-
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. 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;
-
F. Cusanno,
A. Acha,
P. Bydzovsky, C C Chang,
E. Cisbani,
C W de Jager,
R. De Leo,
S. Frullani,
F. Garibaldi,
D. W. Higinbotham,
M. Iodice,
J. J. LeRose,
P. Markowitz,
S. Marrone,
M. Sotona,
G. M. Urciuoli,
for the Hall A Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Updated results of the experiment E94-107 hypernuclear spectroscopy in Hall A
of the Thomas Jefferson National Accelerator Facility (Jefferson Lab), are
presented. The experiment provides high resolution spectra of excitation energy
for 12B_\Lambda, 16N_\Lambda, and 9Li_\Lambda hypernuclei obtained by
electroproduction of strangeness. A new theoretical calculation for
12B_\Lambda, final results for 16N_\Lambda, and discussion of the preliminary
results of 9Li_\Lambda are reported.
11/2009;
-
M. Coman,
P. Markowitz,
K. A. Aniol,
K Baker,
W. U. Boeglin,
H. Breuer,
P. Bydzovsky,
A. Camsonne,
J. Cha, C C Chang, [......],
G. M. Urciuoli,
A. Uzzle,
A Vacheret,
K Wang,
K. Wijesooriya,
B Wojtsekhowski,
S. Wood,
I. Yaron,
X Zheng,
L Zhu
[show abstract]
[hide abstract]
ABSTRACT: The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT, cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL. Comment: 5 pages, 4 figures. Submitted to Physical Review C, Rapid Communications
11/2009;
-
F Cusanno,
G M Urciuoli,
A Acha,
P Ambrozewicz,
K A Aniol,
P Baturin,
P Y Bertin,
H Benaoum,
K I Blomqvist,
W U Boeglin, [......],
R Subedi,
V A Sulkosky,
T Suzuki,
H Ueno,
P E Ulmer,
P Veneroni,
E Voutier,
B B Wojtsekhowski,
X Zheng,
C Zorn
[show abstract]
[hide abstract]
ABSTRACT: An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K(+))Lambda, Sigma(0) exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76+/-0.16 MeV was obtained for (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p(1/2) and p(3/2) hole states of the (15)N core nucleus.
Physical Review Letters 11/2009; 103(20):202501. · 7.37 Impact Factor
-
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 Solvignon,
N Liyanage,
J-P Chen,
Seonho Choi,
K Aniol,
T Averett,
W Boeglin,
A Camsonne,
G D Cates, C C Chang, [......],
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 experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_{1} of the neutron and 3He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c);{2}. Global duality is observed for the spin-structure function g_{1} down to at least Q;{2}=1.8 (GeV/c);{2} in both targets. We have also formed the photon-nucleon asymmetry A1 in the resonance region for 3He and found no strong Q2 dependence above 2.2 (GeV/c);{2}.
Physical Review Letters 11/2008; 101(18):182502. · 7.37 Impact Factor
-
F. Cusanno,
G. M. Urciuoli,
A. Acha,
P Ambrozewicz,
K. A. Aniol,
P. Baturin,
P Y Bertin,
H Benaoum,
K. I. Blomqvist,
W. U. Boeglin, [......],
R. Subedi,
V. A. Sulkosky,
T Suzuki,
H Ueno,
P E Ulmer,
P Veneroni,
E. Voutier,
B. B. Wojtsekhowski,
X. Zeng,
C. Zorn
[show abstract]
[hide abstract]
ABSTRACT: An experimental study of the 16O(e,e'K^+)16N_Lambda reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K^+)Lambda,Sigma_0 exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76 +/- 0.16 MeV was obtained for 16N_Lambda with better precision than previous measurements on the mirror hypernucleus 16O_Lambda. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p_{1/2} and p_{3/2} hole states of the 15N core nucleus. Comment: 5 pages, 3 figures, 2 tables
10/2008;
-
H.P. Blok,
T. Horn,
G. M. Huber,
E. J. Beise,
D. Gaskell,
D. J. Mack,
V. Tadevosyan,
J Volmer,
D. Abbott,
K. Aniol, [......],
D. Van Westrum,
S. Vidakovic,
W. Vulcan,
G. Warren,
S. A. Wood,
C Xu,
C Yan,
W. -X. Zhao,
X Zheng,
B. Zihlmann
[show abstract]
[hide abstract]
ABSTRACT: Cross sections for the reaction ${^1}$H($e,e'\pi^+$)$n$ were measured in Hall C at Thomas Jefferson National Accelerator Facility (JLab) using the CEBAF high-intensity, continous electron beam in order to determine the charged pion form factor. Data were taken for central four-momentum transfers ranging from $Q^2$=0.60 to 2.45 GeV$^2$ at an invariant mass of the virtual photon-nucleon system of $W$=1.95 and 2.22 GeV. The measured cross sections were separated into the four structure functions $\sigma_L$, $\sigma_T$, $\sigma_{LT}$, and $\sigma_{TT}$. The various parts of the experimental setup and the analysis steps are described in detail, including the calibrations and systematic studies, which were needed to obtain high precision results. The different types of systematic uncertainties are also discussed. The results for the separated cross sections as a function of the Mandelstam variable $t$ at the different values of $Q^2$ are presented. Some global features of the data are discussed, and the data are compared with the results of some model calculations for the reaction ${^1}$H($e,e'\pi^+$)$n$.
10/2008;
-
G. M. Huber,
H. P. Blok,
T. Horn,
E. J. Beise,
D. Gaskell,
D. J. Mack,
V. Tadevosyan,
J. Volmer,
D. Abbott,
K. Aniol, [......],
D. Van Westrum,
S. Vidakovic,
W. Vulcan,
G. Warren,
S. A. Wood,
C. Xu,
C. Yan,
W.-X. Zhao,
X. Zheng,
B. Zihlmann
[show abstract]
[hide abstract]
ABSTRACT: The charged pion form factor, Fπ(Q2), is an important quantity that can be used to advance our knowledge of hadronic structure. However, the extraction of Fπ from data requires a model of the 1H(e,e'π+)n reaction and thus is inherently model dependent. Therefore, a detailed description of the extraction of the charged pion form factor from electroproduction data obtained recently at Jefferson Lab is presented, with particular focus given to the dominant uncertainties in this procedure. Results for Fπ are presented for Q2=0.60-2.45 GeV2. Above Q2=1.5 GeV2, the Fπ values are systematically below the monopole parametrization that describes the low Q2 data used to determine the pion charge radius. The pion form factor can be calculated in a wide variety of theoretical approaches, and the experimental results are compared to a number of calculations. This comparison is helpful in understanding the role of soft versus hard contributions to hadronic structure in the intermediate Q2 regime.
Phys. Rev. C. 10/2008; 78(4).
-
H. P. Blok,
T. Horn,
G. M. Huber,
E. J. Beise,
D. Gaskell,
D. J. Mack,
V. Tadevosyan,
J. Volmer,
D. Abbott,
K. Aniol, [......],
D. Van Westrum,
S. Vidakovic,
W. Vulcan,
G. Warren,
S. A. Wood,
C. Xu,
C. Yan,
W.-X. Zhao,
X. Zheng,
B. Zihlmann
[show abstract]
[hide abstract]
ABSTRACT: Cross sections for the reaction 1H(e,e'π+)n were measured in Hall C at Thomas Jefferson National Accelerator Facility (JLab) using the high-intensity Continuous Electron Beam Accelerator Facility (CEBAF) to determine the charged pion form factor. Data were taken for central four-momentum transfers ranging from Q2=0.60 to 2.45 GeV2 at an invariant mass of the virtual photon-nucleon system of W=1.95 and 2.22 GeV. The measured cross sections were separated into the four structure functions σL,σT,σLT, and σTT. The various parts of the experimental setup and the analysis steps are described in detail, including the calibrations and systematic studies, which were needed to obtain high-precision results. The different types of systematic uncertainties are also discussed. The results for the separated cross sections as a function of the Mandelstam variable t at the different values of Q2 are presented. Some global features of the data are discussed, and the data are compared with the results of some model calculations for the reaction 1H(e,e'π+)n.
Phys. Rev. C. 10/2008; 78(4).
-
John J. LeRose,
A. Acha,
P. Bydzovsky,
C. Chang, C.C. Chang,
E. Cisbani,
F. Cusano,
C.W. de Jager,
R. De Leo,
R.J. Feuerbach, [......],
F. Garibaldi,
D.W. Higinbotham,
M. Iodice,
L. Lagamba,
P. Markowitz,
S. Marrone,
B. Reitz,
M. Sotona,
Miloslav Sotona,
G.M. Urciuoli
[show abstract]
[hide abstract]
ABSTRACT: Results are presented from a new experiment (E94-107) in Hall A of the Thomas Jefferson National Accelerator Facility (JLab) producing {12/Lambda} B, {16/Lambda}N, and {9/Lambda}Li using electroproduction, (e,e'K+). In the hypernuclear missing-mass spectrum the experiment achieves very good energy resolution (670 keV FWHM) by exploiting the characteristics of the High Resolution spectrometer pair and the exceptional beam quality available at JLab. The spectrometers were used with the addition an INFN provided pair of septum magnets to reach the desired small angles. Also, the Hall A standard complement of equipment was further augmented by the addition of a Ring Imaging Cherenkov detector (RICH) to achieve the best possible kaon identification.
12/2007;
-
M Iodice,
F Cusanno,
A Acha,
P Ambrozewicz,
K A Aniol,
P Baturin,
P Y Bertin,
H Benaoum,
K I Blomqvist,
W U Boeglin, [......],
H Ueno,
P E Ulmer,
G M Urciuoli,
P Veneroni,
E Voutier,
B B Wojtsekhowski,
Y Ye,
X Zheng,
S Zhou,
C Zorn
[show abstract]
[hide abstract]
ABSTRACT: An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.
Physical Review Letters 09/2007; 99(5):052501. · 7.37 Impact Factor
-
M. Iodice,
F. Cusanno,
A. Acha,
P Ambrozewicz,
K. A. Aniol,
P. Baturin,
P Y Bertin,
H Benaoum,
K. I. Blomqvist,
W. U. Boeglin, [......],
V. A. Sulkosky,
T Suzuki,
H Ueno,
P E Ulmer,
G. M. Urciuoli,
P Veneroni,
E. Voutier,
B. B. Wojtsekhowski,
X Zheng,
C. Zorn
[show abstract]
[hide abstract]
ABSTRACT: An experiment measuring electroproduction of hypernuclei has been performed in Hall A at Jefferson Lab on a $^{12}$C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed \lam{12}{B} spectrum shows for the first time identifiable strength in the core-excited region between the ground-state {\it s}-wave $\Lambda$ peak and the 11 MeV {\it p}-wave $\Lambda$ peak.
06/2007;
-
A Danagoulian,
V H Mamyan,
M Roedelbronn,
K A Aniol,
J R M Annand,
P Y Bertin,
L Bimbot,
P Bosted,
J R Calarco,
A Camsonne, [......],
V Sulkosky,
L Todor,
B Vlahovic,
L B Weinstein,
K Wang,
B Wojtsekhowski,
H Voskanyan,
H Xiang,
X Zheng,
L Zhu
[show abstract]
[hide abstract]
ABSTRACT: Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s=5-11 and -t=2-7 GeV2 with a statistical accuracy of a few percent. The scaling power for the s dependence of the cross section at fixed center-of-mass angle was found to be 8.0+/-0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.
Physical Review Letters 05/2007; 98(15):152001. · 7.37 Impact Factor
-
F. Cusanno,
A. Acha,
P. Bydžovský, C. C. Chang,
E. Cisbani,
C. W. De Jager,
R. De Leo,
R. J. Feuerbach,
S. Frullani,
F. Garibaldi,
D. W. Higinbotham,
M. Iodice,
L. Lagamba,
J. J. LeRose,
P. Markowitz,
S. Marrone,
B. Reitz,
M. Sotona,
G. M. Urciuoli
[show abstract]
[hide abstract]
ABSTRACT: The E94-107 experiment in Hall A at Jefferson Lab has started a systematic study of 1p-shell hypernuclei. Data have been taken
on C-12, Be-9 and O-16 targets. The counting rate for hypernuclear electroproduction decreases dramatically as the scattering
angle increases. Therefore, the electron scattering angle has to be as forward as possible to get high virtual photon flux
and kaon angle has to be as close as possible to the virtual photon direction to minimize momentum transfer. In order to allow
experiments at very forward angle in Hall A, two superconducting septum magnets were added to the High Resolution Spectrometers
(HRS). The two magnets bend particles scattered at 6° into each HRS, introducing only a small perturbation on the HRS optics
thus preserving the excellent momentum resolution of the HRS. With the new setup a momentum resolution of 10−4 FWHM on both HRS arms was obtained. One of the challenges of the experiment at very forward angle is the identification of
very small peaks in the missingenergy spectrum; this requires a powerful Particle Identification (PID) system that provides
unambiguous kaon selection.
12/2006: pages 37-40;
-
J. J. LeRose,
A. Acha,
P. Bydžovský, C. C. Chang,
E. Cisbani,
F. Cusanno,
C. W. de Jager,
R. De Leo,
R. J. Feuerbach,
S. Frullani,
F. Garibaldi,
D. W. Higinbotham,
M. Iodice,
L. Lagamba,
P. Markowitz,
S. Marrone,
B. Reitz,
M. Sotona,
G. M. Urciuoli,
The Hall A Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Results are presented from a new experiment (E94-107) in Hall A of the Thomas Jefferson National Accelerator Facility (JLab)
producing
Λ
12
B using electroproduction, (e,e’K+). In the hypernuclear missing-mass spectrum the experiment achieves very good energy resolution (640 keV FWHM) by exploiting
the characteristics of the High Resolution spectrometer pair and the exceptional beam quality available at JLab. The spectrometers
were used with the addition an INFN provided pair of septum magnets to reach the desired small angles. Also, the Hall A standard
complement of equipment was further augmented by the addition of a Ring Imaging Cherenkov detector (RICH) to achieve the best
possible kaon identification.
12/2006: pages 29-32;
-
T Horn,
K Aniol,
J Arrington,
B Barrett,
E J Beise,
H P Blok,
W Boeglin,
E J Brash,
H Breuer, C C Chang, [......],
V Tadevosyan,
L G Tang,
V Tvaskis,
S Vidakovic,
J Volmer,
W Vulcan,
G Warren,
S A Wood,
C Xu,
X Zheng
[show abstract]
[hide abstract]
ABSTRACT: The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F(pi)) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F(pi) is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction.
Physical Review Letters 12/2006; 97(19):192001. · 7.37 Impact Factor
