F 2 and R in Deuterium
Download
Report
Transcript F 2 and R in Deuterium
Experiment Rosen07: Measurement of
R = sL / sT on Deuterium in the Nucleon
Resonance Region.
Physics
Experiment Setup
HMS Detectors
Calibrations
Data Analysis
Cross Section calculation
Ibrahim H. Albayrak
Hampton University
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Physics
e
e
q
g
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Physics
Structure Functions: F1, F2, FL
Calculable in Quantum
Electrodynamics (QED)
Physics of Interest
(Nucleon Structure)
Structure functions (F1 and F2) which have the
Information of the nucleon’s internal structure.
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Physics
Rosenbluth Separation Technique:
ds
ddE
'
(s T s L )
Where: = flux of transversely polarized
virtual photons
= relative longitudinal flux
sL
FL
R
s T 2xF1
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
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
Singlet and non-singlet distribution functions
Lattice QCD comparisons
–
Quark-hadron duality studies
Neutron form factors.
–
–
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.
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Physics
FL, F1 , F2 structure functions
FL (1
longitudinal
4M 2 x 2
Q
2
Transverse
) F2 2 xF1
MIxEd
F1 is transverse structure function
F2 is mixed structure function
• describes the momentum distribution of the quarks inside the
nucleon.
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Physics
This Data Provides Constraints on Gluon Distributions in two Ways:
1- FL can probe the gluon distributions…..
FL(x,Q2) = (as(Q)/2p)x2 dy/y3 [8/3F2(y,Q2) + 2∑ei2(y-x)g(y,Q2)] + …
2- n-p provides non-singlet and therefore singlet
• Nucleon structure composed of singlet (gluons, sea) and non-singlet
(valence) distributions
•At moderate x (~ 0.3), singlet comparable to non-singlet
= > Singlet and non-singlet separation provides extra constraint on
gluon distribution.
• 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
∫(Fd – 2Fp)dx yields non-singlet distribution
• Need to pin down non-singlet (n-p) to extract singlet .
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Physics
Moments of the Structure Functions
Mn(Q2) = ∫dx xn-2F(x,Q2)
Moments Calculated on the lattice at Q2 = 4 GeV2
For proton, n= 2 F2 moment = 0.182 +/- 0.006
For deuteron, n=2 F2 moment / nucleon = 0.165 +/- 0.008
Since Lattice calculates only valence quarks, singlet/non-singlet
separation allows for precise Lattice comparisons.
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Physics
New data with high Q2 above 3 GeV
And new epsilon points for LT separation
JAN05
ROSEN07
ROSEN07 experiment is the second phase of this experiment,
the first phase was JAN05 experiment…
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Current Status and Update
Detector Calibration
Calorimeter Eff.
Cerenkov Eff.
Tracking Eff.
Trigger Eff.
Computer Dead Time
Acceptance Corrections
Beam Position Stability Study
Beam Position Offsets
Target Position Offsets
Optics Checks
Charge Symmetric Background
Radiative Corrections
Cross Sections
Completed
Completed
Completed
Detailed study in progress
Detailed study in progress
Detailed study in progress
Needs to be redone
Completed
Needs to be redone
Needs to be redone
Preliminary Checks
Completed
Iterating
Iterating
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Charge Symmetric Background Subtraction…(From Vahe)
Cross Section(CS) fit function has
exponential form, with constraint
CS=0 at E’=Ebeam.
s ( E ,q const ) log( C ) (exp( S ( Ebeam E )) 1)
Cross section is interpolated by a polynomial in
theta and used in CSB subtraction.
Cerenkov Center Efficiency Correction…
Position dependency of
Cerenkov efficiency
1/Eff
#PE>1
Corr < 0.5%
#PE>2
Corr ~ 2%
dp/p
This effect is bigger than we had in Jan05.
That might be because cerenkov had been
moved between the two experiments.
Due to the gap between the cerenkov mirrors,
there is an efficiency problem in the center
region.
dp/p
1/Eff
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Cerenkov Center Efficiency Correction…
Before the correction
After the correction
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Data to Monte Carlo simulation comparisons…
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Preliminary Drift Chamber Position Studies
Significantly different from previous
data!!!
Checked optics elements, magnets
fields, matrix elements and no
difference found from previous data.
FPP was tested before ROSEN07.
Would detector positions have been
effected by all that weight on
detector frame?
Could it be because of DC offsets?
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Preliminary Drift Chamber Position Studies
Center pos of
Jan05 data
Center pos of
ROSEN07 data
Dx
Dy
Dx_DC2=0.45 cm
Dy_DC1=0.33 cm
Dy_DC2=0.30 cm
ROSEN07
x and y positions of drift
chambers of old (Jan05)
and new (Rosen07) data
compared to find the
amount of shift.
Dx_DC1=0.70cm
JAN05
Mean = 0.34
Mean = 0.01
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Preliminary Drift Chamber Position Studies
Point target study [1% RL Carbon target]
Before
After DC position adjustment in replay:
1-Y/ tar comparison gets better,
2- Ytar becomes narrower,
After
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
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*( DE DW)*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.
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Cross Sections (preliminary)
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Cross Sections (preliminary)
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
And L/T Separations…
Here is some
preliminary L/T
separations from
Vahe Mamyan.
Ibrahim H. Albayrak, January 2009 HallC Collaboration Meeting
Experiment & Data analysis
Summary
Calibrations are done.
Charge symmetric background subtraction,
radiative corrections and other corrections
are mostly done.
Some preliminary L/T separations have
already been done (Vahe).
Continue data analysis
L/T separations
Moment extractions
n-p analysis