Infoscience

Journal article

Measurement of gamma gamma* -> pi(0) transition form factor at Belle

Uehara, S.; Watanabe, Y.; Nakazawa, H.; Adachi, I.; Aihara, H.; Asner, D. M.; Aushev, T.; Bakich, A. M.; Belous, K.; Bhardwaj, V.

Belle Collaboration

We report a measurement of the process gamma gamma* -> pi(0) with a 759 fb(-1) data sample recorded with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The pion transition form factor, F(Q(2)), is measured for the kinematical region 4 GeV2 <= Q(2) <= 40 GeV2, where -Q(2) is the invariant-mass squared of a virtual photon. The measured values of Q(2)vertical bar F(Q(2))vertical bar agree well with the previous measurements below Q(2) similar or equal to 9 GeV2 but do not exhibit the rapid growth in the higher Q(2) region seen in another recent measurement, which exceeds the asymptotic QCD expectation by as much as 50%.

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