Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2603.13139v1</id>\n    <title>CP Violation in $B_{(s)}\\toφK$ Decays: Standard Model Benchmarks and Isospin-Breaking New Physics</title>\n    <updated>2026-03-13T16:29:06Z</updated>\n    <link href='https://arxiv.org/abs/2603.13139v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2603.13139v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>The penguin loop-suppressed $B\\toφK$ decays are highly sensitive to contributions of hypothetical heavy new particles. Particularly interesting probes for testing the Standard Model and revealing such phenomena are provided by CP violation in the $B^0_d\\toφK_{\\rm S}$ decay. Standard-Model estimates for the corresponding CP-violating observables are theoretically limited by doubly Cabibbo-suppressed penguin contributions. We study these effects using a factorization approach, and provide predictions for CP asymmetries, to be contrasted with future measurements. To gain additional insight into these hadronic effects, we propose the $B_s^0\\toφK_{\\rm S}$ decay as a new channel. We predict the observables for this decay for which currently no measurements exist. By comparing $B^0_d\\toφK_{\\rm S}$ and $B^+ \\to φK^+$, we further derive state-of-the-art constraints on isospin observables within the Standard Model. The same framework enables probing of possible New-Physics contributions, including general effects and those with non-trivial isospin structure. Interesting prospects arise for the high-precision era of flavour physics ahead.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='hep-ph'/>\n    <published>2026-03-13T16:29:06Z</published>\n    <arxiv:comment>28 pages, 9 figures</arxiv:comment>\n    <arxiv:primary_category term='hep-ph'/>\n    <author>\n      <name>Robert Fleischer</name>\n    </author>\n    <author>\n      <name>Jelle Groot</name>\n    </author>\n    <author>\n      <name>K. Keri Vos</name>\n    </author>\n  </entry>"
}