Recoil Polarization Measurements in

0 Electroproductionat the Peak of the (1232)

Recoil Polarization Measurements in

0 Electroproductionat the Peak of the (1232)

By:By:

Adam J. SartyAdam J. Sarty

On behalf of the Hall A andOn behalf of the Hall A and E91-011 Collaborations E91-011 Collaborations

NSTAR2001NSTAR2001

Workshop on the Physics of Excited NucleonsWorkshop on the Physics of Excited Nucleons

University of MainzUniversity of Mainz

March 7-10, 2001March 7-10, 2001

A Status ReportA Status Report

(and some Preliminary Results)(and some Preliminary Results)

From JLab E91-011 in Hall AFrom JLab E91-011 in Hall A

Acknowledgments: Acknowledgments: This Experiment (E91-011) ran in Hall A from This Experiment (E91-011) ran in Hall A from

May 19 – August 31, 2000.May 19 – August 31, 2000.

This talk is possible due to the contributions This talk is possible due to the contributions and hard work of many collaborators…and hard work of many collaborators…

The Other Co-Spokespeople:The Other Co-Spokespeople:

• Jim Kelly (Maryland), Jim Kelly (Maryland), Salvatore Frullani (INFN)Salvatore Frullani (INFN)

• Robert Lourie (Rentec) – Robert Lourie (Rentec) – spokesperson spokesperson EmeritusEmeritus

The Hardworking PhD Students:The Hardworking PhD Students:

• Rikki Roche’ (FSU)Rikki Roche’ (FSU)

• Zhengwhei Chai (MIT)Zhengwhei Chai (MIT)

• Stephanie Escoffier (Saclay)Stephanie Escoffier (Saclay)

And Postdocs who led (leading!) the effort:And Postdocs who led (leading!) the effort:

• Mark Jones (Maryland, now JLab)Mark Jones (Maryland, now JLab)

• Dave Meekins (FSU, now JLab)Dave Meekins (FSU, now JLab)

…and the rest of the Hall A Collaboration participants:…and the rest of the Hall A Collaboration participants:

How can 1 more measurement in Hall A How can 1 more measurement in Hall A contribute to the “N-contribute to the “N-” problem?” problem?

How can 1 more measurement in Hall A How can 1 more measurement in Hall A contribute to the “N-contribute to the “N-” problem?” problem?

Given this is the 5th N- talk in a row, I’ll skip the “Motivation” discussion driving the interest to isolate S1+ and M1+ (and other!) contributions in e+p e+p+0 at W=1232!

Focal Plane Polarimeter:(FPP)

Tools in Hall A:• 2 Hi-Res Specs

(6 msr each)• FPP• High I, high Pol.

cw beam• 15 cm LH2

cryotarget

• E0 up to 5 GeV

Hall A

Measurement Philosophy:Measurement Philosophy:Measurement Philosophy:Measurement Philosophy:

• High-resolution High-resolution recoil polarizationrecoil polarization measurements should be done at measurements should be done at selected kinematic regions for selected kinematic regions for stringent evaluation of multipole stringent evaluation of multipole amplitudes.amplitudes.

• Access to Access to unique multipole unique multipole combinationscombinations and phase information and phase information not available with other methods.not available with other methods.

• Complement the CLAS multipole Complement the CLAS multipole extractions via a more extensive extractions via a more extensive “energy independent” analysis.“energy independent” analysis.

• Power of recoil-pol technique demonstrated with “single point” measurements from Bates (Warren, Warren, 9898) and Mainz (Schmeiden, 00Schmeiden, 00)

(or: “why do we need this, given all that extensive Hall B data?”)

Our Choice of Q2 compared toExisting Data for EMR & SMR:Our Choice of Q2 compared to

Existing Data for EMR & SMR:

Specific Measurements:Specific Measurements:• Angular Distribution of diff. Cross sections

and Recoil Polarization in p( e,ep( e,e´́p )p )00

• Allows for multiple Response Function extraction.

CENTRAL PRODUCTION KINEMATICS:

(1 electron setting, 12 proton settings)

Accessible Response Functions:Accessible Response Functions:

Phase-Space Coverage AchievedPhase-Space Coverage Achieved

• ““in-plane” part only allows extraction of in-plane” part only allows extraction of distributions for distributions for 6 responses6 responses

• Extended “out-of-plane” acceptance (from Extended “out-of-plane” acceptance (from cm-lab boost) provides potential access to cm-lab boost) provides potential access to several more.several more.

• Each response: unique combination of Each response: unique combination of contributing multipolescontributing multipoles

• Unique access to Unique access to imaginary imaginary part of part of multipole interferences – multipole interferences – phase phase info. info.

cm

Evaluation of Expected Sensitivity to SMR:

Evaluation of Expected Sensitivity to SMR:

• Above “sensitivity checks” done by using a simple isobar-model (JJ Kelly’s “eipiprod”), and allow SMR to vary away from VPI (SAID) database values.

• 4 graphs outlined in GREEN are the Responses accessible IN-PLANE.

