Hypernuclei: latest results from LNF and future programs at J-PARC

Transcription

1 Hypernuclei: latest results from LNF and future programs at J-PARC n p p n p p n Λ p n n p p Λ n n Λ p Alessandro Feliciello I.N.F.N. - Sezione di Torino

2 Outline 3 The FINUDA experiment at DAФNE hypernuclear physics results: 6 H neutron-rich hypernucleus 2 N induced hypernucleus weak decay Looking to the future: the INFN ULYSSES J-PARC

3 DAΦNE May

4 DAΦNE 5 e Κ e stop Κ A Z A Z Κ OSIM energy 510 MeV luminosity cm -2 s -1 σ x (rms) 2.11 mm σ y (rms) mm σ z (rms) 35 mm bunch length 30 mm Be window beam pipe A ( Z 1) targets ISIM tofino crossing angle 12.5 mrad frequency (max) MHz bunch/ring up to 120 part./bunch current/ring 5.2 A (max) A Z ( A2) ( A3) ( Z ( Z 1) 1) p n p n n

5 FINUDA key features 6 very thin nuclear targets ( g/cm 2 ) high resolution spectroscopy coincidence measurement with large acceptance decay mode study event by event K + tagging continuous energy and rate calibration irradiation of different targets in the same run systematic error reduction

6 The FINUDA Collaboration 7 I.N.F.N. Bari and Bari University Brescia University KEK I.N.F.N. / L.N.F. Frascati I.N.F.N. Pavia and Pavia University RIKEN Seoul National University Teheran Shahid Beheshty University I.N.F.N. Torino and Torino University Torino Polytechnic I.N.F.N. Trieste and Trieste University TRIUMF

7 Physics output (S = -1) 9 M. Agnello et al., PLB 640 (2006) 145 M. Agnello et al., PRL 108 (2012) M. Agnello et al., NPA 881 (2012) 269 M. Agnello et al., PRC 86 (2012) nuclear models M. Agnello et al., PLB 622 (2005) 35 M. Agnello et al., PLB 681 (2009) 139 M. Agnello et al., NPA 835 (2010) 414 M. Agnello et al., PLB 698 (2011) 219 spectroscopy neutron-rich Λ-hypernuclei medium effect n p p n n p p n Λ p p n 4B weak interaction (weak) decay quark substructures low-energy N -Y interaction deeply bound K states M. Agnello et al., PRL 94 (2005) M. Agnello et al., NPA 804 (2008) 151 M. Agnello et al., PLB 681 (2009) 139 M. Agnello et al., NPA 835 (2010) 439 M. Agnello et al., PLB 685 (2010) 247 M. Agnello et al., PLB 701 (2011) 556 M. Agnello et al., NPA 881 (2012) 322

8 The new NRH search strategy 12 L int 1156 pb -1 K 6 6 stop Li 6 H H 6 He double C-EX p ~ 252 MeV/c n.m. decay p ~ 134 MeV/c apparatus capabilities: selective trigger (based on fast scintillator detectors) precise K - vertex identification < 1 mm 3 (PID + spatial resolution + K - tagging), K, p, d, separation (OSIM & LMDC de/dx) high momentum resolution MeV/c 6% 110 MeV/c (tracker performance + He bag + thin target)

9 Analysis technique 13 K 6 6 stop Li 6 H H 6 He 6 ( ( He) 801 ms) if 6 H is a stable system 2 independent two-body reactions: decay at rest atomic mass tables M 2 ( 6 He) p 2 ( ) M( 6 He) M M ( 2 6 ( 6 H ) p 2 ( ) M ( 6 H ) 5 H ) M ( H ) M ( ) B( ) MeV ( MeV with B 0 6 MeV) cut on T ( ) T ( ) : MeV

10 Data selection MeV/c ( p =1.1 MeV/c) MeV/c ( p =1.2 MeV/c) 5 H + 3 H + 2n MeV -1.7 MeV selection range fixed by including 6 H lowest particle stability threshold p + = MeV/c p - = MeV/c B = MeV (out of stopped K - events) 4 H + 2n MeV

