Recent results from the Hall C hypernuclear program Recent results from the Hall C hypernuclear program - JLab E Osamu Hashimoto Tohoku University HYP2006 Mainz, October 11-14, 2006

E hypernuclear collaboration – –Y. Fujii, O. Hashimoto (Spokesperson), D. Honda, M. Kaneta, F. Kato, D. Kawama, A. Matsumura, N. Maruyama,T. Miyoshi, S.N. Nakamura (Spokesperson), H. Nomura, K.Nonaka,A. Ohtani, Y. Okayasu, M. Sumihama, H. Tamura (Tohoku U) – –S. Kato (Yamagata U) – –T. Takahashi, Y. Sato, H. Noumi (KEK) – –O.K. Baker, M. Christy, L. Cole, P. Gueye, C. Keppel, L. Tang (Spokesperson), L. Yuan (Hampton U) – –B. Beckford, S. Gullon, P. Markowitz, J. Reinhold (Spokesperson), C. Vega (FlU) – –Ed.V. Hungerford, K. Lan, N. Elhayari, N. Klantrains, Y. Li,S. Radeniya, Murad, V. Rodrigues (Houston) – –R. Carlini, R. Ent, H. Fenker, T. Horn, D. Mack, G. Smith, W. Vulcan, S.A. Wood, C. Yan (JLab) – –N. Simicevic, S. Wells (Louisiana Tech) – –L. Gan (North Carolina, Wilmington) – –A. Ahmidouch, S. Danagoulian, A. Gasparian (North Carolina A&T) – –M. Elaasar (New Orleans) – –R. Asaturyan, H. Mkrtchyan, A. Margaryan, S. Stepanyan, V. Tadevosyan (Yerevan) – –D. Androic, T. Petkovic, M. Planinic, M. Furic, T. Seva (Zagreb) – –T. Angelescu (Bucharest) – –V.P. Likhachev (Sao Paulo) – –M. Ahmed (Duke) – –B. Hu, Y. Song, C. Yang (Lanzhou)

1989 The first hypernuclear experiment in 1989 The first hypernuclear experiment in Hall C, E89-009, approved 1994 Hypernuclear experiment in 1994 Hypernuclear experiment in Hall A, E94-107, approved 1995 JLab started physics experiments 1997 Hall C 2 nd generation experiment, E97-008, approved, later updated as E The first (e,e’K + ) hypernuclear spectroscopy, E89-009, carried out High resolution kaon spectrometer (HKS) for the E experiment under construction Hypernuclear experiment in Hall A, E94-107, carried out Hypernuclear experiment in Hall A, E94-107, carried out The second generation experiment in Hall C, E01-011, carried out The 3 rd generation hypernuclear experiment in Hall C, E05-115, approved New electron spectrometer for the 3 rd generation experiment, E05-115, New electron spectrometer for the 3 rd generation experiment, E05-115, under construction under construction 2008 The E experiment will be ready for beam in Hall C 2008 The E experiment will be ready for beam in Hall C ( Nue Nakamura’s Talk ) (e,e’K + ) hypernuclear spectroscopy at JLab

12 C(  +,K + ) 12  C spectra by the SKS spectrometer at KEK 12 GeV PS KEK336 2 MeV(FWHM) KEK E MeV(FWHM) Hypernuclear spectroscopy established BNL 3 MeV(FWHM) SKS Mass resolution and yield limited

Hypernuclear investigation Mean field aspects of nuclear matter Mean field aspects of nuclear matter –A baryon deep inside a nucleus distinguishable as a baryon ?  N interaction  N interaction –Flavor SU(3) –  mixing or the three-body interaction New form of nuclei New form of nuclei Spectroscopy in the wide mass range High resolution and High yield rate

 Single particle states  Single particle states ->  -nuclear potential ->  -nuclear potential  hyperon in a heavier nucleus  Single-particle orbits in a nucleus E140a at KEK Hotchi et al., PRC 64 (2001) Hasegawa et. al., PRC 53 (1996)1210KEK E140a Skyrme HF (Yamamoto) DDRH (Lenske) Quark-meson coupling (Saito, Thomas) ……… YLaPb Si

Hypernuclear spectroscopy Reaction spectroscopy  -ray spectroscopy Resolution > 1.5 MeV with meson beams so far Applicable to all hypernuclear states Mass, cross sections, angular distributions, polarization …. Each reaction populates characteristic states Resolution as good as a few keV Applicable to the states below nucleon emission thresholds Angular distribution, lifetime, branching ratios … Powerful for spin dependent interaction Complimentary Better resolution required Higher yield required

