Charming penguins and lepton universality violation in $$\varvec{b \rightarrow s \ell ^+ \ell ^-}$$ b s + - decays

Marco Ciuchini (INFN Sezione di Roma Tre, Via della Vasca Navale 84, Rome, 00146, Italy) ; Marco Fedele (Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology, Karlsruhe, 76131, Germany) ; Enrico Franco (INFN Sezione di Roma, Piazzale Aldo Moro 2, Rome, 00185, Italy) ; Ayan Paul (Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, Hamburg, 22607, Germany; Institut für Physik, Humboldt-Universität zu Berlin, Berlin, 12489, Germany) ; Luca Silvestrini (INFN Sezione di Roma, Piazzale Aldo Moro 2, Rome, 00185, Italy) ; et al. - Show all 6 authors

The LHCb experiment has recently presented new results on Lepton Universality Violation (LUV) in $$B \rightarrow K^{(*)} \ell ^+ \ell ^-$$ B K ( ) + - decays involving $$K_S$$ K S in the final state, which strengthen the recent evidence of LUV obtained in $$B^+ \rightarrow K^{+} \ell ^+ \ell ^-$$ B + K + + - decays and the previous measurements of $$B \rightarrow K^{*0} \ell ^+ \ell ^-$$ B K 0 + - . While LUV observables in the Standard Model are theoretically clean, their predictions in New Physics scenarios are sensitive to the details of the hadronic dynamics, and in particular of the charming penguin contribution. In this work, we show how a conservative treatment of hadronic uncertainties is crucial not only to assess the significance of deviations from the Standard Model but also to obtain a conservative picture of the New Physics responsible for LUV. Adopting a very general parameterization of charming penguins, we find that: (i) current data hint at a sizable $$q^2$$ q 2 and helicity dependence of charm loop amplitudes; (ii) conservative NP solutions to B anomalies favour a left-handed or an axial lepton coupling rather than a vector one.

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      "title": "Charming penguins and lepton universality violation in  $$\\varvec{b \\rightarrow s \\ell ^+ \\ell ^-}$$  <math> <mrow> <mi>b</mi> <mo>\u2192</mo> <mi>s</mi> <msup> <mi>\u2113</mi> <mo>+</mo> </msup> <msup> <mi>\u2113</mi> <mo>-</mo> </msup> </mrow> </math>   decays"
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      "value": "The LHCb experiment has recently presented new results on Lepton Universality Violation (LUV) in  $$B \\rightarrow K^{(*)} \\ell ^+ \\ell ^-$$  <math> <mrow> <mi>B</mi> <mo>\u2192</mo> <msup> <mi>K</mi> <mrow> <mo>(</mo> <mrow></mrow> <mo>\u2217</mo> <mo>)</mo> </mrow> </msup> <msup> <mi>\u2113</mi> <mo>+</mo> </msup> <msup> <mi>\u2113</mi> <mo>-</mo> </msup> </mrow> </math>   decays involving  $$K_S$$  <math> <msub> <mi>K</mi> <mi>S</mi> </msub> </math>   in the final state, which strengthen the recent evidence of LUV obtained in  $$B^+ \\rightarrow K^{+} \\ell ^+ \\ell ^-$$  <math> <mrow> <msup> <mi>B</mi> <mo>+</mo> </msup> <mo>\u2192</mo> <msup> <mi>K</mi> <mo>+</mo> </msup> <msup> <mi>\u2113</mi> <mo>+</mo> </msup> <msup> <mi>\u2113</mi> <mo>-</mo> </msup> </mrow> </math>   decays and the previous measurements of  $$B \\rightarrow K^{*0} \\ell ^+ \\ell ^-$$  <math> <mrow> <mi>B</mi> <mo>\u2192</mo> <msup> <mi>K</mi> <mrow> <mrow></mrow> <mo>\u2217</mo> <mn>0</mn> </mrow> </msup> <msup> <mi>\u2113</mi> <mo>+</mo> </msup> <msup> <mi>\u2113</mi> <mo>-</mo> </msup> </mrow> </math>  . While LUV observables in the Standard Model are theoretically clean, their predictions in New Physics scenarios are sensitive to the details of the hadronic dynamics, and in particular of the charming penguin contribution. In this work, we show how a conservative treatment of hadronic uncertainties is crucial not only to assess the significance of deviations from the Standard Model but also to obtain a conservative picture of the New Physics responsible for LUV. Adopting a very general parameterization of charming penguins, we find that: (i) current data hint at a sizable  $$q^2$$  <math> <msup> <mi>q</mi> <mn>2</mn> </msup> </math>   and helicity dependence of charm loop amplitudes; (ii) conservative NP solutions to B anomalies favour a left-handed or an axial lepton coupling rather than a vector one."
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Published on:
24 January 2023
Publisher:
Springer
Published in:
European Physical Journal C , Volume 83 (2023)
Issue 1
Pages 1-15
DOI:
https://doi.org/10.1140/epjc/s10052-023-11191-w
Copyrights:
The Author(s)
Licence:
CC-BY-4.0

Fulltext files: