1. FSU, Tallahassee FL USA May 2016 Eli Piasetzky Tel Aviv University, ISRAEL 12 C Measurement of polarization transferred to a proton bound in nuclei MAMI / A1

2. Nucleons are complex objects. Are nucleons being modified in the nuclear medium ? meson cloud Free neutron Bound neutron Do nucleons change their quark-gluon structure in the nuclear medium ? Do nucleons change global properties (radius, mass...) ? In-Medium vs. Free Structure Function In-Medium vs. Free Form Factors The challenge is to observe or exclude evidence for changes in the bound nucleon compare to a free one.

3. Which nucleons are modified ? Mean field SRC np pp nn V(r) (ρ 0 =0.17 fm -3 )

4. Deep Inelastic Scattering (DIS) E E` (,q)(,q) nucleon Final state Hadrons W2W2 Incident lepton E, E’ 5-500 GeV Q 2 5-50 GeV 2 w 2 >4 GeV 2 0 ≤ X B ≤ 1 x B gives the fraction of nucleon momentum carried by the struck parton Information about nucleon vertex is contained in F 1 (x,Q 2 ) and F 2 (x,Q 2 ), the unpolarized structure functions scattered lepton Electrons, muons, neutrinos SLAC, CERN, HERA, FNAL, JLAB

5. The European Muon Collaboration (EMC) effect per nucleon in nuclei ≠ per nucleon in deuteron DIS off a bound nucleon ≠ DIS off a free nucleon? ? Is modification caused by mean-fields (modify all nucleons all the time) or by SRCs which modify some nucleons some of the time ? A bound nucleon ≠ A free nucleon? ?

6. EMC effect SLAC E139 data for iron and gold Calculations predict changes in the quark structure function due to the mean scalar and vector fields in the nucleus. In-Medium structure Functions ≠ Free

7. PRL 106, 052301 (2011), also PRC 85 047301 (2012) SRC EMC the EMC effect is associated with large virtuality ( )

8. Hypothesis can be verified by measuring DIS off Deuteron tagged with high momentum recoil nucleon EMC 12 GeV JLab/ Hall C approved experiment E 12-11-107 Tagged recoil proton measure neutron structure function Tagged recoil neutron measure in the proton structure function 12 GeV JLab/ Hall B approved experiment Is the EMC effect associated with large virtuality ?

9. Do nucleons change global properties (radius, mass...) ? In-Medium vs. Free Form Factors Deep Inelastic Scattering (DIS) Qasi Free Scattering (QF) The observable of choice: The recoil polarization of a knockout proton in quasi-elastic scattering

10. The observable of choice: The polarization of the knockout proton in quasi-elastic scattering * obtained from a single measurement with syst. and stat. uncertainties ~1%. * sensitive to the properties of the nucleon (size, charge dist… * only moderately sensitive to MEC, IC, FSI. * Minimal affected by radiative corrections. * G Ep /G Mp

11. The polarization of the knockout proton in quasi-elastic scattering

12. QF 4 He ≠ free proton Jlab E03-104 Data S. Dieterich et al. PL B500, 47 (2001). S. Strauch et al. PRL. 91 052301 (2003). M. Paolone et al. PRL. 91 052301 (2003). Calculations by the Madrid group Can be explained by: Medium FF≠ Free CQS: Chiral Quark Soliton QMC: Quark Meson Coupling Also proposed SCX FSI ≠ calc. with free FF Px/Pz polarization transferred ratio

13. bound nucleon ≠ free nucleon BUT The local nuclear density The virtuality (momentum off -shellness) of the nucleon Px/Pz polarization transferred ratio Is it due to in-medium FF modification ? Does it depend on ? Use a large-virtuality bound proton in the deuteron s- and p- shell removal

14. MAMI / A1 -

15. MAMI / A1 June –July 2012 data - Setup Name B/C (e’) Pmiss [MeV/c] K30_H0.4C038482.4668-34.7932 K300.4C038482.4668-34.7921 K180.4C150462.873.8495-43.31874 G900.175C186397.649.4665-39.160191 G910.175B50508.643.4484-53.3159245 Virtuality range 4 He data This experiment Q2Q2 4 He data

16. * Deuteron QF ≠ free * Strong virtuality dependence * No Q 2 dependence neutronproton neutron Px/Pz polarization transferred ratios JLab (Hu et al.) Q 2 =, 0.43 1.00 MAINZ Q 2 = 0.175, 0.4 [(GeV/c) 2 ]

17. No Nuclear density (B.E.) dependence ! neutronproton neutron

18. H. Arenhovel (7 models) 1.NORMAL (DWIA) 2.PWBA 3.NORMAL+MEC 4.NORMAL+MEC+IC 5.NORMAL+REL 6.PWBA (RC) 7.NORMAL+MEC+IC+REL Compare to calculations with free FFs

19. Compare to calculations (free FFs) neutronproton neutron * The virtuality dependence is reproduced by the calculations

20. What produce the virtuality dependence ? neutronproton neutron FSI

21. Effect of first order relativistic correction: neutronproton neutron

22. Compare to calculations (Free FFs) neutronproton neutron * Calculation with FF are below the data Why ?

23. Compare to Free FFs calculations 10 % is a large deviation ! Changing NN potential AV18  Bonn Changing FFs shape to dipole Changing FFs for free proton and neutron (within measured )unceratinties 1-2 % Calculations > data Calculation < data

25. Dependent on nuclear local density: Ron, Cosyn, Piasetzky, Ryckebusch, Lichtenstat, PRC87,028208 (2013). s- and p- shell removal preliminary 12 C data

26. Very preliminary 12 C data neutronproton neutron Very preliminary 12 C data

27. get better coverage of x B <1 range neutronproton neutron July 2016

28. Summary smooth virtuality dependence. no Q 2 – dependence. No nuclear density (binding energy) dependence. calculations predicts the smooth virtuality dependence (FSI). The calculations are off by an overall 10%. Why ? Is it a “baryon” or “nuclear” issue ? Deuteron QF ≠ free

29. Polarization-transfer measurement to a large-virtuality bound proton in the deuteron My colleges : A1 Collaboration: I. Yaron, D. Izraeli,P. Achenbach, H. Arenhövel, J. Beričič, R. Böhm, D. Bosnar, L. Debenjak, M., O. Distler, A. Esser, I. Friščić, R. Gilman, I. Korover, J. Lichtenstadt, H. Merkel, D. G. Middleton, M. Mihovilovič, U. Müller, E. Piasetzky S. Širca, S. Strauch J. Pochodzalla, G. Ron, B. S. Schlimme, M. Schoth, F. Schulz, C. Sfienti, M. Thiel, A. Tyukin, A. Weber.A1 CollaborationI. YaronD. IzraeliP. AchenbachH. ArenhövelJ. BeričičR. BöhmD. BosnarL. DebenjakO. DistlerA. EsserI. FriščićR. GilmanI. KoroverJ. LichtenstadtH. MerkelD. G. MiddletonM. MihovilovičU. MüllerE. PiasetzkyS. ŠircaS. StrauchJ. PochodzallaG. RonS. SchlimmeM. Schoth F. SchulzC. SfientiM. ThielA. TyukinA. Weber Nucl-ex arXiv:1602.06104 Acknowledgment and the organizers for the invitation. Volker Crede Winston Roberts