The Rumble in the Meson: a leptoquark versus a $Z^{\prime }$ to fit $b\to s{\mu }^{+}{\mu }^{-}$ anomalies including 2022 LHCb $R_{K^{(\ast )}}$ measurements

Abstract

We juxtapose global fits of two bottom-up models (an $S_3$ scalar leptoquark model and a $B_3-L_2$ $Z^{\prime }$ model) of \bsll\ anomalies to flavour data in order to quantify statistical preference or lack thereof. The leptoquark model couples directly to left-handed di-muon pairs, whereas the $Z^{\prime }$ model couples to di-muon pairs with a vector-like coupling. $B_s-\overline{B_s}$ mixing is a focus because it is typically expected to disfavour $Z^{\prime }$ explanations. In two-parameter fits to 247 flavour observables, including $B_{s/d}\to {\mu }^{+}{\mu }^{-}$ branching ratios for which we provide an updated combination and LHCb $R_{K^{(\ast )}}$ measurements from December 2022, we show that each model provides a similar improvement in quality-of-fit of $\sqrt{\Delta {\chi }^2}=3.6$ with respect to the Standard Model. The main effect of the $B_s-\overline{B_s}$ mixing constraint in the $Z^{\prime }$ model is to disfavour values of the $s_L-b_L$ mixing angle greater than about $5|V_{cb}|$. This limit is rather loose, meaning that a good fit to data does not require `alignment' in either quark Yukawa matrix. No curtailment of the $s_L-b_L$ mixing angle is evident in the $S_3$ model.

31 pages, 6 figures. v3 is updated with a new fit including December 2022 LHCb reanalysis of $R_{K^{(\ast )}}$ measurements. Plots and fits significantly changed but the main conclusion is left unchanged. v4 has minor changes. v5 has a typo fixed in the caption of Fig 6, v6 has corrected vertical lines in Fig 6

References in corpus (27)

• Probing New Physics via the $B_s^0\to {\mu }^{+}{\mu }^{-}$ Effective Lifetime
• $SU(2)\times U(1)$ gauge invariance and the shape of new physics in rare $B$ decays
• Family non-universal Z' models with protected flavor-changing interactions
• On the single leptoquark solutions to the $B$-physics anomalies
• Phenomenology of an $SU(2)\times SU(2)\times U(1)$ model with lepton-flavour non-universality
• Improved Theory Predictions and Global Analysis of Exclusive $\mathbf{b}\to \mathbf{s}{\mathbf{\mu }}^{+}{\mathbf{\mu }}^{-}$ Processes
• Bs mixing observables and Vtd/Vts from sum rules
• Constraints on Lepton Universality Violation from Rare $B$ Decays
• Matching scalar leptoquarks to the SMEFT at one loop
• Low-energy phenomenology of scalar leptoquarks at one-loop accuracy
• $b\to s\ell \ell$ Global Fits after $R_{K_S}$ and $R_{K^{\ast +}}$
• Lessons from the $B^{0,+}\to K^{\ast 0,+}{\mu }^{+}{\mu }^{-}$ angular analyses
• More Indications for Lepton Nonuniversality in $b\to s{\ell }^{+}{\ell }^{-}$
• Drell-Yan Tails Beyond the Standard Model
• A Model of Muon Anomalies
• Neutrino mixing and $R_K$ anomaly in $U(1{)}_X$ models: a bottom-up approach
• Muonic Force Behind Flavor Anomalies
• Standard Model Predictions for Rare K and B Decays without New Physics Infection
• The Exclusive Vision of Rare $K$ and $B$ Decays and of the Quark Mixing in the Standard Model
• On the significance of new physics in $b\to s{\ell }^{+}{\ell }^{-}$ decays
• New Physics in $b\to s\mu \mu$: FCC-hh or a Muon Collider?
• Anomalous $Z^{\prime }$ bosons for anomalous $B$ decays
• Anomalies and accidental symmetries: charging the scalar leptoquark under $L_{\mu }$-$L_{\tau }$
• Global Fits of Third Family Hypercharge Models to Neutral Current B-Anomalies and Electroweak Precision Observables
• Large Hadron Collider Constraints on Some Simple $Z^{\prime }$ Models for $b\to s{\mu }^{+}{\mu }^{-}$ Anomalies
• Electroweak Penguin Decays of $b$-Flavoured Hadrons
• Flatland: abelian extensions of the Standard Model with semi-simple completions

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• A gauged non-universal $U(1{)}_X$ model to study muon $g-2$ and $B$ meson anomalies
• Precision Tests in $b\to s{\ell }^{+}{\ell }^{-}$ ($\ell =e,\mu$) at FCC-ee
• Malaphoric $Z^{\prime }$ models for $b\to s{\ell }^{+}{\ell }^{-}$ anomalies
• Flavour Physics at LHCb -- 50 years of the KM paradigm
• CMS highlights on searches for new physics in final states with jets