${{\mathit \pi}^{0}}$ MEAN LIFE

INSPIRE   JSON  (beta) PDGID:
S009T
Most experiments measure the ${{\mathit \pi}^{0}}$ width which we convert to a lifetime. ATHERTON 1985 is the only direct measurement of the ${{\mathit \pi}^{0}}$ lifetime. The two Primakoff measurements from 1970 have been excluded from our average because they suffered model-related systematics unknown at the time. More information on the ${{\mathit \pi}^{0}}$ lifetime can be found in BERNSTEIN 2013.
VALUE ($ 10^{-17} $ s) EVTS DOCUMENT ID TECN  COMMENT
$\bf{ 8.43 \pm0.13}$ OUR AVERAGE  Error includes scale factor of 1.2.
$8.337$ $\pm0.056$ $\pm0.112$ 1
LARIN
2020
PRMX Primakoff effect
$8.5$ $\pm1.1$ 2
BYCHKOV
2009
PIBE ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit \nu}}{{\mathit \gamma}}$ at rest
$8.4$ $\pm0.5$ $\pm0.5$ 1182 3
WILLIAMS
1988
CBAL ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \pi}^{0}}$
$8.97$ $\pm0.22$ $\pm0.17$
ATHERTON
1985
CNTR Direct measurement
$8.2$ $\pm0.4$ 4
BROWMAN
1974
CNTR Primakoff effect
• • We do not use the following data for averages, fits, limits, etc. • •
$8.32$ $\pm0.15$ $\pm0.18$ 5
LARIN
2011
PRMX Primakoff effect
$5.6$ $\pm0.6$
BELLETTINI
1970
CNTR Primakoff effect
$9$ $\pm0.68$
KRYSHKIN
1970
CNTR Primakoff effect
$7.3$ $\pm1.1$
BELLETTINI
1965B
 CNTR Primakoff effect
1  LARIN 2020 reported this lifetime value from a measurement of $\Gamma ({{\mathit \pi}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$) = $7.802$ $\pm0.052$ $\pm0.105$ eV, combining data from PrimEX-II on 12C and 28Si targets with previous PrimEx-I LARIN 2011 measurements. This result supersedes LARIN 2011.
2  BYCHKOV 2009 obtains this using the conserved-vector-current relation between the vector form factor $\mathit F_{V}$ and the ${{\mathit \pi}^{0}}$ lifetime.
3  WILLIAMS 1988 gives $\Gamma\mathrm {({{\mathit \gamma}} {{\mathit \gamma}})}$ = $7.7$ $\pm0.5$ $\pm0.5$ eV. We give here $\tau $ = $\hbar{}/\Gamma\mathrm {(total)}$.
4  BROWMAN 1974 gives a ${{\mathit \pi}^{0}}$ width $\Gamma $ = $8.02$ $\pm0.42$ eV. The mean life is $\hbar{}/\Gamma $.
5  LARIN 2011 reported $\Gamma ({{\mathit \pi}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$) = $7.82$ $\pm0.14$ $\pm0.17$ eV which we converted to mean life $\tau $ = $\hbar{}/\Gamma $(total).
References