Study of Light -Hypernuclei by Spectroscopy of Two Body Weak Decay Pions Liguang Tang Department of...
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Transcript of Study of Light -Hypernuclei by Spectroscopy of Two Body Weak Decay Pions Liguang Tang Department of...
Study of Light -Hypernuclei by Spectroscopy of Two Body Weak Decay Pions
Liguang Tang
Department of Physics, Hampton UniversityJefferson National Laboratory (JLAB)JLab PAC40, June 18, 2013
Fragmentation of Hypernuclei and
Mesonic Decay inside Nucleus
Free: p + -
2-B: AZ A(Z + 1) +
-
This previous PR12-10-001 is now proposed as a part of combined experiments that can run at same time to maximize physics outcome
HRS – HKS: (e, e’K+) experiments for mass spectroscopyHKS – Enge or HKS – HES: New decay - spectroscopy experiment
Future Project: Super Hypernuclear Physics Experiment at JLab
Unified collaboration from the previous Hall A and C collaborations
Enge ()
HES () HKS (K)
HRS (e’)Septum
Septum
Combine the features of previous Hall A and C experiments, create an optimized future program w/ the CEBAF CW beam
Decay Pion Spectroscopy to Study -Hypernuclei
12C -
Weak mesonic two body decay
1- 0.02- ~150 keV
Ground state doublet of 12
BB 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 hypernuclei, some of
which cannot be produced or measured
precisely by other means
e e
* K+
p
AZ
A(Z-1)
A1Z1 stop
A2Z2
(Z-1) = Z1+Z2; A=A1+A2
-
A1(Z1+1)
SPECTROSCOPYe e
* K+
,(-) p(n)
AZ (A-1)Z’
-
N
BACKGROUND
VS
Comparison of Spectroscopic and Background - Production
(b)
3B background
20 Ex
10 Ex 10 Ex 10 Ex
2-
3/2+
5/2+1/2+
9Li8
HeJp=? 1-
8Li
7H
1/2+
3/2+
7Li
1- ?
6Li
Additions from 9Li and its
continuum
(Phase II: 9Be target)
A
p
1 2 3 4 5 6 7 8 9 10 11 12
1
2
3
4
5
6
3H 4
H5H
6H
7H
8H
6He 7
He 8He 9
He
6Li 7
Li 8Li 9
Li 10Li
11Be9
Be 10Be8
Be
11B
9B
10B
8B 12
B
Light Hypernuclei to Be Investigated
Previously measured
Mirror pairs
Study of Light Hypernuclei by Pionic Decay at JlabIllustration on the Main Features
(a)2-B decay from 7He and
its continuum
(Phase I: 7Li target) 1/2+
PMaxPMin 0 2Ex Ex
0 2
4H
0+
7He
1/2+
3/2+5/2+
3H
6He
1- ?
6H
5H
90.0 100.0 110.0 120.0 130.0 140.0- Momentum (MeV/c)
3B background
(b)
3B background
20Ex
10Ex 10
Ex 10Ex
2-
3/2+
5/2+
1/2+
9Li
8He
1-
8Li
7H
1/2+
3/2+
7Li
1- ?
6Li
Additions from 9Li and its
continuum
(Phase II: 9Be target)
(c) Additions from 12B and its
continuum
(Phase III: 12C target)
12B
1-
11Be
11B 10
Li
10Be
5/2+Jp=?10B
9He
9Be
9B
8H
8Be
8B 3B background
Illustration of Decay Pion Spectroscopy
• Precise measurement of ground state B (20keV) for a series of light hypernuclei with high resolution (130keV), spin-parity determination of g.s., charge symmetry breaking (CSB) from mirror pairs
• Neutron rich light hypernuclei (- coupling) and neutron drip line limit (6
H and 8H)
• Formation of quasi free continuum and fragmentation mechanism
Physics Goal of Decay Pion Spectroscopy
Provide precise input for theoretical description of -N interaction. Since B and excitation are the only sources of experimental information, study wide range of hypernuclei is needed.
Preliminary Results from MAMI-C
4H
2011 RunPartial
2012 RunPartial
KID affected by huge rate of e+ at 0
• Added 10cm Pb curtain
• Luminosity increased• KID was still a problem• K+ singles increased
just a little
KAOS – SPEC-C
2A beam
20A beam
We are convinced at least on 4
H observation
• Higher production rate (~9 times)• Excellent PID for both K+ and -
• Less background (accidental or real)• Full coverage of the interested - momentum
range• Can take data together with the (e, e’K+)
experiment
Advantages of Jlab Experiment
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.
• We are convinced from the MAMI-C test runs that the technique works.