420 likes | 572 Views
Spectroscopic Investigation of L hypernuclei in the wide mass region using the (e,e’K + ) reaction (Extension request of the currently running E01-011 experiment). P05-115. Osamu Hashimoto Department of Physics, Tohoku University representing the HKS collaboration.
E N D
Spectroscopic Investigation of L hypernuclei in the wide mass region using the (e,e’K+) reaction(Extension request of the currently running E01-011 experiment) P05-115 Osamu Hashimoto Department of Physics, Tohoku University representing the HKS collaboration JLab PAC28 August 24, 2005
Hyper Collaboration • O. Hashimoto (Spokesperson), S.N. Nakamura (Spokesperson), Y. Fujii, M. Kaneta, M. Sumihama, H. Tamura,K. Maeda, H. Kanda, Y. Okayasu, K. Tsukada, A. Matsumura, K.~Nonaka, D. Kawama, N. Maruyama, Y. Miyagi (Tohoku U) • S. Kato (Yamagata U) • T. Takahashi, Y. Sato, H. Noumi (KEK) • T. Motoba (Osaka EC) • L. Tang (Spokesperson), O.K. Baker, M. Christy, L. Cole, P. Gueye, C. Keppel, L. Yuan (Hampton U) • J. Reinhold (Spokesperson), P. Markowitz, B. Beckford, S. Gullon, C. Vega (FlU) • Ed.V. Hungerford, K. Lan, N. Elhayari, N. Klantrains, Y. Li,S. Radeniya (Houston) • R. Carlini, R. Ent, H. Fenker, 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) • D. Dehnhard (Minnesota) • M. Elaasar(New Orleans) • R. Asaturyan, H. Mkrtchyan, A. Margaryan, S. Stepanyan, V. Tadevosyan (Yerevan) • D. Androic, T. Petkovic, M. Planinic, M. Furic (Zagreb) • T. Angelescu (Bucharest) • V.P. Likhachev (Sao Paulo) • M. Ahmed (Duke)
Outline of the talk • Significance of hypernuclear spectroscopy and goals of the proposed experiment • (e,e’K+) spectroscopy and the current status of E01-011 experiment 3. Setup & conditions of the proposed experiment 4. Summary with prospect
Significance of hypernuclear spectroscopyandthe goals of the proposed experiment
Single-particle nature of L hypernuclei Core Nucleus + L Singly charged atom A L hyperon in the mean field • New degree of freedom free from Pauli blocking • Deeply bound nuclear states • Baryon structure in nuclear medium • Unique structure of hadronic many-body system • Nucleus with a new quantum number • Core excited states • Glue role of a L hyperon • LN interaction • Unified view of baryon-baryon interaction in SU(3) • Central and spin-dependent LN interaction Core excitation,
e’ e p Nucleon single particle orbits
Single-particle nature of L hypernuclei Core Nucleus + L Singly charged atom A L hyperon in the mean field • New degree of freedom free from Pauli blocking • Deeply bound nuclear states • Baryon structure in nuclear medium • Unique structure of hadronic many-body system • Nucleus with a new quantum number • Core excited states • Glue role of a L hyperon • LN interaction • Unified view of baryon-baryon interaction in SU(3) • Central and spin-dependent LN interaction Core excitation,
YN, YY Interactions and Hypernuclear Structure Free YN, YY interaction Constructed from limited hyperon scattering data (Meson exchange model: Nijmegen, Julich) G-matrix calculation YN, YY effective interaction in finite nuclei (YN G potential) Hypernuclear properties, spectroscopic information from structure calculation (shell model, cluster model…) Energy levels, Energy splitting, cross sections Polarizations, weak decay widths high quality (high resolution & high statistics) spectroscopy plays a significant role
Population of excited L hypernuclear statesand L hypernuclear spectroscopy L-particle nucleon-hole states neutron or proton L ~25 MeV BL p Narrow widths < a few 100 keV p Reaction spectroscopy Bp n Bn 207LTl g 207LPb 208LPb Gamma-ray spectroscopy Weak decay nonmesonic mesonic
