Study of psi(2S) decays to X J/psi

TL;DR

This study measures the branching fractions of psi(2S) decays to J/psi with various intermediate states using a large data sample, providing precise ratios normalized to the psi(2S) -> pi+ pi- J/psi decay.

Contribution

It provides the first precise measurements of branching fraction ratios for psi(2S) decays to J/psi involving eta and pi^0 pi^0, normalized to the pi+ pi- mode.

Findings

Measured B(psi(2S) -> eta J/psi)/B(psi(2S) -> pi+ pi- J/psi) = 0.098 ± 0.005 ± 0.010

Measured B(psi(2S) -> pi^0 pi^0 J/psi)/B(psi(2S) -> pi+ pi- J/psi) = 0.570 ± 0.009 ± 0.026

Total B(psi(2S) -> anything J/psi)/B(psi(2S) -> pi+ pi- J/psi) = 1.867 ± 0.026 ± 0.055

Abstract

Using J/psi -> mu^+ mu^- decays from a sample of approximately 4 million psi(2S) events collected with the BESI detector, the branching fractions of psi(2S) -> eta J/psi, pi^0 pi^0 J/psi, and anything J/psi normalized to that of psi(2S) -> pi^+ pi^- J/psi are measured. The results are B(psi(2S) -> eta J/psi)/B(psi(2S) -> pi^+ pi^- J/psi) = 0.098 \pm 0.005 \pm 0.010, B(psi(2S) -> pi^0 pi^0 J/psi)/B(psi(2S) -> pi^+ pi^- J/psi) = 0.570 \pm 0.009 \pm 0.026, and B(psi(2S) -> anything J/psi)/B(psi(2S) -> pi^+ pi^- J/psi) = 1.867 \pm 0.026 \pm 0.055.