Potterveld, D.H.
DSIG/DOMEGA
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Neutral Pion Electroproduction in the Resonance Region at High $Q^2$

Villano, A.N. ; Stoler, P. ; Bosted, P.E. ; et al.
Phys.Rev.C 80 (2009) 035203, 2009.
Inspire Record 823260 DOI 10.17182/hepdata.54189

The process $ep \to e^{\prime}p^{\prime}\pi^0$ has been measured at $Q^2$ = 6.4 and 7.7 \ufourmomts in Jefferson Lab's Hall C. Unpolarized differential cross sections are reported in the virtual photon-proton center of mass frame considering the process $\gamma^{\ast}p \to p^{\prime}\pi^0$. Various details relating to the background subtractions, radiative corrections and systematic errors are discussed. The usefulness of the data with regard to the measurement of the electromagnetic properties of the well known $\Delta(1232)$ resonance is covered in detail. Specifically considered are the electromagnetic and scalar-magnetic ratios $R_{EM}$ and $R_{SM}$ along with the magnetic transition form factor $G_M^{\ast}$. It is found that the rapid fall off of the $\Delta(1232)$ contribution continues into this region of momentum transfer and that other resonances

125 data tables
Table 1

Differential cross sections at Q**2=6.564 GeV**2, EPSILON=0.4523, W=1.112 GeV and COS(THETA(*))=-0.9 for the small SOS spectrometer.

Table 2

Differential cross sections at Q**2=6.564 GeV**2, EPSILON=0.4523, W=1.112 GeV and COS(THETA(*))=-0.7 for the small SOS spectrometer.

Table 3

Differential cross sections at Q**2=6.564 GeV**2, EPSILON=0.4523, W=1.112 GeV and COS(THETA(*))=-0.5 for the small SOS spectrometer.

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Single pi+ electroproduction on the proton in the first and second resonance regions at 0.25-GeV**2 < Q**2 < 0.65-GeV**2 using CLAS.

The CLAS collaboration Egiyan, H. ; Aznauryan, I.G. ; Burkert, V.D. ; et al.
Phys.Rev.C 73 (2006) 025204, 2006.
Inspire Record 707883 DOI 10.17182/hepdata.6748

The ep -> e'pi^+n reaction was studied in the first and second nucleon resonance regions in the 0.25 GeV^2 < Q^2 < 0.65 GeV^2 range using the CLAS detector at Thomas Jefferson National Accelerator Facility. For the first time the absolute cross sections were measured covering nearly the full angular range in the hadronic center-of-mass frame. The structure functions sigma_TL, sigma_TT and the linear combination sigma_T+epsilon*sigma_L were extracted by fitting the phi-dependence of the measured cross sections, and were compared to the MAID and Sato-Lee models.

345 data tables
Table 1

Structure functions for Q**2 = 0.30 GeV**2 and W = 1.11 GeV.

Table 2

Structure functions for Q**2 = 0.30 GeV**2 and W = 1.13 GeV.

Table 3

Structure functions for Q**2 = 0.30 GeV**2 and W = 1.15 GeV.

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Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1-GeV to 5.5-GeV.

The Jefferson Lab Hall A & Jefferson Lab E94-104 collaborations Zhu, L.Y. ; Arrington, J. ; Averett, T. ; et al.
Phys.Rev.C 71 (2005) 044603, 2005.
Inspire Record 659852 DOI 10.17182/hepdata.31680

The differential cross section for the gamma +n --> pi- + p and the gamma + p --> pi+ n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50 degree to 110 degree. The pi- and pi+ photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi+ data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.

14 data tables
Table 1

Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 5.614 GeV.

Table 2

Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 4.236 GeV.

Table 3

Differential cross section for the process GAMMA N --> PI- P for an incident electron energy of 3.400 GeV.

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Near threshold electroproduction of the omega meson at Q**2 approx. 0.5-GeV**2.

The Jefferson Laboratory E91-016 collaboration Ambrozewicz, P. ; Mitchell, J. ; Dunne, J. ; et al.
Phys.Rev.C 70 (2004) 035203, 2004.
Inspire Record 645605 DOI 10.17182/hepdata.31643

Electroproduction of the omega meson was investigated in the p(e,e'p)omega reaction. The measurement was performed at a 4-momentum transfer Q2 ~ 0.5 GeV2. Angular distributions of the virtual photon-proton center-of-momentum cross sections have been extracted over the full angular range. These distributions exhibit a strong enhancement over t-channel parity exchange processes in the backward direction. According to a newly developed electroproduction model, this enhancement provides significant evidence of resonance formation in the gamma* p -> omega p reaction channel.

2 data tables
Table 1

Differential cross section for an average W of 1.75 GeV.

Table 2

Differential cross section for an average W of 1.79 GeV.


Measurements of electron proton elastic cross sections for 0.4-(GeV/c)**2 < Q**2 < 5.5-(GeV/c)**2.

The E94110 collaboration Christy, M.E. ; Ahmidouch, A. ; Armstrong, C.S. ; et al.
Phys.Rev.C 70 (2004) 015206, 2004.
Inspire Record 643262 DOI 10.17182/hepdata.31763

We report on precision measurements of the elastic cross section for electron-proton scattering performed in Hall C at Jefferson Lab. The measurements were made at 28 unique kinematic settings covering a range in momentum transfer of 0.4 $<$ $Q^2$ $<$ 5.5 $(\rm GeV/c)^2$. These measurements represent a significant contribution to the world's cross section data set in the $Q^2$ range where a large discrepancy currently exists between the ratio of electric to magnetic proton form factors extracted from previous cross section measurements and that recently measured via polarization transfer in Hall A at Jefferson Lab.

