FINUDA: latest results and inheritance

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1 FINUDA: latest results and inheritance Alessandro Feliciello Istituto Nazionale di Fisica Nucleare - Sezione di Torino Via P. Giuria 1, I Torino, Italy FINUDA was a complex magnetic spectrometer installed on the DAΦNE e + e collider, the φ-factory operating at the INFN National Laboratories in Frascati, near Rome. It was built in the manner of a typical collider apparatus but it was specifically designed to carry on a nuclear physics experiment. Actually the community gathered around this project performed a complete study of single -hypernuclei. The leading idea was to exploit the unique and, most likely, inimitable properties of K following the φ resonance disintegration. As a matter of fact, the K very low energy and their substantial monochromaticity allowed to perform fine spectroscopy of several p-shell hypernuclei [1 4]. Moreover, the collider geometry makes the FINUDA spectrometer a powerful tool for coincidence measurements. Then it was possible to address a systematic study of both mesonic and nonmesonic weak decay modes [2, 5 9]. The latest, but not least, FINUDA results are just related to these two topics. Search for neutron-rich nuclear systems is stimulated by the interest in studying nuclear matter under extreme conditions. The experimentally proven binding property of a hyperon, makes possible to observe nuclear bound systems with neutron to proton ratio even higher than for ordinary nuclei (N/Z( 6 H) = 4 > N/Z( 8 He) = 3). After a first attempt to discover such exotic objects [10], FINUDA succeeded in finding three candidate events for bound 6 H hypernucleus [11]. This analysis exploited at best the momentum high-resolution featured by the spectrometer and its powerful capability of doing coincidence measurements [12]. The two-nucleon induced -hypernucleus weak decay mechanism is generally believed to significantly contribute to the total decay width. However no experimental evidence for such process was ever found. Also in this case a dedicated analysis allowed to isolate three candidate events [9]. In summary the FINUDA Collaboration fully accomplished its commitment, providing a long series of interesting and, sometime, unexpected results. Future prospects for hypernuclear physics are essentially represented by the experimental Alessandro.Feliciello@to.infn.it

2 activities approved to run at J-PARC, the new Japanese accelerator center where it is now possible to find a large availability of dedicated experimental tools and particle beams and the main concentration of specific culture in the field. References [1] FINUDA Collaboration, Phys. Lett. B 622 (2005) 35. [2] FINUDA Collaboration, Phys. Lett. B 681 (2009) 139. [3] FINUDA Collaboration, Nucl. Phys. A 835 (2010) 414. [4] FINUDA Collaboration, Phys. Lett. B 698 (2011) 219. [5] FINUDA Collaboration, Nucl. Phys. A 804 (2008) 151. [6] FINUDA Collaboration, Nucl. Phys. A 835 (2010) 439. [7] FINUDA Collaboration, Phys. Lett. B 685 (2010) 247. [8] FINUDA Collaboration, Phys. Lett. B 701 (2011) 556. [9] FINUDA Collaboration, Nucl. Phys. A 881 (2012) 322. [10] FINUDA Collaboration, Phys. Lett. B 640 (2006) 145. [11] FINUDA Collaboration, Phys. Rev. Lett. 108 (2012) [12] FINUDA Collaboration, Nucl. Phys. A 881 (2012)

3 FINUDA: latest results and inheritance p n n p n p p p n n p p n n p November 20-23, 2012, Milano, Italy Alessandro Feliciello I.N.F.N. - Sezione di Torino

4 Outline 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 2

5 DAΦNE 3 e Κ + e + + φ Κ A Z A Z Κ + + π energy 510 MeV luminosity cm -2 s -1 σ x (rms) σ y (rms) σ z (rms) bunch length 2.11 mm mm 35 mm 30 mm crossing angle 12.5 mrad frequency (max) MHz bunch/ring up to 120 part./bunch current/ring 5.2 A (max) A Z OSIM Be window beam pipe A ( Z ( A2) ( A3) + 1) + π ( Z ( Z 1) + 1) + targets ISIM tofino p + n p + n + n

6 FINUDA key features 4 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

7 Physics output (S = -1) 5 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 low-energy N -Y interaction neutron rich -hypernuclei medium effect n p p n n p p n p p n deeply 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) 322

8 m a i n The background issue K A + Z (Z 2) + π A + K 6 6 Li + H + π 6 5 H ( Li ) : u. l. = (2.5 ± 1.4) 10 / K 6 90% background subtraction b a c k g r o u n d L int 220 pb K Li + H + π + M. Agnello et al., PLB 640 (2006) 145 c. l 6.

9 The status of the art 7 K A + Z (Z 2) + π A A A π + Z ( Z 2) + K + + K - + p π 0 +, π 0 + p π + + n: 2-step (S-EX + C-EX) K - + p K 0 + n, K 0 + p + π + : 2-step (C-EX + S-EX) K - + p π + + Σ -, Σ - + p + n: 1-step (S-EX) experimental results theoretical predictions He ( Be) : u. l. = / K Be ( C) : u. l. = / K C ( O) : u. l. = / K π - + p π 0 + n, π 0 + p K + + : 2-step (C-EX + AP) π - + p K 0 +, K 0 + p K + + n: 2-step (AP + C-EX) π - + p K + + Σ -, Σ - + p + n: 1-step (AP) experimental results Li ( 10 B) : dσ / dω = nb / sr 10 ± KEK KEK INFN-LNF H ( Li) : u. l. = (2.5 ± 1.4) 10 / K H ( Li) : u. l. = (4.5 ± 1.4) 10 / K Be ( C) : u. l. = (2.0 ± 0.4) 10 / K K. Kubota et al., NPA 602 (1996) 327 M. Agnello et al., PLB 640 (2006) / K 6 7 T.Y. Tretyakova et al., NPA 691 (2001) 51c theoretical predictions P.K. Saha et al., PRL 94 (2005) T.Y. Tretyakova et al., PAT 66 (2003) 1681

10 The new NRH search strategy 8 ΔL int 960 pb -1 K 6 6 Li + H + π + 6 H 6 He + double C-EX p ~ 252 MeV/c π 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) π, K, p, d, separation (OSIM & LMDC de/dx) high momentum resolution 6 FWHM 270 MeV/c 6% FWHM 110 MeV/c (tracker performance + He bag + thin target)

11 Analysis technique 9 K 6 6 Li + H + π + 6 H 6 He + 6 ( τ ( He) 801 ms) atomic mass tables π = ± 1.3 M 2 ( 6 He) + p 2 (π ) M( 6 He) MeV if 6 H is a stable system 2 independent two-body reactions: decay at rest M M ( 2 6 ( 6 H ) + p ( MeV with B = ( π ) M ( 6 H ) 5 H ) = M ( H ) + M ( ) B( ) MeV) + cut on T ( π ) + T ( π ) : MeV

12 Data selection 10 absolute energy scale: μ + (235.6 MeV/c) from K μ2 Δ p < 0.12 MeV/c π - (132.8 MeV/c) from 4 H Δ p < 0.2 MeV/c systematic errors σt sys = 0.17 MeV σt(π + ) = 0.96 MeV, σt(π - ) = 0.84 MeV σt exp = 1.3 MeV σt = 1.3 MeV FINUDA Coll. And A. Gal, NPA 881 (2012) T ( π ) + T ( π ) : MeV

13 Data selection MeV/c (σ p =1.1 MeV/c) MeV/c (σ p =1.2 MeV/c) 5 H + 3 H + 2n + 4 H + 2n 0.0 MeV -1.7 MeV MeV selection range fixed by including 6 H lowest particle stability threshold p π+ = MeV/c p π- = MeV/c B = MeV (out of ped K - event)

14 Production rate 13 background sources accidentals: π + ( MeV/c) and π - ( MeV/c) 0.27 ± 0.27 ev. 6 + K + Li Σ 4 + π - + He + n n + π + K Li H + n + n + π + 4 He + π - production rate total background on 6 Li: end point ~190 MeV/c end point ~282 MeV/c end point ~252 MeV/c p(π - ) = 133 MeV/c BGD1 + BGD2 = 0.43 ± 0.28 ev ± 0.07 ev. negligible Poisson statistics: 3 events DO NOT belong to pure C.L. = 99% BR( π ) 4 H = 0.49 H. Tamura et al., PRC 40 (1989) R479 + R BR( π ) = (3 BGD1 BGD2) /[ ε ( π ) ε ( π )( n. 6 R BR( π ) = (2.9 ± 2.0) 10 / R / 6 = (5.9 ± 4.0) 10 K FINUDA Coll. and A. Gal, PRL 108 (2012) K (2.5 K on ± ) 10 / K 6 Li)] M. Agnello et al., PLB 640 (2006) 145

15 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 nrh prod. rate: ~10-2 hyp. prod. rate in (K -, π - ) 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 production MeV MeV FINUDA Coll. and A. Gal, PRL 108 (2012) FINUDA Coll. and A. Gal., NPA 881 (2012) 269

