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