Searches for Physics Beyond the Standard Model The Qweak and MOLLER Experiments Willem T.H. van Oers INT – October 1, 2009

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

The Standard Model: Issues Lots of free parameters (masses, mixing angles, and couplings) How fundamental is that? Why 3 generations of leptons and quarks? Begs for an explanation! Insufficient CP violation to explain all the matter left over from Big Bang Or we wouldn’t be here. Doesn’t include gravity Big omission … gravity determines the structure of our solar system and galaxy Starting from a rational universe suggests that the SM is only a low order approximation of reality, as Newtonian gravity is a low order approximation of general relativity.

 QED  s (QCD) Measured Charges Depend on Distance (running of the coupling constants) 1/137 1/128 Electromagnetic coupling is stronger close to the bare charge Strong coupling is weaker close to the bare charge far close “screening”“anti-screening”

“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.

Weak Charge of the Proton Depends on the Weak Mixing Angle,  W MZMZ MWMW WW WW g U(1) g SU(2) “on-shell”  + corrections  The exact value of the corrections depends on how much is included in the definition of (normalization scheme).  At the Z-pole, sin 2  W = in the MSbar scheme, but is in the on-shell scheme  You can take the value of measured at the Z-pole and “run” it to other energies.

Weak Charge Phenomenology This accidental suppression of the proton weak charge in the SM makes it more sensitive to new physics (all other things being equal). Note how the roles of the proton and neutron have become almost reversed (ie, neutron weak charge is dominant, proton weak charge is almost zero!) Q e -1 -(1 – 4sin 2  W ) = -.048

(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 contains hadronic structure information – strange form factors Strange electric and magnetic form factors -measure contribution of strange quark sea to nucleon structure

How Low a Value of Q 2 to be Used? low Q 2 reduces the hadronic correction, but also reduces A z the experiment will use Q 2 = 0.03 (Gev/c) 2,  = 8 , where Qweak term Hadronic correction constrained by G0, HAPPEX, PV-A4, SAMPLE calculations Ross Young, JLab The -300 ppb (-0.3 ppm) is technically manageable The hadronic corrections should introduce <2% error in Q W 10

Electroweak Radiative Corrections Q p Weak Standard Model (Q 2 = 0) ± Q p Weak experiment precision goal± SourceQ p Weak Uncertainty  sin  W (M Z )± Z  box±  sin  W (Q) hadronic ± WW, ZZ box - pQCD± Charge symmetry 0 Total± Erler, Kurylov, Ramsey-Muslolf,, PRD 68(2003) Estimates of  -Z box diagrams on A PV at Qweak Kinematics TBE (Tjon, Blunden, Melnitchouk) 0.13% ( hadronic: N and  ) arXiv: TBE (Gorchtein & Horowitz) ~ 6% (dispersion relations; PVDIS FF) Phys. Rev. Lett. 102, (2009) However, see more recent calculations ! Note: Perhaps  -W box diagrams involved in V ud extraction in nuclear beta decay can provide insight? (Erler, et al.)

JLab Qweak Run I + II + III ±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)

New Physics Sensitivity of Q p weak Q p weak is sensitive to new electron-quark interactions such as Leptoquarks A new heavy vector Z’ R-parity violating SUSY Compositeness but not the usual R parity- conserving SUSY (she’s very shy and hides in loops).

R.D. Young et al., PRL 99, (2007) Present Parity-Violating Electron-Proton Elastic Scattering Data: Extrapolation to Q 2 = 0 PDG SM Qweak

New update on C 1q couplings Dramatic improvement in knowledge of weak couplings! 95% (R.D.Young et al.) Factor of 5 increase in precision of Standard Model values

Overview of the Q p Weak Experiment Incident beam energy: GeV Beam Current: 150 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/c) 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

Technical details  5 x statistics Count for 2500 hr at 6.5 GHz.  Beam polarization New Hall-C Compton polarimeter.  Absolute Q 2 Dedicated runs with full tracking. Accurate magnetic field map.  hadronic correction Theory and existing experiment  Background fraction. Dedicated runs with tracking and TOF  Beam Properties. Online measurement and correction. How do you do that? We want: 2% on A z  4% on Q w  0.3% on sin 2  W How hard is that? G0 500 ppb HAPPEX ppb TRIUMF E ppb SLAC E ppb Qweak 6 ppb MOLLER 0.7 ppb Typical A z uncertainties, adding statistical and systematic in quadrature.

