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Beyond the Born Approximation Measuring the Two-Photon Exchange - - PowerPoint PPT Presentation

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary Beyond the Born Approximation Measuring the Two-Photon Exchange Effect at CLAS Robert Paul Bennett Old Dominion University for The CLAS Collaboration

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Beyond the Born Approximation

Measuring the Two-Photon Exchange Effect at CLAS Robert Paul Bennett

Old Dominion University

for The CLAS Collaboration

E07-005 PANIC 2011: Cambridge, MA June 24-29, 2011

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

1 / 40

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

1 Motivation 2 Form Factors 3 TPE 4 Experiment 5 Analysis overview 6 Projections 7 Summary

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

2 / 40

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Elastic Scattering: Born Approximation

✁

q P l(k) P ′ l(k′) Γµ γµ

e-p Kinematics

k (k’): incoming (outgoing) lepton 4-vector P (P’): incoming (outgoing) proton 4-vector Single virtual photon: q2 = (k − k′)2 = −Q2, Q2 > 0 Proton remains intact

Nucleon Current Operator Γµ(q) Γµ(q) = γµF1(q2) +

1 2MN σµνqνF2(q2)

F1(q2) Non-spin flip Dirac Form Factor F2(q2) Spin flip Pauli Form Factor

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Elastic Scattering: Born Approximation

✁

q P l(k) P ′ l(k′) Γµ γµ

dσ dΩ = dσMott dΩ

  • G2

Ep(Q2) + τ ǫ G2 Mp(Q2) 1 1+τ

  • ǫ =
  • 1 + 2(1 + τ) tan2 θe

2

−1

ep Kinematics

k (k’): incoming (outgoing) lepton 4-vector P (P’): incoming (outgoing) proton 4-vector Single virtual photon: q2 = (k − k′)2 = −Q2, Q2 > 0 Proton remains intact

F1 and F2 are NOT unique

Electric form factor: GEP (Q2) = F P

1 (Q2) − τF p 2 (Q2)

Magnetic form factor: GMP (Q2) = F P

1 (Q2) + F p 2 (Q2)

τ =

Q2 4M2 P

; GEP µP ≈ GMP ≈ GD Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

How to extract G2

Ep(Q2): Rosenbluth Separation Method

Step 1: Fix Q2 Step 2: Measure dσ

dΩ at large Ee

and small θe (ǫ → 1)

dσ dΩ ∝ G2 Ep(Q2) + τG2 Mp(Q2)

Step 3: Measure at small Ee and large θe (ǫ → 0)

dσ dΩ ∝ G2 Mp(Q2)

Step 4: Subtract

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

A Better Way: Polarization Transfer

Formalism

I0Pt = −2

  • τ(1 + τ)GEpGMp tan θe

2 I0Pl = 1 M

  • τ(1 + τ)G2

Mp tan2 θe

2 I0 = G2

Ep + τ

ǫ G2

Mp

GEp GMp = − Pt Pl Ee + E′

e

2M

  • tan θe

2

  • A. I. Akhiezer and M. P. Relanko, Sov. J. Part.
  • Nucl. 3, (1974) 277 and Arnold, Carlson and

Gross, Phys. Rev. C23 (1981) 363

Method

Scatter polarized electrons off of an un polarized proton target Electron transfers spin to the proton Detect the polarization of the

  • utgoing proton

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Why this is hard:

Need polarized electrons (easy at JLab) Need to detect the proton, and then let it rescatter and remeasure it to determine the polarization (easy at JLab) Need to understand spin precession in the spectrometer Need lots of events (easy at JLab)

Why this is easy:

Almost all errors cancel in the ratio of polarizations

Hall A & C M.K. Jones et al., Phys. Rev. Lett. 84, 1398 (2000)

  • O. Gayou et al., Phys. Rev. C64, 038202 (2001)
  • O. Gayou et al., Phys. Rev. Lett. 88, 092301 (2002)
  • V. Punjabi et al., Phys. Rev. C71, 055202 (2005)

M.K. Jones et al., Phys. Rev. C74, 035201 (2006)

  • G. MacLachian et. al., Nucl. Phys. A764, 261 (2006)

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

The Proton Formfactor Puzzle

Rosenbluth Separation: (SLAC, MIT BATES, JLab et al.)

