Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Searches for CP violation in two-body charm decays   The LHCb experiment recorded data corresponding to an integrated luminosity
of 3.0 $fb^{-1}$ during its first run of data taking. These data yield the
largest samples of charmed hadrons in the world and are used to search for CP
violation in the $D^0$ system. Among the many measurements performed at LHCb, a
measurement of the direct CP asymmetry in $D^0 \rightarrow K_S^0 K_S^0$ decays
is presented and is found to be
  $A_{CP}(D^0 \rightarrow K_S^0 K_S^0) = (-2.9 \pm 5.2 \pm 2.2)\, \%, $ where
the first uncertainty is statistical and the second systematic. This represents
a significant improvement in precision over the previous measurement of this
parameter. Measurements of the parameter $A^\Gamma$, defined as the CP
asymmetry of the $D^0$ effective lifetime when decaying to a CP eigenstate, are
also presented. Using semi-leptonic b-hadron decays to tag the flavour of the
$D^0$ meson at production with the $K^+K^-$ and $\pi^+\pi^-$ final states
yields $A^\Gamma(K^+K^-) = (-0.134 \pm 0.077^{+0.026}_{-0.034})\, \%,$
$A^\Gamma(\pi^+\pi^-) = (-0.092 \pm 0.145^{+0.025}_{-0.033})\, \%. $
  Thus no evidence of direct or indirect CP violation in the $D^0$ system is
found, though it is tightly constrained.

19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin