APS Meeting, April 30 2011

Exclusive π0 electroproductionin the resonance region at high Q2.

Maurizio Ungaro, Kyungseon Joo

University of ConnecticutJefferson Laboratory

for the CLAS collaboration

1M.Ungaro

APS Meeting, April 30 2011 2

Resonance Discoveryp+ + P p+ + P p- + P p- + P

p- + P p0 + N€

13A3 / 2 + 2

3A1/ 2

€

A3 / 2

€

23

(A3 / 2 − A1/ 2)

s++:s--:s-0 = 9:1:2

€

dσdΩ

= a + bcosθ + c cos2θ

€

L2I 2J = P33

M.Ungaro

$1750

$200

Search for Quarks

Friday, May 19, 1967

Beyond CQM

gg

1,0

Constituent Counting Rule:

€

A12∝1/Q3

A32∝1/Q3

GM* ∝1/Q4

APS Meeting, April 30 2011 5M.Ungaro

Map the NN* electrocouplings as a function of photon virtuality with a combined analysis of electroproduction channels

Access active degrees of freedom at various distances

Explore the non-perturbative strong interactions responsible for nucleon formation and the origin of quark confinement

N* Program in CLAS

Investigate the origin of 98% of nucleon mass through DCSB

JLABCarnegie Mellon

Univ. of MarylandTrinity College (Dublin)

DSE FrameworkDCSBLCSR

Dist. Amplitudes

Form Factors

APS Meeting, April 30 2011 Williamsburg, VA 6M.Ungaro

p+ in the resonance region

Q2: 1.6 5.4 GeV2

W: 1.1 1.8 GeV58000 data points

High Q2 p electroproduction

e

e’

γv N*, △*

p+, p

n, p’p

Single p+, p production p in the Delta

Q2: 2 6.5 GeV2

W: 1.1 1.4 GeV7200 data points

Missing:p in the resonance region

Q2: 2.0 6.5 GeV2

W: 1.1 2.0 GeV~75000 data points

No prior data

h electroproduction from the same dataset1.1 W 2.0

0

Q

2

6

M. Ungaro Phys.Rev.Lett.97:112003,2006

K. Park Phys.Rev.C77:015208,2008I.G. Aznauryan Phys.Rev.C78:045209,2008

Nick Markov, UCONN

This analysis

APS Meeting, April 30 2011 Williamsburg, VA 7

Experiment Overview

N

s s(W,Q2,cos(q*))

ds/dWp = sT + esL + esTTcos2f + √2e(e+)sLTcosf + h√2e(e-1)sLT’sinf

M.Ungaro

Detect:Electron, Proton

Will Extract:

• Cross sections, Structure Functions

• Beam Spin Asymmetries• Helicity amplitudes and their

Q2 dependence

APS Meeting, April 30 2011 Williamsburg, VA 8M.Ungaro

B.H. Separation:The typical angle between the emitted photon and the electron in B.H. processes is θ m/E∼

Analysis Overview

APS Meeting, April 30 2011 9M.Ungaro

45 bins in W, DW=20 MeV7 bins in Q2 DQ2/Q2 ~ 0.18

10 bins in cos(q*)24, 48, 96 bins in f*

W [GeV]

Q2

[GeV

2 ]

W=1.59 Q2=3.5

Total: 75600 CS points

p0 Analysis Overview

APS Meeting, April 30 2011 Williamsburg, VA 10M.Ungaro

Preliminary Results

aTL +ess

€

sLT =b

sinθ 2ε (ε +1)

TTT

cqe

s 2sin

ds/dW* = sT + esL + esTTcos2f + √2e(e+1)sLTcosf

240 pointsout of 75K

CLAS P

relim

inary

APS Meeting, April 30 2011 Williamsburg, VA 11M.Ungaro

Preliminary Resultsds/dW* = sT + esL + esTTcos2f + √2e(e+1)sLTcosf

240 pointsout of 75K

CLAS P

relim

inaryaTL +ess

€

sLT =b

sinθ 2ε (ε +1)

TTT

cqe

s 2sin

APS Meeting, April 30 2011 Williamsburg, VA 12M.Ungaro

Preliminary Resultsds/dW* = sT + esL + esTTcos2f + √2e(e+1)sLTcosf

CLAS P

relim

inary

aTL +ess

€

sLT =b

sinθ 2ε (ε +1)

TTT

cqe

s 2sin

APS Meeting, April 30 2011 Williamsburg, VA 13M.Ungaro

Preliminary Resultsds/dW* = sT + esL + esTTcos2f + √2e(e+1)sLTcosf

CLAS P

relim

inary

aTL +ess

€

sLT =b

sinθ 2ε (ε +1)

