Data Analysis Strategy to Obtain High
Precision Missing Mass Spectra
For E05-115 Experiment
Spectroscopic investigation of Lambda hypernuclei in
the wide mass region using the (e,e’K+) reaction
(HKS-HES Collaboration)
Zhihong Ye
Hampton University
Feb. 16th 2010, APS Meeting, Washington DC
Outline
 Detector Calibration:
Tracking, Timing, Particle Identification
 Optics Calibration:
Splitter, HKS, HES (Angle, Momentum, Time)
 Kinematics Calibration:
Beam energy offset, target effect, center momentum and
center angle deviation.
 Flow Chart
 Current Status
Detectors Calibration
 Tracking:
--- Focal Plan Info
KDC1(6)
K+
100.2 cm
 HKS: Two identical Wire Chambers
Resolution:
Position:
Angle:
x, y ~ 0.015 cm,
x’, y’ ~ 0.3 mrad
EDC1(10)
Position:
Angle:
e’
x ~ 0.007 cm, y ~ 0.015 cm,
x’ ~ 0.5 mrad, y’ ~ 0.9 mrad
 Timing: -- Trigger, TOF
• HKS Hodoscopes: 1X(17)+1Y(9)+2X(18)
•
HES Hodoscopes: 1X(25)+2X(25)
K1X(17)
K1Y (9)
K2X(18)
K+
15.9 cm
133.6 cm
E1X (25)
E2X(25)
30.0 cm
• Time Correction:
•
Resolution:
EDC2(6)
~30.0 cm
 HES: Honeycomb Chamber + Wire Chamber
Resolution:
KDC2(6)
Pulse High Correction, Alignment, Offsets.
Single PMT ~ 110 ps,  ~ 0.025
e’
 Particle ID:
 Online Trigger: !(AC1+AC2+AC3) & (WC1+WC2)
AC (+< 99%), WC (p+< 99%),
 Offline KID:
Cuts on number of photon electrons (NPE)
Optimize Cutting values – More Kaon, less Pion & Proton
=0.027
Kaon Beta
HKS X
WC NPE
AC NPE
Optics Calibration
Optics:
Beam
Splitter
HKS / HES
K+/e’
Optics Calibration
Optics:
Splitter
Beam
HKS / HES
Reconstruction:
Angle:
 x't 
SS T
  M Splitter 
 y 't  K  / e'
Momentum: pt K
Target Time: Ttar K


/ e'
/ e'

 T 
 xSS 
FP  SS
  M HKS
/ HES 
 ySS  K  / e'


FPT

 HKS
X
/ HES
fp K  / e ' ,
fp K  / e '



FPT

 HKS
X
/ HES
fp K  / e ' ,
K+/e’
 x fp 


x
'
 fp 
y 
 fp 
 y' 
 fp  K  / e '
Optics Calibration
Optics:
Splitter
Beam
Reconstruction:
Angle:
 x't 
SS T
  M Splitter 
 y 't  K  / e'
Momentum: pt K
Target Time: Ttar K
Matrices:
M
M


/ e'
/ e'

 T 
Generated
from Geant4
simulation
P
SS T
Splitter
FP T
HKS / HES

 xSS 
FP  SS
  M HKS
/ HES 
 ySS  K  / e'


FPT

 HKS
X
/ HES
fp K  / e ' ,
FP  SS
HKS / HES
FP T
HKS / HES
fp K  / e '




K+/e’
HKS / HES

 x fp 


x
'
 fp 
y 
 fp 
 y' 
 fp  K  / e '


FPT

 HKS
X
/ HES
fp K  / e ' ,
Optimized using Sieve Slit data.
Optimized using & Spectra.
Optimized using & Spectra.
Path length correction using RF time.
Coincident
 RF Structure:
2 ns
Electron
pulse
t
Jlab electron beam has a 2ns pulse pattern.
K  / e'
tar
THKS / HES  T
 TRF
After Path length correction
RF vs HKS X
RF vs HES X
Coincident
 RF Structure:
2 ns
Electron
pulse
t
Jlab electron beam has a 2ns pulse pattern.
K  / e'
tar
THKS / HES  T
 TRF
After Path length correction
2ns
RF vs HKS X
RF vs HES X
Coincident
 RF Structure:
2 ns
Electron
pulse
t
Jlab electron beam has a 2ns pulse pattern.
K  / e'
tar
THKS / HES  T
 TRF
After Path length correction
2ns
RF vs HKS X
RF vs HES X
Real Events
 Coincident Time:
Select coincident Kaon and
electron events:

