Parity Violation at Jefferson Lab PREX MOLLER PVDIS

Parity Violation at Jefferson Lab PREX, MOLLER, & PVDIS Experiments Robert Michaels Hall A 1/16 R. Michaels, Jlab DOE S&T 2012

Parity Violating Asymmetry 2 + APV from interference 208 Pb Applications of APV at Jefferson Lab • Nucleon Structure Strangeness s s in proton (HAPPEX, G 0 expts) • Test of Standard Model of Electroweak e–e This talk (MOLLER) , e – q (PVDIS) elastic e – p at low Q 2 (QWEAK) • Nuclear Structure (neutron density) R. Michaels, Jlab DOE S&T 2012 PREX e - 208 Pb 2/16

How to do a Parity Experiment (integrating method) Flux Integration Technique: Example : HAPPEX: 2 MHz PREX: 500 MHz R. Michaels, Jlab DOE S&T 2012 3/16

Small beam-related Systematics -- thanks to Jlab beam quality • Offline asymmetries nearly identical to online. Parity Violating Asymmetry • Errors are statistical only Asymmetry (ppm) • Corrections tiny (here, 3 ppb) HAPPEX-II data D. Lhuillier, K. Kumar spokespersons Slug (~1 day) Araw = -1. 58 ppm 0. 12 (stat) 0. 04 (syst) HAPPEX-II data R. Michaels, Jlab DOE S&T 2012 (HWP = optical element used to flip beam helicity, helps suppress some systematics) 4/16

Parity Quality Beam : Unique Strength of JLab Helicity – Correlated Position Differences Plotted below Araw = Adet - AQ + E+ i xi Sign flips provide further suppression : Average with signs = what experiment feels achieved < 5 nm R. Michaels, Jlab DOE S&T 2012 Units: microns Points: Not sign-corrected. 20 -50 nm diffs. with pol. source setup & feedback Measured separately Sign flips using ½ wave plate & Wien filter ++ -+ +- -This BPM, Average = 2. 4 3. 1 nm PREX data Slug # ( ~ 1 day) 5/16

PREX : Z 0 of weak interaction : sees the neutrons proton neutron Electric charge 1 0 Weak charge 0. 08 1 Neutron form factor 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 C. J. Horowitz Parity Violating Asymmetry R. Michaels, Jlab DOE S&T 2012 6/16

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 R. Michaels, Jlab DOE S&T 2012 Crab Pulsar URCA probable, else not 7/16

PREX HRS + septum Results PRL 108 (2012) 112502 Physics Asymmetry Pb target Hall A JLAB Pol. Source CEBAF à Statistics limited ( 9% ) à Systematic error goal achieved ! (2%) HRS Septum Magnet Pb target R. Michaels, Jlab DOE S&T 2012 50 8/16

Asymmetry leads to RN Establishing a neutron skin at ~95 % CL Neutron Skin = RN - RP = 0. 33 + 0. 16 - 0. 18 fm published proposed Spokespersons K. Kumar R. Michaels K. Paschke P. A. Souder G. Urciuoli R. Michaels, Jlab DOE S&T 2012 Also considering a new 48 Ca proposal 9/16

12 Ge. V R. Michaels, Jlab DOE S&T 2012 Parity Program • MOLLER (e-e scattering) • PVDIS • Fundamental tests of electroweak theory (e-q scattering) 10/16

MOLLER Credit: Krishna Kumar Moller (e-e) Scattering: Search for New Physics at the Te. V Scale + 11 Ge. V Beam 5 -10 mrad LH 2 APV = 35. 6 ppb δ(Qe. W) = ± 2. 1 % (stat. ) ± 1. 0 % (syst. ) Luminosity: 3 x 1039 cm 2/s! To do better for a 4 -lepton contact interaction would require: Giga-Z factory, linear collider, neutrino factory or muon collider Ebeam = 11 Ge. V 75 μA 80% polarized δ(APV) = 0. 73 parts per billion R. Michaels, Jlab DOE S&T 2012 best contact interaction reach for leptons at low OR high energy 11 11/16

