Tullio Bressani

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Status and Perspectivesof the Physics
Programwith the FINUDA Apparatus
Tullio Bressani NuPECC Meeting Venezia, March
18-19, 2005
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The FINUDA Collaboration

• Bari University and I.N.F.N. Bari
• Brescia University and I.N.F.N. Pavia
• KEK
• L.N.F. / I.N.F.N. Frascati
• Pavia University and I.N.F.N. Pavia
• RIKEN
• Seoul National University
• Teheran Shahid Beheshty University
• Torino University and I.N.F.N. Torino
• Torino Polytechnic and I.N.F.N. Torino
• Trieste University and I.N.F.N. Trieste
• TRIUMF

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Outline

• the FINUDA experiment
• the physics program
• the apparatus
• the results
• hypernuclear spectroscopy
• Kaon deeply-bound state K-pp
• search for neutron-rich hypernuclei
• hypernucleus (rare) decays
• 3) future plans

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Physics output (S-1)
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FINUDA _at_ DAFNE
energy 510 MeV
luminosity 5 1032 cm-2 s-1
sx (rms) 2.11 mm
sy (rms) 0.021 mm
sz (rms) 35 mm
bunch length 30 mm
crossing angle 12.5 mrad
frequency (max) 368.25 MHz
bunch/ring up to 120
part./bunch 8.9 1010
current/ring 5.2 A (max)
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FINUDA _at_ DAFNE
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FINUDA _at_ DAFNE
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FINUDA detectors performances

• s.c. solenoid B 1.0 T field homogeneity
  within 2

• interaction/target region K/K- identification,
  hypernucleus production and detection

ISIM/OSIM sz 30 µm ?E 20 FWHM TOFin st
250 ps

• tracking devices measurement of trajectories and
  momenta of charged particles (?p/p 3.5)

LMDC s(?, f) 150 µm sz 1 wire length STB
s(?, f) 150 µm sz 500 µm

• external scintillator barrel trigger and neutron
  detection

TOFout st 500 ps FWHM efficiency 10 ?E
8 MeV

• He chamber minimization of particle multiple
  scattering

?p/p He atmosphere 3.5 air 2
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K / K identification
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FINUDA key features

• very thin nuclear targets (0.1 0.3 g/cm2)

• coincidence measurement with large acceptance

• irradiation of different targets in the same run

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FINUDA first run

• 14-Oct-2003 to 22-Mar-2004
• 250 pb-1 delivered to IP2
• 33 pb-1 machine tuning
• 10 pb-1 FINUDA debugging
• 190 pb-1 useful data taking

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Bhabha event
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The typical event
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Target envelope by K - stopping points
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K / K - stopping points
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Improvement in momentum resolution
?p/p 0.4
?p/p 0.6
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K- 12C ? p- X inclusive spectra
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Background reactions p - spectrum
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K- 12C ? p X inclusive spectrum
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12C (raw) excitation spectrum
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FINUDA vs. KEK-E369
DE 1.3 MeV FWHM
DE 1.5 MeV FWHM
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12C excitation spectrum
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K-pp state theoretical calculations
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Kaonic nuclei search with ? tagging

• Missing-mass spectroscopy
• Example
• A kaonic nucleus emits a hyperon in its decay.
• Invariant-mass spectroscopy
• Example

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? momentum distribution and back-to-back
correlations
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K-pp deeply bound state
Contribution from S0p decay are seen in low mass
region
No other background exists !
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FINUDA vs. KEK-E471
6Li
7Li
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neutron-rich hypernuclei

• 2 production mechanisms
• strangeness double charge exchange
• K- p ? ? p0
• ?? p0 p ? n p
• p- p ? p0 n
• ?? p0 p ? K ?
• Strangeness exchange with ?-S coupling
• K- p ? S- p
• ?? S- p ? ? n
• p- p ? S- K
• ?? S- p ? ? n

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neutron-rich hypernuclei
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Upper limit for NRH formation probabilty
PNRH UPPER LIMIT ( 10-5) 90 C.L. 90 C.L. 2 s C. L. 2 s C. L. 3 s C.L. 3 s C.L.
PNRH UPPER LIMIT ( 10-5) dE/dx PID dE/dx TOF PID dE/dx PID dE/dx TOF PID dE/dx PID dE/dx TOF PID
Present Momentum Resolution (0.9) 2.6 3.5 4.9 2.1 2.9 4.3 3.2 4.3 6.1 2.6 3.6 5.3 4.9 6.6 9.4 4.0 5.6 8.3 12LBe 6LH 7LH
Nominal Momentum Resolution (0.35) 1.6 2.1 3.3 1.3 1.8 2.8 2.0 2.6 4.1 1.6 2.2 3.5 3.1 4.1 6.5 2.5 3.5 5.6 12LBe 6LH 7LH
PRELIMINARY
KEK result for 12LBe 6.110-5 (90 C.L., no
error given)
new results
Uncertainties dominated by the error on the m
time gate efficiency (? 10)
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(rare) decay
K- 6Li ? p-
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d d (rare) decay
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d d (rare) decay
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Summary

• First data taking period successfully carried out
  (30 106 events on tape)
• Preliminary and partial results on spectroscopy
  are competitive with world
  published data
• Observation of K-pp bound state
• Experimental upper limit for the NRH production
• better than published one for ?12Be
• measured for the first time for ?6H and ?7H
• First observation of?4He non mesonic (rare) decay

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Short term plans

• Next data-taking period scheduled in 2006
• ( 1 fb-1 ? statistics 5)
• effort focused on light-medium targets (6Li, 7Li,
  9Be, 16O)
• Increase by a factor 4 of the DAQ rate
• Replacement of the internal TOF detector (KEK)
• Improvement of the reconstruction program
• geometrical alignment
• detector calibration
• pattern recognition strategy
• selection criteria
• Further data-taking period (hopefully) in
  2007/2008

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Long term plans
FINUDA2 _at_ DAFNE2
L 1034 cm-2s-1
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Ge detectors in magnetic field _at_ GSI