International Conference on Hypernuclear XIand Strange Particle Physics

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1 International Conference on Hypernuclear XIand Strange Particle Physics The first observation of a neutron rich hypernucleus, ΛH M. Danysz and J. Pniewski, Philosophical Magazine 44, 348 (1953) Elena Botta INFN-Torino and Torino University 1

2 International Conference on Hypernuclear XIand Strange Particle Physics Overview M. Danysz and J. Pniewski, Philosophical Magazine 44, 348 (1953) Conference Topics physics motivations n-rich hypernuclei search with FINUDA Λ H 2

3 Search for light n-rich hypernuclei physics motivations Hypernuclei with a large neutron excess: R.H. Dalitz, R. Levi Setti., N. Cim. 30 (193) 489, L. Majling, NP A 585 (1995) 211c, Y. Akaishi et al., Frascati Physics Series XVI (1999) 59. The Pauli principle does not apply to the Λ inside the nucleus + extra binding energy ( glue-like role) a larger number of neutrons can be bound with respect to ordinary nuclei. Neutron drip-line: response of neutron halo on embedding of Λ hyperon, hypernuclear species with unstable nuclear core, extending the neutron drip line beyond the standard limits of n-rich nuclei Hypernuclear physics: ΛN interactions at low densities, the rôle of 3-body forces nuclear core compression ( 7 ΛLi vs Li: H.Tamura et al., Phys.Rev. Lett. 84 (2000) 593) FINUDA physics program: PLB 40 (200) 145: upper limits Λ H, 7 Λ H and 12 Λ Be PRL 108 (2012) , NPA 881 (2012) 29: Λ H observation 3

4 Hypernuclear e + + e - φ (1020) K + + K - (127 MeV/c) K - stop + A Z A Λ Z + π- A Λ Z A (Z+1) + π - Γ π A Λ Z A-2 (Z-1) + p + n A Λ Z A-3 (Z-1) + p + n + n MWD 1N induced Γ p Spectroscopy 2N induced Γ np NMWD - very thin targets ( g/cm 2 ) transparency high resolution spectroscopy - different targets in the same run high degree of flexibility - coincidence measurement with large acceptance (ΔΩ 2π srad) complete event decay mode study (S. Bufalino talk) - simultaneous tracking of µ + from the K + decay K + µ + ν µ energy and rate calibration FINUDA key features 4

5 Search for light n-rich hypernuclei Production reactions (K - stop, π+ ) K - + p Λ + π 0 π 0 + p n + π + (2-step) S-EX + C-EX K - + p K 0 + n K 0 + p Λ + π + (2-step) C-EX + S-EX K - + p Σ + π + Σ + p n + Λ (1-step) S-EX K.Kubota et al, NPA 02 (199) Λ He ( 9 Be) U.L.= /K - stop ; 12 Λ Be(12 C) U.L.= /K - stop ; 1 Λ C( 1 O) U.L.= /K - stop T.Y.Tretyakova et al., Nucl. Phys. A 91 (2001) 51c ( /K - stop ) M. Agnello et al. Phys. Lett. B 40 (200) 145 Λ H ( Li) U.L.= (2.5 ± 1.4) 10-5 /K - stop; 7 ΛH( 7 Li) U.L.= (4.5± 1.4) 10-5 /K - s; 12 Λ Be( 12 C) U.L.= (2.0 ± 0.4) 10-5 /K - stop (π -, K + ) π - + p π 0 + n π 0 + p Λ + K + (2-step) C-EX + AP π - + p K 0 + Λ K 0 + p n + K + (2-step) AP + C-EX π - + p K + + Σ - Σ - + p n + Λ (1-step) AP P.K.Saha et al., PRL 94 (2005) : 10 Λ Li (10 B) dσ/dω = 11.3±1.9 nb/sr T.Y.Tretyakova et al., Phys. At. Nucl. (2003) 151 5

6 Λ H and 7 ΛH ( 12 ΛBe) search with FINUDA M.Agnello et al., PLB 40 (200) 145 oct jan 04: ~220 pb -1 background: K - + p Σ + + π - K - + pp Σ + + n Σ + n π + Σ + n π + cut on K - /π + distance K - stop + Li Λ H + π+ K - stop + 7 Li 7 ΛH + π + raw inclusive spectrum background subtracted spectrum R ( ΛH) U.L.= (2.5 ± 1.4) 10-5 /K - stop 90% C.L.

