Spin structure of 3 He studied by deuteron and nucleon knockout processes

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1 Spin structure of 3 He studied by deuteron and nucleon knockout processes S. Širca, U. of Ljubljana, Slovenia Electron-Nucleus Scattering XIII Marciana Marina, Isola d Elba 25 June

2 Experiments covered in this talk E (Gilad, Higinbotham, Korsch, Norum, Širca) Double-spin asymmetries in quasi-elastic 3 He( e, e d)p 3 He( e, e p)d 3 He( e, e p)pn E (Averett, Chen, Xiang) Target single-spin asymmetry in quasi-elastic 3 He (e, e ) E (Averett, Higinbotham, Sulkosky) Target single-spin asymmetry in quasi-elastic 3 He (e, e n) Double-spin asymmetries in quasi-elastic 3 He( e, e n) Project N (Sfienti, Pohodzalla, Distler) Subproject (Distler): triple-polarized 3 He( e, e p) Analysis work done by Elena Long (Kent State U) Miha Mihovilovič (U of Ljubljana) Yawei Zhang (Rutgers) Markus Weinriefer (Mainz) 2

3 Physics motivation for studying processes on 3 He Knowledge of ground-state structure of 3 He needed to extract information on the neutron from 3 He( e, e X) or 3 He( e, e ). Examples: G n E, Gn M, An 1, gn 1, gn 2, GDH. Complications: protons in 3 He partly polarized due to presence of S - and D-state components. Addressing differences in r 2 ( 3 H, 3 He). Understanding (iso)spin dependence of reaction mechanisms (MEC, IC). Understanding role of D and S states is one of key issues in Standard Model of few-body theory. Persistent discrepancies among theories regarding double-polarization observables most sensitive to 3 He ground-state structure. 3

4 Polarized 3 He: it is easy to draw the cartoon... S S D Hamiltonian S S P D p n p p n p p n p AV AV18/TM AV18/UIX S: spatially symmetric 90 % of spin-averaged WF; polarized neutron D: generated by tensor part of NN force, 8.5 %. S : mixed symmetry component; (spin-isospin)-space correlations, 1.5 %. P S E 2.1 b. P eff n CD-Bonn CD-Bonn/TM Nijm I Nijm I/TM Nijm II Nijm II/TM Reid Reid93/TM , P eff p 0.03 Schiavilla++ PRC 58 (1998) 1263 TM = Tucson-Melbourne π-π exchange 3NF UIX = Urbana 3NF 4

5 ...supported e.g. by data on 3 He( e, e p)d/pn... quasi-elastic (Q 2 = 0.31, ω = 135, q = 570) 3NF, MEC negligible, FSI small in 2bbu, large in 3bbu A pd A 1 + t A 2 asymmetry BB 3BB 3BB target spin direction 2bbu A PWIA A PWIA+FSI kinematics + small p d polarized p target, P p 1 3 P He 3bbu A PWIA 0 (p p ) A PWIA+FSI large & negative not a polarized p target PRC 72 (2005) , EPJA 25 (2005) 177 5

6 ...and which has a nice analogue in the deuteron... d( e, e p) 0.2 PWIA (S only) PWIA (S+D) PWBA+FSI PWBA+FSI+MEC PWBA+FSI+MEC+IC FULL A V ed 0 S+D -0.2 S only p m [MeV/c] σ = σ 0 (1 + hp1 d AV ed ( ) Pz p = P S 1 2 P D 2 3 ) P d 1 Passchier++ PRL 82 (1999) 4988 Passchier++ PRL 88 (2002)

7 ...but the true ground state of 3 He is like lace Blankleider, Woloshyn PRC 29 (1984) 538 7

8 Meeting point of theory and experiment e.g. 3 He( e, e d) dσ (h, S) = dσ 0 dω e de e dω d dp d [ ] 1 + S A 0 + h(a e + S A) A x,z = [ dσ ++ + dσ ] [ dσ + + dσ + ] [ dσ ++ + dσ ] + [ dσ + + dσ + ] 8

9 The E and E experiments at JLab Benchmark measurement of A x and A z asymmetries in 3 He( e, e d), 3 He( e, e p), and 3 He( e, e n). Better understanding of ground-state spin structure of polarized 3 He S, S, D wave-function components. Improve knowledge of 3 He rather than using it as an effective neutron target. Direct consequences for all polarized 3 He experiments. A1n Errors Statistical Experimental Systematics Radiative Correction F 2 A 1 p P p P n Distinct manifestations of S, D, S with changing p miss in (e, e {p/d/n}). Data at (almost) identical Q 2 for ( e, e d), ( e, e p), and ( e, e n) simultaneously over a broad range of p miss poses strong constraints on state-of-the-art calculations x Bjorken 9

