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Title: Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis

Abstract

The baryon electromagnetic form factors are expressed in terms of two-dimensional densities describing the distribution of charge and magnetization in transverse space at fixed light-front time. In this paper, we calculate the transverse densities of the spin-1/2 flavor-octet baryons at peripheral distances b=O(M$$-1\atop{π}$$) using methods of relativistic chiral effective field theory (χ EFT) and dispersion analysis. The densities are represented as dispersive integrals over the imaginary parts of the form factors in the timelike region (spectral functions). The isovector spectral functions on the two-pion cut t > 4 M$$2\atop{π}$$ are calculated using relativistic χEFT including octet and decuplet baryons. The χEFT calculations are extended into the ρ meson mass region using an N/D method that incorporates the pion electromagnetic form factor data. The isoscalar spectral functions are modeled by vector meson poles. We compute the peripheral charge and magnetization densities in the octet baryon states, estimate the uncertainties, and determine the quark flavor decomposition. Finally, the approach can be extended to baryon form factors of other operators and the moments of generalized parton distributions.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [2];  [3]
  1. Univ. of Bonn (Germany). Bethe Center for Theoretical Physics. Helmholtz Inst. for Radiation and Nuclear Physics; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States). Theory Center
  2. Univ. of Valencia (Spain). Dept. of Theoretical Physics. Inst. for Corpuscular Physics (IFIC)
  3. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States). Theory Center
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Univ. of Bonn (Germany); Univ. of Valencia (Spain)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); German Research Foundation (DFG); Ministry of Economy, Industry and Competitiveness (MINECO) (Spain); European Commission (EC); Generalitat Valenciana
OSTI Identifier:
1356984
Report Number(s):
JLAB-THY-17-2432
Journal ID: ISSN 0375-9474; PII: S0375947417301185; TRN: US1702506
Grant/Contract Number:
AC05-06OR23177; CRC 110; FPA2013-40483-P; FIS2014-51948-C2-2-P; SEV-2014-0398; PROMETEOII/2014/0068
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Physics. A
Additional Journal Information:
Journal Volume: 964; Journal ID: ISSN 0375-9474
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Electromagnetic form factors; Chiral lagrangians; Dispersion relations; Hyperons; Charge distribution

Citation Formats

Alarcón, J. M., Hiller Blin, A. N., Vicente Vacas, M. J., and Weiss, C. Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis. United States: N. p., 2017. Web. doi:10.1016/j.nuclphysa.2017.05.002.
Alarcón, J. M., Hiller Blin, A. N., Vicente Vacas, M. J., & Weiss, C. Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis. United States. doi:10.1016/j.nuclphysa.2017.05.002.
Alarcón, J. M., Hiller Blin, A. N., Vicente Vacas, M. J., and Weiss, C. 2017. "Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis". United States. doi:10.1016/j.nuclphysa.2017.05.002.
@article{osti_1356984,
title = {Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis},
author = {Alarcón, J. M. and Hiller Blin, A. N. and Vicente Vacas, M. J. and Weiss, C.},
abstractNote = {The baryon electromagnetic form factors are expressed in terms of two-dimensional densities describing the distribution of charge and magnetization in transverse space at fixed light-front time. In this paper, we calculate the transverse densities of the spin-1/2 flavor-octet baryons at peripheral distances b=O(M$-1\atop{π}$) using methods of relativistic chiral effective field theory (χ EFT) and dispersion analysis. The densities are represented as dispersive integrals over the imaginary parts of the form factors in the timelike region (spectral functions). The isovector spectral functions on the two-pion cut t > 4 M$2\atop{π}$ are calculated using relativistic χEFT including octet and decuplet baryons. The χEFT calculations are extended into the ρ meson mass region using an N/D method that incorporates the pion electromagnetic form factor data. The isoscalar spectral functions are modeled by vector meson poles. We compute the peripheral charge and magnetization densities in the octet baryon states, estimate the uncertainties, and determine the quark flavor decomposition. Finally, the approach can be extended to baryon form factors of other operators and the moments of generalized parton distributions.},
doi = {10.1016/j.nuclphysa.2017.05.002},
journal = {Nuclear Physics. A},
number = ,
volume = 964,
place = {United States},
year = 2017,
month = 5
}

Journal Article:
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  • Transverse densities describe the distribution of charge and current at fixed light-front time and provide a frame-independent spatial representation of hadrons as relativistic systems. In this paper, we calculate the transverse densities of the octet baryons at peripheral distances b=O(M π -1) in an approach that combines chiral effective field theory (χχEFT) and dispersion analysis. The densities are represented as dispersive integrals of the imaginary parts of the baryon electromagnetic form factors in the timelike region (spectral functions). The spectral functions on the two-pion cut at t>4Mmore » $$2\atop{π}$$ are computed using relativistic χEFT with octet and decuplet baryons in the extended on-mass-shell renormalization scheme. The calculations are extended into the ρ-meson mass region using a dispersive method that incorporates the timelike pion form-factor data. The approach allows us to construct densities at distances b>1 fm with controlled uncertainties. Finally, our results provide insight into the peripheral structure of nucleons and hyperons and can be compared with empirical densities and lattice-QCD calculations.« less
  • We study finite-volume effects on the masses of the ground-state octet baryons using covariant baryon chiral perturbation theory (ChPT) up to next-to-leading order by analyzing the latest n{sub f}=2+1 lattice quantum chromodynamics (LQCD) results from the NPLQCD Collaboration. Contributions of virtual decuplet baryons are taken into account using the consistent coupling scheme. We compare our results with those obtained from heavy baryon ChPT and show that, although both approaches can describe well the lattice data, the underlying physics is different: In heavy baryon ChPT, virtual decuplet baryons play a more important role than they do in covariant ChPT. This ismore » because the virtual octet-baryon contributions to finite-volume corrections are larger in covariant ChPT than in heavy baryon ChPT, while the contributions of intermediate decuplet baryons are smaller, because of relativistic effects. We observe that for the octet-baryon masses, at fixed m{sub {pi}}L (>>1) finite-volume corrections decrease as m{sub {pi}} approaches its physical value, provided that the strange quark mass is at or close to its physical value, as in most lattice quantum chromodynamics setups.« less
  • The magnetic and transition magnetic moments of the ground-state baryons are computed in heavy baryon chiral perturbation theory in the large-N{sub c} limit, where N{sub c} is the number of colors. SU(3) symmetry breaking is systematically studied twofold: On the one hand, one-loop nonanalytic corrections of orders m{sub q}{sup 1/2} and m{sub q} ln m{sub q} are included, with contributions of baryon intermediate states from both flavor octet and flavor decuplet multiplets, assuming degeneracy between baryon states within a given flavor multiplet but nondegeneracy between baryons of different multiplets. On the other hand, perturbative SU(3) symmetry breaking is also analyzedmore » by including all relevant leading-order operators that explicitly break SU(3) at linear order. The resultant expressions are compared with the available experimental data and with other determinations in the context of conventional heavy baryon chiral perturbation theory for three flavors of light quarks and at the physical value N{sub c}=3. The agreement reached is quite impressive.« less