Res-Parity: Parity Violating Electron Scattering in the Resonance Region

1. Res-Parity:Parity Violating Electron Scattering in the Resonance Region • Physics: Resonance Structure, Duality, Nuclear Effects in PV scattering • Experiment • Projected Results • Summary: • “Easy” experiment • Never done before; • Relevant to wider community yWith much help from the talented Res-Parity spokespersons, J. Arrington, V. Dharmawardane, H. Mkrtchyan, X. Zheng and especially Peter Bosted Paul E. Reimery

2. e’ e g e’ e Z0 + P P Parity Violation—A Tool • The cross section can be expressed terms of electromagnetic, weak and interference contribution: dTotal = d + dweak + dinterference • Asymmetry due to interference between Z0 and  • Probe using weak interaction instead of EM interaction • EM interaction weights as parton charge squared • Emphasizes up quark contribution • Weak interaction sensitive to down and strange quark content Parity Violation in Resonance Region poorly understood Q2 < 1GeV2 Mproton < W < 2 GeV

3. What is duality and why study it? • In QCD, can be understood from an OPE of moments of structure functions • Duality is described in OPE as higher twist (HT) effects being small or cancelling. Graphic from Melnitchouk et al. Phys. Rept. 406 127 (2005) • Will higher twist terms cancel similarly with the Z0 probe in parity violation c.f. earlier talk by M. Ramsey-Musolf at PAVI06 and review by Melnitchouk, Ent and Keppel, Phys. Rept. 406 127 (2005), hep-ph/05012017

4. Why Study Duality? • Duality works extremely well for spin-averaged structure function to low values of Q2. • Have a great impact on our ability to access kinematic regions that are difficult to access otherwise • Duality in PV electron scattering will provide new constraints for models trying to understand duality and its QCD origins • Would provide significant limits on the contributions of higher twists to 12 GeV DIS region JLab Hall C data as discussed in Melnitchouk et al. Phys. Rept. 406 127 (2005) Duality also appears to work for spin dependent structure functions for Q2 > 1 GeV2.

5. Resonance Region Asymmetry • For inelastic scattering, ARL can be written in terms of response functions • A0¼ 6.5 £ 10-4; • L, T, T0 denote longitudinal, transverse and axial; and • VL,T,T0 represent lepton kinematic factors. • Details have so far been worked out only for N→∆(1232) • c.f. JLab E04-101 and Jones and Petcov Phys. Lett. 91B 137 (1980) Sensitive to axial vector transition form factor, GAN

6. Resonance Region Asymmetry • For inelastic scattering, ARL can be written in terms of response functions Simple, “toy” model: •  depends on sin2W ) Assume sin2W = 0.25 ) VA term disappears • Pure magnetic or electric scattering • No strange, charm contributions • ARLRes¼ -9£ 10-5 Q2 (n/p)

7. Duality for -Z interference? PROTON • No reliable model for n/p ratio in res. region: use simple toy model • Will data look anything like this? • Duality good to ~5% in F2, our goal is to measure ALR to ~5% locally and <3% globally DIS model Resonance model DATA NEEDED!

8. Resonance Region Asymmetry: (1232)—significant departure from duality • Sato and Lee predict significant departure from Duality for N! ALR = 9£ 10-5Q2(1.075+V+A) • A,V contain axial and vector contributions from neutral current • ALR 2£ larger than duality predictions! Duality E=4 GeV Sato and Lee E=6 GeV

9. Physics Goals – Nuclear targets • Parity violating asymmetries over the full resonance region for proton, deuteron, and carbon • Global and local quark-hadron duality in nuclei. • Better precision for global/local duality then proton data (higher luminosity targets) • W resolution limited by Fermi motion. • First look at EMC effect with Z-boson probe • Important input to other PVES and -scattering measurements on nuclear targets

10. Nuclear dependence (EMC effect) • If photon and Z-exchange terms have • identical dependence on parton distributions and • EMC effect is flavor-independent, ) then we expect NO EMC effect in ARL • If we see nuclear dependence Unexpected (?) physics • Flavor dependence of EMC effect no sea quark EMC effect seen by Drell-Yan (Fermilab E772) • Different effect for Z-exchange • If we observe no nuclear dependence important constraint for PVES, -scattering on heavy targets • Res-Parity covers x-region (0.2<x<0.7) where nuclear dependence predicted to be largest in most models

11. Benefits to other experiments

12. Neutrino Oscillation • Major world-wide program to study neutrino mass, mixing • Interpretation requires neutrino cross sections in few GeV region on various nuclei: direct measurements difficult—rely in part on models • Res-Parity will constrain these models, especially the isospin dependence and nuclear dependence • Resonance region probed by Res-Parity dominates total cross section for 1 < En < 5 GeV, important to MINERnA and MINOS neutrino antineutrino

13. Background in Standard Model tests • NuTeV: • Nuclear effects in the weak interaction (as opposed to EM nuclear effects) • Higher twist effects could explain part of observed anomaly • Møller Scattering: • SLAC E158 found (22§4)%background correction from low Q2 ep inelastic scattering (mostly resonance region) • Res-PV will constrain models of the background for future extension aiming at 2% to 3% precision using 11 GeV at JLab (with 1.5 m long target as in E158) • DIS-Parity: • Constraining radiative corrections and Higher Twist effects in current (E05-007) and future (11 GeV) DIS-PV experiments

