-
H. Fonvieille,
G. Laveissière,
N. Degrande,
S. Jaminion,
C. Jutier,
L. Todor,
R. Di Salvo,
L. Van Hoorebeke,
L. C. Alexa,
B. D. Anderson, [......],
E. Voutier,
J. W. Watson,
L. B. Weinstein,
K. Wijesooriya,
R. Wilson,
B. B. Wojtsekhowski,
D. G. Zainea,
W-M. Zhang,
J. Zhao, Z.-L. Zhou
[show abstract]
[hide abstract]
ABSTRACT: Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep→epγ. This paper gives a detailed account of the analysis which has led to the determination of the structure functions PLL−PTT/ε and PLT and the electric and magnetic generalized polarizabilities (GPs) αE(Q2) and βM(Q2) at values of the four-momentum transfer squared Q2=0.92 and 1.76 GeV2. These data, together with the results of VCS experiments at lower momenta, help building a coherent picture of the electric and magnetic GPs of the proton over the full measured Q2 range and point to their nontrivial behavior.
Phys. Rev. C. 07/2012; 86(1).
-
H. Fonvieille,
G. Laveissiere,
N. Degrande,
S. Jaminion,
C. Jutier,
L. Todor,
R. Di Salvo,
L. Van Hoorebeke,
L. C. Alexa,
B. D. Anderson, [......],
E. Voutier,
J. W. Watson,
L. B. Weinstein,
K. Wijesooriya,
R. Wilson,
B. B. Wojtsekhowski,
D. G. Zainea,
W. -M. Zhang,
J. Zhao, Z. -L. Zhou
[show abstract]
[hide abstract]
ABSTRACT: Virtual Compton Scattering (VCS) on the proton has been studied at Jefferson
Lab using the exclusive photon electroproduction reaction (e p --> e p gamma).
This paper gives a detailed account of the analysis which has led to the
determination of the structure functions P_LL-P_TT/epsilon and P_LT, and the
electric and magnetic generalized polarizabilities (GPs) alpha_E(Q^2) and
beta_M(Q^2) at values of the four-momentum transfer squared Q^2= 0.92 and 1.76
GeV^2. These data, together with the results of VCS experiments at lower
momenta, help building a coherent picture of the electric and magnetic GPs of
the proton over the full measured Q^2-range, and point to their non-trivial
behavior.
05/2012;
-
C Zhang,
M Kohl,
T Akdogan,
R Alarcon,
W Bertozzi,
E Booth,
T Botto,
J R Calarco,
B Clasie,
C Crawford, [......],
T Smith,
B Tonguc,
C Tschalär,
E Tsentalovich,
W Turchinetz,
Y Xiao,
W Xu, Z-L Zhou,
V Ziskin,
T Zwart
[show abstract]
[hide abstract]
ABSTRACT: We report a precision measurement of the deuteron tensor analyzing powers T(20) and T(21) at the MIT-Bates Linear Accelerator Center. Data were collected simultaneously over a momentum transfer range Q=2.15-4.50 fm(-1) with the Bates Large Acceptance Spectrometer Toroid using a highly polarized deuterium internal gas target. The data are in excellent agreement with calculations in a framework of effective field theory. The deuteron charge monopole and quadrupole form factors G(C) and G(Q) were separated with improved precision, and the location of the first node of G(C) was confirmed at Q=4.19±0.05 fm(-1). The new data provide a strong constraint on theoretical models in a momentum transfer range covering the minimum of T(20) and the first node of G(C).
Physical Review Letters 12/2011; 107(25):252501. · 7.37 Impact Factor
-
P. Bourgeois,
Y. Sato,
J. Shaw,
R. Alarcon,
A. M. Bernstein,
W. Bertozzi,
T. Botto,
J. Calarco,
F. Casagrande,
M. O. Distler, [......],
E. Six,
N. F. Sparveris,
S. Stave,
E. Stiliaris,
T. Tamae,
G. Tsentalovich,
C. Tschalaer,
W. Turchinetz, Z.-L. Zhou,
T. Zwart
[show abstract]
[hide abstract]
ABSTRACT: Experimental details of a virtual Compton scattering (VCS) experiment performed on the proton at the MIT-Bates out-of-plane scattering facility are presented. The VCS response functions PLL−PTT/PTTɛɛ and PLT have been measured at Q2=0.057 GeV2/c2. The generalized electric and magnetic polarizabilities, α(Q2) and β(Q2), and the mean-square electric polarizability radius〈rα2〉 are obtained from a dispersion analysis of the data. The results are in good agreement with O(p3) heavy baryon chiral perturbation and indicate the dominance of mesonic effects in the polarizabilities.
