Two is better than one: The U-spin-CP anomaly in charm Article Swipe

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Rigo Bause , Hector Gisbert , Gudrun Hiller , Tim Höhne , Daniel F. Litim , Tom Steudtner · YOU? · · 2022 · Open Access · · DOI: https://doi.org/10.48550/arxiv.2210.16330

The recent measurement of the CP-asymmetry in the decay $D \to K^+ K^-$ by LHCb, combined with $ΔA_{\text{CP}}$, evidences a sizable CP-asymmetry in $D \to π^+ π^-$ decays, which requires a dynamical enhancement of standard model higher-order contributions over tree-level ones by a factor of two. The data furthermore imply huge U-spin breaking, about 4-5 times larger than the nominal standard model one of $\lesssim 30 \%$ in charm. Enhanced breakdown of the two approximate symmetries points to models that violate U-spin and CP and disfavors flavor singlet contributions such as chromomagnetic dipole operators as explanations of the data. We analyze the reach of flavorful $Z^\prime$ models for charm CP-asymmetries. Models feature explicit U-spin and isospin breaking, allowing for correlations with $D \to π^0 π^0$ and $D^+ \to π^+ π^0$ decays with corresponding CP-asymmetries at a similar level and sign as $D \to π^+ π^-$, about $ {\cal{O}}(1-2) \cdot 10^{-3}$. Experimental and theoretical constraints narrow down the shape of viable models: anomaly-free models are leptophobic -- or at least electro- and muo-phobic -- with light $Z^\prime$ below ${\cal{O}}(20)$ GeV, and can be searched for in low mass dijets at the LHC, $Υ$ and charmonium decays, and dark photon signatures. A $Z^\prime$ around $\sim 3$ GeV or $\sim (5-7)$ GeV can relieve the tensions in the $J/ψ\to π^+ π^-$ and $ψ^\prime \to π^+ π^-$ branching ratios with pion form factors from fits to Babar and JLab data, and simultaneously explain the charm CP asymmetries. Models also feature sizable branching ratios into light right-handed neutrinos or vector-like dark fermions, which can be searched for in $e^+ e^- \to$~hadrons + invisibles at Belle II and BESIII. Due to the low new physics scale dark fermions may induce an early Landau pole which requires UV-completion near the TeV-scale.

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preprint

Language

en

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http://arxiv.org/abs/2210.16330

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https://arxiv.org/pdf/2210.16330

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green

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10

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https://openalex.org/W4307925645

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https://openalex.org/W4307925645

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DOI

https://doi.org/10.48550/arxiv.2210.16330

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Title

Two is better than one: The U-spin-CP anomaly in charm

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preprint

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en

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2022

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2022-10-28

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Rigo Bause, Hector Gisbert, Gudrun Hiller, Tim Höhne, Daniel F. Litim, Tom Steudtner

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https://arxiv.org/abs/2210.16330

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https://arxiv.org/pdf/2210.16330

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green

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https://arxiv.org/pdf/2210.16330

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Concepts

Physics, Particle physics, Asymmetry, Anomaly (physics), Charm (quantum number), Physics beyond the Standard Model, Isospin, CP violation, Nuclear physics, Pion, Charm quark, Standard Model (mathematical formulation), Hadron, Quantum mechanics, Archaeology, Gauge (firearms), History

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Cited by

1

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2025: 1

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10

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