Simonetta Marcello Torino University JAEA Tokai-mura, October 26, 2010 Hypernuclear Weak Decay Measurements with FINUDA Experiment 1 Simonetta Marcello.Torino University JAEA-October 2010

OUTLINE FINUDA Experiment Study of Hypernuclear Weak Decays Mesonic Weak Decays (MWD) Non-Mesonic Weak Decays (NMWD) Two body Rare Non-Mesonic Weak Decays 2 Simonetta Marcello.Torino University JAEA-October 2010

DAFNE e + -e - Collider e + - e - Beams of 510 MeV at the c.m. energy of  (1020) meson circulating in two different rings collide in two interaction regions e-e- e+e+ 3 Simonetta Marcello.Torino University JAEA-October 2010 DA  NE is a high luminosity  Factory L ~ 2.2x10 32 cm -2 s -1  ~ 900  /s  8 pb -1 /day DA  NE is a high luminosity  Factory L ~ 2.2x10 32 cm -2 s -1  ~ 900  /s  8 pb -1 /day

KLOE CP, CPT violation chiral dynamics … KLOE CP, CPT violation chiral dynamics … FINUDA Strangeness Nuclear Physics FINUDA Strangeness Nuclear Physics SIDDHARTA K - N scattering SIDDHARTA K - N scattering K S K L 34%  13% K + K - 49% Φ Decays DecayBR (%)p (MeV/c) K + K K 0 L K 0 S  13  +  -  E kin 16 MeV Low Energy kaons can be stopped in Nuclear Targets neutral and charged kaons collinear (Back-to-Back) and tagged monochromatic and low energy 4 Simonetta Marcello.Torino University JAEA-October 2010

DAFNE Peak Luminosity history FINUDA DAFNE e + -e - Collider RUN-1 RUN-2 5 Simonetta Marcello.Torino University JAEA-October 2010 FINUDA

DAFNE e + -e - Collider 6 Simonetta Marcello.Torino University JAEA-October 2010 DAFNE Peak Luminosity history In the last years further improvement in the Luminosity has been achieved L ~ 3÷4x10 32 cm -2 s -1 peak luminosity In the last years further improvement in the Luminosity has been achieved L ~ 3÷4x10 32 cm -2 s -1 peak luminosity FINUDA

RUN-2: October 2006 – June 2007 Integrated Luminosity ~ 1 fb -1 HYP events: ~ 5 millions Daily integrated luminosity [nb-1] Integrated luminosity [nb-1] Average daily integrated luminosity ~ 7 pb -1 Stable Data Taking 7 Simonetta Marcello.Torino University JAEA-October 2010

8 FINUDA DAΦNE Structure of a collider experiment Large acceptance: > 2  sr B=1T omogeneous magnetic field within 2% Large acceptance: > 2  sr B=1T omogeneous magnetic field within 2% Mechanical frame Vertex/target Drift Chambers, Straw tubes Magnet end-caps TOFONE detector

Simonetta Marcello.Torino University JAEA-October Fixed TARGET Experiment K - are stopped in very thin targets Different Targets at the same time FINUDA is a target experiment with cylindrical geometry e  e   Φ  K  K  127 MeV/c 16 MeV 12.5 mrad Φ e-e- e+e+ Not exactly at rest boost of 12.3 MeV/c π -π - π -π - p K+K+  μ+μ+ K-K- 12 C 51 V 27 Al 12 C 7 Li 6 Li

 HYPERNUCLEAR PHYSICS  Spectroscopy  Weak Decays  HADRON PHYSICS with STRANGENESS  Bound Kaonic Clusters Detection and full reconstruction of particles Coincidence measurement with large acceptance FINUDA Physics SIMULTANEOUSLY ON DIFFERENT TARGETS Very thin nuclear targets (0.1 ÷ 0.3 g/cm 2 ) High Resolution Spectroscopy  p/p = 0.6% Detection and full reconstruction of particles Very good  identification K  stop + A Z  A  Z +   10 Simonetta Marcello.Torino University JAEA-October 2010

Hypernuclear Event   K+K+ K-K-  6 Li Forward track K  stop A Z  A  Z   K        Forward    track 11 Simonetta Marcello.Torino University JAEA-October 2010

