Coherent Λ-Σ Coupling in Neutron-rich Hypernuclei

Transcription

1 RIKEN Lecture January 6, 2006 Coherent - Coupling in Neutron-rich Hypernuclei Yoshinori AKAISHI

2 Exotics? The exotic nucleus, 11 Li

3 The overbinding problem H -0.1 MeV H He MeV MeV 5 He MeV MeV (Exp) -.12 MeV R.H. Dalitz, R.C. Herndon & Y.C. Tang, Nucl. Phys. B7 (1972) 109 Overbound

4 Singlet interaction is more attractive than triplet interaction.

5 Central YN interaction Pictures 1-channel 2-channel D0 D2 N Coupling N A.R. Bodmer (1966) Phase-equivalent to Nijmegen D 0 N phase shift S S (MeV)

6 Two pictures N int. D0 Overbinding problem N-N int. D2 Underbinding problem H He 5 He H He 5 He Underbinding? Exp -.12 MeV MeV Exp -.12? Overbinding N N N V N, N Q V e N, N Pauli suppression R.H. Dalitz et al. (1972)

7 Coherent - coupling T=0 T= MeV/c MeV/c 2

8 (MeV) 0 He D2 interaction 20 U ( 0 + ) 10 U ( 1 + ) U ( + 0 ) U ( + 1 ) MeV Exp r (fm) Y. Akaishi, T. Harada, S. Shinmura and Khin Swe Myint, Phys. Rev. Lett. 8 (2000) 59

9 = = = p n n s s s = = = n p p s s s H S=1 pairs Contribution to U - coupling energy 1 : 9 1/2 /2 +1/2 +1/2 +1/2 +1/2 +1/ -1/ Cancel Coherently added

10 The difference is not a measure of N spin-spin interaction. B. Gibson (Maui, 199) N N (MeV) He N N P coh =1.9 % 0 P coh =0.7 % + P coh =0.9 % P coh =2.0 % Exp D2 SC97e(S) SC97f(S) SC89(S) Th.A. Rijken Y. Akaishi, T. Harada, S. Shinmura & Khin Swe Myint, Phys. Rev. Lett. 8 (2000) 59

11 CRC

12 Faddeev-Yakubovsky calculation of He Real space SC97e 1 E E P V V V + V V V V + V A. Nogga, (2001) % 1.08% (MeV) V ( E) + V ( E) Model space N 2 N 1 ( E) ( E) V N + V N 2 Is the 1 S 0 YN int. more attractive than the S 1 YN int.? No! Is there any evidence for coherently enhanced - coupling in 0 +? No!

13 Single-channel description of He Model space SC97e (MeV) E V sc V, sc E V sc V, sc Coherently enhanced x/5 -.1 Cooking! 1 S 0 sc S 1 is more attractive than. sc V, V + V + sc = V P + V { T + P ΔM } { T } + 1 P = 1 1 P V

14 Stochastic variational calculation of 5 He H. Nemura, Y. Akaishi & Y. Suzuki, Phys. Rev. Lett. 89 (2002) 1250 The first successful ab initio 5-body calculation including degrees of freedom J.A. Carlson, AIP Conf. Proc. 22 (1991) 198 SC89: unbound H [0.15%] -0.1 H [0.98%] He SC97e(S) NN:GRS [1.9%] p [1.55%] -.12 (MeV)

15 Rearrangement of He due to sticking α -28 MeV - MeV -2 MeV -8 MeV Rearrangement in α M. Kohno et al., Phys. Rev. C68 (200) 002 H. Nemura et al., Phys. Rev. Lett. 89 (2002) 1250 N (D) N N P D (α)=10.2% 9.% 1 C V ( E) V ( T E) N V T π (S) N C V ( E) - MeV, MeV, V T π T = 85 MeV N

