Empirical fit to precision inclusive electron-proton cross sections in the resonance region

Christy, M. E.; Bosted, P.

doi:10.1103/physrevc.81.055213

Cited by 203 publications

(314 citation statements)

References 15 publications

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“…Our approach to Fermi-smearing is explained in Section II G. Here, we just summarize our sources of data for the fits to A 2 and A 1 for the proton and the neutron. For the unpolarized structure functions F p,n 1 and R p,n , we used a recent parametrization of the world data by Bosted and Christy [67,89]. This parametrization fits both DIS and resonance-region data with an average precision of 2-5%, including Jefferson Lab Hall C data on the proton and the deuteron with very similar kinematics to ours.…”

Section: Modelsmentioning

confidence: 99%

“…Inclusive scattering data from the empty (LHe) and 12 C targets were analyzed to determine the total target cell length (L) and effective ND 3 thickness ( A ) using similar equations. The required cross-sections were calculated from a fit to world data for F 1 and F 2 for protons and neutrons, using a Fermi-convolution model to fit inclusive scattering data on nuclear targets, including EG1b data from 12 C, solid 15 N and empty (LHe) targets [67,68]. The nuclear EMC effect was parametrized using SLAC data [69].…”

Section: Dilution Factormentioning

confidence: 99%

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Precise determination of the deuteron spin structure at low to moderateQ2with CLAS and extraction of the neutron contribution

Guler¹,

Fersch²,

Kuhn³

et al. 2015

Phys. Rev. C

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Precise determination of the deuteron spin structure at low to moderate Q^{2} with CLAS and extraction of the neutron contribution We present the final results for the deuteron spin structure functions obtained from the full data set collected with Jefferson Lab's CLAS in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2 and 5.8 GeV were scattered from deuteron ( 15 ND3) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double spin asymmetry, the virtual photon absorption asymmetry A d 1 and the polarized structure function g d 1 were extracted over a wide kinematic range (0.05 GeV 2 < Q 2 < 5 GeV 2 and 0.9 GeV < W < 3 GeV). We use an unfolding procedure and a parametrization of the corresponding proton results to extract from these data the polarized structure functions A n 1 and g n 1 of the (bound) neutron, which are so far unknown in the resonance region, W < 2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x, a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the Operator Product Expansion.

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Section: Modelsmentioning

confidence: 99%

Section: Dilution Factormentioning

confidence: 99%

Precise determination of the deuteron spin structure at low to moderateQ2with CLAS and extraction of the neutron contribution

Guler¹,

Fersch²,

Kuhn³

et al. 2015

Phys. Rev. C

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“…(12), most of the support for the integrals lies in the resonance region, where there are good data from JLab, and there are analytic fits valid in the resonance region for both the neutron and proton structure functions from Bosted and Christy [45,46] (we also remind the reader the neutron functions are determined from deuterium-Compton scattering with the additional uncertainties captured in the coefficients of the neutron functions, and propagated into our uncertainties through a Monte-Carlo treatment). Their quoted range of validity includes Q 2 up to 8 GeV 2 and W up to 3.1 GeV (W 2 = M 2 + 2M ν − Q 2 ).…”

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confidence: 99%

Electromagnetic Self-Energy Contribution toMp−Mnand the Isovector Nucleon Magnetic Polarizability

2012

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We update the determination of the isovector nucleon electromagnetic self-energy, valid to leading order in QED. A technical oversight in the literature concerning the elastic contribution to Cottingham's formula is corrected and modern knowledge of the structure functions is used to precisely determine the inelastic contribution. We find δM γ p−n = 1.30(03)(47) MeV. The largest uncertainty arises from a subtraction term required in the dispersive analysis, which can be related to the isovector magnetic polarizability. With plausible model assumptions, we can combine our calculation with additional input from lattice QCD to constrain this polarizability as: βp−n = −0.87(85) × 10 −4 fm 3 .PACS numbers: 13.40. Dk, 13.40.Ks, 13.60.Fz, 14.20.Dh Given only electrostatic forces, one would predict that the proton is more massive than the neutron but the opposite actually occurs [1-3]:Before we knew of quarks and gluons there were many attempts to explain this contradiction, see Ref.[4] for a review. We now know there are two sources of isospin breaking in the standard model, the masses of the up and down quarks as well as the electromagnetic interactions between quarks governed by the charge operator. The effects of the mass difference between down and up quarks are larger and of the opposite sign than those of electromagnetic effects, see the reviews [5][6][7]. The net result of the quark mass difference and electromagnetic effects is well known, Eq. (1), but our ability to disentangle the contributions from these two sources remains poorly constrained. In contrast, lattice QCD calculations have matured significantly. There are now calculations performed with the light quark masses at or near their physical values [8][9][10][11][12], reproducing the ground state hadron spectrum within a few percent. These advances have allowed for calculations to begin including explicit isospin breaking effects from both the quark masses [13][14][15][16][17] and electromagnetism [15,[18][19][20][21]. While the lattice calculations of m d − m u effects are robust, the contributions from electromagnetism are less mature and suffer from larger systematics, due in large part to the disparity between the photon mass and a typical hadronic scale. Improved knowledge of m d − m u and its effects in nucleons will enhance the ability to use effective field theory to compute a variety of isospin-violating (charge asymmetric) effects in nuclear reactions [7,[22][23][24][25][26][27]].An application [28] of the Cottingham sum rule [29], which relates the electromagnetic self-energy of the nucleon to measured elastic and inelastic cross sections, gives the result δM γ p−n = 0.76 ± 0.30 MeV. Given the high present interest in the precise value of δM γ p−n and its many possible implications, it is worthwhile to revisit this result. Many high quality electron scattering experiments have been performed since 1975 and there have also been theoretical advances. The central aim of this work is to provide a modern, robust evaluation of δM γ p−n . We wil...

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“…In our previous work we modified the Christy and Bosted fit to electromagnetic data [11] in the the resonance region Q 2 < 8 GeV 2 and W < 2.5 GeV. Their fits for F γγ 1 , σ T , and σ L account for the contributions of seven resonances as well as a smooth background.…”

Section: Modification Of the Structure Functionsmentioning

confidence: 99%

Modification of electromagnetic structure functions for theγZ-box diagram

Rislow

Carlson

2013

Phys. Rev. D

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The γZ-box diagram for parity violating elastic e-p scattering has recently undergone a thorough analysis by several research groups. Though all now agree on the analytic form of the diagram, the numerical results differ due to the treatment of the structure functions,W 2 must be approximated through the modification of existing fits to electromagnetic structure function data. We motivate and describe the modification used to obtain F γZ 1,2 (x, Q 2 ) in our previous work. We also describe an alternative modification and compare the result to our original calculation. Finally, we present a new modification procedure to acquire F γZ 3 (x, Q 2 ) in the resonance region and calculate the axial contribution to the γZ-box diagram. Details of these modifications will illuminate where discrepancies between the groups arise and where future improvements can be made.

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Empirical fit to precision inclusive electron-proton cross sections in the resonance region

Cited by 203 publications

References 15 publications

Precise determination of the deuteron spin structure at low to moderateQ2with CLAS and extraction of the neutron contribution

Precise determination of the deuteron spin structure at low to moderateQ2with CLAS and extraction of the neutron contribution

Electromagnetic Self-Energy Contribution toMp−Mnand the Isovector Nucleon Magnetic Polarizability

Modification of electromagnetic structure functions for theγZ-box diagram

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