1. A.K. Opper June 2004 The Q p Weak Experiment: “A Search for New Physics at the TeV Scale Via a Measurement of the Proton’s Weak Charge” 63 People at: JLab, LANL, MIT, BATES, TRIUMF, William & Mary, Univ. of Manitoba, Virginia Tech, Louisiana Tech, Caltech, Univ. of Connecticut, Univ. Nacional Autonoma de Mexico, UNBC, Univ. of New Hampshire, Ohio Univ., Mississippi State, Hampton Univ., Yerevan Physics Institute May 2000 Collaboration formed January 2002JLab Proposal Approved with ‘A’ rating January 2003Technical design review complete 2003All needed funding secured DOE/JLab, NSF & NSERC 2004Design work and prototyping 2007Goal for initial experiment installation. 1 st measurement of Q p w 10  measurement of sin 2  W running

2. A.K. Opper June 2004 Standard model predicts sin 2  w (Q) A LR  Q p W = 1 – 4 sin   W Complements APV and high energy measurements Tests consistency of SM and probes for new physics  0.3% sin 2  W  Interfere  Z0Z0 Q(GeV/c)

3. A.K. Opper June 2004 (at tree level) Q p Weak : Extract from PV Electron Scattering measures Q p EM - PC measures Q p Weak - PV M EM M NC Q p weak is a well-defined experimental observable Q p weak has a definite prediction in the electroweak Standard Model Q e weak : electron’s weak charge is measured in PV Moller scattering (E158) Interference  helicity asymmetry, A, for polarized beam A = =  + -  -  + +  - ______

4. A.K. Opper June 2004 Nucleon Structure Contributions to the Asymmetry hadronic: (31% of asymmetry) - contains G  E,M G Z E,M constrained by HAPPEX, G 0, MAMI PVA4 axial: (4% of asymmetry) - contains G e A, has large electroweak radiative corrections. Will be constrained by G 0 and SAMPLE Expected constraints on A hadronic from currently running experiments Quadrature sum of expected A hadronic and A axial errors contributes ~2% to error on Q p W ---- Range of possible strange quark form factor contribution Measure not calculate! = -0.28 ppm

5. A.K. Opper June 2004 Energy Scale of an “Indirect” Search for New Physics Parameterize New Physics contributions in electron-quark Lagrangian A 4% Q p Weak measurement probes for new physics at energy scales to: g: coupling constant  : mass scale TeV discovery potential unmatched until the LHC turns on

6. A.K. Opper June 2004 “Running of sin 2  W ” in the Standard Model At Q = 0.03 GeV/c: * Q p weak (semi-leptonic) and * SLAC E158 (pure leptonic) * different sensitivities to SM extensions Electroweak radiative corrections  sin 2  W varies with Q +  + Erler et al., Phys. Rev D 68, 016006  (Q p weak ) = 4%  (sin 2  W ) = 0.3%

7. A.K. Opper June 2004 Q p weak (semi-leptonic) and E158 (pure leptonic) together make a powerful program to search for and identify new physics. Qweak measurement will provide a stringent stand alone constraint on Lepto-quark based extensions to the SM. JLab Qweak SLAC E158 E158 Run I hep- ex/0312035 ± 0.012 (projected final) (proposed) -

8. A.K. Opper June 2004 Illustration of the Q p Weak Experiment Incident beam energy: 1.165 GeV Beam Current: 180 μA Beam Polarization: ~80% LH 2 target power: 2.5 KW Central scattering angle: 8° ±2 Phi Acceptance: 50% of 2 Average Q²: 0.028 GeV 2 Acceptance averaged asymmetry:–0.28 ppm Integrated Rate (all sectors): 5.2 GHz Integrated Rate (per detector): 650 MHz Experiment Parameters (integration mode) Polarized Electron Beam 35cm Liquid Hydrogen Target Collimator with 8 openings θ= 8° ± 2° Region I GEM Detectors Region II Drift Chambers Toroidal Magnet Region III Drift Chambers Elastically Scattered Electron Eight Fused Silica (quartz) Čerenkov Detectors Luminosity Monitors

9. A.K. Opper June 2004 Collimator Design θ= 8°±2° (azimutal) φ= ±11° (polar, per octant) Q²= 0.028 GeV² Rate = 650 MHz/octant Kinematical acceptance: Target Collimator 1 Defining aperture Electron beam Collimator 2 (clean up) Main Torus Magnet Material: leaded brass (25% lead,70% Cu, 5% Sn)  required survey accuracy: ~ 1 mrad (~ 1 mm for alignment of precision collimators with respect to target) Shielding Wall

10. A.K. Opper June 2004 Q weak Toroidal Magnet beam scattered e envelope 8 toroidal coils, 4.5m long along beam Resistive, based on BLAST Pb shielding between coils Coil holders & frame all Al  B  dl ~ 0.7 T-m ~9500 A

