-
D. Wang,
K. Pan,
R. Subedi,
X. Deng,
Z. Ahmed,
K. Allada,
K. A. Aniol,
D. S. Armstrong,
J. Arrington,
V. Bellini, [......],
P. A. Souder,
R. Suleiman,
V. Sulkosky,
C. M. Sutera,
W. A. Tobias,
B. Waidyawansa,
B. Wojtsekhowski,
L. Ye,
B. Zhao,
X. Zheng
[show abstract]
[hide abstract]
ABSTRACT: We report on parity-violating asymmetries in the nucleon resonance region
measured using $5 - 6$ GeV longitudinally polarized electrons scattering off an
unpolarized deuterium target. These results are the first parity-violating
asymmetry data in the resonance region beyond the $\Delta(1232)$, and provide a
verification of quark-hadron duality in the nucleon electroweak $\gamma Z$
interference structure functions at the 10-15% level. The results are of
particular interest to models relevant for calculating the $\gamma Z$
box-diagram corrections to elastic parity-violating electron scattering
measurements.
04/2013;
-
P. Solvignon,
N. Liyanage,
J. -P. Chen,
Seonho Choi,
K. Slifer,
K. Aniol,
T. Averett,
W. Boeglin,
A. Camsonne,
G. D. Cates, [......],
V. Sulkosky,
A. Tobias,
G. M. Urciuoli,
K. Wang,
K. Wijesooriya,
B. Wojtsekhowski,
S. Woo,
J. -C. Yang,
X. Zheng,
L. Zhu
[show abstract]
[hide abstract]
ABSTRACT: We present new experimental results of the $^3$He spin structure function
$g_2$ in the resonance region at $Q^2$ values between 1.2 and 3.0 (GeV/c)$^2$.
Spin dependent moments of the neutron were then extracted. The resonance
contribution to the neutron $d_2$ matrix element was found to be small at $\ <
Q^2 \ >$=2.4 (GeV/c)$^2$ and in agreement with the Lattice QCD calculation. The
Burkhardt-Cottingham sum rule for neutron was tested with the measured data and
using the Wandzura-Wilczek relation for the low $x$ unmeasured region. A small
deviation was observed at $Q^2$ values between 0.5 and 1.2 (GeV/c)$^2$ for the
neutron.
04/2013;
-
S. Riordan,
C. Keppel,
K. Aniol,
J. Annand,
J. Arrington,
T. Averett,
C. Ayerbe Gayoso,
E. Brash,
G. D. Cates,
J. -P. Chen, [......],
N. F. Sparveris,
V. Sulkosky,
V. Vereshchaka,
B. Wojtsekhowski,
Z. Ye,
J. Zhang,
Y. W. Zhang,
X. Zheng,
R. Zielinski,
the Hall A Collaboration
02/2013;
-
P. Monaghan,
R. Shneor,
R. Subedi,
B. D. Anderson,
K. Aniol,
J. Annand,
J. Arrington,
H. Benaoum,
F. Benmokhtar,
P. Bertin, [......],
G. M. Urciuoli,
E. Voutier,
K. Wang,
J. W. Watson,
L. B. Weinstein,
B. Wojtsekhowski,
S. Wood,
H. Yao,
X. Zheng,
L. Zhu
[show abstract]
[hide abstract]
ABSTRACT: The five-fold differential cross section for the 12C(e,e'p)11B reaction was
determined over a missing momentum range of 200-400 MeV/c, in a kinematics
regime with Bjorken x > 1 and Q2 = 2.0 (GeV/c)2. A comparison of the results
and theoretical models and previous lower missing momentum data is shown. The
theoretical calculations agree well with the data up to a missing momentum
value of 325 MeV/c and then diverge for larger missing momenta. The extracted
distorted momentum distribution is shown to be consistent with previous data
and extends the range of available data up to 400 MeV/c.
