CP Violation Parameter Research Articles

Study of Higgs-gauge boson anomalous couplings throughe−e+→W−W+hat the ILC

In this work, Higgs couplings with gauge bosons is probed through $e^-e^+ \rightarrow W^-W^+H$ in an effective Lagrangian framework. An ILC of 500 $GeV$ center of mass energy with possible beam polarization is considered for this purpose. The reach of ILC with integrated luminosity of 300 $fb^{-1}$ in the determination of both the CP-conserving and CP-violating parameters are obtained. Sensitivity of the probe of each of these couplings on the presence of other couplings is investigated. The most influential couplings parameters are $\bar c_W=-\bar c_B$. Other parameters of significant effect are $\bar c_{HW}$ and $\bar c_{HB}$ among the CP-conserving ones, and $\tilde c_{HW}$ and $\tilde c_{HB}$ among the CP-violating ones. CP-violating parameter, $\tilde c_\gamma$ seems to have very little influence on the process considered. Detailed study of the angular distributions have presented a way to disentangle the effect of some of these couplings.

Final state interaction phases obtained by data from CP asymmetries

Evidence of physics beyond the Standard Model (SM) of particle physics might be revealed through CP violation. Experimental results from BaBar, Belle, and most recently from LHCb are very interesting in this respect. It is important to calculate various CP violation parameters within the SM. In this Letter, the final state interaction (FSI) phases with the CKM matrix are calculated using the recent experimental results from LHCb on CP violation in B0 and Bs0 meson decays. To obtain the allowed regions of the FSI phases, a simplified form of the Jarlskog determinant of the CKM matrix is used and the CP phase delta close to the maximal value of pi/2 is found. Then, the asymmetry data on B0 and Bs0 from LHCb is used to explore graphically the allowed regions of the FSI phases.

Model independent determination of the CKM phase γ using input from D 0 ‐ D ¯ 0 $$ {D}^0\hbox{-} {\overline{D}}^0 $$ mixing

We present a new, amplitude model-independent method to measure the CP violation parameter γ in B − → DK − and related decays. Information on charm interference parameters, usually obtained from charm threshold data, is obtained from charm mixing. By splitting the phase space of the D meson decay into several bins, enough information can be gained to measure γ without input from the charm threshold. We demonstrate the feasibility of this approach with a simulation study of B − → DK − with D → K + π − π + π −. We compare the performance of our novel approach to that of a previously proposed binned analysis which uses charm interference parameters obtained from threshold data. While both methods provide useful constraints, the combination of the two by far outperforms either of them applied on their own. Such an analysis would provide a highly competitive measurement of γ. Our simulation studies indicate, subject to assumptions about data yields and the amplitude structure of D 0 → K + π − π + π −, a statistical uncertainty on γ of ~ 12° with existing data and ~ 4° for the LHCb-upgrade.

Exploring CP violation in the MSSM.

We explore the prospects for observing CP violation in the minimal supersymmetric extension of the Standard Model (MSSM) with six CP-violating parameters, three gaugino mass phases and three phases in trilinear soft supersymmetry-breaking parameters, using the CPsuperH code combined with a geometric approach to maximise CP-violating observables subject to the experimental upper bounds on electric dipole moments. We also implement CP-conserving constraints from Higgs physics, flavour physics and the upper limits on the cosmological dark matter density and spin-independent scattering. We study possible values of observables within the constrained MSSM (CMSSM), the non-universal Higgs model (NUHM), the CPX scenario and a variant of the phenomenological MSSM (pMSSM). We find values of the CP-violating asymmetry A_mathrm{CP} in b rightarrow s gamma decay that may be as large as 3 %, so future measurements of A_mathrm{CP} may provide independent information about CP violation in the MSSM. We find that CP-violating MSSM contributions to the B_s meson mass mixing term Delta M_{B_s} are in general below the present upper limit, which is dominated by theoretical uncertainties. If these could be reduced, Delta M_{B_s} could also provide an interesting and complementary constraint on the six CP-violating MSSM phases, enabling them all to be determined experimentally, in principle. We also find that CP violation in the h_{2,3} tau ^+ tau ^- and h_{2,3} {bar{t}} t couplings can be quite large, and so may offer interesting prospects for future pp, e^+ e^-, mu ^+ mu ^- and gamma gamma colliders.

