Vladas Tvaskis

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Measurement of F2 and RsL/sT on Nuclear-Targets
in the Nucleon Resonance Region (Hall C,
Jefferson Lab)
Vladas Tvaskis For e02-109 e04-001
collaborations
Thanks to Robert Bradford
Jim Steinmann Ph.D thesis Student Arie Bodek
Spokesperson Eric Christy Spokesperson Thia
Keppel Spokesperson
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L/T Separated Structure Functions at low Q2 on
Nuclei (Jlab E02-109 and E04-001)
2 weeks of beam time in Hall C during Jan05
(1/3 of approved time) to measure the low Q2
(0.3 lt Q2 lt 2) part of E02-109 L/T separated
structure functions on the deuteron. E04-001
L/T separated structure functions on nuclei.
(part of JUPITER) as well as
Dedicated Low Q2 cross section measurements for
our friends in the neutrino
community. (Makoto Sakuda)
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Neutrino Experiments Need

• Neutrino experiments need good models of cross
  sections and final states to extract cross
  sections
• Neutrino Monte Carlo models must be based on
  understanding of the physics, and checked by data
  
• Reliable global models linking electron and
  neutrino scattering measurements need to be
  developed.
• Nuclear data necessary for comparison with
  neutrino measurements
• No L/T separated structure function measurements
  exist on nuclei in the resonance region
• In the resonance region, nuclear effects may be
  large, different from the DIS region, and Q2
  dependent.

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e-N Scattering
e(E)
e(E)
Born Approximation
?
sT (sL) is the Transverse (Longitudinal) virtual
photon Cross Section
Q2
N
Transverse virtual photon flux
Virtual photon polarization parameter
OR
Q2 - Negative squared mass of the virtual photon
F1(x,Q2) purely transverse
Mp - mass of the Proton
FL(x,Q2) purely longitudinal
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(No Transcript)
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Rosenbluth Separation
Method Examples
Requirements The same x, Q2 but different e.
Examples of the Rosenbluth Separation from
Experiment e94110
sL- Slope, sT - Intercept
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Jlab Hall C
Used for detection of electrons
Shielded Detector Hut
Superconducting Dipole
Target Scattering Chamber
HMS
SOS
Used for detections of positrons
Superconducting Quads
Electron Beam
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HMS Spectrometer
HMS Properties (pt-pt tune)
Vertically Segmented Hodoscope
Kinematic Range
Momentum
0.5 7.5 GeV/c
4-layer Electromagnetic Calorimeter
Angular
2 sets of vertical horizontal Drift Chambers
10.5O - 80O
Acceptance
Gas Cerenkov
O
6.5 msr
Dp/p
/-9
Resolution
Dp/p
lt 0.1
T
1 mrad
Cer Cal provide p rejection factor 10000/1 At
1 GeV

• HMS Acceptance is dominated
• by the octagonal collimator!

horizontally Segmented Hodoscope
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Kinematics Coverage

• L/T Separation Data
• Beam Energies 4.6, 3.5, 2.3, 1,2 GeV
• Targets D, C, Al, Fe
• Some H data available for crosschecks.
• Uncertainties in preliminary data estimated at
  1.6 pt-pt in e (2 normalization).

L/T separations where multiple energies.

• Low Q2 data for n modeling
• Targets H,D, C, Al
• Uncertainties in preliminary data
• estimated at 3 - 8
• (Much larger RCs and rates)

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Analysis Methodology

• Bin efficiency corrected e- yield in? dp/p?- T
• (dp/p
  /-8, ??T /-35 mrad)
• Subtract empty target background bin-by-bin.
• Subtract charge symmetric e- yield bin-by-bin.
• Apply acceptance correction for each d - T bin.
• Apply radiative corrections bin-by-bin.
• Apply T bin-centering correction and average
  over T ??for each d bin.

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Particle Identification
NPhotoelectronsgt 2
ECalo/E gt 0.7
Subsystem e- Efficiency Uncertainty
Cerenkov gt 99 0.2
Calorimeter 96.5 99.5 0.3
Tracking 90 98 0.3
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Backgrounds
Charge-Symmetric Background (measure e yields)
Background From Target Walls
Carbon EBeam 2.3 GeV
20o 30o 45o 60o
q bin-centering (finite q acceptance)
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HMS Monte-Carlo
HMS spectrometer is well understood !

• Comparison of MC to E99-118 data using E94-110
  resonance region model as a event generator.

• Excellent agreement between
  different experiments!
  
• Acceptance is determined to lt 1 pt-pt in the
  kinematics.

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Preliminary Cross Section Results
----- Input models for RCs, etc.

• Error bars are statistical only.
• Only inelastic data shown.

Deuterium Fits to previous JLab SLAC
resonance region data. Heavy targets fits to
DIS data (F2 R) y-scaling QE model.
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Cross Sections
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STATUS/SUMMARY
Expected Syst. Uncertainties

• Analysis in progress
• Calibrations is done for all runs (Final)
• Efficiencies nearly complete
• CSB complete for E2.3 Beam Energy
• CSB for other Beam energies are under way
• Working on Radiative corrections
• Iteration
• QE
• Final Cross Sections
• LT separations

Table for syst for LT separations (what we expect)
Normalization 2
Systematic uncertainty for low Q2, expected to be
higher since
Uncertainty of Charge Measurement will increase
(very low Beam Current).
Uncertainty of Radiative Corrections will
increase.
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Preliminary Data Available
Preliminary Data available for modeling in RES(W2
gt1,16 (GeV/c)2) and DIS regions on

• Hydrogen
• Deuterium
• Carbon
• Aluminium
• Iron

QE Data under way