e'
Tcoin  Ttar
 TtarK
Accidental
Kinematics Calibration
Ebeam = 2.344 GeV±0.01%; Pk0 = 1.2GeV/c ± 12.5%; Pe0 = 0.844 GeV/c ±17%;
 Missing Mass:
mm  f ( Ebeam , pk , x'k , y 'k , pe ' , x'e ' , y 'e ' )
Kinematics Calibration
Ebeam = 2.344 GeV±0.01%; Pk0 = 1.2GeV/c ± 12.5%; Pe0 = 0.844 GeV/c ±17%;
 Missing Mass:
mm  f ( Ebeam , pk , x'k , y 'k , pe ' , x'e ' , y 'e ' )
 Target effect:
Due to Bremsstrahlung, Ionization, Multi-Scattering and so on..
Using SIMC (Hall-C standard Monte-Carlo simulation package), for different
targets and thickness, we have:
Ebeam  100 ~ 500KeV , Ek  40 ~ 350KeV , Ee'  40 ~ 250KeV
Kinematics Calibration
Ebeam = 2.344 GeV±0.01%; Pk0 = 1.2GeV/c ± 12.5%; Pe0 = 0.844 GeV/c ±17%;
 Missing Mass:
mm  f ( Ebeam , pk , x'k , y 'k , pe ' , x'e ' , y 'e ' )
 Target effect:
Due to Bremsstrahlung, Ionization, Multi-Scattering and so on..
Using SIMC (Hall-C standard Monte-Carlo simulation package), for different
targets and thickness, we have:
Ebeam  100 ~ 500KeV , Ek  40 ~ 350KeV , Ee'  40 ~ 250KeV
 Beam Energy Offset:
Two energy scan run: E = Ebeam ± 1.0 MeV, we have the correction function:
Eoffset  f (bpm06 x, bpm06 y, bpm12 x, bpm12 y, bpm17 x, bpm17 y)
 Central Momentum & Angle Offsets:
Magnet field setting, Installation, and Coordinate definition…
 Central Momentum:
Pk 0  Pk 0  Pk 0 , Pe 0  Pe 0  Pe 0
 Central Angle:
X 'k 0  X 'k 0  X 'k 0 , Y 'k 0  Y 'k 0  Y 'k 0
X 'e 0  X 'e 0  X 'e 0 , Y 'e 0  Y 'e 0  Y 'e 0
 Central Momentum & Angle Offsets:
Magnet field setting, Installation, and Coordinate definition…
 Central Momentum:
Pk 0  Pk 0  Pk 0 , Pe 0  Pe 0  Pe 0
 Central Angle:
X 'k 0  X 'k 0  X 'k 0 , Y 'k 0  Y 'k 0  Y 'k 0
X 'e 0  X 'e 0  X 'e 0 , Y 'e 0  Y 'e 0  Y 'e 0
Using the well-known & masses, define Chi-Square:
 2   (mm  mPDG ) 2   (mm  mPDG ) 2
And set X’k0, Y’k0, Pk0, X’e0, Y’e0, Pe0 as parameters, we can fit & data
to minimize the Chi-Square, and obtain offset values:
 2  0  Pk 0  ?, X k 0 '  ?,...
 Central Momentum & Angle Offsets:
Magnet field setting, Installation, and Coordinate definition…
 Central Momentum:
Pk 0  Pk 0  Pk 0 , Pe 0  Pe 0  Pe 0
 Central Angle:
X 'k 0  X 'k 0  X 'k 0 , Y 'k 0  Y 'k 0  Y 'k 0
X 'e 0  X 'e 0  X 'e 0 , Y 'e 0  Y 'e 0  Y 'e 0
Using the well-known & masses, define Chi-Square:
 2   (mm  mPDG ) 2   (mm  mPDG ) 2
And set X’k0, Y’k0, Pk0, X’e0, Y’e0, Pe0 as parameters, we can fit & data
to minimize the Chi-Square, and obtain offset values:
 2  0  Pk 0  ?, X k 0 '  ?,...
Missing Mass: mm  f ( Ebeam  Eoffset  Ebeam ,
pk  Pk 0  Ek , x'k  X 'k 0 , y 'k  Y 'k 0 ,
pe '  Pe 0  Ee ' , x'e '  X 'e 0 , ye' '  Y 'e 0 )
Flow Chart
HKS
Tracking
(KDC)
TOF
(Hodoscopes)
KID
(AC,WC,LC)
Raw Data
HES
Tracking
(EDC)
TOF
(Hodoscopes)
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
Spectra
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
Current Status & Plan
o We are currently working on precise calibration of all detectors.

p(e, e' K  ) / 
C (e, e' K  )12
B
12
P Shell?
G.S?
~1 MeV

To Do:
o Tracking:
Solve HES y’ problem.
o Timing:
Improve timing and TOF resolution.
o PID:
Standardize AC, WC cutting values for different targets.
o Optics:
Optimizing matrices using Sieve Slit data
o Kinematics: Improving minimization method.
Need a lot of work to reach
350 KeV!
Thank
you!