Study of precursor phenomena of pionic condensation via parity conversion nuclear reaction on 40Ca Masaki Sasano Pion condensation Phase transition above n~2n0 A. B. Migdal, Zh. Eksp. Teor. Fiz. 61 (1971) 2210 Physics of nuclear matter Equation of state Exotic structure (ex. Alternating layer spin, T. Takatsuka et al., Prog. Theo. Phys. 59 (1978) 1933. Astrophysics Pion condensation in neutron star ⇒　stronger neutrion emission ⇒　resolve the probem of surface temprature of neutron star At n~n0, Precursor phenomena : pionic enhancement ⇒　Jπ=0－, T=1 (same as π)

Measurements of 0- in 40Ca by Parity conversion nuclear reaction 18O; 0+; g.s.→0－; 6.9 MeV 16O; 0+; g.s.→0－; 11.0 MeV Experimental method 16,18O @ 300MeV/n (primary beam, 100 pnA) SHARAQ, DALI2 target DALI2 γ NaI SHARAQ

パリティ反転核反応プローブ パリティ反転プローブ 従来の核反応プローブ: (p,p’)反応 Jt ＝ΔL±1, ΔL Parity: (－)ΔL Lt＝ΔL Jt ＝ΔL Parity: (－)ΔL+1 Lt＝ΔL+1 0+, 1+ (ΔL=0） 0－ (ΔL=0） 0－ ΔL ΔL 0+ 0+ 0+ Jp=1/2 プローブ粒子 プローブ粒子 標的粒子 標的粒子 　プローブ粒子の内部構造を無視 　プローブ側が励起しない 　プローブ粒子が複合核　 　プローブ側が励起：パリティのみ変化

16,18O核によるパリティ反転核反応 18O (T=1) 16O (T=0) Isoscalar channel (T=0) Isovector channel (T=1) Isoscalar channel (T=0) 18O (T=1) 16O (T=0) 6.9 MeV；0－ 11.0 MeV；0－ ガンマ線脱励起 2.4 MeV⇒検出 ガンマ線脱励起 3.8 MeV⇒検出 4.5 MeV；1－ 7.2 MeV；1－ 一段階非弾性散乱 0+; g.s. →0-; 6.9 MeV 一段階非弾性散乱 0+; g.s. →0-; 11.0 MeV g.s. 0+ g.s. 0+ Isovector channel は実際には純粋なT=1ではなく、isoscalar 成分（T=0)も 少量ながら混ざっている。両チャンネルを測定することで純粋なisovector成分を導出。

パリティ反転核反応のスペクトル 散乱角度分布 (p,p’) : 0－, 1－, 2－ 状態が混じる 従来のプローブ 　　　　　⇒　角度による分離が不可能 パリティ反転核反応： 0－のみ0度ピーク 　　　　　⇒　分離が容易 　　　　　⇒　標的：2重閉殻核(16O, 40Ca) 　　　　　　　 1+状態の0度への染み出し 　　　　　　　 を完全に除去可能。 従来のプローブ 0度 16O標的 パリティ反転核反応

最適入射エネルギーの選択 1. 多段階過程の効果を最小化 2. Isovector /Isoscalar (spin flip) を最大化 核子当たりの入射エネルギー300MeV

実験手法 統計量100events/day 16O(0－,T=1, 12.8MeV)、分解能 ~0.6MeV ビーム(16O,18O) 入射エネルギー: 300A MeV カレント: 10 pnA 分散整合 標的: 40Ca: 10mg/cm2 磁気分析器: Spectroscopy with High-resolution Analyzer and RadioActive Quantum beams (SHARAQ) 4. ガンマ線検出器系: NaI検出器アレイ DALI2 　　　検出効率1%、 エネルギー分解能400 keV 標的 γ NaI SHARAQ 統計量100events/day 16O(0－,T=1, 12.8MeV)、分解能 ~0.6MeV

パリティ反転核反応のスペクトル 散乱角度分布 (p,p’) : 0－, 1－, 2－ 状態が混じる 従来のプローブ 　　　　　⇒　角度による分離が不可能 パリティ反転核反応： 0－のみ0度ピーク 　　　　　⇒　分離が容易 従来のプローブ パリティ反転核反応

Parity-conversion reaction Existing nuclear probe: ex. (p,p’) Parity-conversion reaction Jt ＝ΔL±1, ΔL Parity: (－)ΔL Lt＝ΔL Jt ＝ΔL Parity: (－)ΔL+1 Lt＝ΔL+1 0+, 1+ (ΔL=0） 0－ (ΔL=0） 0－ ΔL ΔL 0+ 0+ 0+ Jp=1/2 probe probe target target 　no (negligible) internal structure of probe particle 　Probe particle is not excited 　Probe has internal structures　 　Probe can be excited (parity conversion)

Precursor phenomena of pion condensation Pionic enhancement Jπ=0－, T=1 (isovector) state, which has the same J, T, parity as pion, is enhanced Existing study：　 16O(p,p’)16O(0-,T=1,12.8 MeV) ⇒　support precursor phenomena Limited to known low-lying discrete states How about continuum? T. Wakasa et al., PLB 632, 485 (2006).

