Baryonic content of the pion

Abstract

The baryon form factor of charged pions arises since isospin symmetry is broken with unequal up and down quark masses, $m_d>m_u$, as well as electromagnetic effects. We obtain estimates for this basic property in two phenomenological ways: from simple constituent quark models, as well as from fitting the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ data. All our methods yield the result that the baryon mean square radius, extracted from the slope of the form factor, is positive for ${\pi }^{+}$, hence a picture where the outer region has a net baryon, and the inner region a net antibaryon density, both compensating each other such that the total baryon number is zero. For ${\pi }^{-}$ the effect is equal and opposite. We estimate the corresponding mean squared baryon radius as $⟨r^2{⟩}_B^{{\pi }^{+}}=(0.03-0.04\mathrm{fm}{)}^2$.

arXiv comment7 pages, 5 figures; references and figures added; extended discussions; version accepted for publication in PLB

References in corpus (31)

• Impact Parameter Dependent Parton Distributions and Off-Forward Parton Distributions for $\zeta \to 0$
• The Mesonic Chiral Lagrangian of Order $p^6$
• Precise measurement of the e+ e- to pi+ pi- (gamma) cross section with the Initial State Radiation method at BABAR
• Precise Measurement of the e+ e- --> pi+ pi- (gamma) Cross Section with the Initial-State Radiation Method at BABAR
• rho^0-gamma mixing in the neutral channel pion form factor |F_pi|^2 and its role in comparing e^+ e^- with tau spectral functions
• Electromagnetic structure of the deuteron
• Measurement of $\sigma (e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\gamma )$ and extraction of $\sigma (e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-})$ below 1 {\rm GeV} with the KLOE detector
• High-Statistics Study of the tau^- -> pi^- pi^0 nu_tau Decay
• Measurement of sigma(e+ e- -> pi+ pi-) from threshold to 0.85 GeV^2 using Initial State Radiation with the KLOE detector
• Measurement of $\sigma (e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\gamma (\gamma ))$ and the dipion contribution to the muon anomaly with the KLOE detector
• The Discrepancy Between tau and e+e- Spectral Functions Revisited and the Consequences for the Muon Magnetic Anomaly
• Transverse Charge Densities
• Isospin Violation and the Magnetic Moment of the Muon
• Radiative tau decay and the magnetic moment of the muon
• Precise charm to strange mass ratio and light quark masses from full lattice QCD
• Precision Measurement of the e+e- --> K+K-(gamma) Cross Section with the Initial-State Radiation Method at BaBar
• Isospin violating effects in e+e- vs. tau measurements of the pion form factor |F_pi|^2 (s)
• Charge Distributions of Moving Nucleons
• The Dipion Mass Spectrum In e+e- Annihilation and tau Decay: A Dynamical (rho0, omega, phi) Mixing Approach
• Ambiguities in the definition of local spatial densities in light hadrons
• Cross sections for the reactions $e^{+}{e}^{-}\to K_S^0{K}_L^0$, $K_S^0{K}_L^0{\pi }^{+}{\pi }^{-}$, $K_S^0{K}_S^0{\pi }^{+}{\pi }^{-}$, and $K_S^0{K}_S^0{K}^{+}{K}^{-}$ from events with initial-state radiation
• New $\tau$-based evaluation of the hadronic contribution to the vacuum polarization piece of the muon anomalous magnetic moment
• The branching ratio $\omega \to {\pi }^{+}{\pi }^{-}$ revisited
• Pion form factor and charge radius from Lattice QCD at physical point
• Stranger in the Light: The Strange Vector Form Factors of the Nucleon
• Just How Strange? Loops, Poles and the Strangeness Radius of the Nucleon
• Lattice Calculation of Pion Form Factor with Overlap Fermions
• Consequences of the BaBar e^+e^- --> pi^+pi^- Measurement for the Determination of Model-Dependent rho-omega Mixing Effects in Pi_{ρω}(m_ρ^2) and (g-2)_mu
• Models of Isospin Breaking in the Pion Form Factor: Consequences for the Determination of Pi_{ρω}(m_rho^2) and (g-2)_mu/2
• Isospin Breaking in the Relation Between the tau-->nu_tau pi pi and e^+e^- -->pi^+ pi^- Versions of |F_π(s)|^2$ and Implications for (g-2)_mu
• Equivalence Between Vector Meson Dominance and Unitarised Chiral Perturbation Theory

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