Nuclear Physics at Jefferson Lab Part II R. D. McKeown Jefferson Lab College of William and Mary Taiwan Summer School June 29, 2011

2 Strange Quarks Standard Model Tests Dark Matter? Outline

3 Strange Quarks in the Nucleon 3 Strange quarks-antiquarks virtual pairs produced by gluons Contribution to proton’s magnetism - (Stern’s discovery)? - QCD analog of Lamb shift in atoms Study using small (few parts per million) left-right difference in electron-proton force  challenging experiments!

4 Strange Quarks in the Nucleon Mass: u u d u s u s valence sea proton  -N scattering Spin:Polarized deep-inelastic scattering HERMES semi-inclusive -p elastic scattering

5 Electroweak charged fermion couplings

6 Weak Charges Q W p = 1 – 4 sin 2  W ~ Q W n = -1

7 Neutral weak form factors Electromagnetic interaction Neutral weak interaction  p Z0Z0 p G E ,p, G M ,p G E Z,p, G M Z,p G A Z,p

8 Use Isospin Symmetry (p  n) = (u  d) For vector form factors theoretical CSB estimates indicate < 1% violations (unobservable with currently anticipated uncertainties) (Miller PRC 57, 1492 (1998) Lewis and Mobed, PRD 59, (1999)

9 Parity-violating electron scattering Polarized electrons on unpolarized target For a proton: (Cahn & Gilman 1978)  Z0Z0  2 Forward anglesBackward angles

10 (VMD) Soliton, NJL, … l Dispersion Integrals l Lattice QCD Theoretical Approaches

11 Theoretical predictions for  s

12 SAMPLE Experiment Polarized Injector Wien Filter Accelerator E = 125 MeV 600 pulses/s I pk = 3 mA I ave = 44  A P B = 36% Energy Beam Current Fast phase shift (energy) feedback K11 Beam current feedback SAMPLE Detector Lumi Position, Angle, Charge Halo Moller Polarimeter Beam position feedback

13 Experimental procedure Asymmetry between pulses separated by 1/60 s  remove effects due to 60 Hz Rapid helicity reversal  reduce effects of long-term drifts Slow helicity reversal  remove helicity-correlated electronics effects

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15 G M s (Q 2 =0.1) = SAMPLE result

16  s Theory and Experiment

17 Other Experiments JLAB Mainz JLAB

18 Global Analysis

19 Nucleon models continue to struggle, with some indication that higher mass poles are important Precise lattice QCD - motivated prediction: (Leinweber, et al., PRL 97, (2006) New unquenched lattice QCD result: Doi, et al., arXiv: Theory Update

20 HAPPEX-III Results A(G s =0) = ppm ± ppm G s E G s M = ± (stat) ± (syst) ± (FF) A PV =  (stat)  (syst) ppm preliminary

21 Measuring the Neutron “Skin” in the Pb Nucleus 21 crust Neutron StarLead Nucleus skin 10 km 10 fm Parity violating electron scattering Sensitive to neutron distribution First clean measurement Relevant to neutron star physics Currently running in Hall A

22 Page 22 Lead ( 208 Pb) Radius Experiment : PREX Elastic Scattering Parity-Violating Asymmetry Z 0 : Clean Probe Couples Mainly to Neutrons Applications : Nuclear Physics, Neutron Stars, Atomic Parity, Heavy Ion Collisions The Lead ( 208 Pb) Radius Experiment (PREX) determines the neutron radius to be larger than the proton radius by fm (+0.15, -0.17). This result represents model-independent confirmation of the existence of a neutron skin, with relevance for neutron star calculations. Plans for follow-up experiment to reduce uncertainties by factor of 3. This can quantitatively pin down the symmetry energy, an important contribution to the nuclear equation of state. A neutron skin of 0.2 fm or more has implications for our understanding of neutron stars and their ultimate fate Rel. mean field Nonrel. skyrme PREX PREX data

23 Running of the Weak Coupling

24 Global Fits

25 PV electron-quark couplings General Form: Standard model:

26 Qweak Luminosity monitors Luminosity monitors scanner Precise determination of the weak charge of the proton Q w = -2(2C 1u +C 1d ) =(1 – 4 sin 2  W )

27 Qweak Overview

28 Target cell 35 cm target cell, designed with CFD Target tested and stable up to 160  A. Sufficient reserve cooling power to easily reach 180  A. Highest power LH2 target. When using 960Hz spin flip rate, the target density fluctuations (an unknown before commissioning) appear to be small compared to expected counting statistical uncertainty (per quartet) of ~220 ppm. Qweak LH 2 Cryotarget

29 Accelerator Performance for Qweak

30 Qweak Projection

31 Radiative Correction Uncertainty (Ramsey-Musolf)

32 Constraints on Couplings HAPPEx: H, He G 0 (forward): H, PVA4: H SAMPLE: H, D projection

33 New combination of: Vector quark couplings C 1q Also axial quark couplings C 2q PV Deep Inelastic Scattering For an isoscalar target like 2 H, structure functions largely cancel in the ratio at high x e-e- N X e-e- Z*Z* ** At high x, A PV becomes independent of x, W, with well-defined SM prediction for Q 2 and y Sensitive to new physics at the TeV scale 0 1 at high x a(x) and b(x) contain quark distribution functions f i (x) PVDIS: Only way to measure C 2q

34 SoLID Spectrometer Baffles GEM’s Gas Cerenkov Shashlyk Calorimeter ANL design JLab/UVA prototype Babar Solenoid International Collaborators: China (Gem’s) Italy (Gem’s) Germany (Moller pol.)

