A sample of $pp$ collision data, corresponding to an integrated luminosity of 5.4 fb$^{ -1}$ and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the ${ \it{ \Xi}}_b^0$ baryon to that of the ${ \it{ \Lambda}}_b^0$ baryon, $r_{ \tau}\equiv\tau_{ { \it{ \Xi}}_b^0}/\tau_{ { \it{ \Lambda}}_b^0}$. The value ${ r_{ \tau}^{ \rm Run\,2}=1.004\pm0.009\pm0.006}$ is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain ${ r_{ \tau} = 1.004\pm0.008\pm0.005}$. Multiplying by the known value of the ${ \it{ \Lambda}}_b^0$ lifetime yields ${ { \tau_{ { \it{ \Xi}}_b^0}} = 1.475\pm0.012\pm0.008\pm0.009~{ \rm ps}}$, where the last uncertainty is due to the limited knowledge of the ${ \it{ \Lambda}}_b^0$ lifetime. This measurement improves the precision of the current world average of the ${ \it{ \Xi}}_b^0$ lifetime by about a factor of two, and is in good agreement with the most recent theoretical predictions.
Categories: hep-ex