Status of ZEUSWolfram ZeunerDESY/Hamburg

for the ZEUS Collaboration

• ZEUS Operation

• Shutdown Activities

• Physics Highlights

• Outlook & Summary

PRC open session November 10, 2005

ZEUS Operation

• Congratulation to the HERA crew for the best running period ! • HERA delivered 202pb-1

more than all HERA I

• HERA is able deliver to >1pb-1/day for extended periods of time

• ZEUS is in very good shape, almost all gated data can be used for physics

ZEUS Operation

• ZEUS gated 150 pb-1

• Efficiency: 74%

• ZEUS can record >1 pb-1/day• Recently typical efficiency ~80%

Weekly efficiencies 2004 and 2004/05

• DAQ very stable• Main source of losses: HV trips caused by p-beam spikes

ZEUS OperationRecent example: good and bad fillsDead time due to HV trips and enormous trigger rates

Luminosity lost by CTD trips

0

50

100

150

200

250

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45

Fill number (arbitr)

L[1

/nb

)

(Oct. 8 – Nov. 7):

p-beambackground

e-beam background

CTD current

Efforts to improve the p-beam stability are appreciated

good fill bad fill

CTD Trips

Shutdown Activities

• Forward Straw Tube Tracker (STT) has insufficient cooling Interferes with solenoid operation STT is off since Oct. 2004

• Adding cooling close to the solenoid should solve the problem.• Problem – have to remove FDET without breaking the beam vacuum

now

With add. cooling

700 Kg

CTD

SC coil (~4.5K)

pe

Shutdown Activities

Pull detector over the GO magnet with a special jigDesign has been reviewed by external engineersThe jig is ready and testedThe FCAL has to go off the bottom yoke onto extension rails ----------• The rest is standard repair and maintenance work• Keeping in mind that the detector has to run for ~16 month without major shutdown• Time schedule is ok

Physics Highlights

• HERA I data still being analyzed• All publications so far on HERA I data• First HERA II analysis close to publication

Summer conferences were very successful ZEUS: 42 contributed papers to LP05/HEP05 5 HERA II analyses

Report here:

• High Q2 Cross Sections with Polarized e+/e- Beams• Strong Coupling Constant from Inclusive Jets• Charm Fragmentation Ratios and Fractions• Factorization in Diffraction• Isolated Leptons

High Q2 Cross Sections with Polarized e+/e- Beams

Q2 > 200 GeV2, y < 0.9ZEUS DATA SAMPLE

HERA II

Right-handed Left-handed

e+ L=14.1 pb-1

P=31.8%

L=16.4 pb-1

P=-40.2%

e- L=6.5 pb-1

P=29.2%

L=35.3 pb-1

P=-25.9%

NC

CC

e- e-

High Q2 Cross Sections with Polarized e+/e- Beams Charged current cross section with polarized leptons

0)(Pσ)P(1)(Pσ/eecc/ee/eecc

Direct observation of the chiralstructure of the weak interaction

• Linear dependency on P clearly visible• Agreement with SM prediction No indication of WR

pb(syst.)0.5(stat.)1.622.50.402)(Pσ

pb(syst.)1.0(stat.)2.446.70.318)(PσCC

CC

e+p

e-p

pb(syst.)(stat.)1.986.20.406)(Pσ

pb(syst.)(stat.)3.554.60.292)(Pσ

2.2

2.6

1.1

1.4

CC

CC

First CC measurement as functionof polarization

Charged current cross sections with polarized leptons

Effect of weak interaction visible in diff. distribution over full phase spaceGood agreement with SM predictionCan be used to further constrain PDFs in QCD fits

e+pe-p

Neutral current cross sections with polarized leptons

Again good agreement with SMElectroweak effect starts to become visible

e+ e-

Strong Coupling Constant from Inclusive Jets

• Inclusive jets in Breit frame • Previous measurement is published• and used to extract αs

• Recently included in QCD-fit to reduce PDF uncertainties

• Now 2-fold statistics

• Prediction infrared insensitive • High precision measurement• Compare to NLO QCD (DISENT)

-1

JetBT,

22

81.7pbLdt

GeV8E,GeV125Q

Strong Coupling Constant from Inclusive Jets

(0.1182±0.0027)

Best value for Q2> 500 GeV2

Fit NLO QCD calc.

(theo.)0.0017

0.0029(exp.)

