An investigation of the very rare K → π νν¯ decay Article uri icon

abstract

  • The NA62 experiment reports an investigation of the K → π νν¯ mode from a sample of K decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10−10 for the K → π νν¯ branching ratio at 90%25 CL. This, together with the corresponding 68%25 CL measurement of (0.48−0.48 0.72) × 10−10, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements. © 2020, The Author(s).
  • The NA62 experiment reports an investigation of the K%2b→ π%2bνν¯ mode from a sample of K%2b decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10−10 for the K%2b→ π%2bνν¯ branching ratio at 90%25 CL. This, together with the corresponding 68%25 CL measurement of (0.48−0.48%2b0.72) × 10−10, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements. © 2020, The Author(s).

authors

publication date

  • 2020-01-01