CP Asymmetries Research Articles

CP-like symmetry with discrete and continuous groups and CP violation/restoration

We study physical implications of general CP symmetry including CP-like symmetry. Various scattering amplitudes of CP asymmetry are calculated in CP-like symmetric models. We explicitly show that the CP-like transformation leads to a specific relation between different CP asymmetries. The resultant relation is similar to the one obtained in GUT baryogenesis and sphaleron processes, where we also obtain a required condition for generating particle number asymmetry in CP-like symmetric models. In addition, we propose a generalization of a CP-like transformation for continuous symmetry groups. Since the CP transformation is an outer automorphism, which depends on the internal symmetry group, it turns out that the physical CP and CP-like symmetries can be mutually converted through the spontaneous symmetry breaking (SSB) of the internal symmetry. We investigate properties of physical CP asymmetry in both CP and CP-like symmetric phases, and find that the spontaneous CP violation and restoration can be observed even in models with continuous groups. We demonstrate that CP-like symmetric models with continuous Lie groups can be naturally realized in physical CP symmetric models through the SSB.

Imprinting New Physics by Using Angular Profiles of the Flavor-Changing-Neutral-Current Process Bc → Ds* (→ Dsπ) ℓ+ℓ-

Abstract The decays governed by the flavor-changing-neutral-current (FCNC) transitions, such as $b\rightarrow s\ell ^{+}\ell ^{-}$, provide an important tool to test the physics in and beyond the Standard Model (SM). This work focuses on investigating the FCNC process $B_{c}\rightarrow D_{s}^{*} \left(\rightarrow D_{s}\pi \right)\ell ^{+}\ell ^{-}(\ell =e,\mu ,\tau )$. Being an exclusive process, the initial and final state meson matrix elements involve the form factors, which are nonperturbative quantities and need to be calculated using specific models. By using the form factors calculated in the covariant light-front quark model, we analyze the branching fractions and angular observables such as the forward-backward asymmetry $A_{\mathrm{ FB}}$, polarization fractions (longitudinal and transverse) $F_{L(T)}$, CP asymmetry coefficients $A_{i}$, and CP-averaged angular coefficients $S_{i}$, both in the SM and in some new physics (NP) scenarios. Some of these physical observables are a potential source of finding the physics beyond the SM and help us to distinguish various NP scenarios.

Topological diagram analysis of [formula omitted] decays in the SU(3)F limit and beyond

Charm baryon decay plays an important role in studying non-perturbative baryonic transitions. Compared to other hadron multiplets, the flavor symmetry of baryon decuplet is more simple and attractive. In this work, we study the topological amplitudes of charmed baryon decays into decuplet baryon in the flavor symmetry and the linear SU(3)F breaking. It is found most of topological diagrams are suppressed by the Körner-Pati-Woo theorem in the SU(3)F limit. Only two independent amplitudes contributing to the Bc3‾→B10M decays, with one dominating the branching fractions. The Lee-Yang parameters of all Bc3‾→B10M modes are the same in the SU(3)F limit, and there are only four possible values for the CP asymmetries. After including the first-order SU(3)F breaking effects, the Ξc+→Σ⁎+K‾0 and Ξc+→Ξ⁎0π+ decays have non-zero branching fractions. The number of free parameter contributing to the Bc3‾→B10M decays in the linear SU(3)F breaking is smaller than the available data. The SU(3)F breaking part of the quark loop diagram can be extracted by global fitting of branching fractions, which could help us understand the CP violation in charm sector. Additionally, some new isospin equations are proposed to test the Körner-Pati-Woo theorem.

Purely flavored leptogenesis from a sudden mass gain of right-handed neutrinos

In this paper, we would like to point out that in the scenario that the right-handed neutrinos suddenly gain some masses much larger than the temperature of the Universe at that time so that the washout effects for the lepton asymmetry generated from their decays can be neglected safely, the purely flavored leptogenesis scenario (in which the total CP asymmetries for the decays of the right-handed neutrinos are vanishing and the successful leptogenesis is realized by virtue of the flavor non-universality of the washout effects) cannot work in the usual way any more. For this problem, we put forward that the flavor non-universality of the conversion efficiencies from the flavored lepton asymmetries to the baryon asymmetry via the sphaleron processes may play a crucial role. And we will study if the requisite baryon asymmetry can be successfully reproduced from such a mechanism in the scenarios that the right-handed neutrino masses are hierarchical and nearly degenerate, respectively. A detailed study shows that this mechanism can be viable in both these two scenarios.