10 What is so special about 3 He(e, e d) and 3 He( e, e d)? unique isoscalar-isovector interference in (e, e d) Tripp++ PRL 76 (1996) in (e, e p) the D/S effects seen only at high p miss Laget PLB 276 (1992) 398

11 Exploiting state-of-the-art calculations Bochum/Krakow (full Faddeev) AV18 NN-potential (+ Urbana IX 3NF, coming up...) Complete treatment of FSI, MEC Hannover/Lisbon (full Faddeev) CC extension and refit of CD-Bonn NN-potential Includes FSI, MEC as active degree-of-freedom providing effective 3NF and 2-body currents Coulomb interaction for outgoing charged baryons Pisa PRC 72 (2005) AV18 + Urbana IX (or IL7) Inclusion of FSI by means of the variational PHH expansion and MEC Not Faddeev, but accuracy completely equivalent to it Trento Coming up 11

12 Basic machinery: Faddeev calculations Nuclear transition current for breakup of 3 He: J µ = Ψ f Ô µ Ψ3 He(θ, φ ) Photon absorption operator: Ô µ = ] 3 i=1 [ĴSN (i) + Ĵ MEC (i) Final-state interactions (auxiliary states): Ψ f Ô µ Ψ3 He(θ, φ ) Ψ f U µ f U 0 ppn = PWIA + MEC U 0 pd = PWIA + MEC G more terms more terms more terms more terms

13 Role of WF components in 3 He( e, e d) Krakow/Bochum 13

14 Indication of D and S components in 3 He( e, e ) Inclusive A T (= A z) and A LT (= A x) AT [%] Gao PRC 50 (1994) R546 Xu PRL 85 (2000) 2900 PWIA PWIA(PS) ATL [%] Jones PRC 52 (1995) 1520 Hansen PRL 74 (1995) 654 (e,e d) (e,e p) ω [MeV] ω [MeV] A LT receives contributions from ingredients which go beyond most simplistic picture [ F (n) 1 = 0 ] sensitive to replacement PWIA(PS) PWIA. S - and D-state pieces contribute very strongly to A LT Ishikawa, Golak, Glöckle et al. PRC 57 (1998) 39 14

15 3 He( e, e d) vs. 3 He( e, e p) Krakow/Bochum 15

16 How do we do it? Experimental Setup 16

17 Experiment E in Hall-A Detected Electron Incident polarized electron θ L Beam Helicity γ * p p n θ q A z A x n p p Detected Deuterons and Protons 17

18 Acceptance-averaging of 3 He( e, e p) and 3 He( e, e d)p Krakow/Bochum Hannover/Lisbon Pisa Hannover/Lisbon 18

19 Comparison with the theory 3 He( e, e d)p A(θ * =160 o,φ * =0 o ) A(θ * =71 o,φ * =0 o ) E (JLab 2009) Hannover/Lisbon Bochum/Krakow Pisa PRELIMINARY p m [MeV/c] 19

20 Comparison with the theory 3 He( e, e d)p A(θ * =160 o,φ * =0 o ) E (JLab 2009) Hannover/Lisbon Bochum/Krakow Pisa A(θ * =71 o,φ * =0 o ) QE PRELIMINARY QE ω [MeV] 20

21 The question of P z and P zz 3 He( e, e d)p assume 3 He( e, e d)p at low p miss is like elastic scattering off polarized d use A (3 He) x, A (3 He) z as if they were A (ed) x, A (ed) z and extract P z and P zz with appropriate deuteron FFs, toy model 3 He = d + p spin decomposition 3 He = 1 2, 1 = , 1 1 2, , 0 1 2, 1 2 gives P z = I z 3 He = 2 3, P zz = 3Iz He = 0 P zz E (JLab 2009) Hannover/Lisbon Bochum/Krakow Pisa P z 21

22 Preliminary results for asymmetries in 3 He( e, e p) E = GeV E = GeV ω = MeV ω = MeV Q 2 = (GeV/c) 2 Q 2 = (GeV/c) 2 22

