Current Projects in the ZEUS collaboration

Current Projects in the ZEUS collaboration

Mónica L. Vázquez AcostaMónica L. Vázquez Acosta

Max Planck Institute, Munich, 09.05.2005

Current Projects in the ZEUS Collaboration, Mónica L. Vázquez Acosta (NIKHEF) Max-Planck Intitute MunichMax-Planck Intitute Munich, 09/05, 2005 - 2

HERA: ep ColliderHERA: ep ColliderHERA: ep ColliderHERA: ep Collider

H1: ep interactions

HERA-B: p beam+fixed target

HERMES: polarised e + fixed target

ZEUS: ep interactions

920 GeV protons27.5 GeV positrons


Measures taken:• Additional collimators far upstream of IPs• Additional pump near IP

HERA-II no longer current-limited due to backgrounds

Background problems in HERA-II solved!Background problems in HERA-II solved!Background problems in HERA-II solved!Background problems in HERA-II solved!

Shutdown 2003

mea

sure

of

bac

kgr

oun

d

positron beam current2001: Luminosity upgrade & new silicon detector (MVD)2002-2003: background struggle


ZEUS Gated Luminosity ZEUS Gated Luminosity ZEUS Gated Luminosity ZEUS Gated Luminosity

ZEUS gated: 43.7 pb-1

ZEUS gated: 48.36 pb-1

plot 09/03/05

Most ZEUS data is good MicroVertexDetector(MVD) data

Efficiency loss due to: Bad conditions in the initial tuning after luminosity is declared, which prevents to switch on the tracking chambers DAQ problems which now have been solved


Radiation Monitor SystemRadiation Monitor SystemRadiation Monitor SystemRadiation Monitor System

zx-Querschnitt

4x2 PIN diodes 4x2 PIN diodes

-100 cm

110 cm

BMVDFMVD

z=160 cm -120 cm

-130 cm

4 RadFET

X

Z

4 RadFET8 RadFET

8 RadFET

Silicon PIN diodes Instantaneous dose rate from signal current Automatic dump system Bulk damage from offset leakage-current

Radiation Field Effect Transistors (RadFETs) Monitor surface damage from shift in threshold voltage


Silicon pin diodes: fast radiation monitorSilicon pin diodes: fast radiation monitorSilicon pin diodes: fast radiation monitorSilicon pin diodes: fast radiation monitor

Threshold alarm: 1000 nA ~ 0.02 kRadThreshold dump: 4000 nA ~ 0.08 kRrad Forgiveness rate: 10 nA/s : allows short-term increase during injection and small constant background

25 kRad expected dose in the MVD by end of HERAII Front end chips tested up to 300 kRads

Maximumfill level

ffill Isignal = Idiode - Ileakage

fforgiveness

Actualfill level

bucket overflow beam dump

Dump signal to HERA


Silicon Pin Diodes: leakage currentsSilicon Pin Diodes: leakage currentsSilicon Pin Diodes: leakage currentsSilicon Pin Diodes: leakage currents

Diodes on ring inside,closest to beamline

ShutdownProton beam-loss accident

Long term increase and annealing of leackage currentSubtract pedestal before each fill


RADFETs: integrated doseRADFETs: integrated doseRADFETs: integrated doseRADFETs: integrated dose

Steady increase during beam operationStep like increase from single beam-loss accidentsValues expected higher in rear than in MVD (-0.3m) due to: backscatter in C5 collimator synchrotron radiation and off momentum positrons

Dos

e (k

Rad

)

MVD (-0.6m) REAR (-1.7m)C5 (-1m) FORWARD (1.3m)


Radiation damage in the MVDRadiation damage in the MVDRadiation damage in the MVDRadiation damage in the MVD

No evidence of significant radiation damage

- Mean signal size stable

- Uncontrolled proton beam loss (4 Nov 03)

caused 10% drop in signal

- Big effort of HERA to reduce the risk

to <1 till end of running

- Noise shows a shallow slope

- Corresponds to 6 kRad in 500 days

on innermost cylinder

Detector in good shape

- Bad channels stable <2%


The MVD is there ...The MVD is there ...The MVD is there ...The MVD is there ...

All vertices in the XY plane with -25 cm < Z < 25 cm The interactions in the material of the beampipe and the MVD are clearly seen

Ladders 3% Xo


MVD Alignment with cosmic muonsMVD Alignment with cosmic muonsMVD Alignment with cosmic muonsMVD Alignment with cosmic muons

うQ’

Q

P

P

MVD alignmentminimize the difference betweenthe expected track position andthe measured hit position

cosmic track reconstruct as 2 tracks

0ZThe mismatch distribution has a width of 97 m after alignment

Before alignment

After alignment


Impact parameter resolution from cosmicsImpact parameter resolution from cosmicsImpact parameter resolution from cosmicsImpact parameter resolution from cosmics

cosmic track reconstruct as 2 tracks

0Z

Difference of two independent tracks so divide by √2 : 83/pt + 47 m

This satisfies the design criterium of an impact parameter resolution of 100 m

After MVD alignment


Tracking quantities in ep DIS dataTracking quantities in ep DIS dataTracking quantities in ep DIS dataTracking quantities in ep DIS data

Tracking quantities are well describedThe point of distance of closest approach is well described


DD++: charm: charm taggingtagging with the MVDwith the MVDDD++: charm: charm taggingtagging with the MVDwith the MVD

The combinatorial background is reduced by a factor 45 and the signal by a factor 2.7

Submitted to ICHEP2004


Event display of a DIS DEvent display of a DIS D++ candidate candidateEvent display of a DIS DEvent display of a DIS D++ candidate candidate

Q2 = 160 GeV2

pt(D+)=5.1 GeV


Charm semileptonic decays in DISCharm semileptonic decays in DISCharm semileptonic decays in DISCharm semileptonic decays in DIS

Charm tagging: detect charmed mesons BR(c→D*) = 2.6 % detect e- BR(c→e-) = 9.6 %

Q2

Electron tagging using: CAL clusters with a matched track & dEdx CAL deposit requirementEEMC/ETOT>0.9 ("electron sample")EEMC/ETOT<0.4 ("hadron sample") → Estimate background


Charm semileptonic decays in DISCharm semileptonic decays in DISCharm semileptonic decays in DISCharm semileptonic decays in DIS

HERA-I 99-00 data

Results to be made preliminary for EPS05


Jet production in charged current DIS Jet production in charged current DIS Eur.Phys.J.C31: 149-164, 2003Eur.Phys.J.C31: 149-164, 2003

Jet production in charged current DIS Jet production in charged current DIS Eur.Phys.J.C31: 149-164, 2003Eur.Phys.J.C31: 149-164, 2003

Test flavour changing electroweak theory and QCD in one type of events


Jet Substructure: mean subjet multiplicityJet Substructure: mean subjet multiplicityJet Substructure: mean subjet multiplicityJet Substructure: mean subjet multiplicity

(th.)(syst.)(stat.)0.0052 0.1202)(Mα 0.00650.0053

0.00600.0019ZS

QCD does not distinguish if W (CC) or (NC) is exchanged

NC CC

The kT algorithm is reapplied to particles assigned to jet until distances between clusters:

2jetTcutij Eyd

HERA physics is excitingbut the LHC is calling ...

Current Projects in the ZEUS collaboration

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