Coincidence measurement + nov 200 - jun 2007: 90 pb -1 K - stop + Li Λ H +

+ x,y,z resolution + K + tagging) " p, K, p, d, P.ID.

7 Coincidence measurement + nov jun 2007: 90 pb -1 K - stop + Li Λ H + π+ Λ H He + π - D-CEX ~252 MeV/c MWD ~134 MeV/c Detector capabilities: " Selective trigger based on fast scint. detectors " precise K - vertex identification (~ 1 mm 3 ) (P.ID.+ x,y,z resolution + K + tagging) " p, K, p, d, P.ID. (OSIM and LMDC de/dx) " High momentum resolution FWHM MeV/c, % FWHM MeV/c (tracker resolution + He bag + thin targets) B = 1T π - π + 7

8 Coincidence measurement K - stop + Li Λ H + π+ Λ H He + π - (τ( He)~801 ms) if ΛH is a stable system independent 2-body reactions: decay at rest M(K - ) + 3 M(n) + 3M(p) B( Li) = M( Λ H) + T( Λ H) + M(π+ ) + T(π + ) M( ΛH) = 4 M(n) + 2M(p) B( He) + T( He) + M(π - ) + T(π - ) M 2 ( He) + p 2 (π ) M( He) T(π + ) + T(π - ) = M(K - ) + M(p) M(n) B( Li) + B( He) T( He) T( ΛH) M(π + ) M(π - ) = ± 1.3 MeV ( MeV with B Λ = 0 MeV) M 2 ( Λ H) + p2 (π + ) M( Λ H) M( ΛH) = M( 5 H) + M(Λ) B(Λ) cut on T(π + ) + T(π - ): MeV 8

9 counts/1 MeV selection: T(π + )+T(π - ) = MeV T + T! -! + (MeV) Finuda Coll. and A. Gal, NPA 881 (2012) 29. absolute energy scale: µ+(235. MeV/c) from K µ2 Δ p < 0.12 MeV/c systematic errors π-(132.8 MeV/c) from 4 ΛH σt sys = 0.17 MeV Δ p < 0.2 MeV/c momentum (MeV/c)! σt (π+) = 0.9 MeV, σt (π ) = 0.84 MeV σt exp = 1.3 MeV σt = 1.3 MeV ! momentum (MeV/c) 9

10 MeV/c (σ p = 1.1 MeV/c) MeV/c (σ p = 1.2 MeV/c) Finuda Coll. and A. Gal, NPA 881 (2012) 29. blue bars: p π+/π selection regions including ΛH lowest particle stability threshold 4 Λ H+2n (p π+ =251.9 MeV/c, p π =135. MeV/c) B Λ =1.5 MeV counts/1 MeV/c candidate events K - stop events counts/1 MeV/c ! + momentum (MeV/c) ! momentum (MeV/c) 10

250 255 MeV/c (σ p = 1.1 MeV/c) 130 137 MeV/c (σ p = 1.2 MeV/c) Finuda 5 H + Λ Coll. and A. Gal, NPA 881 (2012) 29. 0.0 MeV 3 H + 2n + Λ -1.