 Selective trigger based on fast scintillation detectors  Clean K - vertex identification ISIM P.ID.+ x,y,z resolution + K + tagging  , K, p, d, t … Particle Identification (dE/dx)  High momentum resolution (6‰ FWHM) tracker resolution+He bag+thin targets  6‰ for  MeV/c for spectroscopy  1% for  MeV/c for decay study  6 % for  MeV/c for mesonic decay study  2 % for MeV/c for non-mesonic decay study  Time-Of-Flight (TOF system)  Neutron detection (external Scintillator barrel) Detector capabilities 12 Simonetta Marcello.Torino University JAEA-October 2010

FINUDA Data Takings RUN Integrated Luminosity: ~ 1 fb -1  five millions of HYP events RUN Integrated Luminosity: ~ 1 fb -1  five millions of HYP events Targets: 2x 6 Li, 2x 7 Li, 1x 13 C, 1x 9 Be, 1x 16 O Medium-light targets to allow a wider spectrum of physics:  hypernuclear spectroscopy  NRH spectroscopy  hypernuclear decay modes  bound kaonic states RUN Integrated Luminosity: 190 pb -1  one million of HYP events RUN Integrated Luminosity: 190 pb -1  one million of HYP events Targets: 2x 6 Li, 1x 7 Li, 3x 12 C, 1x 27 Al, 1x 51 V  12 C reference target for detector performance tuning  27 Al V medium-heavy nuclei for spectroscopic studies  6 Li -- 7 Li sources of light hypernuclei 13 Simonetta Marcello.Torino University JAEA-October 2010

14 Hypernuclear Weak Decays: Mesonic channels Free Space p +   B.R %   - free n+   B.R %   0 free Q ~ 38 MeV ; p N = p  ~ 100 MeV/c Δ I = ½ Rule Exp   - free   0 free  1.78   - free   0 free  2 pure Δ I = 1/2   - free   0 free  1/2 pure Δ I = 3/2   p +     n +     Q M < 38 MeV ; p N ~ 100 MeV/c < k F = 270 MeV/c Mesonic mode (MWD) is Pauli Blocked But still possible in finite nuclei In the Nuclear Medium Hamiltonian describes transitions with Δ I of 1/2 and 3/2 with comparable strengths BUT an enhancement in Δ I = 1/2 component is observed in free Y decays and K decays Strong interaction corrections are added But not enough to account for such an enhancement

15 Hypernuclear Weak Decays: Non-Mesonic channels  p  n p  n  n n nn pp One-Nucleon induced Decays  Nucleons can escape the nucleus  Non-Mesonic mode (NMWD) is not Pauli Blocked  NMWD dominates over the Mesonic one for all hypernuclei, but the lighter ones, where is in competition with the MWD  Final State Interaction (FSI) cannot be neglected in NMWD Q M ~ 176 MeV ; p N ~ 415 MeV/c > k F = 270 MeV/c Nucleon pairs mainly emitted back-to-back Difficult to measure neutrons, low efficiency  N N  n N N  2N Two-Nucleon induced Decay Q M ~ 176 MeV p N ~ 340 MeV/c Q M shared among the three Nucleons

16 Hypernuclear decays: only way to get information on  N  NN Extension of NN  NN weak interaction with ΔS = 0, in particular on the parity conserving part of the Hamiltonian (masked by strong interaction) No experimental observation of  N  NN using  beams. Possible to study the reverse reaction pn  p   but not feasible  very low  ~ mb Hypernuclear Weak Decays  Tot =  M +  NM  M =   - +   0 ;  NM =  p +  n +  2N  = ℏ  Tot hypernucleus lifetime Simonetta Marcello, JSPS Fellow, Kyoto University-Intensive Lectures-July 29-31, 2009

17 Hypernuclear Weak Decays: Non-Mesonic channels N  N , K, K* NN  NNNN One-Nucleon induced Decays Two-Nucleon induced Decay One Meson Exchange Model Massive mesons ( , K, K*,  and  ) have been included to explain interaction at short distances One Pion Exchange Model Not enough to explain  n /  p ratio Hybrid models adopting direct quark mechanisms in addition to meson-exchange potential have been used Simonetta Marcello, JSPS Fellow, Kyoto University-Intensive Lectures-July 29-31, 2009

