Precision spectroscopy of deeply bound pionic states in tin isotopes at RIBF

Transcription

1 Precision spectroscopy of deeply bound pionic states in tin isotopes at RIBF DeukSoon Ahn, Georg P.A. Berg, Masanori Dozono, Daijiro Etoh, Hiroyuki Fujioka, Naoki Fukuda,! RILAC Nobuhisa Fukunishi, Hans Geissel, Emma Haettner, Tadashi Hashimoto, Ryugo S. Hayano, Satoru Hirenzaki, Hiroshi Horii, Natsumi Ikeno, Naoto Inabe, Kenta Itahashi*, Sathoshi Itoh, Masahiko Iwasaki, Daisuke Kameda, Shouichiro Kawase, Keichi Kisamori, Yu Kiyokawa, Toshiyuki Kubo, Kensuke AVF Kusaka, Hiroaki Matsubara, RIPS Masafumi Matsushita, Shin'ichiro Michimasa, Kenjiro Miki, Go Mishima, Hiroyuki Miya, Daichi Murai, Yohei Murakami, Hideko Nagahiro, Masaki Nakamura, Megumi Niikura, Takahiro Nishi**, Shumpei Noji, Kota Okochi, Shinsuke SRCOta, Naruhiko Sakamoto, Kimiko Sekiguchi, Hiroshi Suzuki, frcken Suzuki, Motonobu RRC Takaki, Hiroyuki Takeda, Yoshiki K. Tanaka, Koichi Todoroki, Kyo BigRIPS Tsukada, Tomohiro Uesaka, Yasumori Wada, Yuni N. Watanabe, Helmut Weick, Hiroyuki Yamada, Hiroki Yamakami, Yoshiyuki Yanagisawa and Koichi Yoshida! 0 50 m Takahiro Nishi! Advanced Meson Science Laboratory, RIKEN IRC *spokesperson, ** co-spokesperson University of Tokyo, RIKEN, Nishina Center, University of Notre Dame, Tohoku University, Kyoto University, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Nara Women's University, Osaka University,! Stefan Meyer Institute

2 2 Deeply bound pionic states Half density radius Nucleus pion orbit : surface on the nuclei 1s pion density deeply bound pionic states! Large overlap between π and A good probe for strong interaction at finite ρ π ~ probing 0.6 ρ0 1s 2s Nuclear density overlap 2s radius [fm] N. Ikeno et al., PTP126(2011)483.

3 3 Strong interaction and pionic states 121 Sn-π - BE, Γ of 1s pionic state% strong interaction effect π-a s-wave optical potential (s-wave) V s (r) = 2 µ [ 1{b 0 + b 1 } + 2 B 0 2 ] ρ = ρp + ρn! δρ = ρp ρn N. Ikeno et al., Prog. Theor. Phys. 126 (2011) 483.! S. Itoh, Doctoral Dissertation, Univ. of Tokyo (2011)

4 4 Strong interaction and pionic states BE, Γ of 1s pionic state% strong interaction effect 121 Sn-π - π-a s-wave optical potential (s-wave) V s (r) = 2 µ [ 1{b 0 + b 1 } + 2 B 0 2 ] strong relation with quark condensate Order parameter of % chiral symmetry breaking N. Ikeno et al., Prog. Theor. Phys. 126 (2011) 483.! S. Itoh, Doctoral Dissertation, Univ. of Tokyo (2011)

5 5 Production method; (d, 3 He) reaction d p n n A Pb A Pb(d, 3 He) π- p p n 3 He neutron! hole A-1 Pb π- Momentum transfer [MeV/c] recoilless condition is = 250 MeV/u BEπ ~ 0 MeV! BEπ ~ 5 MeV Pion bound state! (coupled with n hole) threshold quasifree Incident energy [MeV/u] 3 He kinetic energy

6 6 Deeply bound pionic atoms at GSI Calibration Nuclear chart 123 Sn 1s 119 Sn 115 Sn K. Suzuki et al., PRL (2004) NuDat Systematic study of pionic Sn isotopes ~ 3 month measurement for 3 isotopes

