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

2 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 Z 0 and  e’ e P e’ e P Z0Z0  + 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 Q 2 < 1GeV 2 M proton < 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. c.f. earlier talk by M. Ramsey-Musolf at PAVI06 and review by Melnitchouk, Ent and Keppel, Phys. Rept (2005), hep-ph/ Graphic from Melnitchouk et al. Phys. Rept (2005) Will higher twist terms cancel similarly with the Z 0 probe in parity violation

4 Why Study Duality? Duality works extremely well for spin-averaged structure function to low values of Q 2. 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 Duality also appears to work for spin dependent structure functions for Q 2 > 1 GeV 2. JLab Hall C data as discussed in Melnitchouk et al. Phys. Rept (2005)

5 Resonance Region Asymmetry For inelastic scattering, A RL can be written in terms of response functions – –A 0 ¼ 6.5 £ ; – –L, T, T 0 denote longitudinal, transverse and axial; and – –V L,T,T 0 represent lepton kinematic factors. Sensitive to axial vector transition form factor, G A N  Details have so far been worked out only for N→∆(1232) – –c.f. JLab E and Jones and Petcov Phys. Lett. 91B 137 (1980)

6 Resonance Region Asymmetry For inelastic scattering, A RL can be written in terms of response functions Simple, “toy” model:  depends on sin 2  W ) Assume sin 2  W = 0.25 ) VA term disappears Pure magnetic or electric scattering No strange, charm contributions A RL Res ¼ -9£ Q 2 (  n /  p )

7 Duality for  -Z interference? 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 F 2, our goal is to measure A LR to ~5% locally and <3% globally Resonance model PROTON DIS model DATA NEEDED!

8 Resonance Region Asymmetry:  (1232)—significant departure from duality Sato and Lee predict significant departure from Duality for N!  A LR = 9 £ Q 2 (  V +  A )  A,V contain axial and vector contributions from neutral current A LR 2 £ larger than duality predictions! Duality Sato and Lee E=4 GeVE=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 A RL 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 Resonance region probed by Res-Parity dominates total cross section for 1 < E  < 5 GeV, important to MINER A and MINOS neutrinoantineutrino 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

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 Q 2 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: Use Hall A HRS spectrometers to simultaneously collect data at two kinematic points A B C Graphics courtesy of Jefferson Laboratory Hall A Plan to maximize overlap in setup with PV-DIS (E05-007) – –Essentially same experimental setup with different kinematics

16 Experimental Setup Electrons detected in two HRS independently Fast counting DAQ can take 1 MHz rate with 10 3 pion rejection C, LD2, LH2 targets (highest cooling power) 4.8 GeV 85% polarized e - beam, 80  A,  P b /P b = 1.2% Beam intensity asymmetry controlled by parity DAQ (demonstrated by HAPPEX) Target density fluctuation, other false asymmetries measured by the Luminosity Monitor

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 E 0 settings in HRS-R, high E 0 in HRS-L Deuterium Kinematics, Rates, etc. xYQ2Q2 E0E0 W ee MHz  A/A % % % %

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%) Source  A/A Beam Polarization0.012 Kinematic Determination of Q Electromagnetic radiative corrections0.008 Beam asymmetry0.005 Pion contamination0.005 DAQ deadtime and pile-up effects0.003 Pair symmetric background0.002 Target purity and density Fluctuations0.002 Pole-tip background0.001 Total0.018

20 Res-Parity Beam time requests Strong synergy with PV-DIS E (see talk by Xiaochao Zheng) Non-standard equipment: fast DAQ, upgraded Compton. Both required for E (PV-DIS) E Target P HRS (L,R) time 4.8 GeV LH2 4.0, 3.2 GeV 5 days 4.8 GeV LH2 3.6, 2.8 GeV 4 days 4.8 GeV LD2 4.0, 3.2 GeV 4 days 4.8 GeV LD2 3.6, 2.8 GeV 4 days 4.8 GeV C 4.0, 3.2 GeV 6 days 4.8 GeV C 3.6, 2.8 GeV 6 days Pass Change from E hours Polarization measurements 8 hours e + asymmetry 8 hours Total requirement: 30 days of 80 mA, 85% Polarization, parity quality beam (mostly longitudinal, some transverse to measure 2- photon background)

21 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 F 2 and g 1 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 F 2 are >10 % Projected Uncertainties (W Binning) PROTON DEUTERON, CARBON

22 Projected Uncertainties (  Binning) PROTON DEUTERON, CARBON 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 F 2 and g 1 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 F 2 are >10 % Sato and Lee  1232)

23 Res-Parity: Summary Easy measurement –Follow lead of (E ) New probe of –Resonance structure –Duality EMC effect with weak probe –Z 0 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 Easy measurement –Follow lead of (E ) New probe of –Resonance structure –Duality EMC effect with weak probe –Z 0 sensitive to different quark distribution combination Measure Higher Twist constraints for PV-DIS Constrain PV background to Møller Scattering experiments Res-Parity: Summary Exploration of Terra Incognita Map from Library of Congress