11 MeV/c (σ p = 1.1 MeV/c) MeV/c (σ p = 1.2 MeV/c) Finuda 5 H + Λ Coll. and A. Gal, NPA 881 (2012) MeV 3 H + 2n + Λ -1.7 MeV blue bars: p π+/π selection regions including ΛH lowest particle stability threshold 4 Λ H+2n (p π+ =251.9 MeV/c, 4 p π =135. Λ H + MeV/c) 2n B Λ = MeV counts/1 MeV/c candidate events K - stop events counts/1 MeV/c ! + momentum (MeV/c) ! momentum (MeV/c) 11

12 T(π + )+T(π - ) cut : systematics T(π + )+T(π - ) = MeV T(π + )+T(π - ) = MeV momentum (MeV/c) momentum (MeV/c) ! + 220! ! momentum (MeV/c) ! momentum (MeV/c) 12

Λ H/K - stop production rate Background sources: fake coincidences: π+(249 255 MeV/c) & π - (130 138 MeV/c) 0.27±0.27 ev.

13 Λ H/K - stop production rate Background sources: fake coincidences: π+( MeV/c) & π - ( MeV/c) 0.27±0.27 ev. K - stop + Li Σ + + π He + n n + π + (end point ~190 MeV/c) (end point ~282 MeV/c) 0.1±0.07 ev. K - stop + Li 4 ΛH + n + n + π + (end point ~252MeV/c) 4 He + π - (p(π - ) = 133 MeV/c) negligible Λ H/K - stop production rate Total background: BGD1 + BGD2 = 0.43 ± 0.28 events on Li Poisson statistics: 3 events DO NOT belong to pure background: C.L.= 99% R * BR(π-) = (3 BGD1 BGD2) / [ε(π-) ε(π+) (n. K - stop on Li)] R * BR(π-) = (2.9 ± 2.0) 10 - /K - stop H. Tamura, et al., PRC 40 (1989) R479 BR(π ) 4 Λ H = 0.49 R = (5.9 ± 4.0) 10 - /K - stop (2.5 ± ) 10-5 /K - stop Agnello et al., PLB 4(200) 145 FINUDA Coll. and A. Gal, PRL 108 (2012) , NPA 881 (2012) 29 13

14 first evidence of ΛH based on 3 events that cannot be attributed to pure instrumental and physical background kinematics T tot (MeV) p(π + ) (MeV/c) p(π - ) (MeV/c) M( Λ H) formation (MeV/c 2 ) M( Λ H) decay (MeV/c 2 ) ΔM ( Λ H) (MeV) 202.5± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±1.28 FINUDA Coll. and A. Gal, PRL 108 (2012) , NPA 881 (2012) 29 B Λ determination formation decay mass difference 14

(N+Y)/Z=5 Λ H binding energy Dalitz et al., N. Cim. 30 (193) 489 (binding energy 4.2 MeV) L. Majling, NPA 585 (1995) 211c - binding energy - prod. rate ~ 10-2 * hyp. prod. rate in (K - stop, π- ) 4.

15 (N+Y)/Z=5 Λ H binding energy Dalitz et al., N. Cim. 30 (193) 489 (binding energy 4.2 MeV) L. Majling, NPA 585 (1995) 211c - binding energy - prod. rate ~ 10-2 * hyp. prod. rate in (K - stop, π- ) 4.2 MeV Y. Akaishi et al., AIP Conf. Proc (2008) 277 K.S. Myint, et al., Few Body Sys. Suppl. 12 (2000) 383 Y. Akaishi et al., Frascati Phys. Series XVI (1999) MeV coherent Λ Σ coupling in 0+ states ΛNN three body force: B ΛNN = 1.4 MeV, ΔE(0 + g.s. 1 + ) = 2.4 MeV model originally developed for 4 ΛH and 4 ΛHe 15

16 B Λ ( ΛH) determination mass mean value = ±1.1 B Λ = 4.0±1.1 MeV ( 5 He + Λ) B Λ = 5.8 MeV ( 5 He + Λ) ΛNN force: 1.4 MeV 5 H +! MeV [2] 3 H + 2n +! B Λ interval 4 H + n + n MeV! [1] Dalitz, Majling 0 MeV MeV (0 + ) Akaishi [3] H! formation decay = 0.98±0.74 MeV excitation spectrum of ΛH 1

