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

Autor(en)

Wolfgang Lucha, Dimitri Melikhov

Abstrakt

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(en)

Teilchenphysik

Externe Organisation(en)

Österreichische Akademie der Wissenschaften (ÖAW), Universität Wien, Lomonosov Moscow State University (MSU)

Journal

Physical Review D

Band

86

Anzahl der Seiten

8

ISSN

1550-7998

DOI

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

Publikationsdatum

2012

Peer-reviewed

Ja

ÖFOS 2012

103036 Theoretische Physik, 103034 Teilchenphysik

Link zum Portal

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