SOLID Spectrometer Credit: Paul Souder for PVDIS 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 Q 2 (Ge. V 2) Error bar σA/A (%) at bins in Q 2, x R. Michaels, Jlab DOE S&T 2012 12/16

Interplay with LHC: New Physics Assume either SUSY or Z’ discovered at LHC Does Supersymmetry provide a candidate for dark matter? MSSM RPV SUSY Not if Nature lies in RPV SUSY space rather than MSSM space Ramsey-Musolf and Su, Phys. Rep. 456 (2008) J. Erler and E. Rojas Te. V-Scale Z / • Virtually all GUT models predict new Z’s • LHC reach ~ 5 Te. V, but. . • For ‘light’ 1 -2 Te. V, Z’ properties can be extracted Suppose a 1 to 2 Te. V heavy Z’ is discovered at the LHC • Can we point to an underlying GUT model? R. Michaels, Jlab DOE S&T 2012 13/1613

Interplay with LHC: EW Physics m. W and sin 2ϴW are powerful indirect probes of the m. H use standard model electroweak radiative corrections to evolve best measurements to Q ~ MZ MOLLER projected δ(sin 2θW) = ± 0. 00026 (stat. ) ± 0. 00012 (syst. ) precise enough to affect the central value of the world average R. Michaels, Jlab DOE S&T 2012 14/16

MOLLER Status Director’s Review chaired by C. Prescott: positive endorsement • MOLLER Collaboration Technical Challenges – ~ 100 authors, ~ 30 institutions – Expertise from SAMPLE A 4, HAPPEX, G 0, PREX, Qweak, E 158 • ~ 150 GHz scattered electron rate – Idea is to flip Pockels cell ~ 2 k. Hz – 4 th generation JLab parity experiment – 80 ppm pulse-to-pulse statistical fluctuations • 1 nm control of beam centroid on target – Improved methods of “slow helicity reversal” • > 10 gm/cm 2 liquid hydrogen target – 1. 5 m: ~ 5 k. W @ 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 R. Michaels, Jlab DOE S&T 2012 • ~ 20 M$ project funding sought • 3 -4 years construction • 2 -3 years running 15/16 thanks, Krishna 15 Kumar

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 ) not discussed nuclei ( neutrons ) PREX • Precision Frontier of Standard Electroweak Model MOLLER, SOLID-PVDIS complementary to LHC. R. Michaels, Jlab DOE S&T 2012

appendix R. Michaels, Jlab DOE S&T 2012

MOLLER Spectrometer Design Progress Magnet Concepts : Property • increased the size of the water cooling Field Integral (Tm) hole • simplified layout with slightly larger Total Power (k. W) conductor Current per wire (A) • current density fine with sufficient Voltage per coil (V) water flow Current Density (A/cm 2) • water-cooling achievable • weight and magnetic forces modest Wire cross section • still need work on support structure (ID: water hole) (in) and water/electrical connections Weight of a coil (lbs) Ongoing studies (students/postdocs) : • optimize the optics • position sensitivity studies • magnetic forces for asymmetric coils R. Michaels, Jlab DOE S&T 2012 Magnetic Forces (lbs) Moller Qweak 0. 15 1. 1 0. 89 40 765 1340 298 384 9500 19 285 18 1200 1550 500 0. 229 x 0. 229 (0. 128) 2. 3 x 1. 5 (0. 8) 44 555 7600 100 3000 27000 Upstream Concept 2

So. LID PVDIS Progress • CLEO-II magnet fulfills requirements of So. LID PVDIS and So. LID 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 Geant 4 simulation framework, GEMC, is successfully applied. • Analysis Software: Tracking framework and calibration methods being developed • Aiming for a Director’s Review in Fall 2012 R. Michaels, Jlab DOE S&T 2012

PREX: 2 Measurement at one Q is sufficient to measure R N ( R. J. Furnstahl ) Why only one parameter ? (next slide…) proposed error R. Michaels, Jlab DOE S&T 2012

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 n. m. density ratio proton/neutrons • Slope unconstrained by data 208 • Adding R N from Pb will significantly reduce the dispersion in plot. R. Michaels, Jlab DOE S&T 2012