CP asymmetries in τ→KSπντ decays

We present here the CP asymmetries in the decay rate and angular distributions of [Formula: see text] decays in the Standard Model (SM) and beyond (BSM). The CP asymmetries in the SM are induced by the CP violation in [Formula: see text] mixing. To investigate the BSM CP-violating (CPV) effects, a model-independent analysis is performed by using the low-energy effective field theory (LEFT) framework at [Formula: see text] GeV. If one further assumes the BSM physics to stem from above the electroweak scale, the LEFT shall then be matched onto the SM effective field theory (SMEFT), the operators of which contributing to [Formula: see text] decays will also contribute to the neutron electric dipole moment (EDM) and [Formula: see text] mixing. The stringent bounds from the latter suggest that no remarkable CPV effects can be observed in either the decay rate or the angular distributions. The prospects for future measurements of these observables are also mentioned.

CP violation induced by neutral meson mixing interference

We investigate a long-overlooked CP violation effect—the double-mixing CP asymmetry—in a type of cascade decay that involves at least two mixing neutral mesons in the decay chain. It is induced by the interference between different oscillation paths of the neutral mesons in the decay process. The double-mixing CP asymmetry is of critical importance for phenomenology, providing opportunities for clean determination of Cabibbo-Kobayashi-Maskawa phase angles free of uncertainties induced by the strong dynamics. To illustrate this point, we perform a phenomenological analysis on two examples: Bs0→ρ0K→ρ0(π−ℓ+νℓ) and B0→D0K→D0(π+ℓ−ν¯ℓ). Our results demonstrate that the double-mixing CP asymmetry can be numerically significant in the absence of strong phases, as shown by the former example. Additionally, the latter example showcases a direct extraction of weak and strong phases from data, without the need for theoretical inputs. Published by the American Physical Society 2024

Enhancement of direct CP asymmetry in Z′ models

We consider CP-violating Z′ models to account for the anomalies in b→sℓℓ decays. Using the updated constraints from lepton flavor universality violating ratios, b→sμμ CP-conserving and CP-violating observables, Bs−B¯s mixing and neutrino trident we obtain the favored parameter space of two classes of Z′ models generating the new physics scenarios with Re[C9μNP]<0 and [C9μNP=−C10μNP,C9eNP=−C10eNP]. We study the predictions of direct CP asymmetry ACP in B+→K+μμ decays and CP asymmetric angular observables in these models. The favored 1σ parameter space of Z′ models generating scenario Re[C9μNP]<0 allows for an enhancement in the integrated ACP in q2=[8,9] GeV2 bin up to ±25%, while the [C9μNP=−C10μNP,C9eNP=−C10eNP] scenario allows only positive values of ACP. However, these ACP values flip sign depending on the choice of J/ψ phase, hence distinguishing these two Z′ models through a measurement in this bin requires a more reliable determination of the J/ψ phase. The prediction of ACP in the q2=[16,17] GeV2 bin are promising as they allow for an enhancement only in the positive direction for [C9μNP=−C10μNP,C9eNP=−C10eNP] scenario, irrespective of the choice of strong phase, while both positive and negative values are allowed for the scenario Re[C9μNP]. We also find that a future more precise measurement of CP-asymmetric angular observables A8 and A9 in the low-q2 bins can provide distinguishing signatures of these two Z′ models and help constrain new physics CP-violating phases. Published by the American Physical Society 2024

CP-violating observables of four-body B(s)→(ππ)(KK¯)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(K\\bar{K})$$\\end{document} decays in perturbative QCD

