Item

Abstract

A search is performed in the invariant mass spectrum of the
$B_c^{+}\pi^{+}\pi^{-}$ system for the excited $B_c^{+}$ states
$B_c(2^{1}S_{0})^+$ and $B_c(2^{3}S_{1})^+$ using a data sample of $pp$
collisions collected by the LHCb experiment at the centre-of-mass energy of
$\sqrt{s} = 8 \,{\mathrm{TeV}}$, corresponding to an integrated luminosity of
$2 \,{\mathrm{fb^{-1}}}$. No evidence is seen for either state. Upper limits on
the ratios of the production cross-sections of the $B_c(2^{1}S_{0})^+$ and
$B_c(2^{3}S_{1})^+$ states times the branching fractions of
${B_c(2^{1}S_{0})^+} \to {B_c^{+}\pi^{+}\pi^{-}}$ and ${B_c(2^{3}S_{1})^+} \to
{B_c^{*+}\pi^{+}\pi^{-}}$ over the production cross-section of the $B_c^{+}$
state are given as a function of their masses. They are found to be between
0.02 and 0.14 at $95\%$ confidence level for $B_c(2^{1}S_{0})^+$ and
$B_c(2^{3}S_{1})^+$ in the mass ranges $[6830, 6890] \,{\mathrm{MeV}}/c^{2}$
and $[6795,6890] \,{\mathrm{MeV}}/c^{2}$, respectively.