Mesonic Weak Decays  -nucleus optical potential, the low energy  probes the nuclear structure  possibile to discriminate among different potential models (instead of studying  -nucleus scattering or X-rays from pionic atoms) Enhancement of the  -mesonic decay rates due to the pion wave distortion  higher momentum available for the Nucleon J  assignment hypernuclei, strong dependence of the two-body  - decay Branching Ratios on the ground state spin: new indirect spectroscopic tool 18 PHYSICS MOTIVATIONS

Non-Mesonic Weak Decays 4-baryon strangeness changing weak interaction give the possibility to investigate both the parity violating and the parity conserving contributions to the Hamiltonian (in NN  NN the latter one is masked by the strong interaction)  I=1/2 rule  n /  p puzzle  2N and Final State Interactions (FSI) contributions 19

Study of Weak Decays with FINUDA p -- charged Non-Mesonic channel K - stop + A Z  A  Z +  - A  Z  A-2 (Z-1) + p + n NMWD MeV/c charged Mesonic channel K - stop + A Z  A  Z +  - A  Z  A (Z+1) +  - S-EX MeV/c MWD MeV/c -- -- 20 Simonetta Marcello.Torino University JAEA-October 2010 Coincidence measurement

21 Mesonic Weak Decays

MWD strictly forbidden in infinite nuclear matter (p N ~ 100 MeV/c)  feels attraction in nuclear medium due to the p-wave part of the optical potential (  distortions)  dispersion relation modified inside the nucleus  pion carries lower energy for fixed momentum q: E  ≤ √ (q 2 +m  2 )  Energy conservation: higher momentum available for the final nucleon which has more chance to overcome the Fermi momentum theoretical calculations with pion distorted wave predict MWD to be less suppressed for p-shell (A~10) Enhancement of MWD due to pion wave distortion: Bando et al., Progr. Theor. Phys. Suppl. 72 (1984) 109 Oset et al., NPA 443 (1985) 704 Extensive calculations: Motoba et al., Prog. Theor. Phys. Suppl. 117 (1994) 477 Gal Nucl. Phys. A 828 (2009) 72 Mesonic weak Decays p-shell hypernuclei 22 Simonetta Marcello.Torino University JAEA-October 2010 Pauli Blocking is less effective in the medium !

23 Study of Mesonic Decays K - + A Z  A  Z +   – A  Z  A (Z + 1) +   – Hypernucleus Formation high   – momentum ~ 270 MeV/c In the bound region from the ground state peak Hypernucleus Decay low   – momentum ~ 100 MeV/c  Not Pauli blocked in Light p-shell Hypernuclei  Can provide information on spin-parity of the initial hypernuclear ground state A  Z  A Z +   0  0 not detected in FINUDA Short track reconstructed by means of 2 layers of Si-Microstrips and 1 layer of Low Mass Drift Chambers Δp/p =1% FWHM Cuts are reduced Δp/p =6% FWHM Only 3 points Simonetta Marcello.Kyoto University-Intensive Lectures-July 29-31, 2009

Simonetta Marcello.Torino University JAEA-October 2010 MWD Measurements: strategy 12  C 11  B Inclusive production  - spectrum background corrected 11  B -- 24 Background under formation peak K - (np)   - p  -  n  - SHORT TRACKS (in Si-Microvertex) Detection of  - down to ~ 80 MeV/c LONG TRACKS (4 points)  p/p ~ 1% in the region MeV/c Background under decay peak  qf decay Decay  - spectrum background & acceptance corrected Branching Ratio BR  – =   – /  TOT BR  – = N  decays / N HYP

25 Study of Mesonic Decays K Li  7  Li +   – (276 MeV/c) K Li  5  He + d +   – K Li  5  He + p + n +   – 7  Li  7 Be +   – (107.7 MeV/c) 5  He  5 Li +   – (99.3 MeV/c) 7 Li Target Mesonic Weak Decay of Hypernuclei is important because it takes place deeply inside the nucleus (since the  is in s-shell s 1/2 ) and involves a low energy , so it can sensitively probe the structure of nuclear interior Mesonic Decay Simonetta Marcello.Kyoto University-Intensive Lectures-July 29-31, 2009

T. Motoba (Private Communication) ) 7 Be: 3/2 - gs & 1/2 - (429keV) 3-body decays Agnello PLB 681 (2009) 139 J  assignment: 7  Li Gal NPA 828 (2009) 72 Correspondence with the calculated strength functions T. Motoba et al, Progr. Theor. Phys. Suppl. 117 (1994) 477 A. Gal, Nucl. Phys. A 828 (2009) 72 Formation of different excited states of the daughter nucleus Initial hypernucleus spin J π ( 7  Li g.s. ) = 1/2 + Sasao, PLB 579 (2004) BR  – = ± 0.041

9 B: 3/2 - gs & 1/2 - (2.75 MeV)  T ~ 4 MeV MeV Agnello PLB 681 (2009) 139 T. Motoba (Private Communication)) Correspondence with the calculated strength functions T. Motoba et al, Progr. Theor. Phys. Suppl. 117 (1994) 477 A. Gal, Nucl. Phys. A 828 (2009) 72 Initial hypernucleus spin J π (   Be g.s. ) = 1/2 + O.Hashimoto NPA 639 (1998) 93c 27 J  assignment: 9  Be BR  – = ± 0.040

11 C: 3/2 - gs & 7/2 - (~6.5 MeV) Agnello PLB 681 (2009) 139 Correspondence with the calculated strength functions H. Bando et al, Pers. Meson Science (1992) 571 A. Gal, Nucl. Phys A 828 (2009) 72 Two contributions of 11 C 5/2 - ground state and 7/2 - excited state Initial hypernucleus spin J π ( 11 Λ B g.s. ) = 5/2 + : experimental confirmation Sato et al., PRC 71 (2005) by different observable T. Motoba (Private Communication) 28 J  assignment: 11  B BR  – = ± 0.039

15 O: 1/2 - gs & sd (~6 MeV) Agnello PLB 681 (2009) 139 Correspondence with the calculated strength functions T. Motoba et al, Nucl. Phys. A 489 (1988) 683 A. Gal, Nucl. Phys. A 828 (2009) Λ N g.s spin not known. J π ( 15 Λ N g.s. ) = 3/2 + D.J.Millener, A.Gal, C.B.Dover Phys. Rev. C 31 (1985) 499 Spin ordering not obtained from  -rays of 16  O M.Ukai et al. Phys. Rev.C 77 (2008) First experimental determination of J π ( 15 Λ N g.s. ) = 3/2 + from decay rate value and spectrum shape T. Motoba NPA 489 (1988) J  assignment: 15  N BR  – = ± 0.028

present data T. Motoba PTPS 117 (1994) 477 previous data A.Gal NPA 828 (2009) 72 A Mesonic decay ratio:   - /     - /   =  tot /    BR   tot /   = (0.990±0.094) + (0.018±0.010)  A fit from measured values for A=4-12 hypernuclei [ Sasao et al., PLB579(2004)258 ] strong nuclear structure effect  distortion, MWD enhancement proved ! 30 BR  = N  decays / N HYP

31 Non Mesonic Weak Decays

32 Hypernuclear Weak Decays:  n /  p Ratio  n  p  = 1/2 for pure ΔI = 1/2  n  p  = 2 for pure ΔI = 3/2 What about ΔI = ½ rule for  decay in the medium ? For a long time large experimental values have been measured (1 ÷ 2) indicating a possible violation of ΔI = ½ rule in hypernuclear decays and small theoretical values have been predicted (OPE model 0.1 ÷ 0.2)  n  n n  p  n p  N N  n N N Most studied systems: 5  He and 12  C The analysis of  n  p  ratio is influenced by the two-nucleon induced process, whose experimental identification is rather difficult

33 Hypernuclear Weak Decays:  n /  p Ratio  p  n p First measurement of nucleon-coincidence spectra and angular correlation (BtoB)  n  p ≈  N N  n N N  n  n n New experimental measurements and progress in theoretical models contributed to solve the  n  p  ”Puzzle” Theoretical improvements: havier mesons, interaction terms which violate ΔI=1/2 rule, quark degree of freedoms for the short range baryon-baryon interaction  n  p ≈  He 12  C Significant contribution of two-Nucleon induced decay and FSI (non-BtoB kinematics) quenching of N yields ~ 40% Bhang et al., EPJ A33 (2007) 259 Outa et al., NPA754 (2005) 157c, Kang et al., PRL96(2006) Sasaki et al., NPA669 (2000) 331 Parreno and Ramos, PRC65(2002)015204

