A $U$-Spin Anomaly in Charm CP Violation

Schacht, Stefan

doi:10.48550/arxiv.2207.08539

Cited by 3 publications

(4 citation statements)

References 44 publications

(68 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1. The small value of A CP (K + K − ), combined with ∆A CP (green), implies a sizable CP-asymmetry in π + π − , together with substantial U -spin breaking, which has also been pointed out in [4]. Predictions in the U-spin limit (red dashed line) and 30% SM-like breaking (red cones) are indicated.…”

Section: Introductionmentioning

confidence: 65%

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

Bause¹,

Gisbert²,

Hiller³

et al. 2022

Preprint

View full text Add to dashboard Cite

The recent measurement of the CP-asymmetry in the decay D → K + K − by LHCb, combined with ∆ACP, evidences a sizable CP-asymmetry in the decay D → π + π − , 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 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 models for charm CP-asymmetries. Models generically feature explicit U-spin and isospin breaking, allowing for correlations with D → π 0 π 0 and D + → π + π 0 decays with corresponding CP-asymmetries at similar level and sign as D → π + π − , about O(1−2) • 10 −3 . Experimental and theoretical constraints very much narrow down the shape of viable models: Viable, anomaly-free models are leptophobic, -or at least electron-and muon-phobic -with light Z below O(20) GeV, and can be searched for in low mass dijets at the LHC or in Υ and charmonium decays, as well as dark photon searches. Models can also feature sizable branching ratios into light right-handed neutrinos or vector-like dark fermions, which can be searched for in e + e − → hadrons + invisibles at Belle II and BESIII. Due to the low new physics scale dark fermions can easily induce an early Landau pole, requiring models to be UV-completed near the TeV-scale.

show abstract

Section: Introductionmentioning

confidence: 65%

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

Bause¹,

Gisbert²,

Hiller³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…C P asymmetry in the individual mode is more significant compared to the difference between two decay modes because it allows us to extract more knowledge of nonperturbative QCD. The newest data indicates a very large U -spin breaking in the D 0 → K + K − and D 0 → π + π − modes, which is beyond the naive expectations of ε ∼ m s / QCD ∼ 30% [23].…”

Section: Introductionmentioning

confidence: 73%

“…Compared to Ref. [23], the K * K * → ππ scattering is included in the final state interaction. Since the weak vertex of triangle diagram is a shortdistance T diagram, the factorization approach is used to estimate the weak decay amplitude.…”

Section: Estimation In the Final-state Interactionmentioning

confidence: 99%

Evidence of $$A_{CP}(D^0\rightarrow \pi ^+\pi ^-)$$ implies observable CP asymmetry in the $$D^0\rightarrow \pi ^0\pi ^0$$ decay

Wang

2023

Eur. Phys. J. C

View full text Add to dashboard Cite

Inspired by the recent measurement of CP asymmetry in the individual mode on LHCb, we study CP asymmetry of the $$D\rightarrow \pi \pi $$ D → π π system in the isospin and topological analysis. The ratio between penguin and tree amplitudes $$P/(T+C)$$ P / ( T + C ) in the $$D\rightarrow \pi \pi $$ D → π π system is found to be greater than two in most values of the relative strong phase. And $$D^0\rightarrow \pi ^0\pi ^0$$ D 0 → π 0 π 0 is a potential mode to reveal the CP asymmetry of the order of $$10^{-3}$$ 10 - 3 , which would be observed by Belle II in the future. The large CP asymmetry in the $$D\rightarrow \pi \pi $$ D → π π system might be understood in the t-channel final-state interaction.

show abstract

“…CP asymmetry in the individual decay mode is more significant compared to the difference between two decay modes because it allows us to extract more knowledge of non-perturbative QCD. Recent theoretical work showed the newest data indicates a very large U -spin breaking in the D 0 → K + K − and D 0 → π + π − modes, which is beyond the naive expectations of ε ∼ m s /Λ QCD ∼ 30% [20].…”

Section: Introductionmentioning

confidence: 81%

Evidence of $A_{CP}(D^0\to π^+π^-)$ implies observable $CP$ violation in the $D^0\to π^0π^0$ decay

Wang¹

2022

Preprint

View full text Add to dashboard Cite

Inspired by the discovery of CP violation in the D 0 → π + π − decay on LHCb, we study CP asymmetries in the D → ππ system in the isospin and topological analysis. The formulas of direct CP asymmetries in the D 0 → π + π − and D 0 → π 0 π 0 decays are derived. We find the ratio between penguin and tree amplitudes P/(T + C) in the D → ππ system is greater than 2 in most values of the strong phase. And D 0 → π 0 π 0 decay is a potential mode to reveal the CP violation of the order of 10 −3 and would be observed by Belle II in the foresee future.

show abstract

A $U$-Spin Anomaly in Charm CP Violation

Cited by 3 publications

References 44 publications

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

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

Evidence of $$A_{CP}(D^0\rightarrow \pi ^+\pi ^-)$$ implies observable CP asymmetry in the $$D^0\rightarrow \pi ^0\pi ^0$$ decay

Evidence of $A_{CP}(D^0\to π^+π^-)$ implies observable $CP$ violation in the $D^0\to π^0π^0$ decay

Contact Info

Product

Resources

About