The ESS Based Neutrino Super Beam for CP Violation Discovery

After measuring the last neutrino mixing angle θ13 and finding it relatively large, the observation of CP violation in the leptonic sector is now reachable with the condition to have significantly more intense neutrino beams than the existing ones. For this θ13 value, it came out that going to the second oscillation maximum instead of the first one, provides more sensitivity to CP violation. The European Spallation Source facility in Lund, designed to accelerate protons to 2.0GeV at a repetition rate of 14Hz for neutron production, could also be used to produce a copious number of neutrinos. Doubling the frequency of its proton linac opens the possibility to operate the facility simultaneously for neutron and neutrino production. An accumulator ring would be needed to shorten the pulses from 2.86ms for neutrons to few μs in order to reduce to acceptable levels the electric current sent to the magnetic horn focusing charged mesons to acceptable levels for the neutrino production. This accumulator could also be used by the neutron facility to increase its performance. Coupled with a megaton Water Cherenkov far detector placed at the optimal distance, this facility could efficiently exploite the second oscillation maximum to cover a large fraction of the CP violation parameter δCP at 5 σ confidence level.

Measurement of the directCP-violating parameterACPin the decayD+→K−π+π+

We measure the direct CP-violating parameter A_CP for the decay of the charged charm meson, D+ -> K-pi+pi+ (and charge conjugate), using the full 10.4 fb-1 sample of ppbar collisions at sqrt(s) = 1.96 TeV collected by the D0 detector at the Fermilab Tevatron collider. We extract the raw reconstructed charge asymmetry by fitting the invariant mass distributions for the sum and difference of charge-specific samples. This quantity is then corrected for detector-related asymmetries using data-driven methods and for possible physics asymmetries (from B -> D processes) using input from Monte Carlo simulation. We measure A_CP = [-0.16 +- 0.15 (stat.) +- 0.09 (syst.)]%, which is consistent with zero, as expected from the standard model prediction of CP conservation, and is the most precise measurement of this quantity to date

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.

Charm CP violation and mixing at Belle

We present charm CP violation and mixing measurements at Belle. They are the first observation of D0 − D̄0 mixing in e+e− collisions from D0 → K+π− decays, the most precise mixing and indirect CP violation parameters from D0 → K0Sπ+π− decays, and the timeintegrated CP asymmetries in D0 → π0π0 and D0 → K0Sπ0 decays. Our mixing measurement in D0 → K+π− decays excludes the no-mixing hypothesis at the 5.1 standard deviation level. The mixing parameters x = (0.56 ± 0.19+0.03+0.06−0.09−0.09)%, y = (0.30 ± 0.15+0.04+0.03−0.05−0.06)% and indirect CP violation parameters |q/p| = (0.90+0.16+0.05+0.06−0.15−0.04−0.05)%, arg(q/p) = (−6 ± 11 ± 3+3−4)° measured from D0 → K0Sπ+π− decays, and the time-integrated CP asymmetries AD0→π0π0CP = (−0.03 ± 0.64 ± 0.10)% and AD0→K0Sπ0CP = (−0.21 ± 0.16 ± 0.07)% are the most precisemeasurements to date. Our measurements here are consistent with predictions of the standard model.

Weak interactions of kaons from lattice QCD

The methods of lattice QCD and available computer resources are now sufficient that predictions for many of the Standard Model properties of kaons can be made from first principles with accurately bounded uncertainties. We discuss two relatively new areas where lattice methods are having or will soon have a large impact: calculation of the two complex amplitudes A0 and A2 describing the decay of the kaon into two-pions with I = 0 and 2 and calculation of long-distance contributions to second-order electro-weak processes including the KL – KS mass difference ΔMK, the CP-violating parameter ϵK and certain rare kaon decays.

Baryogenesis from strong CP violation and the QCD axion.

We show that strong CP violation from the QCD axion can be responsible for the matter antimatter asymmetry of the Universe in the context of cold electroweak baryogenesis if the electroweak phase transition is delayed below the GeV scale. This can occur naturally if the Higgs couples to a O(100) GeV dilaton, as expected in some models where the Higgs is a pseudo-Nambu-Goldstone boson of a new strongly interacting sector at the TeV scale. The existence of such a second scalar resonance with a mass and properties similar to the Higgs boson will soon be tested at the LHC. In this context, the QCD axion would not only solve the strong CP problem, but also the matter antimatter asymmetry and dark matter.

