Searches for Physics Beyond the Standard Model

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/Atomicsystems address several topics; complement the LHC: • Neutrino mass and mixing0 decay, 13,  decay, long baseline neutrino expts • Rare or Forbidden ProcessesEDMs, charged LFV, 0 decay • Dark Matter Searches • Low Energy Precision Electroweak Measurements: Complementary signatures to augment LHC new physics signals • 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) Worldwide Experimental Thrust in the 2010s: New Physics Searches Compelling arguments for “New Dynamics” at the TeV Scale A comprehensive search for clues requires: Large Hadron Collider as well as Lower Energy: Q2 << MZ2

4. Processes with potential sensitivity: - neutrino-nucleon deep inelastic scattering - atomic parity violation (APV) - parity-violating electron scattering 2 NuTeV at Fermilab 133Cs at Boulder Window of opportunity for weak neutral current measurements at Q2<<MZ2 Colliders vs Low Q2 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. Measured Charges Depend on Distance (running of the coupling constants) Electromagnetic coupling is stronger close to the bare charge Strong coupling is weaker close to the bare charge “screening” “anti-screening” 1/128 QED s (QCD) 1/137 far close far close

7. +  + “Running of sin2W” in the Electroweak Standard Model • Electroweak radiative corrections •  sin2W varies with Q • All “extracted” values of sin2W must agree with the Standard • Model prediction or new physics is indicated.

9. Ebeam = 11 GeV not just “another measurement” ofsin2W 75 μA 80% polarized (~ 2.5 yrs) δ(APV) = 0.73 ppb Compelling opportunity with the Jefferson Lab Energy Upgrade: • 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 APV = 35.6 ppb δ(QeW) = ± 2.1 (stat.) ± 1.0 (syst.) % δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.) ~ 0.1% MOLLER Objective Derman and Marciano (1978)

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

11. Qpweak & Qeweak – Complementary Diagnostics for New Physics JLab Qweak SLAC E158 - (proposed) Run I + II + III ±0.006 Erler, Kurylov, Ramsey-Musolf, PRD 68, 016006 (2003) • Qweak measurement will provide a stringent stand alone constraint • on lepto-quark based extensions to the SM. • Qpweak (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.

12. Experimental Technique:Technical Improvements over three Decades Parity-violating electron scattering has become aprecisiontool • 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 Beam Direction First Toroid Hybrid Toroid Drift Region Detector Region Target Chamber contains primary beam & Mollers Right HRS Mollers exit vacuum 10 ft 28 m

15. Odd number of coils: both forward & backward Mollers in same phi-bite meters first toroid hybrid toroid meters ECOM = 53 MeV Highest figure of merit at θCM = 90o cross-section (mb) Asymmetry (ppb) • 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 identical particles! Center of Mass Angle Center of Mass Angle

16. Parity-Violating Electron-Electron Scattering at 11 GeV Theory contours 95% CL Experimental bands 1σ ΔQpweak • Qeweak 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. ΔQeweak d(QeW)SUSY/ (QeW)SM

17. MOLLER will plan to use ~ 2 kHz reversal; subtleties in details of timing Example: at 240 Hz reversal Choose 2 pairs pseudo-randomly, force complementary two pairs to follow Analyze each “macropulse” of 8 windows together Noise characteristics have been unimportant in past experiments: Not so for PREX, Qweak and MOLLER.... any line noise effect here will cancel here Optical Pumping C.Y. Prescott et. al, 1978 • 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 • Beam helicity is chosen pseudo-randomly at multiple of 60 Hz • sequence of “window multiplets”

18. not just “another measurement” ofsin2W ~ 38 weeks Compelling opportunity with the Jefferson Lab Energy Upgrade: Ebeam = 11 GeV 75 μA 80% polarized δ(APV) = 0.73 ppb • 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 (~ 2 yrs) APV = 35.6 ppb δ(QeW) = ± 2.1 (stat.) ± 1.0 (syst.) % δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.) ~ 0.1% MOLLER Parameters

19. Target: Liquid Hydrogen • 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 E158 scattering chamber

21. Detector Systems ‘pion’ • 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 luminosity neutrals • Other Detectors • Tracking detectors • 3 planes of GEMs/Straws • Critical for systematics/calibration/debugging • Integrating Scanners • quick checks on stability

23. Signal & Backgrounds • Statistical Error • 83 ppm 1 kHz pulse-pair width @ 75 μA • table assumes 80% polarization & no degradation of statistics from other sources • realistic goal ~ 90 ppm • potential for recovering running time with higher Pe, higher efficiency, better spectrometer focus.... • Elastic e-p scattering • well-understood and testable with data • 8% dilution, 7.5±0.4% correction • Inelastic e-p scattering • sub-1% dilution • large EW coupling, 4.0±0.4% correction • variation of APV with r and φ Backgrounds: • 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

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. Summary • Completed low energy Standard Model tests are consistent with Standard • Model “running of sin2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 QpWeak 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. • Fundamental10 measurement of the running of sin2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 Qeweak 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)

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