Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $\eta_c$ production at LHC and indications on the understanding of
  $J/\psi$ production   We present a complete evaluation for the prompt $\eta_c$ production at the
LHC at next-to-leading order in $\alpha_s$ in nonrelativistic QCD. By assuming
heavy quark spin symmetry, the recently observed $\eta_c$ production data by
LHCb results in a very strong constraint on the upper bound of the color-octet
long distance matrix element $1S0$ of $J/\psi$. We find this upper bound is
consistent with our previous study of the $J/\psi$ yield and polarization and
can give good descriptions for the measurements, but inconsistent with some
other theoretical estimates. This may provide important information for
understanding the nonrelativistic QCD factorization formulism.

31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga