Transcript E06-009/E04-001 update (high Q 2 data)

Experiment Rosen07: Measurement of
R = sL / sT on Deuterium in the Nucleon
Resonance Region.
 Physics
 Data Analysis
 Cross Section calculation
 L/T Separations
Ibrahim H. Albayrak
Hampton University
1
ROSEN07 and JAN05 experiments
ROSEN07 (E06-009) is the second phase of the experiment JAN05(E04-001)
with higher Q2 data.
ROSEN07 is combination of two experiments:
Measurement of R = sL / sT on Deuterium in the Nucleon Resonance
Region.(I.Albayrak)
Measurement of R = sL / sT on Nuclear targets in the Nucleon Resonance
Region.(Vahe Mamyan)
JAN05 is combination of two experiments:
Measurement of R = sL / sT on Deuterium in the Nucleon Resonance
Region.(Ya Li)
Measurement of R = sL / sT on Nuclear targets in the Nucleon Resonance
Region.(Ya Li)
2
Physics
Physics Motivation

FL, F1, F2 and R fundamental Structure Function Measurements on Deuterium.
- These structure functions provide us important information about
internal structure of nucleon, i. e. distribution of quarks and gluons
inside the nucleus.

Since these are fundamental measurements, they allow a variety of physics issues to
be addressed, such as:
–
Structure Function Moments
 Lattice QCD comparisons
 Singlet and non-singlet distribution functions
–
Quark-hadron duality studies
Neutron form factors.
–
–
3
Support Broad Range of Deuteron Physics
 Spin structure functions
 BONUS (BOund NUcleon Structure) neutron structure functions
- Hall B experiment for NEUTRON cross sections via spectator
tagging.
Physics
Structure Functions: F1, F2, FL
Calculable in Quantum
Electrodynamics (QED)
4
Physics of Interest
(Nucleon Structure)
Structure functions (F1 and F2) which have the
Information of the nucleon’s internal structure.
Physics
Rosenbluth Separation Technique:
ds
ddE
'
 (s T  s L )
Where:  = flux of transversely polarized
virtual photons
 = relative longitudinal flux
s L  FL
sL
FL
R

s T 2xF1
s T  2xF1
Transverse
2 2
5
4M x
F2  ( FL  2 xF1 ) /(1 
)
2
Q
longitudinal
Physics
Moments of the Structure Functions
Mn(Q2) = ∫dx xn-2F(x,Q2)
• The non-singlet moments can only be determined from differences of
proton and neutron moments.
• Assuming a charge-symmetric sea, n-p isolates the non-singlet
Md – 2Mp = ∫xn-2 (Fd ∙ f – 2Fp)dx
yields non-singlet distribution
•Where
• Need to pin down non-singlet (n-p) to extract singlet .
Moments Calculated on the lattice at Q2 = 4 GeV2
6
Physics
Purely New data with high Q2 above 3 GeV
New data with higher Q2
And new epsilon points for LT separation
JAN05
ROSEN07
ROSEN07 experiment is the second phase of this experiment,
the first phase was JAN05 experiment…
7
Experiment & Data analysis
Current Status and Update














8

Detector Calibrations
Kinematic Corrections
Dead Times
Efficiencies
Background Estimation and Subtraction:
Target Density Correction
Acceptance Corrections
Bin-centering corrections
Radiative corrections
Iteration Procedure
Systematic Uncertainties
Extracting Differential Cross Sections
Doing Rosenbluth L/T Separation
Moment extraction
N-p analysis
Experiment & Data analysis
Data to Monte Carlo simulation comparisons…
9
Experiment & Data analysis
Drift Chamber Positions Offsets
Significantly different from
previous data!!!
Checked optics elements, magnets
fields, matrix elements and no
difference found from previous
data.
Could it be because of DC offsets?
10
Experiment & Data analysis
Drift Chamber Positions Offsets X direction
For drift chamber position offset study I studied the width of the Elastic peak
and Xptar. The narrowest the peak the best the position. XpTar plots should not
be correlated with DC positioning.
Peak gets wider
with any x offset
No DC offset in X
(vertical) direction!
Without X pos offset
11
With X pos offset
Must be Straight. Gets
tilted with any x offset
Experiment & Data analysis
Drift Chamber Positions Offsets Y Direction
Ytar plot for Carbon
target should be narrowest
with correct positions
Without Y pos offset
With Y pos offset
There is about 0.45 mm
relative offset (distance)
between the DCs
Slope of the valley
gives the best Y offset!
12
Peak gets narrower
Experiment & Data analysis
Offsets for Drift Chamber Positions
After putting the relative offset 0.45 mm for Y position we get better comparison!
Before
After correction y pos gets narrow, which indicates that we are doing
the right thing.
13
After
Experiment & Data analysis
Target Position Study (Again)
After getting correct position information for Drift Chambers, Target position
study needed to be redone.
YData  YMC
 Z  X tan( )
cos( )
C
D2
Al
Fe
Cu
14
Del X
Del Z
(cm)
(cm)
-0.105
-0.0665
-0.116
-0.0861
-0.0764
0.0928
0.0382
0.173
0.0972
0.0749
Experiment & Data analysis
Elastic Study (Kinematic Corrections)
Two simulation runs compared with
and without radiative corrections to get
the radiative effect on peak position.
15
And correct elastic peak position
calculated after subtracting the
radiative effect.
Experiment & Data analysis
Elastic Study (Kinematic Corrections)
E 
E
W  Wdata  W proton  E
 E
E
E
There is not enough data to do a precise
kinematic offset study!
All this data is consistent with very small
(> 10-4 ) E and E’ offsets
A possible 0.3 mrad Theta
offset. On average it gives
better results.
16
Two Photon experiment has enough
number of elastic H data. They could
provide more precise results.
Experiment & Data analysis
Cross Sections Extraction Method
Monte Carlo ratio method is used to extract data cross sections:
We can simulate Monte Carlo data using a cross section model to obtain
YMC(E',q) = L* smod*( E W)*AMC(E',q)
Taking ratio to data and assuming that AMC = A, yields
ds/dWdE' = smod * (Y(E',q)/YMC(E',q))
(MC ratio method)
Peter Bosted’s model used as input model. And this data has
helped in the development of this model.
17
Experiment & Data analysis
Cross Sections (preliminary)
18
Experiment & Data analysis
And L/T Separations…
Here is some almost
final rosenbluth
separation plots for 2
different W2,Q2 pairs
Advantage of this method:
Systematic errors cancel.
sA s A
 T (1  r   )
sD s D
T
19
r  RA  RD
    /(1    RD )
Experiment & Data analysis
And L/T Separations…
Plots of R ,first one have
Q2 range 0.5-2.25 second
one Q2 range 2.25-4.5 for
Carbon.
20
Experiment & Data analysis
Summary






21 
Calibrations are done.
Charge symmetric background subtraction,
radiative corrections and other corrections
are mostly done.
Some L/T separations have already been
done (Vahe).
Continue data analysis
L/T separations
Moment extractions
n-p analysis