ZEUS Status Report

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ZEUS Status Report

• 2002-2003 Running Period
• Detector Progress
• Data Analysis
• Background Studies
• Physics Results Highlights
• Physics Outlook and Goals

• Stathes Paganis
• Columbia University
• On behalf of the ZEUS Collaboration
• PRC Meeting May 2003

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2002-2003 Running Period
Data Collected 2000 (L45.8pb-1) and
2002/2003 (L1.55pb-1)
CTD at 95HV
Neutral Current Event
Charged Current Event
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Microstrip-Vertex-Detector (MVD)

• 267 runs with 3.1Mio events recorded between
  10/31/02 and 02/18/03 with MVD on and DQM (gt 676
  nb-1)
• DAQ reliable and conforms to the ZEUS
  specifications

• Run selection criteria were
• ep run
• more than 2k events
• CTD on (95 voltage)
• MVD on and DQM-checked ok
• Event selection
• E-Pz gt 10
• abs(VtxZ)lt40
• More than 2 vertex tracks
• Less than 25 vertex tracks.
• electron energy gt 10 GeV

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K0S with MVD
Mpp(GeV)

• MVD had a successful commissioning period.
• The detector is running well
• Radiation dosage is monitored
• Alignment, Tracking and Vertexing are coming
  along nicely.

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Straw Tube Tracker (STT)
Detector installed into ZEUS in April 2001 After
installation a few H/W problems were identified
which prevented effective data taking A
committee reviewed repair plans February 18,
2003 final go-ahead for the STT repairs March/3
present STT removed and repairs have been
succesfully completed STT now installed back in
ZEUS and all channels are working as expected
STT dismounted for repairs
STT remounted after repairs
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Luminosity Monitors and Measurement
ZEUS has two luminosity monitors photon
calorimeter and spectrometer Detectors
(calorimeter, spectrometer), FEE and digital
electronics commissioned and operational. Both
systems report lumi and beam profiles on-line to
HERA via the ZEUS lumi-monitor.
Full 2000 lumi used
The measured Luminosity was used by several
2002-2003 studies by all physics groups. Very
important for example in studies of background
effects on physics.
Neutral Current event rates from 2002 compared to
2000 rates normalized by the luminosity, are
in very good agreement
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Background at ZEUS IP

• SUMMARY
• Understanding of background conditions has been
  very challenging.
• Effort of many people.
• Quantitative understanding of background achieved
• Modifications to IP area planned and reviewed
• Significant improvement of synchrotron radiation
  background x10
• Positron background improvement factor of 2
• Several measures to improve proton beam-gas
  background.
• After the modifications we expect that ZEUS will
  be able to run at the highest luminosity
• Shutdown to effect these changes are on
  schedule

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Physics Highlights

• ZEUS 8 papers since last PRC, 50 abstracts
  submitted to EPS

• High ET and high Q2 physics
• Extraction of as from PhP
• Diffraction and low x
• Inclusive diffraction with FPC
• First measurement of FL
• Hadronic Final States
• KsKs final state in DIS
• Searches for new physics
• Lepto-quarks and single top
• Heavy Flavour Physics
• Charm fragmentation fractions
• Charm content of the photon in charm
  photoproduction

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High ET jet cross section in gp
Inclusive jet cross section in gp has been
measured with high precision, allowing for small
exp. error as determination
as is determined at different bins of ET as
running is observed in a single measurement
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High ET jet cross section in gp
as determination from incl. jet cross sections in
gp and comparison with other measurements.

• as measurement consistent with all recent
  measurements
• Small experimental uncertainties competitive
  with LEP
• Theoretical uncertainty larger than the
  experimental error

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Inclusive Diffraction with FPC
adiff determined by fitting ds/dMx
atot determined by fitting the F2 x distributions
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Inclusive Diffraction with FPC
Data (4ltMxlt8 GeV) show

• For Q2gt10GeV2 aIPdiff(0) lies above soft pomeron
  and its Q2 dependence is clearly visible.
• aIPdiff(0) is half that expected from inclusive
  DIS aIPtot(0).

