gamma*gamma* -> eta(c) transition form factor

Author(s)

Wolfgang Lucha, Dimitri Melikhov

Abstract

We study the gamma*gamma* -> eta(c) transition form factor, F-eta c gamma gamma (Q(1)(2), Q(2)(2) )with the local-duality (LD) version of QCD sum rules. We analyze the extraction of this quantity from two different correlators, <PVV > and <AVV >, with P, A, and V being the pseudoscalar, axial-vector, and vector currents, respectively. The QCD factorization theorem for F-eta c gamma gamma (Q(1)(2), Q(2)(2)) allows us to fix the effective continuum thresholds for the <PVV > and <AVV > correlators at large values of Q(2) = Q(2)(2) and some fixed value of beta = Q(1)(2) / Q(2)(2). We give arguments that, in the region Q(2) >= 10-15 GeV2, the effective threshold should be close to its asymptotic value such that the LD sum rule provides reliable predictions for F-eta c gamma gamma (Q(1)(2), Q(2)(2) ) . We show that, for the experimentally relevant kinematics of one real and one virtual photon, the result of the LD sum rule for F-eta c gamma(Q(2)) equivalent to F-eta c gamma gamma (0, Q(2)) may be well approximated by the simple monopole formula F-eta c gamma(Q(2)) equivalent to 2e(c)(2)N(c)f(P)(M-V(2) + Q(2))(-1), where f(P) is the eta(c) decay constant, e(c)(2) is the c-quark charge, and the parameter M-V lies in the mass range of the lowest (c) over barc vector states.

Organisation(s)

Particle Physics

External organisation(s)

Österreichische Akademie der Wissenschaften (ÖAW), Universität Wien, Anuchin Research Institute and Museum of Anthropology

Journal

Physical Review D

Volume

86

No. of pages

8

ISSN

1550-7998

DOI

https://doi.org/10.1103/PhysRevD.86.016001

Publication date

2012

Peer reviewed

Yes

Austrian Fields of Science 2012

103036 Theoretical physics, 103034 Particle physics

Portal url

https://ucris.univie.ac.at/portal/en/publications/gammagamma--etac-transition-form-factor(6e92f035-cf31-4ed7-a4a4-7a4349860030).html