Search for B+→K+νν¯ Decays U

A tale of invisibility: constraints on new physics in b → sνν

“…Recently, the Belle II collaboration presented a new analysis with a new upper bound Br(B + → K + νν) < 4.1×10 −5 [4,8]. A simple weighted average of the result with previous analyses [5][6][7] [4,8] which suggests an enhancement over the SM expectation. We discuss its implications in terms of new physics in section 4.4.…”

“…Indeed, due to the large suppression of b → s transitions as predicted by the SM, currently only experimental upper bounds on the decay channels B → K ( * ) νν and B → X s νν exist. Most recently, the Belle-II collaboration presented a new analysis for B + → K + νν [4] and reported an upper bound Br(B + → K + νν) < 4.1 × 10 −5 at the 90% confidence level. A simple weighted average of their result with earlier results [5][6][7] leads to Br(B + → K + νν) = (1.1 ± 0.4) × 10 −5 [4,8].…”

“…Most recently, the Belle-II collaboration presented a new analysis for B + → K + νν [4] and reported an upper bound Br(B + → K + νν) < 4.1 × 10 −5 at the 90% confidence level. A simple weighted average of their result with earlier results [5][6][7] leads to Br(B + → K + νν) = (1.1 ± 0.4) × 10 −5 [4,8]. If substantiated further, this would imply an enhancement on top of the SM expectation Br(B + → K + νν) = (4.4 ± 0.7) × 10 −6 [9], which has been interpreted in terms of leptoquarks and Z bosons [10,11].…”

“…where q 2 denotes the square of the 4-momentum of the neutrino pair. The relevant Wigner-D functions are D 0 0,0 (Ω K ) = 1 and D 2 0,0 (Ω K ) = 1 2 3 cos 2 θ K − 1 4 and their coefficients Ḡ are given in appendix D. The CP conjugate process B → K * ν α ν β is obtained by replacing the Ḡ functions with the corresponding G functions G 0,0 0 and G 2,0 0 for which all Wilson coefficients are replaced by their complex conjugates.…”

“…simple weighted average [4,8] Br(B + → K + νν) = (1.1 ± 0.4) × 10 −5 and discuss how it could be explained in terms of a sterile neutrino.…”