Constituent-Quark Model with Pionic Contributions: Electromagnetic N → Δ Transition

We report on ongoing work to determine the pion-cloud contribution to the electromagnetic N → Δ transition form factors. The starting point is an SU ( 6 ) spin-flavor symmetric constituent-quark model with instantaneous confinement that is augmented by dynamical pions which couple directly to the quarks. This system is treated in a relativistically invariant way within the framework of point-form quantum mechanics using a multichannel formulation. The first step is to determine the electromagnetic form factors of the bare particles that consist only of three quarks. These form factors are basic ingredients for calculating the pion-cloud contributions. Already without the pion cloud, electromagnetic nucleon and N → Δ transition form factors compare reasonably well with the data. By inclusion of the pion-cloud contribution coming from the π − N intermediate state the reproduction of the data is further improved.

[1]  P. Forcrand,et al.  N-to-delta electromagnetic-transition form factors from lattice QCD. , 2004, hep-lat/0409122.

[2]  C. Fischer,et al.  Electromagnetic transition form factors of baryons in the space-like momentum region , 2017, The European Physical Journal A.

[3]  W. Schweiger,et al.  On the Microscopic Structure of π NN , π N (cid:3) and π (cid:3)(cid:3) Vertices , 2017 .

[4]  Nuruzzaman,et al.  Electroexcitation of the Δ+(1232) at low momentum transfer , 2015, 1509.00780.

[5]  W. Schweiger,et al.  The Pion-Cloud Contribution to the Electromagnetic Nucleon Form Factors , 2015, 1508.03991.

[6]  D. Wilson,et al.  STUDIES OF NUCLEON RESONANCE STRUCTURE IN EXCLUSIVE MESON ELECTROPRODUCTION , 2012, 1212.4891.

[7]  E. Santopinto,et al.  Systematic study of longitudinal and transverse helicity amplitudes in the hypercentral constituent quark model , 2012, 1506.01207.

[8]  W. Schweiger,et al.  Electroweak form factors of heavy-light mesons: A relativistic point-form approach , 2012, 1206.1257.

[9]  W. Schweiger,et al.  Point-Form Hamiltonian Dynamics and Applications , 2010, 1008.0244.

[10]  I. Aznauryan,et al.  Electroexcitation of Nucleon Resonances from CLAS Data on Single Pion Electroproduction , 2009, 0909.2349.

[11]  W. Schweiger,et al.  Electromagnetic meson form factor from a relativistic coupled-channels approach , 2009, 0902.2348.

[12]  T. Ledwig,et al.  Electromagnetic properties of the Delta(1232) and decuplet baryons in the self-consistent SU(3) chiral quark-soliton model , 2008, 0811.3086.

[13]  S. Boffi,et al.  Electroweak structure of the nucleon, meson cloud, and light-cone wave functions , 2007, 0707.2897.

[14]  S. Yang,et al.  Electromagnetic excitation of the Δ(1232)-resonance , 2006, hep-ph/0609004.

[15]  L. Tiator,et al.  Electroproduction of nucleon resonances , 2003, nucl-th/0310041.

[16]  B. Desplanques,et al.  Explicitly covariant light-front dynamics and relativistic few-body systems , 1998, nucl-th/9804029.

[17]  S. Simula,et al.  Nucleon and pion electromagnetic form-factors in a light front constituent quark model , 1995, nucl-th/9507037.

[18]  S. Sokolov.  Relativistic addition of direct interactions in the point form of dynamics , 1978 .