pdgLive Home   >   Meson Summary Table   >   ${{\mathit \chi}_{{{c1}}}{(1P)}}$   >   $\mathit b_{2}$ = $\mathit M2/\sqrt {\mathit E1{}^{2}+\mathit M2{}^{2} }$ Magnetic quadrupole fractional transition amplitude

MULTIPOLE AMPLITUDES IN ${{\mathit \psi}{(2S)}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \chi}_{{{c1}}}{(1S)}}$ RADIATIVE DECAY

$\mathit b_{2}$ = $\mathit M2/\sqrt {\mathit E1{}^{2}+\mathit M2{}^{2} }$ Magnetic quadrupole fractional transition amplitude

INSPIRE   JSON  (beta) PDGID:

M055QB2

VALUE ($ 10^{-2} $) EVTS DOCUMENT ID TECN  COMMENT $\bf{ 2.5 \pm0.4}$ OUR AVERAGE $2.29$ $\pm0.39$ $\pm0.27$ 164k 1 ABLIKIM 2017 N BES3 ${{\mathit \psi}{(2S)}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$ $2.76$ $\pm0.73$ $\pm0.23$ 39k ARTUSO 2009 CLEO ${{\mathit \psi}{(2S)}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$ $7.7$ ${}^{+5.0}_{-4.5}$ 921 OREGLIA 1982 CBAL ${{\mathit \psi}{(2S)}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$ 1  Correlated with ${{\mathit a}_{{{2}}}}$ with correlation coefficient $\rho _{{{\mathit a}_{{{2}}}} {{\mathit b}_{{{2}}}}}$ = 0.133.

References

Except where otherwise noted, content of the 2025 Review of Particle Physics is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license. The publication of the Review of Particle Physics is supported by US DOE, MEXT (Japan), INFN (Italy) and CERN. Individual collaborators receive support for their PDG activities from their respective institutes or funding agencies. © 2025. See LBNL disclaimers.