Spacelike pion form factor from analytic continuation and the onset of perturbative QCD

Ananthanarayan, B and Caprini, Irinel and Imsong, Sentitemsu I (2012) Spacelike pion form factor from analytic continuation and the onset of perturbative QCD. In: PHYSICAL REVIEW D, 85 (9).

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Abstract

The factorization theorem for exclusive processes in perturbative QCD predicts the behavior of the pion electromagnetic form factor F(t) at asymptotic spacelike momenta t(= -Q(2)) < 0. We address the question of the onset energy using a suitable mathematical framework of analytic continuation, which uses as input the phase of the form factor below the first inelastic threshold, known with great precision through the Fermi-Watson theorem from pi pi elastic scattering, and the modulus measured from threshold up to 3 GeV by the BABAR Collaboration. The method leads to almost model-independent upper and lower bounds on the spacelike form factor. Further inclusion of the value of the charge radius and the experimental value at -2.45 GeV2 measured at JLab considerably increases the strength of the bounds in the region Q(2) less than or similar to 10 GeV2, excluding the onset of the asymptotic perturbative QCD regime for Q(2) < 7 GeV2. We also compare the bounds with available experimental data and with several theoretical models proposed for the low and intermediate spacelike region.

Item Type:	Journal Article
Publication:	PHYSICAL REVIEW D
Publisher:	AMER PHYSICAL SOC
Additional Information:	Copyright for this article belongs to the American Physical Society
Department/Centre:	Division of Physical & Mathematical Sciences > Centre for High Energy Physics
Date Deposited:	27 Jun 2012 10:28
Last Modified:	27 Jun 2012 10:28
URI:	http://eprints.iisc.ac.in/id/eprint/44740

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