Simulation of the background reaction K - n p  Σ - p followed by the decay Σ -  nπ - Fermi momentum distribution for nucleons selection criteria and quality cuts as for real data Simulated background π - and proton spectra from 12 Λ C NMWD Spectrum of negative pions for events with a proton detected in coincidence red peak at 272 MeV/c ( 12 Λ C ground state) π - spectrum in coincidence with p RUN-1 12 C Not acceptance corrected 339 events Not acceptance corrected proton spectra in coincidence with π - peak Acceptance corrected

35 proton spectrum in coincidence with π - peak π - and proton spectra from 12 Λ C NMWD background subtracted proton spectrum in coincidence with π - peak π - spectrum in coincidence with p RUN-1 12 C normalization region M. Agnello et al., NPA 804 (2008), 151 Short tracks  proton Threshold = 15 MeV 15 MeV K - np   - p  -  n π - coincidence simulation + reconstruction + selection + normalization

36  K - stopped in 7 Li target can produce: 7 Λ Li, ( 6 Λ He+p), ( 5 Λ He+d), ( 4 Λ He+t), ( 3 Λ He+α)  275 MeV/c peak is consistent with 7 Λ Li g.s.  269 MeV/c peak is consistent with 5 Λ He+d p max = 272,67 MeV/c ΔB Λ = 3.98 MeV π - and proton spectra from 7 Λ Li NMWD 269 MeV/c 275 MeV/c RUN-2 π - spectrum in coincidence with p Simulated background proton spectrum in coincidence with π - peak (275MeV/c) background subtracted proton spectrum in coincidence with π - peak (275MeV/c) Simulation of the background K - np → Σ - p followed by Σ - → nπ - Acceptance Corrected 7 Li

37 7 Li - π - and proton spectra from 5 Λ He NMWD 269 MeV/c 275 MeV/c RUN-2 π - spectrum in coincidence with p Acceptance Corrected Simulated background proton spectrum in coincidence with π - peak (269MeV/c) background subtracted proton spectrum in coincidence with π - peak (269MeV/c) K - stop + 7 Li  5 Λ He + d + π -  Enhancement of the low energy region FSI and 2 Nucleons induced effects  Bulk of the signal at 80 MeV (~ Q/2 value of the reaction) Simulation of the background K - np → Σ - p followed by Σ - → nπ - 7 Li

38 6 Li - π - and proton spectra from 5 Λ He NMWD Acceptance Corrected Simulated background proton spectrum in coincidence with π - peak background subtracted proton spectrum in coincidence with π - peak K - stop + 6 Li  5 Λ He + p + π - π - spectrum in coincidence with p RUN-2 Simulation of the background for the 2 Nucleons absorption take into account the cluster substructure of 6 Li as (  + d) molecule Momentum distribution of the deuteron inside 6 Li T. Yamazaki and Y. Akaishi NP A792 (2007 ) MeV/c 6 Li

5  He 7  Li 12  C  Similar shape for 5  He, 7  Li and 12  C  Peak at ~ 80 MeV (Q/2 value), broadened by N Fermi motion, visible even for 12  C  no strong FSI effect in low energy region  FSI & 2N contribution in the low energy region? 39 5 Λ He, 7 Λ Li and 12 Λ C proton spectra

40 Comparison with KEK experimental data FINUDA: NPA 804 (2008)151 KEK E462/E508: PLB 597 (2004)249 5 Λ He: FINUDA vs KEK 12 Λ C: FINUDA vs KEK  KEK: thick targets  strong correction  FINUDA: thin targets & transparent detectors  KEK: p energy from TOF and range + dE/dx  poor energy resolution above 100 MeV, distortion  FINUDA: p momentum from magnetic analysis 2% energy resolution 80 MeV, no distortion normalization beyond 35 MeV (KEK data threshold) Agreement for 5  He, not for 12  C

41 Comparison with theoretical calculations Comparison with theoretical models not satisfactory for 12  C  New data important to constrain theories in low energy region  12 Λ C: FSI and two-nucleons induced NMWD appear to be too strong to reproduce the data (low energy peak + excess smearing) Theoretical curve FINUDA proton spectra 5 Λ He (Garbarino,Phys. Rev. C [2004]) KEK 12 Λ C Garbarino,(P.R.C [2004]) Theoretical curve FINUDA proton spectra KEK  np  nnp strongly quenches the nucleon yields H. Bhang et al., EPJ A33 (2007) 259 normalization beyond 15 MeV (FINUDA data threshold)

