Abstract
A study of Bc+→χcπ+
B
c
+
→
χ
c
π
+
decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The decay Bc+→χc2π+
B
c
+
→
χ
c
2
π
+
is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the Bc+→J/ψπ+
B
c
+
→
J
/
ψ
π
+
decay is measured to beBBc+→J/ψπ+BBc+→χc2π+=0.37±0.06±0.02±0.01,
B
B
c
+
→
χ
c
2
π
+
B
B
c
+
→
J
/
ψ
π
+
=
0.37
±
0.06
±
0.02
±
0.01
,
where the first uncertainty is statistical, the second is systematic, and the third is due to the knowledge of the χc2→ J/ψγ branching fraction. No significant Bc+→χc1π+
B
c
+
→
χ
c
1
π
+
signal is observed and an upper limit for the relative branching fraction for the Bc+→χc1π+
B
c
+
→
χ
c
1
π
+
and Bc+→χc2π+
B
c
+
→
χ
c
2
π
+
decays of \frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c1}{\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c2}{\pi}^{+}}}=<0.49
B
B
c
+
→
χ
c
1
π
+
B
B
c
+
→
χ
c
2
π
+
=
<
0.49
is set at the 90% confidence level.</jats:p