Measurement Of Time-dependent CP Asymmetry Research Articles

A Review of CP Violation Measurements in Charm at LHCb

The LHCb experiment has been able to collect the largest sample ever produced of charm-hadron decays, performing a number of measurements of observables related to CP violation in the charm sector. In this document, the most recent results from LHCb on the search of direct CP violation in D0→Ks0Ks0, D(s)+→h+π0 and D(s)+→h+η decays are summarised, in addition to the most precise measurement of time-dependent CP asymmetry in D0→h+h− decays and the first observation of mass difference between neutral charm-meson eigenstates.

CP violation measurements in B mesons at Belle

We present recent measurements of time-dependent CP asymmetries in two neutral B decay modes: B0 → η'K0 and B0 → ωK°S. The measured values of mixing-induced (sin 2ϕ1eff) and direct CP violation parameters are: Sη'Ko = +0.68 ± 0.07stat ± 0.03syst, Aη'K0 = +0.03 ± 0.05stat ± 0.04syst and SωK0S = +0.91 ± 0.32stat ± 0.05syst, AωK0S = -0.36 ± 0.19stat ± 0.05syst, respectively. These results are fully consistent with the current world average of sin 2ϕ1 measured in b → cc̄s transitions, and represent the most accurate measurements in these modes up-to- date. In addition, we present a new preliminary update on branching ratio measurement in B0 → π0π0 decay mode, the result of which: ℬ(B0 → π0π0) = (0.90 ± 0.12stat ± 0.10syst) × 10−6 represents an important ingredient in a ππSU(2) isospin analysis, used to experimentally extract ϕ2 angle from B → ππ measurements. To obtain CP violation parameters (ℬ(B0 → π0π0)) the final data set of 772 × 106 (751.5 × 106) BB̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric e+e− collider in Japan (3.5 × 8.0GeV) is used.

Measurement of time-dependentCPasymmetry inB0→cc¯K(*)0decays

We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465+/-5) million Upsilon(4S)->BBbar decays collected with the Babar detector at the PEPII asymmetric energy e+e- storage rings operating at the SLAC National Accelerator Laboratory. The time-dependent CP asymmetry parameters measured from JpsiKs, JpsiKL, Psi(2S)Ks, Chi_c1Ks, eta_cKs and JpsiK*0 decays are: C_f = 0.024+/-0.020(stat)+/-0.016(syst) and -\eta_f S_f = 0.687+/-0.028(stat)+/-0.012(syst).

Measurements of time-dependentCPasymmetries inB0→D(*)+D(*)−decays

We present new measurements of time-dependent CP asymmetries for B0 --> D(*)+D(*)- decays using (467 +/- 5) X 10^6 BB pairs collected with the BaBar detector located at the PEP-II B Factory at the Stanford Linear Accelerator Center. We determine the CP-odd fraction of the B0 --> D*+D*- decays to be R_perp = 0.158 +/- 0.028 +/- 0.006 and find CP asymmetry parameters for the CP-even component of the decay S_+ = -0.76 +/- 0.16 +/- 0.04 and C_+ = 0.00 +/- 0.12 +/- 0.02. We measure S = -0.63 +/- 0.36 +/- 0.05 and C = -0.07 +/- 0.23 +/- 0.03 for B0 --> D+D-, S = -0.62 +/- 0.21 +/- 0.03 and C = 0.08 +/- 0.17 +/- 0.04 for B0 --> D*+D-$, and S = -0.73 +/- 0.23 +/- 0.05 and C = 0.00 +/- 0.17 +/- 0.03 for B0 --> D+D*-. For the B0 --> D*+/-D-/+ decays, we also determine the CP-violating asymmetry A = 0.008 +/- 0.048 +/- 0.013. In each case, the first uncertainty is statistical and the second is systematic. The measured values for the asymmetries are all consistent with the Standard Model.

Improved measurement of time-dependentCPasymmetries and theCP-odd fraction in the decayB0→D*+D*−

We present an updated measurement of the CP-odd fraction and the time-dependent CP asymmetries in the decay B0->D*+D*-using (383 +/- 4) \times 10^{6} BB pairs collected with the Babar detector. We determine the CP-odd fraction to be $0.143\pm0.034\stat\pm0.008\syst$. The time-dependent CP asymmetry parameters are determined to be $C_+ = -0.05\pm 0.14\stat \pm 0.02\syst$ and $S_+ = -0.72 \pm 0.19\stat \pm 0.05\syst$. The non-zero value of the measured $S_+$ indicates the evidence of CP violation at the $3.7 \sigma$ confidence level.

Measurements of time-dependentCPviolation inB0→ωKS0,f0(980)KS0,KS0π0andK+K−KS0decays

We present measurements of time-dependent CP asymmetries in $B^0 \to \omega K_S^0$, $f_0 (980) K_S^0$, $K_S^0 \pi^0$ and $K^+ K^- K_S^0$ based on a sample of 535 $\times 10^6$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. One neutral $B$ meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying $B$ meson is identified from its decay products. CP-violation parameters for each of the decay modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays.