Simonetta Marcello.Torino University JAEA-October NMWD proton spectra p-shell hypernuclei M.Agnello et al., PLB 685 (2010) 247 Background subtracted & acceptance corrected 5 Λ He 7 Λ Li 9 Λ Be 11 Λ B 15 Λ N 12 Λ C 13 Λ C 16 Λ O

A low A high  from fit 12  C FINUDA, PLB 685 (2010) 247 NMWD p gaussian fit free  A low : spectrum area below  1N + 2N + FSI A high : spectrum area above  1N + FSI 2N(>70 MeV) ~ 5% 2N tot G,Garbarino, A.Parreno and A.Ramos, Phys.Rev.Lett. 91 (2003) Phys.Rev. C 69 (2004) assumption W.Alberico and G.Garbarino, Phys. Rev. 369 (2002) 1 assumption  2N /  NMWD &  n /  p not depend on A 43 NMWD:  2N  N N  n N N

FSI &  NN contribution evaluation: systematics 44 5 Λ He 7 Λ Li 9 Λ Be 11 Λ B 15 Λ N 12 Λ C 13 Λ C 16 Λ O NMWD:  2N

FSI &  NN contribution evaluation A low = 0.5 N(  p  np) + N(  np  nnp) + N p FSI-low A high = 0.5 N(  p  np) + N p FSI-high N(  p  np) N(  np  nnp) = pp  np ≈ pp  2N  np :  pp :  nn = 0.83 : 0.12 : 0.04 E. Bauer and G.Garbarino, Nucl.Phys. A 828 (2009), 29. assumption N(  p  np) + A low + A high A low = 0.5 N(  p  np) + N(  np  nnp) + N p FSI-low N(  np  nnp) + N p FSI-low + N p FSI-high R = 45 NMWD:  2N A low A high  from fit 12  C

46 Rare Two-Body Non Mesonic Decays

Two body non mesonic decays of light hypernuclei Non-mesonic decays of light hypernuclei (A<12) are not the favoured decay channels Mesonic decays play a larger role Two-body non mesonic decay: large momentum transfer (Q Val ~170 MeV ) Unlikely to occur → rare events Expected branching ratios: at the level of 1.5% of all non-mesonic decays calculations for 4 Λ He  3 He n, p t, d d [Rayet Nuovo Cim. 42B (1968), 238] Very few and sparse observations Mainly from bubble chamber/emulsion experiments, for 4 Λ He Extremely poor statistics, a few events No 4 Λ He →pt A few 4 Λ He → 3 He n : 8-14% of all identified NM decays of 4 Λ He Corenmans et al. (1968), unpublished Block PRL 3(1959), 291 One 4 Λ He →dd event Block et al. (1960) One 5 Λ He →dt event Keyes et al. Nuovo Cimento (1976) 47

Light hypernuclei decays in FINUDA large angular coverage (~4π) Excellent particle identification for charged hadrons Good momentum resolution Capability to fully reconstruct the event topologies Set of several targets allowing the production of different hypernuclei and hypernuclear fragments 4 Λ He hyperfragments production, from all targets – 4 Λ He → d d d momentum: 570 MeV/c – 4 Λ He → p t p momentum: 508 MeV/c 5 Λ He hypernucleus formation –From 6 Li targets: K - 6 Li → 5 Λ He + p + π - (π - momentum: MeV/c) –From 7 Li targets: K - 7 Li → 5 Λ He + d + π - –NM two-body decay: 5 Λ He → d t d momentum: 597 MeV/c dE/dx p.id. TOF p.id. p t d d pt mips 48 4 Λ He → n 3 He Not detectable

4 Λ He → dd decays Expected event features: 2 deuteron tracks of 570 MeV/c Back-to-back deuteron tracks possible 4 Λ He formation π - for the formation of the 4 Λ He g.s. hypernucleus in 4 He target: p π =255 MeV/c d d π-π- Analyzed data: 954 pb -1, data taking 49 Forward d  p/p = 3% Backward d  p/p = 4%

