < Q2 < 350GeV2

Cleaning Cuts−40 < Zvtx/cm < 4035 GeV < E− pz < 65 GeV

Electron CutsSiecorr > 10 GeV

140◦ < θel < 180◦

−14.8 < ex/cm < 14.8−14.6 < ey/cm < 12.5

TriggersSPP02 trigger for 0405e

SPP09 trigger for 06e, 0607p

Prompt Photon Phase Space4 < ET,γ/GeV < 15

−0.7 < ηγ < 0.9

Prompt Photon Cleaning Cuts∆r < 0.2

EEMCEHAC+EEMC

> 0.9

EγEjet containing γ

> 0.9

fmax > 0.05

Jet Selectionbased on zufos

EcorrT,jet > 2.5GeV

−1.5 < ηjet < 1.8take highest ET,jet jet within η range inthe event 5/40


Q2-reweighting• Q2-reweighting procedure has been improved since last meeting. Insteadof reweighting MC after inclusive DIS selection to inclusive DIS Data:• Split data events after full event selection into two parts: with δZ > 0.35(more background events) and with δZ < 0.35 (more signal events)

• reweight non-radiative Ariadne background to the part of data withδZ > 0.35• reweight signal Pythia MC to the part with δZ < 0.35• do not reweight LL Ariadne at all, since it is well theoretically understood

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Q2-reweighting

• Left four plots are before reweighting• Right four plots are after reweighting• Linear fit for Pythia and polynomial of order two for Ariadne• Compared hadronic level of MC with Data corrected for acceptance effects• Data and MC summed over periods

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Q2-reweighting

• Control plots before Q2-reweighting

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Q2-reweighting

• Control plots after Q2-reweighting: better description of Data by MC for Q2and x

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Cross-section comparison with/without Q2 reweighting(1/2)

• Discrepancy is typically less then 1%

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Cross-section comparison with/without Q2 reweighting(1/2)

• Influence on Q2 cross-section is tiny

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Control Plot

)2 (GeV2Q0 50 100150200250300350

Eve

nts

0200400600800

100012001400160018002000

)2 (GeV2Q0 50 100150200250300350

Eve

nts

0200400600800

100012001400160018002000

x0.005 0.01 0.015 0.02

Eve

nts

0

500

1000

1500

2000

2500

3000

x0.005 0.01 0.015 0.02

Eve

nts

0

500

1000

1500

2000

2500

3000

(cm)vtxZ-40 -20 0 20 40

Eve

nts

0

200

400

600

800

1000

1200

(cm)vtxZ-40 -20 0 20 40

Eve

nts

0

200

400

600

800

1000

1200

(GeV)γT,E4 6 8 10 12 14 16

Eve

nts

0

500

1000

1500

2000

2500

(GeV)γT,E4 6 8 10 12 14 16

Eve

nts

0

500

1000

1500

2000

2500

(GeV)T,jetE5 10 15 20 25 30 35

Eve

nts

0

200

400

600

800

1000

1200

1400

1600

(GeV)T,jetE5 10 15 20 25 30 35

Eve

nts

0

200

400

600

800

1000

1200

1400

1600-1ZEUS (prel.) 332 pb

LL MC

QQ MC

LL + QQ + Hadronic MC

• Q2-reweighting has been applied here and on the further plots

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fmax, δz definition

>maxmax∆<0 0.2 0.4 0.6 0.8 1 1.2 1.4

Eve

nts

0

200

400

600

800

1000

1200

ZEUS

-1ZEUS (prel.) 332 pb

LL MC

QQ MC


Z>∆<0 0.2 0.4 0.6 0.8 1 1.2 1.4

Eve

nts

0

200

400

600

800

1000

1200

• fmax - ratio of the energy in the highest energy cell of a cluster to the totalenergy of a cluster• δz - energy weighted mean width of the electromagnetic cluster in Zdirection:

