M. Pitt, Virginia Tech LANL Seminar, 2005 The Q p weak Experiment – A Search for New Physics at the TeV Scale Mark Pitt Virginia Tech Brief review of recent and planned low energy neutral current Standard Model tests Overview and status report of an approved JLAB Standard Model test – The Q p weak Experiment Brief review of most recent results on strange electric and magnetic form factors of the nucleon

M. Pitt, Virginia Tech LANL Seminar, 2005 What about the running of sin 2  W ? Running coupling constants in QED and QCD QED (running of  ) ss QCD(running of  s ) 137 

M. Pitt, Virginia Tech LANL Seminar, 2005 “Running of sin 2  W ” in the Electroweak Standard Model Electroweak radiative corrections  sin 2  W varies with Q + +  All “extracted” values of sin 2  W must agree with the Standard Model prediction or new physics is indicated.

M. Pitt, Virginia Tech LANL Seminar, 2005 Why are Precision Measurements far Below the Z-pole Sensitive to New Physics? Precision measurements well below the Z-pole have more sensitivity (for a given experimental precision) to new types of tree level physics, such as additional heavier Z’ bosons.

M. Pitt, Virginia Tech LANL Seminar, 2005 Low Energy Weak Neutral Current Standard Model Tests These three types of experiments are a complementary set for exploring new physics possibilities well below the Z pole. Low energy weak charge “triad” (M. Ramsey-Musolf) probed in weak neutral current experiments SLAC E158: parity-violating Moller scattering e + e  e + e Cesium Atomic Parity Violation: primarily sensitive to neutron weak charge JLAB Q p weak : parity-violating e-p elastic scattering e + p  e + p

M. Pitt, Virginia Tech LANL Seminar, 2005 Q e weak : Electron Weak Charge – SLAC E158 Experiment Parity-violating Moller scattering Q 2 ~.026 GeV 2  ~ 4 – 7 mrad E ~ 48 GeV at SLAC End Station A e + e  e + e Final results: hep-ex/ A PV = -131  14 (stat)  10 (syst) ppb sin 2  eff (Q 2 =0.026 GeV 2 ) = ± ± Running of sin 2  eff established at 6  level in pure leptonic sector

M. Pitt, Virginia Tech LANL Seminar, 2005 Atomic Parity Violation in the Cesium Atom (B x E)   PNC expt. + atomic theory: Q W ( 133 Cs) = ± (0.29) expt ± (0.36) theor Standard Model prediction: Q W ( 133 Cs) = ± (0.03) after a turbulent 2-year period as the atomic theory was successively improved. Boulder 133Cs experiment (Wood et al., Science 275, 1759 (1997)): Measures modification of neutral weak current to the S-P Stark mixing in an applied electric field Isolate the parity non-conserving piece (PNC) with five different reversals

M. Pitt, Virginia Tech LANL Seminar, 2005 Future Directions for PV Moller and APV e2ePV: Parity-Violating Moller scattering at 12 GeV JLAB (Mack, Reimer, et al.) ● Paris group (Bouchiat, et al.): more precise Cs APV ● Seattle group (Fortson, et al.): single trapped Ba + APV 6S 1/2  5D 3/2 ● Berkeley group (Budker, et al.): isotope ratios in Yb APV ● Stony Brook/Maryland group (Orozco, et al.): isotope ratios in Fr APV Note: isotope ratios can eliminate large atomic structure theory uncertainties Atomic Parity Violation Future Directions Achieve Moller focus with long, narrow superconducting toroidal magnet, Radiation hard detector package E = 12 GeV Q 2 =.008 GeV 2,  ~ o, A PV = - 40 ppb In 4000 hours, could determine Q e W to 2.5% (compare to 12.4% for E158)

M. Pitt, Virginia Tech LANL Seminar, 2005 Potential of e2ePV: Parity-Violating Moller at 12 GeV JLAB A 12 GeV Moller experiment could be comparable to the world’s best weak mixing angle measurements at the Z pole (~ 0.1%).

