1. Searches for Physics Beyond the Standard Model The MOLLER Experiment at Jefferson Laboratory Willem T.H. van Oers CSSM – February 15-19, 2010 Information taken from the introductory talk by Krishna Kumar at the JLab Directors Review of the MOLLER experiment on January 14-15, 2010

2. Outline Global Physics Context MOLLER Objective and Physics Impact Experimental Technique –High Flux Parity Violation Experiments –MOLLER Design Choices –Technical Challenges/Requirements –Statistical and Systematic Errors

3. Nuclear/Atomic systems address several topics; complement the LHC: Neutrino mass and mixing  decay,  13,  decay, long baseline neutrino expts Rare or Forbidden Processes EDMs, charged LFV,  decay Dark Matter Searches Low Energy Precision Electroweak Measurements: Worldwide Experimental Thrust in the 2010s: New Physics Searches Lower Energy: Q 2 << M Z 2 Large Hadron Collideras well as Neutrons: Lifetime, Asymmetries (LANSCE, NIST, SNS...) Muons: Lifetime, Michel parameters, g-2 (BNL, PSI, TRIUMF, FNAL, J-PARC...) Parity-Violating Electron Scattering Low energy weak neutral current couplings, precision weak mixing angle (SLAC, JLab) Complementary signatures to augment LHC new physics signals A comprehensive search for clues requires: Compelling arguments for “New Dynamics” at the TeV Scale

4. Colliders vs Low Q 2 Window of opportunity for weak neutral current measurements at Q 2 <<M Z 2 2 Processes with potential sensitivity: - neutrino-nucleon deep inelastic scattering - atomic parity violation (APV) - parity-violating electron scattering NuTeV at Fermilab 133 Cs at Boulder Consider known weak neutral current interactions mediated by Z Bosons E158@SLAC

5. The Standard Model: Issues Lots of free parameters (masses, mixing angles, and couplings) How fundamental is that? Why 3 generations of leptons and quarks? Asks 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.

6.  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”

7. “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.

9. MOLLER Objective 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 ) = ± 0.00026 (stat.) ± 0.00012 (syst.) ~ 0.1% (~ 2.5 yrs) 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: not just “another measurement” of sin 2  W Derman and Marciano (1978)

10. 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)

11. 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. MOLLER (pure leptonic) is intended to do considerably better. SLAC E158 Q p weak & Q e weak – Complementary Diagnostics for New Physics Erler, Kurylov, Ramsey-Musolf, PRD 68, 016006 (2003)

12. Experimental Technique: Technical Improvements over three Decades Parity-violating electron scattering has become a precision tool Steady progress in technology towards: part per billion systematic control 1% systematic control major developments in - photocathodes ( I & P ) - polarimetry - high power cryotargets - nanometer beam stability - precision beam diagnostics - low noise electronics - radiation hard detectors pioneering recent next generation future

13. 11 GeV MOLLER Experiment double toroid configuration

14. MOLLER Hall Layout Left HRS Right HRS Beam Direction Target Chamber First Toroid Hybrid Toroid Drift Region contains primary beam & Mollers Detector Region Mollers exit vacuum 10 ft 28 m

15. meters first toroid hybrid toroid Asymmetry (ppb) Center of Mass Angle Highest figure of merit at θ CM = 90 o Center of Mass Angle cross-section (mb) E COM = 53 MeV identical particles! Avoid superconductors –~150 kW of photons from target –Collimation extremely challenging Quadrupoles a la E158 –high field dipole chicane –poor separation from background –~ 20-30% azimuthal acceptance loss Two Warm Toroids –100% azimuthal acceptance –better separation from background Odd number of coils: both forward & backward Mollers in same phi-bite

16. 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 Experimental bands 1σ ΔQ e weak ΔQ p weak  (Q e W ) SUSY / (Q e W ) SM

17. Optical Pumping Optical pumping of a GaAs wafer Rapid helicity reversal: change sign of longitudinal polarization ~ kHz to minimize drifts (like a lockin amplifier) Control helicity-correlated beam motion: under sign flip, keep beam stable at the sub- micron level C.Y. Prescott et. al, 1978  B Beam helicity is chosen pseudo-randomly at multiple of 60 Hz sequence of “window multiplets” Example: at 240 Hz reversal Choose 2 pairs pseudo-randomly, force complementary two pairs to follow Analyze each “macropulse” of 8 windows together any line noise effect herewill cancel here MOLLER will plan to use ~ 2 kHz reversal; subtleties in details of timing Noise characteristics have been unimportant in past experiments: Not so for PREX, Qweak and MOLLER....

18. 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 ) = ± 0.00026 (stat.) ± 0.00012 (syst.) ~ 0.1% ~ 38 weeks (~ 2 yrs) not just “another measurement” of sin 2  W

19. Target: Liquid Hydrogen parametervalue length150 cm thickness10.7 gm/cm 2 X0X0 17.5% p,T35 psia, 20K power5000 W E158 scattering chamber Most thickness for least radiative losses No nuclear scattering background Not easy to polarize Need as much target thickness as technically feasible Tradeoff between statistics and systematics Default: Same geometry as E158

21. Detector Systems Integrating Detectors: –Moller and e-p Electrons: radial and azimuthal segmentation quartz with air lightguides & PMTs –pions and muons: quartz sandwich behind shielding –luminosity monitors neutrals ‘pion’ luminosity Other Detectors –Tracking detectors 3 planes of GEMs/Straws Critical for systematics/calibration/debuggi ng –Integrating Scanners quick checks on stability

23. Signal & Backgrounds parametervalue cross-section45.1 μBarn Rate @ 75 μA135 GHz pair stat. width (1 kHz)82.9 ppm δ(A raw ) ( 6448 hrs)0.544 ppb δ(A stat )/A (80% pol.)2.1% δ(sin 2 θ W ) stat 0.00026 Elastic e-p scattering –w–well-understood and testable with data –8–8% dilution, 7.5±0.4% correction Inelastic e-p scattering –s–sub-1% dilution –l–large EW coupling, 4.0±0.4% correction –v–variation of A PV with r and φ photons and neutrons –mostly 2-bounce collimation system –dedicated runs to measure “blinded” response pions and muons –real and virtual photo-production and DIS –prepare for continuous parasitic measurement –estimate 0.5 ppm asymmetry @ 0.1% dilution Statistical Error –8–83 ppm 1 kHz pulse-pair width @ 75 μA –t–table assumes 80% polarization & no degradation of statistics from other sources –r–realistic goal ~ 90 ppm –p–potential for recovering running time with higher Pe, higher efficiency, better spectrometer focus.... Backgrounds:

24. Outlook Aggressive physics goal –conservative design choices –reasonable extrapolations on existing/planned third generation technologies Strong, committed collaboration –Experience from previous E158, G0, HAPPEX experiments –Major roles in Qweak and PREX (the best kind of MOLLER R&D!) No engineering yet –Spectrometer design is the heart of the apparatus launching physics/engineering efforts Cost range: 12-16 M$ –Very generous on engineering/design manpower and contingency projections Begun process of devising a coherent R&D Plan –Assuming green light from Doe and JLab, launch parallel effort to CD0 process in 2010

25. 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 2010-2012 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 took place in early 2010 with very positive outcome. weak charge triad  (Ramsey-Musolf) Summary

26. To Note: ECT Workshop, November 8 – 12, 2010 – “Precision Tests of the Standard Model: from Atomic Parity Violation to Parity-Violating Electron Scattering”