17 formation decay M interpretation Spin flip is forbidden in production at rest: K stop + Li (L i =0, S=1) Λ H(L f, S=1) + π+ L f = 0 Λ H(1+ exc. ) followed by : (i) Λ H(1+exc.) γ + Λ H(0+g.s.) ( s) (ii) Λ H(0+g.s.) π + He(0+g.s.) ( s) M1 B Λ ( ΛH) = (4.5 ± 1.2) MeV vs 5 He+Λ from decay mass only little neutron-excess effect compared to B Λ ( ΛHe) = (4.18 ± 0.10) MeV The excitation energy of the 1 + spin-flip state is identified with a systematic M = 0.98 ± 0.74 MeV between values of ΛH mass derived separately from production and from decay. M is consistent with the 1.04 MeV for the analogous spin-flip excitation in 4 ΛH, according to shell-model estimates. ΔE( g.s.) = 2.4 MeV from ΛNN three body force calculations. An experiment to produce Λ H via the (π, K+) reaction on Li at 1.2 GeV/c was approved at J-PARC (E10) and should run soon. The expected energy resolution is 2.5 MeV FWHM, and the expected statistics is about 1 2 orders 17 of magnitude higher than previous KEK experiments.

He + 3n 8 He+Λ 4.9 7! He + 2n 3.1 + + 3/2, 5/2 3.9 8!

18 9 Λ He search with FINUDA (N+Y)/Z = 3.5 stable nuclear core n-halo ! He + 4n! He + 3n 8 He+Λ 4.9 7! He + 2n /2, 5/ ! He + n 5 MeV 0.0 (MeV) 9! He + 1/2 Majling, NPA 585 (1995) 211c binding energy = 8.5 MeV 10 MeV 18

19 9 Λ He search with FINUDA K - stop + 9 Be 9 ΛHe + π+ 9 Λ He 9 Li + π - (τ( 9 Li)~178 ms) independent 2-body reactions: decay at rest M(K - ) + 5 M(n) + 4 M(p) B( 9 Be) = M( 9 Λ He) + T(9 Λ He) + M(π+ ) + T(π + ) M( 9 Λ He) = M(n) + 3M(p) B(9 Li) + T( 9 Li) + M(π - ) + T(π - ) Preliminary M 2 ( 9 Li) + p 2 (π ) M( 9 Li) M 2 ( 9 Λ He) + p2 (π + ) M( 9 Λ He) M( 9 ΛHe) = M( 8 He) + M(Λ) B(Λ) T(π + ) + T(π - ) = M(K - ) + M(p) M(n) B( 9 Be) + B( 9 Li) T( 9 Li) T( 9 ΛHe) M(π + ) M(π - ) = ± 1.3 MeV ( MeV with B Λ = 0 10 MeV) cut on T(π + ) + T(π - ): MeV 19

20 counts/1 MeV selection: T(π + )+T(π - ) = MeV T(! + ) + T(! ) (MeV) momentum (MeV/c)! ! momentum (MeV/c)

21 momentum (MeV/c)! B Λ ~ 3.5 MeV MeV/c (σ p = 1.1 MeV/c) MeV/c (σ p = 1.2 MeV/c) B Λ = 5 10 MeV 200 B Λ ~ 1 MeV ! momentum (MeV/c) Preliminary counts/(1 MeV/c) counts/(1 MeV/c) ! + momentum (MeV/c) 0 21 momentum (MeV/c) !

