HYPERNUCLEAR PHYSICS USING CEBAF BEAM

PAST AND FUTURE

Liguang TangHampton University/JLAB

4th Workshop on Hadron Physics In China and Opportunities with JLAB 12GeV

July 16-20, 2012

INTRODUCTION – BARYONIC INTERACTIONSBaryonic interaction (B-B) is an important part of nuclear force that builds the “world”

Astronomical Scale -

Neutron Stars -

H (1p)

He( - 2p,

2n)

C (3 )

Understand B-B interactions is one of the essential tasks in Nuclear Physics

INTRODUCTION – JP=1/2+ BARYON FAMILY

,0

(uds)

n(udd

)

p+

(uud

)

+

(uus)

-

(dds)

-

(dss)

0

(uss)

S

Q

I

S = 0

S = -1

S = -2

I3 = -1

I3 = +1/2

I3 = -1/2

I3 = +1

I3 = 0

Nucleon (N)

Hyperon (Y)

S - Strangeness I - Isospin

INTRODUCTION – HYPERNUCLEAR PHYSICS

To understand YN and YY interactions Producing Y inside of the nucleus Extract YN and YY interactions by studying the many body system

To study short range interactions in baryonic interactions (OPE is absent in N interaction)

To better explore nuclear structure using as a probe (not Pauli blocked by nucleons) and to explore new degree of freedom Model the baryonic many body system Study the role and the single particle nature of in various nuclear

medium and density

N and are the most fundamental interactions. Since decays only weakly (N or NNN) thus long lifetime, mass spectroscopy -hypernuclei becomes possible analog to the nuclear mass spectroscopy

Shell Model with 2-B N Effective Potential (pNs)

VN = V0(r) + V(r) sNs + V(r) LN s + VN(r) LN sN + VT(r) S12

Additional Contribution: - coupling N N Contribute to the repulsive core Introduce an additional term:

Observables: Ground state single binding energy Excitation spectroscopy (levels and level spacing) Production and production cross sections Decays

V— S SN T

5 Radial Integrals: Coefficients of operators

THEORETICAL DESCRIPTION: 2B POTENTIAL

BASIC PRODUCTION MECHANISMS

AZ

n

AZ

-K-(K, ) Reaction

Low momentum transfer Higher production cross section Substitutional, low spin, & natural parity states Harder to produce deeply bound states

AZ

n

A

+ K+(, K) Reaction

High momentum transfer Lower production cross section Deeply bound, high spin, & natural parity states

A(Z-1)

p

AZ

e e’

K+

(e, e’K) Reaction

High momentum transfer Small production cross section Deeply bound, highest possible spin, & unnatural parity states Neutron rich hypernuclei

CERN BNL KEK & DANE J-PARC (Near Future)

Disadvantage: Lack absolute energy calibration and

resolutionCEBAF at JLAB

(MAMI-C Near Future)Advantage: Absolute energy

calibration& high resolution

RELIABILITY OF EMULSION RESULTSUSING (K-

STOP, -) REACTION

4He

4H

3H

7He

7Li

6He

B (MeV)

5He

9Be

9Li

8Be

8Li

8He

7Be

13N

13C

10B

12B

11B

9B

Important source of data but lack statistics and resolution

Reliability: Questionable

Nevertheless, emulsion experiments before 80’s

provided the most complete set of measured single binding energy B of s- and p-shell -

hypernuclei

ACHIEVEMENT OF GAMMA SPECTROSCOPY22 GAMMA TRANSITIONS WERE SO FAR OBSERVED

Missing predicted

gamma ray

Advantages: High resolution (~ few keV) and precise level spacing

Disadvantages: low rate (statistics) and unable to measure the ground state binding energy

IMPORTANCE OF RESOLUTION AND MASS CALIBRATION EXAMPLE: 12C(+,K+)12

C MASS SPECTRA WITH MESON BEAM

KEK336 2 MeV(FWHM)

KEK E369 1.5 MeV(FWHM)

High resolution, high yield, and systematic study is essential and is the key to unlock the “gate”

Meson beam lacks absolute mass calibration (no free neutron target)

BNL 3 MeV(FWHM)

ELECTRO-PRODUCTION USING CEBAF BEAM

High quality primary beam allows high precision mass spectroscopy on -hypernuclei

Producing and 0 from proton simultaneously allows absolute mass calibration – precise binding energy

Mirror and neutron rich hypernuclei comparing those from (+,K+) reaction

Spectroscopy dominated by high spin-stretched spin-flip states

Results are important in determining , SN and V0 terms from s states and S term from states with at higher orbits

HALL C TECHNIQUE IN 6GEV PROGRAM

Zero degree e’ tagging High e’ single rate Low beam luminosity High accidental rate Low yield rate A first important milestone for hypernuclear physics with electro- production

Beam Dump

Target

Electron Beam

　　　　 Focal Plane( SSD + Hodoscope )