σr = dσ dΩ ε(1 + τ) σmott

  • = τG2

M + ǫG2 E

ε =

  • 1 + 2(1 + τ) tan2 θe/2

−1 τ = Q2 4M2

Separate GE and GM contributions at a particular Q2 using different beam energies and scattered electron angles GM measurement dominates at high Q2, GE is suppressed Polarization Transfer: (Hall A & C)

GE GM = − Pt Pl (Ee + Ee′ ) 2M tan θe 2

Longitudinal polarized electrons incident on proton target Measure transverse and longitudinal polarization of recoiled proton

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

The Proton Formfactor Puzzle

Rosenbluth Separation: (SLAC, MIT BATES, JLab et al.)

σr = dσ dΩ ε(1 + τ) σmott

  • = τG2

M + ǫG2 E

ε =

  • 1 + 2(1 + τ) tan2 θe/2

−1 τ = Q2 4M2

Separate GE and GM contributions at a particular Q2 using different beam energies and scattered electron angles GM measurement dominates at high Q2, GE is suppressed Polarization Transfer: (Hall A & C)

GE GM = − Pt Pl (Ee + Ee′ ) 2M tan θe 2

Longitudinal polarized electrons incident on proton target Measure transverse and longitudinal polarization of recoiled proton

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Beyond the Born Approximation

Use GM from Rosenbluth Separation and GE from Polarization Transfer To account for the difference we need a ε dependent correction to the cross section on the order of a few percent: The TPE contribution expected to be ∼ 5 − 8% We’ve known about this for a long time – Just ask Sydney Drell Phys. Rev. 113, 741744 (1959) or Leon Lederman and Mike Tannenbaum Advances in Particle Physics Vol 1 1967 pp 1–70

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Limited Previous Data

TPE was a known issue

All of the data indicated that it was small so it was ignored. Reanalysis of the existing world data (2004) shows a slight ε dependence but not well constrained. Effect increases at low ε Negligible Q2 dependence of the ratio is seen for these data. Large error bars limit our knowledge of the correction, especially at low ε and high Q2. A high precision measurement is required as TPE is only a few percent

  • f the cross section

Mixed Q2 Mixed ε

  • J. Arrington, PRC69, 032201 (2004)

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Predictions

There are several model dependent predictions of the TPE effect on the market

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Positrons to the rescue!

At leading order, the TPE term of the elastic scattering cross section changes sign as the charge of the incident beam The elastic e±p → e±p scattering contribution: σ(e±) ∝ |Aborn + · · · ± A2γ|2 σ(e±) ∝ |Aborn|2 ± 2AbornRe(A2γ) e− ↔ e+ ⇒ α ↔ −α The ratio of the cross sections isolates the TPE correction term R = σ(e+) σ(e−) = 1 − 2δ2γ δ2γ = 2Re(A2γ) Aborn We can calculate this very well (QED) Theoretical calculation of the diagram is hard : Need to integrate over all baryon states The e−P/e+P ratio provides a model independent measurement of the TPE contribution

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Jefferson Laboratory

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Continuous Electron Beam Accelerator Facility (CEBAF)

5 pass super-conducting accelerator Polarized electrons up to 6 GeV Maximum Current ∼ 100 µ A Upgrading to 12 GeV 3 experimental halls running (A, B, & C) (D is coming soon)

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

CEBAF Large Acceptance Spectrometer

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Simultaneous, Idential e+/e− Beams

Primary electron beam: 5.5 GeV and 100 nA Radiator: 1% of primary electrons radiate high energy photons Tagger magnet: Transport electrons tagger dump Converter: 10% of photons are converted to electron/positron pairs Chicane: separate the lepton beams Remaining photons are stopped at the photon blocker e+ ande− beams are then recombined and continue to the target Target: liquid hydrogen: length = 18cm (30 cm) & diameter = 6cm (6 cm) Detector: CLAS (DC, TOF) Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Simultaneous, Idential e+/e− Beams

Primary electron beam: 5.5 GeV and 100 nA Radiator: 1% of primary electrons radiate high energy photons Tagger magnet: Transport electrons tagger dump Converter: 10% of photons are converted to electron/positron pairs Chicane: separate the lepton beams Remaining photons are stopped at the photon blocker e+ ande− beams are then recombined and continue to the target Target: liquid hydrogen: length = 18cm (30 cm) & diameter = 6cm (6 cm) Detector: CLAS (DC, TOF) Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Simultaneous, Idential e+/e− Beams

