Direct CP Asymmetries Research Articles

The resonance effect for the CP asymmetry associated with the process $\omega \rightarrow \pi^{+}\pi^{-}\pi^{0}$

Abstract The direct CP asymmetry in the weak decay process of hadrons is commonly attributed to the weak phase of the CKM matrix and the indeterminate strong phase. We propose a method to generate a significant phase difference through the interference between $\rho$ and $\omega$ mesons, taking into account the G-parity allowed decay process of $\omega \rightarrow \pi^{+}\pi^{-}\pi^{0}$ and the G-parity suppressed decay process of $\rho^{0} \rightarrow \pi^{+}\pi^{-}\pi^{0}$ in B meson decays. 
It can lead to a significant CP asymmetry changes in the interference region. 
Besides, we also calculate the integral results of different phase space regions for the four-body decay process. We hope that our work can offer valuable theoretical guidance for future experimental investigations on CP asymmetry in these decays.Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

CP -odd window into long distance dynamics in rare semileptonic B decays

We consider the combined measurements of CP-averaged decay rates and direct CP asymmetries of B±→K±ℓ+ℓ− and B±→π±ℓ+ℓ− to probe (nonlocal) four-quark operator matrix element contributions to rare semileptonic B meson decays. We also explore how their effects could be in principle disentangled from possible local new physics effects using U-spin relations. To this end, we construct a ratio of CP-odd decay rate differences which are exactly predicted within the standard model in the U-spin limit, while the leading U-spin breaking effects can also be systematically calculated. Our results motivate binned measurements of the direct CP asymmetry in B±→π±ℓ+ℓ− as well as dedicated theoretical estimates of U-spin breaking both in local form factors as well as in four-quark matrix elements. 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.

Determination of the D→ππ ratio of penguin over tree diagrams

We study the penguin over tree ratio in D→ππ decays. This ratio can serve as a probe for rescattering effects. Assuming the Standard Model and in the isospin limit, we derive expressions that relate both the magnitude and the phase of this ratio to direct CP asymmetries and branching fractions. We find that the current data suggest that rescattering is large. A dedicated experimental analysis with current and future data will be able to significantly reduce the errors on these determinations, and enable us to check if indeed there is significant rescattering in D→ππ decays. Published by the American Physical Society 2024

Study of Bs0→TT(a2(1320), K2*(1430), f2(1270), f2′(1525)) in the perturbative QCD approach

In the present study, the calculations of two-body decays Bs0→TT [T denotes tensor mesons, a2(1320), K2*(1430), f2(1270), f2′(1525)] in the perturbative QCD approach are presented. The ensuing predictions encompass branching ratios, polarization fractions, and direct CP violations, all elucidated in comprehensive detail. It is discerned that (1) for pure annihilation decay, the longitudinal polarization is around 90.0%, whereas the transverse polarizations manifest comparatively diminutive magnitudes. (2) The direct CP asymmetry is directly proportional to the interference between the tree and penguin contributions. For most of the decays investigated within this discourse, the direct CP asymmetry remains modest in magnitude. (3) There are precisely six distinct categories of Feynman diagrams for Bs0→TT, because the tensor mesons cannot be produced through the (V±A) currents or (S±P) density, thereby prohibiting factorizable emission diagrams. The nonfactorizable and annihilation contributions are ascertained to be pivotal in these decay modes. The calculated branching ratios of our calculation for Bs0→TT are at the order of 10−6 and 10−7, which can be tested in the LHCb and Belle II experiments. (4) Mixing exists for the f2(1270) and f2′(1525), just as the η and η′ mixing, the branching ratios about the mixing angle θ are given in this work. However, it is different from f1(1285)−f1(1420), the mixing angle is notably small, thereby resulting in only marginal alterations in the decay branching ratios. Published by the American Physical Society 2024

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.

CP asymmetries in B meson two-body baryonic decays

We study the CP-odd and CP-even observables of the B mesons decaying into a baryon and antibaryon. We estimate these observables through the P03 model and chiral selection rule. The decay branching ratio of B+→pΛ‾ is calculated to be (2.31±0.69)×10−7, which is consistent with the current experiments. The effects of the B−B‾ oscillations are considered, which largely suppress the direct CP asymmetries in the Bs0 decays. We suggest the experiments to visit Bs0→Λ(→pπ−)Λ‾(→p‾π+), where the time-averaged CP-odd observables are estimated to be large. The direct CP asymmetries of B+→pΛ‾ and B0→pp‾ are found to be (26.2±7.9)% and (−3.1±0.9)% for a positive strong phase and (−36.9±11.1)% and (4.2±1.3)% for a negative strong phase, respectively.

