CLAS Approved Analysis Proposal. Out-of-plane Measurements of the Structure Functions of the Deuteron

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1 CAS Approved Analysis Proposal Out-of-plane Measurements of the Structure Functions of the Deuteron G.P.Gilfoyle University of Richmond W.K.Brooks, B.A.Mecking Jefferson ab S.Kuhn,.Weinstein Old Dominion University M.F.Vineyard Union College Physics Motivation Formalism Current Status xtracting Structure Functions with CAS Preliminary Results Conclusions

2 Physics Motivation. Can the deuteron be understood with the coherent hadronic model of nuclear physics? Can we properly incorporate relativistic effects into our description of the deuteron and few-body nuclei? Can we account for final-state interactions (FSI)? What other effects are needed (meson-exchange currents, isobar configurations, etc.)? These were raised as Key Questions in the PAC Few-Body Workshop.. How do we distinguish between quark-gluons effects and the less-well-understood effects of conventional nuclear physics in the GeV energy region? 3. The fifth structure function (the imaginary part of the longitudinal-transverse interference) can be investigated only with out-of-plane measurements and is largely unexplored territory.

3 > > 4 Kinematics and Formalism Kinematics: e Scattering Plane Cross section:! #"%$ -+./ '& $ #"(& )+*#, $ 4-+./ && )*3, $ 5 "(&,7698 e θ φ e pq -+./ ( ω, q ) q Reaction Plane p Missing momentum: ;: < =.. Conventional asymmetries are proportional to the corresponding structure function: "(& && 3? = A@BC?? 3? $ A@BD? = 4? $ " F " $ 3I7? I7? "(&GFH"(& & F & $ " F " $ &&JFK&& && F && & F & > "(& M I7? = ON I7? M I7? $ ON I7? "PFH" $ F "(& &JFK& = &&JFK&& Subscripts - -Q./. Superscripts - beam helicity.

4 Current Status Some measurements have already been made for =, but suffer from limited statistics or angular range. The plot is from S.Gilad, et al., NP A63, 76c, Hall A experiment - will determine cross sec 4. tions and 3"(& at,, Hall A experiment - will measure struc all five. ture functions near threshold at ν (GeV) This project will analyze data from the 5 run period. 4 ed e X blue GeV green -.56 GeV red -.56 GeV, reversed field Q (GeV/c)

5 Physics Program Measure > "(& from O in quasi-elastic kinematics in the region 4 =. Quasielastic kinematics are better understood. Use missing mass to identify the neutron. Fifth structure ( > "(& ) function analysis. Use -,D6 8 and/or fits to the helicity asymmetry to extract > "(&. K and K? reactions to test algorithms. Cross checks with different running conditions. Comparison with theoretical calculations. Corrections, uncertainties, etc.. Measure the fifth structure function at higher dip region., i.e., the Do other structure functions > "(& and > &&. More vulnerable to acceptance effects.

6 xtracting Structure Functions with CAS Measuring O Use missing mass technique to isolate neutrons. ) 3 ) 3 Missing Mass (GeV/c.5 ed e px.6 GeV, reversed field 3 Missing Mass (GeV/c (deg) 4. GeV (deg) Neutrons are clearly visible (.6 GeV, normal polarity).

7 ( > 7 xtracting Structure Functions with CAS For electrons. Data Selection and Corrections Good CC, C, SC status,, nergy-momentum match $#&% ' ) *% Reject pions and (! " C fiducial No tracks within ',+ of the end of a strip lectron fiducial Quasi-elastic scattering Modified e cut, Gegham Asryan fits!-.*/ 3!-45/ 6 For protons. Proton fiducial cut 9 vertex cut 798;:=< ;>? Modified e cut A@B6CDB 8:6< + For neutrons. Missing mass cut F- G/ *HI J J H* F- KG/ H lectron momentum corrections are small. Beam charge asymmetry..6 GeV, reversed field:.6 GeV, normal field:!- - NMPO! 4!- - QO! 4 Beam polarization. All Runs R4 " O F.S4

8 How high in./ can we go? 3 Missing Mass versus CM x o o MM (GeV) o o o o MM (GeV) MM (GeV) Missing mass spectrum for field, not acceptance corrected.,.558 GeV, normal

9 How high in : can we go? Missing Mass versus p m 3 Missing Mass versus p m x.6 GeV, normal field p m =.-. GeV/c Missing Mass versus p m Missing Mass versus p m 5 p m =.7-.8 GeV 5 p m =.4-.5 GeV/c Thu Jan 3 6::4 3 Missing mass spectrum for field, not acceptance corrected.,.558 GeV, normal