In this work, we investigate six helicity amplitudes of the four-body B(s)→(ππ)(KK¯)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(K\\bar{K})$$\\end{document} decays via an angular analysis in the perturbative QCD (PQCD) approach. The ππ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi \\pi $$\\end{document} invariant mass spectrum is dominated by the vector resonance ρ(770)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho (770)$$\\end{document} together with scalar resonance f0(980)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_0(980)$$\\end{document}, while the vector resonance ϕ(1020)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi (1020)$$\\end{document} and scalar resonance f0(980)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_0(980)$$\\end{document} are expected to contribute in the KK¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K\\bar{K}$$\\end{document} invariant mass range. We extract the two-body branching ratios B(B(s)→ρϕ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B_{(s)}\\rightarrow \\rho \\phi )$$\\end{document} from the corresponding four-body decays B(s)→ρϕ→(ππ)(KK¯)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}\\rightarrow \\rho \\phi \\rightarrow (\\pi \\pi )(K \\bar{K})$$\\end{document} based on the narrow width approximation. The predicted B(Bs0→ρϕ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B^0_{s}\\rightarrow \\rho \\phi )$$\\end{document} agrees well with the current experimental data within errors. The longitudinal polarization fractions of the B(s)→ρϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}\\rightarrow \\rho \\phi $$\\end{document} decays are found to be as large as 90%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$90\\%$$\\end{document}, basically consistent with the previous two-body predictions within uncertainties. In addition to the direct CP asymmetries, the triple-product asymmetries (TPAs) originating from the interference among various helicity amplitudes are also presented for the first time. Since the Bs0→ρ0ϕ→(π+π-)(K+K-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_s^0\\rightarrow \\rho ^0\\phi \\rightarrow (\\pi ^+\\pi ^-)(K^+K^-)$$\\end{document} decay is induced by both tree and penguin operators, the values of the AdirCP\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{A}^\ extrm{CP}_\ extrm{dir}$$\\end{document} and AT-true1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{A}^{1}_{\ ext {T-true}}$$\\end{document} are calculated to be (21.8-3.3+2.7)%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(21.8^{+2.7}_{-3.3})\\%$$\\end{document} and (-10.23-1.56+1.73)%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(-10.23^{+1.73}_{-1.56})\\%$$\\end{document} respectively. While for pure penguin decays B0→ρ0ϕ→(π+π-)(K+K-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B^0\\rightarrow \\rho ^0\\phi \\rightarrow (\\pi ^+\\pi ^-)(K^+K^-)$$\\end{document} and B+→ρ+ϕ→(π+π0)(K+K-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B^+\\rightarrow \\rho ^+\\phi \\rightarrow (\\pi ^+\\pi ^0)(K^+K^-)$$\\end{document}, both the direct CP asymmetries and “true” TPAs are naturally expected to be zero in the standard model (SM) due to the absence of the weak phase difference. The “fake” TPAs requiring no weak phase difference are usually none zero for all considered decay channels. The sizable “fake” AT-fake1=(-20.92-2.80+6.26)%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{A}^{1}_{\ ext {T-fake}}=(-20.92^{+6.26}_{-2.80})\\%$$\\end{document} of the B0→ρ0ϕ→(π+π-)(K+K-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B^0\\rightarrow \\rho ^0\\phi \\rightarrow (\\pi ^+\\pi ^-)(K^+K^-)$$\\end{document} decay is predicted in the PQCD approach, which provides valuable information on the final-state interactions. The above predictions can be tested by the future LHCb and Belle-II experiments.

Study of Bs→ϕ(ρ0,ω) decays in the standard model and a family nonuniversal Z′ model

Within the QCD factorization approach, we employ the new results of form factors of Bs→ϕ and calculate the branching fractions, CP asymmetries (CPAs) and polarization fractions of the decay modes Bs→ϕ(ρ0,ω) in both the standard model (SM) and the family nonuniversal Z′ model. We find that in SM the above observables are relate to two parameters, ρH and ϕH, which characterize the end-point divergence in the hard spectator-scattering amplitudes. When setting ρH=0.5 and ϕH∈[−180,180]°, the theoretical uncertainties are large. By combining the experimental data, our results can be used to constrain these two parameters. Supposing ρH=0, we study the effects of the Z′ boson on the concerned observables. With the available branching fraction of Bs→ϕρ0, the possible ranges of parameter spaces are obtained. Within the allowed parameter spaces, the branching fraction of Bs→ϕω can be enlarged remarkably. Furthermore, the new introduced weak phase plays important roles in significantly affecting the CPAs and polarization fractions, which are important observables for probing the effects of NP. If these decay modes were measured in the on-going LHC-b and Belle-II experiments in the future, the peculiar deviation from SM could provide a signal of the family nonuniversal Z′ model, which can also be used to constrain the mass of Z′ boson in turn. Published by the American Physical Society 2024

