FINUDA: status of analysis and plans for next data taking 31st Meeting of the LNF Scientific Committee November 29, 2005 Monica Bertani , INFN Frascati
Outline • Status of the analysis and plans for next data taking (1fb1): • Deeply Bound Kaonic Nuclei • Hypernuclear physics • New targets choice • Hardware upgrades • Conclusions and prospects for next run
+ K Deeply Bound Kaonic nuclei:do they exist ?
- (S=-1) bound K-nucleus systems Do they exist? _ Crucially depends on shape of K-nucleus potential If found, they would provide fundamental data about K-N potential, L(1405),nuclear compressibility, chiral symmetry restoration, Kaon mass inside nuclear matter (strangeness condensation, neutron stars…), … Deeply bound kaonic nuclei YES (deep optical potential) Akaishi-Yamazaki [PLB535(2002)70; PRC 65 (2002) 044005], Kaiser et.al, [NPA594 (1995) 325] NO(shallow optical potential)small B & large G Schaffner-Bielich et.al[N.P. A669 (2000)], Ramos et.al [N.P. A671 (2000) 481], Cieply et.al [N.P. A696 (2001) 173]
_ Akaishi and Yamazaki predict deep K-nucleus optical potential Deeply bound K-nucleus systems K- + 3He _ K- + p MeV MeV r fm r fm 1 2 3 1 2 3 0 0 L(1405) -50 -50 S+p S+p ( ppnK-) ( ppK-) L+p L+p -200 -200 K- + pp MeV r fm -300 -300 1 2 0 -50 3 2 S+p H H -400 -400 K K L+p -200 -500 -500 -300 Experimentally visible Theoretical predictions , .... • Large binding Energy • Narrow width • Favored decay channel: YN closed channel S+p Λ(1405): doorway for the K-nucleus bound states? Akaishi, Yamazaki,PRC 65(2002)044005 PLB 535(2002)70
1) Missing mass spectroscopy • Measurement of the momentum of the monochromatic recoiling particle in a A(K-,N)X inclusive reactions • Search for the tri-baryon and generic many-body K- deeply bound states • With stopped K-:_ • E471, @KEK-PS • FINUDA @ DAΦNE • With in flight K-: • E930 @ BNL-AGS 2) Invariant mass spectroscopy • Based on the kaonic nuclear states feature of decaying into hyperons • (K-pp) → Λ + p • (K-pn) → Λ + n • (K-ppn) → Λ + d , Λ + (pn) • (K-ppnn) → Λ + t • (K-pppn) → Λ + 3He • Full reconstruction of decaying particles • The decay occurs at rest: angular correlation between the emitted particles • Emitted in opposite directions FINUDA @ DAΦNE FOPI @ GSI Methods for deeply bound K-nuclear states serches
FINUDA uses invariant- mass spectroscopy in light nuclei FINUDA first observation: Physical Review Letter 94, 212303 (2005) presenting here an update preliminary ! Back-to-back correlation of these decay modes are observed preliminary ! Some candidates of back-to-back L-d pair are found preliminary ! Deeply-bound kaonic nuclei in FINUDA • Missing mass method exploited: S0 state ?
First observations: the dibaryon . Evidences in FINUDA invariant mass method, 2004 data X(K-pp)→Λp -p p(Λ) ≈ 500 MeV/c p(p) ≈ 500 MeV/c p(-) ≈200 MeV/c
K-“pp” L+p Lpinv. Mass. p p- Step 2: inv. Mass of back-to-back L-p events Step 1: selection of L events; L-p angular correlation M = (2255 ± 9) MeV Yield ≈ 1%/stopped K- threshold 6 light nuclear targets used: 6Li,7Li,12C First observation of K-pp bound state in FINUDA Phys. Rev. Lett. 94 212303 (3 June 2005) First application of Invariant mass spectroscopy (K-stop, ppp-)
4-hits tracks only 3 & 4 hits tracks 703 entries 203 entries preliminary all 12C 7Li 6Li threshold threshold p-L inv. mass (GeV/c2) Phys. Rev. Lett. 94 212303 (3 June 2005) Update on K-pp analysis: high+low resolution tracks New pattern recognition including 3-hit tracks in order to make up for 1 missing hit detector higher acceptance With same set of 6 light nuclear targets (6Li,7Li,12C) increase of statistics, possible to distinguish different nuclei Consistent result
