Adam J. Sarty Saint Mary’s University

New Polarization Measurementsin Deuteron Photodisintegration

in the 275-360 MeV range

d( , p )n Adam J. Sarty

Saint Mary’s University

representing

Jackie Glister (SMU & Dalhousie U., PhD student)

Guy Ron (Tel Aviv U., PhD student)

Ron Gilman (Rutgers U. & Jefferson Lab)

Steffen Strauch (U. of South Carolina)

Doug Higinbotham (Jefferson Lab)

Byungwuek Lee (Seoul National U., PhD student)

and the JLab Hall A “LEDEX Collaboration”

(JLab experiments E05-103 and E05-004)

The DeuteronKey in Quark/Gluon Nucleon/Meson connection

• A main focus at JLab: – understand the relation / connection between these 2

descriptive paradigms.

• Most basic “real nucleus” ( np ):– Simplicity offers hope of shedding light on the connection

• Simple reaction process: d pn

• @ High Energies (E 3 GeV):– both d and Polarization appear to show evidence of tx to

Quark/Gluon description viaDimensional Scaling (pQCD)

cm = 90

K. Wijesooriya et al. (Hall A), PRL 2002

d(,p)n :pQCD-type behaviour as E

PRC70 (2004), 014005

d/dt scale s11

Py zero

d(,p)n Quark/Gluon Nucleon/Meson connection?

• Is displayed “scaling” behaviour truly a manifestation of quark/gluon d.o.f. (pQCD)?

• Lower in excitation energy than pQCD expected to be valid…perhaps can be modeled w/ “traditional” nucleon/meson framework?

• To understand: clearly need best understanding possible of

nucleon/meson calculations at low E. Deuteron calculations at low E have been very successful … with one notable exception (30 yr problem!):inability to describe induced polarizationat excitation of few hundred MeV

d(,p)nState of Data/Theories at “Low E” (I)

• E = 300 MeV: good description of d and Polarization

• Hadronic (N / meson) theories are: Schwamb & Arenhoevel (solid line), Kang et al. (dashed)

• Schwamb & Arenhoevel “best”/most-realistic: modern NN potentials, relativistic corrections, channel coupling

E = 300 MeV

d(,p)nState of Data/Theories at “Low E” (II)

d(,p)nState of Data/Theories at “Low E” (III)

• BUT @ E = 450 MeV: clear disagreement for Py

and still no data for PXC

or PzC

E = 450 MeV

d(,p)nState of Data/Theories at “Low E” (III)

• And by E = 500 MeV:

HUGE disagreement for Py at 90 cm-angle

THUS - Our Goal:• Measure high-precision

Polarization obs. In 300-400 MeV range

• Provide clues as to what hadronic theories are missing (evidenced by Py)

NEW Data taken summer 2006: JLab, Hall ALEDEX (Low Energy Deuteron Experiments)

Py @ cm = 90

Goal of New d(,p)n Measurements:Induced Polarization

Goal of New d(,p)n Measurements:Transferred Polarization

d( , p )nPolarization Observable Definitions

“C” circular polarization of photon beam

d( , p )nExperimental Setup (“LEDEX” 2006)

d( , p )nFocal Plane Polarimeter (“FPP”)

Pztarget from component-mixing in HRS spin-transport

d( , p )nKinematics Table for LEDEX

d( , p )n ResultsInduced Polarization, Py

• Pre-existing world data shown in Blue. Our new results shown in Black (with statistical uncertainties); systematic uncertainty black strip.

• Theory curves are Schwamb & Arenhövel: dashed is more recent (from Schwamb’s habilitation, to appear in Phys. Rep.) and treats interactions in propagating NN system non-perturbatively (as opposed to approximately)

• LOWEST ENERGY: E = 277 10 MeVReasonable agreement w/ world-data + theory…theory slight over-predict’n




• ENERGY BIN #2: E = 297 10 MeV




• HIGHEST ENERGY: E = 357 10 MeVAgreement gone – data show clear evolution to “inverted shape” wrt theory;NOTE: large underestimate of theory for angles between 60 - 120


ENERGY DEPENDENCE @ cm = 90

• Increase of polarization magnitude (away from theory) shows onset clearly by 337 MeV point

• Increase in polarization steeper as f(E) than older data

• Green line is theory by Kang et al.


ENERGY DEPENDENCE @ cm = 90• When viewed on

the larger “global” energy scale …Our data can be seen to confirm the “problem” seen in earlier data (and, in fact, show the “problem” to start at lower Energy!)

d( , p )n ResultsTransferred Polarizations, Px

c and Pzc

LOWEST ENERGY: E = 277 MeV

• Reasonable agreement with Schwamb & Arenhövel calculations at lower cm-angles (a little better agreement with older calculations)

• Data show “shape change” (relative to predictions) at angle above 50 (albeit this is regime where our systematic errors grow)


c and Pzc

HIGHEST ENERGY: E = 357 MeV

• Pxc clearly shows better

agreement with Schwamb & Arenhövel’s older calculations (I’ll come back to this at end)

• Pzc has a completely

different angular-distribution “shape” than predicted (by either the old or new calculations)


c and Pzc

ENERGY DEPENDENCE @ cm = 90• Px

c approaches theory as E increases … interesting since Px

c and Py are the real and imaginary parts of the same amplitude-combination (and Py diverges from theory as E increases!)

• Pzc has same E

dependence as predicted,but it’s magnitude is consistently under-predicted.

d( , p )nSummary

• First: discussion/comparison of results to “old” (NPA 2001) vs. “new” (to appear Phys Rep). Schwamb & Arenhövel calculations:– “Old” calculations having following properties:

• parameters fixed/fit to NN-scattering and d(,p)n data (as described earlier in talk)

NN dynamics treated approximately (with a resulting violation of unitarity)

– “New” calculations having following properties:• more rigorous “conceptually”: fulfills unitarity to leading order NN dynamics treated non-perturbatively• fewer parameters to be fixed/fit: parameters fit to simultaneously

describe 7 reactions: d(,p)n , d(e,e’p)n, d(,0)d, d(,0)pn, dNN, NN NN, NN NN

• SO…newer/better, but much less parameter“freedom”

d( , p )nSummary (continued)

• Confirmed steep increase in magnitude of induced normal polarization (beyond predictions of standard MB calculations)

– rise in Py magnitude seen to start as low as ~330 MeV

• Standard MB calculations have rough agreement with new transferred polarizations at the lower energies (<300 MeV);

– agreement deteriorates for Pzc as energy goes > 300 MeV

– interestingly, agreement improves for Pxc as energy goes up (since Px

c and Py are Im and Re part of same amplitude-combo)

• Conjecture for source of discrepancies between data and MB calculations: NN-potentials used are not well-calibrated/precise at the high energies of the FSI in our reaction …

Kinematics Overview (with e-beam polarization = 38-41%):5 bins in E (20 MeV wide), 9 cm settings

d( , p )nKinematics Overview for LEDEX

d( , p )nFPP Alignment

d( , p )nFalse Asymmetry

d( , p )nMeasured Carbon Analyzing Power (Ac)

d( , p )nMeasured Carbon Analyzing Power (Ac)

New Parameterization Pubished:Glister et al., NIM A (2009)

d( , p )nMethod of Extracting Polarizations (I)

d( , p )nMethod of Extracting Polarizations (II)

Adam J. Sarty Saint Mary’s University

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