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N. F. Sparveris,
R. Alarcon,
D. Barkhuff,
A. Bernstein,
W. Bertozzi,
J. Calarco,
F. Casagrande,
J. Chen,
J. Comfort,
M. O. Distler, [......],
E. Stiliaris,
D. Tieger,
C. Tschalaer,
W. Turchinetz,
C. Vellidis,
G. A. Warren,
A. Young,
J. Zhao,
Z.-L. Zhou,
T. Zwart
[show abstract]
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ABSTRACT: Quadrupole amplitudes in the γ*N⃗Δ transition are associated with the issue of nucleon deformation. A search for these small amplitudes has been the focus of a series of measurements undertaken at Bates/MIT by the OOPS Collaboration. We report on results from H(e,e′p)π0 data obtained at Q2=0.070(GeV/c)2 and invariant mass of W=1155MeV using the out-of-plane detection technique with the OOPS spectrometers. The σLT and σT+εσL response functions were isolated. These results, along with those of previous measurements at W=1172MeV and Q2=0.127(GeV/c)2, aim in elucidating the interplay between resonant and nonresonant amplitudes.
Phys. Rev. C. 05/2003; 67(5).
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Z L Zhou,
J Chen,
S B Soong,
A Young,
X Jiang,
R Alarcon,
H Arenhövel,
A Bernstein,
W Bertozzi,
J Comfort, [......],
J A Tjon,
C Tschalaer,
E Tsentalovich,
W Turchinetz,
C E Vellidis,
G A Warren,
L B Weinstein,
S Williamson,
J Zhao,
T Zwart
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ABSTRACT: Measurements of the (2)H((-->)e,e(')p)n reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, f(LT) and f(')(LT), and the transverse-transverse, f(TT), interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2 = 0.15 (GeV/c)(2). In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of-plane technique.
Physical Review Letters 10/2001; 87(17):172301. · 7.37 Impact Factor
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C Mertz,
C E Vellidis,
R Alarcon,
D H Barkhuff,
A M Bernstein,
W Bertozzi,
V Burkert,
J Chen,
J R Comfort,
G Dodson, [......],
D Tieger,
C Tschalaer,
W Turchinetz,
P E Ulmer,
S Van Verst,
G A Warren,
L B Weinstein,
S Williamson,
R J Woo,
A Young
[show abstract]
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ABSTRACT: High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account.
Physical Review Letters 04/2001; 86(14):2963-6. · 7.37 Impact Factor
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C. Mertz,
C. Vellidis,
R. Alarcon,
D. H. Barkhuff,
A. M. Bernstein,
W. Bertozzi,
V Burkert,
J Chen,
J.R. Comfort,
G. Dodson, [......],
D. Tieger,
C. Tschalaer,
W. Turchinetz,
P E Ulmer,
S. van Verst,
G. A. Warren,
L B Weinstein,
S. Williamson,
R. J. Woo,
A. Young
[show abstract]
[hide abstract]
ABSTRACT: High-precision H(e,e'p)pi0 measurements at Q2=0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma* N->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole amplitude ratios, Rsm=(-6.5 +- 0.2{stat+sys} +- 2.5{mod}) % and Rem=(-2.1 +- 0.2{stat+sys} +- 2.0{mod}) %, are dominated by model error. Previous Rsm and Rem results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account. Comment: 5 pages LATEX, 2 figures; resubmitted to Phys. Rev. Lett
02/1999;
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Z L Zhou,
J Chen,
S. -B. Soong,
A. Young,
X Jiang,
R. Alarcon,
A Bernstein,
W. Bertozzi,
J. Comfort,
G. Dodson, [......],
S Gilad,
R. Hicks,
A Hotta,
K Joo,
N. I. Kaloskamis,
A. Karabarbounis,
S. Kowalski,
C. Kunz,
D. Margaziotis, C. Mertz
[show abstract]
[hide abstract]
ABSTRACT: A set of three out-of-plane magnetic spectrometers (OOPS) has recently been deployed and commissioned at the Bates Linear Accelerator. Measurements of the 2H(e, e'p)n reaction have been performed using an 800 MeV polarized-electron beam and the OOOPS to detect protons in coincidence with an electron spectrometer in kinematics of either quasielastic (QE) at Q2=0.22(GeV/c)2 or non-quasielastic (dip) at Q2=0.15 (GeV/c)2. Two and three OOPS were positioned symmetrically along the direction of momentum transfer in phi p q=(45, 135) degrees and (0, 90, 180) degrees configurations, respectively for a given set of theta p q values. This allowed simultaneous meaasurements of the longitudinal-transverse responses, fLT and f'LT, and the transverse-transverse response fTT at various central missing momenta ranging from 145 to 265 MeV/c. Here, preliminary results are presented and compared with vigorous model calculations. The data reveal strong effects of relativity and final-state interactions, as well as the two-body currents, which include the meson-exchange and iso-bar currents, in the deuteron electrodisintegration. An out-look of future OOPS programs is also discussed.
