Nuclear Effects in Electron Scattering

1. Nuclear Effects in Electron Scattering Arie Bodek University of Rochester Un-ki Yang University of Manchester NuFact 2008, Valencia, Spain, Jun 30 - July 5, 2008 Un-ki Yang, Manchester

2. Nuclear Effect in Electron Scattering (A)/ (d ): EMC effect • Of theoretical interest • Shadowing • Binding • Fermi motion •  exp. (osc. / non-osc.) with all heavy targets wants: • (A) • (A)/ (d) • This is what electron data can offer using with light & heavy target as a good reference Un-ki Yang, Manchester

3. Neutrino Cross Sections • Quasi-Elastic / elastic (W=M): nm + n m- + p • by form factors • Resonance (low Q2, W< 2): nm + p m- + p + p • by Rein and Seghal model (overlap with DIS) • Deep Inelastic Scattering: nm + p m- + X • by quark-parton model (non-pQCD effect, high x PDFs) • Describe DIS, resonance within quark-parton model: with PDFS, it is easy to convert (e) into () • () for deuterium (d): (d,e) • Nuclear effect in d : d/u issue at high x • (A,) = (d,) * [ (A,e) / (d,e)] • Good reference to study nuclear effect •  vs e, vector vs axial-vector, F2 vs xF3 Un-ki Yang, Manchester

4. Modeling on (e) for p and d q F2 GRV • Describe all processes, even photo-production (Q2=0) within quark-parton model • Challenge: • High x PDFs (d/u) • Non-pert. QCD at low Q2 • Nuclear effect in the deuterium? • Resonance scattering in terms of quark-parton model? (duality) Un-ki Yang, Manchester

5. Unified Approach mf=M* (final state) q P=M • NNLO pQCD +TM approach:describes the DIS and resonance data very well: • A phenomenological HT from the NLO analysis: ~ NNLO pQCD term • Effective LO approach: (pseudo NNLO for MC) Use a LO PDFs with a new scaling variable to absorb TM, HT, higher orders Un-ki Yang, Manchester

6. Fit withxw DIS F2(d) • Use GRV98 LO • xw= [Q2+B] / [ Mn (1+(1+Q2/n2)1/2 ) +A] • Different K factors for valence and sea • Ksea = Q2/[Q2+Csea] Kval = [1- GD2 (Q2) ] *[Q2+C2V] / [Q2+C1V], GD2 (Q2) = 1/ [ 1+Q2 / 0.71 ] 4 (separate u, d val. ?) • Freeze the evolution at Q2 = 0.8 • Very good fits are obtained using SLAC/NMC/BCDMS p, dwith low x HERA/NMC F2 A=0.418, B=0.222, Csea = 0.381 C1V = 0.604, C2V= 0.485 2/DOF= 1268 / 1200 Un-ki Yang, Manchester

7. Resonance and photo-production data F2(d) resonance Photo-production (p) s(g-proton) = 4pa/Q2 * F2(w, Q2) where F2(w, Q2) = Q2 /(Q2 +C) * F2(w ) Not included in the fit Un-ki Yang, Manchester

8. DIS at low x Un-ki Yang, Manchester

9. 2xF1 data? • All DIS F2 at high/low x e/ data are well described • Photo-production data (Q2=0) also work: thus included in the latest fit • 2xF1 data (Jlab/SLAC) also work: using F2(w)+R1998

10. Comparison with high E () data En= 55 GeV • Assume vector = axial • Apply nuclear corrections using e/ scattering data • Use R=Rworld fit for 2xF1 • But total (anti-neutrino) appear to be higher by 5%, xF3 issue? (w)---- (x)

11. NLO Correction to xF3? • Scaling variable, w absorbs higher order effect on F2 • Higher order effect on F2 and xF3 : not same • Check double ratio => not 1 but indep. of Q2 NLO VFS Un-ki Yang, Manchester

12. NLO Correction to xF3 • (anti-neutrino): up by 3% while (neutrino): down by 1% for all energy range. Un-ki Yang, Manchester

13. Nuclear Effect in Electron Scattering (A)/ (D ): EMC effect F2 x • Nuclear effect (x) in DIS at high Q2: • Do we see the same nuclear effect(x) in the resonance region? • Jlab data: yes but using Nachtmann variable  Un-ki Yang, Manchester

14. Nuclear effect in Resonance and DIS • Comparison of resonance (JLAB) & DIS (SLAC/NMC) carbon iron Good agreement in  Un-ki Yang, Manchester

15. A-dependence of Nuclear Effect 4He 12C • Is nuclear effect scaled up with A number? • Carbon and 4He Jlab data results favor density dep. nuclear effect • Need to be careful about non-iso target correction Un-ki Yang, Manchester

16. Nuclear Effect in the Deuterium? • Nuclear effect in d can be 4%, extrapolated using nuclear density • Agree with Melinichouk & Thomas calculation • Consistent with all DIS with all DIS e/ F2 , Tevatron W asym. • Correlated with d/u issue PRL 1998 Bodek-Yang Un-ki Yang, Manchester

17. d/u at high x • Large change in d/u at high x due to nuclear effect in d • Larger impact on (d,) • Same conclusion from Thomas &, Mel. and CTEQ in 1998 • Indep. measurements need; • HERA CC (e-/e+) • Tevatron W asym. at high- with larger lepton pt cut or LHC? • Jlab measure of nearly on-shell n by tagging slow p: ed->epX? • Interesting results from NuTeV and E866 DY data: See Morfin’s talk • NuTeV: u+d (higher?) • E866 DY: 4u+d (lower?) Un-ki Yang, Manchester

18. Dedicated efforts to prove d/u at high x from Jlab (reference) • Measure SF of nearly on-shell n by detecting slow spectator p in semi-inclusive ed -> ep X reaction : JLab CLAS++, BONUS exp. (almost scattering off free nucleon) • Parity violation in DIS on 1H: very sensitive to d/u Un-ki Yang, HQL 2008

19. Summary and Discussions • Effective LO model with w describe all DIS and resonance data as well as photo-production data: • Provide a good reference for (,d) • With (A)/ (d)from e/, provide (,A), (A)/ (d) for  ; any deviation => different nuclear effect (vector vs axial: valence vs sea) in  scattering • (A)/ (d)from e/ • Scaling with Nachtman variable,  regardless of DIS and resonance • Favors scaling with nucleon density, instead of A • Need to understand nuclear effect in d or d/u at high x • More Jalb data are coming, and neutrino data are absolutely needed (K2K, SciBooNE, MiniBooNE, and Minerva etc) Un-ki Yang, Manchester

20. Nuclear effect from Jlab (backup) Un-ki Yang, Manchester