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The FINUDA experiment: a new powerful laboratory for studies of strangeness in nuclear matter

The FINUDA experiment: a new powerful laboratory for studies of strangeness in nuclear matter. on behalf of the FINUDA Collaboration: Bari University and I.N.F.N., Italy Brescia University, Italy KEK , Tsukuba, Ibaraki, Japan LNF ( Laboratori Nazionali di Frascati) / I.N.F.N., Italy

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The FINUDA experiment: a new powerful laboratory for studies of strangeness in nuclear matter

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  1. The FINUDA experiment:a new powerful laboratory for studies of strangeness in nuclear matter • on behalf of the FINUDA Collaboration: • Bari University and I.N.F.N., Italy • Brescia University, Italy • KEK, Tsukuba, Ibaraki, Japan • LNF (Laboratori Nazionali diFrascati) /I.N.F.N., Italy • Pavia University and I.N.F.N., Italy • RIKEN, Wako, Saitama, Japan • Seoul National University, South Korea • Teheran Shahid Beheshty University, Iran • Tokyo University, Japan • Torino University, Polytechnic and I.N.F.N., Italy • Trieste University and I.N.F.N., Italy • TRIUMF, Vancouver, Canada Maurizio Palomba Physics Department of Bari University and I.N.F.N. Bari, Italy PANIC05 XVIIth Particles And Nuclei International Conference Santa Fe, NM, United States - October 24th-28th, 2005