BL=0 L Hypernuclear production (K-,p-) Inflight(K-,p) BNL, CERN mb/sr (p+,K+) Stopped (K-,p) KEK, BNL Hypernuclear Cross section mb/sr (p+,K+) JLab (e,e’K+) (g,K+) (p+,K+) nb/sr (p,K+) 0 500 1000 Momentum transfer (MeV/c)
Hypernuclei in the wide mass range -- toward strange matter -- • Short range nature of the LN interaction : no pion exchange • meson picture or quark picture ? • Light hypernuclei (A<~20) • Fine structure • Baryon-baryon interaction in SU(3) • LScoupling in large isospin hypernuclei • Cluster structure • Heavy hypernuclei (A>~50) • Single-particle potential • Distinguishability of a L hyperon • U0(r), mL*(r), VLNN, ... • Neutron star (A ~ 1057 ) • Hyperonization Softening of EOS ? • Superfluidity
12C(p+,K+) 12LC spectraby the SKS spectrometer at KEK 12 GeV PS BNL 3 MeV(FWHM) SKS SKS KEK E369 1.45 MeV(FWHM) Hypernuclear spectroscopy established KEK336 2 MeV(FWHM)
KEK E140a Hasegawa et. al., PRC 53 (1996)1210 L hyperon in heavier nuclei L Single particle states -> L-nuclear potential Hotchi et al., PRC 64 (2001) 044302 Si Y La Pb Single-particle orbits in nucleus • Skyrme HF (Yamamoto) • DDRH (Lanske) • Quark-meson coupling • (Saito, Thomas) • ………
Goals of the proposed experiment • 51V(e,e’K+)51LTi reaction • Next heavier L hypernuclei from 28LAl • L binding energies for s,p,d orbits determined • L hypernuclear structure investigated • ls splitting in l=2,3 orbits to b derived If sizable • 89Y(e,e’K+)89LSr reaction • Exploratory run to examine feasibility of (e,e’K+) spectroscopy in heavier hypernuclei • 6,7Li(e,e’K+)6,7LHe and 10,11B(e,e’K+)10,11LBe • Precision hypernuclear structure in neutron-rich L hypernuclei • LS coupling effect changing isospins with neutron number
L Hyperon production reactions for spectroscopy DZ = 0 DZ = -1 comment neutron to L proton to L (p+,K+) ( p-,K0) stretched, high-spin large momentum transfer In-flight (K-,p-) in-flight (K-,p0) substitutional stopped (K-,p-) stopped (K-,p0) large momentum transfer (e,e'K0) (e,e'K+) spin-flip (g,K0) (g,K+) & large momentum transfer The (e,e’K+) reaction for hypernuclear spectroscopy • Proton to L Neutron rich L hypernuclei • Large angular momentum transfer • Spin-flip amplitude & Higher energy resolution A few 100 keV achievable First (e,e’K+) spectroscopy E89-009 (SOS + ENGE) Only at JLab
What limited the E89-009 experiment ? • Energy resolution • The kaon arm limited hypernuclear mass resolution • Hypernuclear yield rates • High accidental background rate due to Brems electrons • Solid angle of the kaon arm (SOS) limited detection efficiency (1) A high-resolution large-solid-angle kaon spectrometer (HKS) (2) New experimental configuration “Tilt method”
Side view Tilt method and optimization of the tilt angle Singles rate of the e-arm 200 MHz < a few MHz even with 5 Target thickness and 50 Beam intensity
The HKS spectrometer system for E01-011 High resolution Kaon Spectrometer (HKS) Maximum momentum 1.2 GeV/c Dispersion 4.7 cm/% Momentum resolution 2 x 10-4(FWHM) Solid angle 30 msr w/o splitter 16 msr w splitter Momentum acceptance 12.5 % Tilt method for the electron arm
E01-011 setup in Hall C Tilted ENGE HKS ENGE
Expected singles rates Ie = 30 mA, 100 mg/cm2 Measured values at E89-009 Ie = 0.66 mA, 22 mg/cm2 Greater hadron rates High rejection efficiencies against pions and protons are required
Beam currents, singles rates & trigger rates E01-011 Tilt method proved to work !!
