spectroscopic investigation of hypernuclei in the wide mass region using the (e,e’k + ) reaction...
TRANSCRIPT
Spectroscopic Investigation of hypernuclei in the wide mass region
using the (e,e’K+) reaction(Extension request of the currently running E01-011 experiment)
Osamu Hashimoto Department of Physics, Tohoku University
representing the HKS collaboration
JLab PAC28 August 24, 2005
P05-115
Hyper Collaboration• O. Hashimoto (Spokesperson), S.N. Nakamura (Spokesperson), Y. Fujii, M. Kaneta, M. S
umihama, 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 (H
ampton 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
1. Significance of hypernuclear spectroscopy and
goals of the proposed experiment
2. (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 spectroscopy
andthe goals of the proposed experiment
3D Nuclear Chart with the strangeness degree of freedom
Single-particle nature of hypernuclei
• 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 hyperon
• N interaction• Unified view of baryon-baryon interaction in SU(3)• Central and spin-dependentN interaction
Singly charged atomCore Nucleus +
Core excitation,
A hyperon in the mean field
Nucleon single particle orbits
e e’
p
Single-particle nature of hypernuclei
• 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 hyperon
• N interaction• Unified view of baryon-baryon interaction in SU(3)• Central and spin-dependentN interaction
Singly charged atomCore Nucleus +
Core excitation,
A hyperon in the mean field
YN, YY Interactions and Hypernuclear Structure
Free YN, YY interactionConstructed from limited hyperon scattering data
(Meson exchange model: Nijmegen, Julich)
YN, YY effective interaction in finite nuclei(YN G potential)
Hypernuclear properties, spectroscopic informationfrom structure calculation (shell model, cluster model…)
Energy levels, Energy splitting, cross sectionsPolarizations, weak decay widths
i
iFiFiiN rkckbarv )/exp()()( 222
high quality (high resolution & high statistics) spectroscopy plays a significant role
G-matrix calculation
Population of excited hypernuclear statesand hypernuclear spectroscopy
neutron orproton
n
p
B
Bp
Bn
208Pb
207Tl
207Pb
Weak decay nonmesonic mesonic
Narrow widths< a few 100 keV
-particle nucleon-hole states
~25 MeV
Reaction spectroscopy
Gamma-ray spectroscopy
B=0 Hypernuclear
production
(+,K + )
Stopped (K-,)
(e,e’K+)(,K + )
(p,K+ )
Inflight(K-,)
Hyp
ernu
clea
r C
ross
sec
tio n
Momentum transfer (MeV/c)
mb/sr
nb/sr
b/sr
0 500 1000
JLab
KEK, BNL
BNL, CERN
(K-,-)
(+,K+)
(+,K+)
• Light hypernuclei (A<~20)• Fine structure• Baryon-baryon interaction in SU(3)• coupling in large isospin hypernuclei• Cluster structure
• Heavy hypernuclei (A>~50)• Single-particle potential• Distinguishability of a hyperon
U0(r), m*(r), VNN, ...
• Neutron star (A ~ 1057 )• Hyperonization Softening of EOS ?• Superfluidity
Hypernuclei in the wide mass range-- toward strange matter --
• Short range nature of the N interaction : no pion exchange meson picture or quark picture ?