δz =P

i |Zi−Zcluster|∗EiWcell

Pi Ei

• The δz distribution has the more detailed structure and was chosen todefine the prompt photon fraction in Data, as in the previous analysis• LL = predicted value of lepton high-energy radiation• QQ = predicted value of prompt photons

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fmax , δz fits

fits: δz/Et

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fmax , δz fits

fits: fmax/Et

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Differential cross sections

(GeV)γTE4 6 8 10 12 14

(pb/

GeV

)γ T

/dE

σd

0.5

1

1.5

2

2.5


LL MC

QQ(x1.6) MC

LL + QQ(x1.6) MC

ZEUS

)2 (GeV2Q20 30 40 50 210 210×2

)2 (p

b/G

eV2

/dQ

σd

-310

-210

-110

-1ZEUS (prel.) 332 pbLL MCQQ(x1.6) MCLL + QQ(x1.6) MC

ZEUS

γη-0.5 0 0.5

(pb)

γ η/dσd

2

4

6

8

10

12

14 -1ZEUS (prel.) 332 pbLL MC

QQ(x1.6) MC

LL + QQ(x1.6) MC

ZEUS

x-310 -210

/dx

(pb)

σd

10

210

310


ZEUS

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Cross sections as functions of jet variables

, GeVjetTE

10 20 30

(pb/

GeV

)je

tT

/dE

σd

-210

-110

1


ZEUS

(GeV)jetT

E-1 0 1

(pb)

jet

η/dσd

1

2

3

4

5

6

7


LL MCQQ(x1.6) MCLL + QQ(x1.6) MC

ZEUS

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Comparison of 1st and 2nd analysis, 0405e (1/3)

photonη

-0.5 0 0.5

(pb)

phot

onη

/d

σd

2

4

6

8

10

1st analysis

2nd analysis

photonη-0.5 0 0.5

rel.

diffe

renc

e

-0.4-0.2

00.20.4

)2 (GeV2Q210

)2 (p

b/G

eV2

/d Q

σd

-310

-210

-110

1

1st analysis

2nd analysis

)2 (GeV2Q210

rel.

diffe

renc

e

-0.5

0

0.5

• Distributions of selected events with photon + jet are compared• Agreement in 1st and 2nd analysis is excellent

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(GeV)photonTE4 6 8 10 12 14

(pb/

GeV

)ph

oton

T/d

Eσd

1

2

3

4

1st analysis2nd analysis

(GeV)photonTE4 6 8 10 12 14

rel.

diffe

renc

e

-0.4-0.2

00.20.4

Bjx-310 -210

(pb)

Bj/d

xσd

210

310

410

1st analysis

2nd analysis

Bjx-310 -210

rel.

diffe

renc

e

-0.5

0

0.5

• Distributions of selected events with photon + jet are compared• Perfect agreement of 1st and 2nd analysis

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T, jetE4 6 8 10 12 14

(pb/

GeV

)T,

jet

/d E

σd

-110

1

1st analysis2nd analysis

T, jetE4 6 8 10 12 14

rel.

diffe

renc

e

-0.4

-0.2

0

0.2

0.4

jetη

-1.5 -1 -0.5 0 0.5 1 1.5

(pb)

jet

η/d

σd

1

2

3

4

5

6

7

1st analysis

2nd analysis

jetη-1.5 -1 -0.5 0 0.5 1 1.5

rel.

diffe

renc

e

-0.4

-0.2

0

0.2

0.4

• Distributions of selected events with photon + jet are compared• Agreement in 1st and 2nd analysis is excellent

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Summary

Differential cross sections for prompt photon + jetsproduction have been measured.

We are waiting for promised theoretical predictions.

