{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"055300917de144d5478648577764adca87f9648caf4a0ff6d32f8753a1f84fbf","created":"2026-10-03T07:18:05Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"5353b3c2675c2e0e0193e4812cb524400a7e53e07e8715ec94428f9090d3756a","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"hep.flavor-anomalies.b-k-nunu","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Belle II found that B mesons decay to a kaon plus invisible particles more often than expected, about four times the predicted rate. It could be new particles or a fluctuation.","posed_since":"2023","precise":"Belle II (2023) measured BR(B+ -> K+ nu nubar) = (2.3 +- 0.7) x 1e-5, $2.7\\,\\sigma$ above the SM prediction ($\\sim 0.5 x 1e-5$). Determine whether the excess persists at $\\ge 5\\,\\sigma$ and whether it shows a peak in invisible mass from a new light particle.","problem_ref":null,"references":"","settled_by":"Belle II with about 5 to 10 $\\mathrm{ab}^{-1}$ and NA62-style rare kaon decays for related b to s and s to d invisible channels.","status_note":"The $2.7\\sigma$ excess is still the latest measurement as of 2026.","title":"Is the Belle II $B\\,\\mathrm{to}\\,K\\,\\nu\\,\\nu$ excess real?","topic_ref":"67e36a860662b77a3c30ab454eb65cfa879e6c2949ab905ac9b1ccef959fe797"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"39a558bd6ce48b8496559b26e619658f7c31e51e5cea86820886b0ce62d747a6","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"bbc3b173f957215d25409cab6259864a10da9c4a4a42e9ec76dc3181525c96f2","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"FT-m8P9l5m0MIoTywxqO8jQgkaZJRdxoY2--Afb5uCRtOI0V5intvsZ7JDaY8VVXNTtecgHq6oTfl6UqZBUgBA"},"schema":"pubphys.envelope/1"},"record_hash":"39a558bd6ce48b8496559b26e619658f7c31e51e5cea86820886b0ce62d747a6","leaf_index":1537}