ZEUS UK Collaboration Status Report
David BaileyUniversity of Bristol
Overview
- Zeus Detector Status
- Performance during running
- Detector upgrades
- HERA upgrade
- Microvertex Detector
- CTD Performance
- Resolution
- dE/dx
- Triggering
- CTD 2005
Zeus Status
- 1997 data-taking efficiency close to 80% throughout
- Benefited from short shutdown
Zeus Luminosity
- 28pb-1 (out of 36) on tape in 1997
- More than doubled existing dataset
Zeus Upgrades
- HES installation completed
- FHES operational for 1998
- Silicon Telescope installed in front of BPC
- Precision low Q2 cross sections
- Background suppression
- Barrel Presampler installed
- Test modules commissioned in 1997
- Full presampler ready for 1998
- Forward Plug Calorimeter
- Installed and ready for 1998
- Enhanced acceptance for diffractive physics
BPC Schematic
Forward Plug Calorimeter
- Improved acceptance for:
- Diffractive physics
- Forward jets (BFKL)
Forward Plug Calorimeter
- Extended ranges in Mx and pseudorapidity
The Future...
- HERA Upgrade
- 36.4pb-1 delivered in 1997 exceeded all expectations but is close to maximum achievable annual luminosity
- Still to make high statistics, high-Q2 measurements
- To explore electroweak physics we need ~1fb-1 on tape by 2005
- To realise these goals requires a major upgrade to the experimental interaction region
- New possibilities to use polarised lepton beams
- UK Physicists are heavily involved in the upgrade program, assessing the impact of modifications to the machine on ZEUS as a whole
Upgrade Parameters
Upgrade Impact on ZEUS
Upgrade Impact on ZEUS
- Effect on FDET Multiplicity
ZEUS Microvertex Detector
- Already presented and approved
- Currently in the final design stages
- Installation scheduled for 1999/2000 shutdown
- Will bring significant benefits:
- Secondary vertex detection
- Order of magnitude increase in charm detection efficiencies
- Precise measurement of F2charm
- Tagging charm in jets
- Enhanced capability for exotic physics searches
- Improved primary vertex and tracking measurement
MVD Layout
Charm Tagging with Microvertex Detector
ZEUS-UK MVD Progress
- Installation of MVD in ZEUS
- Installation scheme specified
- Design drawings for installation and mounting on the CTD are complete
- Required close contact between UK, beampipe and MVD construction groups
- Next steps to produce detailed engineering drawings and manufacture installation equipment
- Alignment of MVD
- Test setup of opto-electronic alignment system working
- Position resolution ə?m achieved for single sensor in lab
- Database for alignment parameters under discussion
- Clock and control electronics
- Functionality completely specified
- Prototype ready by August 1998 for electronics integration tests
CTD Status
- Running smoothly
- Resolutions stable
- Significant effort required from DQM to maintain optimal performance
- ZEUS physics depends on the CTD
dE/dx
- dE/dx used in many analyses
- Improved signal:background for exclusive final state measurements (see above)
- HV set by pressure for optimal pulseheight distribution
- Clear particle separation
CTD Trigger
- ZEUS trigger selects events from e-p interactions
- Powerful background rejection
- Rate reduction from ~10KHz to ~5Hz of physics events
- Three-level design
- CTD information is used at all levels of the trigger
- CTD first-level trigger was completed for 1996 running and is vital for efficient Zeus data-taking
- CTD second-level trigger processing speed improved to minimise deadtime
- CTD data now available for use in MVD/Global second-level trigger scheme
CTD SLT Latency
- Latency reduced by ~1ms after code improvements
CTD 2005
- The CTD has operated reliably for 6 years with no degradation in performance
- Rich physics program until 2005
- The CTD must operate efficiently and reliably until then
- We are addressing the issues involved:
- Thorough review of all CTD subcomponents
- Software
- Electronics
- Spares availability
- Continuing access to expert knowledge in the UK
- Experience of UK engineers crucial on occasion
The CTD in Physics
- ZEUS analyses depend on the CTD
- Vertex
- Accurate reconstruction of kinematic variables
- Tracks
- Exclusive final states
- Particle identification
- High-Q2 electrons
- ? identification
- Good Monte Carlo description
Kinematic Variables
- Variables reconstructed from energy and angle of positron and hadronic system
Charm Production
- Start at the low-Q2 end of the market...
- Search for charm by reconstructing D* in final states using tracking
- Most popular decay used is
Charm in the Photon
- To leading order, two types of process contribute to charm cross-section - “Direct” and “Resolved”
- Question of how to treat charm in the photon
- Particular interest in “Resolved” charm as charm content of photon is poorly understood
Charm in the Photon
- Use dijet sample to measure x?
- x? is a measure of the fraction of the photon’s momentum participating in the hard process
- “Direct” processes have x? close to 1
- Cross section d?/dx? gives clues to the nature of the underlying process
- Look for D*s associated with these jets
Charm in the Photon
- Clear evidence for a significant “resolved” component to charm production
- The work on charm in jets is just beginning in earnest
Semi-Leptonic Charm
- Analysis still in early stages
- Uses dE/dx to identify electrons from semi-leptonic decays of charm
- Statistically independent sample of charm
- First obvious analysis for microvertex detector
Charm in the Proton
- Reconstruct D* in final state
- Measure charm content of F2 directly
Charm in the Proton
- Direct handle on gluon density (BGF mechanism dominant)
- Sensitivity to low-x QCD compared to inclusive F2 measurement
- Understand Q2 evolution of massive quark parton density
Charm in the Proton
Charm in the Proton
- More data now available from 1996/1997 running
- New channels to be investigated: K???? decay mode of D*
Charm in the Pomeron?
- Diffractive events characterised by no energy in calorimeter around forward beam direction
- Process now understood as probing the structure of a colourless exchange object - the Pomeron
Charm in the Pomeron?
- Select events by position of most forward calorimeter object (?max)
Charm in the Pomeron?
- One of the key processes to differentiate models of diffraction and give insight on the nature (or existence) of the pomeron
- Now moving on to look at combined 1996/1997 data
- Higher statistics
- Differential distributions
To Conclude
- We are looking forward to electron running 1998/1999
- After the upgrade HERA will provide high-luminosity running with polarised electrons and positrons
- New physics?
- Polarised measurements
- Microvertex detector upgrade
- High charm tagging efficiencies
- Zeus and UK effort on schedule
- And there’s more to come...