10/1998;
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[show abstract]
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ABSTRACT: Introduction The electromagnetic N!Delta transition involves three multipoles, M1 (magnetic dipole), E2 (electric quadrupole) and C2 (Coulomb quadrupole). The transition is studied via electromagnetic pion production on the free proton in the Delta(1232) resonance region, which is analyzed in terms of pion partial waves. In these terms, the photon multipoles M1, E2 and C2 are translated to the pion multipoles M1+ , E1+ and S1+ , respectively. Of special importance are the relative strengths of E1+ and S1+ with respect to the dominant M1+ multipole. a Arizona State University; Bates Linear Accelerator Center; Bonn University; California State University at Los Angeles; College of William & Mary; Florida State University; National and Capodistrian University of Athens; Massachusetts Institute of T
10/1998;
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B.D. Milbrath,
J. I. McIntyre,
C. S. Armstrong,
D. H. Barkhuff,
W. Bertozzi,
D Dale,
G. Dodson,
K. A. Dow,
M.B. Epstein,
M. Farkhondeh, [......],
P.M. Rutt,
A. J. Sarty,
D. Tieger,
C. Tschalaer,
W. Turchinetz,
P E Ulmer,
S. P. Van Verst,
G. A. Warren,
L B Weinstein,
R. J. Woo
[show abstract]
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ABSTRACT: Recoil proton polarization observables were measured for both the p($\vec {\rm e}$,e$^\prime\vec{\rm p}\,$) and d($\vec {\rm e}$,e$^\prime\vec{\rm p}\,)$n reactions at two values of Q$^2$ using a newly commissioned proton Focal Plane Polarimeter at the M.I.T.-Bates Linear Accelerator Center. The hydrogen and deuterium spin-dependent observables $D_{\ell\ell}$ and $D_{{\ell}t}$, the induced polarization $P_n$ and the form factor ratio $G^p_E/G^p_M$ were measured under identical kinematics. The deuterium and hydrogen results are in good agreement with each other and with the plane-wave impulse approximation (PWIA). Comment: 9 pages, 1 figure; accepted by Phys. Rev. Lett
12/1997;
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R. J. Woo,
D. H. Barkhuff,
W. Bertozzi,
D Dale,
G. Dodson,
K. A. Dow,
M.B. Epstein,
M. Farkhondeh,
J.M. Finn,
S Gilad, [......],
P.M. Rutt,
A. J. Sarty,
D. Tieger,
C. Tschalaer,
W. Turchinetz,
P E Ulmer,
C. Vellidis,
S. P. Van Verst,
G. A. Warren,
L. Weinstein
[show abstract]
[hide abstract]
ABSTRACT: The first measurements of the induced proton polarization, P_n, for the 12C (e,e'\vec{p}) reaction are reported. The experiment was performed at quasifree kinematics for energy and momentum transfer (\omega,q) \approx (294 MeV, 756 MeV/c) and sampled a recoil momentum range of 0-250 MeV/c. The induced polarization arises from final-state interactions and for these kinematics is dominated by the real part of the spin-orbit optical potential. The distorted-wave impulse approximation provides good agreement with data for the 1p_{3/2} shell. The data for the continuum suggest that both the 1s_{1/2} shell and underlying l > 1 configurations contribute. Comment: 5 pages LaTeX, 2 postscript figures, accepted by Physical Reveiw Letters
11/1997;
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D.H. Barkhuff,
C.S. Armstrong,
W. Bertozzi,
J.P. Chen,
D. Dale,
G. Dodson,
K.A. Dow,
M.B. Epstein,
M. Farkhondeh,
J.M. Finn, [......],
A.J. Sarty,
D. Tieger,
C. Tschalær,
W. Turchinetz,
P.E. Ulmer,
S.P. Van Verst,
C. Vellidis,
G. Warren,
L.B. Weinstein,
R.J. Woo
[show abstract]
[hide abstract]
ABSTRACT: In order to test modern theories of two-nucleon bound and scattering states, we have measured the spin polarization of ejectile protons in the electrodisintegration reaction . Compared with spin-averaged observations, these observables offer the potential of enhanced sensitivity to details of the reaction process. The experiment was carried out in quasielastic kinematics (GeV2/c2). Protons were detected at two angles corresponding to neutron recoil momenta pr of 0 and 100 MeV/c. Full nonrelativistic calculations of the polarization transfer components sl and st, including leading order relativistic contributions, describe our measurements well, but calculations of the induced polarization sn at pr=100 MeV/c underpredict the experimental result.
Physics Letters B.