Primary electron beam: 5.5 GeV and 100 nA Radiator: 1% of primary electrons radiate high energy photons Tagger magnet: Transport electrons tagger dump Converter: 10% of photons are converted to electron/positron pairs Chicane: separate the lepton beams Remaining photons are stopped at the photon blocker e+ ande− beams are then recombined and continue to the target Target: liquid hydrogen: length = 18cm (30 cm) & diameter = 6cm (6 cm) Detector: CLAS (DC, TOF) Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Simultaneous, Idential e+/e− Beams

Primary electron beam: 5.5 GeV and 100 nA Radiator: 1% of primary electrons radiate high energy photons Tagger magnet: Transport electrons tagger dump Converter: 10% of photons are converted to electron/positron pairs Chicane: separate the lepton beams Remaining photons are stopped at the photon blocker e+ ande− beams are then recombined and continue to the target Target: liquid hydrogen: length = 18cm (30 cm) & diameter = 6cm (6 cm) Detector: CLAS (DC, TOF) Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

20 / 40

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Simultaneous, Idential e+/e− Beams

Primary electron beam: 5.5 GeV and 100 nA Radiator: 1% of primary electrons radiate high energy photons Tagger magnet: Transport electrons tagger dump Converter: 10% of photons are converted to electron/positron pairs Chicane: separate the lepton beams Remaining photons are stopped at the photon blocker e+ ande− beams are then recombined and continue to the target Target: liquid hydrogen: length = 18cm (30 cm) & diameter = 6cm (6 cm) Detector: CLAS (DC, TOF) Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

21 / 40

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Simultaneous, Idential e+/e− Beams

Primary electron beam: 5.5 GeV and 100 nA Radiator: 1% of primary electrons radiate high energy photons Tagger magnet: Transport electrons tagger dump Converter: 10% of photons are converted to electron/positron pairs Chicane: separate the lepton beams Remaining photons are stopped at the photon blocker e+ ande− beams are then recombined and continue to the target Target: liquid hydrogen: length = 18cm (30 cm) & diameter = 6cm (6 cm) Detector: CLAS (DC, TOF) Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Beam Profiling

TPE Calorimeter

5x6 tower, 3.8mm × 3.8mm × 450mm Shashlik type calorimeter Located directly downstream of CLAS on the forward carriage Dense fiber monitor mounted on the face of TPEcal.

Fiber Monitors

16x16 (64x64) channel Upstream Sparse Fiber Monitor Bicron fibers spaced 5 mm (1mm) apart glued to a Hamamatsu PMT Beam size ∼ 15 mm radius Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Systematic Checks

Flipped chicane polarity about once a week Check for geometric alignment of e−/e+ on target Varied steering magnet currents Measured individual beam positions at Sparse Fiber Monitor Reproducible crossing for all chicane flips Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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The Basics

1

Measure Elastic Scattering Ratio

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

The Basics

1

Measure Elastic Scattering Ratio

R =

  • Y +

e+P

Y +

e−P

×

Y −

e+P

Y −

e−P

2

Systematics

Extensive beam profiling Flip torus polarity Flip chicane polarity Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

25 / 40

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

The Basics

1

Measure Elastic Scattering Ratio

R =

  • Y +

e+P

Y +

e−P

×

Y −

e+P

Y −

e−P

2

Systematics

Extensive beam profiling Flip torus polarity Flip chicane polarity 3

Analysis Issues

Beam energy for a given event is unknown Non-standard particle identification Different efficiency for ID’ing in-bending and out-bending tracks Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

25 / 40

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Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

The Basics

1

Measure Elastic Scattering Ratio

R =

  • Y +

e+P

Y +

e−P

×

Y −

e+P

Y −

e−P

2

Systematics

Extensive beam profiling Flip torus polarity Flip chicane polarity 3

Analysis Issues

Beam energy for a given event is unknown Non-standard particle identification Different efficiency for ID’ing in-bending and out-bending tracks 4

Analysis Solutions

Look for coplanar pairs (opposite sectors) Identify ++ and +− pairs Exploit over constrained kinematics Straight through running of primary beam Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Summary of Data Analysis

1

Trigger on particle in forward 450 and anything in opposite sector

2

Vertex cut (−45cm ≤ Vz ≤ −15cm)

3

Azimuthal angle cut (φproton − φlepton ≈ 1800)

4

Transverse Momentum cut (PT ≈ 0)

5

Beam Energy cut (Ebeam(angles) ≈ Ebeam(PConsv.))