16 Physics output (S = -1) 19 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 low-energy N -Y interaction neutron rich -hypernuclei medium effect n p p n n p p n p p n deeply 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) 322

17 2N induced weak decay 21 relevance first pointed out by: W.M. Alberico et al., PLB 256 (1991) 134 key role in data interpretation many theoretical predictions several experimental evidences, but indirect E. Botta, T. Bressani, G. Garbarino, EPJA 48 (2012) 21 E. Bauer G. Garbarino A. Parreño A. Ramos importance of the effect: ~20-25% of the total NMWD width smoking gun evidence missing! experimental hardness: 3 nucleons emitted from -hypernucleus g.s. 4-fold coincidence measurement (π -, p, n, n)

18 2N induced decay exp. evidence 22 triple coincidence: (n + n + p) events exclusive np nnp decay event: 7 4 Li He + p + n + n first, direct experimental evidence p π- = ± 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 ϑ(n1 n2) = 94.8 ±3.8 ϑ(n1 p) = ±3.4 ϑ(n2 p) = 154 ±19 no n-n or p/n scattering M. Agnello et al., NPA 881 (2012) 322

19 2N induced decay exp. evidence 23 triple coincidence: (n + n + p) events exclusive np nnp decay event: 7 4 Li He + p + n + n p π- = ± 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 ϑ(n1 n2) = ±5.4 ϑ(n1 p) = 53.5 ±4.3 ϑ(n2 p) = ±3.9 no n-n or p/n scattering

20 2N induced decay exp. evidence 24 triple coincidence: (n + n + p) events exclusive np nnp decay event: Be He+ H + p + n + n p π- = ± 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 ϑ(n1 n2) = ± 7.5 ϑ(n1 p) = ± 5.5 ϑ(n2 p) = 95.4 ± 3.6 no n-n or p/n scattering

21 Background evaluation 25 K + ( np) Σ + p Σ π + n 7 Li p Σ - π - n Target ϑ(π 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 cosϑ(π - p)and E p was studied for the simulated background: major contribution from this source when π 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 cosϑ(π - p) and E p on 7 Li and 9 Be: ~10-3 events were found for both targets the 2 np nnp real events DO NOT belong to background to a confidence level 99%.

22 2008 scenario completed upgrading running in preparation stand-by in preparation completed 26 A. Feliciello / 6 th Japan-Italy Symposium on Heavy-Ion Physics Perspectives in Nuclear Physics, Tokai, Japan, November 11-15, 2008.

23 2012 scenario completed running upgrading running running in preparation in preparation running completed stand-by in preparation running! completed 27

24 Future speaks Japanese 28 participants (170) 4% 12% 7% 19% 14% 9% 35% China Germany Italy Japan Spain USA others next HYP: Sendai, 2015

25 J-PARC scientific program 22 experiments 7 proposals 4 tests 30

26 Physics output (S = -1) 31 E10 E13 nuclear models γ spectroscopy low-energy N -Y interaction neutron rich -hypernuclei medium effect n p p n n p p n p p n deeply bound K states 4B weak interaction (weak) decay quark substructures E15 E27 E18 E22

27 Physics output (S = -2) nuclear models strangelets H dibaryon existence E03 E05 E07 spectroscopy p n n p (weak) decay double deeply bound K states S=-2 system g.s. low-energy Y-Y interaction H particle mass P42 33

28 The ULYSSES initiative 34 U n r a v e L in g h Y p e r n u c l e a r S p e c t r o s c o p y a n d S t r u c t u r e E x p e r i m e n t S a special thank to: (

29 E13 experiment layout γ-ray spectroscopy of hypernuclei top view 35 further study of N interaction: 4 He, 10 B, 11 B, 19 F N-ΣN coupling and 3-body force charge symmetry breaking (n p?) radial dependence (interaction range) g in a nucleus from spin-flip B(M1): 7 Li SksMinus + HyperBall K1.8 beam line Hyperball J-PARC side view

30 E05 experiment layout 37 first spectroscopic study of S = -2 systems in (K -,K + ) reaction ΞN interaction attractive or repulsive depth of Ξ-nuclear potential isospin dependence ΞN- coupling force SksPlus Spectroscopic study of Ξ-hypernucleus, 12 Be Ξ, via the 12 C(K -,K + ) reaction

31 Summary 39 Last but not least results from FINUDA: first experimental evidence for the heavy hyperhydrogen 6 H 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

32 41 Thank you! 有り難う