Searches for Physics Beyond the Standard Model The

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

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

Worldwide Experimental Thrust in the 2010 s: New Physics Searches Compelling arguments for “New Dynamics” at the Te. V Scale A comprehensive search for clues requires: Large Hadron Collider as well as Lower Energy: Q 2 << MZ 2 Nuclear/Atomic systems address several topics; complement the LHC: • Neutrino mass and mixing 0 decay, 13, decay, long baseline neutrino expts • Rare or Forbidden Processes EDMs, 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)

Colliders vs Low 2 Q Consider known weak neutral current interactions mediated by Z Bosons 2 Window of opportunity for weak neutral current measurements at Q 2<<MZ 2 Processes with potential sensitivity: - neutrino-nucleon deep inelastic scattering Nu. Te. V at Fermilab 133 Cs at Boulder - atomic parity violation (APV) - parity-violating electron scattering E 158@SLAC

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.

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

“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.

MOLLER Objective Derman and Marciano (1978) Ebeam = 11 Ge. V 75 μA APV = 35. 6 ppb 80% polarized (~ 2. 5 yrs) δ(APV) = 0. 73 ppb δ(Qe. W) = ± 2. 1 (stat. ) ± 1. 0 (syst. ) % δ(sin 2θW) = ± 0. 00026 (stat. ) ± 0. 00012 (syst. ) ~ 0. 1% not just “another measurement” of sin 2 W 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

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

Qpweak & Qeweak – Complementary Diagnostics for New Physics JLab Qweak SLAC E 158 - (proposed) Run I + 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 E 158 (pure leptonic) together make a powerful program to search for and identify new physics. • MOLLER (pure leptonic) is intended to do considerably better.

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 • pioneering • recent • next generation • future • major developments in - photocathodes ( I & P ) - polarimetry - high power cryotargets - nanometer beam stability - precision beam diagnostics - low noise electronics - radiation hard detectors

11 Ge. V MOLLER Experiment double toroid configuration

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

ECOM = 53 Me. V = 90 o Asymmetry (ppb) CM Center of Mass Angle cross-section (mb) Highest figure of merit at θ identical particles! Center of Mass Angle • Avoid superconductors Odd number of coils: both forward & backward Mollers in same phi-bite – ~150 k. W of photons from target – Collimation extremely challenging – high field dipole chicane – poor separation from background – ~ 20 -30% azimuthal acceptance loss • Two Warm Toroids – 100% azimuthal acceptance – better separation from background meters • Quadrupoles a la E 158 first toroid hybrid toroid meters

Parity-Violating Electron-Electron Scattering at 11 Ge. V • 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). ΔQpweak Theory contours 95% CL Experimental bands 1σ Direct associatedproduction of a pair of RPC SUSY particles might not be possible even at LHC. d(Qe. W)SUSY/ (Qe. W)SM ΔQeweak

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

MOLLER Parameters Ebeam = 11 Ge. V 75 μA APV = 35. 6 ppb 80% polarized ~ 38 weeks (~ 2 yrs) δ(APV) = 0. 73 ppb δ(Qe. W) = ± 2. 1 (stat. ) ± 1. 0 (syst. ) % δ(sin 2θW) = ± 0. 00026 (stat. ) ± 0. 00012 (syst. ) ~ 0. 1% not just “another measurement” of sin 2 W 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

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 E 158 • Default: Same geometry as E 158 scattering chamber parameter value length 150 cm thickness 10. 7 gm/cm 2 X 0 17. 5% p, T 35 psia, 20 K power 5000 W

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

Signal & Backgrounds parameter value • Statistical Error cross-section 45. 1 μBarn – 83 ppm 1 k. Hz pulse-pair width @ 75 μA Rate @ 75 μA 135 GHz – table assumes 80% polarization & no degradation of statistics from other sources pair stat. width (1 k. Hz) 82. 9 ppm – realistic goal ~ 90 ppm δ(Araw) ( 6448 hrs) 0. 544 ppb – δ(Astat)/A (80% pol. ) 2. 1% potential for recovering running time with higher Pe, higher efficiency, better spectrometer focus. . δ(sin 2θW)stat 0. 00026 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 • 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

Outlook • Aggressive physics goal – conservative design choices – reasonable extrapolations on existing/planned third generation technologies • Strong, committed collaboration – Experience from previous E 158, G 0, 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 CD 0 process in 2010

Summary • Completed low energy Standard Model tests are consistent with Standard Model “running of sin 2 W” SLAC E 158 (running verified at ~ 6 level) - leptonic Cs APV (running verified at ~ 4 level ) – semi-leptonic, “d-quark dominated” Nu. TEV result in agreement with Standard Model after corrections have been applied • Upcoming Qp. 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 Te. V 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 Ge. V Parity-Violating Moller Experiment Qeweak at JLAB • Conceptual design indicates reduction of E 158 error by ~5 may be possible at 11 Ge. V JLAB. Experiment approved with A rating; JLab Directors review took place in early 2010 with very positive outcome. weak charge triad (Ramsey-Musolf)

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