  A phys /A phys  Q p weak /Q p weak Statistical (2500 hours production) 2.1% 3.2% Systematic: Hadronic structure uncertainties % Beam polarimetry 1.0% 1.5% Absolute Q 2 determination 0.5% 1.0% Backgrounds 0.5% 0.7% Helicity-correlated Beam Properties 0.5%0.7% _________________________________________________________ Total 2.5% 4.1%   A phys /A phys  Q p weak /Q p weak Statistical (2500 hours production) 2.1% 3.2% Systematic: Hadronic structure uncertainties % Beam polarimetry 1.0% 1.5% Absolute Q 2 determination 0.5% 1.0% Backgrounds 0.5% 0.7% Helicity-correlated Beam Properties 0.5%0.7% _________________________________________________________ Total 2.5% 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

Principal Parts of the Q p weak Experiment Synthetic Quartz Scintillator Bars Toroidal Spectrometer Magnet Liquid Hydrogen Target (2.5 kW) Electron Beam GeV 150  A (0.2 nA) P ~ 85% Region 2: HDCs Region 1: GEMs Collimator System Region 3: VDCs Lumi Monitors Trigger Scintillator light blue = counting mode black = current mode

The QTOR Resistive Spectrometer Magnet:

View Along Beamline of Q p Weak Apparatus - Simulated Events Central scattering angle: ~8.4° ± 3° Phi Acceptance: > 50% of 2  Average Q²: (GeV/c) 2 Acceptance averaged asymmetry: –0.29 ppm Integrated Rate (per detector): ~801 MHz Inelastic/Elastic ratio: ~0.026% Central scattering angle: ~8.4° ± 3° Phi Acceptance: > 50% of 2  Average Q²: (GeV/c) 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; 0.18 m wide X 2.0 meters long rectangular quartz bar; 0.18 m wide X 2.0 meters long Inelastic/Elastic Separation in Q p Weak

 Highest power (2500 watt) cryotarget ever  ~50 litre liquid hydrogen inventory  35 cm long, 2200 watt beam load  High capacity combined 4K and 15K heat exchanger  LN2 pump tests ongoing Cryotarget Transverse flow “ice cream cone” target cell

Preparing the TRIUMF field mapper at MIT-Bates

Luminosity monitor  Symmetric array of 8 quartz Cerenkov detectors instrumented with rad hard PMTs operated in “vacuum photodiode mode” and 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

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

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.

 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

Errors from Helicity Correlated Beam Properties

R.D. Young et al., PRL 99, (2007) No PVES with PVES future Q p weak Sensitivity to New Physics Depends on Relative Importance of the New up and down Quark Couplings up down  Qweak constrains new physics to beyond 2 TeV

 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 2005 JLAB Jeopardy Proposal approved with ‘A’ rating  March 2007 Two day engineering run (at end of G zero) Beam noise and target boiling studies.  January 2008PAC33 Jeopardy review. Qweak granted 198 PAC days as requested.  October 2009 Installation on the beam line starts  May 2010 – May 2011 Phase I commissioning and data taking  November 2011 Phase II data taking  May GeV conversion of CEBAF Progress of Qweak – Past to Future

Parity-Violating Electron-Electron Scattering at 11 GeV E = 11 GeV 4000 hours L = 150 cm A PV = -40 ppb JLab could determine Q e weak to 2.5% as a search for new physics or the best low energy determination of the weak mixing angle.