Phys. Rev. C. 09/2011; 84(3).
-
G. Laveissière,
N. Degrande,
S. Jaminion,
C. Jutier,
L. Todor,
R. Di Salvo,
L. Van Hoorebeke,
L. C. Alexa,
B. D. Anderson,
K. A. Aniol, [......],
E. Voutier,
J. W. Watson,
L. B. Weinstein,
K. Wijesooriya,
R. Wilson,
B. B. Wojtsekhowski,
D. G. Zainea,
W.-M. Zhang,
J. Zhao, Z.-L. Zhou
[show abstract]
[hide abstract]
ABSTRACT: We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e, e'p)γ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W-dependence at fixed Q2=1 GeV2 and for the Q2 dependence at fixed W near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed Q2 dependence is smooth. The measured ratio of H(e, e'p)γ to H(e, e'p)π0 cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to real Compton scattering (RCS) at high energy and large angles, our VCS data at the highest W (1.8-1.9 GeV) show a striking Q2 independence, which may suggest a transition to a perturbative scattering mechanism at the quark level.
Phys. Rev. C. 01/2009; 79(1).
-
P Bourgeois,
Y Sato,
J Shaw,
R Alarcon,
A M Bernstein,
W Bertozzi,
T Botto,
J Calarco,
F Casagrande,
M O Distler, [......],
E Six,
N F Sparveris,
S Stave,
E Stiliaris,
T Tamae,
G Tsentalovich,
C Tschalaer,
W Turchinetz, Z-L Zhou,
T Zwart
[show abstract]
[hide abstract]
ABSTRACT: The mean square polarizability radii of the proton have been measured for the first time in a virtual-Compton-scattering experiment performed at the MIT-Bates out-of-plane scattering facility. Response functions and polarizabilities obtained from a dispersion analysis of the data at Q2 = 0.057 GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory. The data support the dominance of mesonic effects in the polarizabilities.
Physical Review Letters 12/2006; 97(21):212001. · 7.37 Impact Factor
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P Bourgeois,
Y Sato,
J Shaw,
R. Alarcon,
A. M. Bernstein,
W. Bertozzi,
T. Botto,
J Calarco,
F. Casagrande,
M. O. Distler, [......],
E. Six,
N. F. Sparveris,
S. Stave,
E Stiliaris,
T Tamae,
G Tsentalovich,
C. Tschalaer,
W. Turchinetz, Z L Zhou,
T. Zwart
[show abstract]
[hide abstract]
ABSTRACT: The mean square polarizability radii of the proton have been measured for the
first time in a virtual Compton scattering experiment performed at the
MIT-Bates out-of-plane scattering facility. Response functions and
polarizabilities obtained from a dispersion analysis of the data at Q2=0.06
GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory.
The data support the dominance of mesonic effects in the polarizabilities, and
the increase of beta with increasing Q2 is evidence for the cancellation of
long-range diamagnetism by short-range paramagnetism from the pion cloud.
05/2006;
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N F Sparveris,
R Alarcon,
A M Bernstein,
W Bertozzi,
T Botto,
P Bourgeois,
J Calarco,
F Casagrande,
M O Distler,
K Dow, [......],
J Shaw,
E Six,
S Stave,
E Stiliaris,
T Tamae,
G Tsentalovich,
C Tschalaer,
W Turchinetz, Z-L Zhou,
T Zwart
[show abstract]
[hide abstract]
ABSTRACT: We report new precise H(e,e(')p)pi(0) measurements at the Delta(1232) resonance at Q(2)=0.127 (GeV/c)(2) obtained at the MIT-Bates out-of-plane scattering facility which are particularly sensitive to the transverse electric amplitude (E2) of the gamma(*)N-->Delta transition. The new data have been analyzed together with those of earlier measurements to yield precise quadrupole to dipole amplitude ratios: Re(E(3/2)(1+)/M(3/2)(1+))=(-2.3+/-0.3(stat+syst)+/-0.6(model))% and Re(S(3/2)(1+)/M(3/2)(1+))=(-6.1+/-0.2(stat+syst)+/-0.5(model))% for M(3/2)(1+)=(41.4+/-0.3(stat+syst)+/-0.4(model))(10(-3)/m(pi(+))). The derived amplitudes give credence to the conjecture of deformation in hadrons favoring, at low Q2, the dominance of mesonic effects.
