Experimental sensitivity on searching for CP violation at BES-Ⅲ

The CP violation in the D system is predicted to be an unobserved level in the Standard Model. In this paper, we describe the method of searching for CP violation decay processes with the coherently produced D^0D^0 mesons from the ψ（3770） decay. The CP violation decay processes can be searched for at the BES-Ⅲ experiment. The experimental sensitivity for searching for the CP violation can reach about a 10^-4 level with a ψ（3770） data sample of about 20 fb^-1.

Prospects of CP violation inΛdecay with a polarized electron beam at the STCF

Based on 1.89×10^(8) J/ψ→ΛΛ Monte Carlo(MC)events produced from a longitudinally-polarized electron beam,the sensitivity of the CP violation of A decay is studied using fast simulation software.In addition,the J/ψ→ΛΛ decay can be used to optimize the detector response using the interface provided by the fast simulation software.In the future,the STCF is expected to obtain 3.4 trillion J/ψevents,and the statistical sensitivity of the CP violation of A decay via the J/ψ→ΛΛ process is expected to reach O(10^(-5))when the electron beam polarization is 80%.

Exploring HVV amplitudes with CP violation using decomposition and the on-shell scattering amplitude method

CP violation may play an important role in baryogenesis in the early universe and should be examined comprehensively at colliders.We study the CP properties of HVV vertexes between Higgs and gauge boson pairs by defining a CP violation phase angle,which indicates the mixture of CP-even and CP-odd Higgs states in HVV in new physics.A series of HVV amplitudes,H→γγ,H-→V→γtt,and H→VV-→4f,with a CP phase angle are studied systematically to explicitly explain why CP violation can only be probed independently in the 4t pro-cess.We obtain a novel amplitude decomposition relation that illustrates that if two preconditions(multilinear mo-mentum dependent vertexes,and the current J_(μ) of V→l^(+)l^(-)is formally proportional to a photon's polarization vec-tor)are satisfied,a higher-point amplitude can be decomposed into a summation of a series of lower-point amp-litudes.As a practical example,the amplitude of the H→γV-→γtt and H→VV→4t processes can be decom-posed into a summation of many H→γγ amplitudes.We calculate these amplitudes in the framework of the on-shell scattering amplitude method,considering both massless and massive vector gauge bosons with the CP viola-tion phase angle.The above two approaches provide consistent results and clearly reveal the CP violation ξ depend-ence in the amplitudes.

Direct CP violation of three body decay processes from the resonance effect

The physical state of ρ−ω−φ mesons can be mixed using the unitary matrix.The decay processes ω→π^(+)π^(−)and φ→π^(+)π^(−)originate from isospin symmetry breaking.The ρ−ω,ρ−φ,and ω−φ interferences lead to a resonance contribution to produce strong phases.CP violation is considered from isospin symmetry breaking due to the new strong phase of the first order.CP violation can be enhanced greatly for the decay process B^(0)→π^(+)π^(−)η^((′))when the invariant masses of π^(+)π^(−) pairs are in the area around the ω resonance range and φ resonance range in perturbative QCD.We also discuss the possibility of searching for the predicted CP violation at the LHC.

D^0 -~0 mixing and CP violation at BES-Ⅲ

Recently, both BaBar and Belle experiments found evidences of neutral D mixing. In this paper, we discuss the sensitivities of the measurements of D mixing parameters at BES-Ⅲ. With CP tag technique at ψ（3770） peak, the extraction of the strong phase difference in D^0 → Kπ decay at BES-Ⅲ are discussed. We also make an estimate on the measurements of the mixing rate RM by using the coherent data at ψ（3770） peak. The CP violation in D system is predicted with an unobserved level in the Standard Model. Any significant CP violation in the D system indicates the existence of new physics. The sensitivity of the measurements of CP violation in the D system is estimated in the coherent D decays. Finally, the search for the rare D decays are discussed, in which some of the forbidden decays are smoking gun of new physics.

Feasibility study of CP violation inτ^(-)→Ksπ^(-)ντdecays at the Super Tau Charm Facility

We report a feasibility study for violation inτ^(-)→Ksπ^(-)ντdecays at a Super Tau Charm Facility(STCF).With an expected luminosity of 1 ab-1 collected by STCF per year at a center-of-mass energy of 4.26 GeV,the statistical sensitivity for CP violation is determined to be of order 9.7×10^(-4)by measuring the decay-rate differ-ence betweenτ^(+)→Ksπ^(+)ντandτ^(-)→Ksπ^(-)ντ.The analysis is performed using a reliable fast simulation software package,which can describe the detector responses properly and vary the responses flexibly for further optimization.Moreover,the energy-dependent efficiencies for reconstructingτ^(-)→Ksπ^(-)ντare presented.The expected CP sens-itivity is proportional to 1/T in the energy region from 4.0 to 5.0 GeV.The sensitivity of CP violation is of order 3.1×10^(-4)with 10 ab^(-1)integrated luminosity,which is equivalent to ten years'data taking in this energy region at STCF.