K-“pn” L+n Lninv. Mass. p p- threshold Search for theK-pn L+nsystem in FINUDA Invariant mass spectroscopy (K-stop, pnp-) preliminary back-to-back n selection tagging TOO EARLY TO SAY SOMETHING • not enough statistics (~100 events)
K-“pn” S-+p Spinv. Mass. n p- threshold Search for theK-pn S-+psystem in FINUDA Invariant mass spectroscopy (K-stop, pnp-) preliminary back-to-back - p selection - tagging no cuts pp>200MeV/c to reduce L decay contamination TOO EARLY TO SAY SOMETHING - not enough statistics (~100 events)
K-“ppn” L+ d L dinv. Mass. p p- Search for the strange tribaryonK-ppnsystem in FINUDA (1) Invariant mass spectroscopy (K-stop, dpp-) • In the same set of light targets (6Li,7Li,C12) • deuteron selection by energy deposit at OSIM and Time of flight • L invariant mass • L& dmust be back to back, high momentum • L d invariant mass in coincidence with p-
dE/dxdE/dx + TOF dE/dxdE/dx + TOF K-“ppn” L+ d p p- Search forthe strange tribaryonK-ppnsystem in FINUDA (2) d selection (p, p-, d coincidence) With dE/dx + TOF/track lenght : high S/N reduction, very low background left Very clean d and L peaks ! L invariant mass deuteron mass coincidence p-,p,d de/dx selection TOF selection (p -,p) inv mass (p -,p) inv mass
threshold comparison with previous observations: (next slide) KEK-PS E471 GSI-FOPI Search forthe strangeK-ppnsystem in FINUDA (3) L- d invariant mass (p -,p) inv. mass Cos(QLd) dE/dx + TOF dE/dx + TOF 6Li,7Li,12C targets (Ld) inv mass Ld inv. mass all selection cuts: 106<Lmass<1126 MeV/c2 Cos(QLd) < - 0.8 6Li 12C 7Li Still poor statistics (57 evts), need more!
KEK-E471 & FOPI-GSI experimental indications of the strange tribaryon K-ppn KEK-PS E471 miss. mass method Iwasaki et al, nucl-ex/0310018, Suzuki et al, Phys. Lett. B597 (2004) 263 GSI-FOPI inv. mass method preliminary, HPC2005 3 3.2 3.4 3.6 3.8 3 3 3.2 3.4 3.6 3.8 (Λ+d) inv. mass (GeV) 4He(K-stop,n) K-ppn [ S+(3140)] T=0,B =169 MeV M = (3140.5 +3.0-0.8±2.3) MeV Γ < 21.6 MeV , Main decay SNN Ni+Ni @ 1.93AGeV: Λ+d(Kppn) B=149MeV, M = (3159 ± 20)MeV G~(100± 50) MeV POOR SIGNAL/NOISE RATIO
KEK-E471 experimental indications of the strange tribaryon K-pnn KEK-PS E471 miss. mass method Iwasaki et al, nucl-ex/0310018, Suzuki et al, Phys. Lett. B597 (2004) 263 proton momentum (MeV/c) 4He(K-stop,p) K-pnn : Signal observed in the semi-inclusive proton momentum spectrum ~ 510 Mev/c, in coincidence with a fast p-, identified with the strange tribaryon S0(3115) : T=1,B =194 MeV , M = (3117.7 +3.8-2.0±0.9) MeV, Γ < 21.6 MeV(95%C.L.) , Main decay : SNN, Sd
??? 510MeV/c Tribaryon (K-pnn) search with the missing mass technique in FINUDA (1) Contributions from hyperfragment non-mesonic decays (i.e. 5Hep+n+t) • FINUDA looks for S0 signal: in the inclusive proton spectrum we observe a clear peak around 510 MeV • only in Li6, not in other targets. • 6Li behaves like a cluster of 4He-d: • Is it the same signal found by KEK-E471 due to the strange tribaryon S0(3115) on a “quasi-4He” substructure of 6Li ? • K-stop+4He (K-pnn)+p • the proton momentum should exhibit a peak at about 500MeV/c • Missing mass spectroscopy method PRELIMINARY inclusive proton momentum spectrum not acceptance corrected
p- momentum p momentum momentum p momentum PRELIMINARY Tribaryon (K-pnn) search with the missing mass technique in FINUDA (2) Study of semi-inclusive proton/pion spectra on 6Li (not acceptance corrected) : strong correlation of the 500 MeV/c protons with high momentum p- In the assumption: K-stop+4He (K-pnn)+p • Do the proton come from S0 formation and thepion from the its decay ? K-pnn –d – n p- NO ! p (p-) < 280 MeV/c ! WARNING ON MISSING MASS METHOD !!!! Selected with p > 260 MeV/c: Clear peak structure!