Final-state interactions in the CP asymmetry of D meson two-body decays

Final-state interactions in the CP asymmetry of <i>D</i> meson two-body decays

Measurement of absolute branching fractions of Ds+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\ extrm{D}}_{\ extrm{s}}^{+} $$\\end{document} hadronic decays

Using e+e− collision data collected at the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of 7.33 fb−1, we determine the absolute branching fractions of fifteen hadronic Ds+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}_s^{+} $$\\end{document} decays with a double-tag technique. In particular, we make precise measurements of the branching fractions BDs+→K+K−π+=5.49±0.04±0.07%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{B}\\left({D}_s^{+}\ o {K}^{+}{K}^{-}{\\pi}^{+}\\right)=\\left(5.49\\pm 0.04\\pm 0.07\\right)\\% $$\\end{document}, BDs+→KS0K+=1.50±0.01±0.01%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{B}\\left({D}_s^{+}\ o {K}_S^0{K}^{+}\\right)=\\left(1.50\\pm 0.01\\pm 0.01\\right)\\% $$\\end{document} and BDs+→K+K−π+π0=5.50±0.05±0.11%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{B}\\left({D}_s^{+}\ o {K}^{+}{K}^{-}{\\pi}^{+}{\\pi}^0\\right)=\\left(5.50\\pm 0.05\\pm 0.11\\right)\\% $$\\end{document}, where the first uncertainties are statistical and the second ones are systematic. The CP asymmetries in these decays are also measured and all are found to be compatible with zero.

Washout processes in post-sphaleron baryogenesis from way-out-of-equilibrium decays

We study washout processes in post-sphaleron baryogenesis, a mechanism where the matter–antimatter asymmetry is generated in the decay of exotic particles after the electroweak phase transition. In particular we focus, in a quite model independent way, on those scattering processes that have an amplitude proportional to the CP asymmetry. We find that when the scatterings involve only massless particles, the washouts are very severe for light decaying particles (with masses below a few hundred of GeV) and successful baryogenesis is only possible in a small portion of parameter space. Instead, if even a very light particle participates in these processes, the allowed region of parameter space opens considerably, although the final amount of baryon asymmetry may differ significantly from the expression which is typically used and neglects washouts. Furthermore, we analyze washouts from the non-thermal spectrum of energetic particles produced in cascade decays and indicate in which models they can be relevant.

Measurement of branching-fraction ratios and CP asymmetries in B± → DCP±K± decays at Belle and Belle II

We report results from a study of B±→ DK± decays followed by D decaying to the CP-even final state K+K− and CP-odd final state KS0π0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {K}_S^0{\\pi}^0 $$\\end{document}, where D is an admixture of D0 and D¯0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\overline{D}}^0 $$\\end{document} states. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angle ϕ3. The results are based on a combined analysis of the final data set of 772 × 106BB¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ B\\overline{B} $$\\end{document} pairs collected by the Belle experiment and a data set of 198 × 106BB¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ B\\overline{B} $$\\end{document} pairs collected by the Belle II experiment, both in electron-positron collisions at the Υ(4S) resonance. We measure the CP asymmetries to be A\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{A} $$\\end{document}CP+ = (+12.5 ± 5.8 ± 1.4)% and A\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{A} $$\\end{document}CP− = (−16.7 ± 5.7 ± 0.6)%, and the ratios of branching fractions to be R\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{R} $$\\end{document}CP+ = 1.164 ± 0.081 ± 0.036 and R\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{R} $$\\end{document}CP− = 1.151 ± 0.074 ± 0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries A\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{A} $$\\end{document}CP+ and A\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{A} $$\\end{document}CP− have similar magnitudes and opposite signs; their difference corresponds to 3.5 standard deviations. From these values we calculate 68.3% confidence intervals of (8.5° < ϕ3 < 16.5°) or (84.5° < ϕ3 < 95.5°) or (163.3° < ϕ3 < 171.5°) and 0.321 < rB < 0.465.