01/2013;
-
F. Garibaldi,
P. Bydzovsky,
E. Cisbani,
F. Cusanno,
R. De Leo,
S. Frullani,
D. W. Highinbotham,
M. Iodice, J. J. LeRose,
P. Markowitz,
G. M. Urciuoli,
for the Hall A Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The first systematic study of 1p-shell and medium-heavy hypernuclei by
electroproduction of strangeness has started at Jefferson Laboratory with the
experiments E89-009, E94-107, E01-011, E05-115. The main results obtained in
Hall A and future prospects of the investigation of hypernuclei at Jefferson
Laboratory regarding the study of the angular dependence of electroproduction
of strangeness and the possibility of performing the spectroscopy of
208^Tl_Lambda are reported here.
11/2012;
-
S. Abrahamyan,
A. Acha,
A. Afanasev,
Z. Ahmed,
H. Albataineh,
K. Aniol,
D. S. Armstrong,
W. Armstrong,
J. Arrington,
T. Averett, [......],
Y. Ye,
Z. Ye,
V. Yim,
L. Zana,
X. Zhan,
J. Zhang,
Y. Zhang,
X. Zheng,
V. Ziskin,
P.Zhu
[show abstract]
[hide abstract]
ABSTRACT: We have measured the beam-normal single-spin asymmetry An in the elastic scattering of 1–3 GeV transversely polarized electrons from 1H and for the first time from 4He, 12C, and 208Pb. For 1H, 4He, and 12C, the measurements are in agreement with calculations that relate An to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the 208Pb result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new An measurements might emerge as a new and sensitive probe of the structure of heavy nuclei.
Physical Review Letters 11/2012; 109:192501. · 7.37 Impact Factor
-
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;
-
S Abrahamyan,
Z Ahmed,
H Albataineh,
K Aniol,
D S Armstrong,
W Armstrong,
T Averett,
B Babineau,
A Barbieri,
V Bellini, [......],
H Yao,
Y Ye,
Z Ye,
V Yim,
L Zana,
X Zhan,
J Zhang,
Y Zhang,
X Zheng,
P Zhu
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of the parity-violating asymmetry A(PV) in the elastic scattering of polarized electrons from 208Pb. A(PV) is sensitive to the radius of the neutron distribution (R(n)). The result A(PV)=0.656±0.060(stat)±0.014(syst) ppm corresponds to a difference between the radii of the neutron and proton distributions R(n)-R(p)=0.33(-0.18)(+0.16) fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.
Physical Review Letters 03/2012; 108(11):112502. · 7.37 Impact Factor
-
Z Ahmed,
K Allada,
K A Aniol,
D S Armstrong,
J Arrington,
P Baturin,
V Bellini,
J Benesch,
R Beminiwattha,
F Benmokhtar, [......],
D Wang,
J Wexler,
R Wilson,
B Wojtsekhowski,
X Zhan,
X Yan,
H Yao,
L Ye,
B Zhao,
X Zheng
[show abstract]
[hide abstract]
ABSTRACT: The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV2 and beam energy E(b) = 3.48 GeV to be A(PV) = -23.80 ± 0.78(stat) ± 0.36(syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G(E)(s) + 0.517G(M)(s) = 0.003 ± 0.010(stat) ± 0.004(syst) ± 0.009(ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.
Physical Review Letters 03/2012; 108(10):102001. · 7.37 Impact Factor
-
J Huang,
K Allada,
C Dutta,
J Katich,
X Qian,
Y Wang,
Y Zhang,
K Aniol,
J R M Annand,
T Averett, [......],
Y Ye,
Z Ye,
L Yuan,
X Zhan,
Y-W Zhang,
B Zhao,
X Zheng,
L Zhu,
X Zhu,
X Zong
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of the double-spin asymmetry A{LT} for charged pion electroproduction in semi-inclusive deep-inelastic electron scattering on a transversely polarized {3}He target. The kinematics focused on the valence quark region, 0.16<x<0.35 with 1.4<Q{2}<2.7 GeV{2}. The corresponding neutron A{LT} asymmetries were extracted from the measured {3}He asymmetries and proton over {3}He cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g{1T}{q} and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for π{-} production on {3}He and the neutron, while our π{+} asymmetries are consistent with zero.
