Experimental hypernuclear physics

Transcription

1 Experimental hypernuclear physics p n n p n n p p Λ p p n Alessandro Feliciello I.N.F.N. - Sezione di Torino

2 Outline strangeness nuclear physics: interest discovery potential experimental results high resolution spectroscopy decay modes neutron-rich hypernuclei deeply bound K-nucleus states future prospects: facilities experiments 2

3 Single Λ-hypernucleus production A hypernucleus is is the outcome of of a genic engineering manipulation applied to to the nuclear physics domain 1) strangeness exchange (both in flight and at rest): K π + A + Z Z + A Z A Λ A Λ Z + π 2) associated strangeness production: 3) electro-production : e + K A ' + + Z e + K + Λ A + ( Z 1) 3

4 quality vs. quantity quality vs. quantity energy resolution interaction rate spectromer performance low cross section beam intensities apparatus acceptance (~100 msr) targ thickness (g/cm 2 ) 4

5 Experimental technique improvement 1996 ΔE ΔE ~ MeV MeV FWHM FWHM T. T. Hasegawa Hasegawa Rev. Rev. C C (1996) (1996) C(π C(π + +,K,K + + ) ) 12 Λ 12C 5 years C targ: 0.9 g/cm 2 ΔE ΔE ~ MeV MeV FWHM FWHM H. H. Hotchi Hotchi Rev. Rev. C C (2001) (2001)

6 Physics output (S = -1) nuclear nuclear models models spectroscopy spectroscopy low-energy low-energy N -Y -Y interaction interaction neutron neutron rich rich Λ-hypernuclei Λ-hypernuclei medium medium effect effect n p p n n p p n Λ p p n deeply deeply bound bound KK states states (weak) (weak) decay decay 4B 4B weak weak interaction interaction quark quark substructures substructures 6

7 Physics output (S=-2) nuclear nuclear models models spectroscopy spectroscopy low-energy low-energy Y-Y Y-Y interaction interaction strangels strangels p Λ n n Λ p double double deeply deeply bound bound KK states states H dibaryon dibaryon existence existence (weak) (weak) decay decay S=-2 S=-2 system system g.s. g.s. H particle particle mass mass 27

8 S=-2 systems S = -2-2systems study is is not not just justa simple extension of of what has has been done for for S = -1-1system new physics items: a dailed and consistent understanding of the quark aspect of the baryon-baryon forces in the SU(3) space will not be possible as long as experimental information on the YY channel is not available search for H particle existence of S = -2 (deeply) bound K states experimental challenges: (abundant) production of ΛΛ-hypernuclei is very difficult identification of produced hyperfragments is problematic γ-ray measurement in coincidence 28

9 A. Feliciello / 7th European Research Conference Electromagnic Interactions with Nucleons and Nuclei, Milos Island, Greece, September 12-15, Hypernuclei s Hypernuclei s chart chart 29

10 Hypernuclei s chart 2 Hypernuclei s chart 2 in preparation in preparation compled compled ~ running ~ running running running running running in preparation in preparation compled compled 38

11 Hall A E results on B Λ 12 I e- : 100 μa 12 C targ: 100 mg/cm 2 Septa nearly nearly no no background! background! M. M. Iodice Iodice Rev. Rev. Lt. Lt (2007) (2007) theory theory best best fit fit ΔE ΔE ~ MeV MeV FWHM FWHM 39

12 41 Hall C E results E results L. Tang Nucl. A 790 (2007) 679c L. Tang Nucl. A 790 (2007) 679c 1.5 T I e- : μa ΔΩ: ~16 msr targs: 100 mg/cm 2 ΔE ~ 0.75 MeV FWHM ΔE ~ 0.75 MeV FWHM lightest observed n-rich hypernucleus

13 DAΦNE energy 510 MeV luminosity cm -2 s -1 σ x (rms) σ y (rms) σ z (rms) bunch length crossing angle frequency (max) 2.11 mm mm 35 mm 30 mm 12.5 mrad MHz bunch/ring up to 120 part./bunch current/ring 5.2 A (max) A Z Λ e Κ + e stop + + φ Κ A A Z Z A Λ Z Κ + + π ( Z + 1) + π ( A 2) ( A 2) + n + n 43 ( Z 1) + p + n

14 12 C 12 C FINUDA 1 st st round 6 Li 6 Li 51 V 2003/2004 Φsup 27 Al boost 7 Li 12 C doorway for for light light systems 4 (( H 4,, He 5,, He) Λ Λ Λ He) medium-a systems (~ (~ terra terra incognita) reference nuclide never never studied before before 48

15 Capture rate/0.25 MeV x FINUDA vs. KEK-E C(K C(K K - stop -,π,π - ) - ) 12 Λ 12 C ΔE ΔE ~ MeV MeV FWHM FWHM ΔΩ: > 2π sr 12 C targ: 0.2 g/cm 2 M. M. Agnello Agnello Lt. Lt. B B (2005) (2005) a) #1 #2 #3 # #5 B Λ (MeV) #6 H. H. Hotchi Hotchi Rev. Rev. C C (2001) (2001) C(π C(π + +,K,K + + ) ) 12 Λ 12C ΔE ΔE ~ MeV MeV FWHM FWHM ΔΩ: ~100 msr 12 C targ: 0.9 g/cm 2 49