12C(+,K+) 12C spectra
by the SKS spectrometer at KEK 12 GeV PS
KEK336 2 MeV(FWHM)
KEK E369 1.45 MeV(FWHM)
Hypernuclear spectroscopy established
BNL 3 MeV(FWHM)
SKS
SKS
Single particle states
-> -nuclear potential
hyperon in heavier nuclei
Single-particle orbits in nucleus
Hotchi et al., PRC 64 (2001) 044302 Hasegawa et. al., PRC 53 (1996)1210KEK E140a
• Skyrme HF (Yamamoto)• DDRH (Lanske)• Quark-meson coupling (Saito, Thomas)• ………
Y La PbSi
Goals of the proposed experiment
• 51V(e,e’K+)51Ti reaction
– Next heavier hypernuclei from 28Al
– binding energies for s,p,d orbits determined– hypernuclear structure investigated– ls splitting in l=2,3 orbits to b derived If sizable
• 89Y(e,e’K+)89Sr reaction
– Exploratory run to examine feasibility of (e,e’K+)
spectroscopy in heavier hypernuclei
• 6,7Li(e,e’K+)6,7He and 10,11B(e,e’K+)10,11
Be – Precision hypernuclear structure in neutron-rich hypernuclei– LS coupling effect changing isospins with neutron number
(e,e’K+) spectroscopy andE01-011 status
The (e,e’K+) reaction for hypernuclear spectroscopy
• Proton to Neutron rich hypernuclei
• Large angular momentum transfer
• Spin-flip amplitude
Hyperon production reactions for spectroscopy
Z = 0 Z = -1 comment neutron to proton to
(+,K+) (-,K0) stretched, high-spin large momentum transfer
In-flight (K-,-) in-flight (K-,0) substitutional
stopped (K-,-) stopped (K-,0) large momentum transfer (e,e'K0) (e,e'K+) spin-flip (K0) (,K+) & large momentum transfer
Higher energy resolution&
First (e,e’K+) spectroscopy E89-009 (SOS + ENGE)
A few 100 keV achievable
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”
Tilt method and optimization of the tilt angle
Side view
Singles rate of the e-arm 200 MHz < a few MHzeven with 5 Target thickness and 50 Beam intensity
Maximum momentum 1.2 GeV/cDispersion 4.7 cm/%Momentum resolution 2 x 10-4(FWHM)Solid angle 30 msr w/o splitter 16 msr w splitterMomentum acceptance 12.5 %
The HKS spectrometer system for E01-011
Tilt methodfor the electron arm
High resolution Kaon Spectrometer (HKS)
E01-011 setup in Hall C
ENGE
HKS
Tilted ENGE
Expected singles rates
TargetHKS ENGE
e+
(kHz)+
(kHz)K+
(kHz)p
(kHz)e-
(kHz)-
(kHz)
12C - 420 0.38 150 1,000 2.8
28Si - 420 0.32 130 1,960 2.8
51V - 410 0.29 120 2,650 3.0
E89-009 12C
100 1.4 <1 Hz 0.14 200,000 -
SOS ENGE
Ie = 30 A, 100 mg/cm2
High rejection efficiencies against pions and protons are required
Measured values at E89-009 Ie = 0.66 A, 22 mg/cm2
Greater hadron rates
Yield comparison of E01-011 and E89-009
Item E01-011 E89-009Gain factor
Virtual photon flux per
electron(x10-4)0.2 4 0.05
Target thickness(mg/cm2) 100 22 4.5
Scattered electron momentum acceptance(MeV/c)
190 120 1.6
Kaon survival rate 0.35 0.4 0.88
Solid angle of K arm (msr) 16 5 3.2
Beam current (A) 30 0.66 45
Estimated yield
(12Bgr:counts/h)
41(expected)
0.9(measured) 46
Beam currents, singles rates & trigger rates E01-011
TargetBeam curr
ent
(A)
COIN Trigger
rate (Hz)
HKS singles
rate (kHz)
ENGE singles
rate (kHz)
CH2
(5 mm)1.5 88 3.4 590
12C(100 mg/cm2)
24 290 9.5 980
28Si(65 mg/cm2)
12 377 7.0 1040
Tilt method proved to work !!
p
K
Kaon PID E01-011
coincidence time (ns)
tof
–
trac
k
HKS singles events HKS-ENGE coincidence events
p(e,e’K+)0 reactions
12C(e,e’K+) quasi-free
Accidental
E89-009 experiment E01-011 experiment
Improved!
