ZEUS Status Report

1
ZEUS Status Report
Alessandro Polini On behalf of the ZEUS
Collaboration
63rd Physics Research Committee Meeting 10 May
2007

• Contents
• Luminosity and Statistics
• Physics Highlights
• Low Energy Running

2
Luminosity

• High Energy Running (HER) vs 300-320 GeV
• Switch e-p ? ep June 2006
• Total HER luminosity delivered by HERA
  (1993-2007) 758 pb-1
• Total ZEUS Physics Luminosity 0.5 fb-1
• Low Energy Running (LER) vs 225 GeV (p460
  GeV)
• As of today 8 pb-1 gated
• End of HERA on July 2nd

Period ep e-p
HERA-I 115 pb-1 17 pb-1
HERA-II (pol. e) 182 pb-1 190 pb-1
Total 297 pb-1 207 pb-1
3
Physics Highlights

• New preliminary results (DIS 2007)
• Jets in NC - HERA II
• F2c from D (HERA-II)
• F2c from HERAII (MVD)
• F2b at HERA II
• Scaled momenta distribution
• Multijet production in CC
• Charm fragmentation
• F2 at high-y and Low Energy Run Control
• NC e-p HERA II
• Exclusive ?0 in DIS
• High ET jets
• Isolated Leptons
• Multi-leptons
• Almost final results
• Observation of d and d in DIS
• Diffractive dijets in Photoproduction
• Forward jets
• Multijets at low x

• Papers published since last PRC
• Measurement of D Mesons Production in Deep
  Inelastic Scattering at HERADESY-07-052 (April
  2007) submitted to JHEP
• Diffractive Photoproduction of D(2010) at
  HERADESY-07-039 (March 2007)
• Measurement of D Meson Production in ep
  Scattering at low Q2DESY-07-012 (January 2007)
• Leading Neutron Energy and PT Distributions in
  Deep Inelastic Scattering and Photoproduction at
  HERA
  DESY-07-011 (January 2007)
• Jet-radius dependence of inclusive-jet cross
  sections in deep inelastic scattering at
  HERADESY-06-241 (December 2006)
• Measurement of K0s, Lambda, Antilambda
  Production at HERADESY-06-226 (December 2006)
• Photoproduction of Events with Rapidity Gaps
  between Jets at HERADESY-06-215 (November 2006)
• Measurement of open beauty production at HERA
  in the D muon final stateDESY-06-166 (September
  2006)
• Search for stop production in R-parity-violating
  supersymmetry at HERADESY-06-144 (November 2006)

4
Inclusive Jets in the Breit Frame in DIS

• Inclusive jets in Breit frame directly sensitive
  to aS and g(x)
• All HERA-I data published, good agreement with
  NLO QCD
• Small theoretical uncertainty (5) at high ET
  and Q2
• New measurement

Running of aS
Jet Radius Dependence
DESY06-241
5
High ET Dijets in Photoproduction

• HERA 98-00 data
• ETj1,j2 gt 20, 15 GeV
• -1 lt ? lt 3 (at least one in -1 lt ? lt 2.5)
• Good description
• by NLO QCD
• Sensitivity to
• g(x) in ? and p
• Large uncertainties
• for low x?obs
• due to choice of
• photon PDF

Direct Photon (x? 1)
Resolved Photon (x? ltlt 1)
6
HERAII - CC FOUR-Jet Events!
7
Diffractive Dijets in Photoproduction

• Do diffractive PDFs from inclusive DIS describe
  hard processes in Photoproduction (Dijets)?
• Dijet Photoproduction
• Data is final
• No need to rescale low x? region
• ?No evidence of factorization breaking

HERA-I ET j1,2gt 7.5, 6.5 GeV ?lt1.5 xIPlt0.025
8
Hard Diffraction in Photoproduction

• Do diffractive PDFs from inclusive DIS describe
  hard processes in photoproduction (D)?
• D Diffractive Photoproduction
• Data consistent with NLO QCD
  prediction within
  scale uncertainties
• Agreement with diffractive
  QCD factorization

DESY-07-039
HERA I data pTgt 2 GeV ?lt1.5
9
Exclusive ?0 production in DIS

• Full HERA-I (120 pb-1) (70000 ?0 0.65lt
  M(pp-)lt1.1 GeV)
• Very precise data up to large Q2
• Transition from soft to hard vs Q2 seen in d, b
• No available model is able to describe all
  the features of the data

10
Scaled Charged Track Momentum Distributions

• New prel. result based on full HERA luminosity
  (475 pb-1)

• Extend previous data up
• to Q2 40000 GeV2
• xp p(track)/(Q/2)
• current region of
• the Breit Frame
• Scaling violation observed
• Compared to NLO with
• fragmentation functions
• from ee-
• Agreement not so good
• (similar from MC and MLLA)

11
Deuterons and Antideuterons at HERA

• First measurement in DIS
• First d in elementary particles collisions
• Coalescence Model
• B2 in agreement with H1 PHP
• 3 times less antideuteron observed than deuterons

Full HERA I data
12
Charm Production in DIS

• New measurements in DIS with different
  techniques
• Combined D, D0, Ds (HERA-I)
  
  
  (DESY-07-012)
• D (prel.)
  