K+

K+

QD

_D

0 1m

QD_D

Side View

Top View

Target

(1.645 GeV)

Phase IE89-009

K+

e’Phase IIE01-011

Common Splitter Magnet

New HKS spectrometer large Tilted Enge spectrometer Reduce e’ single rate by a factor of 10-5 High beam luminosity Accidental rate improves 4 times High yield rate First possible study beyond p shell

HALL C TECHNIQUE IN 6GEV PROGRAM

New HES spectrometer larger Same Tilt Method

High beam luminosity

Further improves accidental rate Further improves resolution and accuracy

High yield rate

First possible study for A > 50

Beam2.34 GeV

e’

K+

e

Phase IIIE05-115

Common Splitter Magnet

6GEV PROGRAM HIGHLIGHTS

0

Allowing precise calibration of mass scale

p(e, e’K+) and 0 (CH2 target)

-B L (MeV)

-6.680.02 0.2 MeV from aLnn

7He

E94-107 in Hall A (2003 & 04)

s (2-/1-)

p

(3+/2+’s)

Core Ex. States

~635 keV

FWHM

12B

6GEV PROGRAM HIGHLIGHTS– CONT.

K+ _D

K+

1.2GeV/c

Local Beam Dump

E89-009 12ΛB spectrum~800

keVFWHM

HNSS in 2000s p

Phase I in Hall C (E89-009)

Phase II in Hall C (E01-011)

B (MeV)

28Si(e, e’K+)28Al (Hall C

E01-011) H

KS

JLAB

C

ou

nts

(1

50

ke

V/b

in)

28

Al

s

p

d

AccidentalsPhase II in Hall C

(E01-011)~500 keV

FWHM

HKS in 2005

12B

16N (Hall

A) F. Cusanno et al, PRL 103 (2009)

16 N

F. Cusanno et al, PRL 103 (2009)

s p

Phase III in Hall C (E05-115)

s p

6GEV PROGRAM TECHNIQUE SUMMARY

Hall A experiment (Pair of Septums + two HRS) Advantage: Almost no accidental background

and be able to study elementary process at low Q2 at forward angle

Disadvantage: Low yield rate and cannot study heavier hypernuclei

Hall C experiment (Common Splitter + HKS + HES/Enge) Advantage: High yield rate and high precision

in binding energy measurement Disadvantage: High accidental background

and solid targets only

Future program: Combination

EXPERIMENTAL LAYOUT IF IN HALL C

HKS - Kaons

Enge - Pions

HES - Electrons

Hodoscope

Lucite Č

Drift Chamber

64mg/cm2

22mg/cm2

K+

-

Trigger I: HKS(K) & Enge() for Decay Pion Spectroscopy ExperimentTrigger II: HKS(K) & HES(e’) for Mass Spectroscopy Experiment

High quality with low background High precision on binding energy and high

resolution High yield rate which leads to wide range of physics:

Elementary production at forward angle Detailed and precise level structure of light and

medium heavy hypernuclei (shell models) Precise shell structure of heavy hypernuclei (single

particle nature and field theory) High efficiency and productivity:

one exp. Four 6GeV experiments New physics: Decay pion spectroscopy (Light

Hypernuclei) Precise ground state B Determination of ground state Jp Search for neutron rich limit (high Isospin states )

Technical Features of Future Program

DECAY PION SPECTROSCOPY TO STUDY -HYPERNUCLEI

12C -

Weak mesonic two body decay

1- 0.02- ~150 keV

Ground state doublet of 12

B

B and

Direct Production

p

e’

e12C K

+

Example:

Hypernuclear States:s (or p) coupled to low lying core nucleus

12Bg.s.

E.M.

*

12B

DECAY PION SPECTROSCOPY FOR LIGHT AND EXOTIC -HYPERNUCLEI

Fragmentation Process

p

e’

e 12C

Example: K +

*

s12B*

Highly Excited Hypernuclear States:s coupled to High-Lying core nucleus, i.e.particle hole at s orbit

4H

Fragmentation (<10-16s)

4Hg.s

.

4He

-

Weak mesonic two body decay (~10-10s)

Access to variety of light and exotic

hypernuclei, some of which cannot be

produced or measured precisely by other

means

110 ~ 160 MeV/c 110.05 ~ 160.05 MeV/c 110.1 ~ 160.1 MeV/c

110.15 ~ 160.15 MeV/c 110.2 ~ 160.2 MeV/c

Possible observation4H ground state

Central Mom. : 133.5 MeV/c → BΛ(4ΛH) : ~ － 1.60 MeV

Width : 97 keV/c FWHMTarget straggling loss was not correctedSpec-C momentum calibration was not yet done

MAMI-C Short Test Run on Decay Pion Spectroscopy

SUMMARY

Hypernuclear Physics is an important part of nuclear physics

Program with CEBAF beam is the only one that provides precise B and features as

Precision mass spectroscopy program

Future program will be highly productive