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R. Michaels, Jlab DOE S&T 2012 Parity Violation at Jefferson Lab PREX, MOLLER, & PVDIS Experiments Thomas Jefferson National Accelerator Facility Robert.

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Presentation on theme: "R. Michaels, Jlab DOE S&T 2012 Parity Violation at Jefferson Lab PREX, MOLLER, & PVDIS Experiments Thomas Jefferson National Accelerator Facility Robert."— Presentation transcript:

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

2 R. Michaels, Jlab DOE S&T 2012 Parity Violating Asymmetry + 2 Applications of A PV at Jefferson Lab Nucleon Structure Test of Standard Model of Electroweak Nuclear Structure (neutron density) A PV from interference Strangeness s s in proton (HAPPEX, G0 expts) e – e (MOLLER), e – q (PVDIS) elastic e – p at low Q 2 (QWEAK) 208 Pb PREX This talk e - 208 Pb 2/16

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

4 R. Michaels, Jlab DOE S&T 2012 Offline asymmetries nearly identical to online. Corrections tiny (here, 3 ppb) Errors are statistical only Parity Violating Asymmetry Asymmetry (ppm) Slug Small beam-related Systematics -- thanks to Jlab beam quality (HWP = optical element used to flip beam helicity, helps suppress some systematics) HAPPEX-II data A raw = -1.58 ppm 0.12 (stat) 0.04 (syst) 4/16 (~1 day) D. Lhuillier, K. Kumar spokespersons

5 R. Michaels, Jlab DOE S&T 2012 Slug # ( ~ 1 day) Units: microns Parity Quality Beam : Unique Strength of JLab Helicity – Correlated Position Differences Sign flips provide further suppression : Average with signs = what experiment feels achieved < 5 nm Points: Not sign-corrected. 20-50 nm diffs. with pol. source setup & feedback A raw = A det - A Q + E + i x i Plotted below Measured separately Sign flips using ½ wave plate & Wien filter ++ -+ +- -- This BPM, Average = 2.4 3.1 nm PREX data 5/16

6 R. Michaels, Jlab DOE S&T 2012 PREX : Z 0 of weak interaction : sees the neutrons proton neutron Electric charge 1 0 Weak charge 0.08 1 Neutron form factor Parity Violating Asymmetry T.W. Donnelly, J. Dubach, I. Sick C.J. Horowitz Nucl. Phys. A 503, 589, 1989 C. J. Horowitz, S. J. Pollock, P. A. Souder, R. Michaels Phys. Rev. C 63, 025501, 2001 6/16

7 R. Michaels, Jlab DOE S&T 2012 PREX & Neutron Stars Crab Pulsar C.J. Horowitz, J. Piekarewicz R N calibrates equation of state (pressure vs density) of Neutron Rich Matter Combine PREX R N with Observed Neutron Star Radii Some Neutron Stars seem too cold Strange star ? Quark Star ? Explained by Cooling by neutrino emission (URCA process) ? 0.2 fm URCA probable, else not Phase Transition to Exotic Core ? 7/16

8 R. Michaels, Jlab DOE S&T 2012 Physics Asymmetry CEBAF Hall A JLAB Pol. Source Statistics limited ( 9% ) Systematic error goal achieved ! (2%) Septum Magnet HRS + septum Pb target HRS Pb target 5050 PREX PRL 108 (2012) 112502 Results 8/16

9 R. Michaels, Jlab DOE S&T 2012 Neutron Skin = R N - R P = 0.33 + 0.16 - 0.18 fm Establishing a neutron skin at ~95 % CL Asymmetry leads to R N proposed published Also considering a new 48 Ca proposal Spokespersons K. Kumar R. Michaels K. Paschke P. A. Souder G. Urciuoli 9/16

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

11 R. Michaels, Jlab DOE S&T 2012 11 MOLLER E beam = 11 GeV A PV = 35.6 ppb δ(A PV ) = 0.73 parts per billion δ(Q e W ) = ± 2.1 % (stat.) ± 1.0 % (syst.) 75 μA80% polarized Moller (e-e) Scattering: Search for New Physics at the TeV Scale best contact interaction reach for leptons at low OR high energy To do better for a 4-lepton contact interaction would require: Giga-Z factory, linear collider, neutrino factory or muon collider Luminosity: 3x10 39 cm 2 /s! + LH2 5-10 mrad 11 GeV Beam Credit: Krishna Kumar 11/16

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

13 R. Michaels, Jlab DOE S&T 2012 13 Interplay with LHC: New Physics Does Supersymmetry provide a candidate for dark matter? RPV SUSY MSSM Ramsey-Musolf and Su, Phys. Rep. 456 (2008) 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? J. Erler and E. Rojas Assume either SUSY or Z discovered at LHC Not if Nature lies in RPV SUSY space rather than MSSM space TeV-Scale Z / 13/16