0.0025

0.0019(stat.)0.00110.1196)(Mα Zs

Precision comparable to any other single measurement

Charm Fragmentation Ratios and Fractions

Test universality of charm fragmentationMeasure: (+ anti-particles) in photoproduction (Q2< 1 GeV2, 130 <W < 300 GeV, pT(D,Λc) > 3.8 GeV)

D,Λ,D,D,D cs0

Calculate:Ru/d: Ration of neutral to charged D-meson production rate

γs: Strangeness suppression factor

Pdv: Fraction of D-mesons produced

in a vector state

f(cD, c): Fragmentation fraction of charm into D or c

)σ(σ2σγDDDs 0

s

KpπΛc

Charm Fragmentation Ratios and Fractions

Charged and neutral D-mesonsare produced with the same rate

Ratio of strange to non-strange is26% in charm fragmentation

57% of the charged D-mesonsare produced in a vector stateSmaller than spin countingprediction of 75%

Charm Fragmentation Ratios and Fractions

General good agreement with e+e-

Fragmentation fraction cD* is lower and cc is higher than in e+e- (correlated)

First measurement of in γpHighest precision single measurement

Universality of fragmentation is supported

Factorization in Diffraction

Exchange of colorless objectwith quantum numbers of vacuum

Cross section = Product of parton density function & hard scattering cross section

J.C. Collins showed that factorization holds in ep DIS Phys. Rev. D57 3051(1998),J. Phys. G28 1069 (2002)

Dijets in Diffractive DIS 22 GeV100Q5

GeV250W100pγ*

NLO Calculations DISENT + diffr. Extension

• Data consistent with ZEUS and H1 QCD NLO fit• GLP fit too low Shape of distr. not well described

• Sensitivity on diffractive PDF main uncertainty

• No indication of factorization violation

Factorization in Diffraction

Problem: CDF-Dijet rates factor 3-10 lower than expected, using HERA diffractive PDFs

Idea: Cross section suppression by second. interactions

Test at HERA with resolved photoproduction• photon fluctuates into hadronic system, which takes part in hadronic scattering similar to hadron interactions• prediction by Kaidalov et al res. γp cross section has to be rescaled by 0.34

Phys.Lett.B567 (2003),61 Dijets in photoproductionD* in photoproduction

Hard scale: ET of jet or charm mass

Diffractive γp Production of Dijets

Direct PhP Resolved PhP

1.5η1.5GeV,6.5EGeV,7.5E

0.025x

GeV1Q0.85,y0.2

Jet2T

Jet1T

p

22

• NLO overestimates data by factor 1.6• Shape reasonably described • Scaling the resolved component does not describe the resolved enriched sample

• No indication of factorization violation

Diffractive D* in PhotoproductionNLO does not overestimate dataopposite to dijetsShapes are reasonably described

No indication of factorization violation

Further studies needed:• Diffractive PDFs• PDF dependence of cross sections

Inclusive

eDiffractiv

Inclusive

eDiffractiv

PDF

PDF

σ

σ

NLO description of inclusiveand diffractive PDFs is consistent

0.6(Data/NLO)Dincl.

(Data/NLO)Ddiffr.

)s(Data/NLOincl.Dijet

a/NLO)Dijets(Datdiffr.

Isolated Leptons• SM process for isolated leptons with missing transverse momentum is single W production – cross section (LO) : 1.1pb

• SM background are DIS NC and CC an dileptons with some mis-measurement• The favorite exotic process with the same signature is single top production

Single top production

ZEUS all HERA I dataNo excess to SMNeither e+ nor e- Phys. Lett. B559,153 (2003)

1999-2000

New analysis • Measure W cross section• Cuts very close to those from H1• Analyse: HERA I e+ data from 1999/2000 HERA II e+ data from 2003/2004

Isolated e candidates PTX > 25 GeV

ZEUS (prel.) 99-00

e+p (66 pb-1)

Obs:1;

Exp: 0.92±0.09 (79% W)

ZEUS (prel.) 03-04

e+p (40 pb-1)

Obs:0;

Exp: 0.58±0.09 (76% W)

No excess to SM prediction

Both samples are described by MCSignal: SM W-production

Isolated Leptons

Outlook

• Reconstruction/Tracking very active field at ZEUS Well advanced: New pattern recognition combines CTD + MVD Kalman filter track fit and vertex reconstruction

Under development: Integration of forward tracker and wheels of MVD

Prelim.Impact parameter distribution of muons in γp

MVD tagged D+

Pushing the tracking at HERA IItowards the optimal performance

More and more analyses will profitfrom high precision tracking

Summary

• HERA finishes its best running period

• ZEUS is performing very well and has taken lots of high quality data

• The STT will be operational again after the shutdown

• Many new and interesting physics results Majority of results still from HERA I data HERA II analyses well advanced

• Looking forward to a successful data taking in 2006/07