M. Pitt, Virginia Tech LANL Seminar, 2005 “Running of sin 2  W ” : Current Status and Future Prospects present: “d-quark dominated” : Cesium APV (Q A W ): SM running verified at ~ 4  level “pure lepton”: SLAC E158 (Q e W ): SM running verified at ~ 6  level future: “u-quark dominated” : Q weak (Q p W ): projected to test SM running at ~ 10  level “pure lepton”:12 GeV e2ePV (Q e W ): projected to test SM running at ~ 25  level

M. Pitt, Virginia Tech LANL Seminar, 2005 The Q p weak Experiment: A Search for New TeV Scale Physics via a Measurement of the Proton’s Weak Charge Measure: Parity-violating asymmetry in e + p elastic scattering at Q 2 ~ 0.03 GeV 2 to ~4% relative accuracy at JLab Extract: Proton’s weak charge Q p weak ~ 1 – 4 sin 2  W to get ~0.3% on sin 2  W at Q 2 ~ 0.03 GeV 2 tests “running of sin 2  W ” from M 2 Z to low Q 2 sensitive to new TeV scale physics

M. Pitt, Virginia Tech LANL Seminar, 2005 The Q p Weak Experiment JLAB E02-020: “A Search for new physics beyond the Standard Model at the TeV Scale” The Q p Weak Experiment JLAB E02-020: “A Search for new physics beyond the Standard Model at the TeV Scale” The Collaboration D. Armstrong, T. Averett, J. Birchall, T. Botto, J. D. Bowman, P. Bosted, A. Bruell, R. Carlini (PI), S. Chattopadhay, C. Davis, J. Doornbos, K. Dow, J. Dunne, R. Ent, J. Erler, W. Falk, M. Farkhondeh, J.M. Finn, T. Forest, W. Franklin, D. Gaskell, K. Grimm, F. W. Hersman, M. Holtrop, K. Johnston, R. Jones, K. Joo, C. Keppel, M. Khol, E. Korkmaz, S. Kowalski, L. Lee, Y. Liang, A. Lung, D. Mack, S. Majewski, J. Martin, J. Mammei, R. Mammei, G. Mitchell, H. Mkrtchyan, N. Morgan, A. Opper, S.A. Page, S. Penttila, M. Pitt, B. (Matt) Poelker, T. Porcelli, W. Ramsay, M. Ramsey-Musolf, J. Roche, N. Simicevic, G. Smith (PM), T. Smith, R. Suleiman, S. Taylor, E. Tsentalovich, W.T.H. van Oers, S. Wells, W.S. Wilburn, S. Wood, H. Zhu, C. Zorn, T. Zwart The Institutions JLab, LANL, MIT, TRIUMF, William & Mary, Univ. of Manitoba, Virginia Tech, Louisiana Tech, Univ. of Connecticut, Univ. Nacional Autonoma de Mexico, Univ. of Northern British Columbia, Univ. of New Hampshire, Ohio Univ., Mississippi State, Hampton Univ., Yerevan Physics Institute May 2000 Collaboration formed July 2001 JLab Letter of Intent December 2001 JLab Proposal Submitted January 2002 JLab Proposal Approved with ‘A’ rating January 2003 Technical design review completed, Funding approved by to DOE, NSF & NSERC January 2005JLAB Jeopardy Proposal approved with ‘A’ rating

M. Pitt, Virginia Tech LANL Seminar, 2005 Jefferson Lab in Newport News, Virginia CEBAF: CW electron accelerator, energies up to 6 GeV

M. Pitt, Virginia Tech LANL Seminar, ’s: e + 9 Be (QE) A ~ 10 ppm Mainz e + 12 C (elastic) A ~ 1 ppm MIT-Bates Goal: Standard Model test 90’s, 00’s: SAMPLE HAPPEX e + p (elastic) A ~ 2 – 50 ppm G 0 MAMI PV-A4 e + d (QE) Goal: Assume Standard Model is correct, measure strange form factors 70’s: e + d (DIS) A ~ 100 ppm SLAC E122 (Prescott, et al) Goal: measure sin 2 θ W = / most precise measurement at that time Brief History of Parity Violating Electron-Nucleon Scattering 00’s: Q p weak A ~ 0.3 ppm Goal:  sin 2 θ W )/sin 2  W ~ 0.3% at low Q 2 Standard Model test

M. Pitt, Virginia Tech LANL Seminar, 2005 (at tree level) Q p weak : Extract from Parity-Violating Electron Scattering measures Q p – proton’s electric charge measures Q p weak – proton’s weak charge M EM M NC As Q 2  0 Q p weak is a well-defined experimental observable Q p weak has a definite prediction in the electroweak Standard Model

M. Pitt, Virginia Tech LANL Seminar, 2005 How to Measure the Neutral weak form factors

M. Pitt, Virginia Tech LANL Seminar, 2005 Parameterize New Physics contributions in electron-quark Lagrangian A 4% Q p Weak measurement probes with 95% confidence level for new physics at energy scales to: g: coupling constant,  : mass scale The TeV discovery potential of weak charge measurements will be unmatched until LHC turns on. If LHC uncovers new physics, then precision low Q 2 measurements will be needed to determine charges, coupling constants, etc. Energy Scale of an “Indirect” Search for New Physics