Measurements of [formula omitted] in [formula omitted] and [formula omitted] Decays at B-Factories

Measurements of time-dependent CP asymmetries related to the extraction of the CKM-matrix parameter ϕ 1 / β are presented. Reported analyses, based on studies of neutral B-meson decays that proceed via b → c and b → s processes, were performed by Belle and BaBar collaborations.

Measurements of the CKM angle α/ϕ2 at the B Factories

We report measurements of time-dependent CP asymmetries related to the CKM angle $\beta/\phi_1$, using decays of neutral B mesons to charmonium, open charm and in $b\to s$ loop processes. A preliminary measurement of time-dependent CP asymmetries in $B^0\to \rho^0(770) K^0_S$ decays from the BaBar experiment is given here.

ϕ1/β Determination

Measurements of time-dependent CP asymmetries in B 0 → J / ψ K 0 and related b → c transitions provide precise measurements of sin 2 ϕ 1 . Time-dependent CP asymmetries in B 0 → ϕ K 0 and related b → s FCNC transitions also give sin 2 ϕ 1 to a good approximation within the Standard Model. Deviations from the Standard Model expectations would indicate a new source of CP violation. In this article, the present experimental results, as well as prospects for discoveries at LHC experiments and at SuperKEKB are summarized. In the end, several questions for discussions are raised.

Measurement of Time-DependentCPAsymmetries and theCP-Odd Fraction in the DecayB0→D*+D*−

We present an updated measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B0→D*+D*− using 232×106BB¯ pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the CP-odd fraction to be 0.125±0.044(stat)±0.007(syst). The time-dependent CP asymmetry parameters C+ and S+ are determined to be 0.06±0.17(stat)±0.03(syst) and −0.75±0.25(stat)±0.03(syst), respectively. The standard model predicts these parameters to be 0 and −sin2β, respectively, in the absence of penguin amplitude contributions.Received 30 June 2005DOI:https://doi.org/10.1103/PhysRevLett.95.151804©2005 American Physical Society

Results on the CKM Parameter [formula omitted] from the BaBar and Belle Experiments

This report presents a review of recent results for the determination of the parameter β ( ϕ 1 ) of the Cabibbo-Kobayashi-Maskawa matrix through the measurement of time-dependent CP asymmetries in B -meson decays by the BaBar and Belle experiments.

Effect of supersymmetric right-handed flavor mixing onBsdecays

Motivated by the possibility of ${\mathcal{S}}_{\ensuremath{\phi}{K}_{S}}<0$, we study the implications for the ${B}_{s}$ meson system. In a specific model that realizes ${\mathcal{S}}_{\ensuremath{\phi}{K}_{S}}<0$ with large $s\mathrm{\text{\ensuremath{-}}}b$ mixing, right-handed dynamics, and a new CP phase, we present predictions for CP asymmetries in ${B}_{s}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\phi}$, ${K}^{+}{K}^{\ensuremath{-}}$, and $\ensuremath{\phi}\ensuremath{\gamma}$ decays. Even if the measurement of time-dependent CP asymmetry becomes hampered by very fast ${B}_{s}$ oscillation, a finite difference between the decay rates of ${B}_{s}$ mass eigenstates may enable the studies of CP violations with untagged data samples. Thus, studies of CP violation in the ${B}_{s}$ system would remain useful for the extraction of new physics information.

Measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B0-->D(*+)D(*-).

We present a measurement of time-dependent CP asymmetries and an updated determination of the CP-odd fraction in the decay B0-->D(*+)D(*-) using a data sample of 88x10(6)BB pairs collected by the BABAR detector at the PEP-II B Factory at SLAC. We determine the CP-odd fraction to be 0.063+/-0.055(stat)+/-0.009(syst). The time-dependent CP asymmetry parameters Im(lambda(+)) and /lambda(+)/ are determined to be 0.05+/-0.29(stat)+/-0.10(syst) and 0.75+/-0.19(stat)+/-0.02(syst), respectively. The standard model predicts these parameters to be -sin(2beta and 1, respectively, in the absence of penguin diagram contributions.

Study of CP asymmetries in charmless hadronic B decays: Toward a measurement of α

We present preliminary measurements of time-dependent CP asymmetries in neutral B meson decays to π + π − and π + π − π 0 final states, where the latter is measured in the region of the Dalitz plane dominated by the ϱ resonance. We also present preliminary measurements of the branching fraction for the decay B + → π + π 0 and an improved upper limit for B 0 → π 0 π 0, both of which are needed to extract the CP parameter α from the time-dependent dependent CP asymmetry in the π + π − channel. These results are obtained from a data sample of approximately 88 million γ(4 S) → B B decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC.