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Register a new userStudy of CP violation and CPT violation in $K^{ast}(892)rightarrow K_{S,L}^{0}pi$ decays at BESIII
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Xiao-Dong Cheng Xiao-Dong Cheng
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2021
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The decays $K^{ast}(892)rightarrow K_{S,L}^{0}pi$ can be used to study CP violation and CPT violation. The $K^{ast}(892)$ meson can be produced via $J/psi$ decays at BESIII. In this paper, we study CP violation and CPT violation in $K^{ast}(892)rightarrow K_{S,L}^{0}pi$ decays at BESIII. Basing on two cases: the samples of $10^{10}$ and $10^{12}$ $J/psi$ events, we calculate the expected numbers of the observed signal events on the CP violation in $J/psi$ decays with $K^{ast}(892)$ meson in the final states, we find that the BESIII experiment may be able to unambiguously observe CP violation for each of these two cases. Under the assumption that the observed event on CPT violation is absent, we discuss the upper limits on the absolute value of the CPT violation parameter $Re(z)$ in $J/psi$ decays involving $K^{ast}(892)$ meson in the final states with $10^{10}$ $J/psi$ events and $10^{12}$ $J/psi$ events, respectively. By using the accumulated $10^{10}$ $J/psi$ events, the upper limits on $left|Re(z)right|$ can be obtained at the $90%$ confidence level of $10^{-4}-10^{-5}$, which is competitive with the current best result, if the detection efficiency $varepsilon_{K^0_{L}}$ is assumed to be at the level of $8times 10^{-3}$ at BESIII. And besides, the upper limits on $left|Re(z)right|$ will be improved by about two orders of magnitude compared with the current best result with $10^{12}$ $J/psi$ events.
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The three-body charmless hadronic decay $B^0_s rightarrow K^{0}_{rm S} pi^{+}pi^{-}$ provides a number of novel possibilities to search for CP violation effects and test the Standard Model of particle physics. These include fits to the Dalitz-plot distributions of the decay-time-integrated final state, decay-time-dependent (but without initial state flavour tagging) fits to the Dalitz-plot distribution, as well as full decay-time-dependent and flavour tagged fits. The relative sensitivities of these different approaches are investigated.
Using an $e^{+}e^{-}$ annihilation data sample corresponding to an integrated luminosity of $3.19~mathrm{fb}^{-1}$ and collected at a center-of-mass energy $sqrt{s} = 4.178~mathrm{GeV}$ with the BESIII detector, we measure the absolute branching fractions $mathcal{B}(D_{s}^{+} rightarrow K_{S}^{0}K^{+}) = (1.425pm0.038_{rm stat.}pm0.031_{rm syst.})%$ and $mathcal{B}(D_{s}^{+} rightarrow K_{L}^{0}K^{+}) =(1.485pm0.039_{rm stat.}pm0.046_{rm syst.})%$. The branching fraction of $D_{s}^{+} rightarrow K_{S}^{0}K^{+}$ is compatible with the world average and that of $D_{s}^{+} rightarrow K_{L}^{0}K^{+}$ is measured for the first time. We present the first measurement of the $K_{S}^{0}$-$K_{L}^{0}$ asymmetry in the decays $D_{s}^{+} rightarrow K_{S,L}^{0}K^{+}$, and $R(D_{s}^{+} rightarrow K_{S,L}^{0}K^{+})=frac{mathcal{B}(D_{s}^{+} rightarrow K_{S}^{0}K^{+}) -mathcal{B}(D_{s}^{+} rightarrow K_{L}^{0}K^{+})}{mathcal{B}(D_{s}^{+} rightarrow K_{S}^{0}K^{+}) +mathcal{B}(D_{s}^{+} rightarrow K_{L}^{0}K^{+})}= (-2.1pm1.9_{rm stat.}pm1.6_{rm syst.})%$. In addition, we measure the direct $CP$ asymmetries $A_{rm CP}(D_{s}^{pm} rightarrow K_{S}^{0}K^{pm}) = (0.6pm2.8_{rm stat.}pm0.6_{rm syst.})%$ and $A_{rm CP}(D_{s}^{pm} rightarrow K_{L}^{0}K^{pm}) = (-1.1pm2.6_{rm stat.}pm0.6_{rm syst.})%$.
