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Parity Violation at Jefferson Lab PREX, MOLLER, & PVDIS Experiments

Parity Violation at Jefferson Lab PREX, MOLLER, & PVDIS Experiments. Robert Michaels Hall A. Thomas Jefferson National Accelerator Facility. 1/16. Parity Violating Asymmetry. 2. +. A PV from interference. 208 Pb. 208 Pb.

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Parity Violation at Jefferson Lab PREX, MOLLER, & PVDIS Experiments

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  1. Parity Violation at Jefferson Lab PREX, MOLLER, & PVDIS Experiments Robert Michaels Hall A Thomas Jefferson National Accelerator Facility 1/16

  2. Parity Violating Asymmetry 2 + APV from interference 208Pb 208Pb Applications of APV at Jefferson Lab • Nucleon Structure • Test of Standard Model of Electroweak • Nuclear Structure (neutron density) Strangeness s s in proton (HAPPEX, G0 expts) e – e (MOLLER) , e – q (PVDIS) elastic e – p at low Q2 (QWEAK) This talk e - 208Pb PREX 2/16

  3. Flux Integration Technique: HAPPEX: 2 MHz PREX: 500 MHz How to do a Parity Experiment (integrating method) Example : HAPPEX 3/16

  4. Asymmetry (ppm) Slug Small beam-related Systematics -- thanks to Jlab beam quality Parity Violating Asymmetry • Offline asymmetries nearly identical to online. • Corrections tiny (here, 3 ppb) • Errors are statistical only HAPPEX-II data D. Lhuillier, K. Kumar spokespersons (~1 day) Araw = -1.58 ppm 0.12 (stat)  0.04 (syst) HAPPEX-II data (HWP = optical element used to flip beam helicity, helps suppress some systematics) 4/16

  5. Parity Quality Beam : Unique Strength of JLab Helicity – Correlated Position Differences Plotted below Araw = Adet - AQ +  E+ i xi Measured separately Points: Not sign-corrected. 20-50 nm diffs. with pol. source setup & feedback Sign flips using ½ wave plate & Wien filter ++ -++--- This BPM, Average = 2.4 3.1 nm Sign flips provide further suppression : Average with signs = what experiment feels achieved < 5 nm Units: microns PREX data Slug # ( ~ 1 day) 5/16

  6. PREX : Z0 of weak interaction : sees the neutrons T.W. Donnelly, J. Dubach, I. Sick Nucl. Phys. A 503, 589, 1989 C. J. Horowitz, S. J. Pollock, P. A. Souder, R. Michaels Phys. Rev. C 63, 025501, 2001 Neutron form factor C.J. Horowitz Parity Violating Asymmetry 6/16

  7. PREX & Neutron Stars C.J. Horowitz, J. Piekarewicz RN calibrates equation of state (pressure vs density) of Neutron Rich Matter Combine PREX RN with Observed Neutron Star Radii Phase Transition to “Exotic” Core ? Strange star ?Quark Star ? Some Neutron Stars seem too cold Explained by Cooling by neutrino emission (URCA process) ? 0.2 fm URCA probable, else not 7/16 Crab Pulsar

  8. Pol. Source Hall A JLAB CEBAF PREX Results PRL 108 (2012) 112502 HRS + septum Physics Asymmetry Pb target • Statistics limited ( 9% ) • Systematic error goal achieved ! (2%) HRS Septum Magnet 50 Pb target 8/16

  9. Asymmetry leads to RN Establishing a neutron skin at ~95 % CL Neutron Skin = RN - RP = 0.33 + 0.16 - 0.18 fm published Spokespersons K. Kumar R. Michaels K. Paschke P. A. Souder G. Urciuoli proposed Also considering a new 48Ca proposal 9/16

  10. GeV Parity Program • MOLLER (e-e scattering) • PVDIS (e-q scattering) • Fundamental tests of electroweak theory 10/16