7 7 Extract b1 from experimental data Contour plot of χ 2 π-a s-wave optical potential b 1 free / b Pb ,119,115 Sn, 28 Si, 20 Ne, 16 O 1.0 free value V s (r) = 2 µ [ 1{b 0 + b 1 } + 2 B 0 2 ] ImB0 [mπ -4 ] σ 3σ 2σ 1σ b free 1 b 1 =0.78 ± b 1 [m π -1 ] qq qq cf. theoretical prediction ~ ± 0.06 b0, ReB0 are deduced from data of light / symmetric pionic atoms

8 8 Extract b1 from experimental data Contour plot of χ 2 π-a s-wave optical potential b 1 free / b Pb ,119,115 Sn, 28 Si, 20 Ne, 16 O 1.0 free value V s (r) = 2 µ [ 1{b 0 + b 1 } + 2 B 0 2 ] ImB0 [mπ -4 ] σ 3σ 2σ b free 1 b 1 =0.78 ± σ b 1 [m π -1 ] qq qq 0.66 ± 0.06 error of b1 in medium is still large! compared with that in vacuum!!! two main sources are!! experimental error % neutron distribution ambiguities cf. theoretical prediction ~ 0.65 b0, ReB0 are deduced from data of light / symmetric pionic atoms

9 9 Extract b1 from experimental data Contour plot of χ 2 π-a s-wave optical potential b 1 free / b Pb ,119,115 Sn, 28 Si, 20 Ne, 16 O 1.0 free value V s (r) = 2 µ [ 1{b 0 + b 1 } + 2 B 0 2 ] ImB0 [mπ -4 ] b free σ 3σ 2σ 1σ b 1 [m π -1 ] To extract qq =0.78 ± b1 with higher precision% ± 0.06 b 1 qq cf. theoretical prediction ~ 0.65 error of b1 in medium is still large! compared with that in vacuum!!! two main sources are!! experimental error % neutron distribution ambiguities improve resolution / calibration! More isotopes

10 10 Experiment at RIBF, RIKEN RILAC RIPS AVF frc RRC SRC BigRIPS IRC 0 50 m GSI RIBF Improvement intensity ~ / 6 s (1 spill) ~ / s 60 angular acceptance (H / V) 15 / 10 mrad 40 / 60 mrad 16 resolution (FWHM) 400 kev improve

11 First production experiment in 2014! RIKEN (11 days) aim of the experiment% improve the resolution ~ 300 kev first step of the systematic study with enough statistics

12 First production experiment in 2014! RIKEN (11 days) NuDat Nuclear chart Measured targets in exp. at GSI! Measured targets in exp at RIKEN 122 Sn: relatively large cross section! 117 Sn: first odd-a target

13 13 RIKEN Fragment Separator BigRIPS Experimental setup 3 He ~ 10 2 Hz% (signal) Detector Installation p ~ 10 5 Hz! (break up/ background) F7 F5 Target (strip) F0 SRC Beam Transfer line Superconducting! Ring! Cyclotron d beam 250 MeV/u! ~ /s

14 14 Experimental setup: detectors Tracking by MWDC 3 He ~ 10 2 Hz% (signal) Detector Installation p ~ 10 5 Hz! (break up/ background) F7 F5 Measured position, angle@f5! +! transfer matrix SRC Target (strip) F0 P3He + reaction angle at target Multi Wire Drift Chamber

15 15 Production run: 122 Sn target position spectrum of 3 He counts / mm # of 3 He: ~ ! ~ 1 day measurement position of He at F5 focal plane [mm] High P3He

16 16 Production run: 122 Sn target position spectrum of 3 He Eex spectrum of 121 Sn bound state! of π in 121 Sn θreac < 1.0 counts / mm # of 3 He: ~ ! ~ 1 day measurement Preliminary position of He at F5 focal plane [mm] High P3He High P3He quasi-free π - production threshold The spectrum seems to achieve the best resolution among the past deeply-bound pionic atom experiment.

