NUFRA2013. Λ-hypernucleus decay: a discovery tool. Alessandro Feliciello I.N.F.N. - Sezione di Torino

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1 Λ-hyernucleus decay: a discovery tool NUFRA Setember - 6 October, 2013, Kemer (Antalya), Turkey Alessandro Feliciello I.N.F.N. - Sezione di Torino

2 Outline hysics motivations a osteriori (discovery tool) intrinsic exerimental results: mesonic decay (exclusive) non-mesonic decay 2N induced decay a look to the (next) future: waiting for J-PARC waiting for J-Lab waiting for MAMI 2 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

3 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 The original NRH search strategy L int 1156 b -1 K 6 6 sto Li 6 H H 6 He double C-EX ~ 252 MeV/c n.m. decay ~ 134 MeV/c aaratus caabilities: selective trigger (based on fast scintillator detectors) recise K - vertex identification < 1 mm 3 (PID + satial resolution + K - tagging), K,, d, searation (OSIM & LMDC de/dx) high momentum resolution MeV/c 6% 110 MeV/c (tracker erformance + He bag + thin target) 3

4 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 background sources 6 H Λ roduction rate accidentals: + ( MeV/c) and - ( MeV/c) 0.27 ± 0.27 ev. - He n n K sto Li K 6 4 sto Li roduction rate H n n + 4 He + - total background on 6 Li: end oint ~190 MeV/c end oint ~282 MeV/c end oint ~252 MeV/c ( - ) = 133 MeV/c BGD1 + BGD2 = 0.43 ± 0.28 ev ± 0.07 ev. negligible Poisson statistics: 3 events DO NOT belong to ure C.L. = 99% BR( ) 4 H 0.49 H. Tamura et al., PRC 40 (1989) R479 R BR( ) (3 BGD1 BGD2) /[ ( ) ( )( n. 6 R BR( ) ( ) 10 / 6 R ( ) 10 / K sto FINUDA Coll. and A. Gal, PRL 108 (2012) K sto ( K ) 10 sto 5 on / K 6 sto Li)] M. Agnello et al., PLB 640 (2006) 145 4

5 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 Kinematics and binding energy 6 8 ( N Y ) / Z( H ) 5 N / Z( He) 3 theoretical redictions 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 nrh rod. rate: ~10-2 hy. rod. rate in (K - sto, - ) formation mass values systematically higher than the ones from decay Akaishi M = ( ± 1.1) MeV B = (4.0 ± 1.1) MeV ( 5 H + ) B = 5.8 MeV ( 5 H + ) NN force 1.4 MeV (0.98 ± 0.74) MeV excited states roduction E. Hiyama et al., NPA 908 (2013) 29 A. Gal, D.J. Millener, PLB 725 (2013) MeV MeV FINUDA Coll. and A. Gal, PRL 108 (2012) FINUDA Coll. and A. Gal, NPA 881 (2012) 269 5

6 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA N Λ J assignment background free M. Agnello et al., PLB 681 (2009) O: 1/2 - g.s. & sd (~6 MeV) limited energy resolution A. Gal, NPA 828 (2009) 72. Clear corresondence with the calculated strength functions: T. Motoba et al., Nucl. Phys. A 489 (1988) 683. A. Gal, Nucl. Phys. A 828 (2009) N Λ g.s sin not known J π ( 15 N Λ g.s. ) = 3/2 + D.J. Millener, A. Gal, C.B. Dover, Phys. Rev. C 31 (1985) 499. Sin ordering not obtained from -rays of 16 O Λ M. Ukai et al., Phys. Rev. C 77 (2008) First exerimental determination of J π ( 15 N Λ g.s. ) = 3/2 + from decay rate value (and sectrum shae) T. Motoba, NPA 489 (1988) st exerimental determination 6

7 Exanding the horizon H. Tamura 4 He udated from B.I. Abelev et al., Science 328 (2010) A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

