A Tale ofInvisibility: Constraints on New Physics in b → sνν

The Belle IIexperiment will measure the rare decays B → Kνν and B → K∗νν withincreased sensitivity which can hence be expected to serve as a very efficientprobe of new physics. We calculate the relevant branching ratios in LEFTincluding an arbitrary number of massive sterile neutrinos and discuss theexpected sensitivity to the different operators. We also take into account thelongitudinal polarisation fraction FL and the inclusive decayrate B → Xsνν. Together with an investigation of new physics dominantlycontributing to one and two operators, respectively, we discuss the impact ofnon-zero (sterile) neutrino masses and interpret the recently reported excessin B+ → K+νν as anindication of the existence of a massless sterile neutrino. Our results show apowerful interplay of the exclusive decay rates B → Kνν and B → K∗νν, anda surprisingly large sensitivity of the inclusive decay mode to vectoroperators even under conservative assumptions about its uncertainty.Furthermore, the sensitivity of FL is competitive with thebranching ratio of B → K∗νν in the search for new physicscontributing to scalar operators and thus also complementary to B → Kνν and B → Xsνν.

Zoom ID: 97113126809
https://pitt.zoom.us/j/97113126809

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