18O parity conversion reaction Isovector channel (T=1) 18O (T=1) 6.9 MeV；0－ Gamma ray 2.4 MeV⇒NaI 4.5 MeV；1－ One-step process 0+; g.s. →0-; 6.9 MeV g.s. 0+

Expected spectra for parity-conversion reaction Angular distribution (p,p’) : 0－, 1－, 2－ are mixed Parity-conversion： only 0- has peak at 0 degrees 　　　　　⇒　can be easily separated 　　　　　⇒ target：double closed nuclei (16O, 40Ca) 　　　　　 1+ states are strongly suppressed. 0度 16O標的

Plan of Exp. statistics100events/day 16O(0－,T=1, 12.8MeV)、res. ~0.6MeV Beam (18O) energy: 300A MeV current: 10 pnA Dispersion matching Target : 16O, 40Ca: 10mg/cm2 Spectrometer: Spectroscopy with High-resolution Analyzer and RadioActive Quantum beams (SHARAQ) 4. Gamma-ray dector: NaI detection array DALI2 　　　eff. 1%、 resolution ~400 keV 標的 γ NaI SHARAQ statistics100events/day 16O(0－,T=1, 12.8MeV)、res. ~0.6MeV

Summary Charge exchange reactions at intermediate energies are a useful probe of spin-isospin responses. The (p,n) reaction at 300 MeV is simplest probe for the GT transition. The GT unit cross sections has been successfully determined at 200 & 300 MeV. It is shown by using SM calc. & DWIA calc. that the GT unit cross section works well. B(GT) distrib. Have been deduced for double beta decay nuclei using the above obtained GT unit cross sections.

Parity-conversion reaction Jt ＝ΔL Parity: (－)ΔL+1 Lt＝ΔL+1 0－ (ΔL=0） 0－ ΔL 0+ 0+ probe target 　Probe has internal structures　 　Probe can be excited (parity conversion)

Precursor phenomena of pion condensation Pionic enhancement Jπ=0－, T=1 (isovector) state, which has the same J, T, parity as pion, is enhanced Existing study：　 16O(p,p’)16O(0-,T=1,12.8 MeV) ⇒　support precursor phenomena Limited to known low-lying discrete states How about continuum? T. Wakasa et al., PLB 632, 485 (2006).

18O parity conversion reaction Isovector channel (T=1) 18O (T=1) 6.9 MeV；0－ Gamma ray 2.4 MeV⇒NaI 4.5 MeV；1－ One-step process 0+; g.s. →0-; 6.9 MeV g.s. 0+

Expected spectra for parity-conversion reaction Angular distribution (p,p’) : 0－, 1－, 2－ are mixed Parity-conversion： only 0- has peak at 0 degrees 　　　　　⇒　can be easily separated 　　　　　⇒ target：double closed nuclei (16O, 40Ca) 　　　　　 1+ states are strongly suppressed. 0度 16O標的

Plan of Exp. statistics100events/day 16O(0－,T=1, 12.8MeV)、res. ~0.6MeV Beam (18O) energy: 300A MeV current: 10 pnA Dispersion matching Target : 16O, 40Ca: 10mg/cm2 Spectrometer: Spectroscopy with High-resolution Analyzer and RadioActive Quantum beams (SHARAQ) 4. Gamma-ray dector: NaI detection array DALI2 　　　eff. 1%、 resolution ~400 keV 標的 γ NaI SHARAQ statistics100events/day 16O(0－,T=1, 12.8MeV)、res. ~0.6MeV

Summary Charge exchange reactions at intermediate energies are a useful probe of spin-isospin responses. The (p,n) reaction at 300 MeV is simplest probe for the GT transition. The GT unit cross sections has been successfully determined at 200 & 300 MeV. It is shown by using SM calc. & DWIA calc. that the GT unit cross section works well. B(GT) distrib. Have been deduced for double beta decay nuclei using the above obtained GT unit cross sections.