11. A.K. Opper June 2004 Separated Inelastic & Photon Background Inelastics Elastic Photons Q p Weak spectrometer optics from GEANT simulation. Double collimator.  clean separation of elastics from inelastics & ’s at focal plane At Detector(with Čerenkov cut): Elastic e-p rate = 650 MHz/octant Inelastic rate = 30 KHz/octant  Inelastic contamination ~ 0.005% Photon rate = 42 KHz/octant  Photon contamination ~ 0.007%

12. A.K. Opper June 2004 View Along Beamline of Q p Weak Apparatus with Simulated Events Black region in center is Pb shielding

13. A.K. Opper June 2004 The Q p weak Detector and Electronics System Focal plane detector requirements: Radiation hardness (expect > 300 kRad). Insensitivity to background , n, . Operation at counting statistics. Electronics (LANL/TRIUMF/UMan design): Normally operates in integration mode. Will have connection for pulse mode. Low electronic noise contribution compared to counting statistics. 1 MHz 16 bit ADC will allow for over sampling.  Fused Silica (synthetic quartz) Cerenkov detector Use 15 cm x 200 cm x 2.5 cm quartz bars read out at both ends by S20 photocathode PMTs (expect ~ 100 pe/event), 5 inch n=1.47,  Cerenkov = 47° total internal reflection  tir =43° reflectivity = 0.997

14. A.K. Opper June 2004 Position dependence of the # of pe’s on each of the PMTs. Simulation includes the full weighted cross-section & spectrometer optics. Light Collection in 12 cm x 2.54 cm x 2 m Quartz Cerenkov Detectors Rotate Detector 12.5 o Length Width

15. A.K. Opper June 2004 Detector Performance prototype sample tested in beam (G0) Alignment within a few degrees was critical In a quartz TIR detector the angle rather than position is the right variable. Top window: bar roughly perpendicular to beam Bottom Window: bar tilted 5 degrees to favor bottom PMT

16. A.K. Opper June 2004 The Q p weak 2200 Watt Liquid Hydrogen Target Target: Similar in design to SAMPLE & G 0 targets  longitudinal liquid flow  high stream velocity achieved with perforated, tapered “windsock” Q p Weak Target parameters/requirements: Length = 35 cm Beam current = 180 A Beam power = 2500 W Raster size ~4 mm x ~4 mm square Flow velocity > 700 cm/s Density fluctuations (at 15 Hz) < 5x10 -5 G 0 target

17. A.K. Opper June 2004 G0 Target Cell & Manifold cold helium gas (dropped for Q weak ) (enlarged for Q weak ) perforated windsock/flow diverter exit window (75 µ)

18. A.K. Opper June 2004 Determination of Average Q 2 Need to know  / ~ 0.7%  requires survey accuracy ~ 1 mrad (~ 1 mm for alignment of precision collimator with respect to target) Expected Q 2 distribution Calibration measurements at low beam current, event-by-event made with 1 set of GEMs and 2 sets of Drift Chambers to: Measure shape of focal plane distribution. Measure position-dependent detector efficiency. Compared measured Q 2 distribution to Monte-Carlo

19. A.K. Opper June 2004 Measurement of the Signal-to-Background Dilution Factor TOF Measurement: Beam: 2 MHz pulse rate & low current PMT anode  1 GHz transient digitizer TOF distribution of the anode current  events of interest are in prompt peak PMT Anode  1 GHz 8 bit transient digitizer Decompose Prompt Peak: Insert GEMs, drift chambers & scintillator. Run at low beam current (“pulse mode”) in coincidence. Scintillator allows for neutral rejection. Tracking traces origin of scattered particles. Pions Neutrons Prompt: Elastic e - +  0   + brems. 

20. A.K. Opper June 2004 Basel/Hall C Møller Existing Hall C Møller can do 1% (stat) in a few minutes With care, absolute accuracy <1% Limitations -I Max ~ 10 A At higher currents the Fe target depolarizes. -Measurement is destructive Goals for an upgraded Møller -Measure P beam at 100 A or higher, quasi-continuously -Trick: kicker + strip or wire target (looks promising) Plus new HallC Compton polarimeter -Measure P beam at 100 A or higher, quasi-continuously

21. A.K. Opper June 2004 Anticipated Uncertainties on Q p Weak  Q p weak /Q p weak Possible Improvements Statistical (2200 hours) 2.8%  2.5% Systematic: Hadronic structure corrections 2.0%  1.5% Beam polarization 1.4%  1.0% Average Q 2 determination 1.0% Helicity-correlated Beam Properties 0.6% Uncertainty in Inelastic contamination0.2% Al Target window Background <1.0%  0.3% (Be) Total systematic 2.9% 2.2% ______________________________________________________________________ Total 4.0% 3.3% Bottom line: Precision measurement of the running of sin 2  W requires effort but no new technology! Additional uncertainty associated with QCD corrections (from extraction of sin 2  W ): raises sin2W / sin2W from 0.2% to 0.3%.