35 Statistical Errors (%) 4 months at 11 GeV 2 months at 6.6 GeV Error bar σ A /A (%) shown at center of bins in Q 2, x Strategy: sub-1% precision over broad kinematic range for sensitive Standard Model test and detailed study of hadronic structure contributions

36 Sensitivity: C 1 and C 2 Plots Cs PVDIS Qweak PVDIS World’s data Precision Data 6 GeV

37 SoLID: Comprehensive PVDIS Study Measure A D in NARROW bins of x, Q 2 with 0.5% precision Cover broad Q 2 range for x in [0.3,0.6] to constrain HT Search for CSV with x dependence of A D at high x Use x>0.4, high Q 2, and to measure a combination of the C iq ’s Strategy: requires precise kinematics and broad range xyQ2Q2 New Physicsnoyesno CSVyesno Higher Twistyesnoyes Fit data to: C(x)=β HT /(1-x) 3

38 PV Møller Scattering SLAC E158 result: A PV = (-131 ± 14 ± 10) x 10 -9

39 E158 Result

40 New JLab Experiment Polarized Beam Unprecedented polarized luminosity unprecedented beam stability Liquid Hydrogen Target 5 kW dissipated power (2 X Qweak) computational fluid dynamics Toroidal Spectrometer Novel 7 “hybrid coil” design warm magnets, aggressive cooling Integrating Detectors build on Qweak and PREX intricate support & shielding radiation hardness and low noise

41 Toroidal Spectrometer Mollers e-p elastic Separate Moller events from background

42 Projected MOLLER Results Projected systematic error:  A/A = 1%

43 Systematic Error Estimate

44 PV Moller Scattering: Custom Toroidal Spectrometer 5kw LH Target SOLID (PVDIS): High Luminosity on LD2 and LH2 Better than 1% errors for small bins Large Q 2 coverage x-range W 2 > 4 GeV 2 44 INT EIC Workshop, Nov. 2010

45 JLab Future 45INT EIC Workshop, Nov. 2010

46 INT EIC Workshop, Nov Kurylov, et al.

47 Muon g-2 Momentum Spin e SUSY? 47INT EIC Workshop, Nov. 2010

48 On the horizon: A New Muon g-2 Experiment at Fermilab Update: Oct 2010:  a  (Expt – Thy) = 297 ± 81 x  BNL E e + e - Thy 3.6  x Future Goals Goal: 0.14 ppm Expected Improvement D. Hertzog 48INT EIC Workshop, Nov. 2010

49 Cosmology and Dark Matter R. D. McKeown June 15, Dark sector is new physics, beyond the standard model Many direct searches for dark matter interacting with sensitive detectors (hints, no established signal yet…) Controversial evidence for excess astrophysical positrons… → many predictions for new physics

50 PAMELA Data on Cosmic Radiation Va. Tech. Physics Colloquium, Dec. 3, Surprising rise in e + fraction But not p Could indicate low mass A’ (M A’ < 1 GeV ) Or local astrophysical origin??

51 NEW! Confirmation from Fermi

52 AMS-02 Launched May 16, 2011 slide from Andrei Kounine TeVPA 2010

53 New Opportunity: Search for A’ at JLab Search for new forces mediated by ~100 MeV vector boson A’ with weak coupling to electrons: Irrespective of astrophysical anomalies: New ~GeV–scale force carriers are important category of physics beyond the SM Fixed-target (FEL + CEBAF) have unique capability to explore this! 53Va. Tech. Physics Colloquium, Dec. 3, 2010 g – 2 preferred!

54 APEX in Hall A Uses existing equipment Successful 2010 test run (results soon!)

55 HPS in Hall B Forward, compact spectrometer/vertex detector identifies heavy photon candidates with invariant mass and decay length. EM Calorimeter provides fast trigger and electron ID. Small cross sections and high backgrounds demand large luminosities. HPS survives beam backgrounds by spreading them out maximally in time, capitalizing on 100% CEBAF duty cycle and employing high rate DAQ. All detectors are split above and below the beam to avoid the “wall of flame” from multiple Coulomb scattered primaries, bremsstrahlung, & degraded electrons.

56 DarkLight at JLab FEL 100 MeV 10 mA Reconstruct all final state particles and achieve an invariant mass resolution of 1 MeV/c 2 or better over the range 10 to 100 MeV/c 2. Toroidal magnetic spectrometer with a bending power of 0.05 to 0.16 T-m with a wire chamber tracker for the leptons, a radial TPC for proton detection and a scintillator for triggering.

57 Jlab Future Clearly we have a exciting and growing program to search for new physics beyond the standard model. But we have a substantial program of important experiments exploring QCD - confinement mechanism - nucleon tomography And there are prospects for a future new facility: Electron Ion Collider (EIC) One more lecture…