Low-scale baryogenesis from three-body decays

Baryogenesis at the TeV scale from CP-violating decays of a massive particle requires some way to avoid the washouts from processes closely related to the existence of CP violation. Baryogenesis from three-body decays (instead of two-body decays) has been proposed as a way for TeV scale baryogenesis. In this work we revisit this statement and show that, although three-body-decay models can provide interesting alternatives to address other kind of difficulties faced by low-scale baryogenesis, the generic problem due to the washouts proportional to the CP asymmetry persists. Therefore, as in two-body-decay models, the mass of the decaying particle cannot be below ∼10 TeV unless some mechanism to avoid these kinds of washouts is implemented. Published by the American Physical Society 2024

Observation of J/ψ decays to e+e−e+e− and e+e−μ+μ−

Using a data sample of 4.481×108 ψ(3686) events collected with the BESIII detector, we report the first observation of the four-lepton-decays J/ψ→e+e−e+e− and J/ψ→e+e−μ+μ− utilizing the process ψ(3686)→π+π−J/ψ. The branching fractions are determined to be [5.48±0.31(stat)±0.45(syst)]×10−5 and [3.53±0.22(stat)±0.13(syst)]×10−5, respectively. The results are consistent with theoretical predictions. No significant signal is observed for J/ψ→μ+μ−μ+μ−, and an upper limit on the branching fraction is set at 1.6×10−6 at the 90% confidence level. A CP asymmetry observable is constructed for the first two channels, which is measured to be (−0.012±0.054±0.010) and (0.062±0.059±0.006), respectively. No evidence for CP violation is observed in this process. Published by the American Physical Society 2024

Improved Measurement of CP Violation Parameters in B_{s}^{0}→J/ψK^{+}K^{-} Decays in the Vicinity of the ϕ(1020) Resonance.

The decay-time-dependent CP asymmetry in B_{s}^{0}→J/ψ(→μ^{+}μ^{-})K^{+}K^{-} decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb^{-1}, collected with the LHCb detector at a center-of-mass energy of 13TeV. Using a sample of approximately 349 000 B_{s}^{0} signal decays with an invariant K^{+}K^{-} mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕ_{s} is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B_{s}^{0}-B[over ¯]_{s}^{0} system, ΔΓ_{s}, and the difference of the average B_{s}^{0} and B^{0} meson decay widths, Γ_{s}-Γ_{d}. The values obtained are ϕ_{s}=-0.039±0.022±0.006 rad, ΔΓ_{s}=0.0845±0.0044±0.0024 ps^{-1}, and Γ_{s}-Γ_{d}=-0.0056_{-0.0015}^{+0.0013}±0.0014 ps^{-1}, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ϕ_{s} is also measured independently for each polarization state of the K^{+}K^{-} system and shows no evidence for polarization dependence.

B¯→D¯D\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{B}\ o \\overline{D}D $$\\end{document} decays and the extraction of fd/fu at hadron colliders

We perform a detailed model-independent phenomenological analysis of B¯→D¯D\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{B}\ o \\overline{D}D $$\\end{document} decays. Employing an SU(3)F analysis including symmetry-breaking contributions together with a conservative power counting for various suppression effects, we obtain updated Standard Model predictions for all branching fractions and CP asymmetries from a fit to the available experimental data, testable at Belle II and the LHC experiments. These results include all relevant suppressed contributions, thereby providing upper limits on subleading Standard Model (SM) effects like “penguin pollution”, enabling searches for physics beyond the SM. Importantly, allowing in the same fit for the production fractions of charged and neutral B mesons to be different, we find fd/fu = 0.86 ± 0.05, which is 2.5σ away from unity, which, if confirmed, would have important phenomenological consequences.

Top quark anomalous couplings from top-pair tagged photoproduction at pe− colliders

We summarize the quantitative results of our analysis [1] of top-pair photoproduction in semileptonic mode in pe collisions at the LHeC and FCC-he. We define three photoproduction regions, based on the rapidity acceptance range of the electron tagger, that provide different degrees of sensitivity to top-quark effective couplings. We focus on the ttγ dipole couplings and the left-handed vector tbW coupling, for which we determine limits at both energies in the different photoproduction regions. Furthermore, we find that the LHeC and FCC-he will yield tight direct bounds on top dipole moments, greatly improving on current direct limits from hadron colliders, and direct limits on the tbW coupling as restrictive as those expected from the HL-LHC. We also consider indirect limits from b → sγ branching ratio and CP asymmetry, that are well known to be very sensitive probes of top electromagnetic dipole moments.

