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 Hall A Collaboration Meeting Jefferson Lab, December 2007 Francesco Cusanno INFN Rome (Italy) Armando Acha FIU (Miami FL)

H YPERNUCLEI …what they are H ypernuclei are bound states of nucleons with a strange baryon (Lambda hyperon). A hypernucleus is a laboratory to study nucleon-hyperon interaction ( -N interaction). Extension of physics on N-N interaction to system with S0 Internal nuclear shell are not Pauli-blocked for hyperons.

: hypernuclear identification with visualizing techniques emulsions, bubble chambers 1970 Now : Spectrometers at accelerators: CERN (up to 1980) BNL : (K -, - ) and (K +, + ) production methods KEK : (K -, - ) and (K +, + ) production methods > 2000 : Stopped kaons at DA NE (FINUDA) : (K - stop, - ) > 2000 : The new electromagnetic way : HYPERNUCLEAR production with ELECTRON BEAM at JLAB Elementary reaction on neutron : e.g. Elementary reaction on proton : e.g. H ypernuclei - historical background - experimental techniques Production of MIRROR hypernuclei : I=0, q=0 n = p Spectroscopy of mirror hypernuclei reveal n p 0 mixing and N-N coupling

What do we learn from hypernuclear spectroscopy H ypernuclei and the -N interaction weak coupling model (parent nucleus) ( hyperon) (doublet state) S SNSN T (A-1) A SNSN, S, T Split by N spin dependent interaction Hypernuclear Fine Structure Low-lying levels of Hypernuclei Each of the 5 radial integral (V,, S, S N, T) can be phenomenologically determined from the low lying level structure of p-shell hypernuclei V

E LECTROproduction of H ypernuclei Hypernuclear physics accesses information on the nature of the force between nucleons and strange baryons, i.e. the -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

J LAB Hall A Experiment E O(e,eK + ) 16 N 12 C(e,eK + ) C(e,eK + ) 12 Be(e,eK + ) 9 Li Be(e,eK + ) 9 Li H(e,eK + ) 0 E beam = 4.016, 3.777, GeV P e = 1.80, 1.57, 1.44 GeV/c P k = 1.96 GeV/c e = K = 6° W 2.2 GeV Q 2 ~ 0.07 (GeV/c) 2 Beam current : <100 A Target thickness : ~100 mg/cm 2 Counting Rates ~ 0.1 – 10 counts/peak/hour 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 E C OLLABORATION

R esults on 12 C target Analysis of the reaction 12 C(e,eK) 12 B Results published: M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007).

R esults on 12 C target – Hypernuclear Spectrum of 12 B G.S. width is 1150 keV; an unresolved doublet? What would separation be between two 670 keV peaks? ~650 keV (theory predicts only 140) Narrowest peak is doublet at MeV experiment resolution < 700 keV 670 keV FWHM

R esults from the 9 Be target Analysis of the reaction 9 Be(e,eK) 9 Li (very preliminary) Counts / 200 keV Missing energy (MeV) Counts / 200 keV Red line: Benhold-Mart (K MAID) Blue line: Saghai Saclay-Lyon (SLA) Curves are normalized on g.s. peak. Black line: Millener wave function

R esults from the 9 Be target Analysis of the reaction 9 Be(e,eK) 9 Li (very preliminary) Missing energy (MeV) Counts

Preliminary R esults on the WATERFALL target Analysis of the reaction 16 O(e,eK) 16 N and 1 H(e,eK) (elementary reaction)

Be windows H 2 O foil WATERFALL the WATERFALL target: provides 16 O and H targets

1 H (e,eK) 16 O(e,eK) 16 N 1 H (e,eK) Energy Calibration Run Preliminary R esults on the WATERFALL target - 16 O and H spectra Excitation Energy (MeV) Nb/sr2 GeV 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)

Fit to the data: Fit 4 regions with 4 Voigt functions 2 /ndf = 1.19 Theoretical model superimposed curve based on : i)SLA p(e,eK+) (elementary process) ii) N interaction fixed parameters from KEK and BNL 16 O spectra R esults on 16 O target – Hypernuclear Spectrum of 16 N - Peak Search : Identified 4 regions with excess counts above background Binding Energy B =13.66±0.25 MeV Measured for the first time with this level of accuracy (ambiguous interpretation from emulsion data; interaction involving production on n more difficult to normalize)

R esults on 16 O target – Hypernuclear Spectrum of 16 N E ( +,K + ) (K -, - ) [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) [2] [3] [4] Comparison with the mirror nucleus 16 O Difference expected: 400 – 500 keV

p(e,e'K + ) on Waterfall Production run p(e,e'K + ) on LH2 Cryo Target Calibration run Work on normalizations, acceptances, efficiencies still underway Expected data from the Proposal E to study the angular dependence of p(e,eK) and 16 O(e,eK) 16 N at Low Q 2 approved January, 2007 R esults on H target – The p(e,eK) C ross S ection