Evidence for the Exclusive Decay<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>B</mml:mi><mml:mi>c</mml:mi><mml:mo>±</mml:mo></mml:msubsup><mml:mo>→</mml:mo><mml:mi>J</mml:mi><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi><mml:msup><mml:mi>π</mml:mi><mml:mo>±</mml:mo></mml:msup></mml:math>and Measurement of the Mass of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>B</mml:mi><mml:mi>c</mml:mi><mml:mo>±</mml:mo></mml:msubsup></mml:math>Meson

We report the first evidence for a fully reconstructed decay mode of the ${B}_{c}^{\ifmmode\pm\else\textpm\fi{}}$ meson in the channel ${B}_{c}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, with $J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. The analysis is based on an integrated luminosity of $360\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ in $p\overline{p}$ collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe $14.6\ifmmode\pm\else\textpm\fi{}4.6$ signal events with a background of $7.1\ifmmode\pm\else\textpm\fi{}0.9$ events, and a fit to the $J/\ensuremath{\psi}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ mass spectrum yields a ${B}_{c}^{\ifmmode\pm\else\textpm\fi{}}$ mass of $6285.7\ifmmode\pm\else\textpm\fi{}5.3(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.2(\mathrm{syst})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%.

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