Measurement of branching fractions and direct CP asymmetries for B→Kπ and B→ππ decays at Belle II

We report measurements of the branching fractions and direct CP asymmetries of the decays B0→K+π−, B+→K+π0, B+→K0π+, and B0→K0π0, and use these for testing the standard model through an isospin-based sum rule. In addition, we measure the branching fraction and direct CP asymmetry of the decay B+→π+π0 and the branching fraction of the decay B0→π+π−. The data are collected with the elle II detector from e+e− collisions at the ϒ(4S) resonance produced by the SuperKEKB asymmetric-energy collider and contain 387×106 bottom-antibottom meson pairs. Signal yields are determined in two-dimensional fits to background-discriminating variables, and range from 500 to 3900 decays, depending on the channel. We obtain −0.03±0.13±0.04 for the sum rule in agreement with the standard model expectation of zero and with a precision comparable to the best existing determinations. Published by the American Physical Society 2024

Study of four-body decays B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} in the perturbative QCD approach

In this work, we make a systematical study on the four-body B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} decays in the perturbative QCD (PQCD) approach, where the ππ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi \\pi $$\\end{document} invariant mass spectra are dominated by the vector resonance ρ(770)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho (770)$$\\end{document} and the scalar resonance f0(980)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_0(980)$$\\end{document}. We improve the Gengenbauer moments for the longitudinal P-wave two-pion distribution amplitudes (DAs) by fitting the PQCD factorization formulas to measured branching ratios of three-body and four-body B decays. With the fitted Gegenbauer moments, we make predictions for the branching ratios and direct CP asymmetries of four-body B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} decays. As a by-product, we extract the branching ratios of two-body B(s)→ρρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow \\rho \\rho $$\\end{document} from the corresponding four-body decay modes and calculate the relevant polarization fractions. We find that the B(B0→ρ+ρ-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B^0 \\rightarrow \\rho ^+\\rho ^-)$$\\end{document} is consistent with the previous theoretical predictions and data. The leading-order PQCD calculations of the B(B+→ρ+ρ0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B^+\\rightarrow \\rho ^+\\rho ^0)$$\\end{document}, B(B0→ρ0ρ0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B^0\\rightarrow \\rho ^0\\rho ^0)$$\\end{document} and the f0(B0→ρ0ρ0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_0(B^0\\rightarrow \\rho ^0\\rho ^0)$$\\end{document} are a bit lower than the experimental measurements, which should be further examined. It is shown that the direct CP asymmetries are large when both tree and penguin contributions are comparable to each other, but small for the tree-dominant or penguin-dominant processes. In addition to the direct CP asymmetries, the “true” and “fake” triple-product asymmetries (TPAs) originating from the interference among various helicity amplitudes in the B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}\\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} decays are also analyzed. The sizable averaged TPA AT-true1,ave=25.26%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{A}_{\ ext {T-true}}^{1, \ ext {ave}}=25.26\\%$$\\end{document} of the color-suppressed decay B0→ρ0ρ0→(π+π-)(π+π-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B^0\\rightarrow \\rho ^0\\rho ^0 \\rightarrow (\\pi ^+\\pi ^-)(\\pi ^+\\pi ^-)$$\\end{document} is predicted for the first time, which deviates a lot from the so-called “true” TPA AT-true1=7.92%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {A}_\ ext {T-true}^1=7.92\\%$$\\end{document} due to the large direct CP violation. A large “fake” TPA AT-fake1=24.96%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {A}_\ ext {T-fake}^1=24.96\\%$$\\end{document} of the decay B0→ρ0ρ0→(π+π-)(π+π-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B^0\\rightarrow \\rho ^0\\rho ^0 \\rightarrow (\\pi ^+\\pi ^-)(\\pi ^+\\pi ^-)$$\\end{document} is also found, which indicates the significance of the final-state interactions. The predictions in this work can be tested by LHCb and Belle-II experiments in the near future.