4 Λ He → pt decays Lower threshold for triton detection in FINUDA: 550 MeV/c 508 MeV/c tritons cannot be observed ! Missing triton analysis one proton with momentum in the range ( ) MeV/c one high momentum π - Missing mass for the (A - 4 Λ He - p - π - ) system compatible with one (missing) triton + residual nucleus Missing mass for the (A - 4 Λ He - p - π - ) system compatible with one (missing) triton + residual nucleus Large background contribution from K - (np) → Σ - p: capture rate 1.62%/K - stop in 6 Li (NPA 775 (2006), 35) Stringent cuts to be applied on: secondary vertices π - π - impact parameter (rejection 79%) angular distributions (backward peaked) (pπ - ) invariant mass to reject  from conversion reactions 50

5 Λ He formation in FINUDA 5 Λ He formation in FINUDA clearly observed in 6 Li and 7 Li targets: peaks in the spectra in coincidence with a NM decay proton 5 Λ He formation: π - in the momentum band ( ) MeV/c K - 6 Li → 5 Λ He + p + π - 5 Λ He formation: π - in the momentum band ( ) MeV/c K - 7 Li → 5 Λ He + d + π - 6 Li 5 Λ He 7 Li 5 Λ He 7 Λ Li NPA804 (2008),

5 Λ He → dt decays No events with detected d+t coincidence Pion momentum in the selected bands granting hypernucleus formation Deuteron momentum in a band across 597 MeV/c ( MeV/c) Missing triton analysis Additional requirement: hit on the vertex detectors head-on with the deuteron with large energy release 52

Summary and Conclusions  FINUDA at DAFNE successfully collected ~ 1.2 fb -1 of K - stop on several nuclear targets in two different data taking Excellent tracking performance, PID and large acceptance Several reactions have been measured and studied in coincidence Good capabilities of FINUDA to detect events with well definite topologies  Systematic Study of the charged MWD channels of p-shell  Hypernuclei: 7 Λ Li, 9 Λ Be, 11 Λ B and 15 Λ N Pion spectra measured for the first time with magnetic analysis Shape of spectra compared with theoretical ones obtained with pion distorted wave calculations J  assignement of ground state: 1/2 + for 7 Λ Li, 5/2 + for 11 Λ B have been confirmed, 3/2 + for 15 Λ N g.s. assigned for the first time Measurement of Branching Ratios Γ   / Γ TOT and evalaution of Γ   / Γ Λ 53 Mesonic Weak decays

Summary and Conclusions  Measurement of the proton energy spectra from the NMWD of 5 Λ He, 7 Λ Li, 9 Λ Be, 11 Λ B, 12 Λ C, 13 Λ C, 15 Λ N, and 16 Λ O down to 15 MeV, never reached before, crucial for FSI and Three-body decay 5 Λ He spectrum compatible with previous Exp and Theoretical calculations 12 Λ C spectrum not compatible with Exp and Theoretical calculations First measurement of 7 Λ Li Evaluation of the FSI and the Two-Nucleon induced NMWD Γ 2N /Γ NMWD = (0.24 ± 0.10) smaller than previous Experiments  In spite of limited statistics FINUDA could observe very clean signatures of Rare NMWD events with almost no background. First measurement of the ratio dd/pt of the decay modes of 4 Λ He. First measurement of the BR ( 5 Λ He  dt) 54 Non-Mesonic Weak decays

55 The FINUDA Collaboration Bari University and INFN, Italy Brescia University and INFN, Italy KEK, Japan Kyoto University, Japan Laboratori Nazionali di Frascati INFN, Italy Pavia University and INFN, Italy RIKEN, Japan Seoul National University, Korea Shahid Beheshty University, Teheran, Iran Torino University and INFN, Italy Torino Polytechnic and INFN, Italy Trieste University and INFN, Italy TRIUMF, Vancouver, Canada Bari University and INFN, Italy Brescia University and INFN, Italy KEK, Japan Kyoto University, Japan Laboratori Nazionali di Frascati INFN, Italy Pavia University and INFN, Italy RIKEN, Japan Seoul National University, Korea Shahid Beheshty University, Teheran, Iran Torino University and INFN, Italy Torino Polytechnic and INFN, Italy Trieste University and INFN, Italy TRIUMF, Vancouver, Canada

56 The END