World average values for the branching fractions of Λc+ baryon decays
(updated 10 October 2016)

People working on this:   Xiao-Rui Lyu Anze Zupanc


Charmed baryon decays play an important role in studies of weak and strong interactions and provide a crucial input in studies of exclusive and inclusive decay rate measurements of b-flavored mesons and baryons or the measurements of fragmentation fractions of charm and bottom quarks. Albeit their importance, the experimental input on branching fractions of Λc+ baryons was scarce until 2014 when Belle published the first ever model-independent measurement of branching fractions of Λc+→pK-π+ decays that improved the precision of previous model-dependent determinations by a factor of 5. The precisions of branching fractions of multiple hadronic Cabibbo-favored Λc+ baryon decays have further been improved with the first direct measurement based on threshold data performed by BESIII. In addition, BESIII reported the first absolute measurement of branching fractions of the most favorable semi-leptonic mode Λc+→Λe+νe.

Here, we present a global fit to branching fractions of the Cabbibo-favored Λc+ decays taking into account many different experimental measurements.

The measurements listed in Table below have been used in a least χ2 fit. The fitted quantities, branching fractions of twelve hadronic and one semileptonic Λc+ decay, and the input measurements are labelled using the PDG Γn notation, where n is an integer number that matches the notation from the PDG 2014 edition. Therefore, the fit output consists of 13 quantities - twelve hadronic and one semileptonic Λc+ decay branching fraction. We have taken into account the correlations for the measurements from the same experiment for the systematic uncertainties related to: normalization, track finding efficiency, particle identification efficiency, π0, KS0, and Λ reconstruction efficiencies. In the case of the simultaneous determination of twelve hadronic Λc+ absolute branching fractions by BESIII, we use the published correlation matrix. The world average values for twelve hadronic and one semileptonic Λc+ decay rates are given in Table below. The overall χ2 value of the global fit is 30.0 for 23 degrees of freedom, which corresponds to a p value of 0.149. Correlation matrix between the fitted branching fractions is shown in figure below.

The branching fraction of the normalisation decay, Λc+→pK-π+, is found to be

Br(Λc+→pK-π+)WA = (6.46 ± 0.24) × 10-2.

Experimental results and world averages for branching fractions of twelve hadronic and one semileptonic Λc+ decay. The first uncertainty is statistical and the second is systematic.


Correlation coefficients between averaged Λc+ branching fractions (Click on figure for higher resolution.)

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