B  =0  Hypernuclear production (  +,K ＋ ) Stopped (K -,  ) (e,e’K+) ( ,K ＋ ) (p,K ＋ ) Inflight(K -,  ) Hypernuclear Cross section Momentum transfer (MeV/c) mb/sr nb/sr  b/sr JLab KEK, BNL BNL, CERN (K -,  - ) (  +,K + )

Expansion of hypernuclear chart by the (e,e ’ K + ) reaction Mirror symmetric hypernuclei A : to be studied by the (e,e ’ K+) reaction ( ppnp 57(2006) )

Basic characteristics of (e,e ’ K + ) spectroscopy Proton converted to   Neutron rich  hypernuclei Proton converted to   Neutron rich  hypernuclei Large angular momentum transfer  Similarly to (  +,K + ) reaction Large angular momentum transfer  Similarly to (  +,K + ) reaction Spin-flip amplitude  Unnatural parity hypernuclear states Spin-flip amplitude  Unnatural parity hypernuclear states Sub MeV resolution  High quality primary beam Sub MeV resolution  High quality primary beam Small thin target ( even enriched targets ) Small thin target ( even enriched targets )  High quality primary beam  High quality primary beam

E and E01-011

K + detection At very forward angle (~ 0 degrees) Maximum hypernuclear production cross section e’ detection = tag virtual photon energy and emission angle At extremely forward angles Advantage : Large virtual photon flux Disadvantage : Huge backgrounds from Bremsstrahlung Kinematics of the (e,e ’ K + ) reaction in Hall C p e =0.3GeV/c e’ K+K+ p K =1.2 GeV/c E e =1.8 GeV e - Beam Target nucleus E  =1.5 GeV σ total (  b) E γ (GeV) p( ,K + )  Total cross section Phys. Lett. B 445, 20 (1998) M. Q. Tran et al.

Kaon Angular Distribution Angle (deg) d  /d  (nb/sr) Electron Angular Distribution Angular distributions of scattered electrons and kaons Sotona

The first (e,e ’ K + ) spectroscopy experiment (JLab E89-009) E e = 1.7,1.8 GeV  = E  = 1.5 GeV p K = 1.2 GeV  e = 0 degrees  k = 0-7 degrees Electron spectrometer --- Enge split pole Kaon Spectrometer --- SOS (Short Orbit Spectrometer) Splitter magnet 0 degree tagging geometry SOS

152 nb/sr 12  B spectrum of E Ground state doublet B  = 11.4 ± 0.5 MeV Cross section 140±17(stat) ±18(sys) nb/sr Motoba’s calculation Binding energy Emulsion data B  = MeV d  /d  nb/sr/0.3 MeV -B  (MeV) (2+,3+)(1-,2-) (1-,0-) (2-,1-) ~ 750 keV(FWHM) 292 hrs 0.66  A T. Miyoshi et al., Phy. Rev. Lett. 90, (2003) J  cross section

What limited the E experiment ? Hypernuclear yield rate Hypernuclear yield rate –High accidental background rate due to Brems electrons limited luminosity –Kaon solid angle limited detection efficiency Energy resolution Energy resolution –The kaon arm limited hypernuclear mass resolution (1) A high-resolution large-solid-angle kaon spectrometer (HKS) (2) New experimental configuration “Tilt method”

Maximum momentum 1.2 GeV/c Dispersion 4.7 cm/% Momentum resolution 2 x (FWHM) Solid angle 30 msr w/o splitter 16 msr w splitter Momentum acceptance 12.5 % The HKS spectrometer system for E (2) Tilt method for the electron arm (1) High resolution Kaon Spectrometer (HKS)

K+K+ e’ E setup in Hall C ENGE HKS Electron beam To beam dump From upstream Splitter Electron beam e’ K+K+ To beam dump

Kinematical regions of electrons and kaons 12  B gr band Real data

HKS detectors HKS exit p,K +,  +,e +

Time of flight w/ cherenkov cut p K   tof –  K After cherenkov cut

Tilt method The electron spectrometer (ENGE) vertically tilted by 8 degree e’ 8 degree --- Normal to the dispersive plane of the splitter magnet --- Higher luminosityHigher hadron rates

Expected singles rates Target HKSENGE e + (kHz)  + (kHz) K + (kHz)p(kHz) e - (kHz)  - (kHz) 12 C , Si , V , E C 12 C <1 Hz ,000- SOSENGE I e = 30  A, 100 mg/cm 2 High rejection efficiencies against pions and protons are required Measured values at E I e = 0.66  A, 22 mg/cm 2 Greater hadron rates

Beam currents, singles rates & trigger rates TargetTargetThickness (mg/cm 2 ) Beam current (  A) Hadron singles rate (kHz) electron singles rate (kHz) COIN Trigger rate (kHz) CH 2 5mm Li C Si “Tilt method” works !! E E01-011