M. Pitt, Virginia Tech LANL Seminar, 2005 Impact of Q p Weak “Model-independent Semi-Leptonic Analysis” Effective electron-quark neutral current Lagrangian: Large ellipse (existing data): SLAC e-D (DIS) MIT-Bates 12 C (elastic) Cesium APV Red ellipse: Impact of Q p Weak measurement (centroid assumes agreement with standard model) Why so much better? precision & complementarity of Q p W measurement  C 1u  C 1u (exp)  C 1u (SM)  C 1d  C 1d (exp)  C 1d (SM)

M. Pitt, Virginia Tech LANL Seminar, 2005 JLab Qweak Run I + II + III (preliminary) ±0.006 (proposed) - Qweak measurement will provide a stringent stand alone constraint on Lepto-quark based extensions to the SM. Q p weak (semi-leptonic) and E158 (pure leptonic) together make a powerful program to search for and identify new physics. SLAC E158 Q p weak & Q e weak – Complementary Diagnostics for New Physics Erler, Kurylov, Ramsey-Musolf, PRD 68, (2003)

M. Pitt, Virginia Tech LANL Seminar, 2005 R parity (B-L conservation) RPC SUSY occurs only at loop level RPV SUSY occurs at tree level Relative Shifts in Proton and Electron Weak Charges due to SUSY Effects Erler, Ramsey-Musolf, Su hep-ph/

M. Pitt, Virginia Tech LANL Seminar, 2005 Overview of the Q p Weak Experiment Incident beam energy: GeV Beam Current: 180 μA Beam Polarization: 85% LH 2 target power: 2.5 KW Central scattering angle: 8.4° ± 3° Phi Acceptance: 53% of 2 Average Q²: GeV 2 Acceptance averaged asymmetry:–0.29 ppm Integrated Rate (all sectors): 6.4 GHz Integrated Rate (per detector): 800 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

M. Pitt, Virginia Tech LANL Seminar, 2005   A phys /A phys  Q p weak /Q p weak Statistical (2200 hours production) 1.8% 2.9% Systematic: Hadronic structure uncertainties % Beam polarimetry 1.0% 1.6% Absolute Q 2 determination 0.5% 1.1% Backgrounds 0.5% 0.8% Helicity-correlated Beam Properties 0.5%0.8% _________________________________________________________ Total 2.2% 4.1%   A phys /A phys  Q p weak /Q p weak Statistical (2200 hours production) 1.8% 2.9% Systematic: Hadronic structure uncertainties % Beam polarimetry 1.0% 1.6% Absolute Q 2 determination 0.5% 1.1% Backgrounds 0.5% 0.8% Helicity-correlated Beam Properties 0.5%0.8% _________________________________________________________ Total 2.2% 4.1% (Erler, Kurylov, Ramsey-Musolf, PRD 68, (2003)) Q p W =  theoretically 0.8% error comes from QCD uncertainties in box graphs, etc. (Erler, Kurylov, Ramsey-Musolf, PRD 68, (2003)) Q p W =  theoretically 0.8% error comes from QCD uncertainties in box graphs, etc. Anticipated Q p Weak Uncertainties 4% error on Q p W corresponds to ~0.3% precision on sin 2  W at Q 2 ~ 0.03 GeV 2

M. Pitt, Virginia Tech LANL Seminar, 2005 Constraints on A hadronic from other Measurements Quadrature sum of expected  A hadronic = 1.5% and  A axial = 1.2% errors contribute ~1.9% to error on Q p W hadronic: (31% of asymmetry) - contains G  E,M G Z E,M Constrained by HAPPEX, G 0, MAMI PVA4 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. Constrained by G 0 and SAMPLE axial: (4% of asymmetry) - contains G e A, has large electroweak radiative corrections. Constrained by G 0 and SAMPLE Nucleon Structure Contributions to the Asymmetry

M. Pitt, Virginia Tech LANL Seminar, 2005 What role do strange quarks play in nucleon properties? u u d u u s s valence quarks “non-strange” sea (u, u, d, d) quarks “strange” sea (s, s) quarks Momentum: Spin: Mass: Charge and current: There has been a decade long effort to measure the vector strange form factors. proton gluon

M. Pitt, Virginia Tech LANL Seminar, 2005 Strange Vector Form Factors – G E s and G M s The strange vector form factors measure the contribution of the strange quark sea to the electromagnetic properties of the nucleon. Strange electric form factor: measures the contribution of the strange quark sea to the nucleon’s spatial charge distribution. Strange magnetic form factor: measures the contribution of the strange quark sea to the nucleon’s spatial magnetization distribution.