Møller Scattering Purely leptonic reaction Figure of Merit rises linearly with E lab Small, well-understood dilution SLAC: Highest beam energy with moderate polarized luminosity JLab 11 GeV: Moderate beam energy with LARGE polarized luminosity Derman and Marciano (1978)

Parity-Violating Electron-Electron Scattering at 11 GeV Q e weak would tightly constrain RPV SUSY (ie tree-level One of few ways to constrain RPC SUSY if it happens to conserve CP (hence SUSY EDM = 0). Direct associated- production of a pair of RPC SUSY particles might not be possible even at LHC. Theory contours 95% CL Expt bands 1σ ΔQ e weak ΔQ p weak  (Q e W ) SUSY / (Q e W ) SM

Complementary to LHC A PV Best current limits on 4-electron contact interactions: LEPII at 200 GeV (Average of all 4 LEP experiments) insensitive toOR RPV SUSY Minimal SUSY Ramsey-Musolf and Su (2007) This proposal Courtesy F. Petriello et al

MOLLER Parameters Comparable to the two best measurements at colliders Unmatched by any other project in the foreseeable future At this level, one-loop effects from “heavy” physics Compelling opportunity with the Jefferson Lab Energy Upgrade: E beam = 11 GeV A PV = 35.6 ppb δ(A PV ) = 0.73 ppb δ(Q e W ) = ± 2.1 (stat.) ± 1.0 (syst.) % 75 μA80% polarized δ(sin 2 θ W ) = ± (stat.) ± (syst.) ~ 0.1% ~ 38 weeks (~ 2 yrs) not just “another measurement” of sin 2  W

11 GeV Møller Experiment double toroid configuration

Near-Term Plans MOLLER proposal receives JLab PAC approval in January 2009 With help of laboratory management, aim to provide input to DoE planning retreat in Spring 2010 Must generate documentation for proceeding to a CD0 request Director’s Review in mid-January 2010 will help provide such documentation Task is to prepare for such a review this Fall

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” NuTEV result in agreement with Standard Model after corrections have been applied Upcoming Q p Weak 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 time frame Future 11 GeV Parity-Violating Moller Experiment Q e weak at JLAB Conceptual design indicates reduction of E158 error by ~5 may be possible at 11 GeV JLAB. Experiment approved with A rating; JLab Directors review in early weak charge triad  (Ramsey-Musolf) Summary

D. Armstrong, A. Asaturyan, T. Averett, J. Benesch, J. Birchall, P. Bosted, A. Bruell, C. Capuano, R. D. Carlini 1 (Principal Investigator), G. Cates, C. Carrigee, S. Chattopadhyay, S. Covrig, C. A. Davis, K. Dow, J. Dunne, D. Dutta, R. Ent, J. Erler, W. Falk, H. Fenker, T. A. Forest, W. Franklin, D. Gaskell, M. Gericke, J. Grames, K. Grimm, F.W. Hersman, D. Higinbotham, M. Holtrop, J.R. Hoskins, K. Johnston, E. Ihloff, M. Jones, R. Jones, K. Joo, J. Kelsey, C. Keppel, M. Khol, P. King, E. Korkmaz, S. Kowalski 1, J. Leacock, J.P. Leckey, L. Lee, A. Lung, D. Mack, S. Majewski, J. Mammei, J. Martin, D. Meekins, A. Micherdzinska, A. Mkrtchyan, H. Mkrtchyan, N. Morgan, K. E. Myers, A. Narayan, A. K. Opper, SA Page 1, J. Pan, K. Paschke, M. Pitt, M. Poelker, T. Porcelli, Y. Prok, W. D. Ramsay, M. Ramsey-Musolf, J. Roche, N. Simicevic, G. Smith 2, T. Smith, P. Souder, D. Spayde, B. E. Stokes, R. Suleiman, V. Tadevosyan, E. Tsentalovich, W.T.H. van Oers, W. Vulcan, P. Wang, S. Wells, S. A. Wood, S. Yang, R. Young, H. Zhu, C. Zorn 1 Spokespersons 2 Project Manager College of William and Mary, University of Connecticut, Instituto de Fisica, Universidad Nacional Autonoma de Mexico, University of Wisconsin, Hendrex College, Louisiana Tech University, University of Manitoba, Massachusetts Institute of Technology, Thomas Jefferson National Accelerator Facility, Virginia Polytechnic Institute & State University, TRIUMF, University of New Hampshire, Yerevan Physics Institute, Mississippi State University, University of Northern British Columbia, Cockroft Institute of Accelerator Science and Technology, Ohio University, Hampton University, University of Winnipeg, University of Virginia, George Washington University, Syracuse University, Idaho State University, University of Connecticut, Christopher Newport University The Qweak Collaboration