INSTEAD: BACKWARD CORRELATION OBSERVED BETWEEN PROTON AND PION! This does NOT look like a signal from S0 . Tribaryon (K-pnn) search with the missing mass technique in FINUDA (3) If we observe a proton from S0 formation and a pion from its decay: K-stop + 4He S0 (3115) + p S0 (3115)–NN we expect no strong angular correlation between proton and pion proton peak region: (p(p)=505-515MeV/c) +p(pi-) >260MeV/c
Tribaryon (K-pnn) search with the missing mass technique in FINUDA(4 ):objection to the interpretation of S0 production from an 4He cluster • Is the peak, observed in 6Li by FINUDA and in 4He by KEK-E471, simply due to the scattering on a quasi-deuteron ? • K- + d - + p ? • Proton momentum: 515 MeV/c • - momentum from - decay: 200-300 MeV/c • Quite significant formation branching ratio expected • Indications for a sizeable d-cluster presence from old exp. of pi- capture on 4He WARNING: a peak in missing mass methods can be misleading ! FINUDA will exploit both missing mass and invariant mass techniques and will give an answer with next data taking using also a D2O target
Deeply Bound Kaonic Nuclear states: yield estimation for next run [1fb-1]
Hypernuclear spectroscopy and Non Mesonic Weak Decays: status of the analysis and prospects for next run
Hypernuclear spectroscopy: 12LC[published] Result on 12LC (KEK E369) Resolution 1.45 MeV FWHM Production reaction: (p+,K+) First FINUDA result on 12LC : Resolution 1.29 MeV FWHM Production reaction: (K-stop, p-) FINUDA RESULTS PR C64(2001)044302 Phys. Lett. B 622(2005)35 Capture Rates for 12LC in FINUDA: #1 ground state: ~ (1.01 0.11)x10-3/K-stop #6 excited state: ~ (2.04 0.17 )x10-3/K-stop FINUDA has achieved better resolution than previous experiments
12C 27Al 51V 7Li FINUDA hypernuclear results: summary Preliminary! Hypernuclear capture rate/K-stop (integrated over the bound region) as a function of the mass number.
Li 7 : p- momentum and proton energy spectra FINUDA Proton spectra in the hypernucleus bound region in coincidence with a p- from hypernucleus formation. Pion momentum from 7Li formation. Evidence of ground state and first low lying state Np=90 proton energy p-momentum
C12 p- momentum spectra Pion momentum from 12LC • formation To increase statistics,no selection quality cuts on p-, bw+fw tracks, • b<0.3 cm to reduce bck from in flight S- decays Pion momentum from 12LC formation in coincidence with proton from decay 12LC : sL and pL clearly show up with better S/N. p-momentum (MeV/c)
KEK-PS E462/E508 [Okada et al, PLB597(2004)249] neutron (filled circle) and proton (open circle) C12 proton & neutron energy spectra Counts / 10 MeV) C12 neutron energy (MeV) C12 proton energy (MeV) FINUDA Proton and neutron spectra in coincidence with a p- from hypernucleus formation in the hypernucleus bound region (s L + p L) .
Non Mesonic Weak decays: yield estimation for next data taking [1fb-1]
New set of targets for next data taking New set of targets: 2x 6Li, 2x 7Li,2x 9Be, 13C, D2O Expected results with ~ 1 fb-1 • All the targets can be used for deeply bound kaonic states searches, (K-pp,K-pn) and A dependence can be studied. • FINUDA can give an answer to many open questions • 6Li,9Be are ad, aan clusters useful to investigate the strange tri-baryion systems • 9Be: high resolution and high statistics hypernuclear spectroscopy and weak decays (never done before) • D2O = (free d + Oxygen), to be compared with behavior of quasi “d” in 6Li • O: high resolution and high statistics hypernuclear spectroscopy and weak decays of 16O (poorly studied) • 7Li :the best known hypernucleus concerning spectroscopy, weak decays never measured • 13C: high resolution and high statistics hypernuclear spectroscopy, comparison with 12C , poorly known only with (K+,pi+).
New targets simulation [ with 1fb-1] Be9 16O expected hypernuclear momentum spectra from next set of new targets: Be9, C13, O16 assuming 0.4% FWHM momentum resolution 13C
New TOFINO in Frascati • New Tofino detector built at KEK by Japanese collaborators: • Use of Hamamatsu photomultipliers • 1.8 mm thickness vs 2.3 mm • is in Frascati, Astra lab. PMTs case TOFINO inner side The use of PM’s allows to reduce the thickness of the scintillator slabs (less energy loss) and to suitably modify the assembly geometry
The deeply bound kaonic nuclear states are still largely unexplored: the existence of such states is not experimentally established at the moment and there are different theoretical predictions. FINUDA in the next run with 1fb-1 will use nuclear targets that will proof or disproof the existence of such states. CONCLUSIONS • FINUDA in the first 3-month run has demonstrated its capability of performing world-class hypernuclearspectroscopy, and has explored a new field in the search for deeply bound kaonic nuclear states. • Simultaneously, FINUDA will continue the experimental hypernuclear physics program mainly focused on NMWD.