11 Production rate 17 background sources accidentals: + ( MeV/c) and - ( MeV/c) 0.27 ± 0.27 ev. - He n n K stop Li end point ~190 MeV/c end point ~282 MeV/c 0.16 ± 0.07 ev. K 6 4 stop Li production rate H n n + 4 He + - total background on 6 Li: end point ~252 MeV/c p( - ) = 133 MeV/c BGD1 + BGD2 = 0.43 ± 0.28 ev. negligible Poisson statistics: 3 events DO NOT belong to pure C.L. = 99% BR( ) 4 H 0.49 R BR( ) (3 BGD1 BGD2) /[ ( ) ( )( n. 6 R BR( ) ( ) 10 / K stop K stop on 6 Li)] H. Tamura et al., PRC 40 (1989) R479 6 R ( ) 10 / K stop FINUDA Coll. and A. Gal, PRL 108 (2012) ( ) 10 5 / K stop M. Agnello et al., PLB 640 (2006) 145

12 Kinematics and binding energy ( N Y ) / Z( H ) 5 N / Z( He) 3 theoretical predictions B = 4.2 MeV R.H. Dalitz and R. Levi Setti, NC 30 (1963) 489 B = 4.2 MeV L. Majling, NPA 585 (1995) 211c formation mass values systematically higher than the ones from decay Akaishi M = ( ± 1.1) MeV (0.98 ± 0.74) MeV excited states production MeV MeV B = (4.0 ± 1.1) MeV ( 5 H + ) nrh prod. rate: ~10-2 hyp. prod. rate in (K - stop, - ) B = 5.8 MeV ( 5 H + ) NN force 1.4 MeV FINUDA Coll. and A. Gal, PRL 108 (2012) FINUDA Coll. and A. Gal., NPA 881 (2012) 269

13 Physics output (S = -1) 23 M. Agnello et al., PLB 640 (2006) 145 M. Agnello et al., PRL 108 (2012) M. Agnello et al., NPA 881 (2012) 269 M. Agnello et al., PRC 86 (2012) nuclear models M. Agnello et al., PLB 622 (2005) 35 M. Agnello et al., PLB 681 (2009) 139 M. Agnello et al., NPA 835 (2010) 414 M. Agnello et al., PLB 698 (2011) 219 spectroscopy neutron-rich Λ-hypernuclei medium effect n p p n n p p n Λ p p n 4B weak interaction (weak) decay quark substructures low-energy N -Y interaction deeply bound K states M. Agnello et al., PRL 94 (2005) M. Agnello et al., NPA 804 (2008) 151 M. Agnello et al., PLB 681 (2009) 139 M. Agnello et al., NPA 835 (2010) 439 M. Agnello et al., PLB 685 (2010) 247 M. Agnello et al., PLB 701 (2011) 556 M. Agnello et al., NPA 881 (2012) 322

14 2N induced weak decay 25 relevance first pointed out by: W.M. Alberico et al., PLB 256 (1991) 134 key role in data interpretation many theoretical predictions E. Bauer G. Garbarino A. Parreño A. Ramos importance of the effect: ~20-25% of the total NMWD width several experimental evidences, but indirect E. Botta, T. Bressani, G. Garbarino, EPJA 48 (2012) 21 smoking gun evidence missing! experimental hardness: 3 nucleons emitted from -hypernucleus g.s. 4-fold coincidence measurement ( -, p, n, n)

15 2N induced decay exp. evidence 26 triple coincidence: (n + n + p) events exclusive np nnp decay event: 7 Li 4 He p n n p - = ± 1.2 MeV/c p miss = 217 ± 44 MeV/c E tot = 178 ± 23 MeV MM = 3710 ± 23 MeV/c 2 E(n1) = 110 ± 23 MeV E(n2) = 16.9 ± 1.7 MeV E(p) = ± 0.85 MeV (n1 n2) = 94.8 ±3.8 (n1 p) = ±3.4 (n2 p) = 154 ±19 no n-n or p/n scattering first, direct experimental evidence M. Agnello et al., NPA 881 (2012) 322

