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Zeus UK Status Report Part II

Zeus UK Status Report Part II. Rod Walker Imperial College London 15th May 2000. Physics activities. Post-upgrade physics opportunities with polarised beams. Polarimeter upgrade. Message: It`s big init. Words: The 96/97 data has allowed us to go to. HERA Kinematic Plane.

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Zeus UK Status Report Part II

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  1. Zeus UK Status Report Part II Rod Walker Imperial College London 15th May 2000 • Physics activities. • Post-upgrade physics opportunities with polarised beams. • Polarimeter upgrade.

  2. Message: It`s big init. Words: The 96/97 data has allowed us to go to... HERA Kinematic Plane • High Q2 and x region probed. • Overlap with fixed target data. Q2(GeV2 ) PPESP, RAL, May 2000

  3. e+p:d, s and u, c e-p:u, c and d, s Deep inelastic scattering Neutral Current Photon/Z exchange Charged Current W exchange `invisible`Missing PT Q2 Q2 ep:All flavours contribute PPESP, RAL, May 2000

  4. Message:- Now have both e+ & e- data. • Words: FL is negligable compared to F2 and xF3, but work is underway to measure it using ISR. NC cross section • e+p & e-p data. • 48pb-1 e+p (94-97) • 16pb-1 e-p (98-99) • (e-p) > (e+p) • Good agreement with SM over 6 orders of magnitude. PPESP, RAL, May 2000

  5. NC: d/dx • Agreement with SM • Z interference at High-Q2 PPESP, RAL, May 2000

  6. Message:- Higher precision at low x, extended range at high x - overlap with fixed target. • Words:- F2 from 94 has already added greatly to our knowledge of the proton structure, strong scaling violations at low-x. • 96/97 data represents 10 fold increase in luminosity which allows much higher precision in the highQ2 region, and also new bins at high x are accessible giving overlap with fixed target data. F2 • 94 F2 • QCD fits • Strong scaling violations • New 96/97 F2 • 12published lumi • Improved precision at high-Q2 • Extend to higher-x at high-Q2. PPESP, RAL, May 2000

  7. Rise of F2 at low x measured with high precision.

  8. Strong scaling violations

  9. Words:Sensitive to the lepton charge. Turn over at high Q2. Turn up for e-. e+p e-p Double differential cross sections PPESP, RAL, May 2000

  10. Message:- xF3 precision comparable to first 92 F2 extraction and will benefit greatly from lumi upgrade. Constrains high x valence quark distbn, important in estimating very high energy processes at LHC. First extraction of xF3 at high-Q2 and x. • Precision comparable to first F2 extraction. • FL contribution is negligible. • Sensitive to valence quarks at high-x. PPESP, RAL, May 2000

  11. Message:- xF3 precision comparable to first 92 F2 extraction and will benefit greatly from lumi upgrade. Constrains high x valence quark distbn, important in estimating very high energy processes at LHC. First extraction of xF3 at high-Q2 and x. • Can extract s from the slope. • Much improved precision after upgrade. PPESP, RAL, May 2000

  12. Charged Current e+p Valence d probed. Sensitive to quark flavours. d/u ratio u unsuppressed e-p Mw PPESP, RAL, May 2000

  13. Mw measurement Normalisation:xsec at Q2=0 1 σ contour of χ2 distbn • Fit normalisation and shape. • Direct measurement of Mw in space-like region. PPESP, RAL, May 2000

  14. Double differential cross section High-x dominated by valence d quarks. High-y dominated by sea quarks. e+p

  15. Message:- Lots of new physics opportunities. But need 2% measurement of polarisation • Words:- Right handed W- is not allowed in SM. Similarly left handed W+. Zeus can set exclusion limits ~400GeV. • Vector and axial couplings to light quarks can be measured from fits to NC and CC cross sections from the 4 permutations of lepton charge and polarisation. Particularly for the vector couplings, where a factor 6 increase on precision over unpolarised beam scenario is possible, polarised beams are essential. Knowledge of the unpolarised F2 at high-Q2 is important to reduce errors. Not only is Hera F2 measurement crucial for the new pp collider, it also feeds directly back into future Hera physics. e-L p  v Xe-R p  v X Future Physics:- Lepton Polarisation • Parity violation in CC • SM • RH W- limit Mw>400GeV • Light quark couplings • Fits to NC&CC cross sections for R&L pol. • Polarisation measurement. • Require 1-2% precision • Currently only 4% P Large effect PPESP, RAL, May 2000

