Recent Spectroscopic
Investigation of P-Shell Λhypernuclei by
the (e, e’K+) Reaction
-Analysis Status of E05115Chunhua Chen（陈春花）
Hampton University
July 18,2012
The fourth workshop on hadron physics in China and Opportunities in USA
Introduction
E05115：
The 3rd generation spectroscopic investigation of Lambda hypernuclei by the
Reaction (e,e’K+) at Jlab Hall C
Merits of (e,e’K+) experiment:




Large momentum transfer → Excitation of deeply-bound state
p to  conversion → Mirror or Neutron-rich hypernuclei
Production of both spin-flip/non-flip states;
High resolution because of the quality of the CEBAF beam
Experimental Goals:


Spectroscopy of Medium - heavy hypernucleus
52Cr(e,e’K+) 52 V

Spectroscopy of Light  hypernuclei- p shell hypernuclei
12C(e,e'K+)12
ΛB
, 7Li(e,e'K+)7ΛHe,
10B(e,e'K+)10
ΛBe
, and 9Be(e'K+)9ΛLi
Calibration by the elementary process p(e,e’K+)or : H2O and CH2
Results are important in determining  , SN and V0 terms from s
states and S term from states with  at higher orbits Dr. Tang’s Talk
Experimental Setup
HES
e’
e
Virtual photon flux factor 
Splitter
Magnet
HKS
K+
Bremsstralung flux
PreChicane-SPL-(HKS+HES) Configuration
Kinematics of the E05-115 Experiment
Electron beam
Momentum: 0.844GeV/c ±17%
Angular acceptance: 3°〜9°

Momentum: 2.344GeV/c
+p →+K+
Scattered electron
Target
nucleus
Coincidence
measurement
1.5GeV γ*
p
K+
Momentum: 1.2GeV/c ±12.5%
Angular acceptance : 1°〜13°
Experimental Setup
-Detector PackageHES Detectors
EDC2
EDC1
e’
HES-D
EHOD2
EHOD1
Analysis Flow Chart
HKS
Tracking
(KDC)
TOF
(Hodoscopes)
KID
(AC,WC,LC)
Raw Data
HES
TOF
(Hodoscopes)
Tracking
(EDC)
Need to do
Geant4 Simulation
HKS
Focal Plane
(X,X’,Y,Y’,Tfp)
Data & Info
Optics
(HKS+Splitter)
HKS
Sieve Slit
Kinematics Correction
(Beam, Target effects,
Momentum, Angular)
Coincident
(RF )
Lambda&Sigma
12 Bgs Spectra
Λ
HES
Sieve Slit
HES
Focal Plane
(X,X’,Y,Y’, Tfp)
HKS
Target Plane
(X’, Y’, P, Ttar)
Optics
(HES+Splitter)
HES
Target Plane
(X’, Y’, P, Ttar)
Missing
Mass
Calibration Procedure of the Spectrometer System
Magnetic field study
Forward
Tuning
A&B&C
Field map
Geant4 Simulation
Focal plane pattern
matrices
Real Data
Initial
state
Backward
tuning
Matching level
Focal plane pattern
Matching
level
SS pattern
Nonlinear Least
Chi2 fitting
Kinematical scan
A
B
SS hole
Independent
C
level
Λ & Σ mass
Kinematical
spectroscopy
parameters
mass spectroscopy
Forward Optics Tuning
Beam
Kaon
Q2
Q1
Target
Purple:
simulation
green:
Real HES
SS data
Purple:Geant4
Real HKS
SS data Blue:
Geant4
Simulation
Splitter field contour on xoz plane
The leakage of splitter fringe field causes the cross
talk between the splitter and quadrupoles
Forward Optics Tuning
The asymmetry functions are introduced and tuned for
HKS&HES quadruple field Bx and By, independently.
The Mass Status of Forward Optics Tuning
Start Point
after forward tuning
11
Backward Spectrometer System Calibration
Spectrometer system calibration key： to reach 400 keV energy resolution
 Common splitter : Separated single arm kinematics and optics calibration is not
possible
 Technique: 2-arm coupled calibration for both kinematics and optics
Using known masses of,  from CH2 target and identified known hypernuclear
bound states 12Bgs for spectrometer calibration
HES spectrometer system
Kinematics coverage
To beam dump