22 9 Λ He/K - stop production rate upper limit evaluation 0 observed events ε(π ), ε(π+) n. K - stop on 9 Be ( K - stop events) Preliminary R * BR(π-) < (2.3±1.9) 10 - / (n. K - stop on 9 Be) (90% C.L.) BR(π-) = 0.323± ( 5 ΛHe + 4 spectator neutrons) M.Agnello et al., PLB 81 (2009) 139. Γ( 9 Λ He gs 9 Li gs + π - ) = 0.21 Γ Λ from A. Gal, Nucl. Phys. A 828, 72 (2009) R < / (n. K - stop on 9 Be) (90% C.L.) R < / (n. K - stop on 9 Be) (90% C.L.) submitted to PRC K.Kubota et al, NPA 02 (199) Λ He ( 9 Be) U.L.= /K - stop 22

23 Conclusions (K - stop, π + ) production rate vs A R (/K-stopped) * Λ H 7 Λ H Λ He 12 Λ Be 1 Λ C Preliminary FINUDA: inclusive spectra FINUDA: coincidence KEK full bars: U.L., 90% C.L. 2 1 theoretical calculations are welcome! E. Hiyama A J-PARC (E10): Λ H and 9 Λ He 23 23

24 24

25 Li Λ He Λ H Λ Li ( 5 ΛHe+p) 25

26 coincidence method limits target hypernucleus 2-b MWD daughter nucleus lifetime MWD model MWD model BR(π ) Li Λ H He 801 ms 4 Λ H 0.49 H. Tamura, et al., PRC 40 (1989) R479 7 Li 7 Λ H 7 He unstable 4 Λ H 0.49 H. Tamura, et al., PRC 40 (1989) R479 9 Be 9 Λ He 9 Li 178 ms 5 Λ He FINUDA PLB 81 (2009) see A. Gal, Nucl. Phys. A 828, 72 (2009) 12 C 12 Λ Be 12 B 20 ms 9 Λ Be FINUDA PLB 81 (2009) C 13 Λ Be 13 B 17.3 ms 9 Λ Be FINUDA PLB 81 (2009) O 1 Λ C 1 N 7.13 s 12 Λ C Y.Sato et al., PRC 71 (2005)

27 FINUDA low momentum π resolution: production of 4 Λ H hyperfragment on Li counts/(0.25 MeV/c) ! momentum (MeV/c) µ = 132.±0.1 MeV/c σ = 1.2±0.1 MeV/c χ 2 /ndf = 79.1/74 FINUDA π+ momentum resolution (235 MeV/c): K µ2 decay (PLB 98 (2011) 219) 27

28 Background sources: Σ+ production and decay K - stop + Li Σ + + π He + n n + π + quasi free approach: ± body interaction: ± He + n and 5 He final state counts/1 MeV T(! + ) + T(! ) (MeV) Finuda Coll. and A. Gal, NPA 881 (2012)

29 Background sources [π+( MeV/c) & π - ( MeV/c)]: K - stop + Li 4 Λ H + n + n + π+ (end point ~252MeV/c) 4 He + π - (p(π - ) = 133 MeV/c) negligible (2.8±0.5) 10-8 K - stop + Li Σ Λ H + d + π- n + π + (p(π - ) < 15 MeV/c) (p(π + ) < 250 MeV/c) K - stop + Li 3 ΛH + 3n + π+ (p(π + ) < 242 MeV/c) 3 He + π - (p(π - ) ~ 115 MeV/c) K - stop + Li Λ + 3 H + 2n + π + p + π - (p(π + ) < 247 MeV/c) (p(π - ) < 195 MeV/c) K - stop + Li ΛHe + π0 (p(π 0 ) ~ 280 MeV/c) Li + π - (p(π - ) ~ 108 MeV/c) π 0 + Li He + π + (p(π + ) ~ 280 MeV/c forw. dir.) 29

