63 People at:

1. The QpWeak Experiment:“A Search for New Physics at the TeV Scale Via a Measurement of the Proton’s Weak Charge” • 1st measurement of Qpw • 10 s measurement of sin2qW running May 2000 Collaboration formed January 2002 JLab Proposal Approved with ‘A’ rating January 2003 Technical design review complete 2003 All needed funding secured DOE/JLab, NSF & NSERC 2004 Design work and prototyping 2007 Goal for initial experiment installation. 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 PhysicsInstitute

2. Z0  Interfere  • Standard model predicts sin2qw(Q) • ALR a QpW= 1 – 4 sin2qW • Complements APV and high energy measurements • Tests consistency of SM and probes for new physics  0.3% sin2qW Q(GeV/c)

3. Qpweak is a well-defined experimental observable • Qpweak has a definite prediction in the electroweak Standard Model QpWeak : Extract from PV Electron Scattering Interference  helicity asymmetry, A, for polarized beam MEM MNC measures Qp EM - PC measures QpWeak - PV s+ - s- s+ + s- ______ A = = (at tree level) Qeweak : electron’s weak charge is measured in PV Moller scattering (E158)

4. Nucleon Structure Contributions to the Asymmetry = -0.28 ppm hadronic: (31% of asymmetry) - contains GE,M GZE,M constrained by HAPPEX, G0, MAMI PVA4 axial: (4% of asymmetry) - contains GeA, has large electroweak radiative corrections. Will be constrained by G0 and SAMPLE Quadrature sum of expected Ahadronic and Aaxial errors contributes ~2% to error on QpW Expected constraints on Ahadronic from currently running experiments ---- Range of possible strange quark form factor contribution Measure not calculate!

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

6. Electroweak radiative corrections  sin2W varies with Q +  + “Running of sin2W” in the Standard Model At Q = 0.03 GeV/c: * Qpweak (semi-leptonic) and * SLAC E158 (pure leptonic) * different sensitivities to SM extensions D(Qpweak) = 4% D(sin2qW) = 0.3% Erler et al., Phys. Rev D 68, 016006

7. JLab Qweak SLAC E158 - E158 Run I hep-ex/0312035 ± 0.012 (projected final) (proposed) • Qpweak (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.

8. Elastically Scattered Electron Luminosity Monitors Region III Drift Chambers Toroidal Magnet Region II Drift Chambers Region I GEM Detectors Eight Fused Silica (quartz) Čerenkov Detectors Collimator with 8 openings θ= 8° ± 2° 35cm Liquid Hydrogen Target Polarized Electron Beam Illustration of the QpWeak Experiment Experiment Parameters (integration mode) Incident beam energy: 1.165 GeV Beam Current: 180 μA Beam Polarization: ~80% LH2 target power: 2.5 KW Central scattering angle: 8° ±2 Phi Acceptance: 50% of 2p Average Q²: 0.028 GeV2 Acceptance averaged asymmetry: –0.28 ppm Integrated Rate (all sectors): 5.2 GHz Integrated Rate (per detector): 650 MHz

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

10. scattered e envelope Qweak Toroidal Magnet • 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 beam

11. Separated Inelastic & Photon Background Inelastics Elastic Photons • QpWeak 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. View Along Beamline of QpWeak Apparatus with Simulated Events Black region in center is Pb shielding

13. The Qpweak Detector and Electronics System • Focal plane detector requirements: • Radiation hardness (expect > 300 kRad). • Insensitivity to background , n, . • Operation at counting statistics. •  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 • 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.

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

15. Detector Performanceprototype 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. G0 target The Qpweak 2200 Watt Liquid Hydrogen Target • Target: • Similar in design to SAMPLE & G0 targets •  longitudinal liquid flow •  high stream velocity achieved with perforated, tapered “windsock” • QpWeak 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

17. G0 Target Cell & Manifold exit window (75 µ) (dropped for Qweak) cold helium gas (enlarged for Qweak) perforated windsock/flow diverter

18. Determination of Average Q2 Expected Q2 distribution Need to know D<Q2>/<Q2> ~ 0.7%  requires survey accuracy ~ 1 mrad (~ 1 mm for alignment of precision collimator with respect to target) • 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 Q2 distribution • to Monte-Carlo

19. 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 Prompt: Elastic e- + 0   + brems.  Neutrons Pions • 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.

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

21. Anticipated Uncertainties on QpWeak •  Qpweak/QpweakPossible Improvements • Statistical (2200 hours) 2.8%  2.5% • Systematic: • Hadronic structure corrections 2.0%  1.5% • Beam polarization 1.4%  1.0% • Average Q2 determination 1.0% • Helicity-correlated Beam Properties 0.6% • Uncertainty in Inelastic contamination 0.2% • Al Target window Background <1.0%  0.3% (Be) • Total systematic 2.9% 2.2% • ______________________________________________________________________ • Total 4.0% 3.3% Additional uncertainty associated with QCD corrections (from extraction of sin2W): raises sin2W / sin2W from 0.2% to 0.3%. Bottom line: Precision measurement of the running of sin2qW requires effort but no new technology!

22. 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 G0 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. JLab E02-020: “Qweak” A Search for Physics at the TeV Scale via a Measurement of the Proton’s Weak Charge 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