M. Pitt, Virginia Tech LANL Seminar, 2005 Parity Violating Electron Scattering - Probe of Neutral Weak Form Factors polarized electrons, unpolarized target At a given Q 2 decomposition of G s E, G s M, G e A Requires 3 measurements: Forward angle e + p (elastic) Backward angle e + p (elastic) Backward angle e + d (quasi-elastic) Strange electric and magnetic form factors, + axial form factor

M. Pitt, Virginia Tech LANL Seminar, 2005 Results of Strange Form Factor Measurements Measurements at Q 2 = 0.1 GeV 2 MIT-Bates (SAMPLE) JLAB (HAPPEx) Mainz (A4) from G 0 and Happex at JLAB

M. Pitt, Virginia Tech LANL Seminar, 2005 Strange Form Factor Measurements - speculation The current strange form factor data indicates non-zero values at the ~ 2 σ level. If the true values are anywhere near the central values, these are not small effects; ie. experiment has not yet ruled out potentially large strange quark sea contributions to the nucleon’s electromagnetic properties. Results of global fits to all data (need to multiply by -1/3 to get contribution) More data coming in from JLAB and Mainz from D. Beck

M. Pitt, Virginia Tech PAVI 2002, Mainz Region 3: Vertical Drift chambers Region 2: Horizontal drift chamber location Region 1: GEM Gas Electron Multiplier Quartz Cherenkov Bars (insensitive to non-relativistic particles) Collimator System Mini-torus QTOR Magnet Trigger Scintillator Lumi Monitors e - beam The Qweak Apparatus (Calibration Mode Only - Production & Calibration Modes) E beam = GeV I beam = 180 μ A Polarization ~85% Target = 2.5 KW

M. Pitt, Virginia Tech LANL Seminar, toroidal coils, 4.5m long along beam Resistive, similar to BLAST magnet Pb shielding between coils Coil holders & frame all Al  B  dl ~ 0.7 T-m bends elastic electrons ~ 10 o current ~ 9500 A Status:  coils being wound in France  support stand designed, out for bid Q p Weak Toroidal Magnet - QTOR

M. Pitt, Virginia Tech LANL Seminar, 2005 View Along Beamline of Q p Weak Apparatus - Simulated Events Central scattering angle: ~8° ± 2 Phi Acceptance: > 50% of 2  Average Q²: GeV 2 Acceptance averaged asymmetry: –0.29 ppm Integrated Rate (per detector): ~801 MHz Inelastic/Elastic ratio: ~0.026% Central scattering angle: ~8° ± 2 Phi Acceptance: > 50% of 2  Average Q²: GeV 2 Acceptance averaged asymmetry: –0.29 ppm Integrated Rate (per detector): ~801 MHz Inelastic/Elastic ratio: ~0.026% Very clean elastic separation! rectangular quartz bar; 18 cm wide X 2 meters long rectangular quartz bar; 18 cm wide X 2 meters long Inelastic/Elastic Separation in Q p Weak

M. Pitt, Virginia Tech LANL Seminar, 2005 Focal plane detector requirements: Insensitivity to background , n, . Radiation hardness (expect > 300 kRad). Operation at counting statistics. Fused Silica (synthetic quartz) Cerenkov detector. Plan to use 18 cm x 200 cm x 1.25 cm quartz bars read out at both ends by 5 inch S20 photocathode PMTs (expect ~ 100 pe/event) n =1.47,  Cerenkov =47°, total internal reflection  tir =43° reflectivity = Electronics (LANL/TRIUMF design): Normally operates in integration mode. Will have connection for pulse mode. Low electronic noise contribution. compared to counting statistics. 18 bit ADC will allow for 4X over sampling. The Q p Weak Detector and Electronics System

M. Pitt, Virginia Tech LANL Seminar, 2005 Target Concept: Similar in design to SAMPLE and G 0 targets  longitudinal liquid flow  high stream velocity achieved with perforated, tapered “windsock” Target Concept: Similar in design to SAMPLE and 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 Power = 2200 W beam W heater Raster size ~4 mm x ~4 mm square Flow velocity > 700 cm/s Density fluctuations (at 15 Hz) < 5x10 -5 Q p Weak Target parameters/requirements: Length = 35 cm Beam current = 180  A Power = 2200 W beam W heater Raster size ~4 mm x ~4 mm square Flow velocity > 700 cm/s Density fluctuations (at 15 Hz) < 5x10 -5 The Q p Weak Liquid Hydrogen Target

