PVES Strange Quark Contribution to the Charge and Magnetization of the Nucleon

What can we measure? June 1-19, 2015HUGS 2 Nucleon structure Nuclear structure Electron weak charge Proton weak charge –Weak coupling constants SM Tests

Program HUGS 3 Expt/Lab Target/ Angle Q 2 (GeV 2 ) A phys (ppm) SensitivityStatus SAMPLE/Bates SAMPLE ILH 2 / m s + 0.4G A 2000 SAMPLE IILD 2 / m s + 2G A 2004 SAMPLE IIILD 2 / m s + 3G A 2004 HAPPEx/JLab HAPPExLH 2 / G E G M 2001 HAPPEx IILH 2 / G E + 0.1G M 2006, 2007 HAPPEx He 4 He/ GEGE 2006, 2007 HAPPExLH 2 / G E + 0.5G M 2009 A4/Mainz LH 2 / G E + 0.2G M 2004 LH 2 / G E + 0.1G M 2005 LH 2 / G E + ηG M + η’G A 2009 LH 2 / G E G M 2009 G0/JLab ForwardLH 2 /350.1 to 1-1 to -40G E + ηG M 2005 BackwardLH 2 /LD 2 / , to -45G E + ηG M + η’G A 2009 June 1-19, 2015

Nucleon Structure June 1-19, 2015HUGS 4 Proton is both ordinary and extraordinary object 50% of mass of visible universe masses of constituents ~ 1% of its total mass q q What is it made of? –valence quarks carry baryon number –sea of gluons –and associated quark- antiquark pairs analog of Lamb shift –very complicated because strong coupling ● gluons interact with each other →many-body physics with virtual particles

June 1-19, 2015HUGS 5

Structure Functions Deep Inelastic Scattering HUGS 6 x - fraction of momentum carried by the struck quark June 1-19, 2015

EM Structure of the Nucleon Elastic Scattering HUGS 7  Dirac  Pauli N Electric and magnetic form factors Way of parameterizing this blob June 1-19, 2015

EM Structure of the Nucleon HUGS 8 Neutron Electric Charge Distribution “pion cloud” Related to the charge and magnetization distributions within the nucleon Fourier transform June 1-19, 2015

EM Structure of the Nucleon HUGS 9  Dirac  Pauli  Dirac  Pauli N (Electric and magnetic form factors) June 1-19, 2015

Weak Structure of the Nucleon HUGS 10 Z  Dirac  Pauli N parity violation b/c of this June 1-19, 2015

Strangeness in the Nucleon HUGS 11 Momentum: Spin: Mass: Nucleon in QCD How much do virtual ss pairs contribute to the structure of the nucleon? ¯ Charge and current: June 1-19, 2015

Quarks in the Nucleon HUGS 12 q q June 1-19, 2015

S t R an G e quark contribution HUGS 13 Assume isospin symmetry and we have this and this are well known what about this? (Assume neutral weak charges are known) June 1-19, 2015

Isolating form factors June 1-19, 2015HUGS 14 ~ few parts per million For a proton: For 4 He: G E s alone Forward angle Backward angle For deuteron: enhanced G A e sensitivity

June 1-19, 2015HUGS 15 The Axial Current Contribution ep Z  “box” ep Z  “mixing” ep  “quark pair” Classical analog: torque on a toroidal magnetic field in an external current field –“unknown form factor” G e A (Q 2 ) –related to form factor measured in neutrino scattering –also contains “anapole” form factor –determine isovector (T=1) piece by combining proton and neutron (deuteron) measurements

What is the Anapole Moment? June 1-19, 2015HUGS 16 As first noted by Zel’dovich (Sov. Phys. JETP 6 (58) 1184), a parity-violating coupling of the photon can occur where F A and F E are the anapole (parity-violating, time-reversal conserving) and electric dipole (parity- and time-reversal- violating) moments, respectively At low Q 2 the corresponding interaction energy is (Musolf and Holstein, Phys. Rev. D 43 (91) 2956) The classical analog of the anapole moment is that property of a toroidal magnetic field that leads to a torque in an external current field 