  11. MOLLER Credit: Krishna Kumar Moller (e-e) Scattering: Search for New Physics at the TeV Scale + 11 GeV Beam 5-10 mrad LH2 APV = 35.6 ppb best contact interaction reach for leptons at low OR high energy δ(QeW) = ± 2.1 % (stat.) ± 1.0 % (syst.) Luminosity: 3x1039 cm2/s! To do better for a 4-lepton contact interaction would require: Giga-Z factory, linear collider, neutrino factory or muon collider Ebeam = 11 GeV 75 μA 80% polarized δ(APV) = 0.73 parts per billion 11/16

  12. SOLID Spectrometer forPVDIS Credit: Paul Souder Standard Model test in the e – quark couplings. Novel window on QCD using a broad kinematic scan to unfold hadronic effects (CSV, higher twist) Project is still at an early planning stage Error bar σA/A (%) at bins in Q2, x Q2(GeV2) 12/16

  13. J. Erler and E. Rojas • Virtually all GUT models predict new Z’s • LHC reach ~ 5 TeV, but.... • For ‘light’ 1-2 TeV, Z’ properties can be extracted Suppose a 1 to 2 TeV heavy Z’ is discovered at the LHC • Can we point to an underlying GUT model? Interplay with LHC: New Physics Assume either SUSY or Z’discovered at LHC Does Supersymmetry provide a candidate for dark matter? MSSM Not if Nature lies in RPV SUSY space rather than MSSM space RPV SUSY Ramsey-Musolf and Su, Phys. Rep. 456 (2008) / TeV-Scale Z 13/16

  14. Interplay with LHC: EW Physics mW and sin2ϴW are powerful indirect probes of the mH use standard model electroweak radiative corrections to evolve best measurements to Q ~ MZ MOLLER projected δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.) precise enough to affect the central value of the world average 14/16

  15. MOLLER Status Director’s Review chaired by C. Prescott: positive endorsement • MOLLER Collaboration • ~ 100 authors, ~ 30 institutions • Expertise from SAMPLE A4, HAPPEX, G0, PREX, Qweak, E158 • 4th generation JLab parity experiment Technical Challenges • ~ 150 GHz scattered electron rate • Idea is to flip Pockels cell ~ 2 kHz • 80 ppm pulse-to-pulse statistical fluctuations • 1 nm control of beam centroid on target • Improved methods of “slow helicity reversal” • > 10 gm/cm2 liquid hydrogen target • 1.5 m: ~ 5 kW @ 85 μA • Full Azimuthal acceptance with ~ 5 mrad • novel two-toroid spectrometer • radiation hard, highly segmented integrating detectors • Robust and Redundant 0.4% beam polarimetry • Compton and Moller Polarimeters • ~ 20M$ project funding sought • 3-4 years construction • 2-3 years running 15/16 thanks, Krishna Kumar

  16. Conclusions : Parity-Violation at Jefferson Lab Robert Michaels Hall A • Jefferson Lab is a great place to do parity-violation. Leverages the strengths of the • polarized source and superconducting RF accelerator. • Parity experiments provide • Unique information about structure of • nucleon ( strangeness content ) • nuclei ( neutrons ) PREX • Precision Frontier of Standard Electroweak Model • complementary to LHC. not discussed Thomas Jefferson National Accelerator Facility MOLLER, SOLID-PVDIS

  17. appendix

  18. MOLLER Spectrometer Design Progress • Magnet Concepts : • increased the size of the water cooling hole • simplified layout with slightly larger conductor • current density fine with sufficient water flow • water-cooling achievable • weight and magnetic forces modest • still need work on support structure and water/electrical connections • Ongoing studies (students/postdocs) : • optimize the optics • position sensitivity studies • magnetic forces for asymmetric coils

  19. SoLID PVDIS Progress • CLEO-II magnet fulfills requirements of SoLID PVDIS and SoLID SIDIS. Preliminary discussions about procuring magnet from Cornell have been started. • Baffles: workable concept has been developed for the baffle assembly. • GEM prototyping on going at UVa and several Chinese institutions (USTC, CIAE, Tsinghua U, Lanzhou U,IMP). • Cherenkov conceptual design with two readout options (PMT/GEM). • Shashlyk type EM Calorimeter R&D ongoing by user institutions, collaboration with IHEP from Russia. • A Geant4 simulation framework, GEMC, is successfully applied. • Analysis Software: Tracking framework and calibration methods being developed • Aiming for a Director’s Review in Fall 2012