  16. Message: Here`s what we’ve got. TPOL can be improved. Words:Laser alternates between L&R circular polarisation. LPOL uses the energy asymmetry Polarimeter • Longitudinal &Transverse POLs exist. • Circularly polarised laser shone on lepton beam. • Detect back-scattered compton photons. • TPOL- uses up/down asymmetry between L&R circularly polarised laser to measure lepton polarisation. • Can improve TPOL. PPESP, RAL, May 2000

  17. TPOL PPESP, RAL, May 2000

  18. Message:eta is key input Words: K_eta is ‘analysing power’.Plot from cern test beam. Eta is a key input to polarisation measurement so very important to improve this, and do it in-situ, in real-time to follow any changes. L or R Vertical asymmetry  Polarisation From angular dependence of polarised compton scattering. • <y>L,R determined from EU - ED Cern test beam data • K determined polarisation rise-time data in ‘flat-machine’. • v(y) key input PPESP, RAL, May 2000

  19. Message: Rise-time calibration method is dependent on the machine. Words: The rise-time plot shows the natural polarising effect of the machine. Fit the rise using theoretical prediction? to extract polarisation at equilibrium and measure y up and y down to get K_eta. 0 1 2 Calibration • Currently: • Fit to rise time in `flat-machine’ gives P  extract K • Dominant uncertainty in K comes from v(y) In-situ, real-time measurement of v(y) will reduce systematic error  PPESP, RAL, May 2000

  20. Position sensitive detector • Give precise position of TPOL calorimeter in real time in situ. • Minimise systematic error by making a real-time determination ofv(y) PPESP, RAL, May 2000

  21. Message: Words: Test stand is essentially ready, just the readout to do. The silicon detector on the f/e board works. It has been read out and they’ve seen pulses. Silicon detector • Preparation & procurement of electronics for silicon detector test complete. • Test stand is ready at Imperial. • Silicon detector on the front-end board works. PPESP, RAL, May 2000

  22. Message: things change. Words: Characteristics, in particular the linearity, may change. The calibration is required to achieve the required linearity. Precise calibrate linearity. Compton photons Conversion e+, e- Silicon Position Calibration • Intense Compton beam. • Radiation hard silicon and chips. • But characteristics may change. • Need in-situ calibration. Solution: Scintillating fibre on precision table. • Periodically scan in y. • Precisely calibrate the silicon response. • Better than 20m PPESP, RAL, May 2000

  23. Message: UK contribution ismajor part of Zeus contribution to POL upgrade. Post-upgrade TPOL • Proposed Zeus UK contribution • Silicon detector & read-out. • Precision mechanical support structure for scintillating fibre. PPESP, RAL, May 2000

  24. Costing & Manpower • Responsive RA. • Design and fabricate front-end board. • 4 man months. • Provided by Imperial College. • Design and build precision mechanical items. •  man year . • Provided by Imperial College. PPESP, RAL, May 2000

  25. Words: What will probably be the definitive measurement of F2. FL measurment underway using ISR events to get the required beam energy variation. Improve statistically limited measurements. By combination of the various permutations of lepton charge and polarisation, we will be able to measure the light quark couplings to the Z0. And something which I didn`t mention, is the increased sensitivity to new physics with polarised lepton beams. And we are well-placed to make use of the Hera upgrade. Summary of PartII • Current knowledge of proton & EW physics. • Definitive F2 measurement • First measurement of xF3 at high Q2and x. • Physics after upgrade. • Improve xF3, FL,MW measurements. • Parity violation, light quark couplings, searches. • Polarimeter upgrade crucial to these physics goals. PPESP, RAL, May 2000

  26. Words: And improved detector with UK playing a vital role both in integrating the MVD into the CTD tracking environment, and ensuring sufficient precision on the polarisation measurement. Summary of Resources Requested • Continued support for Maintenance, Operation and travel for the ZEUS group. • £55k to complete the UK MVD tasks, including the greatly expanded active patch box. • £50k for the UK participation in the upgrade of the HERA polarisation measurement. PPESP, RAL, May 2000

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