Interjet Energy Flow

Interjet Energy Flow . Patrick Ryan, Univ. of Wisconsin QCD Meeting , April 7, 2005 - 1

Patrick Ryan University of Wisconsin

Claire GwenlanOxford University

April 18, 2005

Interjet Energy FlowInterjet Energy FlowInterjet Energy FlowInterjet Energy Flow

Monday Meeting

http://www-zeus.desy.de/~pryan/rap_gap

Rapidity Gaps. Patrick Ryan. Univ. of Wisconsin Collaboration Meeting , Oct.. 15, 2003 - 2

Hard Diffractive Hard Diffractive ppHard Diffractive Hard Diffractive pp

• Use pQCD to study diffraction• Hard Diffractive Photoproduction

• Hard: High ET Jets (ET > 5 GeV)• Diffractive: Gap between jets • Photoproduction: Q2 ~ 0

t

q

Standard DiffractionHard Diffractive p

Rapidity Gap


Topology of Rapidity GapsTopology of Rapidity GapsTopology of Rapidity GapsTopology of Rapidity Gaps

Distance between jet centers: •ET

Gap = Total ET between leading and trailing jets

•Gap Event: ETGap < ET

Cut

•Gap indicates color singlet exchange

Jet

Jet

Gap

Remnant

p Remnant0

2

-2.4 2.4

Trailing

LeadingLeading Jet

Trailing Jet

Remnant

-3

3

0

2


The Gap FractionThe Gap FractionThe Gap FractionThe Gap Fraction

Expectation for Behavior of Gap Fraction (J.D. Bjorken, V.Del Durca, W.-K. Tung)*

2 3 4

fGap

fGapSinglet fGap

n-s

dd

ddf Gap

/

/)(

Singletgap

SingletNongapGap

All Dijet Events with large Rapidity separationDijet Events with large Rapidity separation and ET

Gap < ETCut

•Non-Singlet• f() decreases exponentially with • Particle production fluctuations Gap• Non diffractive exchange

•Singlet• f() constant in

*Phys. Rev. D47 (1992) 101

Phys Lett. B312 (1993) 225


Simulation of Simulation of p Eventsp EventsZEUS - AMADEUSZEUS - AMADEUS

Simulation of Simulation of p Eventsp EventsZEUS - AMADEUSZEUS - AMADEUS

• PYTHIA 6.1 and HERWIG 6.1 MC

• Direct and Resolved MC generated separately• Resolved MC includes Multi Parton Interactions

• Dir and Res combined by fitting xdistributions to data (next slide)

• PDFs• PDF(p): GRV-LO

• PDF(): WHIT 2

• Color Singlet Exchange MC• PYTHIA: High-t

• Purpose is simply to match the data

• Note: Rapidity Gap not due to photon exchange

• HERWIG: BFKL

• Uses BFKL Pomeron as exchange object in Rapidity Gap events


Event Selection and xEvent Selection and x Fitting FittingZEUS - AMADEUSZEUS - AMADEUS

Event Selection and xEvent Selection and x Fitting FittingZEUS - AMADEUSZEUS - AMADEUS

•ZEUS 96-97 Data• Luminosity: 38 pb-1

•Offline Cleaning Cuts• |zvtx| < 40 cm• No Sinistra95 e+ with

• Pe > 0.9, Ee > 5 GeV, ye < 0.85• 0.2 < yjb < 0.85

•Jet Selection• ET

1,2 > 5.1, 4.25 GeV (ZUFO)• || < 2.4• ½|| < 0.75• [(px)2 + (py)2] / ET < 2 GeV1/2 • 2.5 < || < 4.0

•4 Gap Samples• ET

CUT = 0.6, 1.2 1.8, 2.4 GeV (ZUFO)

•HPP Trigger• FLT Slot 42• SLT HiEt I/II/III• TLT HPP14 (DST bit 77)

•~70,000 Inclusive Events

Direct

Direct + Resolved

PYTHIA x Fit to Data

PYTHIA: 38% Direct + 61% Resolved HERWIG: 54% Direct + 46% Resolved

Mixing used in all calculations


Simulation of Simulation of p Datap DataZEUS - AMADEUSZEUS - AMADEUS

Simulation of Simulation of p Datap DataZEUS - AMADEUSZEUS - AMADEUS

PYTHIA HERWIG

Data well simulated by MC


Simulation of Gap Energy using Simulation of Gap Energy using ZEUS - AMADEUSZEUS - AMADEUS

Simulation of Gap Energy using Simulation of Gap Energy using ZEUS - AMADEUSZEUS - AMADEUS

•HERWIG does not describe Gap Energy

• Standard ZEUS HERWIG

• Proton PDF: GRV 5

• Photon PDF: WHIT 2

• pTMin = 1.8 GeV

•pTMin: Min pT of all

scatters in hadronic jet production

•Add CS until a reasonable match with data


EETT Gap GapAvg Corr. and HZTOOL TuningAvg Corr. and HZTOOL Tuning

EETT Gap GapAvg Corr. and HZTOOL TuningAvg Corr. and HZTOOL Tuning

Corr. w/ AMADEUS PYT/HER Corr. w/ AVG AMADEUS vs. HZTOOL HERWIG

•HZTOOL HERWIG• pT

Min = 3.0 GeV• pPDF: CTEQ5L PDF: SaS 2D


SystematicsSystematicsSystematicsSystematics

•Order of Variables• +/- 1: ET

1,ET2,1,2, ½||,,YJB,pT/ET

1/2,ye,Zvtx,ETCut

• +/- 3%: ET and YJB (Cal Energy Scale)

PYTHIA HERWIG


Comparisons between AnalysesComparisons between AnalysesComparisons between AnalysesComparisons between Analyses

•Agreement between the analyses

PR: PYTHIA CG: PYTHIA

PR: AVERAGE CG: PYTHIA


Request PreliminaryRequest PreliminaryRequest PreliminaryRequest Preliminary


Summary on Summary on p with Rap Gapp with Rap GapSummary on Summary on p with Rap Gapp with Rap Gap

• Conclusions• HERWIG + BFKL and PYTHIA + High-t describe data

• Evidence for Color Singlet Exchange

• Good Agreement between analyses (P.R & C.G)


Simulation of ESimulation of ETTGapGapSimulation of ESimulation of ETTGapGap

PYTHIA HERWIG

•Data not described by MC


Inclusive and Gap Cross SectionsInclusive and Gap Cross SectionsInclusive and Gap Cross SectionsInclusive and Gap Cross Sections

Gap

Error bars show stat + sys errors

dd

ddf Gap

/

/)(

Ratio of above plots

Inclusive

Gap Fraction:

Compare p Data to HERWIG


Gap Fractions for Different Gap EGap Fractions for Different Gap ETTGap Fractions for Different Gap EGap Fractions for Different Gap ETT

•Observed excess of Data over MC without CS exchange

•Data has better agreement for MC than without CS

•Suggests presence of CS exchange

dd

ddf Gap

/

/)(


Previous PreliminaryPrevious PreliminaryPrevious PreliminaryPrevious Preliminary

•Preliminary for ICHEP 2002• Very old• Different binning• Different from CG thesis

Preliminary: ●

CG ThesisPoints ●


Possible PreliminaryPossible PreliminaryPossible PreliminaryPossible Preliminary

Interjet Energy Flow

Documents

Transcript of Interjet Energy Flow