HKS
HES
Sieve Slit

Splitter
Sieve Slit
Target
Beam
Kaon Momentum (MeV/c)
𝑀𝑀 = 𝑓(Ebeam , Pk , xt’k, yt’k , Pe, , xt’e, ,yt’e’ )
= 𝑓(Ebeam0 + 𝛥Ebeam0 , Pk0 +𝛥Pk0, xt’k , yt’k ,
Pe′0+𝛥Pe′0, xt’e, yt’e′)
𝑥𝑡 ′
𝑦𝑡 ′
δ
= 𝑀
=
𝑃 = 𝑃0(1+δ/100)
 Mathematical optimization by Nonlinear Least Chi2 fitting
a. Central kinematics scan (mΛ,mΣ,ΔmΛΣ)
b. Angular matrices (mΛ,mΣ,σ)
c. Momentum matrices (12ΛBgs)
d. Iteration
𝑥𝑓
𝑥𝑓′
𝑦𝑓
𝑦𝑓′
𝑀_𝑎𝑛𝑔𝑙𝑒
𝑀_𝑚𝑜𝑚𝑒𝑛𝑡𝑢𝑚
𝑥𝑓
𝑥𝑓′
𝑦𝑓
𝑦𝑓′
Preliminary status
p(e, e’K+) Λ and Σ0 (CH2 target)
Λ
Σ0
Allowing precise calibration of mass scale
Preliminary status – 12ΛB
(E05-115)
Λ𝑠
E94-107 in Hall A (2003 & 04)
Λ𝑝
Phase II in Hall C (E01~500 keV
011)
FWHM
12 B

HKS in
2005
Preliminary status –
Preliminary
-8.38MeV
10 Be
Λ
9Be+Λ
0 MeV
Cal: 8.84 MeV (without CSB)
Cal: 8.76 MeV (with CSB)
By E. Hiyama
n
Λ
α
10Be
Λ
α
p
Λ
α
α
10B
Λ
Preliminary Result - 7ΛHe
E01011 data
3/2+&5/2+
6He
Preliminary E05115
core
n

n
E. Hiyama, et al., PRC53 2078 (1996)
Preliminary status – 9ΛLi
Hall C
HKS
E05-115
~4.38
s
~3.77
s
~
2.75
~1.90
s
s
Sotona and Millener
Saclay-Lyon model for elementary process
~0.84
Ex: 0.0
B = -10.1  0.3
B = -8.530.18
(emulsion, average over
only 8 events)
Summary and to do

By current calibration method, we are able to get clear
mass spectroscopy , which is not included in the calibration
data set;

Current resolution is still factor of 2 away from expected
resolution, the iteration will continue to improve the
optical matrices as well as the kinematics;

Other issue: High multiplicity tracking problem for heavy
target data, Japanese people are still working for it.
19
Back Up
Particle ID
Online Trigger: (2/3 (𝑨𝑪𝟏 × 𝑨𝑪𝟐 × 𝑨𝑪𝟑)) × (WC1×WC2)
AC (rejecte 𝜋+> 99%), WC (rejecte p+>99%),
Offline KID: Cuts on number of photon electrons (NPE)
Optimize Cutting values – More Kaon(95%), less Pion &Proton
Experimental Setup
-Tilt Method-
𝑑5𝜎
𝑑𝜎
=Γ
Electroproduction differential cross section(Miloslav Sontana
𝑑𝐸𝑒′ 𝑑Ω′𝑒 𝑑Ω𝐾
𝑑Ω𝐾
Г : virtual photon flux
𝑑𝜎
𝑑Ω𝐾
∶Photoproduction cross section by virtual photon
7Li
E. Hiyama et al.
target :Physics of (A = 7,T=1)
PRC80,054321(2009)
M.Jurič et al., NP B52(1973) 1
7 Be

BΛ=-5.58
-3.79 (EXP)
7 Li

-4.42
Possible Charge Sym. Breaking?
-5.40 (EXP)
Λ
NO Reliable DATA
-5.40
α
Λ
7 He

n p
α
-6.39
Λ
n n
α
p
(T=1)
p
Another Physics of
7
He
HKS-HES (E05-115)
n
Unbound neutron halo
NO DATA
α
Λ
n
Bound states
n
α

n
Direct Observation of ’s glue-like role
10B
target
Millener’s parameterization(V,D,SN,S,T)
Hyperball’s  data
predicts >200keV 1-2- separation
10B(e,e’K) 10Be
Λ
10B
Λ
n
α
Λ
α
p
Λ
α
α
Cluster Calc. based on the same framework
Imperfect treatment of Tensor force?
Bad wavefunction of the core nucleus?
Coincident Trigger Set
HKS :
HES:
HKStrigger=(CP)×(K)
CP=(KTOF1X)×(KTOF1Y)×(KTOF2X)
HEStrigger=(EHODO1)×(EHODO2)
×:AND
K=WC×𝐴𝐶
Real
events
 Coincident Time:
Accidental
The correlation of HKS
target time and HES target
time, give us the
coincident spectrum:
K+
tar
Tcoin  T  T
PID cut is applied and path length correction has been done
e'
tar