Physical Review Letters 01/2005; 94(2):022003. · 7.37 Impact Factor
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K. A. Aniol,
M. B. Epstein,
E. Gama,
D. J. Margaziotis,
W. Bertozzi,
J. P. Chen,
D. Dale,
R. E. J. Florizone,
S. Gilad,
A. J. Sarty, [......],
Th. Walcher,
M. Kuss,
A. Richter,
G. Schrieder,
K. Bohinc,
M. Potokar,
S. Širca,
J. M. Udias,
Javier R. Vignote,
R. Schiavilla
[show abstract]
[hide abstract]
ABSTRACT: We have measured the 4He(e, ep)3H reaction at missing momenta of 130-300 MeV/c using the three-spectrometer facility at the Mainz microtron MAMI. Data were taken in perpendicular kinematics to allow us to determine the response function RLT and the asymmetry term ATL. The data are compared to both relativistic and non-relativistic calculations.
European Physical Journal A 11/2004; 22(3):449-454. · 2.19 Impact Factor
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A Kozlov,
A J Sarty,
K A Aniol,
P Bartsch,
D Baumann,
W Bertozzi,
K Bohinc,
R Böhm,
J P Chen,
D Dale, [......],
J A Templon,
M N Thompson,
A Wagner,
Th Walcher,
M Weis,
J Zhao, Z-L Zhou,
J Golak,
W Glöckle,
H Witała
[show abstract]
[hide abstract]
ABSTRACT: New, high-precision measurements of the 3He(e,e(')p) reaction using the A1 Collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasielastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on the plane wave impulse approximation were observed in both the two- and three-body breakup channels. Full Faddeev-type calculations account for some of the observed excess cross-section, but significant differences remain.
Physical Review Letters 10/2004; 93(13):132301. · 7.37 Impact Factor
-
G Laveissière,
L Todor,
N. Degrande,
S. Jaminion,
C. Jutier,
R. Di Salvo,
L. Van Hoorebeke,
L.C. Alexa,
B D Anderson,
K. A. Aniol, [......],
E. Voutier,
J. W. Watson,
L B Weinstein,
K. Wijesooriya,
R Wilson,
B. B. Wojtsekhowski,
D.G. Zainea,
W M Zhang,
J Zhao, Z L Zhou
[show abstract]
[hide abstract]
ABSTRACT: We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions P(LL)-P(TT)/epsilon and P(LT), and the electric and magnetic generalized polarizabilities (GPs) alpha(E)(Q2) and beta(M)(Q2) at momentum transfer Q(2)=0.92 and 1.76 GeV2. The electric GP shows a strong falloff with Q2, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from piN intermediate states.
Physical Review Letters 10/2004; 93(12):122001. · 7.37 Impact Factor
-
K. A. Aniol,
M.B. Epstein,
E. Gama,
D J Margaziotis,
W. Bertozzi,
J P Chen,
D Dale,
R. E. J. Florizone,
S Gilad,
A. J. Sarty, [......],
Th. Walcher,
M. Kuss,
A Richter,
G. Schrieder,
K. Bohinc,
M. Potokar,
S. Sirca,
J. M. Udias,
Javier R. Vignote,
R. Schiavilla
[show abstract]
[hide abstract]
ABSTRACT: We have measured the 4He(e,e'p)3H reaction at missing momenta of 130-300 MeV/c using the three-spectrometer facility at the Mainz microtron MAMI. Data were taken in perpendicular kinematics to allow us to determine the response function Rlt and the asymmetry term Atl. The data are compared to both relativistic and non-relativistic calculations.