210 Lambda’s 1390 Lambdas
-15 0 5 10 15-5-10
(2+,3+)(1-,2-)
(1-,0-)
(2-,1-)
40
50
60
70
80
90
12B spectrum ( 12C target )
12Bg.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)
Prelim
inary
Hypernuclear excitation (300 keV/bin)
d/
d
nb
/sr/
0.3
MeV
-B(MeV)
1 month
E01-011E89-009
< 1MeV (FWHM)
Proposed experimental setup & conditions
Basically similar to those of E01-011except for the new High-resolution electron spectrometer
and some improvement based on the E01-011 experience
HKS-HES hypernuclear spectrometer system
New Splitter
Etop1pass
(GeV)
Etop2pass
(GeV)
Acceptable energy windows of HKS systemwith ENGE or HES
10.40.3 0.6 0.8
Ee’ (GeV)
2.51.8 1.9Ee at Hall
(GeV)
Acceptable Central Energy
(GeV)
HESENGE
2.0 2.2 2.4
4.4 4.55 5.0 6.0
9.45 10.3 10.8 12.0
2.1
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
HKSHES
New Splitter
0.6 GeV/c
1.0 GeV/c
Splitter TOSCA calculation
HES mechanical design
For 600 MeV/cFor 1000 MeV/c
Expected Energy Resolution
ItemContribution to the resolution
(keV, FWHM)
Target 7Li 12C 51V 89Y
HKS momentum 190 ( 500 for SOS)
Beam momentum < 180
Enge or HES momentum
93
K+ angle 230 152 36 20
Target thickness < 170 < 180 < 148 < 138
Overall < 400 < 360 < 320 < 310
<~400 keV(FWHM) expected
Expected hypernuclear production ratesin the (e,e’K+) reaction
TargetBeam Int
ensity
(A)
Counts per
100nb/sr/hour
Q-free K+ in
HKS(Hz)
12C 30 48 340
28Si 30 21 288
51V 30 11 228
TargetHypernucle
us orbitalCross secti
on
(nb/sr)
12C 12B
s1/2 112
p3/2 79
p1/2 45
28Si 28Al
s1/2 56
p3/2 95
p1/2 57
d5/2 131
d3/2 111
51V 51Ti
s1/2 18
p3/2 41
p1/2 26
d5/2 52
d3/2 48
1s1/2 16
f7/2 32
f5/2 38
Calculated hypernuclear cross sections
(Target thickness 100 mg/cm2)
Hypernuclear production rates
Motoba, Sotona
51Ti and 51
V spectra
KEK SKS dataSimulation
Evolution of (e,e’K+) spectroscopy
E89-009 E94-107 E01-011 P05-115*
ConfigurationSOS+ENGE
+Splitter
HRS+HRS
+Septum
HKS+ENGE
+Splitter
HKS+HES
+New splitter
Beam intensity (A) on 12C 0.66 100 24 30
thickness (mg/cm2) 22 100 100 100
Hypernuclear yield
(12Bgr : /hr)0.9 2-3 20 ~ (40) (> 40)
Resolution (keV) 750-900 ~ 800 (3-400) (3-400)
Beam energy (GeV) 1.7-1.8 4 1.8 2.0 - 2.4*
pK (central : GeV) 1.2 1.9 1.2 1.2
Pe (central: GeV ) 0.3 2.2 0.3 0.6 – 1.0
K (degree) 0-7 6 1-13 1-13
e (degree) 0 6 4.5 < 4.5
( ) expected* ENGE spectrometer to be used for a 1.8 GeV beam
2000 2004-2005 2005 200?
Roadmap of (e,e’K+) hypernuclear spectroscopy
• Light hypernuclear spectroscopy– N interaction, 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 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
HKS as a “strangeness tagger”HES as a “virtual photon tagger”
Complimentary to spectroscopy with hadronic beams at J-PARC
Requested beam timeTarget Hypernucleus # of days # of hours
Spectrometer commissioning &
calibration4(8) 96(192)
Data taking
6,7Li,10,11B
6,7He, 10,11
Be 5 120
51V 51Ti 14 336
89Y 89Sr 5 120
Subtotal for data taking 24 576
Grand total 28(32) 672(768)
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 hypernuclei (51V target) and light hypernuclei(6,7Li or10,1
1B 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.