8 STAR 3 H Λ signal 8 Au Au@ 200 GeV 3 H 3 He 3 H 3 He B.I. Abelev et al., Science 328 (2010) 58. A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

9 NUFRA2013 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 Hyernuclei in HI collisions Pb S NN 2.76 TeV 3 3 H 3 He 3 H He toological cuts cos(ointing angle) > 0.9 DCA track to PV > 0.4 cm DCA between tracks < 0.7 cm T(3He, ) > 1 GeV/c c > 1 cm R. Lea, NPA 914 (2013)

10 13 How to identify a ΛΛ-hyernucleus sequential ionic decay A A' ΛΛ Z Λ Z' A" Λ Z" limited target choice (at least for the ilot runs) main background 6 Li, 7 Li, 8 Be, 9 Be, 12 C critical! A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

11 Two different stories n(udd) I(J P ) = ½(½ + ) mass: MeV : s (uds) I(J P ) = 0(½ + ) mass: MeV : s n n n n n n n stable (!) n + e - + ν e Λ n + π MeV (36%) Λ + π MeV (64%) n n n Λ n n 15 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

12 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 Λ-hyernucleus weak decay free Λ decay N ~ 100 MeV/c N W Λ n + π MeV (36%) Λ + π MeV (64%) τ Λ 263 s I = ½ rule (not theoretically understood) hyernucleus mesonic decay N W suressed by Pauli blocking F ~ 270 MeV/c Γ T = Γ M + Γ NM Γ M = Γ π0 + Γ π- Γ NM = Γ n + Γ + Γ 2 hyernucleus non-mesonic decay N ~ 400 MeV/c N W Λ + n n + n MeV Λ + n MeV τ Λ??? dominant in all but the lightest hyernuclei S N N 18

13 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 DAΦNE 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 crossing angle 12.5 mrad frequency (max) MHz bunch/ring u to 120 art./bunch current/ring 5.2 A (max) A Z e Κ e sto OSIM Be window beam ie A ( Z ( A2) ( A3) Κ A Z ( Z ( Z A 1) 1) Z 1) tofino Κ ISIM targets n 20 n n

14 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 FINUDA key features very thin nuclear targets ( g/cm 2 ) high resolution sectroscoy coincidence measurement with large accetance decay mode study event by event K + tagging continuous energy and rate calibration irradiation of different targets in the same run systematic error reduction 24

15 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 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 Physics outut (S = -1) sectroscoy low-energy N -Y interaction neutron-rich Λ-hyernuclei medium effect n n n n Λ n deely bound K states M. Agnello et al., PRL 94 (2005) B weak interaction (weak) decay quark substructures 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)

16 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 Mesonic weak decay (MWD) Exerimental observables - /, 0 / (single) article decay sectra Addressed/addressable issues s-shell hyernuclei -N otential -shell hyernuclei distortion effect and MWD enhancement - -nucleus otical otential J assignment indirect sectroscoic tool 27

17 Hyernucleus decay: the FINUDA strategy 28 inclusive roduction - sectrum K - (n) background subtracted q.f. background decay - and sectra Λ q.f. + K - (n) background subtracted accetance corrected A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

18 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA body decays background free 7 Li Λ J assignment M. Agnello et al., PLB 681 (2009) Be: 3/2 - g.s. & 1/2 - (429 kev) limited energy resolution A. Gal, NPA 828 (2009) 72. Clear corresondence with the calculated strength functions: T. Motoba et al, Progr. Theor. Phys. Sul. 117 (1994) 477. A. Gal, Nucl. Phys. A 828 (2009) 72. Formation of different excited states of the daughter nucleus Initial hyernucleus sin J ( 7 Li g.s. ) = 1/2 + (J. Sasao, Phys. Lett. B 579 (2004) 258.) T. Motoba, rivate communication 29