16 Repulsion? Attraction? Y. Nogami et al. Nucl. Phys. B19 (1970) 9 N N Y. Akaishi et al. Phys. Rev. Lett. 8 (2000) 59 H He 5 He H He 5 He Underbinding Exp MeV -.12 MeV -.12 An extraordinary state Overbinding

17 5 He Single channel n n n p p n n p p n 0 p n n Attractive n n p n p n p n p Repulsive Nogami s BF n p

18 He Single channel n p p n p p n p p 0 p n n Attractive n n p p p n p p 0 n p n p n p Attractive Akaishi s BF Repulsive Nogami s BF

19 Effects of NN three-body force 0.0 (MeV) He 5 He Exp Exp -.12 p p 0 Origin of overbinding Restoration of Pauli principle Coherent - coupling -5.9 Essential dynamics in T=0 nuclei

20 Three-body force due to coherent - coupling : [for D0] U α r r 1 r r r = W 1 2 α α 1 2 α 1 α= tt, ts, ss 2 ( r, r ) a + b ( σ σ ) + c σ ( σ + σ ) NN 2 NN spin-spin a a a tt ts ss W 7 b tt ctt bts cts = 8 8 b ss css t 1 t r, r ' ) = VN, N( r ) VN, ΔM * tt ( N ( r ' ) V t V t 5 He H(1+ ) H(0 + ) H 1 2 ( β ) W tt 2 + MeV 1 2 ( 9 + 2β + β ) W tt ( 6β + 5β ) W tt ( 1 6β + β ) W tt 8 s 5 t 1.0 MeV -0. MeV MeV VN, N = β VN, N, β = 0.67

21 Light hypernuclei A.R. Bodmer & Q.N. Usmani, Nucl. Phys. A77 (1988) 621 R. Sinha & Q.N. Usmani, Nucl. Phys. A68 (2001)586c V N 1 r r 2 = ( Vcore( r ) V )( 1 ε + εpx ) + VσσσN Tπ ( r ) Spin-spin DS r r r V NN = W0Tπ ( r i ) Tπ ( r j ) 1+ σ( σ i + σ j ) 6 Spin-spin H 5 He π N 2 N splitting MeV (70%) The major part is attributed to NN and not to N MeV Exp MeV -.0 MeV (62%) MeV for SC97f Variational Monte Carlo J. Lomnitz-Adler, V.R. Pandharipande & R.A. Smith, Nucl. Phys. A61 (1981) 99

22 The first observation of a bound state E167 : Phys. Lett. 21 (1989) 55 R.S. Hayano T. Ishikawa M. Iwasaki H. Outa E. Takada H. Tamura A. Sakaguchi M. Aoki T. Yamazaki

23 Nucleus, He T. Harada, S. Shinmura, Y.Akaishi & H. Tanaka, Nucl. Phys. A507 (1990) (MeV) U nucl r r = V + V T t 0 τ nucl Lane term 50 U =V 0 h 0 U t + h 0 T - t + t R (fm) U + = V 2 τ 0 h -t

24 Observation of a He bound state T. Nagae, R.E. Chrien et al., Phys. Rev. Lett. 80 (1998) 1605 He B + =. ± 0. ± 1MeV Γ = 7. 0 ± MeV.6 MeV 7.9 MeV T. Harada, Y.Akaishi et al., Nucl. Phys. A507 (1990) 715

25 Theory: T. Harada, Phys. Rev. Lett. 81 (1998) 5287

26 Neutron-excess hypernuclei p 1 V t 0 p 1 t ( V +V 12 s ) Proton induced Cancellation due to isospin selection n n Neutron induced 1 V t 1 12 t ( V +V s )

27 Incoherent + n p n p Coherent T T + 1 for T = T z = N coh =/ 0 n p n p n p

28 SC89 S. Shinmura et al.

29 Relativistic mean field model Baryons: n, p,, Mesons: σ, ρ, ω X X Coherent - mixing X Normal state of infinite matter Baryons in the medium carry the same quantum numbers in vacuum. N.K. Glendenning, Astrophys. J. 29 (1985) 70.