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These plots to be made preliminary

(GeV)γTE4 6 8 10 12 14

(pb/

GeV

)γ T

/dE

σd

0.5

1

1.5

2

2.5


LL MC

QQ(x1.6) MC

LL + QQ(x1.6) MC

ZEUS

)2 (GeV2Q20 30 40 50 210 210×2

)2 (p

b/G

eV2

/dQ

σd

-310

-210

-110


ZEUS

γη-0.5 0 0.5

(pb)

γ η/dσd

2

4

6

8

10

12

14 -1ZEUS (prel.) 332 pbLL MC

QQ(x1.6) MC

LL + QQ(x1.6) MC

ZEUS

x-310 -210

/dx

(pb)

σd

10

210

310


ZEUS

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, GeVjetTE

10 20 30

(pb/

GeV

)je

tT

/dE

σd

-210

-110

1


ZEUS

(GeV)jetT

E-1 0 1

(pb)

jet

η/dσd

1

2

3

4

5

6

7


LL MCQQ(x1.6) MCLL + QQ(x1.6) MC

ZEUS

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)2 (GeV2Q0 50 100150200250300350

Eve

nts

0200400600800

100012001400160018002000

)2 (GeV2Q0 50 100150200250300350

Eve

nts

0200400600800

100012001400160018002000

x0.005 0.01 0.015 0.02

Eve

nts

0

500

1000

1500

2000

2500

3000

x0.005 0.01 0.015 0.02

Eve

nts

0

500

1000

1500

2000

2500

3000

(cm)vtxZ-40 -20 0 20 40

Eve

nts

0

200

400

600

800

1000

1200

(cm)vtxZ-40 -20 0 20 40

Eve

nts

0

200

400

600

800

1000

1200

(GeV)γT,E4 6 8 10 12 14 16

Eve

nts

0

500

1000

1500

2000

2500

(GeV)γT,E4 6 8 10 12 14 16

Eve

nts

0

500

1000

1500

2000

2500

(GeV)T,jetE5 10 15 20 25 30 35

Eve

nts

0

200

400

600

800

1000

1200

1400

1600

(GeV)T,jetE5 10 15 20 25 30 35

Eve

nts

0

200

400

600

800

1000

1200

1400


LL MC

QQ MC


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>maxmax∆<0 0.2 0.4 0.6 0.8 1 1.2 1.4

Eve

nts

0

200

400

600

800

1000

1200

ZEUS

-1ZEUS (prel.) 332 pb

LL MC

QQ MC


Z>∆<0 0.2 0.4 0.6 0.8 1 1.2 1.4

Eve

nts

0

200

400

600

800

1000

1200

25/40


fmax , δz fits

These plots to be made preliminary, fits: δz/Et

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fmax , δz fits

These plots to be made preliminary, fits: fmax/Et

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fmax , δz fits

These plots to be made preliminary, fits: δz/Q2

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fmax , δz fits

These plots to be made preliminary, fits: fmax/Q2

29/40


fmax , δz fits

These plots to be made preliminary, fits: δz/η

30/40


fmax , δz fits

These plots to be made preliminary, fits: fmax/η

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fmax , δz fits

These plots to be made preliminary, fits: δz/x

32/40


fmax , δz fits

These plots to be made preliminary, fits: fmax/x

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fmax , δz fits

These plots to be made preliminary, fits: δz/ET,jet

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fmax , δz fits

These plots to be made preliminary, fits: fmax/ET,jet

35/40


fmax , δz fits

These plots to be made preliminary, fits: δz/ηjet

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fmax , δz fits

These plots to be made preliminary, fits: fmax/ηjet

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Stretch calibration: description (from M.Forrest’s PHDthesis)

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Stretch calibration (from M.Forrest’s PHD thesis)

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Stretch calibration: result

• Better fit of Data distributions after applying stretch calibration

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OutlineData and MC samplesCutsControl Plotfmax, z fitsfmax, z fits

Differential cross sections1st and 2nd analysisSummaryPreliminaryPreliminaryPreliminaryfmax, z fitsfmax, z fits

Appendix

Prompt Photons + Jets in DIS - ppe › ~bussey › prph › DIS11 › 01_pr_photons_jets… · 1200...

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Transcript of Prompt Photons + Jets in DIS - ppe › ~bussey › prph › DIS11 › 01_pr_photons_jets… · 1200...