Thanks, Alex Brown PREX Workshop 2008 E/N R. Michaels, Jlab DOE S&T 2012 Skx-s 15

Thanks, Alex Brown PREX Workshop 2008 E/N R. Michaels, Jlab DOE S&T 2012 Skx-s 20

Thanks, Alex Brown PREX Workshop 2008 E/N R. Michaels, Jlab DOE S&T 2012 Skx-s 25

Lead / Diamond Target Diamond • Three bays • Lead (0. 5 mm) sandwiched by diamond (0. 15 mm) Liquid. Jlab He R. • Michaels, DOE S&T 2012 cooling (30 Watts) LEAD

Performance of Lead / Diamond Targets melted NOT melted Last 4 days at 70 u. A melted Targets with thin diamond backing (4. 5 % background) degraded fastest. Thick diamond (8%) ran well and did not melt at 70 u. A. Solution: Run with 10 targets. R. Michaels, Jlab DOE S&T 2012

PREX-I Result Systematic Errors Error Source Absolute (ppm) Relative ( %) Polarization (1) 0. 0083 1. 3 Beam Asymmetries (2) 0. 0072 1. 1 Detector Linearity 0. 0076 1. 2 BCM Linearity 0. 0010 0. 2 Rescattering 0. 0001 0 Transverse Polarization 0. 0012 0. 2 Q 2 (1) 0. 0028 0. 4 Target Thickness 0. 0005 0. 1 12 C 0. 0025 0. 4 Inelastic States 0 0 TOTAL 0. 0140 2. 1 Asymmetry (2) (1) Normalization Correction applied (2) Nonzero correction (the rest assumed zero) R. Michaels, Jlab DOE S&T 2012 Physics Asymmetry à Statistics limited ( 9% ) à Systematic error goal achieved ! (2%) A physics letter was recently accepted by PRL 108 (2012) 112502

Improvements for PREX-II Region downstream of target Tungsten Collimator & Shielding HRS-L Septum Magnet Q 1 target HRS-R Q 1 Location of ill-fated O-Ring which failed & caused significant time loss during PREX-I Jlab PREX-II R. Michaels, DOE S&T 2012 to use all-metal seals Collimators

Geant 4 Radiation Calculations scattering chamber PREX-II shielding strategies shielding Number of Neutrons per incident Electron 0 - 1 Me. V beamline Energy (Me. V) 1 - 10 Me. V Strategy ------- PREX-II, no shield PREX-II, shielded • Tungsten ( W ) plug Energy (Me. V) 10 - 1200 Me. V • Shield the W • x 10 reduction in 0. 2 to 10 Me. V neutrons R. Michaels, Jlab DOE S&T 2012 Energy (Me. V) 49

Polarized Electron Source Ga. As Crystal Gun Laser Pockel Cell flips helicity Halfwave plate (retractable, reverses helicity) e - beam • Based on Photoemission from Ga. As Crystal • Polarized electrons from polarized laser • Need : • Rapid, random helicity reversal • Electrical isolation from the rest of the lab • Feedback on Intensity Asymmetry R. Michaels, Jlab DOE S&T 2012

Important Systematic : P I T A Effect Polarization Induced Transport Asymmetry Intensity Asymmetry Laser at Pol. Source where Transport Asymmetry drifts, but slope is ~ stable. Feedback on R. Michaels, Jlab DOE S&T 2012 28/53

Methods to Reduce Systematics Intensity Asymmetry (ppm) Perfect Do. CP Scanning the Pockels Cell voltage = scanning the residual linear polarization (Do. LP) Pockels cell voltage offset (V) A rotatable l/2 waveplate downstream of the P. C. allows arbitrary orientation of the ellipse from Do. LP R. Michaels, Jlab DOE S&T 2012 A simplified picture: asymmetry=0 corresponds to minimized Do. LP at analyzer

Pull Plot (example) R. Michaels, Jlab DOE S&T 2012 PREX Data

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 R. Michaels, Jlab DOE S&T 2012 Horowitz, et. al. PRC 63 025501