14. Experimental setup and expected results

15. Experimental Setup: Graphics courtesy of www.jlab.org • Jefferson Laboratory Hall A • Plan to maximize overlap in setup with PV-DIS (E05-007) • Essentially same experimental setup with different kinematics • Use Hall A HRS spectrometers to simultaneously collect data at two kinematic points C A B Graphics courtesy of www.jlab.org

16. Experimental Setup Fast counting DAQ can take 1 MHz rate with 103 pion rejection Target density fluctuation, other false asymmetries measured by the Luminosity Monitor C, LD2, LH2 targets (highest cooling power) 4.8 GeV 85% polarized e- beam, 80 mA, DPb/Pb= 1.2% Electrons detected in two HRS independently Beam intensity asymmetry controlled by parity DAQ (demonstrated by HAPPEX)

17. Collaboration P. E. Bosted (spokesperson), E. Chudakov, V. Dharmawardane (co-spokesperson), A. Duer, R. Ent, D. Gaskell, J. Gomez, X. Jiang, M. Jones, R. Michaels, B. Reitz, J. Roche, B. Wojtsekhowski Jefferson Lab, Newport News, VA J. Arrington (co-spokesperson), K. Hafidi, R. Holt, H. Jackson, D. Potterveld, P. E. Reimer, X. Zheng (co-spokesperson) Argonne National Lab,Argonne, IL W. Boeglin, P Markowitz Florida International University, Miami, FL C Keppel Hampton University, Hampton VA E. Hungerford University of Houston, Houston, TX G. Niculescu, I Niculescu James Madison University, Harrisonburg, VA T. Forest, N. Simicevic, S. Wells Louisiana Tech University, Ruston, LA E. J. Beise, F. Benmokhtar University of Maryland, College Park, MD K. Kumar, K. Paschke University of Massachusetts, Amherst, MA F. R. Wesselmann Norfolk State University, Norfolk, VA Y. Liang, A. Opper Ohio University, Athens, OH P. Decowski Smith College, Northampton, MA R. Holmes, P. Souder University of Syracuse, Syracuse, NY S. Connell, M. Dalton University of Witwatersrand, Johannesburg, South Africa R. Asaturyan, H. Mkrtchyan (co-spokesperson), T. Navasardyan, V. Tadevosyan Yerevan Physics Institute, Yerven, Armenia Experienced PV collaboration (SLAC E158, HAPPEX, G0) And the Hall A Collaboration

18. Kinematics and Rates • Rates similar to PV-DIS (E05-007)—see talk by Xiaochao Zheng • Pion/electron ratio smaller • Low E0 settings in HRS-R, high E0 in HRS-L

19. Systematic Uncertainties • Statistical uncertainty--Always statistics limited • 4-6% per W bin • ¼ 2.5% integrated over full W range • EMC effect: Smaller systematic uncertainties on target ratios (about 1%)

20. Res-Parity Beam time requests • Strong synergy with PV-DIS E05-007 (see talk by Xiaochao Zheng) • Non-standard equipment: fast DAQ, upgraded Compton. Both required for E05-007 (PV-DIS) Total requirement: 30 daysof 80 mA, 85% Polarization, parity quality beam (mostly longitudinal, some transverse to measure 2-photon background)

21. Projected Uncertainties (W Binning) • Relative error of 5-7% per bin for 12 W bins shown (8-10% for H) • Local duality (3 resonance regions) tested to <4% (~5% for H) comparable to F2 and g1 • Global duality tested to <3% • Ratio of H/D (d/u) and C/D (EMC effect) tested to • 3-4% globally, • ¼5% locally: Nuclear effects in F2 are >10% PROTON DEUTERON, CARBON

22. Sato and Lee (1232) Projected Uncertainties ( Binning) • Relative error of 5-7% per bin for 12  bins shown (8-10% for H) • Local duality (3 resonance regions) tested to <4% (~5% for H) comparable to F2 and g1 • Global duality tested to <3% • Ratio of H/D (d/u) and C/D (EMC effect) tested to • 3-4% globally, • ¼5% locally: Nuclear effects in F2 are >10% PROTON DEUTERON, CARBON

23. Res-Parity: Summary • Easy measurement • Follow lead of PV-DIS@6GeV (E05-007) • New probe of • Resonance structure • Duality • EMC effect with weak probe • Z0 sensitive to different quark distribution combination • Measure Higher Twist constraints for PV-DIS • Constrain PV background to Møller Scattering experiments • Expt. currently proposed but deferred

24. Res-Parity: Summary • Easy measurement • Follow lead of PV-DIS@6GeV (E05-007) • New probe of • Resonance structure • Duality • EMC effect with weak probe • Z0 sensitive to different quark distribution combination • Measure Higher Twist constraints for PV-DIS • Constrain PV background to Møller Scattering experiments Exploration of Terra Incognita Map from Library of Congress