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Current Projects in the ZEUS collaboration

Current Projects in the ZEUS collaboration. Mónica L. Vázquez Acosta. Max Planck Institute, Munich, 09.05.2005. HERA: ep Collider. H1: ep interactions. 920 GeV protons 27.5 GeV positrons. HERMES: polarised e + fixed target. HERA-B: p beam+fixed target. ZEUS: ep interactions.

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Current Projects in the ZEUS collaboration

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  1. Current Projects in the ZEUS collaboration Mónica L. Vázquez Acosta Max Planck Institute, Munich, 09.05.2005

  2. HERA: ep Collider H1: ep interactions 920 GeV protons 27.5 GeV positrons HERMES: polarised e + fixed target HERA-B: p beam+fixed target ZEUS: ep interactions

  3. Background problems in HERA-II solved! HERA-II no longer current-limited due to backgrounds measure of background positron beam current 2001: Luminosity upgrade & new silicon detector (MVD) 2002-2003: background struggle Measures taken: • Additional collimators far upstream of IPs • Additional pump near IP Shutdown 2003

  4. ZEUS gated:43.7 pb-1 ZEUS gated:48.36 pb-1 plot 09/03/05 ZEUS Gated Luminosity • 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

  5. 4x2 PIN diodes 4x2 PIN diodes 8 RadFET FMVD BMVD zx-Querschnitt 4 RadFET 8 RadFET 4 RadFET Z X -100 cm -130 cm 110 cm -120 cm z=160 cm Radiation Monitor System 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

  6. ffillIsignal = Idiode - Ileakage Maximum fill level Actual fill level fforgiveness Silicon pin diodes: fast radiation monitor • 25 kRad expected dose in the MVD by end of HERAII • Front end chips tested up to 300 kRads bucket overflow beam dump Threshold alarm: 1000 nA ~ 0.02 kRad Threshold dump: 4000 nA ~ 0.08 kRrad Forgiveness rate: 10 nA/s : allows short-term increase during injection and small constant background Dump signal to HERA

  7. Silicon Pin Diodes: leakage currents Diodes on ring inside, closest to beamline Shutdown Proton beam-loss accident Long term increase and annealing of leackage current Subtract pedestal before each fill

  8. MVD (-0.6m) REAR (-1.7m) C5 (-1m) FORWARD (1.3m) Dose (kRad) RADFETs: integrated dose • Steady increase during beam operation • Step like increase from single beam-loss accidents • Values expected higher in rear than in MVD (-0.3m) due to: • backscatter in C5 collimator • synchrotron radiation and off momentum positrons

  9. Radiation 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%

  10. The MVD is there ... • All vertices in the XY plane with -25 cm < Z < 25 cm • The interactionsin the material of the beampipe and the MVD are clearly seen Ladders 3% Xo

  11. P Q P う Q’ MVD Alignment with cosmic muons MVD alignment minimize the difference between the expected track position and the measured hit position Before alignment cosmic track reconstruct as 2 tracks After alignment The mismatch distribution has a width of 97 mm after alignment

  12. Impact parameter resolution from cosmics After MVD alignment cosmic track reconstruct as 2 tracks Difference of two independent tracks so divide by √2 : 83/pt + 47 mm This satisfies the design criterium of an impact parameter resolution of 100 mm

  13. Tracking quantities in ep DIS data The point of distance of closest approach is well described Tracking quantities are well described

  14. D+: charmtaggingwith the MVD Submitted to ICHEP2004 The combinatorial background is reduced by a factor 45 and the signal by a factor 2.7

  15. Event display of a DIS D+ candidate Q2 = 160 GeV2 pt(D+)=5.1 GeV

  16. Charm 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 requirement • EEMC/ETOT>0.9 ("electron sample") • EEMC/ETOT<0.4 ("hadron sample") → Estimate background

  17. Charm semileptonic decays in DIS HERA-I 99-00 data Results to be made preliminary for EPS05

  18. Jet production in charged current DIS Eur.Phys.J.C31: 149-164, 2003 Test flavour changing electroweak theory and QCD in one type of events

  19. Jet Substructure: mean subjet multiplicity The kT algorithm is reapplied to particles assigned to jet until distances between clusters: NC CC QCD does not distinguish if W (CC) or g (NC) is exchanged

  20. HERA physics is exciting but the LHC is calling ...

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