14 R. Michaels, Jlab DOE S&T 2012 Interplay with LHC: EW Physics precise enough to affect the central value of the world average MOLLER projected δ(sin 2 θ W ) = ± 0.00026 (stat.) ± 0.00012 (syst.) m W and sin 2 W are powerful indirect probes of the m H use standard model electroweak radiative corrections to evolve best measurements to Q ~ M Z 14/16

15 R. Michaels, Jlab DOE S&T 2012 15 MOLLER Status ~ 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/cm 2 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 MOLLER Collaboration –~ 100 authors, ~ 30 institutions –Expertise from SAMPLE A4, HAPPEX, G0, PREX, Qweak, E158 –4th generation JLab parity experiment Director s Review chaired by C. Prescott: positive endorsement Technical Challenges ~ 20M$ project funding sought 3-4 years construction 2-3 years running thanks, Krishna Kumar 15/16

16 R. Michaels, Jlab DOE S&T 2012 Conclusions : Parity-Violation at Jefferson Lab 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. Thomas Jefferson National Accelerator Facility Robert Michaels Hall A not discussed MOLLER, SOLID-PVDIS

17 R. Michaels, Jlab DOE S&T 2012 appendix

18 R. Michaels, Jlab DOE S&T 2012 Property Upstream Moller Concept 2 Qweak Field Integral (Tm)0.151.10.89 Total Power (kW)407651340 Current per wire (A)2983849500 Voltage per coil (V)1928518 Current Density (A/cm 2 )12001550500 Wire cross section (ID: water hole) (in) 0.229x0.229 (0.128) 0.229x0.229 (0.128) 2.3x1.5 (0.8) Weight of a coil (lbs)445557600 Magnetic Forces (lbs) 100300027000 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 MOLLER Spectrometer Design Progress

19 R. Michaels, Jlab DOE S&T 2012 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 Directors Review in Fall 2012

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

21 R. Michaels, Jlab DOE S&T 2012 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 Adding R from Pb will significantly reduce the dispersion in plot. N 208 Slide adapted from J. Piekarewicz

22 R. Michaels, Jlab DOE S&T 2012 Skx-s15 Thanks, Alex Brown PREX Workshop 2008 E/N

23 R. Michaels, Jlab DOE S&T 2012 Skx-s20 Thanks, Alex Brown PREX Workshop 2008 E/N

24 R. Michaels, Jlab DOE S&T 2012 Skx-s25 Thanks, Alex Brown PREX Workshop 2008 E/N

25 R. Michaels, Jlab DOE S&T 2012 Diamond LEAD Lead / Diamond Target Three bays Lead (0.5 mm) sandwiched by diamond (0.15 mm) Liquid He cooling (30 Watts)

26 R. Michaels, Jlab DOE S&T 2012 Performance of Lead / Diamond Targets Last 4 days at 70 uA Targets with thin diamond backing (4.5 % background) degraded fastest. Thick diamond (8%) ran well and did not melt at 70 uA. melted NOT melted Solution: Run with 10 targets.

27 R. Michaels, Jlab DOE S&T 2012 Error SourceAbsolute (ppm) Relative ( % ) Polarization (1)0.00831.3 Beam Asymmetries (2) 0.00721.1 Detector Linearity0.00761.2 BCM Linearity0.00100.2 Rescattering0.00010 Transverse Polarization0.00120.2 Q 2 (1)0.00280.4 Target Thickness0.00050.1 12 C Asymmetry (2)0.00250.4 Inelastic States00 TOTAL0.01402.1 Systematic Errors (1) Normalization Correction applied (2) Nonzero correction (the rest assumed zero) PREX-I Result Statistics limited ( 9% ) Systematic error goal achieved ! (2%) Physics Asymmetry A physics letter was recently accepted by PRL. PRL 108 (2012) 112502

28 R. Michaels, Jlab DOE S&T 2012 Collimators Septum Magnet target HRS-L Q1 HRS-R Q1 Improvements for PREX-II Location of ill-fated O-Ring which failed & caused significant time loss during PREX-I PREX-II to use all-metal seals Tungsten Collimator & Shielding Region downstream of target

29 R. Michaels, Jlab DOE S&T 2012 Geant 4 Radiation Calculations PREX-II shielding strategies Number of Neutrons per incident Electron Strategy Tungsten ( W ) plug Shield the W x 10 reduction in 0.2 to 10 MeV neutrons 0 - 1 MeV Energy (MeV) --- PREX-I --- PREX-II, no shield --- PREX-II, shielded 1 - 10 MeV 10 - 1200 MeV beamline shielding scattering chamber 49

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

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

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

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

34 R. Michaels, Jlab DOE S&T 2012 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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