M. Pitt, Virginia Tech LANL Seminar, 2005 Construct target that does not “boil" at a level << 50ppm/pulse pair level (assuming a 30Hz helicity reversal). Options: large raster size, faster pump speed, better cooled windows.... Use Luminosity monitors to normalize experiment instead of beam current. Assume “boiling” is not a resonant phenomena and “noise” is the result of small “bubbles” formed along the target length being ejected from the beam region. Decrease relative contribution of “boiling” by increasing the reversal/data readout rate. noise/pulse pair decreases as the reversal/readout frequency is raised. Target starts to appear as “solid” w.r.t. any single asymmetry calculation. Limiting the Target “boiling noise” Contribution

M. Pitt, Virginia Tech LANL Seminar, 2005 photocathode NF 3 Laser Cs anode e kV HV insulator NEG pumps Strained GaAs in Gun2 (“old” material) ~ 75% Polarized Strained-superlattice GaAs In Gun3 (“new” material) ~ 85% Polarized NEG-coated Beamline The polarized electrons are generated by photoemission from a GaAs semiconductor with polarized laser light Polarized Electron Guns at JLab

M. Pitt, Virginia Tech LANL Seminar, 2005  P = P + – P - Y = Detector yield (P = beam parameter ~energy, position, angle, intensity) Example: Typical goals for run-averaged beam properties Intensity: Position: keep small with feedback and careful setup keep small with symmetrical detector setup Helicity Correlated Beam Properties: False Asymmetry Corrections

M. Pitt, Virginia Tech LANL Seminar, 2005 Luminosity monitor  Symmetric array of 8 quartz Cerenkov detectors instrumented with rad hard PMTs operated in “vacuum photodiode mode” & integrating readout at small  (~ 0.8  ). Low Q 2, high rates ~29 GHz/octant. Expected signal components: 12 GHz e-e Moeller, 11 GHz e-p elastic, EM showers 6 GHz. Expected lumi monitor asymmetry << main detector asymmetry. Expected lumi monitor statistical error ~ (1/6) main detector statistical error. Useful for:  Sensitive check on helicity-correlated beam parameter corrections procedure.  Regress out target density fluctuations. The Q p Weak Luminosity Monitor

M. Pitt, Virginia Tech LANL Seminar, 2005 Region 3: Vertical Drift chambers Region 2: Horizontal drift chamber location Region 1: GEM Gas Electron Multiplier Quartz Cherenkov Bars (insensitive to non-relativistic particles) Trigger Scintillator e - beam Expected Q 2 distribution Region chambers --> determine value of Q 2 Region 3 chamber --> efficiency map of quartz detectors Q 2 Determination Use low beam current (~ few nA) to run in “pulse counting” mode with a tracking system to determine the “light-weighted” Q 2 distribution.

M. Pitt, Virginia Tech LANL Seminar, 2005 Hall C has existing ~1% precision Moller polarimeter Present limitations: -I Max ~ 10  A. -At higher currents the Fe target depolarizes. -Measurement is destructive Plan to upgrading Møller: -Measure P beam at 100  A or higher, quasi-continuously -Trick: kicker + strip or wire target (early tests look promising – tested up to 40  A so far) Schematic of planned new Hall C Compton polarimeter. Precision Polarimetry

M. Pitt, Virginia Tech LANL Seminar, 2005 Completed low energy Standard Model tests are consistent with Standard Model “running of sin 2  W ” SLAC E158 (running verified at ~ 6  level) - leptonic Cs APV (running verified at ~ 4  level ) – semi-leptonic, “d-quark dominated” Upcoming Q p W Experiment Precision measurement of the proton’s weak charge in the simplest system. Sensitive search for new physics with CL of 95% at the ~ 2.3 TeV scale. Fundamental 10  measurement of the running of sin 2  W at low energy. Currently in process of 3 year construction cycle; goal is to have multiple runs in 2008 – 2009 timeframe Possible 12 GeV Parity-Violating Moller Experiment at JLAB Conceptual design indicates reduction of E158 error by ~5 may be possible at 12 GeV JLAB. weak charge triad  (Ramsey-Musolf) Summary