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Title: Meson electro-/photo-production from QCD

I present the calculation of the $$\pi^+\gamma^\star\to\pi^+\pi^0$$ transition amplitude from quantum chromodynamics performed by the Hadron Spectrum Collaboration. The amplitude is determined for a range of values of the photon virtuality and the final state energy. One observes a clear dynamical enhancement due to the presence of the $$\rho$$ resonance. By fitting the transition amplitude and analytically continuing it onto the $$\rho$$-pole, the $$\rho\to\pi\gamma^\star$$ form factor is obtained. This exploratory calculation, performed using lattice quantum chromodynamics, constitutes the very first determination of an electroweak decay of a hadronic resonance directly from the fundamental theory of quarks and gluons. In this talk, I highlight some of the necessary steps that made this calculation possible, placing emphasis on recently developed formalism. In conclusion, I discuss the status and outlook of the field for the study of $$N\gamma^\star\to N^\star\to N\pi$$ transitions.
Authors:
 [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion Univ., Norfolk, VA (United States)
Publication Date:
Report Number(s):
JLAB-THY-15-2153; DOE/OR/23177-3851; arXiv:1604.03782
Journal ID: ISSN 0177-7963; PII: 1124
Grant/Contract Number:
AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
Few-Body Systems
Additional Journal Information:
Journal Volume: 57; Journal Issue: 10; Conference: "Nucleon Resonances: from Photoproduction to High Photon Virtualities", ECT, Trento (Italy), 12-16 Oct 2015; Journal ID: ISSN 0177-7963
Publisher:
Springer
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
OSTI Identifier:
1330673