  2. The FINUDA experiment • @ DAFNE collider • Detector description • and performance • Physics program • Data analysis and results • from the first data taking: • Hypernuclear spectroscopy • Search for neutron-rich hypernuclei • Search for deeply bound K-nucleus states • Conclusions and future • developments Outline M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  3. FINUDA FINUDA: Fisica NUcleare a DAFNE The very first example of a (hyper)nuclear physics fixed-target experiment carried on at a collider (DAFNE@ LNF) Optimized to produce hypernucleiALZ in a completely new way DAFNE: Double Annulare+-e- F-factory for Nice Experiments M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  4. K+ K- (49%) • Intense source • of K+K- pairs: • Monochromatic • with low energy • (T ~ 16 MeV, • p~ 127 MeV/c) • Collinear • and tagged • Hadronic • background free • → “clean” low- • energy K- beam K0S K0L (34%) e+e- f(1020) r p (13%) • The p- is tracked in the detector • p- momentum → • → ALZhypernucleus energy level Hypernuclei production in FINUDA • DAFNEis a high-luminosity F-factory • 2003-2004 data taking: • L ~ 5 · 1031 cm-2s-1:~ 250 f mesons / s • to be increased of a factor ~ 10 with the • next machine upgrade • K-’s are stopped inside • thin targets (~ 0.2  0.3 g cm-2): • 26Li,7Li,312C,27Al,51V • Strangeness exchange reaction • on target nuclei: • K-stop + AZ→ALZ+p- M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  5. Outer scintillator barrel – 72 slabs (TOFONE) Magnet yoke B = 1.0 T Magnet end-cap e+ Super- conducting Coil • Mechanical support (clepsydra) • For: • 2424 Straw Tubes (longitudinal + stereo) • 16 Low-Mass Drift Chambers • 18 m-strip vertex detectors (ISIM/OSIM) • Inner scintillator barrel – 12 slabs (TOFINO) • 8 Targets e- Simultaneous study offormationanddecayof strange hadronic systems byfull event reconstruction The FINUDA detector • Detector capabilities: • Selective triggerbased on fast scintilla- • tion detectors (TOFINO, TOFONE) • CleanK-vertexidentification • (ISIM P.ID.+x,y,zresolution + K+ tagging) • p, K, p, d, … P.ID. (OSIM dE/dx) • High momentum resolution(6‰ FWHM) • (tracker resolution + He bag + thin targets) • Neutron detection (TOFONE) • Time-Of-Flight (TOFONE-TOFINO) • Apparatus designed for a typical collider experiment: • Cylindrical geometry • large solid angle (~ 3p sr) • multi-tracking analysis M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  6. 4-Baryons NLNN • weak interaction • DI = 1/2 rule Low-energyNY stronginteraction • Neutron-rich L hypernuclei • S hypernuclei • Deeply-bound kaonic nuclei Hypernuclear spectroscopy Hypernuclear weak decay p n n n p L p p p n n p • Impurity nuclear physics: • L“glue-like” role • Changes in nuclear • size and shape • … • NY potentials • SP nuclearmodels • Many-body dynamics • Bound states with S0 Quark degrees of freedom in nuclear medium FINUDA: a new opportunity to investigate strange nuclear matter M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  7. E369 @ KEK: FINUDA @ DAFNE: DBL 1.45 MeV FWHM (p+ , K+) reaction DBL 1.29 MeV FWHM (K-stop, p-) reaction PRC 64(2001) 044302 PLB 622(2005) 35 Hypernuclear spectroscopy • First results on12LChypernucleus (first 2003-2004 data taking): very good agreement with the best previously published ones (6 peaks fit) M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  8. FINUDA @ DAFNE: DBL 1.29 MeV FWHM (K-stop, p-) reaction #6 #5 9.34 #4 PLB 622(2005) 35 #3 #2 #1 Peaks #4 and #5 could be explained as |11C; J+›|1sL› states, in an extended shell model including inter-shell couplings [T. Motoba, NP A 639 (1998) 135c] Hypernuclear spectroscopy (2) • A better fit may be obtained taking into accounta seventh peak(#5in the figure) → a new hypernuclear state found on 12LC ? M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  9. Search for neutron-rich hypernuclei • Hypernuclei with a large neutron excess • Their existence has been theoretically predicted (L. Majling, NP A 585 (1995) 211c) butnot experimentally observed yet • Study of the hypernuclear structureproperties (size, shape, …) at very high N/Z; • Feedback with the astrophy-sics field: phenomena related to high-density nuclear matter in neutron stars • The Pauli principle does not apply to the L • inside the nucleus • A larger number of neutrons may occupy the bound nuclear levels • extra binding energy(L “glue-like” role) M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  10. Reaction mechanisms: • Double charge exchange: • K-+ p → L+ p0 ; p0 + p → n + p+ • Strangeness exchange & S-L coupling: • K-+ p → S-+ p+ (S-+ p ↔ L+ n) • In FINUDA we are searching for: 12LBe (N/Z = 7/4) from 12C(K-stop, p+)12LBe 6LH (N/Z = 4) from 6Li(K-stop, p+)6LH 7LH (N/Z = 5) from 7Li(K-stop, p+)7LH • DQ (NUCLEUS) = -2 • p+in the final state • Event selection: • Reconstruction of a p+ with a momentum • value in the hypernucleus bound region • P.ID. Made using dE/dx from OSIM • and TOF from TOFINO & TOFONE p+ K- K+ Neutron-rich production in FINUDA M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  11. L. Majling, NP A 585 (1995) 211c Expected BL for the ground state FINUDA preliminary Y. Akaishi, Frascati Phys. Series, Vol. XVI (1999) 59 L. Majling, NP A 585 (1995) 211c Data analysis and preliminary results • Two independent normalization methods used to convert the count numbers to a NRH production rate (work in progress) • Statistical analysis to estimate the background contribution in the spectra Regions of interest width = ±2s with respect to the BL central value M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  12. Discrete nuclear bound states of K in few-body nuclear systems with S = -1 • Theoretical models in favour of their observation: • Akaishi & Yamazaki, PLB535 (2002) 70; Akaishi & Yamazaki, PRC65 (2002) 044005 • Kaiser et al., NP A594 (1995) 325 • Deep K-nucleus optical potential: • strongly I = 0 attractive interaction→ “deeply” bound K-nucleus states • K N (I=0) →S +  channel energetically closed • L +  decay forbidden (isospin conservation) • Large binding energies (B ~ 100 MeV); small widths (G~ 50 MeV)  detectable • Theoretical models against their observation: • Schaffner-Bielich et al., NP A 669 (2000); Ramos et al., NP A 671 (2000) 481 • Cieply et.al, NP A 696 (2001) 173; Oset & Toki, arXiv:nucl-th/0509048 v1 (2005) • Shallow K-nucleus optical potential: small B,large G values Search for bound K-nucleus states M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  13. Invariant mass spectroscopy • Based on the kaonic nuclear states feature of decaying into hyperons: • 2KH ( K-pp) → L+ p • with subsequent L decay: L→ p + p- • Full reconstruction of decay events and • involved particles • (p p-) selection @ L invariant mass • Selection of events with back-to-backL-p Search methods for deeply bound K states FINUDA @ DAFNE FOPI @ GSI E471, E549 @ KEK-PS FINUDA @ DAFNE (with stopped K-)_ E930 @ BNL-AGS E548 @ KEK-PS (with in-flight K-) • Missing mass spectroscopy • Measurement of the momentum of the monochromatic recoiling particle in AZ(K-stop, N)X inclusive reactions M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  14. Events excess observed below the 2p + K- mass threshold @ 2.37 GeV/c2 • Possible mechanisms explaining the enhancement: • Two-nucleons absorption← (expected near the threshold) • K- + (pp)  Y* N  + p •  0 + p + p +  (74 MeV) • Kaon bound state formation • K- + (pp)  (K-pp)  + p • 0 + p+ p+ (74 MeV) 2 protons absorption 2mp+mK- FINUDA Coll. PRL 94(2005) 212303 fit region Acceptance- corrected M = 22559 MeV/c2 B = 115+6-5(stat)+3-4(sys) MeV G = 67+14-11(stat)+2-3(sys) MeV Yield ≈ 10-3 / K-stop Invariant mass method: results on 6Li to know more about this analysis please see the Dr. Fujioka poster on Tuesday 25 M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

  15. Summary, conclusions and prospects • FINUDA is the very first collider experiment for studying hypernuclear physics and strangeness in nuclear matter • First data taking ended in march 2004: • Some interesting results on strangeness nuclear physics already found • Data analysis still in progress • Next data taking scheduled in the middle of 2006 • Future prospects (after 2006): • DAFNE luminosity upgrade (~ 5·1032 cm-2s-1 foreseen) • and data taking at higher statistics • FINUDA upgrade and hypernuclear physics at high energy resolution: • study of hypernuclei spin-orbit and spin-spin fine structures M. PalombaPANIC05XVII Particles And Nuclei International Conference Santa Fe, NM - October 24-28, 2005

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