17 17 Fitting of the Eex spectrum : 122 Sn target 121 Sn s s s p p θreac < 1.0 Preliminary blue solid line : fit function fit region The Eex spectrum is fit by the function with several components! deduce binding energies and widths of pionic states calibration of Eex is still on going

18 18 Fitting of the Eex spectrum : 122 Sn target θreac < s 121 Sn! background (solid line / flat)! + 1s pionic state (dashed line) 3s1/2, 2d3/2, 1h11/2 1g7/2, 2d5/2(i), (ii) each pionic state! several configuration! with different neutron holes each configuration! Voigtian / σexp is fixed neutron hole Eex [MeV] 2d3/2 1h11/2 3s1/2 1g7/2 2d5/2 (i) 2d5/2 (ii) relative strength! for pionic 1s state

19 19 Fitting of the Eex spectrum : 122 Sn target θreac < s p 121 Sn! background (solid line / flat)! + 1s pionic state (dashed line)! + 2p pionic state (dashed line)

20 20 Fitting of the Eex spectrum : 122 Sn target θreac < Sn s s p! background (solid line / flat)! + 1s pionic state (dashed line)! + 2p pionic state (dashed line)! + 2s pionic state (dashed line)

21 21 Fitting of the Eex spectrum : 122 Sn target θreac < Sn s s s p p! background (solid line / flat)! + 1s pionic state (dashed line)! + 2p pionic state (dashed line)! + 2s pionic state (dashed line)! + 3p, 3s state (dashed line)! Fitting parameter! relative strength of each state! BE1s, BE2p, BE2s! Fixed parameter! BE3p, BE3s! Γ2s, Γ3p, Γ3s Γ1s, Γ2p

22 22 Fitting of the Eex spectrum : 122 Sn target θreac < Sn s s s p p Preliminary fit region Deduced BE1s, Γ1s, BE2p b1, ImB0 in π-a s-wave optical potential V s (r) = 2 µ [ 1{b 0 (r)+b 1 (r)} + 2 B 0 (r) 2 }]. b0, ReB0 are deduced from data of light / symmetric pionic atoms

23 23 Fitting of the Eex spectrum : 122 Sn target θreac < Sn s s s p p Preliminary fit region Deduced BE1s, Γ1s, BE2p b1, ImB0 in π-a s-wave optical potential V s (r) = 2 µ [ 1{b 0 (r)+b 1 (r)} + 2 B 0 (r) 2 }]. b0, ReB0 are deduced from data of light / symmetric pionic atoms

24 24 Fitting of the Eex spectrum : 117 Sn target θreac < Sn s s s p p Preliminary fit region Deduced BE1s, Γ1s, BE2p b1, ImB0 in π-a s-wave optical potential V s (r) = 2 µ [ 1{b 0 (r)+b 1 (r)} + 2 B 0 (r) 2 }]. b0, ReB0 are deduced from data of light / symmetric pionic atoms

25 θreac dependence of each components! 25 (pionic states in 121 Sn) Sn - 1s state - 2p state - 2s state Preliminary Preliminary s state! decrease dσ/dω p state! increase dσ/dω Large θreac! large momentum transfer! large angular momentum transfer! finite n state increase (2p)

26 θreac dependence of each components! 26 (pionic states in 116 Sn) Sn - 1s state - 2p state - 2s state Preliminary Preliminary s state! decrease dσ/dω p state! increase dσ/dω Large θreac! large momentum transfer! large angular momentum transfer! finite n state increase (2p)

27 θreac dependence of each components! 27 (pionic states in 116 Sn) Sn - 1s state - 2p state - 2s state Preliminary Preliminary s state! decrease dσ/dω p state! increase dσ/dω Large angular acceptance of the spectrometer@riken! enables us to observe angular dependence of d 2 σ/dedω Large θreac! large momentum transfer! large angular momentum transfer! finite n state increase (2p)

28 28 Summary Deeply-bound pionic atom is good probe for QCD in finite density, especially for quark condensate via b1 parameter in π - A potential. To determine the b1 precisely, experiments of pionic Sn isotopes are on going at RIKEN. In the first exp., we measured with the target of 122,116 Sn, and succeed in - improvement of the resolution, - observation of the pionic 1s, 2p and 2s states in 121, 116 Sn, - observation of angular dependence of these states. Analysis to deduce b1 from measured BE1s, Γ1s, BE2p is in progress.

29 29 (Near) future works NuDat Nuclear chart Measured targets in exp. at GSI! Measured targets in exp at RIKEN! Target candidates of the next exp. The next exp. are already approved in PAC at RIKEN! with wider range of isotopes.! The exp. will be performed in a few years.