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Zeus UK Status Report Part II Rod Walker Imperial College London 15th May 2000 zPhysics activities. zPost-upgrade physics opportunities with polarised.

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Presentation on theme: "Zeus UK Status Report Part II Rod Walker Imperial College London 15th May 2000 zPhysics activities. zPost-upgrade physics opportunities with polarised."— Presentation transcript:

1 Zeus UK Status Report Part II Rod Walker Imperial College London 15th May 2000 zPhysics activities. zPost-upgrade physics opportunities with polarised beams. zPolarimeter upgrade.

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

3 PPESP, RAL, May 2000 Deep inelastic scattering Neutral Current Photon/Z exchange e  p: All flavours contribute Q2Q2 Q2Q2 Charged Current W exchange `invisible`  Missing P T e + p: d, s and u, c e - p: u, c and d, s

4 PPESP, RAL, May 2000 NC cross section ze + p & e - p data. y48pb -1 e + p (94-97) y16pb -1 e - p (98-99) y  (e - p) >  (e + p) yGood agreement with SM over 6 orders of magnitude. 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. 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.

5 PPESP, RAL, May 2000 NC: d  /dx zAgreement with SM zZ  interference at High-Q 2

6 PPESP, RAL, May 2000 F2F2 z94 F 2 yQCD fits yStrong scaling violations zNew 96/97 F 2 y12  published lumi yImproved precision at high-Q 2 yExtend to higher-x at high-Q 2. 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. 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.

7 Rise of F 2 at low x measured with high precision.

8 Strong scaling violations

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

10 PPESP, RAL, May 2000 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 xF 3 at high-Q 2 and x. yPrecision comparable to first F2 extraction. yF L contribution is negligible. ySensitive to valence quarks at high-x.

11 PPESP, RAL, May 2000 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 xF 3 at high-Q 2 and x. yCan extract  s from the slope. yMuch improved precision after upgrade.

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

13 PPESP, RAL, May 2000 Normalisation:x sec at Q 2 =0 1 σ contour of χ 2 distbn zFit normalisation and shape. zDirect measurement of M w in space-like region. M w measurement

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

15 PPESP, RAL, May 2000 zParity violation in CC ySM yRH W - limit Mw>400GeV zLight quark couplings yFits to NC&CC cross sections for R&L pol. zPolarisation measurement. yRequire 1-2% precision yCurrently only 4% 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. 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. Future Physics:- Lepton Polarisation e - L p  v X e - R p  v X Large effect P

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

17 PPESP, RAL, May 2000 TPOL

18 PPESP, RAL, May 2000 L,R determined from E U - E D K  determined polarisation rise-time data in ‘flat- machine’.  v (y) key input  L or  R Vertical asymmetry  Polarisation From angular dependence of polarised compton scattering. 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. 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. Cern test beam data

19 PPESP, RAL, May 2000 Calibration zCurrently: yFit to rise time in `flat- machine’ gives P   extract K  yDominant uncertainty in K  comes from  v (y) In-situ, real-time measurement of  v (y) will reduce systematic error  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. 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. 012

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

21 PPESP, RAL, May 2000 Silicon detector zPreparation & procurement of electronics for silicon detector test complete. zTest stand is ready at Imperial. ySilicon detector on the front-end board works. 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. 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.

22 PPESP, RAL, May 2000 Silicon Position Calibration zIntense Compton beam. yRadiation hard silicon and chips. yBut characteristics may change. yNeed in-situ calibration. Solution: Scintillating fibre on precision table. yPeriodically scan in y. yPrecisely calibrate the silicon response. yBetter than 20  m Compton photons Conversion e +, e - Message: things change. Words: Characteristics, in particular the linearity, may change. The calibration is required to achieve the required linearity. Precise calibrate linearity. Message: things change. Words: Characteristics, in particular the linearity, may change. The calibration is required to achieve the required linearity. Precise calibrate linearity.

23 PPESP, RAL, May 2000 Post-upgrade TPOL Message: UK contribution is major part of Zeus contribution to POL upgrade. zProposed Zeus UK contribution ySilicon detector & read-out. yPrecision mechanical support structure for scintillating fibre.

24 PPESP, RAL, May 2000 Costing & Manpower zResponsive RA. zDesign and fabricate front-end board. y4 man months. yProvided by Imperial College. zDesign and build precision mechanical items. y  man year. yProvided by Imperial College.

25 PPESP, RAL, May 2000 Summary of PartII zCurrent knowledge of proton & EW physics. yDefinitive F 2 measurement yFirst measurement of xF 3 at high Q 2 and x. zPhysics after upgrade. yImprove xF 3, F L, M W measurements. yParity violation, light quark couplings, searches. zPolarimeter upgrade crucial to these physics goals. 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.

26 PPESP, RAL, May 2000 Summary of Resources Requested zContinued support for Maintenance, Operation and travel for the ZEUS group. z£55k to complete the UK MVD tasks, including the greatly expanded active patch box. z£50k for the UK participation in the upgrade of the HERA polarisation measurement. 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. 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.


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