  20. PREX: 2 Measurement at one Q is sufficient to measure R N ( R.J. Furnstahl ) Why only one parameter ? (next slide…) proposed error

  21. Slide adapted from J. Piekarewicz Nuclear Structure:Neutron density is a fundamental observable that remains elusive. Reflects poor understanding of symmetry energy of nuclear matter = the energy cost of ratio proton/neutrons n.m. density • Slope unconstrained by data • Adding R from Pb will significantly reduce the dispersion in plot. 208 N

  22. Thanks, Alex Brown PREX Workshop 2008 Skx-s15 E/N

  23. Thanks, Alex Brown PREX Workshop 2008 Skx-s20 E/N

  24. Thanks, Alex Brown PREX Workshop 2008 Skx-s25 E/N

  25. Lead / Diamond Target Diamond LEAD • Three bays • Lead (0.5 mm) sandwiched by diamond (0.15 mm) • Liquid He cooling (30 Watts)

  26. Performance of Lead / Diamond Targets melted melted Targets with thin diamond backing (4.5 % background) degraded fastest. Thick diamond (8%) ran well and did not melt at 70 uA. NOT melted Last 4 days at 70 uA Solution: Run with 10 targets.

  27. PREX-I Result Systematic Errors Physics Asymmetry • Statistics limited ( 9% ) • Systematic error goal achieved ! (2%) A physics letter was recently accepted by PRL. (1) Normalization Correction applied PRL 108 (2012) 112502 (2) Nonzero correction (the rest assumed zero)

  28. Improvements for PREX-II Region downstream of target Tungsten Collimator & Shielding HRS-L Q1 Septum Magnet target HRS-R Q1 Location of ill-fated O-Ring which failed & caused significant time loss during PREX-I  PREX-II to use all-metal seals Collimators

  29. Geant 4 Radiation Calculations PREX-II shielding strategies scattering chamber shielding Number of Neutrons per incident Electron 0 - 1 MeV beamline Energy (MeV) --- PREX-I --- PREX-II, no shield --- PREX-II, shielded 1 - 10 MeV • Strategy • Tungsten ( W) plug • Shield the W • x 10 reduction in • 0.2 to 10 MeV neutrons Energy (MeV) 10 - 1200 MeV Energy (MeV) 49

  30. Polarized Electron Source Laser GaAs Crystal Pockel Cell flips helicity Halfwave plate (retractable, reverses helicity) Gun - e beam • Based on Photoemission from GaAs Crystal • Polarized electrons from polarized laser • Need : • Rapid, random helicity reversal • Electrical isolation from the rest of the lab • Feedback on Intensity Asymmetry

  31. P I T AEffect Important Systematic : Polarization Induced Transport Asymmetry Intensity Asymmetry Laser at Pol. Source where Transport Asymmetry drifts, but slope is ~ stable. Feedback on 28/53

  32. Perfect DoCP Intensity Asymmetry (ppm) A simplified picture: asymmetry=0 corresponds to minimized DoLP at analyzer Pockels cell voltage D offset (V) Methods to Reduce Systematics Scanning the Pockels Cell voltage = scanning the residual linear polarization (DoLP) A rotatable l/2 waveplate downstream of the P.C. allows arbitrary orientation of the ellipse from DoLP

  33. Pull Plot (example) PREX Data

  34. Corrections to the Asymmetry are Mostly Negligible • Coulomb Distortions ~20% = the biggest correction. • Transverse Asymmetry (to be measured) • Strangeness • Electric Form Factor of Neutron • Parity Admixtures • Dispersion Corrections • Meson Exchange Currents • Shape Dependence • Isospin Corrections • Radiative Corrections • Excited States • Target Impurities Horowitz, et.al. PRC 63 025501

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