coincidence time (ns) p K p Kaon PID E01-011 HKS singles events HKS-ENGE coincidence events btof – btrack
p(e,e’K+)L/S0 reactions E89-009 experiment E01-011 experiment Improved! 12C(e,e’K+) quasi-free Accidental 210 Lambda’s 1390 Lambdas
(1-,2-) (2+,3+) 90 80 (1-,0-) 70 (2-,1-) 60 50 40 -15 -10 -5 0 5 10 15 12LB spectrum ( 12C target ) E01-011 E89-009 < 1MeV (FWHM) 1 month ds/dW nb/sr/0.3 MeV Preliminary Hypernuclear excitation (300 keV/bin) -BL(MeV) 12LBg.s~ 600 counts (~20 /hr) <1 MeV (FWHM) 400 keV vs. E89-009 Hall C ~ 165 counts with ~750 keV (~0.9 /hr) E94-107 Hall A ~ 600 counts with ~800 keV (~3 /hr)
Proposed experimental setup & conditions Basically similar to those of E01-011 except for the new High-resolution electron spectrometer and some improvement based on the E01-011 experience
HKS-HES hypernuclear spectrometer system New Splitter
Acceptable energy windows of HKS systemwith ENGE or HES ENGE HES Acceptable Central Energy (GeV) 0.3 0.4 0.6 0.8 1 Ee’ (GeV) 1.8 1.9 2.0 2.2 2.4 2.5 2.1 Ee at Hall (GeV) Etop2pass (GeV) 4.4 4.55 5.0 6.0 Etop1pass (GeV) 9.45 10.3 10.8 12.0
Basic specification of HES • Configuration DQQD horizontal 50 degree bend • Central momentum 0.6 – 1.0 GeV/c • Momentum acceptance > 200 MeV/c • Momentum resolution 2 x 10-4 • Electron detection angle horizontal : 0 degrees vertical : < 10 degrees • Solid angle > 10 msr • Maximum D magnetic field 1.6 T
Splitter, HKS, HES geometry 1.0 GeV/c HES HKS 0.6 GeV/c New Splitter Splitter TOSCA calculation
HES mechanical design For 600 MeV/c For 1000 MeV/c
Expected Energy Resolution <~400 keV(FWHM) expected
Expected hypernuclear production ratesin the (e,e’K+) reaction Calculated hypernuclear cross sections Hypernuclear production rates (Target thickness 100 mg/cm2) Motoba, Sotona
51LTi and 51LV spectra KEK SKS data Simulation
Evolution of (e,e’K+) spectroscopy 2000 2004-2005 2005 200? ( ) expected * ENGE spectrometer to be used for a 1.8 GeV beam
Roadmap of (e,e’K+) hypernuclear spectroscopy HKS as a “strangeness tagger” HES as a “virtual photon tagger” • Light L hypernuclear spectroscopy • LN interaction, LS coupling • p shell hypernuclei 6,7Li,9Be,10,11B, 12C, 13C,16O targets • s shell hypernuclei 3,4He targets • Medium to heavy hypernuclear spectroscopy • A L binding in the mean field, quark picture vs. conventional picture • 28Si, 51V, (Cr) 89Y 208Pb ? targets • Coincidence experiment • weak decay --- fission • proton, neutron and pion emission Complimentary to spectroscopy with hadronic beams at J-PARC
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”. • Physics goal of the proposed experiment is two-fold; spectroscopy of heavier L hypernuclei (51V target) and light L hypernuclei(6,7Li or10,11B targets). • A high resolution electron spectrometer (HES) is under construction at TOHOKU as a part of the HKS-HES hypernuclear spectrometer system. It will be shipped to JLab at the end of 2006. • The HKS-HES spectrometer system allows us to conduct the proposed 3rd generation (e,e’K+) hypernuclear spectroscopy even with 6 GeV and 12 GeV operation.