16 FINUDA results on 12 C FINUDA results on 12 C 50 - stop C(K C(K K - -,π,π - ) - ) 12 Λ 12 C ΔE ~ 1.3 MeV FWHM ΔE ~ 1.3 MeV FWHM M. #5 b) M. Agnello Agnello Lt. Lt. B B (2005) (2005) a) 0.4 #6 0.3 #6 #1 0.2 #1 0.1 #2 #2 #3 #4 #3 #7 #5 #4 B Λ (MeV) Capture rate/0.25 MeV x

17 π The typical event The typical event μ + π Φ Κ + Κ μ + 51

18 - FINUDA results on 7 Li 7 7 Li(K Li(K - -,π,π - ) - ) 12 7 stop Λ 12 Li C background backgroundprocess giving giving π - - following following K - - absorption absorption on on 7 7 Li Li K - (N N ) Σ - N Σ - n π - K - n Λπ - K - μ - ν μ in flight ΔE ΔE ~ MeV MeV FWHM FWHM M. M. Ukai Ukai Rev. Rev. C C (2006) (2006) ?? M. M. Jurić Jurić Nucl. Nucl. Rev. Rev. B B (1973) (1973) 1 1 spin-flip amplitude 0 1/2 + 5/2 + 53

19 Hypernuclear capture rates Hypernuclear capture rates 12 C 59

20 12 CΛ non-mesonic decay 12 CΛ non-mesonic decay π π momentum momentum raw raw spectrum spectrum p dected in coincidence main background: K - (np) Σ - p Σ - n π - 61

21 12 12 C Λ non-mesonic decay real realdata MC MCdata Γ p = p (0.41± (0.41± 0.15) 0.15) Γ Λ Λ FINUDA data data SKS SKS data data S. S. Okada Okada Lt. Lt. B B (2004) (2004)

22 events events with with two two positive positivracks tracks from from 6 6 Li Li targs targs with with momentum momentum > MeV/c MeV/c μ + 4 He Λ d + d (rare) decay π - interesting interestingevents events to to be be recognized recognized p d candidates candidates 64 azimuthal angle difference accurate backtracking and kinematic analysis needed

23 d 4 HeΛ d + d (rare) decay 4 HeΛ d + d (rare) decay d d Φ d Κ Κ + 65

24 neutron-rich hypernuclei neutron-rich hypernuclei 2 production mechanisms: 1) strangeness + double charge exchange K - + p Λ+ π 0 π 0 + p n + π + two step processes! π - + p π 0 + n π 0 + p K + + Λ 2) strangeness exchange with Λ-Σ coupling K - + p Σ - + π + Σ - + p Λ+ n π - + p Σ - + K + Σ - + p Λ+ n 12 C 68

25 K K K stop stop stop FINUDA results on NRH 12 + C Be + π 12 Λ 6 + Li H + π 6 Λ 7 + Li H + π 7 Λ p p p + = MeV / c ± π σ p π M. M. Kubota Kubota Nucl. Nucl. A A (1996) (1996) = MeV / c ± π σ p π + = MeV / c ± π σ p π M. M. Agnello Agnello Lt. Lt. B B (2006) (2006)

26 FINUDA search for B=2 kaon-nuclear states FINUDA search for B=2 kaon-nuclear states FWHM 6 MeV m Λ ±5 MeV 83

27 FINUDA search for B=2 kaon-nuclear states FINUDA search for B=2 kaon-nuclear states 6 Li 7 Li acceptance acceptance corrected corrected 12 C (2m (2mp p + m mk) k ) threshold threshold M. Agnello Rev. Lt. 94 (2005) M. Agnello Rev. Lt. 94 (2005)

28 1 8 FINUDA 2 nd round FINUDA 2 nd round 2 3 boost /2007 sup very preliminary very preliminary best best suited suited for for Κ nuclear states states O 2 2 targ targ K + + charge exchange reaction on on D 2 2 spectroscopy spectroscopy

29 Last FINUDA results on 7 Li Last FINUDA results on 7 Li 275 MeV/c p dected in coincidence 92 not not acceptance acceptance corrected corrected

30 Last FINUDA results on 6 Li Last FINUDA results on 6 Li 275 MeV/c p dected in coincidence 93 not not acceptance acceptance corrected corrected

31 The role of γ ray spectroscopy The role of γ ray spectroscopy H. Tamura 94

32 A look to the future A look to the future Z e A ' + + Z e + K + Λ A ( MWPC Fibers 1 ToF ) 96

33 A look to the future A look to the future 97

34 A look to the future A look to the future Geomrical acceptance reduced to to 82% 82% straw tubes straw tubes HPGe dectors HPGe dectors targs and μstrip dectors targs and μstrip dectors drift chambers scintillator barrel drift chambers scintillator barrel 99

35 The hyper-triple cluster concept design The hyper-triple cluster concept design 106 JRA6 X COOLER II, AMETEC, ORTEC mechanical design thermal studies

36 A look to the future A look to the future 107

37 A look to the future A look to the future top view top view side view side view 108

38 Summary The fifty-year-old field of strangeness nuclear physics is still alive and has a great discovery potential number of exp. physicist involved is growing significant theorical effort, well tuned on exp. data dedicated beams and apparatus main item in several future physics program at new facilities 109

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