30 The FINUDA detector Magnet yoke B = 1.0 T Magnet end-cap Outer scintillator barrel 72 slabs (TOFONE) e + Detector capabilities: " Selective trigger based on fast scintillation detectors (TOFINO, TOFONE) " precise K - vertex identification (~ 1 mm 3 ) (ISIM P.ID.+ x,y,z resolution + K + tagging) " p, K, p, d, P.ID. (OSIM and LMDC de/dx) " High momentum resolution ( FWHM for MeV/c for spectroscopy) (1% FWHM for MeV/c for decay study) e - (% FWHM for MeV/c for decay study) (2% FWHM for MeV/c for decay study) Mechanical support (clepsydra) For: " 2424 Straw Tubes (longitudinal + stereo) " 1 Low-Mass Drift Chambers (LMDC) " 18 µ-strip vertex detectors (ISIM/OSIM) " Inner scintillator barrel 12 slabs (TOFINO) " 8 Targets Superconducting Coil Simultaneous study of formation and decay of strange hadronic systems by full event reconstruction (tracker resolution + He bag + thin targets) " Neutron detection TOF (TOFONE-TOFINO) Apparatus designed for a typical collider experiment: " Cylindrical geometry " large solid angle (~ 2π sr) " multi-tracks analysis 30

31 connected fields: astrophysics n-stars: essential inputs from hypernuclear physics Y in neutron stars first exotic species (N, e, µ) in n-star core; strongly interacting matter: Λ ~ 2n 0, Σ ~ n 0 (repulsive), Ξ ~ 4-5 n 0 (attractive?) YN, YY interaction; short range repulsion of BB ΛNN for YN for additional stability to n-star (Pauli blocking) Cooling on n-star: Y-URCA process volume emission of ν by slow modified-urca processes: N+p+e - N+n+ν e and N+n N+p+e - +ν e (p p +p e p n, charge neutrality: n p /n 11%, n 1.5 n 0 ) Y-URCA direct process: Λ p+e - +ν e no n threshold, no charge neutrality fast cooling, critical n-star mass, suppressed by YY int. strength, Y superfluidity. Maximum n-star mass, mass-radius relation Y appearence lowers overall Fermi energy and momentum of B and l total system n lowers softening of equation of state stiffness of hadronic e.o.s. above 2.5 n 0 controls maximum n-star mass repulsive YY interaction is needed ΛNN forces to increase maximum mass (M obs =1.44 solar-mass for Hulse-Taylor pulsar, 2-solar mass NS (PSR J ) recently observed). Gravitational wave emission rotating n-stars can emit gravitational waves due to the r-mode instability which is controlled by the viscosity of dense matter; NMWDs in dense medium control the bulk viscosity NMWD rates knowledge needed S. Balberg and A. Gal, Nucl. Phys. A 25 (1997) 435. J. Schaffner-Bielich, Nucl. Phys. A 804 (2008) 309, Nucl. Phys. A 835 (2010) 279. S. Tsuruta, Astroph. Jou. 571 (2002) L

32 connected fields: astrophysics n-stars: essential inputs from hypernuclear physics (Vidana talk) Y in neutron stars: composition first exotic species (N, e, µ) in n-star core; strongly interacting matter: Λ ~ 2n 0, Σ ~ n 0 (repulsive), Ξ ~ 3 n 0 (attractive?) YN interaction; short range repulsion of ΛNN for additional stability to n-star (Pauli blocking) Cooling of n-star: Y-URCA process Maximum n-star mass, mass-radius relation stiffness of hadronic e.o.s. above 2.5 n 0 controls maximum n-star mass repulsive YN interaction is needed ΛNN forces to increase maximum mass (M obs =1.44 solar-mass for Hulse-Taylor pulsar, 2-solar mass NS (PSR J ) recently observed). Gravitational wave emission S. Balberg and A. Gal, Nucl. Phys. A 25 (1997) 435. J. Schaffner-Bielich, Nucl. Phys. A 804 (2008) 309, Nucl. Phys. A 835 (2010) 279. S. Tsuruta, Astroph. Jou. 571 (2002) L

Observation of neutron-rich -hypernuclei by the FINUDA experiment

International Symposium on Strangeness Nuclear Physics 2014 December 12 nd -14 th, 2014, ChangSha, China Observation of neutron-rich -hypernuclei by the FINUDA experiment Alessandro Feliciello I.N.F.N.