Broken S_(3L)×S_(3R) flavor symmetry and leptonic CP violation

In the framework of the canonical seesaw model,we present a simple but viable scenario to explicitly break an S3L×S3R flavor symmetry in the leptonic sector.It turns out that the leptonic flavor mixing matrix is completely determined by the mass ratios of the charged leptons（i.e.,me/mμand mμ/mτ） and those of light neutrinos（i.e.,m1/m2 and m2/m3）.The latest global-fit results of the three neutrino mixing angles {θ12,θ13,θ23}and two neutrino mass-squared differences {？m212,？m312} at the 3σ level are used to constrain the parameter space of {m1/m2,m2/m3}.The predictions for the mass spectrum and flavor mixing are highlighted：（1） the neutrino mass spectrum shows a hierarchical pattern and a normal ordering,e.g.,m1≈2.2meV,m2≈8.8 meV and m3≈52.7 meV;（2） only the first octant of θ23 is allowed,namely,41.8？ θ23 43.3？;（3） the Dirac C P-violating phase δ ≈-22？deviates significantly from the maximal value-90？.All these predictions are ready to be tested in ongoing and forthcoming neutrino oscillation experiments.Moreover,we demonstrate that the cosmological matter-antimatter asymmetry can be explained via resonant leptogenesis,including the individual lepton-flavor effects.In our scenario,leptonic C P violation at low-and high-energy scales is closely connected.

Measuring CP violation in rare W decays at the LHC

Heavy Majorana neutrinos beyond the standard model can simultaneously explain the origin of tiny neutRino masses and matter-antimatter asymmetry in our Universe.The existence of heavy Majorana neutrinos will also lead to lepton number violation and confirm the possibility of rare lepton-number-violating W decays.With contributions from two different Majorana neutrinos,nonzero CP asymmetry may be generated from the rate difference between W decay and its CP-conjugate process.The aim of this study is to investigate the prospects of measuring CP violation in rare w decays via Majorana neutRInos at the LHC.Our calculations show that the induced CP asymmetry is independent of the Majorana neutrino mass for 15<m_(N)<70GeV.Such a CP asymmetry,if observed,would in turn provide unambiguous evidence of new physics beyond the standard model.

Implications of the Daya Bay observation of θ_(13) on the leptonic flavor mixing structure and CP violation

The Daya Bay collaboration has recently reported its first νe → νe oscillation result which points to θ13 8.8 ± 0.8 （best-fit ±1σ range） or θ13 = 0 at the 5.2σ level. The fact that this smallest neutrino mixing angle is not strongly suppressed motivates us to look into the underlying structure of lepton flavor mixing and CP violation. Two phenomenological strategies are outlined： （1） the lepton flavor mixing matrix U consists of a constant leading term U0 and a small perturbation term U ; and （2） the mixing angles of U are associated with the lepton mass ratios. Some typical patterns of U0 are reexamined by constraining their respective perturbations with current experimental data. We illustrate a few possible ways to minimally correct U0 in order to fit the observed values of three mixing angles. We point out that the structure of U may exhibit an approximate μ-τ permutation symmetry in modulus, and reiterate the geometrical description of CP violation in terms of the leptonic unitarity triangles. The salient features of nine distinct parametrizations of U are summarized, and its Wolfenstein-like expansion is presented by taking U0 to be the democratic mixing pattern.

Dynamical CP violation of the generalized Yang-Mills model

Starting from the generalized Yang-Mills model which contains, besides the vector part Vμ, also a scalar part S and a pseudoscalar part P. It is shown, in terms of the Nambu-Jona-Lasinio （NJL） mechanism, that CP violation can be realized dynamically. The combination of the generalized Yang-Mills model and the NJL mechanism provides a new way to explain CP violation.

Measurement of strong phases, D-D mixing, and CP violation using quantum correlation at charm threshold

We review the measurements of the D decay strong-phase parameters based on quantum-correlated D^0D^-0 pairs produced in the e^＋e^→（3770） →D^0D^-0 process, and we discuss their role in the measurements of Cabibbo-Kobayashi-Maskawa angle 7 and D-/9 mixing. In addition, we present estimates of the size of quantum-correlated datasets necessary to support the 7 and charm mixing measurements conducted at the LHCb and Belle Ⅱ experiments. Finally, we review the methods for measuring the D-D^- mixing and cP violation parameters at a high-luminosity charm factory, giving sensitivity estimates.

Dynamical CP violation at finite temperature

By using the generalized Yang-Mills model, CP violation behavior at finite temperature is investigated, and it is shown that dynamical CP violation of the generalized Yang-Mills model at zero temperature can be restored at finite temperature.

Direct CP violation in hadronic B decays

There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on kT factorization, using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories.

