XIIth Quark Confinement and the Hadron Spectrum

Fragmentation contributions to J/psi photoproduction at HERA

1 Sept 2016, 14:30

20m

Amfitrion II (Makedonia Palace)

Section C: Heavy Quarks Section C

Speaker

Hee Sok Chung (CERN)

Description

We compute leading-power fragmentation corrections to $J/\psi$
photoproduction at DESY HERA, making use of the nonrelativistic QCD
factorization approach. Our calculations include parton production cross
sections through order ${\alpha }_s^3$, fragmentation functions though
order ${\alpha }_s^2$, and leading logarithms of the transverse momentum
divided by the charm-quark mass to all orders in ${\alpha }_s$. We find
that the leading-power fragmentation corrections, beyond those that are
included through next-to-leading order in ${\alpha }_s$, are small relative
to the fixed-order contributions through next-to-leading order in
${\alpha }_s$. Consequently, an important discrepancy remains between the
experimental measurements of the $J/\psi$ photoproduction cross section
and predictions that make use of nonrelativistic-QCD long-distance
matrix elements that are extracted from the $J/\psi$ hadroproduction
cross-section and polarization data.

Presentation materials

Frag_CONF12.pdf