TTT

cqe

s 2sin

APS Meeting, April 30 2011 Williamsburg, VA 14M.Ungaro

Preliminary Resultsds/dW* = sT + esL + esTTcos2f + √2e(e+1)sLTcosf

CLAS P

relim

inary

aTL +ess

€

sLT =b

sinθ 2ε (ε +1)

TTT

cqe

s 2sin

APS Meeting, April 30 2011 Williamsburg, VA 15M.Ungaro

Preliminary Resultsds/dW* = sT + esL + esTTcos2f + √2e(e+1)sLTcosf

CLAS P

relim

inary

aTL +ess

€

sLT =b

sinθ 2ε (ε +1)

TTT

cqe

s 2sin

APS Meeting, April 30 2011M.Ungaro 16

Summary, OutlookCL

AS Pre

limina

ry

To do list:JANR, DR (Being Done)SAID analysis

Review:p0 (by this summer)h (by this fall/winter)

The combined analysis of single and double meson channels is key to the N* program and to provide a high definition picture of the nucleon

Explore the non-perturbative strong interactions responsible for nucleon formation and the origin of quark confinement

APS Meeting, April 30 2011 17

Backup Slides

M.Ungaro

APS Meeting, April 30 2011 Williamsburg, VA 18M.Ungaro

exclurad (Afanasev, Akushevich, Burkert, Joo)

Input: Exclusive cross section

No peaking approximation No soft-hard photon discrimination Radiation of 4 SF with angular dependence of each one (exclusive electroproduction)

Radiative Correction

W=1.29

Analysis Overview

APS Meeting, April 30 2011 Williamsburg, VA 19M.Ungaro

exclurad (Afanasev, Akushevich, Burkert, Joo)

Input: Exclusive cross section

No peaking approximation No soft-hard photon discrimination Radiation of 4 SF with angular dependence of each one (exclusive electroproduction)

Radiative Correction

W=1.63

Analysis Overview

APS Meeting, April 30 2011 Williamsburg, VA 20M.Ungaro

S1 S2

S3

S5 S6

S4

Normalization check: Good electron PID, fiducial cut Good acceptance from simulation Vertex Correction, Cuts Kinematic Corrections Elastic Scattering Inclusive scattering

Data Keppel Brasse

W [GeV]

W [GeV]

W [GeV]

W [GeV]

W [GeV]

W [GeV]

Analysis Overview

APS Meeting, April 30 2011 Williamsburg, VA 21M.Ungaro

Data:

Electron ID Proton ID Vertex Correction, Selections Electron Fiducial Cut Proton Fiducial Cut Electron Momentum Correction Proton Momentum Correction Normalization Check Radiative Correction Bin Averaging Correctionp0, h selection

Simulation:

Electron ID Proton ID Vertex Correction, Selections Electron Fiducial Cut Proton Fiducial Cut Timing Resolution Match Momentum Resolution Match Acceptance Correction

To do list:Finalize Systematic ErrorsCollaboration ReviewAmplitudes extraction (JANR, DR, SAID)

Analysis Overview

APS Meeting, April 30 2011 Williamsburg, VA 22M.Ungaro

24 f bins200M Generated Events

MAID2007AAO_RAD

Electron ID Proton ID Vertex Correction, Selections Electron Fiducial Cut Proton Fiducial Cut Timing Resolution Match Momentum Resolution Match Drift Chamber Efficiencies p0 selection

Analysis Overview

APS Meeting, April 30 2011 Williamsburg, VA 23M.Ungaro

Analysis Overview

96 f bins200M Generated Events

MAID2007AAO_RAD

Electron ID Proton ID Vertex Correction, Selections Electron Fiducial Cut Proton Fiducial Cut Timing Resolution Match Momentum Resolution Match Drift Chamber Efficiencies p0 selection

APS Meeting, April 30 2011 Williamsburg, VA 24M.Ungaro

What about h?

eP missing mass2 [GeV2]

p0

h

APS Meeting, April 30 2011 Williamsburg, VA 25M.Ungaro

What about h?

25 bins in W, DW=20 MeV7 bins in Q2 DQ2/Q2 ~ 0.18

10 bins in cos(q*)24 bins in f*

W [GeV]

Q2

[GeV

2 ]

W=1.53 Q2=3.0

Total: 43750 points

h

W [GeV]

Q2

[GeV

2 ]

W=1.65 Q2=3.0

W [GeV]

Q2

[GeV

2 ]

W=1.79 Q2=3.0

W [GeV]

Q2

[GeV

2 ]

W=1.95 Q2=3.0