1. Center for Nuclear Study, University of Tokyo
Nuclear/Hadron spectroscopy with spin/isospin filtering techniques ~ with prospect of future project at RCNP ~
KAWABATA Takahiro and
UESAKA Tomohiro
Center for Nuclear Study, University of Tokyo

2. Nuclear Spectroscopy @ RCNP
Missing mass spectroscopy with a direct nuclear reaction.
Simple reaction mechanism at a few hundreds MeV/u.
- Good linearity between ds/dW and B(ô).
Various probes with spin/isospin selectivity are utilized.
Selectivity for the DT = 1 and DT = 0 components.
Spin filtering using Polarization Transfer (PT) observables.
(3He,t) … DT = 1 only (DTz = -1)
(d,d’) … DT=0 only (DTz =0)
(a,a’) ... DT=0 and DS=0 only
(p,p’) … DT = 1 and DT = 0 (DTz = 0)

3. Isospin filtering for 11B
IS/IV M1 strengths in 11B are successfully determined utilizing the three probes.
DT=0 + DT=1
DT=1
DT=0
(p,p’) … DT = 1 and DT = 0 (DTz = 0)
(3He,t) … DT = 1 only (DTz = -1)
(d,d’) … DT=0 only (DTz =0)
T. Kawabata et al., Phys. Rev. C 70, (2004).

4. Spin filtering for 16O
Spin-flip/non-flip exctitaion strengths in 16O are separated by measuring PT obs.
Polarization Transfer (PT) observables:
Total spin transfer:
T.Suzuki, Prog. Theor. Phys. 104, 859 (2000).
Spin-flip/non-flip cross sections:
sDS=1 = Ss, sDS=0 = (1-S)s
T. Kawabata et al., Phys. Rev. C 65, (2002).

5. Isospin/spin filtering with a Beam
Alpha inelastic scattering has a selectivity for the DS=0 and DT=0 excitation.
Nuclear incompressibility was determined via ISGMR and ISGDR measurement.
M. Itoh et al., Phys. Rev. C 68, (2003).

6. Future Prospective
Nuclear spectroscopy with spin/isospin filtering achieves successful results.
Natural extension for RCNP Upgrade Project
Similar technique should be applied to Hadron spectroscopy.
Important for better understanding of QCD in non-perturbative regime.
- Confining mechanism
- Chiral symmetry breaking
Extensive works were devoted to the hadron spectroscopy, especially with electromagnetic probes....
However ....
No spin/isospin filtering technique was fully applied.
Some excitation modes are weakly excited by the EM interaction.
Spectroscopic technique developed at RCNP might open a door.

7. Roper Resonance
Roper resonance N* (1440) has the same quantum numbers with the nucleon.
IS monopole (breathing-mode) resonance in nucleon.
- Compressibility of nucleon.
- Variation in Nuclear Medium.
N* (1440) is still poorly understood both theoretically and experimentally.
- Hardly excited by electromagnetic probes.
- Often buried in the neighboring resonances and continuum.
w (GeV)
D (1232)
1440
P. Stoler, Phys. Rev. Lett. 66, 1003 (1991).
(e,e’)
H. P. Morsch et al., Phys. Rev. C 71, (2005).
d2s/dtdW [mb/(GeV/c)2 GeV]
Missing Mass (GeV)

8. Structure of Roper Resonance
Structure of the Roper resonance is still controversial.
H. P. Morsch proposed two different resonances near N* (1440).
- Breathing mode.
- D excitation build on D (1232).
O. Krehl and E. Hernandez theoretically proposed the Roper excitation rests solely on meson-nucleon dynamics.
- No genuine three-quark resonance is needed to account pN phase shifts.

9. Roper Resonance in Nuclear Medium
Nucleon breathing mode might be modified in nuclear medium.
It is of interest to compare the nucleon breathing mode in free space with that in nuclear medium.
Free Space
Nuclear Medium
Partial restoration of chiral symmetry ??

10. Isospin Filtering for Roper Excitation
Isoscalar probes were extensively utilized to examine Roper resonance.
a particles have a selectivity for DT=0 and DS=0 transitions such as a Roper excitation.
Nucleon in alpha could be excited.
- Hardly excited by electromagnetic probes.
- Complementary information such as decay-particle distribution or spin observable is needed.
aD ?
Roper ?
H. P. Morsch et al., Phys. Rev. C 61, (1999).

11. Possible Strategies
Alpha/Deuteron inelastic scattering with beam energies of P ~ several GeV/c
Measurement:
Angular distribution to obtain transition density distribution.
Decaying pions to eliminate projectile excitation.
Spin observables to separate DS=0 excitation.
Spin-flip probability for deuteron:
Y.Satou et al., Phys. Lett. B 521, 153 (2001).
Spin-flip/non-flip cross sections:
sDS=1 = S1s, sDS=0 = (1-S1)s
Measurement below the threshold in NN system might be useful??

12. Summary
Nuclear Spectroscopy with the spin/isospin filtering techniques are successfully performed at RCNP.
Simple reaction mechanism at a few hundreds MeV/u.
Various probes with isospin selectivity.
Spin filtering by measuring spin observables.
Those sophisticated spectroscopic techniques should be applied to the hadron spectroscopy in the future facility.
As an example, a spectroscopic study of Roper resonance is proposed.
Nucleon breathing modes in nuclear medium might be interesting.