English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

An excess in the branching fraction for $B^+ \to K^+ \nu\nu$ recentlymeasured at Belle II may be a hint of new physics. We perform thoroughlikelihood analyses for different new physics scenarios such as $B \to KX$ witha new invisible particle $X$, or $B\to K\chi\chi$ through a scalar, vector, ortensor current with $\chi$ being a new invisible particle or a neutrino. Wefind that vector-current 3-body decay with $m_X \simeq 0.6$ GeV - which may bedark matter - is most favored, while 2-body decay with $m_X \simeq 2$ GeV isalso competitive. The best-fit branching fractions for the scalar and tensorcases are a few times larger than for the 2-body and vector cases. Past BaBarmeasurements provide further discrimination, although the best-fit parametersstay similar.

Decoding the $B \to K \nu \nu$ excess at Belle II: kinematics, operators, and masses