Update%20on%20Hypernuclear%20Spectroscopy%20in%20Hall%20A

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Update on Hypernuclear Spectroscopy in Hall A

• Hypernuclei A very quick introduction
• Electroproduction of hypernuclei
• The experimental Program at Jefferson Lab
• Update on the analysis of O and Be targets
• Update on the analysis of Elementary Production

Francesco Cusanno INFN Rome (Italy)
Armando Acha FIU (Miami FL)
Hall A Collaboration Meeting Jefferson Lab,
13-14 December 2007
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HYPERNUCLEI what they are

• Hypernuclei are bound states of nucleons with a
  strange baryon (Lambda hyperon). A hypernucleus
  is a laboratory to study nucleon-hyperon
  interaction (L-N interaction).
• Extension of physics on N-N interaction to
  system with S?0
• Internal nuclear shell are not
• Pauli-blocked for hyperons.

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Hypernuclei - historical background -
experimental techniques
1953 ? 1970 hypernuclear identification with
visualizing techniques emulsions, bubble
chambers
Elementary reaction on neutron
1970 ? Now Spectrometers at accelerators CER
N (up to 1980) BNL (K-, p-) and (K, p)
production methods KEK (K-, p-) and (K, p)
production methods
e.g.
gt 2000 Stopped kaons at DAFNE (FINUDA)
(K-stop, p-)
Elementary reaction on proton
gt 2000 The new electromagnetic way
HYPERNUCLEAR production with ELECTRON BEAM at
JLAB
e.g.
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What do we learn from hypernuclear spectroscopy
Hypernuclei and the L-N interaction
weak coupling model
(parent nucleus) (L hyperon)
(doublet state)
SL
SN
T
V
D
Each of the 5 radial integral (V, D, SL , SN, T)
can be phenomenologically determined from the
low lying level structure of p-shell hypernuclei
Low-lying levels of L Hypernuclei
Hypernuclear Fine Structure
SN
Split by LN spin dependent interaction
(A-1)
D
AL
, SL
, T
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ELECTROproduction of Hypernuclei

• Hypernuclear physics accesses information on the
  nature of the force between nucleons and strange
  baryons, i.e. the L-N interaction. The nucleus
  provides a unique laboratory for studying such
  interaction.
• The characteristics of the Jefferson Lab.
  electron beam, together with those of the
  experimental equipments, offer a unique
  opportunity to study hypernuclear spectroscopy
  via electromagnetic induced reactions. A new
  experimental approach alternative to the
  hadronic induced reactions studied so far.
• The experimental program at Jefferson Lab, in
  Hall A and in Hall C, has completed its first
  part of measurements, performing high-resolution
  hypernuclear spectroscopy on light (p-shell) and
  medium heavy targets
• Different approach
• Hall C Low Luminosity (thin targets low
  current) Large Acceptance
• Hall A Small Acceptance - High Luminosity

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JLAB Hall A Experiment E94-107
E94107 COLLABORATION
A.Acha, H.Breuer, C.C.Chang, E.Cisbani,
F.Cusanno, C.J.DeJager, R. De Leo, R.Feuerbach,
S.Frullani, F.Garibaldi, D.Higinbotham,
M.Iodice, L.Lagamba, J.LeRose, P.Markowitz,
S.Marrone, R.Michaels, Y.Qiang, B.Reitz,
G.M.Urciuoli, B.Wojtsekhowski, and the Hall A
Collaboration

• Ebeam 4.016, 3.777, 3.656 GeV
• Pe 1.80, 1.57, 1.44 GeV/c Pk 1.96
  GeV/c
• qe qK 6
• W ? 2.2 GeV Q2 0.07 (GeV/c)2
• Beam current lt100 mA Target thickness 100
  mg/cm2
• Counting Rates 0.1 10 counts/peak/hour

16O(e,eK)16?N 12C(e,eK)12?? ?Be(e,eK)9?Li H(
e,eK)???0
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Results on 12C target
Analysis of the reaction 12C(e,eK)12BL
Results published M.Iodice et al., Phys. Rev.
Lett. E052501, 99 (2007).
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Results on 12C target Hypernuclear Spectrum of
12BL
Narrowest peak is doublet at 10.93 MeV ?
experiment resolution lt 700 keV
G.S. width is 1150 keV an unresolved
doublet? What would separation be between two 670
keV peaks? ? 650 keV (theory predicts only
140)
670 keV FWHM
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Results from the 9Be target
(very preliminary)
Analysis of the reaction 9Be(e,eK)9LiL
Red line Benhold-Mart (K MAID) Blue line Saghai
Saclay-Lyon (SLA) Curves are normalized on g.s.
peak.
Black line Millener wave function
Counts / 200 keV
Counts / 200 keV
Missing energy (MeV)
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Results from the 9Be target
(very preliminary)
Analysis of the reaction 9Be(e,eK)9LiL
Counts
Missing energy (MeV)
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Preliminary Results on the WATERFALL target
Analysis of the reaction 16O(e,eK)16NL
and 1H(e,eK)L (elementary reaction)
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the WATERFALL target provides 16O and H targets
H2O foil
Be windows
H2O foil
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Preliminary Results on the WATERFALL target - 16O
and H spectra
1H (e,eK)L
1H (e,eK)L,S
L
Energy Calibration Run
S
16O(e,eK)16NL
Nb/sr2 GeV MeV
Excitation Energy (MeV)

• Water thickness from elastic cross section on H
• Fine determination of the particle momenta and
  beam energy
• using the Lambda peak reconstruction (resolution
  vs position)

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Results on 16O target Hypernuclear Spectrum of
16NL
- Peak Search Identified 4 regions with excess
counts above background

• Fit to the data Fit 4 regions with 4 Voigt
  functions ? c2/ndf 1.19
• Theoretical model superimposed curve based on
• SLA p(e,eK)? (elementary process)
• ?N interaction fixed parameters from KEK and BNL
  16?O spectra

Binding Energy BL13.660.25 MeV Measured for the
first time with this level of accuracy (ambiguous
interpretation from emulsion data interaction
involving L production on n more difficult to
normalize)
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Results on 16O target Hypernuclear Spectrum of
16NL
2 O. Hashimoto, H. Tamura, Part Nucl Phys 57,
564 (2006) 3 private communication from D.
H. Davis, D. N. Dovee, fit of data from Phys
Lett B 79, 157 (1978) 4 private
communication from H. Tamura, erratum on Prog
Theor Phys Suppl 117, 1 (1994)
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E94-107
(K-,p-)
(K-,p-)
(p,K)
Difference expected 400 500 keV
Comparison with the mirror nucleus 16OL
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Results on H target The p(e,eK)L Cross Section
Work on normalizations, acceptances, efficiencies
still underway
p(e,e'K)L on Waterfall Production run
p(e,e'K)L on LH2 Cryo Target Calibration run
Expected data from the Proposal E07-012 to study
the angular dependence of p(e,eK)L and
16O(e,eK)16NL at Low Q2 approved January, 2007