Electromagnetic Charge Radius of the Pion at High Precision

Ananthanarayan, B and Caprini, Irinel and Das, Diganta (2017) Electromagnetic Charge Radius of the Pion at High Precision. In: PHYSICAL REVIEW LETTERS, 119 (13).

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Abstract

We present a determination of the pion charge radius from high precision data on the pion vector form factor from both timelike and spacelike regions, using a novel formalism based on analyticity and unitarity. At low energies, instead of the poorly known modulus of the form factor, we use its phase, known with high accuracy from Roy equations for pi pi elastic scattering via the Fermi-Watson theorem. We use also the values of the modulus at several higher timelike energies, where the data from e(+)e(-) annihilation and tau decay are mutually consistent, as well as the most recent measurements at spacelike momenta. The experimental uncertainties are implemented by Monte Carlo simulations. The results, which do not rely on a specific parametrization, are optimal for the given input information and do not depend on the unknown phase of the form factor above the first inelastic threshold. Our prediction for the charge radius of the pion is r(pi) = (0.657 +/- 0.003) fm, which amounts to an increase in precision by a factor of about 2.7 compared to the Particle Data Group average.

Item Type:	Journal Article
Publication:	PHYSICAL REVIEW LETTERS
Additional Information:	Copy right for this article belongs to the AMER PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Department/Centre:	Division of Physical & Mathematical Sciences > Centre for High Energy Physics
Date Deposited:	21 Oct 2017 06:18
Last Modified:	21 Oct 2017 06:18
URI:	http://eprints.iisc.ac.in/id/eprint/58051

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