09/2004;
-
K. G. Fissum,
M. Liang,
B. D. Anderson,
K. A. Aniol,
L. Auerbach,
F. T. Baker,
J. Berthot,
W. Bertozzi,
P.-Y. Bertin,
L. Bimbot, [......],
K. Wijesooriya,
B. Wojtsekhowski,
D. G. Zainea,
V. Zeps,
J. Zhao, Z.-L. Zhou,
J. M. Udías,
J. R. Vignote,
J. Ryckebusch,
D. Debruyne
[show abstract]
[hide abstract]
ABSTRACT: The physics program in Hall A at Jefferson Lab commenced in the summer
of 1997 with a detailed investigation of the 16O (e, e' p)
reaction in quasielastic, constant (q,ω) kinematics at
Q2 ≈0.8 (GeV/c)2 , q≈1 GeV/c , and
ω≈445 MeV . Use of a self-calibrating, self-normalizing,
thin-film waterfall target enabled a systematically rigorous
measurement. Five-fold differential cross-section data for the removal
of protons from the 1p -shell have been obtained for 0<
pmiss <350 MeV/c . Six-fold differential cross-section
data for 0< Emiss <120 MeV were obtained for 0<
pmiss <340 MeV/c . These results have been used to extract
the ALT asymmetry and the RL , RT ,
RLT , and RL+TT effective response functions
over a large range of Emiss and pmiss .
Detailed comparisons of the 1p -shell data with Relativistic
Distorted-Wave Impulse Approximation (RDWIA), Relativistic Optical-Model
Eikonal Approximation (ROMEA), and Relativistic Multiple-Scattering
Glauber Approximation (RMSGA) calculations indicate that two-body
currents stemming from meson-exchange currents (MEC) and isobar currents
(IC) are not needed to explain the data at this Q2 .
Further, dynamical relativistic effects are strongly indicated by the
observed structure in ALT at pmiss ≈300
MeV/c . For 25< Emiss <50 MeV and pmiss
≈50 MeV/c , proton knockout from the 1 s1/2 -state
dominates, and ROMEA calculations do an excellent job of explaining the
data. However, as pmiss increases, the single-particle
behavior of the reaction is increasingly hidden by more complicated
processes, and for 280< pmiss <340 MeV/c , ROMEA
calculations together with two-body currents stemming from MEC and IC
account for the shape and transverse nature of the data, but only about
half the magnitude of the measured cross section. For 50<
Emiss <120 MeV and 145< pmiss <340
MeV/c , (e, e' pN) calculations which include the contributions of
central and tensor correlations (two-nucleon correlations) together with
MEC and IC (two-nucleon currents) account for only about half of the
measured cross section. The kinematic consistency of the 1p -shell
normalization factors extracted from these data with respect to all
available 16O (e, e' p) data is also examined in detail.
Finally, the Q2 -dependence of the normalization factors is
discussed.
Physical Review C 08/2004; 70(3):34606. · 3.31 Impact Factor
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G. Laveissière,
N. Degrande,
S. Jaminion,
C. Jutier,
L. Todor,
R. Di Salvo,
L. Van Hoorebeke,
L. C. Alexa,
B. D. Anderson,
K. A. Aniol, [......],
E. Voutier,
J. W. Watson,
L. B. Weinstein,
K. Wijesooriya,
R. Wilson,
B. B. Wojtsekhowski,
D. G. Zainea,
W-M. Zhang,
J. Zhao, Z.-L. Zhou
[show abstract]
[hide abstract]
ABSTRACT: Exclusive electroproduction of π0 mesons on protons in the backward hemisphere has been studied at Q2=1.0 GeV2 by detecting protons in the forward direction in coincidence with scattered electrons from the 4 GeV electron beam in Jefferson Lab’s Hall A. The data span the range of the total (γ*p) center-of-mass energy W from the pion production threshold to W=2.0 GeV. The differential cross sections σT+ϵσL, σTL, and σTT were separated from the azimuthal distribution and are presented together with the MAID and SAID parametrizations.
Phys. Rev. C. 04/2004; 69(4).
-
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]
[hide abstract]
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).
