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CNS, Univ. of Tokyo Y. Shimizu

Spin dependent momentum distribution of proton in 3 He studied via proton induced exclusive knock-out reaction. CNS, Univ. of Tokyo Y. Shimizu. Introduction 3N system Proton polarization in polarized 3 He Experiment @ RCNP Result Comparison with calculation Summary. Collaborators.

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CNS, Univ. of Tokyo Y. Shimizu

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  1. Spin dependent momentum distribution of proton in 3He studied via proton induced exclusive knock-out reaction CNS, Univ. of TokyoY. Shimizu • Introduction • 3N system • Proton polarization in polarized 3He • Experiment @ RCNP • Result • Comparison with calculation • Summary

  2. Collaborators • CNS, Univ. of Tokyo T. Uesaka, T. Kawabata, K. Itho, Y. Sasamotno, S. Sakaguchi, T. Kawahara, H. Tokieda • Univ. of Tokyo H. Sakai, K. Yako, K. Sasano • Kyushu Univ. T. Noro, T. Wakasa, Y. Yamada, M. Dozono • RCNP, Osaka Univ. K. Hatanaka, H. Okamura, A. Tamii, H. Matsubara • CYRIC, Tohoku Univ. T. Wakui, H.P. Yoshida • Univ. of Miyazaki Y. Maeda

  3. 3N system • The 3N bound states have been calculated by using Faddeev equation with the modern NN potentials. • Under binding problem of the 3N system • DB = B2N- Bexp = -0.5 ~ -1.0MeV  The solution has been included 3NF. • Extensions of the 3Nscattering states • p+d elastic scattering • Cross section O.K. • Spin observables ???  Suggest defects in spin dependence • REVISIT the 3N bound state • The structure of 3He has not been clearly understood yet. • Spin dependent momentum distribution NN only NN + TM3NF K. Hatanaka et al., PRC 66, 044002 (2002).

  4. Spin dependent momentum distribution full calc. • For the S-state alone, the proton polarization is zero independent of proton momentum. • The polarization deviate from zero due to the small components, in particular S’-state. • 3-body • 2-body S-state only R.G. Milner et al., PLB 379, 67 (1996). • The calculated proton polarization without D-state are differ visibly from the full calculation. w/o D-state full calc. d p The momentum distribution of the proton polarization in polarized 3He is sensitive to the small 3He components. J. Golak et al., PRC 72, 054005 (2005). k

  5. 3He(e,e’p) • The 3He(e,e’p) experiment would require.  This experiment is very demanding. • The electron target asymmetries in the 3He(e,e’p) 2H and 3He(e,e’p)pn can be simply related to the proton polarization in 3He.  The experiment was carried out at MAMI. J. Golak et al., PRC 72, 054005 (2005). P. Achenbach et al., EPJ A 25, 177 (2005). k ~ 40 MeV/c, DE ~ 1 MeV 3-body: < 20 MeV PWIA only PWIA + re-scattering • The measured asymmetries are well reproduced by the PWIA calculations including re-scattering. • For 3-body configuration, strong re-scattering effects are observed. • To study the 3He spin structure in more detail, the measurement of the momentum distribution of these asymmetries are required.

  6. 3He(p,2p) • In the PWIA, the spin correlation parameter can be related to the nucleon polarization by . • 3He(p,pN): 200 and 290 MeV @ TRIUMF • 3He(p,pN): 197 MeV @ IUCF • The neuron polarization is almost one due to the S-state. • The proton polarization has negative value at low momentum due to the S’-state . Pn Pp k recoil momentum • The poor resolution (DE~20MeV) could not allow the separation of the 2-body and 3-body contributions. • To study the 3He spin structure in more detail, the high resolution (DE~1MeV) would required 3He(p,pN): 197 MeV@IUCF M.A. Miller et al., PRL 74 502 (1995). DE~ 20 MeV

  7. New Experiment • Proton polarization in polarized 3He • The 3He(p,2p) reaction is a suitable tool to measure the proton polarization in polarized 3He experimentally. • The kinematical setting satisfied that the Cyy of pp elastic scattering was large and independent of momentum • Minimum suppression of re-scattering effects • 400 MeV proton beam  Recoiled protons have E ~ 200 MeV • Large momentum transfer : q > 500 MeV/c  The re-scattering effects are small enough to extract the proton polarization from the (p,2p) reaction. • High resolution • require DE = 1 MeV to distinguish 2-body and 3-body breakup.  double arm spectrometer at RCNP

  8. Experiment @ RCNP • Measurement • 3He(p,2p)2H, 3He(p,2p)pn • Observables • Differential cross sectionds/dW (k = 0 – 300 MeV/c) • Spin correlation parameterCyy (k = 0, 100 MeV/c) • Polarized proton • Energy : 392 MeV • Polarization : 50 % • Intensity : 50 nA • Polarized 3He target • Spin exchange method • Polarization：　8% (Max. 14 %) • Monitor by AFP-NMR method • Calibrated by 3He(p,p+)4He Polarized 3He target

  9. Experiment@ RCNP GR Polarized 3Hetarget LAS Scatteredproton Knock out proton MWDC MWDC 100 mm Beam Diode laser Beam

  10. Spectra of 3He(p,2p) • The resolution of 1.1 MeV allowed a clear separation into the two final state channels. • The cut for the 3-body channel was made from 2.2 to 30 MeV.

  11. 2-body 3-body total Differential cross section • The cross sections normalized by the value at 0 MeV/c are consistent with other experimental data. • The ratio of the 3-body to the total increases with the proton momentum.

  12. Proton polarization in 3He • For the 2-body, our results are in good agreement with the calculation. • For the total, our results are consistent with other experimental data. • For the 3-body, our results are larger and same in sign compared to the calculation. The Faddeev calculation may underestimate the S’-state. OR The re-scattering mechanisms may be taken into account. 2-body 3-body total R.G. Milner et al., PLB 379, 67 (1996).

  13. Summary • Spin dependent momentum distribution of proton in 3He • Under biding problem of light nuclei • Spin dependences of 3NF • The spin correlation parameters Cyy of 3He(p,2p)2H and 3He(p,2p)pn reactions were measured at RCNP for the first time. • The resolution of 1.1 MeV allowed a clear separation into the two final state channels. • ds/dW: consistent with existing data • Pp : large discrepancy with • Faddeev calculation for 3-body break-up In future works, We will measure the proton polarization at high momentum region, where the D-state contribution is dominant.

  14. Backup

  15. Target Polarization • 3He polarization was monitored by AFP-NMR method. • In order to calibrate the 3He polarization, we measured the Cyy of the 3He(p,p+)4He reaction. Max. 14 % Ave. 8 % Polarization was very low because of three sources. A) Magnetic field inhomogeneity at experimental hall  Improvement in the magnetic shield of Q-magnet. B) Insufficient laser power  Combination of the two or three diode lasers. C) Short relaxation time  Fabrication of the target cell with cesium coated glass.

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