Spin dependent momentum distribution of proton in 3He studied via proton

induced exclusive knock-out reaction

CNS, Univ. of Tokyo 　 Y. Shimizu

I. Introductiona. 3N systemb. Proton polarization in polarized 3He

II. Experiment @ RCNPIII. Result

a. Comparison with calculationIV. Summary

Collaborators

• CNS, Univ. of TokyoT. Uesaka, T. Kawabata, K. Itho, Y. Sasamotno, S. Sakaguchi,T. Kawahara, H. Tokieda

• Univ. of TokyoH. 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 MiyazakiY. Maeda

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 B = B2N Bexp = 0.5 ~ 1.0MeV

The solution has been included 3NF.

• Extensions of the 3N scattering 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

K. Hatanaka et al., PRC 66, 044002 (2002).

NN onlyNN + TM3NF

• 3-body

• 2-body

Spin dependent momentum distribution

p d

J. Golak et al., PRC 72, 054005 (2005).

k

w/o D-state The calculated proton

polarization without D-state are differ visibly from the full calculation.

1PPp

full calc.

The momentum distribution of the proton polarization in polarized 3He is sensitive to the small 3He components.

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.

R.G. Milner et al., PLB 379, 67 (1996).

S-state only

full calc.

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.

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.

k ~ 40 MeV/c, E ~ 1 MeV3-body: < 20 MeV

PWIA onlyPWIA + re-scattering

J. Golak et al., PRC 72, 054005 (2005).

P. Achenbach et al., EPJ A 25, 177 (2005).

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 .

pNpNp

yyNyy CPC ),(He3

krecoil momentum

Pn

Pp

3He(p,pN): 197 MeV@IUCFM.A. Miller et al., PRL 74 502 (1995).

E ~ 20 MeV

• The poor resolution (E~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 (E~1MeV) would required

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 E = 1 MeV to distinguish 2-body and 3-body

breakup.

double arm spectrometer at RCNP

Experiment @ RCNP

Polarized 3He target

• Measurement 3He(p,2p)2H, 3He(p,2p)pn

• Observables Differential cross section d/d

(k = 0 – 300 MeV/c) Spin correlation parameter Cyy

(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,+)4He

Experiment @ RCNP

Beam

Scattered protonKnock out proton

GRLASPolarized 3He target

Diode laser Beam

MWDC

MWDC

100 mm

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.

Differential cross section2-body3-bodytotal

• 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.

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.

R.G. Milner et al., PLB 379, 67 (1996).

2-body3-bodytotal

pppp

yypyy CPC )2,(He3

The Faddeev calculation may underestimate the S’-state.

ORThe re-scattering mechanisms may be taken into account.

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.

d/d: consistent with existing data Pp : large discrepancy with

Faddeev calculation for 3-body break-up

We will measure the proton polarization at high momentum region, where the D-state contribution is dominant.

In future works,

Backup

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,+)4He reaction.

002

1

2

1 1yyC

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.

Max. 14 %Ave. 8 %