CP asymmetry in τ → Kπντ within non-minimal SU(5)

Direct CP asymmetry in semi-leptonic τ decays is an intriguing hint for new physics beyond the standard model. We investigate the CP asymmetry in {tau}^{-}to {K}_S^0{pi}^{-}{nu}_{tau } and τ− → K−π0ντ decays in the context of the non-minimal SU(5) model, with 45-dimensional Higgs multiplet. We show that the associate color-triplet scalar, which is a natural example of a scalar leptoquark, can mediate the tau to soverline{u}{nu}_{tau } transition and account for the observed 2.8 σ discrepancy in {A}_{textrm{CP}}left({tau}^{-}to {K}_S^0{pi}^{-}{nu}_{tau}right) compared to the SM expectation. We also predict a sizable ACP(τ− → K−π0ντ), of mathcal{O} (10−3), which can be experimentally accessible in current and near future experiments.

Study of the b → dℓℓ transitions in the Standard Model and test of New Physics sensitivities

After incorporating all the available experimental data and the most up-to-date Lattice and light cone sum rule (LCSR) inputs on the form factors, we analyze the exclusive b → uℓνℓ and b → dℓℓ decays simultaneously. We have extracted the shapes of all the associated form factors using which we have provided predictions in the standard model for the branching ratios, direct CP asymmetries and isospin asymmetry for B → πℓℓ and various angular observables for B → ρℓℓ transitions. Also, we have tested the sensitivities of these observables towards physics beyond the standard model (BSM). For the B → ρℓℓ decays, we have defined tagged and untagged observables and predicted them in the SM and BSM. In the context of BSM, we have found some compelling information. The respective predictions in a few benchmark scenarios are given, which can be tested in the experiments at the LHCb and the Belle.

A U-spin anomaly in charm CP violation

Recent LHCb data shows that the direct CP asymmetries of the decay modes D0 → π+π− and D0 → K+K− have the same sign, violating an improved U-spin limit sum rule in an unexpected way at 2.1σ. From the new data, we determine for the first time the imaginary part of the CKM-subleading, U-spin breaking ∆U = 1 correction to the U-spin limit ∆U = 0 amplitude. The imaginary part of the ∆U = 0 amplitude is determined by Delta {a}_{textrm{CP}}^{textrm{dir}} . The corresponding strong phases are yet unknown and could be extracted in the future from time-dependent measurements. Assuming mathcal{O}(1) strong phases due to non-perturbative rescattering, we find the ratio of U-spin breaking to U-spin limit contributions to the CKM-subleading amplitudes to be left({173}_{hbox{--} 74}^{+85}right)% . This highly exceeds the Standard Model (SM) expectation of ~ 30% U -spin breaking, with a significance of 1.95σ. If this puzzle is confirmed with more data in the future, in the SM it would imply the breakdown of the U -spin expansion in CKM-subleading amplitudes of charm decays. The other solution are new physics models that generate an additional ∆U = 1 operator, leaving the U-spin power expansion intact. Examples for the latter option are an extended scalar sector or flavorful Z′ models.

Fingerprinting CP-violating New Physics with B → Kμ+μ−

The B → Kℓ+ℓ− system is particularly interesting to explore physics beyond the Standard Model. Such effects could provide new sources of CP violation, thereby giving rise to Wilson coefficients which could not only be real, as assumed in most analyses, but also be complex. We propose a new strategy to extract the complex C9μ, C10μ from the data, utilising the complementarity of direct CP violation in B+ → K+μ+μ− and mixing-induced CP violation arising — in addition to direct CP violation — in {B}_d^0to {K}_S{mu}^{+}{mu}^{-} , as well as the differential rate in appropriate q2 bins. The long-distance effects, which play a key role to generate the direct CP asymmetries, cannot be reliably calculated due to their non-perturbative nature. In order to describe them, we apply a model by the LHCb Collaboration employing experimental data. Assuming specific scenarios, we demonstrate the fingerprinting of CP-violating New Physics and the distinction between ambiguities in the model of the long-distance contributions. Finally, New Physics could couple differently to muons and electrons, as probed through the lepton flavour universality ratio RK. We discuss these effects in the presence of CP violation and present a new way to measure the direct CP asymmetries of the B → Ke+e− channels.