G0 Experiment June 1-19, 2015HUGS 17 Mini-ferris wheel CED+ Cerenkov Ferris wheel FPD LUMIs G0 Beam monitors Target service module Super-conducting magnet (SMS) View from downstream View from ~upstream

June 1-19, 2015HUGS 18 Turn-around of G 0 Detector – Aug. 11, 2005

Turn-around of G 0 Magnet – Aug. 23, 2005 June 1-19, 2015HUGS 19

G0 Experiment HUGS 20 e - beam target CED + Cerenkov FPD LUMIs (not shown) June 1-19, 2015

HUGS 21 Rate Corrections H 687 MeV H 362 MeV Deadtimes (%) Correct the yields for random coincidences and electronic deadtime prior to asymmetry calculation randoms small except for D-687 (due to higher pion rate) Direct (out-of-time) randoms measured - Validated with simulation of the complete electronics chain Data set Correction to Yield (%) Asymmetry Correction (ppm) systematic error (ppm) H H D D June 1-19, 2015

HUGS 22 Background Corrections Data set ΔA (ppm) Δσ A (ppm) H H D D June 1-19, 2015

HUGS 23 Elastic Asymmetries Hydrogen, 687 MeV, BLINDED Including rate, helicity-correlated corrections Pass 1-Raw asymmetries 2-Scaler counting correction 3-Rate correction 4-Linear regression correction Asymmetry (ppm) Octant June 1-19, 2015

Asymmetries --> FFs HUGS 24 Unblinded, corrected asymmetries and Q 2 Combine with forward angle data and nucleon EM form factors D.S. Armstrong et al., PRL 95 (2005) Data Set Q 2 (GeV 2 ) A phys (Value in ppm ± σ stat ± σ pt-pt ± σ global ) H ± 0.872± 0.268± D ± 0.813± 0.411± H ± 2.43± 0.84± 0.75 D ± 3.34± 1.98± 0.64 Preliminary results, not for quotation June 1-19, 2015

HUGS 25 Measurements at Q 2 = 0.1 GeV 2 MIT-Bates (SAMPLE) JLAB (HAPPEx) Q 2 variation from G 0 and HAPPEx at JLAB  10  5% contribution to G p M (Q 2 ) Mainz (A4) G 0 (forward) Summary of other experimental results

Results June 1-19, 2015HUGS 26 First Q 2 dependence of G e A (T=1) What we see: G s E has a small positive component Q 2 =0.63 GeV 2 G s M is consistent with zero Comparison with theory predictions: Lattice QCD – close to zero some models predict small G s E and “large” G s M

Comparison to Nucleon Form Factors June 1-19, 2015HUGS 27 Recall:

The G 0 Collaboration June 1-19, 2015HUGS 28 G 0 Spokesperson: Doug Beck (UIUC) California Institute of Technology, Carnegie-Mellon University, College of William and Mary, Hendrix College, IPN Orsay, JLab, LPSC Grenoble, Louisiana Tech, New Mexico State University, Ohio University, TRIUMF, University of Illinois, University of Kentucky, University of Manitoba, University of Maryland, University of Winnipeg, Virginia Tech, Yerevan Physics Institute, University of Zagreb Analysis Coordinator: Fatiha Benmokhtar (Carnegie-Mellon,Maryland) Thesis Students: Stephanie Bailey (Ph.D. W&M, Jan ’07, not shown) From left to right: Colleen Ellis (Maryland), Alexandre Coppens (Manitoba), Juliette Mammei (VA Tech), Carissa Capuano (W&M), Mathew Muether (Illinois), Maud Versteegen (LPSC), John Schaub (NMSU)

HUGS 29 parity violating asymmetries elastic electron-proton scattering momentum transfer nucleon strange quark form factors June 1-19, 2015

G 0 Results featured in Physical Review Focus June 1-19, 2015HUGS 30

G 0 Results “published” in the Economist magazine June 1-19, 2015HUGS 31