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DIS at low x first measurement of FL

• F2, FL functions of (x,Q2) only, but
• cross section also depends on sE2
• Measure it at different energies

OR exploit events with hard ISR photons radiated
from the lepton
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KsKs final state in DIS
Scalar Mesons
K0(1430)
K0(1430)
0

f0(8)
f0(1)
a0(????)
a0(????)
-

a0(????)
0
K0(1430)
K0(1430)
-
0
f0(8)
f0(1370) uudd f0(1500) ?? f0(1710) ss
f0(1)
glueball candidate
First observation of JCP(even) in DIS two
states are observed a state consistent with
f2(1525) and f0(1710)
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Searches Leptoquark and single top limits
NC Flavour changing coupling
HERA-I limits competitive with LEP, LEP-II and
Tevatron Run I
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Heavy Flavours charm fragm. fractions
Fragmentation fractions first shown in DIS03
Combined ee-
H1 prelim.
Charm fragmentation fractions are universal
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Heavy Flavour Physics dijet angular distributions
Resolved
Direct
Resolved
Resolved

• Dijet angular distributions in photoproduction of
  charm depend on the spin of the exchanged
  particle
• For quark exchange a symmetric distribution in
  cosq is expected
• For resolved processes we observe a steep rise of
  the cosq closer to the photon, a characteristic
  of a gluon exchange most of the resolved g
  contribution in charm production comes from charm
  from the photon

charm in the photon
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Physics Outlook and Goals

• ZEUS HERA-I results close to completion Ready
  for HERA-II

• DIS and high ET jet cross sections
• HERA-I Finalize Incl. DIS and high ET jet
  production in DIS and PhP
• HERA-II Polarization, electron running, increase
  high x PDF accuracy
• Diffraction
• HERA-I Finalize incl. diffraction and LPS 97-00
  analysis, VM diffra- ctive production (phpDIS)
• HERA-II High Q2 inclusive, hadr. final states,
  VM, D, very high t VM, heavy VM (U), DVCS
• Searches for new physics (substructure, CI, LQ,
  ...)
• HERA-I Use final NC data to complete the contact
  interaction paper
• HERA-II Use polarization, CC, and e- to extend
  CI searches.
• Heavy Flavour Physics
• HERA-I Finalize remaining charm and first beauty
  measurements
• HERA-II The addition of the MVD upgrade opens
  the beauty sector to ZEUS.

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• Modification of Collimators
• Modification of C5b, C5c is almost equivalent to
  effect of
• vertical collimator
• After improvement (SR and e-gas) background very
  much dominated by p-gas.
• Vertical collimator substantial risk of new
  vacuum problem due to HOM losses, heating and
  out-gassing.
• Decided not to install vertical collimator
• (Consider new design of absorber 1 with vertical
  movable jaws with cooling.)
• Expect a factor of ? 10 improvement of
  synchrotron radiation background without taking
  coating of absorber into account

• Proton Beam-Gas Improvements
• Decreased thickness of C5
• C5a CTD current reduced by 15
• C5b small increase of CTD current
• C5c CTD current reduced by 20
• Improvement of vacuum system (MVA)
• Increase conductance of pumping ports absorbers
  1/2 SR3.6/6
• Increase pumping (ion getter pumps)
• SR3.6 30l/s ? 2 60l/s pumps
• SR6 60l/s ? 120l/s pump
• SR8 60l/s ? 120l/s pump
• Coating of absorber at SR11 (if possible) (MVA)
• Back-scattering of synchrotron radiation reduced
  by factor 1.8
• Less out-gassing, proton beam-gas background
  reduced.

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Expected Background Conditions
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Expected Background Conditions

• Expected CTD current reduction at design beam
  currents (0.1µA)
  
  
  (for 95 HV)
  after
  improvements
• Synchrotron radiation background
  1/10
• Positron background
  1/2
• Proton background (x2 improvement of vacuum)
  1/2

95HV no Vacuum improvement
Total
Total
2003 Limit (360 units)
proton
2000 Limit (120 units)
e-gas
synchrotron
ZEUS will be able to run under these conditions
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CTD Efficiency dependence on thresholds
Most of the lost hit efficiency is recovered by
decreasing the DSP threshold
Hit efficiency decreases when the HV is reduced
from 100 to 95
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