10 N + +,,,D / Moments Analysis For > "(& Recall! #"$ et % & '"() * +, -! '". *, + /! '". 3 For a sinusoidally-varying component to the acceptance % & '"()@? %! #"() %! '"7 ) 6 8:9<;=; 6 A "CB %! '"7D)<? > 54 %! #"() Preliminary results for.56 GeV, normal field, not acceptance corrected,? B F KM3NPÖ QR H,?S IT F UWV <;=; <sin(φ)> versus for h= θ (deg) Acceptance Correction from Sum θ (deg) pq pq <sin(φ)> versus for h= θ (deg) A T from Difference (deg) pq

11 Other Moments for > "(& and > && Recall! #"$ In a way similar to relating %! #"7 ) and 6 % ) 4 6 and % )P 6 Preliminary results for.56 GeV, normal field, not acceptance corrected,? B F KM3NPÖ QR H,?S IT F U V -.5 <cos(φ)> <cos(φ)> These asymmetries are large, but are not corrected for acceptance.

12 ? N 4 Helicity Asymmetry Analysis for > "(& Recall Define 6 3? in a more general way.,, 6 & '"(! #"7 3 D! #"$ - Preliminary results for.56 GeV, normal field, not acceptance corrected,? B F KM3NPÖ QR H,?S IT F UWV (N -N )/(N +N ) vs. φ pq o o = (N -N )/(N +N ) vs. φ pq o o = χ / ndf / 8 p -.56 ± χ / ndf.64 / 8 p.574 ± (N -N )/(N +N ) vs. φ pq o o = (N -N )/(N +N ) vs. φ pq o o = χ / ndf 3.45 / 8 p -.44 ± χ / ndf / 8 p ±

13 Comparison of Different Analysis Methods for > "(& A T from <sinφ> (deg) A T from fit to helicity asymmetry (deg) The shapes and uncertainties are consistent. We can measure small > "(&..56 GeV, normal field, not acceptance corrected,,.

14 ? Analysis Comparison with analysis of K. Joo and C. Smith to measure > "(& in the resonance region at.5 GeV. Bethe-Heitler events overlap with missing mass of?. Use kinematic constraints to identify Bethe-Heitler events and remove them. Counts x ep e px.6 GeV, reversed field φ e - φ p (deg) lectron-proton Opening Angle (deg) ep e px.6 GeV, reversed field W (GeV)

15 Results of Bethe-Heitler suppression for?. K. Joo and C. Smith results. This analysis for.6 GeV, reversed field. ep e px,.6 GeV reversed field ep e px,.6 GeV reversed field Counts 6 5 no Bethe- Heitler suppression Counts 6 5 Bethe-Heitler suppressed MM (GeV ) MM (GeV )

16 Comparison of Asymmetries Run By Run for?. K. Joo and C. Smith for resonance at.5 GeV, CAS Analysis -8. This analysis for.6 GeV, reversed field. A T <A T >= -.58 ±.9, Q =.4-.7 GeV (Joo and Smith) <A T >= -.54 ±.7, Q =.5-. GeV (this work) from fit: -.5 ±.9, χ /ν =.8 A T Run Number Our results for > "(& here are consistent with K. Joo and C. Smith in sign (the two experiments use different and ranges) and with helicity sign recorded in the elog.

17 Preliminary Results (not for distribution) For.6 GeV, reversed field. A T ed e pn.6 GeV, reversed field Q = (GeV/c) <sin φ > Method Bates Results at Q =. (GeV/c) S.Gilad, et al., NP, A63, 76c (998) (deg) A T ed e pn.6 GeV, reversed field Q =.3-. (GeV/c) <sin φ > Method (deg) For.6 GeV, normal field. A T.5..5 ed e pn.6 GeV, normal field Q =.8 -. (GeV/c) <sin φ > Method (deg)

18 Preliminary Results for from (not for distribution).6 GeV normal torus polarity Quasi-elastic Kinematics.. Q =.6-.8 GeV.. Q =.8-. GeV.. Q =.-. GeV Curves from H.Arenhoevel Q =.4-.6 GeV. Q =.6-.8 GeV. Q =.8-. GeV p m (GeV/c) GeV reversed torus polarity Quasi-elastic Kinematics :34:53 p m (GeV/c) p m (GeV/c) p m (GeV/c)

19 Conclusions Strong physics motivation to test the nuclear coherent hadronic model in a new energy range. Two methods of measuring > "(& using -./,D6 8 and a fit to the helicity asymmetry are consistent with each other. Our analysis of > "(& from the hydrogen target is consistent with an earlier study by Joo and Smith. Preliminary results for > "(& reveal a significant structure dip at and : 4. > > There is significant structure in "(& and && (and "(& and && ). A written version can be found in the 5 portion of the Hall B secure website. electrodisintegration.ps