23 Hand-waving interpretation of 3 He( e, e p) 23

24 Comparison with the theory 3 He( e, e p) PRELIMINARY NB: 2bbu and 3bbu combined, Krakow/Bochum theory only 24

25 Single-spin asymmetry in QE 3 He (e, e ) Motivation A y = σ σ σ + σ s ( k k ) A y = 0 in Born approximation (T -invariance) A y 0 indicative of 2γ effects, Im{ T 1γ T2γ } interference; relevant for G p E /Gp M, GPDs no measurement of comparable precision on neutron 25

26 Single-spin asymmetry in QE 3 He (e, e ) E A y ( θ) = A y (θ) 26 Figure & table courtesy of Yawei Zhang, Rutgers

27 Single-spin asymmetry in QE 3 He (e, e ) E He neutron (%) -0.1 He 3 A y -0.2 (%) A n y Elastic Only Q (GeV ) -4 PRELIMINARY Mod. Regge GPD Experimental Data Q (GeV ) first measurement of A n y (i.e. extraction from A 3 He y ) uncertainty several times better than previous proton data Figures courtesy of Yawei Zhang, Rutgers 27

28 Single-spin asymmetries in QE 3 He ( e, e n) E a measure of the magnitude of MEC and FSI should be zero in PWIA and should die out at high Q 2 A y JLab E NIKHEF MAMI PRELIMINARY Q 2 (GeV/c) 2 Figure courtesy of Elena Long, UNH 28

29 Single-spin asymmetries in QE 3 He ( e, e n) E Q 2 =0.13 (GeV/c) 2 Q 2 =0.46 (GeV/c) 2 A y A y ν (GeV) Q 2 =0.95 (GeV/c) ν (GeV) A y ν (GeV) PRELIMINARY Figures courtesy of Elena Long, UNH 29

30 Double-spin asymmetries in QE 3 He( e, e n) E Q 2 = 0.5 Q 2 = 0.95 AL for Q2=0.505 (GeV/c) AL for Q2=0.953 (GeV/c) AT for Q2=0.505 (GeV/c) QE ν (GeV) ν (GeV) AT for Q2=0.953 (GeV/c) ν (GeV) ν (GeV) *** VERY PRELIMINARY *** Figures courtesy of Elena Long, UNH 30

31 Triple-polarized 3 He( e, e p) MAMI/A1 PWIA: σ L, σ T, σ T yield spin-dependent momentum distribution FSI, MEC preclude direct access except at p d 2 fm 1 rich interplay final-state symmetrization: large effect in C 3 FSI: largest in C 2 MEC: most prominent in C 1 C1 C2 C3 Q Q Q p N p d p N p N p d p d q / MeV/c ω / MeV Figure courtesy of Michael Distler, JGU Mainz 31

32 Ñ Ñ Triple-polarized 3 He( e, e p) MAMI/A1 spin-dependent momentum distributions of p d clusters in polarized 3 He Golak++ PRC 65 (2002) N µ = Ψ ( ) pd M dm ĵµ( q) ΨM ( Y M = 1 2, M d = 0, m = + 1 ) 2 ( Y M = 1 2, M d = 1, m = 1 ) 2 A = N N Y(1/2, 0, 1/2) Y(1/2, 1, 1/2) Y(1/2, 0, 1/2) + Y(1/2, 1, 1/2) σ L N 0 2 σ T N N 1 2 σ T N +1 2 N 1 2 spin PWIA 1 spin PWIA +1 ½¼ ½ ( ) 1 2 ½¼ 2, 0, 1 ½¼ 2 ½¼ ( ) ¼ ¾¼¼ ¼¼ 1 2 Õ 2, 1, +1 ¼ Šλ ½¼ 2 ½ ½¼ ½¼ ½¼ ½¼ ¼ ¼¼ ¾¼¼ ¼¼ ¼¼ Õ ¼ Šλ PRELIMINARY ¼¼ ¼¼ 32

33 Thank you! 33

34 Dynamics ingredients 3 He( e, e d) Krakow/Bochum 34

35 Dynamics ingredients 3 He( e, e d) Hannover/Lisbon 35

36 Relative size of FSI effects for 3 He(e, e d) Meijgaard, Tjon PRC 42 (1990) 96 36

37 Sensitivity to the S component Krakow/Bochum 37

38 SSA in QE 3 He (e, e ) (details) E Extraction of A n y from A 3 He y effective polarization approximation: A 3 He y = P n f n A n y + P p (1 f n )A p y f n = σ n σ 3 He = σ n 2σ p + σ n P p = 0.86 ± P n = ± high Q 2 : f n computed with Kelly s parameterization of nucleon FFs low Q 2 : theoretical estimate (due to FSI): f n = (A. Deltuva) A p y computed by Afanasev et al. 38