6

Fiducial Cuts

7

DOCA cut between tracks

8

Swimming – Acceptance matching ++ and +− events

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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2006 Test Run

1.5 days of low luminosity beam

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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2006 Test Run Results

Cross Section Ratio Scale-type systematic uncert. ∼ 0.010 (e+/e- relative luminosity) Point-to-point systematic uncert. ∼ 0.0080 (acceptance & effects of cuts, coupled to statistical precision)

Maryam Moteabbed Thesis (FIU) < Q2 >= 0.206 GeV 2 Megh Niroula Thesis (ODU) World data Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Beam Line Modification for TPE

The biggest hindrance to increasing beam luminosity is the drift chamber occupancy. Extensive GEANT simulations to optimize shielding Factor of 10 in luminosity + 70 days of beam

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Q2 vs ε (TPE II 2010-2011)

ε

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

)

2

(GeV

2

Q

0.5 1 1.5 2 2.5 3

Entries 289176 Mean x 0.8662 Mean y 0.2515 RMS x 0.1233 RMS y 0.2115

1 10

2

10

3

10

Entries 289176 Mean x 0.8662 Mean y 0.2515 RMS x 0.1233 RMS y 0.2115

p Positive Torus

  • e

ε

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

)

2

(GeV

2

Q

0.5 1 1.5 2 2.5 3

Entries 286489 Mean x 0.9188 Mean y 0.1947 RMS x 0.0707 RMS y 0.167

1 10

2

10

3

10

4

10

Entries 286489 Mean x 0.9188 Mean y 0.1947 RMS x 0.0707 RMS y 0.167

p Positive Torus

+

e ε

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

)

2

(GeV

2

Q

0.5 1 1.5 2 2.5 3

Entries 368757 Mean x 0.9046 Mean y 0.2073 RMS x 0.1043 RMS y 0.1756

1 10

2

10

3

10

4

10

Entries 368757 Mean x 0.9046 Mean y 0.2073 RMS x 0.1043 RMS y 0.1756

p Negative Torus

  • e

ε

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

)

2

(GeV

2

Q

0.5 1 1.5 2 2.5 3

Entries 215888 Mean x 0.892 Mean y 0.2285 RMS x 0.08524 RMS y 0.1881

1 10

2

10

3

10

Entries 215888 Mean x 0.892 Mean y 0.2285 RMS x 0.08524 RMS y 0.1881

p Negative Torus

+

e

Preliminary

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Projections

CLAS will map out the TPE effect

  • ver large areas of Q2 and ǫ

Not the only game in town: Olympus at DESY and VEP-III at Novosibirsk 30 PAC day (Nov 2010 - Feb 2011), collected more events in 1 hour than the entire test run in 2006 CLAS will be able to obtain < 1% statistical and systematic uncertainties out to Q2 = 2GeV 2 Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Summary

Rosenbluth and Polarization transfer experiments measure GEP that differ by a factor of 3 at Q2 = 6 Understanding the origin of this discrepancy is essential to many other measurement in nuclear physics Two Photon Exchange may be able to explain the discrepancy The e+p/e−p ratio is the only way to measure the real part of the TPE amplitude CLAS was able to produce simultaneous, nearly identical beams of electrons and positrons Test run results showed promise but were severely statistics limited This year we significantly increase our luminosity, through shielding and engineering We should expect small (< 1% stat. and < 1% sys.) uncertainties for in R over a large area in Q2 − ε space

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Thank you

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Thank you

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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EBeam = MP ( 1.0 (tan(θe/2.0) ∗ tan(θP )) − 1.0) (1) EBeam = (Pz1 + Pz2) (2) EBeam = EeEp − PePpcos(θe + θp)/Mp (3)

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Beam Energy

(GeV)

beam

E

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Counts

1000 2000 3000 4000 5000 6000 7000

p: 289176 events

  • e

p: 286489 events

+

e Positive Torus (GeV)

beam

E

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Counts

1000 2000 3000 4000 5000 6000 7000

p: 368757 events

  • e

p: 215888 events

+

e Negative Torus

Very Preliminary

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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Analysis Cuts

