Isabell-A. Melzer-Pellmann Moriond QCD, 28.3.-4.4.2004

H1 and ZEUS H1 and ZEUS RResults esults on on BBeauty eauty PProduction    roduction   

Isabell-Alissandra Melzer-PellmannIsabell-Alissandra Melzer-PellmannDESY Hamburg, ZEUSDESY Hamburg, ZEUS

XXXIXthXXXIXth Rencontres de Moriond Rencontres de MoriondQCD QCD andand HighHigh E Energynergy H Hadronicadronic InteractionsInteractions

March 28th March 28th --April 4th, 2004April 4th, 2004

2Isabell-A. Melzer-Pellmann Moriond QCD, 28.3.-4.4.2004

Outline

• Introduction and Theory• Measurement techniques

and Results (P and DIS)- Jets + - D* correlations

• Summary and Outlook

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Introduction: HERA

p

e

Maximum centre of mass energies: s = 300 GeV (1992-1997) s = 318 GeV (1998-2000)

Luminosity (1996-2000):e+p scattering: L 100 pb-1

e-p scattering: L 15 pb-1

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Theory:Beauty production at

HERA Driven by gluons in the proton Kinematic regions dependent on the virtuality of the photon Q2:

Photoproduction (P): Q2 < 1GeV2

Hard scales: mb, pT

Deep inelastic scattering (DIS): Q2 > 1GeV2

Hard scales: mb, Q2, pTb

b

Always more than one hard scale for s available perturbative QCD should work…

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Theory:Description in pQCD

Factorisation: Photon structure Matrix element Proton structure

Photon structure:

Role of resolved photonsin beauty production?

Proton structure:Test pQCD approximationfor gluon radiations:DGLAP, BFKL,CCFM

Hard ME

QCD modelscompared to data: LO O(s) + parton shower:

o Pythia MC (DGLAP)o Cascade MC (CCFM)

NLO O(s2) :

o P: FMNRo DIS: HVQDIS

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Measurement technique:B -> jjX

Large B mass: pT of relative to the closest Jet is larger

Large B lifetime: impact parameter

H1 P (prel.): Combined max Likelihood fit (, pT ): fb=30.72.5 %rel

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Results: B -> jjX in

Photoproduction

NLO is in good agreement with data H1 slightly higher than ZEUS (agreement within errors)

Pseudorapidity

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P: Comparison of NLO QCD and LO+PS

NLO QCD as well as LO + Parton shower MC describe the data reasonably well (MC below data for high and high pT)

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P: Comparison NLO QCD and LO+PS for xjets

tool to measure photon-gluonfusion (peak at x1) incomparison to other contributions (e.g. gluon-gluon fusion or higher order diagrams (photon structure, distributed over the whole range)

jets

NLO QCD: good description of dataPythia: good description (large contribution from flavour excitation at low x )Cascade: underestimates data at low x (generation of these events via

initial state radiation without using a parton density in the photon)

jets

jets

Allz

Jetz

jets

pE

pEx 2,1

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Results: B -> jX in DIS

ZEUS : ep = (40.9 5.7stat -4.4 sys) pbNLO QCD (HVQDIS): ep = 20.6 –2.2 pbCascade (CCFM): ep = 28 pbRAPGAP (DGLAP): ep = 14 pb

vis

visvis

+6.0+3.1

vis

Jet variables:Jets in Breit frame: + 2x P = 0: momentum of exchanged photonx: Bjorken xP: Proton momentumSpace-like photon and proton collide head-on

Jet variable:

Isabell-A. Melzer-Pellmann Moriond QCD, 28.3.-4.4.2004

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DIS: Results for DIS variables (Q2, log10(x))

DIS variables:NLO QCD and Cascade (CCFM) describe data reasonably well,Rapgap (DGLAP) underestimates cross sections.

Data slightly higher than NLO QCD (2) at small Q2 and at small x.

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DIS: Results for variables (pT, )

Variables:NLO QCD and Cascade (CCFM) describe data reasonably well,Rapgap (DGLAP) underestimates cross sections.

Data slightly higher than NLO QCD (2) at small pT.

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Measurement technique:D* correlations

Charm Beauty

90°-180°, unlike charge 0°- 90°, unlike charge 90°- 180°, unlike charge 90°- 180°, like charge

Separation by angular and charge correlations:

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Results:D* correlations

22 R ZEUS:H1:incl. data: ep = (214 52stat -84 sys) pb

incl. data: ep = (380 120stat 130sys) pb

Visible cross sections for H1 and ZEUS agree within errors.

like charge unlike charge

vis +96vis

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Event display:D* correlations

s

K+e+e+

s

K+p e+

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Summary:Beauty at HERA

H1 and ZEUS performed various measurements in different kinematic regions:

NLO QCD is in general in good agreement with data in most phase space regions, small discrepancies in some regions have been identified:

P: NLO QCD in good agreement for all regions, LO + PS models slightly below data for high and high pT

DIS: NLO QCD underestimates rate for high ET,jet, low Q2, low x, low pT and high LO + PS models behave similar.

Breit

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Outlook

HERA I has come close to the sleeping beauty… measurements of beauty cross sections require more data to really judge agreement with pQCD

HERA II is prepared to wake the sleeping beauty! Expect factor 5 higher integrated luminosity Detector upgrade (ZEUS: microvertex detector) Improvements on trigger

HERA II

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BACKUP

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Summary plot:Beauty at HERA

Recent H1 and ZEUS resultsimply smaller discrepancy between data and NLO QCD in P as well as in DIS.

P DIS