  HERA II 162 pb-1 ?
• D (prel.)
  HERA-II
  135 pb-1
• Key use of the new
  Microvertex Detector
  ?
• Decay Length selection L/s gt3

13
Extraction of F2cc and F2bb
F2bb (prel.) µ jet(pTrel) 39 pb-1 03-04 data

• Precise measurements of F2cc
• Also available HERA II measurement of F2bb

14
Isolated leptons and pTmiss

• Analysis of ep data up to 2006 (228 pb-1)
• All e-p 98-06 (204 pb-1)

e-p
µ
ep
e q ? e q W W ? l ?
e
µ
No excess found, good agreement to Standard Model
15
Multileptons
M12 inv. mass of highest PT electrons
Bethe Heitler Dominant process

• Multielectron analysis
• Almost full luminosity (446 pb -1)
• ee 2 central e with pTgt 10,5 GeV
• eee additional e with Egt 10 GeV (5 rear)
• ? Good agreement with SM

16
Neutral Currents e-p vs ep, xF3
Update using the full e- HERA II data
xF3 direct measure of valence quarks from
pure p target
e-p unpolarized from combined HERA-II polarized
data to P 0
ep unpolarized from HERA-I
17
HERA II DIS at high-y

• Extending the DIS analysis to high y (low x, Low
  Ee)
• Preparation for FL analysis with low energy data
• Data taken with special high-y trigger in 2006

• Improved over HERA-I at
• high-y for Q2 lt 100 GeV2

18
HERA II DIS at high-y

• Extending the DIS analysis to high y (low x, Low
  Ee)
• Preparation for FL analysis with low energy data
• Data taken with special high-y trigger in 2006

• Improved over HERA-I at
• high-y for Q2 lt 100 GeV2

19
Low Energy Running

• End of HER March 21st.
• First good LER data already March 26th
• ZEUS so far
• Total Luminosity 8.28 pb-1
• 15 million events on tape
• If 0.25 pb-1 per day
• ? 10 pb-1 by middle of May

Our deepest appreciation and congratulations to
the machine group for the excellent achievements
SR11 leak HW-DAQ Problems
20
LER Trigger and Data Taking
CTD Current
Low Energy Run

• Data taking
• Situation satisfactory
• Smooth Running HV on in all chambers,
• No prescales, deadtime below 2 (as in HER)
• New trigger with at high-y
• Lower threshold in EMC Rear CAL (level 1)
• Looser electron requirement (level2/3)
• E-pz inclusive trigger (level2/3)

High Energy Run
April 2007
GFLT Output Rate
Deadtime
Lumi x1031
21
FL Photoproduction Background

• 6m tagger
• Small tungsten/scintillator (SCSF-34M) spaghetti
  cal
• 100 acceptance for e of 5-8 GeV
• Trigger without electron finding ? PHP events
• Sample with clear e candidate DIS sample
• Sample with unclear e candidate PHP enriched
• Normalization of PHP MC with respect to
• 6m tagged sample
• PHP enriched sample
• agrees within 5 (assumed conservatively
  10 for the high-y
  analysis)

22
First Look at Low Energy Data

• First Data collected at reduced proton energy
• (Ep460 GeV, Ee27.6 GeV)
• Everything looks as expected
• Looking forward for a promising FL measurement

23
Conclusions and Outlook

• ZEUS has collected 0.5 fb-1 analysis of full
  luminosity started
• HERA II measurements of heavy flavor production
  using the MVD are coming
• Results on high Q2 DIS from full e-p HERA II
  data will be input to next generation of PDF and
  EW fits
• No deviation from SM seen in NC, multileptons,
  isolated leptons
• Including new data on jets provides precision
  tests of QCD, and sensivity to g(x), as ,
• Low Energy Run for the measurement of FL going
  well
• Detector in good shape
• Target luminosity on tape in a week
• Although HERA is going to end in 50 days a very
  rich program of measurements is well under way