Study of Light -Hypernuclei by Spectroscopy
of Two Body Weak Decay Pions
(Update for E12-10-001)
Fragmentation of Hypernuclei
and
Mesonic Decay inside Nucleus
Free:
2-B:
 p +  A Z  A(Z + 1) +  
Liguang Tang
Department of Physics, Hampton University
Jefferson National Laboratory (JLAB)
Hall A Collaboration Meeting, June 9-10, 2011, JLAB
Decay Pion Spectroscopy to Study -Hypernuclei
Example:
Direct Production
e’
K+
12
C
*
e
Ground state doublet
12
of B
p
12

B


E.M.
12

Hypernuclear States:
s (or p) coupled to
low lying core nucleus
B and 
Bg.s.
21-

C
12
Weak mesonic two body decay
~150 keV
0.0
Decay Pion Spectroscopy for Light and Exotic -Hypernuclei
Fragmentation Process
Example: e’
K+
Access to variety of light
and exotic hypernuclei,
some of which cannot be
produced or measured
precisely by other means
12
e
C
*
12

B
p

*
Fragmentation
(<10-16s)
s
4

Highly Excited
Hypernuclear States:
s coupled to HighLying core nucleus, i.e.
particle hole at s orbit


H

4

Hg.s.
-


4
He
Weak mesonic two body
decay (~10-10s)
E12-10-001: Study of Light Hypernuclei by Pionic Decay at Jlab
Technique and Precision
•
Light hypernuclei which stop primarily in thin target foil
•
Weak 2 body mesonic decay at rest uniquely connects the decay pion momentum to the
well known structure of the decay nucleus, B and spin-parity of the ground state of
hyperfragment
•
Decay pion spectroscopy can be accurately measured and variety of physics may be
extracted
•
Most of the background particles move forward, thus pion momentum spectrum is
expected to be clean with minor 3-boby decay pions plus some from  decay
•
Precision and accuracy do not depend on the precisions of beam energy and tagged kaons
•
The momentum resolution can be at level of ~170keV/c FWHM, powerful in resolving
close-by states and different hypernuclei
•
B can be determined with accuracy at a level of 20keV
•
The experiment can be carried out in parasitic mode with high precision hypernuclear mass
spectroscopy experiment which measures the level structures of the primary hypernuclei,
as long as the two share the same target
E12-10-001 update @ Hall A Collaboration Meeting, June 9-10, 2011, JLAB
E12-10-001: Study of Light Hypernuclei by Pionic Decay at Jlab
Major Physics Objectives
• Precisely determine the single  binding energy B for the ground state of variety of light
hypernuclei: 3H,4H, ..., 11Be, 11B and 12B , i.e. A = 3 – 12 (few body to p shell).
• Determine the spin-parity Jp of the ground state of these light hypernuclei
• Measure CSB’s from multiple pairs of mirror hypernuclei such as:
6
He
and 6Li, 8Li and 8Be, 10Be and 10B.
• CSB can also be determined by combining with the existing emulsion result for hypernuclei
not measured in this experiment.
• Search for the neutron drip line limit hypernuclei such as: 6H, 7H and 8H which have
high Isospin and significant - coupling.
• May also extract B(E2) and B(M1) electromagnetic branching ratios through observation of
the isomeric low lying states and their lifetimes.
The high precision makes these above into a set of crucial and extremely
valuable physics variables which are longed for determination of the correct
models needed in description of the Y-N and Y-Nucleus interactions.
E12-10-001 update @ Hall A Collaboration Meeting, June 9-10, 2011, JLAB
E12-10-001: Study of Light Hypernuclei by Pionic Decay at Jlab
Illustration on the Main Features
Experimental Tech. & layout Example
Comparison of Spectroscopic and
Background - Production
(Example)
64mg/cm2
22mg/cm2
K+
-
SPECTROSCOPY
e
K+
Septum
e
e
*

p
A1
AZ
A2
A
(Z-1)
Z2
Lucite Č
-
K+
e’
Hodoscope
Drift Chamber
Z
 1 stop
Trigger I: HRS(K) & Enge() for Decay Pion Spectroscopy Experiment
Trigger II: HRS(K) & HRS(e’) for Mass Spectroscopy Experiment
A1(
Z1+1)
(Z-1) = Z1+Z2; A=A1+A2
VS
Light Hypernuclei to Be Investigated
p
Previously measured
6
BACKGROUND
e
e
*
p(n)
AZ
K+
-
,( )
-
(A-1)
Z’
10
8
9
12
11
9 Li
B
Additions
from
B
3/2B -B


B
1
7 L
8 H
+
9
8
and
its
continuum
11
8


L 10Be Be
L Be 9 Be
6 L

4
i
7
e

1/
i
i 10
 9
6
3B
8 +5/ 9 Li
7
3/2
i 1- ?
(Phase
Li
2Li 2
Li
HII: Be

Li
3 background
+
+
2
target)
E 6 He 0 7 1HeE 8 He 09 1HeE
0
1




2
0 2E x
x
x
3
8
4
5
6
7
H
H
H
H
H
x

H




1
Mirror pairs
(b)
5
N
1
2
3
Jp=?
1/2+
4
5
6
7
8
9
10
E12-10-001 update @ Hall A Collaboration Meeting, June 9-10, 2011, JLAB
11
12
A
Illustration of Decay Pion Spectroscopy
(c)
1-
Additions from 12B and its
continuum
12 B

(Phase III:
9 Be

11 B

Jp=?
10 B

9 He

11 Be

10
Li
5/2+
(b)
6
3B background
Li
8
1-
He
9
Li
Li
1- ?
5/2+
3/2+
0
1
Ex
0
1
Ex
and its continuum
target)
0
1- ?
6
3
He
H
7
1/2+
7 He

0
110.0
2
0 1
E
2 x
Ex
0+
4
6
H
H
5
H
Ex
0
120.0
- Momentum (MeV/c)
H
2-
3/2+ 5/2+
PMin
100.0
(Phase II: 9Be target)
Li
1/2+
3B background
90.0
8
1/2+
(a)2-B decay from 7 He

(Phase I:
H
Additions from 9Li and its
continuum
3/2+
1/2+
7
8
3B background
8 B

7Li
target)
10 Be

8 Be

9 B

12C
130.0
2
PMax
Ex
140.0
Feasibility Test Run at MAMI by A1 Collaboration
Spec-C
e’
Beam
KAOS
K+
MAMI Run Status
• The first beam period (Commissioning)
– May 24 to June 14, 2011
– Maximum beam current: 1.5A
– KAOS detector system needs to be further optimized in
order to run with high intensity run (50 A)
– Pion arm proven to be clean and low single rate
– Run is still undergoing
• The second period (implement e’ detector)
– July 19 to July 31, 2011
• The third possible beam period (higher intensity)
– November to December, 2011
• In general, the physics yield rate at MAMI is about 6
times smaller than that at JLAB
Summary
• High intensity CW beam at JLAB and the characters of
electro-production make possible for high precision
hypernuclear programs, among which the decay pion
program is unique.
• The decay pion spectroscopy program is able to provide
precise and fundamental information needed to
understand the YN and Y-Nucleus interactions.
• Unlike the mass spectroscopy program, this program does
not request precision and stability on beam energy.
• Test run at MAMI is undergoing