Angular analysis of the low K+K− invariant mass enhancement in B+→K+K−π+ decays

We study the decay B+→K+K−π+ and investigate the angular distribution of K+K− pairs with invariant mass below 1.1 GeV/c2. This region exhibits both a strong enhancement in signal and very large direct CP violation. We construct a coherent sum model for the angular distribution of the S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of MK+K− and the differential branching fractions in bins of MK+π−. The results are based on a data sample that contains 772×106 BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. The result favors the presence of S- and D-waves in low MK+K− region to the detriment of a P-wave.1 MoreReceived 24 June 2022Accepted 3 February 2023DOI:https://doi.org/10.1103/PhysRevD.107.032013Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBranching fractionHadronic decaysParticle decaysRare decaysPhysical SystemsMesonsPropertiesCP violationParticles & Fields

Search for [formula omitted] violation and measurement of branching fractions and decay asymmetry parameters for [formula omitted] and [formula omitted] ([formula omitted

We report a study of Λc+→Λh+ and Λc+→Σ0h+ (h=K,π) decays based on a data sample of 980fb-1 collected with the Belle detector at the KEKB energy-asymmetric e+e- collider. The first results of direct CP asymmetry in two-body singly Cabibbo-suppressed (SCS) decays of charmed baryons are measured, ACPdir(Λc+→ΛK+)=+0.021±0.026±0.001 and ACPdir(Λc+→Σ0K+)=+0.025±0.054±0.004. We also make the most precise measurement of the decay asymmetry parameters (α) for the four modes of interest and search for CP violation via the α-induced CP asymmetry (ACPα). We measure ACPα(Λc+→ΛK+)=-0.023±0.086±0.071 and ACPα(Λc+→Σ0K+)=+0.08±0.35±0.14, which are the first ACPα results for SCS decays of charmed baryons. We search for Λ-hyperon CP violation in Λc+→(Λ,Σ0)π+ and find ACPα(Λ→pπ-)=+0.013±0.007±0.011. This is the first time that hyperon CP violation has been measured via Cabibbo-favored charm decays. No evidence of baryon CP violation is found. We also obtain the most precise branching fractions for two SCS Λc+ decays, B(Λc+→ΛK+)=(6.57±0.17±0.11±0.35)×10-4 and B(Λc+→Σ0K+)=(3.58±0.19±0.06±0.19)×10-4. The first uncertainties are statistical and the second systematic, while the third uncertainties come from the uncertainties on the world average branching fractions of Λc+→(Λ,Σ0)π+.

Zooming into CP violation in B(s)→ hh decays

The LHCb collaboration has recently reported the first observation of CP violation in the penguin-dominated {B}_s^0 → K−K+ decay and further new measurements, indicating differences between the direct CP asymmetries of both the {B}_s^0 → K−K+, {B}_d^0 → π−K+ and the {B}_d^0 → π−π+, {B}_s^0 → K−π+ modes. We show that these puzzling differences can be accommodated through sizeable penguin annihilation and exchange topologies in the Standard Model, and constrain them. Utilising the U-spin symmetry, we extract the angle γ of the unitarity triangle from the CP asymmetries in the {B}_s^0 → K−K+, {B}_d^0 → π−π+ system alone, finding gamma =left({65}_{-7}^{+11}right){}^{circ} , in perfect agreement with the determination from tree-level B → DK decays. The {B}_s^0-{overline{B}}_s^0 mixing phase ϕs can be extracted from CP violation measurements in {B}_s^0 → K−K+ in a clean way. We present a new strategy and extract ϕs = −(3.6 ± 5.4)°. This result is in agreement with the determination from {B}_s^0 → J/ψϕ decays. New CP-violating contributions would influence these determinations differently. Hence it is interesting to keep monitoring both as the experimental picture sharpens.