19 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 background free 9 Be Λ J assignment 9 B: 3/2 - g.s. & 1/2 - (2.75 MeV) limited energy resolution M. Agnello et al., PLB 681 (2009) 139. T ~ 4 38 MeV A. Gal, NPA 828 (2009) 72. Clear corresondence with the calculated strength functions: T. Motoba et al., Progr. Theor. Phys. Sul. 117 (1994) 477. A. Gal, Nucl. Phys. A 828 (2009) 72. Initial hyernucleus sin J ( 9 Be g.s. ) = 1/2 + (O.Hashimoto et al., Nucl. Phys. A 639 (1998) 93c.) T. Motoba, rivate communication 30

20 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 background free 11 B Λ J assignment M. Agnello et al., PLB 681 (2009) C: 3/2 - g.s. & 7/2 - (~6.5 MeV) limited energy resolution A. Gal, NPA 828 (2009) 72. Clear corresondence with the calculated strength functions: H. Bandō et al, Pers. Meson Science (1992).571 A. Gal, Nucl. Phys. A 828 (2009) 72. Two contributions of the 11 C ground state 5/2 - and its 7/2 - excited state Initial hyernucleus sin J π ( 11 B Λ g.s. ) = 5/2 + exerimental confirmation by different observable (Y. Sato et al., Phys. Rev. C 71 (2005) ) T. Motoba, rivate communication 31

21 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA / ratio deendence on A - / = tot / BR - tot / = (0.990 ± 0.094) + (0.018 ± 0.010) A fit to measured values for A = 4-12 hyernuclei FINUDA data revious data 1/2 + 1/2 + T. Motoba, PTPS 117 (1994) 477 A. Gal, NPA 828 (2009) 72 5/2 + strong nuclear structure effects M. Agnello et al., NPA 881 (2012) /2 + 3/ A

22 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 Non-mesonic weak decay (NMWD) Exerimental observables n, 2N and FSI contributions NM = n + + 2N (single & coincidence) article decay sectra Addressed/addressable issues 4-baryon strangeness-changing weak interaction I = 1/2 rule validity from s-shell ( 4 H ) and heavier hyernuclei n / 2N determination search for 2N exerimental evidence 34

23 Anatomy of NMWD sectra sectra K - (n) background subtracted M. Agnello et al., PLB 685 (2010) 247. (*) (*) 1N + 2N + FSI!!! 15 MeV threshold! (*) (*) M. Agnello et al., NPA 804 (2008) 151. common features: low energy rise structure at ~80 MeV 35 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

24 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 2N W. Alberico and G. Garbarino, PR 369 (2002) 1. assumtion and FSI determination M. Agnello et al., PLB 685 (2010) 247. NMWD G. Garbarino, A. Parreño and A. Ramos, PRL 91 (2003) G. Garbarino, A. Parreño and A. Ramos, PRC 69 (2004) gaussian fit free assumtion A low A high 2N / NMWD n / 1N A low 1N 2N from fit A high + 2N + FSI + FSI (T > 70 MeV) ~5% 2N 36 indeendent on A

25 FSI and 2N induced non-mesonic decay sectra background subtracted and accetance corrected M. Agnello et al., PLB 685 (2010) 247. (*) (*) (*) (*) M. Agnello et al., NPA 804 (2008) A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

26 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 2N R and FSI determination E. Bauer and G. Garbarino, NPA 828 (2009) 29. assumtion 2N / ~ n / n : n : n = 0.83 : 0.12 : 0.04 A low A low A high 0.5 N( N( n) M. Agnello et al., PLB 685 (2010) 247. FSI linear on A u to A = 16 E. Bauer and G. Garbarino, NPA 828 (2009) 29. H. Bhang et al., EPJA 33 (2007) 259: ~ C J.D. Parker et al., PRC 76 (2007) : He (95% c.l.) M. Kim et al., PRL 103 (2009) : 0.29 ± C n) N( n R( A) N( n nn) N assumtion a ba nn) N FSI low FSI low FSI high N 2 / / 38 ba suorted by both exeriment and theory 2 / 1 and n / indeendent on A / / 1 / NM n 2 A low weighted average H. Bhang et al., EPJA 33 (2007) 259. A high