-
L D van Buuren,
D Szczerba,
R Alarcon,
D J Boersma,
J F J van den Brand,
H J Bulten,
R Ent,
M Ferro-Luzzi,
M Harvey,
P Heimberg, [......],
B L Militsyn,
D Nikolenko,
B E Norum,
I Passchier,
H R Poolman,
I Rachek,
M C Simani,
E Six,
H de Vries, Z-L Zhou
[show abstract]
[hide abstract]
ABSTRACT: We report on measurements of the cross section and provide first data on spin correlation parameters A(TT') and A(TL') in inclusive scattering of longitudinally polarized electrons from nuclear-polarized hydrogen. Polarized electrons were injected into an electron storage ring operated at a beam energy of 720 MeV. Polarized hydrogen was produced by an atomic beam source and injected into an open-ended cylindrical cell, located in the electron storage ring. The four-momentum transfer squared ranged from Q2 = 0.2 GeV(2)/c(2) at the elastic scattering peak to Q2 = 0.11 GeV(2)/c(2) at the Delta(1232) resonance. The data provide a stringent test of pion electroproduction models.
Physical Review Letters 08/2002; 89(1):012001. · 7.37 Impact Factor
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I Passchier,
L D van Buuren,
D Szczerba,
R Alarcon,
Th S Bauer,
D J Boersma,
J F J van Den Brand,
H J Bulten,
R Ent,
M Ferro-Luzzi, [......],
D Nikolenko,
G J L Nooren,
B E Norum,
H R Poolman,
I Rachek,
M C Simani,
E Six,
H de Vries,
K Wang, Z-L Zhou
[show abstract]
[hide abstract]
ABSTRACT: The spin-momentum correlation parameter A(V)(ed) was measured for the 2H-->(e-->,e'p)n reaction for missing momenta up to 350 MeV/c at Q2 = 0.21 (GeV/c)(2) for quasielastic scattering of polarized electrons from vector-polarized deuterium. The data give detailed information about the deuteron spin structure and are in good agreement with the results of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment reveals in a most direct manner the effects of the D state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction.
Physical Review Letters 03/2002; 88(10):102302. · 7.37 Impact Factor
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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
[show abstract]
[hide abstract]
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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I. Passchier,
L. D. van Buuren,
D. Szczerba,
R. Alarcon,
Th. S. Bauer,
D. Boersma,
J. F. J. van den Brand,
H. J. Bulten,
R. Ent,
M Ferro-Luzzi, [......],
D. Nikolenko,
G. J. L. Nooren,
B. E. Norum,
H. R. Poolman,
I. Rachek,
M C Simani,
E. Six,
H. de Vries,
K Wang, Z L Zhou
[show abstract]
[hide abstract]
ABSTRACT: We report on a measurement of spin-momentum correlations in quasi-elastic scattering of longitudinally polarized electrons with an energy of 720 MeV from vector-polarized deuterium. The spin correlation parameter $A^V_{ed}$ was measured for the $^2 \vec{\rm H}(\vec e,e^\prime p)n$ reaction for missing momenta up to 350 MeV/$c$ at a four-momentum transfer squared of 0.21 (GeV/c)$^2$. The data give detailed information about the spin structure of the deuteron, and are in good agreement with the predictions of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment demonstrates in a most direct manner the effects of the D-state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction. Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. for publication
09/2001;
-
Z L Zhou,
J Chen,
S. -B. Soong,
A. Young,
X Jiang,
R. Alarcon,
H. Arenhoevel,
A Bernstein,
W. Bertozzi,
J. Comfort,
G. Dodson,
The MIT-Bates OOPS Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Measurements of the ${^2}H(\vec{e},e^{\prime}p)n$ reaction were performed using an 800-MeV polarized electron beam at the MIT-Bates Linear Accelerator and with the out-of-plane magnetic spectrometers (OOPS). The longitudinal-transverse, $f_{LT}$ and $f_{LT}^{\prime}$, and the transverse-transverse, $f_{TT}$, interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q$^2$=0.15 (GeV/c)$^2$. On comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions, and the importance of the two-body meson-exchange currents and isobar configurations. We demonstrate that these effects can be disentangled and studied by extracting the interference response functions using the novel out-of-plane technique.
06/2001;