30 C58 AD1181

31 1 H ( 6 He, 2 He ) 5 H 1.7 (MeV) Superheavy hydrogen A.A. Korsheninnikov et al, Phys. Rev. Lett. 87 (2001) H H + + 2n 2n+ -. MeV -2.0 H + 2n MeV NN force 6 Li ( π -, K + ) 6 H Hyperheavy hydrogen Khin Swe Myint & Y. Akaishi, Prog. Theor. Phys. Suppl. 16 (2002) H 8 H H.I.

32 Double-charge & strangeness exchange reaction P.K. Saha, T. Fukuda 10 B ( π -,K + ) 10 Li = 6 H + α = H + 2n + α Stabilizer 11 B ( π -,K + ) 11 Li n 9 Li C. Kurokawa et al.

33 10 B(π -,K + ) spectrum J-PARC P.K. Saha, T. Fukuda et al., Phys. Rev. Lett. 9 (2005) P.K. Saha et al., KEK-PS-E521 collaboration Preliminary!! ~0 counts

34 10 Li D2 int NN force 0.21 MeV (P coh =0.1%) γ SVM cal. beyond -body model α + t + + n + n Coherent - coupling BHF cal. Y. A. & K.S. Myint

35 0 Y- [ NNN ] T=1/2 : interactions from D U ( 0 + ) Coherent - coupling 10 U ( + 1 ) 0 U ( 1 + ) 1 2 r (fm) 5-10 U ( + 0 ) -20 U ( + 1 ) -0 (MeV) + U ( 0 ) T = 1/ 2 H formation San Dar Myint Oo

36 Coupling scheme n - Coherent - coupling H formation α formation h n-n 0 -p - coupling n 0 p - n 0 p - t t n n Participant Spectator t α

37 Coupling scheme of t-t- - 0 H formation h t t t Coherent - coupling t t

38 7 He t + t + H + t [MeV] α + n + n + 5 He + n + n 6 He + n 6 He +

39 J-Lab O. Hashimoto et al. 7 He t + t + H + t [MeV] Feshbach resonance? 6 He +

40 Hyperon mixing in 5 H H. Nemura et al.

41 Fully coupled channel (-NΞ--) calculations H. Nemura, S. Shinmura, Y. Akaishi & K.S. Myint, Phys. Rev. Lett. 9 (2005) B -2 [MeV] H H H 5 He H - -6 Nagara -6 -B -8 6 He -8 [MeV]

42 6 Li (K -,K + ) 6 H 6 H = [ t---n ] [ t---n ] Alpha formation Coherent - coupling [ α-ξ - -n ] Large Ξ - mixing Nemura s mechanisn Missing-mass spectroscopy in S=-2 sector via one-step process!

43 Concluding remarks 5 The overbinding problem of He has been virtually solved. NN force Repulsive/attractive : D0 picture Attractive : D2 picture consistency A necessary condition for YN interaction to study A. Effective N interaction Coherent - coupling is essential dynamics. + + He(0 ) - He(0 coh (- 0 mixing) in dense neutron matter ) Neutron-rich hypernuclei can provide additional evidences for coherent - coupling. 6 Li ( π,k + ) 6 H H.I. 7 H, 8 H,, 5 H, 7 H, etc.

44 Excitation energy (MeV) A 1 Ξ 0 [ Z ] - 1 Ξ A [ Z + 1] A 2 [ Z ] + A 1 [ Z 1] A 1 0 [ Z ] - 1 A [ Z + 1] A 1 [ Z ] Coherent - mixing in neutron-rich medium. π - A [ Z + 1] ( K -,K + ) (K, π ),( π,k ) ( K -, π ),( π +,K + ) 0 S=-2 S=-1 A [ Z ] A A [ Z + 1] [ Z + 2 ] S=0 nuclei

45 Thank you very much!