hypernuclear physics using cebaf beam past and future liguang tang hampton university/jlab 4 th...
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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
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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
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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
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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
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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
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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
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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
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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
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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)
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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
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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
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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
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6GEV PROGRAM HIGHLIGHTS
0
Allowing precise calibration of mass scale
p(e, e’K+) and 0 (CH2 target)
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-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
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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
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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
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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
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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
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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
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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
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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