Evaluation of Expected Sensitivity to EMR:

Evaluation of Expected Sensitivity to EMR:

• Above “sensitivity checks” done same way as previous slide’s SMR checks.

• Basically NO SENSITIVITY to EMR.

Symmetries and Redundancies in Multipole Analysis

Symmetries and Redundancies in Multipole Analysis

From The Experiment:From The Experiment:• Beam Polarization mid-high 70%’s• Average current (whole run) = 45 A

(143 Coulombs)

Current:

for mid-Juneto August

LuminosityMonitoring:

108.2 A, P=79%

Sample Spectra #1:Background Subtraction

Sample Spectra #1:Background Subtraction

Sample Spectrum #2:Proton/Pion SeparationSample Spectrum #2:

Proton/Pion Separation

Sample Spectum #3:Separation from Elastic Radiative Tail

Sample Spectum #3:Separation from Elastic Radiative Tail

cm = -50°

• Radiative Tail from elastic peak only present in TWO of the 12 proton settings: for cm = -50° and cm = -90°

Sample Spectrum #4:Sample Spectrum #4:

Sample Spectra #5:Data compared to MAID (input generator

for acceptance Monte-Carlo routine)

Sample Spectra #5:Data compared to MAID (input generator

for acceptance Monte-Carlo routine)

Data in RED

MAID (+M.C.) in BLUE.

Various spec.Distributions(y, tgt , tgt, p)For both e and pSpectrometers.

WDistribution

cm = 50°

FPP (Polarimeter) Performance Checks using H(e,e’p) Elastic

FPP (Polarimeter) Performance Checks using H(e,e’p) Elastic

• Performed several dedicated elastic scattering runs with proton momenta spanning range of production settings

• Used to check/calibrate “false” (instrumental) asymmetries in FPP.

• Can also use Radiative Tail in acceptance of production kin. cm = -90° to check same.

False Asym. Distributions in FPP

FPP (Polarimeter) Performance Checks using H(e,e’p) Elastic #2:

Extracting GE / GM

FPP (Polarimeter) Performance Checks using H(e,e’p) Elastic #2:

Extracting GE / GM

Preliminary

From rad.-tail

Dedicated elasticrun

• Comparison to (Black points) elastic measurement E93-027 made with same device:M.K. Jones et al, PRL 84, 1398 (2000)

Planned Analysis Method:Response Function fit to Focal Plane Polarizations

Planned Analysis Method:Response Function fit to Focal Plane Polarizations

Monte-Carlo Evaluation of Planned Response-Function Extraction

Method:

Monte-Carlo Evaluation of Planned Response-Function Extraction

Method:

PreliminarySimulation Study

This is NOT data!

• Use M.C. (MAID input) to simulate expected focal plane pol. distributions.

• Extract Resp. Fn’s by directly fitting distribution of focal-plane polarizations.

• Compare to input MAID calc’s…mostly OK, still needs a little study.

Monte-Carlo Evaluation of Planned Response-Function Extraction Method #2:

Monte-Carlo Evaluation of Planned Response-Function Extraction Method #2:

PreliminarySimulation (NOT data!)

Preliminary (“On-Line”) Results: Sample #1

Preliminary (“On-Line”) Results: Sample #1

Preliminary (“On-Line”) Results: Sample #2

Preliminary (“On-Line”) Results: Sample #2

Preliminary (“On-Line”) Results: Sample #3

Preliminary (“On-Line”) Results: Sample #3

Summary:Summary:Summary:Summary:• p( e,ep( e,e´́p )p )00 has been measured for 12 has been measured for 12

angular settings, spanning the full range angular settings, spanning the full range on either “side” of q.on either “side” of q.

• Measurements centered at pole of Measurements centered at pole of (1232) (1232) excitation and at Qexcitation and at Q22 = = 1.0 GeV1.0 GeV2 2

• Preliminary analysis shows there should be no Preliminary analysis shows there should be no problems extracting several response problems extracting several response functions, including those beyond the 6 in-functions, including those beyond the 6 in-plane responses, due to large plane responses, due to large acceptance. acceptance.

• ““On-Line” polarizations show marked On-Line” polarizations show marked deviations from that expected (from MAID deviations from that expected (from MAID or SAID).or SAID).

• Could be first hint at the sensitivity of this Could be first hint at the sensitivity of this technique for accessing otherwise technique for accessing otherwise “hidden” multipole information.“hidden” multipole information.

• Need to await completion of analysis to Need to await completion of analysis to make firm statements / conclusions.make firm statements / conclusions.

• Potential exists now to extend Potential exists now to extend technique to other (higher) Qtechnique to other (higher) Q22 and/or to and/or to off-peak W-values.off-peak W-values.

Focal-Plane Polarizationsto

Reaction-CM Polarizations

Focal-Plane Polarizationsto

Reaction-CM Polarizations

Very PreliminaryCross Section Results:

Very PreliminaryCross Section Results:

Spin Precession through HRS

Spin Precession through HRS