22. A.K. Opper June 2004 Status Qweak: Summary Broad community performing precision measurements to test SM – including Qweak. Capital funding (NSF + university matching, JLAB, NSERC) secured JLab  “infrastructure” - AC, DC, cooling water, installation manpower, recycle G 0 beamline systems.... Magnet procurements during FY-04. Detector prototyping begun. On track for a ~3.5 year construction effort with possible installation in 2007. Strong scientific support for the measurement. Nuclear theory (Ramsey-Musolf, Erler, Haxton, Donnelly, Friar,…) and high energy theory (W. Marciano & P. Lanacker). Collaboration healthy and growing -- addition of MIT/Bates Staff and the hiring of postdocs by a number of groups. Investigating possibility of better than a 4% measurement of Qweak.

23. A.K. Opper June 2004 Qweak Collaboration Spokespersons Bowman, J. David - Los Alamos National Laboratory Carlini, Roger (Principal Investigator) - Thomas Jefferson National Accelerator Facility Finn, J. Michael - College of William and Mary Kowalski, Stanley - Massachusetts Institute of Technology Page, Shelley - University of Manitoba Qweak Collaboration Members Armstrong, David - College of William and Mary Averett, Todd - College of William and Mary Birchall, James - University of Manitoba Botto, Tancredi - Massachusetts Institute of Technology Bruell, Antje - Thomas Jefferson National Accelerator Facility Chattopadhyay, Swapan - Thomas Jefferson National Accelerator Facility Davis, Charles - TRIUMF Doornbos, J. - TRIUMF Dow, Karen - Massachusetts Institute of Technology Dunne, James - Mississippi State University Ent, Rolf - Thomas Jefferson National Accelerator Facility Erler, Jens - University of Mexico Falk, Willie - University of Manitoba Farkhondeh, Manouchehr - Massachusetts Institute of Technology Forest, Tony - Louisiana Tech University Franklin, Wilbur - Massachusetts Institute of Technology Gaskell, David - Thomas Jefferson National Accelerator Facility Grimm, Klaus - College of William and Mary Hagner, Caren - Virginia Polytechnic Inst. & State Univ. Hersman, F. W. - University of New Hampshire Holtrop, Maurik - University of New Hampshire Johnston, Kathleen - Louisiana Tech University Jones, Richard - University of Connecticut Joo, Kyungseon - University of Connecticut Keppel, Cynthia - Hampton University Khol, Michael - Massachusetts Institute of Technology Korkmaz, Elie - University of Northern British Columbia Lee, Lawrence - TRIUMF Liang, Yongguang - Ohio University Lung, Allison - Thomas Jefferson National Accelerator Facility Mack, David - Thomas Jefferson National Accelerator Facility Majewski, Stanislaw - Thomas Jefferson National Accelerator Mammei, Juliette - Virginia Polytechnic Inst. & State Univ. Mammei, Russell - Virginia Polytechnic Inst. & State Univ. Mitchell, Gregory - Los Alamos National Laboratory Mkrtchyan, Hamlet - Yerevan Physics Institute Morgan, Norman - Virginia Polytechnic Inst. & State Univ. Opper, Allena - Ohio University Penttila, Seppo - Los Alamos National Laboratory Pitt, Mark - Virginia Polytechnic Inst. & State Univ. Poelker, B. (Matt) - Thomas Jefferson National Accelerator Facility Porcelli, Tracy - University of Northern British Columbia Ramsay, William - University of Manitoba Ramsey-Musolf, Michael - California Institute of Technology Roche, Julie - Thomas Jefferson National Accelerator Facility Simicevic, Neven - Louisiana Tech University Smith, Gregory - Thomas Jefferson National Accelerator Facility Smith, Timothy - Dartmouth College Suleiman, Riad - Massachusetts Institute of Technology Taylor, Simon - Massachusetts Institute of Technology Tsentalovich, Evgeni - Massachusetts Institute of Technology van Oers, W.T.H. - University of Manitoba Wells, Steven - Louisiana Tech University Wilburn, W.S. - Los Alamos National Laboratory Wood, Stephen Thomas - Jefferson National Accelerator Facility Zhu, Hongguo - University of New Hampshire Zorn, Carl - Thomas Jefferson National Accelerator Facility Zwart, Townsend - Massachusetts Institute of Technology JLab E02-020: “Q weak ” A Search for Physics at the TeV Scale via a Measurement of the Proton’s Weak Charge