Phenomenological studies on neutral B-meson decays into J/psi f_1 and eta _c f_1

The axial-vector mesons f_1(1285) and f_1(1420) are particularly viewed as the mixtures of flavor states f_n and f_s with mixing angle varphi . In order to determine this angle, we study the B_{d,s}^0rightarrow J/psi f_1(1285,1420) and B_{d,s}^0rightarrow eta _c f_1(1285,1420) decays in perturbative QCD (PQCD) approach, including the effects of vertex corrections, nonfactorizable diagrams and penguin operators. Not only the branching fractions, but also the direct CP asymmetries and the polarization fractions are calculated. It is found that the branching fractions of these decays are large enough to be measured in the running LHCb and Belle-II experiments. Moreover, in comparison with the observed {mathcal {B}}(B_{d,s}^0 rightarrow J/psi f_1(1285)), B_s^0 rightarrow (J/psi , eta _c) f_1(1420) decays have large branching fractions, which could be measured promisingly through f_1(1420) rightarrow K_S^0 K^pm pi ^mp in experiments. We also propose several ratios that could be used to further constrain the absolute value of the mixing angle varphi , but its sign cannot be determined yet in these decays. The direct CP asymmetries of these decays indicate the penguin pollution in the B_d^0 rightarrow (J/psi , eta _c) f_1 decays cannot be neglected. We acknowledge that there are large theoretical uncertainties arising from the distribution amplitudes of axial-vector mesons and charmonium states, and more precise nonperturbative parameters are called. The comparisons between our results and future experimental data would help us to understand the nature of f_1 states and to test the PQCD approach.

Charmless two-body B meson decays in the perturbative QCD factorization approach* *Supported by the National Science Foundation of China (11805060, 11975112, 12105028, 12070131001, 11775117), the Joint Large-Scale Scientific Facility Funds of the NSFC and CAS (U1932110), the Natural Science Foundation of Jiangsu Province (BK20200980) and the National Key Research and Development Program of China (2020YFA0406400)

The perturbative quantum chromodynamics (PQCD) approach based on factorization has resulted in great achievements in the QCD calculation of hadronic B decays. By regulating the endpoint divergence by the transverse momentum of quarks in the propagators, one can perform the perturbation calculation for various diagrams, including annihilation type diagrams. In this paper, we review the current status of the PQCD factorization calculation of two-body charmless U decays up to next-to-leading order (NLO) QCD corrections. Two new power suppressed terms in the decaying amplitudes are also considered. Using universal input (non-perturbative) parameters, we collect the branching ratios and asymmetry parameters of all charmless two body B decays, which are calculated in the PQCD approach up to NLO. The results are compared with those of the QCD factorization approach, soft-collinear effective theory approach, and current experimental measurements. For most of the considered B meson decays, the PQCD results for branching ratios agree well with those of other approaches and experimental data. The PQCD predictions for the asymmetry parameters of many of the decay channels do not agree with those of other approaches but have better agreement with experimental data. The longstanding puzzle regarding the pattern of the direct CP asymmetries of penguin-dominated decays can be understood after the inclusion of NLO contributions in PQCD. The NLO corrections and power suppressed terms play an important role in color suppressed and pure annihilation type B decay modes. These rare decays are more sensitive to different types of corrections, providing an opportunity to examine the factorization approach with more precise experimental measurements.

Quasi-two-body decays in the perturbative QCD approach* *Supported in part by the National Natural Science Foundation of China under (11347030), the Program of Science and Technology Innovation Talents in Universities of Henan Province (14HASTIT037)

In this study, we investigate quasi-two-body decays in the perturbative QCD approach. Two-meson distribution amplitudes are introduced to describe the final state interactions of the pair, which involve time-like form factors and Gegenbauer polynomials. We calculate the CP averaged branching ratios of the decays. Our results are in agreement with newly updated data measured by Belle II. This suggests that it is more appropriate to analyze these quasi-two-body B decays in the three-body framework than the two-body framework. We also predict direct CP asymmetries for the considered decay modes and find that is small and less than % in magnitude, whereas is larger and can reach a few percent. Our predictions can be tested in future B meson experiments.

Tasting flavoured Majorana dark matter

We study a simplified model of flavoured Majorana dark matter in the Dark Minimal Flavour Violation framework. The model extends the Standard Model by a dark matter flavour triplet and a scalar mediator, through which the new dark fermions couple to right-handed up-type quarks. This interaction is governed by a new coupling matrix λ which is assumed to constitute the only new source of flavour and CP violation. We analyse the parameter space of this model by using constraints from collider searches, D0− overline{D} 0 mixing, cosmology and direct dark matter searches. Throughout our study, we point out crucial differences between the Majorana and Dirac dark matter cases. After performing a combined analysis within the context of all the experimental constraints mentioned above, we analyse which flavour for the dark matter particle is preferred by experimental data. We further investigate if this model is capable of explaining the large measured value of the direct CP asymmetry Delta {A}_{mathrm{CP}}^{mathrm{dir}} in charm decays. We find that significant enhancements with respect to the Standard Model expectation are compatible with all constraints, and even the central value of the measurement can be reached. We also advertise the flavour-violating final state with two same-sign top quarks produced in association with missing transverse energy as a smoking-gun signature for flavoured Majorana dark matter at the LHC.