16 2N induced decay exp. evidence 27 triple coincidence: (n + n + p) events exclusive np nnp decay event: 7 Li 4 He p n n p - = ± 1.2 MeV/c P miss = 447 ± 18 MeV/c E tot = ± 4.2 MeV MM = ± 4.7 MeV/c 2 E(n1) = 21 ± 2.0 MeV E(n2) = 35.3 ± 3.6 MeV E(p) = ± 0.50 MeV (n1 n2) = ±5.4 (n1 p) = 53.5 ±4.3 (n2 p) = ±3.9 no n-n or p/n scattering

17 2N induced decay exp. evidence 28 triple coincidence: (n + n + p) events exclusive np nnp decay event: 9 Be 3 He 3 H p n n p - = ± 1.2 MeV/c P miss = 253 ± 18 MeV/c E tot = ± 4.9 MeV MM = ± 5.0 MeV/c 2 E(n1) = 20.2 ± 2.5 MeV E(n2) = 31.5 ± 4.2 MeV E(p) = ± 0.80 MeV (n1 n2) = ± 7.5 (n1 p) = ± 5.5 (n2 p) = 95.4 ± 3.6 no n-n or p/n scattering

18 Background evaluation 29 K ( np) p n 7 Li - p - n Target ( p) E p (MeV) 7 Li 33.4 ± ± Li ± ± Be ± ± 0.80 significant back-to-back correlation this feature rules out completely the first event on 7 Li the correlation between cos( - p)and E p was studied for the simulated background: major contribution from this source when and p are emitted nearly back-to-back and E p 100 MeV evaluation of the number of simulated events surviving to a 3σ cut on cos( - p) and E p on 7 Li and 9 Be: ~10-3 events were found for both targets the 2 Λnp nnp real events DO NOT belong to background to a confidence level 99%.

19 J-PARC SKS spectrometer K1.8 line K K, 33

20 J-PARC scientific program 22 experiments 7 proposals 4 tests 36

21 Physics output (S = -1) 37 E10 E13 nuclear models spectroscopy low-energy N -Y interaction neutron-rich Λ-hypernuclei medium effect n p p n n p p n Λ p p n deeply bound K states 4B weak interaction (weak) decay quark substructures E18 E22 E15 E27

22 E13 experiment layout -ray spectroscopy of hypernuclei top view 38 further study of ΛN interaction: 4 He Λ, 10 B Λ, 11 B Λ, 19 F Λ ΛN-ΣN coupling and 3-body force charge symmetry breaking (Λn Λp?) radial dependence (interaction range) g Λ in a nucleus from spin-flip B(M1): 7 Li Λ SksMinus + HyperBall side view K1.8 beam line Hyperball J-PARC

23 Physics output (S = -2) 41 nuclear models strangelets H dibaryon existence E03 E05 E07 spectroscopy low-energy Y-Y interaction p Λ n n Λ p double deeply bound K states (weak) decay S=-2 system g.s. H particle mass E42

24 E05 experiment layout 42 Spectroscopic study of -hypernucleus, 12 Be, via the 12 C(K -,K + ) reaction first spectroscopic study of S = -2 systems in (K -,K + ) reaction ΞN interaction attractive or repulsive depth of Ξ-nuclear potential isospin dependence ΞN-ΛΛ coupling force SksPlus

25 Summary 44 Last but not least results from FINUDA: first experimental evidence for the heavy hyperhydrogen 6 H Λ first direct observation of 2 N induced hypernucleus weak decay FINUDA could be considered an ideal bridge between the KEK and the J-PARC eras: we are now looking forward for new and exciting world class results

26 45 Thank you! 有り難う