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
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 - PowerPoint PPT Presentation
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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
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: Q2 << MZ2Large Hadron Collider as well as
• 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
Colliders vs Low Q2
Window of opportunity for weak neutral current measurements at Q2<<MZ2
2
Processes with potential sensitivity:- neutrino-nucleon deep inelastic scattering- atomic parity violation (APV)- parity-violating electron scattering
NuTeV at Fermilab 133Cs at Boulder
Consider known weak neutral current interactions mediated by Z Bosons
E158@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.
QED s (QCD)
Measured Charges Depend on Distance(running of the coupling constants)
1/137
1/128
Electromagnetic coupling isstronger close to the bare charge
Strong coupling isweaker close to the bare charge
far close far close
“screening” “anti-screening”
“Running of sin2W” in the Electroweak Standard Model
• Electroweak radiative corrections sin2W varies with Q + +
• All “extracted” values of sin2W must agree with the Standard Model prediction or new physics is indicated.
•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 sin2W
APV me E lab (1 4 sin2 W )
Derman and Marciano (1978)
(sin2 W )
sin2 W
0.05(APV )
APV
Møller Scattering
Purely leptonic reaction
APV me E lab (1 4sin2 W )
1
E lab
Figure of Merit rises linearly with Elab
(sin2 W )
sin2 W
0.05(APV )
APV
Small, well-understood dilution
SLAC: Highest beam energy with moderate polarized luminosityJLab 11 GeV: Moderate beam energy with LARGE polarized luminosity
Derman and Marciano (1978)
JLab QweakJLab 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.
• 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.
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
• 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
Parity-Violating Electron-Electron Scattering at 11 GeV
• 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.
Theory contours 95% CL Experimental bands 1σ
ΔQeweak
ΔQpweak
(QeW)SUSY/ (Qe
W)SM
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
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 here will 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....
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:
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.• Fundamental 10 measurement of the running of sin2W 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)
Summary
To Note:
• ECT Workshop, November 8 – 12, 2010 –
“Precision Tests of the Standard Model: from Atomic
Parity Violation to Parity-Violating Electron Scattering”