Sub-picosecond C = C bond photo-isomerization: evidence for the role of excited state mixing

We search for excited charmed baryons in the

Λ_{c}^{+} η

system using a data sample corresponding to an integrated luminosity of

980 {fb}^{- 1}

. The data were collected by the Belle detector at the KEKB

e^{+} e^{-}

asymmetric-energy collider. No significant signals are found in the

Λ_{c}^{+} η

mass spectrum, including the known

Λ_{c} (2880)^{+}

and

Λ_{c} (2940)^{+}

. Clear

Λ_{c} (2880)^{+}

and

Λ_{c} (2940)^{+}

signals are observed in the

p D^{0}

mass spectrum. We set upper limits at 90% credibility level on ratios of branching fractions of

Λ_{c} (2880)^{+}

and

Λ_{c} (2940)^{+}

decaying to

Λ_{c}^{+} η

relative to

Σ_{c} (2455) π

of

< 0.13

for the

Λ_{c} (2880)^{+}

and

< 1.11

for the

Λ_{c} (2940)^{+}

. We measure ratios of branching fractions of

Λ_{c} (2880)^{+}

and

Λ_{c} (2940)^{+}

decaying to

p D^{0}

relative to

Σ_{c} (2455) π

of

0.75 \pm 0.03 (stat) \pm 0.07 (syst)

for the

Λ_{c} (2880)^{+}

and

3.59 \pm 0.21 (stat) \pm 0.56 (syst)

for the

Λ_{c} (2940)^{+}

. Published by the American Physical Society2024