Entries 8827351 Mean

  • 22.82

RMS 24.14

Vz (cm)

  • 100 -80 -60 -40 -20 0

20 40 60 80 100

Counts

20 40 60 80 100 120 140 160 180

3

10 ×

Entries 8827351 Mean

  • 22.82

RMS 24.14

Lepton Proton

Entries 3339875 Mean 179.9 RMS 14.27 / ndf

2

χ 1.177e+04 / 194 Prob Amp 1.038e+03 ± 5.224e+05 Mean 0.0 ± 180 Sigma 0.003 ± 1.407 a0 11.8 ± 7707 a1 0.44 ±

  • 45.46

a2 0.05 ±

  • 10.37

(deg) φ ∆

150 160 170 180 190 200 210 220

Counts

5000 10000 15000 20000 25000 30000 35000 40000

Entries 3339875 Mean 179.9 RMS 14.27 / ndf

2

χ 1.177e+04 / 194 Prob Amp 1.038e+03 ± 5.224e+05 Mean 0.0 ± 180 Sigma 0.003 ± 1.407 a0 11.8 ± 7707 a1 0.44 ±

  • 45.46

a2 0.05 ±

  • 10.37

Entries 1010907 Mean 0.004679 RMS 0.1101 / ndf

2

χ 9.629e+04 / 194 Prob Amp 8.637e+02 ± 6.349e+05 Mean 0.00004 ± 0.01894 Sigma 0.00005 ± 0.03082 a0 5.2 ± 2149 a1 4.4 ±

  • 471.8

a2 28.9 ±

  • 9670

(GeV)

T

p ∆

  • 0.5-0.4-0.3-0.2-0.1 0

0.1 0.2 0.3 0.4 0.5

Counts

10000 20000 30000 40000 50000

Entries 1010907 Mean 0.004679 RMS 0.1101 / ndf

2

χ 9.629e+04 / 194 Prob Amp 8.637e+02 ± 6.349e+05 Mean 0.00004 ± 0.01894 Sigma 0.00005 ± 0.03082 a0 5.2 ± 2149 a1 4.4 ±

  • 471.8

a2 28.9 ±

  • 9670

Entries 755182 Mean 0.0755 RMS 0.2059 / ndf

2

χ 2.615e+04 / 104 Prob Amp 7.810e+02 ± 4.861e+05 Mean 0.00011 ± 0.02758 Sigma 0.00012 ± 0.06493 a0 7.5 ± 1300 a1 7.7 ± 1225 a2 38.3 ±

  • 2905

E (GeV) ∆

  • 1 -0.8-0.6-0.4-0.2 0

0.2 0.4 0.6 0.8 1

Counts

5000 10000 15000 20000 25000 30000 35000

Entries 755182 Mean 0.0755 RMS 0.2059 / ndf

2

χ 2.615e+04 / 104 Prob Amp 7.810e+02 ± 4.861e+05 Mean 0.00011 ± 0.02758 Sigma 0.00012 ± 0.06493 a0 7.5 ± 1300 a1 7.7 ± 1225 a2 38.3 ±

  • 2905

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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SLIDE 41

Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Swimming

To reduce acceptance effects we utilize a swimming algorithm.

Reverse the charge of the detected lepton Trace track of reversed lepton through CLAS Keep tracks which would have produced a good hit in the TOF, discard the rest

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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slide-42
SLIDE 42

Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Analysis Cuts Summary

Summary of analysis cuts

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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SLIDE 43

Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Triggers

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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slide-44
SLIDE 44

Outline Motivation Form Factors TPE Experiment Analysis overview Projections Summary

Personnel

1 Spokespersons

Larry Weinstein, Brian Raue, Will Brooks, John Arrington, Andrei Afanasev & Kyungseon Joo

2 Post Docs

Puneet Khetarpal Mauri Ungaro Robert Bennett

3 Graduate Students

Dasuni Adikaram Dipak Rimal Cristian Pe˜ na Hashir Rashad

Robert Paul Bennett (Old Dominion Universityfor The CLAS Collaboration E07-005PANIC 2011: Cambridge, Beyond the Born Approximation

June 24-29, 2011

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