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Register a new userExtracting CP violation and strong phase in D decays by using quantum correlations in psi(3770)-> D0bar{D}0 -> (V1V2)(V3V4) and psi(3770)->D0bar{D}0 -> (V1V2)(K pi)
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The charm quark offers interesting opportunities to cross-check the mechanism of CP violation precisely tested in the strange and beauty sectors. In this paper, we exploit the angular and quantum correlations in the Dbar{D} pairs produced through the decay of the psi(3770) resonance in a charm factory to investigate CP-violation in two different ways. We build CP-violating observables in psi(3770) -> Dbar{D} -> (V_1V_2)(V_3 V_4) to isolate specific New Physics effects in the charm sector. We also consider the case of psi(3770) -> Dbar{D} -> (V_1V_2)(Kpi) decays, which provide a new way to measure the strong phase difference delta between Cabibbo-favored and doubly-Cabibbo suppressed D decays required in the determination of the CKM angle gamma. Neglecting the systematics, we give a first rough estimate of the sensitivities of these measurements at BES-III with an integrated luminosity of 20 fb^-1 at psi(3770) peak and at a future Super tau-charm factory with a luminosity of 10^35 cm^-2.s^-1.
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We study $D^0overline{D}{}^0$ pairs produced in $e^+e^-$ collisions at $sqrt{s}=3.773$ GeV using a data sample of 2.92 fb$^{-1}$ collected with the BESIII detector. We measure the asymmetry $mathcal{A}^{CP}_{Kpi}$ of the branching fractions of $D to K^-pi^+$ in $CP$-odd and $CP$-even eigenstates to be $(12.7pm1.3pm0.7)times10^{-2}$. $mathcal{A}^{CP}_{Kpi}$ can be used to extract the strong phase difference $delta_{Kpi}$ between the doubly Cabibbo-suppressed process $overline{D}{}^{0}to K^-pi^+$ and the Cabibbo-favored process $D^0to K^- pi^+$. Using world-average values of external parameters, we obtain $cosdelta_{Kpi} = 1.02pm0.11pm0.06pm0.01$. Here, the first and second uncertainties are statistical and systematic, respectively, while the third uncertainty arises from the external parameters. This is the most precise measurement of $delta_{Kpi}$ to date.
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.
Several intermediate states of the reaction channels $e^{+}e^{-} rightarrow pi^{+} pi^{-} D^{0} bar{D}^{0}$ and $e^{+}e^{-} rightarrow pi^{+} pi^{-} D^{+}D^{-}$ are studied using the data samples collected with the BESIII detector at center-of-mass energies above 4.08 GeV. For the first time in this final state, a $psi(3770)$ signal is seen in the $Dbar{D}$ invariant mass spectrum, with a statistical significance of $5.2sigma$ at $sqrt{s} = 4.42$ GeV. There is also evidence for this resonance at $sqrt{s}$ = 4.26 and 4.36 GeV with statistical significance of 3.2$sigma$ and 3.3$sigma$, respectively. In addition, the Born cross section of $e^{+}e^{-}to pi^{+}pi^{-}psi(3770)$ is measured. The proposed heavy-quark-spin-symmetry partner of the $X(3872)$, the state $X_{2}(4013)$, is also searched for in the $Dbar{D}$ invariant mass spectra. No obvious signal is found. The upper limit of the Born cross section of the process $e^{+}e^{-}to rho^{0}X_{2}(4013)$ combined with the branching fraction is measured. Also, the processes $e^{+}e^{-}to D_{1}(2420)bar{D} + c.c.$ are investigated. The neutral mode with $D_{1}(2420)^{0}to D^{0}pi^{+}pi^{-}$ is reported with statistical significance of 7.4$sigma$ at $sqrt{s} = 4.42$ GeV for the first time, and evidence with statistical significance of 3.2$sigma$ and 3.3$sigma$ at $sqrt{s}$ = 4.36 and 4.60 GeV is seen, respectively. No evident signal for the process $e^{+}e^{-}to D_{1}(2420)^{0}bar{D}^{0} + c.c., D_{1}(2420)^{0}to D^{*+}pi^{-}$ is reported. Evidence for $e^{+}e^{-}to D_{1}(2420)^{+}D^{-} +~c.c., D_{1}(2420)^{+}to D^{+}pi^{+}pi^{-}$ is reported with statistical significance of 3.1$sigma$ and 3.0$sigma$ at $sqrt{s}$ = 4.36 and 4.42 GeV, respectively.
A search for time-dependent violation of the charge-parity symmetry in $D^0 to K^+ K^-$ and $D^0 to pi^+ pi^-$ decays is performed at the LHCb experiment using proton-proton collision data recorded from 2015 to 2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb$^{-1}$. The $D^0$ meson is required to originate from a $D^*(2010)^+ to D^0 pi^+$ decay, such that its flavour at production is identified by the charge of the accompanying pion. The slope of the time-dependent asymmetry of the decay rates of $D^0$ and $bar{D}^0$ mesons into the final states under consideration is measured to be $Delta Y_{K^+ K^-} = (-2.3 pm 1.5 pm 0.3) times 10^{-4}$, $Delta Y_{pi^+ pi^-} = (-4.0 pm 2.8 pm 0.4)times 10^{-4}$, where the first uncertainties are statistical and the second are systematic. These results are compatible with the conservation of the $CP$ symmetry at the level of 2 standard deviations and improve the precision by nearly a factor of two.
We search for CP violation in neutral charm meson decays using a data sample with an integrated luminosity of 966 fb^-1 collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. The asymmetry obtained in the rate of D^0 and D^0-bar decays to the pi^0 pi^0 final state, [-0.03+-0.64(stat)+-0.10(syst)]%, is consistent with no CP violation. This constitutes an order of magnitude improvement over the existing result. We also present an updated measurement of the CP asymmetry in the D^0 -> K_S pi^0 decay: A_{CP}(D^0 -> K_S pi^0) = [-0.21+-0.16(stat)+-0.07(syst)]%.
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