Direct CP violation in B_(s) → J/ψP(V)

In the framework of factorization, we study direct CP violation in the decays of B（s） → J/φP（V） （P（V） refer to the pseudoscalar （vector） meson）. The CP violation depends strongly on Cabibbo-Kobayashi- Maskawa （CKM） matrix elements and the effective parameter, Nc. The recent experimental data for the branching ratios of B（s） → J/φP（V） are accurate enough and we can give a strong constraint on the range of Arc. We find that the CP violating asymmetry is consistent with the available experiment values for the b→ d transition, and a little smaller than the b→ s transition. We also predict the CP violation of other decay channels for B（s） → J/φP（V）. We expect our results can give valuable guidance for experiments.

Impact of a_(0)^(0)(980)-f_(0)(980) mixing on the localized CP violations of the B^(-)→K^(-)π^(+)(π)^(-) decay

In the framework of the QCD factorization approach,we study the localized CP violations of the B^(-)→K^(-)π^(+)(π)^(-)decay with and without the a_(0)^(0)(980)-f_(0)(980) mixing mechanism and observe that the localized CP violation can be enhanced by this mixing effect when the mass of the π^(+)(π)^(-)pair is in the vicinity of the f_(0)(980) resonance.The corresponding theoretical prediction results are A_(CP)(B^(-)→Kf_(0)→K^(-)π^(+)(π)^(-))=[0.126,0.338](0.232±0.106 with the central value form) and A_(CP)(B^(-)→K^(-)f_(0)(a_0)→K^(-)π^(+)(π)^(-))=[0.230,0.615](0.423±0.193 with the central value form),respectively.Meanwhile,we also calculate the branching fraction of the B^(-)→K^(-)f_(0)(980)→K^(-)π^(+)(π)^(-)decay,which is consistent with the experimental results.We suggest that the a_(0)^(0)(980)-f_(0)(980) mixing mechanism should be considered when theoretically and experimentally studying the CP violation of the B or D meson decays.

Studying the localized CP violation and the branching fraction of the B^0→K^-π^+π^+π^-decay

In this work,we study the localized CP violation and the branching fraction of the four-body decay^ˉB 0→K^−π^+π^−π^+by employing a quasi-two-body QCD factorization approach.Considering the interference of^ˉB 0→ˉK^∗0(700)ρ0(770)→K^−π^+π^−π^+and^ˉB 0→ˉK∗(892)f0(500)→K^−π^+π^−π^+channels,we predict ACP(^ˉB 0→K^−π^+π^−π^+)∈[0.15,0.28]and B(^ˉB 0→K^−π^+π^−π^+)∈[1.73,5.10]×10^−7,respectively,which shows that the interference mechanism of these two channels can induce the localized CP violation to this four-body decay.Meanwhile,within the two quark model framework for the scalar mesons f0(500)andˉK^∗0(700),we calculate the direct CP violations and branching fractions of the^ˉB 0→ˉK^∗0(700)ρ0(770)and^ˉB 0→ˉK∗(892)f0(500)decays,respectively.The corresponding results are ACP(^ˉB 0→ˉK^∗0(700)ρ0(770))∈[0.20,0.36],ACP(^ˉB 0→ˉK∗(892)f0(500))∈[0.08,0.12],B(^ˉB 0→ˉK^∗0(700)ρ0(770)∈[6.76,18.93]×10^−8 and B(^ˉB 0→ˉK∗(892)f0(500))∈[2.66,4.80]×10^−6,indicating that the CP violations of these two-body decays are both positive and the branching fractions quite different.These studies provide a new way to investigate the aforementioned four-body decay and can be helpful in clarifying the configuration of the structure of the light scalar meson.

Measurements of D^0-~0 mixing and searches for CP violation:HFAG combination of all data

We present world average values for D^0-D^0 mixing parameters x and y, CP violation parameters ｜q/P｜ and Arg（q/p）, and strong phase differences δ and δKππ. These values are calculated by the Heavy Flavor Averaging Group （HFAG） by performing a global fit to relevant experimental measurements. The results for x and y differ significantly from zero and are inconsistent with no mixing at the level of 6.7a. The results for ｜q/P｜ and Arg（q/p） are consistent with no CP violation. The strong phase difference δ is less than 45° at 95% C.L.

An overview of D^0-~0 mixing and CP violation

I give a brief overview of D^0-D^0 mixing and CP violation in the framework of the standard model. I focus on the theoretical estimate of the D^0-D^0 mixing parameters and the phenomenological description of several types of CP violation in neutral D-meson decays.

CP VIOLATION IN THE QUARK SECTOR

Revised February 2014 by T. Gershon （University of Warwick） and Y. Nir （Weizmann Institute）.

Constraining the UT angle γ by CP violation parameters in B^0→π^＋π^-

We calculate the tree and penguin amplitudes in the B^0→π^＋^-ecay channel employing the perturbative QCD factorization approach. Using the amplitudes as input with the theoretical uncertainties sufficiently considered, we constrain the UT angle γ to 53°γ 70°, from the measurements of the CP violation parameters C_（π^＋^- and S_（π^＋^-in B^0→π^＋^- The U-spin breaking effect between B^0→π^＋^-nd B^0 s →K^＋K^-is estimated to be around 30%.