7 data tables
Table 1

Measured values of the electron-proton elastic cross section for beam energy 1.148 GeV.

Table 2

Measured values of the electron-proton elastic cross section for beam energy 1.882 GeV.

Table 3

Measured values of the electron-proton elastic cross section for beam energy 2.235 GeV.

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Hard photon production and tests of QED at LEP

The L3 collaboration Acciarri, M. ; Achard, P. ; Adriani, O. ; et al.
Phys.Lett.B 475 (2000) 198-205, 2000.
Inspire Record 513397 DOI 10.17182/hepdata.48965

The total and differential cross sections of the process e+e- -> n gamma with n >= 2 are measured using data collected by the L3 experiment at centre-of-mass energies of \sqrt{s}=183 and 189 GeV. The results are in agreement with the Standard Model expectations. Limits are set on deviations from QED, contact interaction cut-off parameters and masses of excited electrons.

2 data tables
Table 1

Measured cross section.

Table 2

Measured differential cross sections corrected for efficiency and additional photons as a function of cos(theta) where theta is the polar angle of the event defined as. cos(theta)=ABS((sin(theta1-theta2)/2)/(sin(theta1+theta2)/2)).


Longitudinal and transverse cross sections in the H-1(e,e' K+)Lambda reaction.

Niculescu, G. ; Mohring, R.M. ; Gueye, P. ; et al.
Phys.Rev.Lett. 81 (1998) 1805-1808, 1998.
Inspire Record 479881 DOI 10.17182/hepdata.19546

The 1H(e,e′K+)Λ reaction was studied as a function of the squared four-momentum transfer, Q2, and the virtual photon polarization, ɛ. For each of four Q2 settings, 0.52, 0.75, 1.00, and 2.00 (GeV/c)2, the longitudinal and transverse virtual photon cross sections were extracted in measurements at three virtual photon polarizations. The Q2 dependence of the σL/σT ratio differs significantly from current theoretical predictions. This, combined with the precision of the measurement, implies a need for revision of existing calculations.

1 data table
Table 1

The systematic and statistical errors are added in quadrature. OMEGA is the solid angle of K+ in CMS.


Two body photodisintegration of the deuteron up to 2.8-GeV

Belz, J.E. ; Potterveld, D.H. ; Anthony, P. ; et al.
Phys.Rev.Lett. 74 (1995) 646-649, 1995.
Inspire Record 399936 DOI 10.17182/hepdata.19630

Measurements were performed for the photodisintegration cross section of the deuteron for photon energies from 1.6 to 2.8 GeV and center-of-mass angles from 37° to 90°. The measured energy dependence of the cross section at θc.m.=90° is in agreement with the constituent counting rules.

1 data table
Table 1

Statistical and systematic errors have been added in quadrature. Photon energy and angle (in deg) are in center-of-mass system.


Measurements of the proton elastic form-factors for 1-GeV/c**2 <= Q**2 <= 3-GeV/C**2 at SLAC

Walker, R.C. ; Filippone, B. ; Jourdan, J. ; et al.
Phys.Rev.D 49 (1994) 5671-5689, 1994.
Inspire Record 360764 DOI 10.17182/hepdata.22469

We report measurements of the proton form factors GEp and GMp extracted from elastic scattering in the range 1≤Q2≤3 (GeV/c)2 with total uncertainties < 15% in GEp and < 3% in GMp. Comparisons are made to theoretical models, including those based on perturbative QCD, vector-meson dominance, QCD sum rules, and diquark constituents in the proton. The results for GEp are somewhat larger than indicated by most theoretical parametrizations, and the ratios of the Pauli and Dirac form factors Q2(F2pF1p) are lower in value and demonstrate a weaker Q2 dependence than those predictions. A global extraction of the elastic form factors from several experiments in the range 0.1 0.1<Q2<10 (GeV/c)2 is also presented.

6 data tables
Table 1

Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.

Table 2

Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.

Table 3

Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.

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Two-body disintegration of the deuteron with 0.8-GeV to 1.8-GeV photons

Freedman, S.J. ; Geesaman, D.F. ; Gilman, Ronald A. ; et al.
Phys.Rev.C 48 (1993) 1864-1878, 1993.
Inspire Record 365233 DOI 10.17182/hepdata.26023

The differential cross section for the reaction H2(γ,p)n has been measured at several center-of-mass angles ranging from 50° to 143° for photon energies between 0.8 and 1.8 GeV. The experiment was performed at the SLAC-NPAS facility with the use of the 1.6 GeV/c spectrometer to detect the high energy protons produced by a bremsstrahlung beam directed at a liquid deuterium target. Contributions from concurrent disintegration by the residual electron beam were determined by measuring the proton yield without the Cu photon radiator. At angles not very far from 90°, the energy dependence of the cross sections is consistent with predictions of scaling using counting rules for constituent quarks. At least one theoretical calculation based on a meson-baryon picture of the reaction is able to reproduce the magnitude and energy dependence of the 90° cross section. The angular distribution exhibits a large enhancement at backward angles at the higher energies.

1 data table
Table 1

THE QUOTED ERRORS ARE STATISTICAL ONLY.