Expected yield comparison of E and E ItemE (2 nd generation) E (1 st generation) Gain factor Virtual photon flux per electron(x10 -4 ) Target thickness(mg/cm 2 ) Kaon survival rate Solid angle of K arm (msr) Beam current (  A) Estimated yield ( 12  B gr :counts/h) 20(expected)0.9(measured)23

p(e,e ’ K + )  0 reactions on CH2 targets 12 C(e,e’K + ) quasi-free Accidental E89-009E  00 450 mg/cm2, 1.5  A, ~ 70 hours8.8 mg/cm2, 0.5 or 1.0  A, 183 hours 1.43 MeV (FWHM) 1.47 MeV (FWHM)

12 C (e,e ’ K + ) 12  B spectra Preliminary Hypernuclear excitation spectrum d  /d  nb/sr/0.3 MeV -B  (MeV) E01-011E ~ 800 keV Counts (0.25 MeV/bin) ss pp 292hrs 0.66  A Accidentals ~ 90 hrs 30  A T. Miyoshi et al., Phy. Rev. Lett. 90, (2003)

Sotona,Motoba 12 C (  ,K + ) 12  C B  = 10.8 MeV B  = -0.2 MeV 12  C g.s yield rate ~20 /hr (1 g/cm 2 target) KEK-E336 SKS Counts (0.2 MeV/bin) Reaction spectra on a 12 C target Counts (0.25 MeV/bin) ss pp JLAB – HKS ~ 90 hrs w/ 30  A Preliminary Accidentals B  (MeV) Core excited 12  B g.s yield rate ~8 /hr (0.1 g/cm 2 target) B  (s) = 11.5 MeV B  (p) = 1.0 MeV 12 C (e,e ’ K + ) 12  B (Preliminary)

Motoba with full (sd) n wave function Accidentals Counts (0.25 MeV/bin) Preliminary ss pp 28 Si(e,e ’ K + ) 28  Al reaction B  (MeV) 750 keV (FWHM) B  (s)= 18.1 MeV B  (p)= 7.4 MeV Reaction spectra on a 28 Si target ( Preliminary ) 28 Si(  ,K + ) 28  Si reaction B  (s)= 16.6 MeV B  (p)= 7.0 MeV KEK E140a SKS 28 Si enriched target used

Accidentals B  (MeV) Counts (0.4 MeV/bin) 7 Li(e,e’K + ) 7  He reaction Preliminary 30 hrs 30  A ss E. Hiyama, et al., PRC (1996) Sotona B  = 5.4 MeV ( Preliminary ) Reaction spectrum on a 7 Li target 960 keV (FWHM)

Evolution of (e,e ’ K + ) spectroscopy at JLab E89-009E94-107E01-011E ConfigurationSOS+ENGE+SplitterHRS+HRS+Septum HKS+ENGE +Splitter HKS+HES +New splitter Beam intensity (  A) on 12 C thickness (mg/cm 2 ) Hypernuclear yield (12  B gr : /hr) (12  B gr : /hr)0.948~(20)(~40) Resolution (keV) ~800 (400 keV) 700~800(3-400)(3-400) Beam energy (GeV) * p K (central : GeV) p e (central: GeV ) – 1.0  K (degree)  e (degree) ( ) expected ?

Summary Precision hypernuclear spectroscopy by the (e,e ’ K + ) reaction plays an essential role in the investigation of hadronic may-body systems that contain “ strangeness ”. Precision hypernuclear spectroscopy by the (e,e ’ K + ) reaction plays an essential role in the investigation of hadronic may-body systems that contain “ strangeness ”. The 2nd generation experiment in Hall C, JLab E01-011, has been performed in 2005, installing the new kaon spectrometer (HKS) and adopting so-called “ tilt ” geometry for the electron spectrometer. The 2nd generation experiment in Hall C, JLab E01-011, has been performed in 2005, installing the new kaon spectrometer (HKS) and adopting so-called “ tilt ” geometry for the electron spectrometer. Resolution as good as ~700 keV(FWHM) and yield rate of 7-8 counts/hr for the 12  B ground state doublet were realized. Resolution as good as ~700 keV(FWHM) and yield rate of 7-8 counts/hr for the 12  B ground state doublet were realized. Preliminary spectra for a 28 Si target as well as those for 12 C and 7 Li targets are presented, and compared with calculated spectra and (  +,K + ) reaction spectra. Preliminary spectra for a 28 Si target as well as those for 12 C and 7 Li targets are presented, and compared with calculated spectra and (  +,K + ) reaction spectra.