27 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 2N R( A) R N imroved determination n A) (cos 0.8, E 20 MeV) N ( E single sectra fit) FINUDA Collaboration and G. Garbarino., PLB 701 (2011) 556. systematics: all -shell a ba 0.5 ( 2 ba assumtion N( n nn) N 0.5 N( n) N 2 / indeendent on A NM n / 2 / stat / stat M. Kim et al., PRL 103 (2009) : 0.29 ± C. FINUDA Collaboration and A. Gal., PLB 685 (2010) : 0.24 ± sys sys sys sys FSI low statistics direct measurement reduced error 39 FSI E. Bauer and G. Garbarino, PRC 81 (2010)

28 Exclusive NMWD? theoretical advice urgently needed! μ from Gaussian fit S. Bufalino, NPA 914 (2013) 160. simlified hyothesis: n n A ( A Z 2) ( Z 1 ) n 40 n A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

29 FSI and 2N induced non-mesonic decay M. Agnello et al., PLB 685 (2010) 247. (*) (*) (*) (*) M. Agnello et al., NPA 804 (2008) 151. "simle" kinematical calculation 41 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

30 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 2N induced weak decay relevance first ointed out by: W.M. Alberico et al., PLB 256 (1991) 134 key role in data interretation several exerimental evidences, but indirect E. Botta, T. Bressani, G. Garbarino, EPJA 48 (2012) 21 smoking gun evidence missing! many theoretical redictions E. Bauer G. Garbarino A. Parreño A. Ramos imortance of the effect: ~20-25% of the total NMWD width exerimental hardness: 3 nucleons emitted from -hyernucleus g.s. 4-fold coincidence measurement ( -,, n, n) 42

31 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 2N induced decay ex. evidence trile coincidence: (n + n + ) events exclusive n nn decay event: 7 first, direct exerimental evidence Li 4 He n n - = ± 1.2 MeV/c 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() = ± 0.85 MeV (n1 n2) = 94.8 ±3.8 (n1 ) = ±3.4 (n2 ) = 154 ±19 no n-n or /n scattering M. Agnello et al., NPA 881 (2012)

32 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 2N induced decay ex. evidence trile coincidence: (n + n + ) events exclusive n nn decay event: 7 Li 4 He n n - = ± 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() = ± 0.50 MeV (n1 n2) = ±5.4 (n1 ) = 53.5 ±4.3 (n2 ) = ± no n-n or /n scattering

33 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 2N induced decay ex. evidence trile coincidence: (n + n + ) events exclusive n nn decay event: 9 Be 3 He 3 H n n - = ± 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() = ± 0.80 MeV (n1 n2) = ± 7.5 (n1 ) = ± 5.5 (n2 ) = 95.4 ± 3.6 no n-n or /n scattering 45

34 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013 Summary and outlook MWD - sectra for 7 Li, 9 Be, 11 B and 15 N 7 Li, 9 Be and 11 B g.s. J assignment confirmed 15 N g.s. J first determination MWD decay rate extracted strong nuclear structure effect ut in evidence NMWD -induced NMWD roton sectra from 5 He to 16 O 2N -induced NMWD contribution determination first exerimental evidence of the 2N -induced NMWD exclusive rocess dominance in 1N and 2N decay? Further investigations needed both exerimental and theoretical 47

35 E18 E22 Future dedicated exeriments Coincidence measurement of the weak decay of 12 C Λ and the three-body weak interaction rocess Exclusive study of the Λ N weak interaction in A = 4 Λ-hyernuclei 49 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013

36 Aknowledgement A secial thanks to: Michelangelo Agnello Elena Botta Tullio Bressani Stefania Bufalino 50 A. Feliciello / Fourth International Conference on Nuclear Fragmentation Kemer (Antalya), Turkey, 29 Setember - 6 October, 2013 NUFRA2013