hks analysis status
DESCRIPTION
HKS Analysis Status. Lulin Yuan / Hampton University HKS Collaboration Meeting Jefferson Lab, May 16, 2008. Spectrometer System Calibration Strategy. Minimize Chisquare w.r.t reconstruction matrix M by an Nonlinear Least Square method - PowerPoint PPT PresentationTRANSCRIPT
Lulin Yuan / Hampton University
HKS Collaboration Meeting
Jefferson Lab, May 16, 2008
Spectrometer System Calibration Strategy
Minimize Chisquare w.r.t reconstruction matrix M by an Nonlinear Least Square method
Kinematics calibration: important to determine correct binding energy, energy resolution Iteration
M)|f(X=pmmwχ fpiexpi
cali
ii
22 )(
Starting optics
Calculate missing mass
Select , and hypernuclear bound states events
Minimize Chisquare w.r.t reconstruction matrix M
New optics
Better signal to background ratio
More accurate bound state mass
Iteration procedure for optical calibration
Co
un
ts (
0.3M
eV/b
in)
0AccidentalsEvents from C
p(e,e’Kp(e,e’K++))&&00 used for kinematics and optics calibration used for kinematics and optics calibration
HKS-JLABHKS-JLAB
CH2 targetCH2 target
~ 70 hours~ 70 hours
Preliminary
Preliminary = 660 keV
M = -9 keVM = -18 keV
Analysis Status
Optical reconstruction matrices and kinematics almost finalHave quick estimate of B12
ground state (GS) cross section
Finished analysis for simulated HKS data. Results of blind analysis is being compared with correct optics
Better Fitting for and 0 peaks in CH2 spectrum result in shift in binding energy for hypernuclear spectrum
Need precise energy loss correction in CH2 target and other targets in order to determine binding energy correctly
Blind Analysis
Involved B12L bound states in calibrationThe expected position and relative weights of bound states are determined
by scan to find the minimized 2:2
122
12222
PSLBGSLBΣΛwid σ+σ+σ+σ=χ
2_wid at each stage of the calibration
Blind Analysis Step by Step Result
1. initial matrix
2. involving and 3. involving B12L 2 peaks at Excitation Ex~0 and Ex~-11.5
4. involving B12L "core excited" peak at Ex~9.0
5. involving B12L " 2nd core excited" peak at Ex~5.0B12L spectrum at each stage (Ex=0 at binding energy 11.37 MeV)
Blind Analysis: Final Result
● Final matrix: 6 states are identified from simulated C12 target data, their binding energy (MeV) and relative counts to "ground state "are
11.43 ('Ground state'): counts 491
23.70 and 23.04: combined counts relative to GS 0.83
20.35: 0.29
16.70: 0.39
13.63: 0.11
The and position and counts from
simulated CH2 target:: -0.031 from PDG value, 2291 count
: 0.022, 418 count
Ex : binding energy 11.37 MeV
BetterFitting for and 0
Better fitting for and 0 peaks to improve confidence level and binding energy precision. Three fitting methods:
– G+P: Gaussian + Polynomial– AV: Gaussian + Avoigtian
– ASAV: Gaussian + Asymmetric Avoigtian
MaximumhalfWidthHalfmeanxxx
y : ,: ,)(
1022
0
factorasymmetricaxx
xxay : ,
)(
)(122
0
0
Calibration by and 0
Fit Centroid (keV) p.d.f. Confi. Level
G+P -15 1.54 0
AV -8 1.12
ASAV -85 0.86 0.85
0Fit
Centroid (keV) p.d.f. Confi. Level
G+P -12 1.27 0
AV -11 1.18
ASAV -84 1.17 0.15
L Fit
Average Cross section: B12 GS
Quick estimate of B12 GS cross section as the average of 5 C12 run periods
Set# 1 2 3 4 5 6
HKS Tracking 0.93 0.90 0.93 0.89 0.90 0.92
Enge Tracking 0.72 0.66 0.85 0.91 0.92 0.91
AC Cut 0.81 0.82 0.86 0.90 0.95 0.97
WC Cut 0.90 (for all data sets)
Cut 0.93 0.87 0.95 0.93 0.98 0.98
Computer Live 0.90 0.90 0.94 0.92 0.90 0.93
K Absorption 0.975
K Decay 0.345
Beam Charge(mC) 618.5 0.115 0.184 0.158 0.210 0.226
GS Count 26 0 322 77 30 202
Integrated VPF 4.805E-6
Averaged HKS Solid angle 15 msr
Cross section ddL (nbar/sr)
135.5 0 115.7 161.7 94.0 85.6
*Correction factors, solid angle and VPF Based on Okayasu’s PhD Thesis
Average Cross section: B12GS
Averaged B12GS cross section (0-13 degree average)
ddL = 103.1±5.7 (stats)(nbar/sr)
HNSS (E89-009) (0-4.6 degree average):
ddL = 155.0±24 (stats)(nbar/sr)
C12 Run Period
dd
L(n
bar/
sr)
Average Cross section
K+ Scattering Angle(degree)