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.