In this paper we study the direct CP asymmetry of the doubly Cabibbo-suppressed decay mode $D^0 to K^+ pi^- $ within standard model and two Higgs doublet model with generic Yukawa structure. In the standard model we derive the corrections to the tree level amplitude, generated from the box and di-penguin diagrams, required for generating the weak CP violating phases. We show that these phases are so tiny leading to a direct CP asymmetry of order $10^{-9}$. Regarding the two Higgs doublet model with generic Yukawa structure we derive the Wilson coefficients relevant to $D^0 to K^+ pi^- $. After taking into account all constraints on the parameter space of the model we show that charged Higgs couplings to quarks can lead to a direct CP asymmetry of order $10^{-3}$ which is $6$ orders of magnitude larger than the standard model prediction.
The large data sample of the $B_c$ meson collected at the LHC experiment and the HL-LHC experiment provides us the opportunity to study the $B_c$ decays and the related physics. In this paper, we investigate the effect of $K^0-bar{K}^0$ mixing on the the branching ratios, CP violations and CPT violations in the $B_{c}^{pm}rightarrow B^{pm} K_{S,L}^{0}$ decays. We find that some of the $B_c^{pm}rightarrow B^{pm} K_{S,L}^0rightarrow f_{B^{pm}} f_{K_{S,L}^0}$ decay chains have large branching ratios, whose maximum value can exceed the order of $10^{-6}$, the minimum number of $B_c^pm$ events times efficiency for observing the decays at three standard deviations (3$sigma$) level is about $ 10^6$. We study the CP asymmetries in the $B_c^{pm}rightarrow B^{pm} K_{S,L}^0$ decays and find that the CP asymmetries can exceed the order of $10^{-3}$, which are dominated by $K^0-bar{K}^0$ mixing. We give the most promising processes to observe the CP violations and the ranges of the numbers of $B_c^pm$ events-times-efficiency needed to observe the CP asymmetries at a significance of 3$sigma$ in these decays. We investigate the possibility to constraint the CPT violation parameter $Re(z)$ in the $B_c^{pm}rightarrow B^{pm} K_{S,L}^0rightarrow f_{B^{pm}} f_{K_{S,L}^0}$ decays and give the most promising processes to extract the parameter $Re(z)$. We find that the sensitivity for the measurement of parameter $Re(z)$ can reach below $10^{-3}$ in the most promising decays if we assume the selection efficiency is $10^{-3}$ and the total number of $B_c^{pm}$ events collected by the LHCb experiment is $10^{12}$ in the HL-LHC era.
Searches for $CP$ violation in the two-body decays $D_{(s)}^{+}rightarrow h^{+}pi^{0}$ and $D_{(s)}^{+} rightarrow h^{+}eta$ (where $h^{+}$ denotes a $pi^{+}$ or $K^{+}$ meson) are performed using $pp$ collision data collected by the LHCb experiment corresponding to either 9 fb$^{-1}$ or 6 fb$^{-1}$ of integrated luminosity. The $pi^{0}$ and $eta$ mesons are reconstructed using the $e^{+}e^{-}gamma$ final state, which can proceed as three-body decays $pi^{0}rightarrow e^{+}e^{-}gamma$ and $eta rightarrow e^{+}e^{-}gamma$, or via the two-body decays $pi^{0}rightarrow gammagamma$ and $etarightarrowgammagamma$ followed by a photon conversion. The measurements are made relative to the control modes $D_{(s)}^{+}rightarrow K_{S}^{0} h^{+}$ to cancel the production and detection asymmetries. The $CP$ asymmetries are measured to be begin{align} mathcal{A}_{CP}(D^{+}rightarrow pi^{+}pi^{0}) &= (-1.3 pm 0.9 pm 0.6 )%, end{align} begin{align} mathcal{A}_{CP}(D^{+}rightarrow K^{+}pi^{0}) &= (-3.2 pm 4.7 pm 2.1 )%, end{align} begin{align} mathcal{A}_{CP}(D^{+}rightarrow pi^{+}eta) &= (-0.2 pm 0.8 pm 0.4 )%, end{align} begin{align} mathcal{A}_{CP}(D^{+}rightarrow K^{+}eta) &= (-6 pm 10 pm 4 )%, end{align} begin{align} mathcal{A}_{CP}(D_{s}^{+}rightarrow K^{+}pi^{0}) &= (-0.8 pm 3.9 pm 1.2 )%, end{align} begin{align} mathcal{A}_{CP}(D_{s}^{+}rightarrow pi^{+}eta) &= (0.8 pm 0.7 pm 0.5 )%, end{align} begin{align} mathcal{A}_{CP}(D_{s}^{+}rightarrow K^{+}eta) &= (0.9 pm 3.7 pm 1.1 )%, end{align} where the first uncertainties are statistical and the second systematic. These results are consistent with no $CP$ violation and mostly constitute the most precise measurements of $mathcal{A}_{CP}$ in these decay modes to date.
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