Physical Review Letters 02/2012; 108(5):052001. · 7.37 Impact Factor
-
S. Abrahamyan,
Z. Ahmed,
H. Albataineh,
K. Aniol,
D. S. Armstrong,
W. Armstrong,
T. Averett,
B. Babineau,
A. Barbieri,
V. Bellini, [......],
H. Yao,
Y. Ye,
Z. Ye,
V. Yim,
L. Zana,
X. Zhan,
J. Zhang,
Y. Zhang,
X. Zheng,
P. Zhu
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of the parity-violating asymmetry A_PV in the
elastic scattering of polarized electrons from 208Pb. A_PV is sensitive to the
radius of the neutron distribution (Rn). The result A_PV = 0.656 \pm 0.060
(stat) \pm 0.014 (syst) ppm corresponds to a difference between the radii of
the neutron and proton distributions Rn - Rp = 0.33 +0.16 -0.18 fm and provides
the first electroweak observation of the neutron skin which is expected in a
heavy, neutron-rich nucleus.
01/2012;
-
M. Mihovilovic,
K. Allada,
B. D. Anderson,
J. R. M. Annand,
T. Averett,
A. Camsonne,
R. W. Chan,
J. -P. Chen,
K. Chirapatpimol,
C. W. de Jager, [......],
G. Rosner,
B. Sawatzky,
M. Shabestari,
A. Shahinyan,
R. Shneor,
S. Sirca,
R. Subedi,
V. Sulkosky,
J. W. Watson,
Y. -W. Zhang
[show abstract]
[hide abstract]
ABSTRACT: The techniques for optical calibration of Jefferson Lab's large-acceptance
magnetic hadron spectrometer, BigBite, have been examined. The most consistent
and stable results were obtained by using a method based on singular value
decomposition. In spite of the complexity of the optics, the particles'
positions and momenta at the target have been precisely reconstructed from the
coordinates measured in the detectors by means of a single back-tracing matrix.
The technique is applicable to any similar magnetic spectrometer and any
particle type. For 0.55 GeV/c protons, we have established the vertex
resolution of 1.2 cm, angular resolutions of 7 mrad and 16 mrad (in-plane and
out-of-plane, respectively), and a relative momentum resolution of 1.6%.
01/2012;
-
S Abrahamyan,
Z Ahmed,
K Allada,
D Anez,
T Averett,
A Barbieri,
K Bartlett,
J Beacham,
J Bono,
J R Boyce, [......],
J Segal,
L Selvy,
A Shahinyan,
R Subedi,
V Sulkosky,
S Stepanyan,
N Toro,
D Walz,
B Wojtsekhowski,
J Zhang
[show abstract]
[hide abstract]
ABSTRACT: We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α' to electrons. Such a particle A' can be produced in electron-nucleus fixed-target scattering and then decay to an e + e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175-250 MeV, found no evidence for an A'→ e+ e- reaction, and set an upper limit of α'/α ~/= 10(-6). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.
Physical Review Letters 11/2011; 107(19):191804. · 7.37 Impact Factor
-
X Qian,
K Allada,
C Dutta,
J Huang,
J Katich,
Y Wang,
Y Zhang,
K Aniol,
J R M Annand,
T Averett, [......],
H F Ibrahim,
M Iodice,
X Jiang,
G Jin,
M K Jones,
A Kelleher,
W Kim,
A Kolarkar,
W Korsch, J J Lerose
09/2011; 11(6):11-14.
-
X Qian,
K Allada,
C Dutta,
J Huang,
J Katich,
Y Wang,
Y Zhang,
K Aniol,
J R M Annand,
T Averett, [......],
Y Ye,
Z Ye,
L Yuan,
X Zhan,
Y-W Zhang,
B Zhao,
X Zheng,
L Zhu,
X Zhu,
X Zong
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of target single spin asymmetries in the semi-inclusive (3)He(e,e'π(±))X reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.16 < x < 0.35 with 1.4 < Q(2) < 2.7 GeV(2). The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The π(±) Collins moments for (3)He are consistent with zero, except for the π(+) moment at x = 0.35, which deviates from zero by 2.3σ. While the π(-) Sivers moments are consistent with zero, the π(+) Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to (3)He, and are largely consistent with the predictions of phenomenological fits and quark model calculations.
Physical Review Letters 08/2011; 107(7):072003. · 7.37 Impact Factor
-
S. Abrahamyan,
Z. Ahmed,
K. Allada,
D. Anez,
T. Averett,
A. Barbieri,
K. Bartlett,
J. Beacham,
J. Bono,
J. R. Boyce, [......],
J. Segal,
L. Selvy,
A. Shahinyan,
R. Subedi,
V Sulkosky,
S Stepanyan,
N. Toro,
D. Walz,
B Wojtsekhowski,
J Zhang
[show abstract]
[hide abstract]
ABSTRACT: We present a search at Jefferson Laboratory for new forces mediated by
sub-GeV vector bosons with weak coupling $\alpha'$ to electrons. Such a
particle $A'$ can be produced in electron-nucleus fixed-target scattering and
then decay to an $e^+e^-$ pair, producing a narrow resonance in the QED trident
spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV,
found no evidence for an $A'\to e^+e^-$ reaction, and set an upper limit of
$\alpha'/\alpha \simeq 10^{-6}$. Our findings demonstrate that fixed-target
searches can explore a new, wide, and important range of masses and couplings
for sub-GeV forces.
08/2011;
-
J. Huang,
K. Allada,
C. Dutta,
J. Katich,
X. Qian,
Y. Wang,
Y. Zhang,
K. Aniol,
J. R. M. Annand,
T. Averett, [......],
Z. Ye,
L. Yuan,
X. Zhan,
Y. -W. Zhang,
B. Zhao,
X. Zheng,
L. Zhu,
X. Zhu,
X. Zong,
for the Jefferson Lab Hall A Collaboration
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of the double-spin asymmetry $A_{LT}$ for
charged pion electroproduction in semi\nobreakdash-inclusive
deep\nobreakdash-inelastic electron scattering on a transversely polarized
$^{3}$He target. The kinematics focused on the valence quark region,
$0.16<x<0.35$ with $1.4<Q^{2}<2.7\,\textrm{GeV}^{2}$. The corresponding neutron
$A_{LT}$ asymmetries were extracted from the measured $^{3}$He asymmetries and
proton over $^{3}$He cross section ratios using the effective polarization
approximation. These new data probe the transverse momentum dependent parton
distribution function $g_{1T}^{q}$ and therefore provide access to quark
spin-orbit correlations. Our results indicate a positive azimuthal asymmetry
for $\pi^{-}$ production on $^{3}$He and the neutron, while our $\pi^{+}$
asymmetries are consistent with zero.
08/2011;
-
HAPPEX collaboration,
Z. Ahmed,
K. Allada,
K. A. Aniol,
D. S. Armstrong,
J. Arrington,
P. Baturin,
V. Bellini,
J. Benesch,
R. Beminiwattha, [......],
D Wang,
J. Wexler,
R Wilson,
B Wojtsekhowski,
X Zhan,
X Yan,
H Yao,
L. Ye,
B Zhao,
X Zheng
[show abstract]
[hide abstract]
ABSTRACT: The parity-violating cross-section asymmetry in the elastic scattering of
polarized electrons from unpolarized protons has been measured at a
four-momentum transfer squared Q2 = 0.624 GeV and beam energy E =3.48 GeV to be
A_PV = -23.80 +/- 0.78 (stat) +/- 0.36 (syst) parts per million. This result is
consistent with zero contribution of strange quarks to the combination of
electric and magnetic form factors G_E^s + 0.517 G_M^s = 0.003 +/- 0.010 (stat)
+/- 0.004 (syst) +/- 0.009 (ff), where the third error is due to the limits of
precision on the electromagnetic form factors and radiative corrections. With
this measurement, the world data on strange contributions to nucleon form
factors are seen to be consistent with zero and not more than a few percent of
the proton form factors.
07/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: A program of hypernuclear spectroscopy experiments encompassing many hypernuclei has been undertaken in both Halls A and C using complimentary approaches. Spectra with sub-MeV resolution have been obtained for Li, B, and N in Hall A, while results from Hall C include He, B, and Al with new data still under analysis for He, Li, Be, B and V. High resolution and high precision in the determination of the single Λ binding energy at various shell levels has been the key success of these experiments using the (e,e'K+) reaction to produce Λ hypernuclei.
Journal of Physics Conference Series 06/2011; 299(1):012013.