Coherent flavour oscillation and CP violating parameter in thermal resonant leptogenesis

Solving the Kadanoff-Baym (KB) equations in a different method from our previous analysis, we obtain the CP violating parameter $\varepsilon$ in the thermal resonant leptogenesis without assuming smallness of the off-diagonal Yukawa couplings. For that purpose, we first derive a kinetic equation for density matrix of RH neutrinos with almost degenerate masses $M_i \ (i=1,2) \sim M$. If the deviation from thermal equilibrium is small, the differential equation is reduced to a linear algebraic equation and the density matrix can be solved explicitly in terms of the time variation of (local) equilibrium distribution function. The obtained CP-violating parameter $\varepsilon_i$ is proportional to an enhancement factor $(M^{2}_{i}-M^{2}_{j}) M_i \Gamma_j/ ((M^{2}_{i}-M^{2}_{j})^2 +R_{ij}^2)$ with a regulator $R_{ij}=M (\Gamma_i + \Gamma_j)$, consistent with the previous analysis. The decay width can be determined systematically by the 1PI self-energy of the RH neutrinos in the 2PI formalism.

Nucleon electric dipole moments and the isovector parity- and time-reversal-odd pion–nucleon coupling

The isovector time-reversal- and parity-violating pion–nucleon coupling g¯π(1) is uniquely sensitive to dimension-six interactions between right-handed light quarks and the Standard Model Higgs doublet that naturally arises in left-right symmetric models. Recent work has used the g¯π(1)-induced one-loop contribution to the neutron electric dipole moment dn, together with the present experimental dn bound, to constrain the CP-violating parameters of the left-right symmetric model. We show that this and related analyses are based on an earlier meson theory dn computation that is not consistent with the power-counting appropriate for an effective field theory. We repeat the one-loop calculation using heavy baryon chiral perturbation theory and find that the resulting dn sensitivity to g¯π(1) is suppressed, implying more relaxed constraints on the parameter space of the left-right symmetric model. Assuming no cancellations between this loop contribution and other contributions, such as the leading order EDM low-energy constant, the present limit on dn implies |g¯π(1)|≲1.1×10−10.

Present and futureKandBmeson mixing constraints on TeV scale left-right symmetry

We revisit the $\Delta F=2$ transitions in the $K$ and $B_{d,s}$ neutral meson systems in the context of the minimal Left-Right symmetric model. We take into account, in addition to up-to-date phenomenological data, the contributions related to the renormalization of the flavor-changing neutral Higgs tree-level amplitude. These contributions were neglected in recent discussions, albeit formally needed in order to obtain a gauge independent result. Their impact on the minimal LR model is crucial and twofold. First, the effects are relevant in $B$ meson oscillations, for both CP conserving and CP violating observables, so that for the first time these imply constraints on the LR scenario which compete with those of the $K$ sector (plagued by long-distance uncertainties). Second, they sizably contribute to the indirect kaon CP violation parameter $\varepsilon$. We discuss the bounds from $B$ and $K$ mesons in both cases of LR symmetry: generalized parity ($\mathcal P$) and charge conjugation ($\mathcal C$). In the case of $\mathcal P$, the interplay between the CP-violation parameters $\varepsilon$ and $\varepsilon'$ leads us to rule out the regime of very hierarchical bidoublet vacuum expectation values $v_2/v_1<m_b/m_t\simeq 0.02$. In general, by minimizing the scalar field contribution up to the limit of the perturbative regime and by definite values of the relevant CP phases in the charged right-handed currents, we find that a right-handed gauge boson $W_R$ as light as 3 TeV is allowed at the 95% CL. This is well within the reach of direct detection at the next LHC run. If not discovered, within a decade the upgraded LHCb and Super B factories may reach an indirect sensitivity to a Left-Right scale of 8 TeV.

Technique to observe directCPviolation inDmesons using Bose symmetry and the Dalitz plot

We present a new and sensitive method to observe direct CP violation in $D$ mesons using Bose symmetry and Dalitz plot. We apply the method to processes such as $B \to D^0\bar{D}^0 P$, where $P$ is either a $K$ or a $\pi$. By choosing to reconstruct $D$ mesons only through their decays into CP eigenstates, we show that any asymmetry in the Dalitz plot can arise only through direct CP violation. We further show how CP violation parameters can be determined. Since the approach involves only Bose symmetry, the method is applicable to any multi-body process that involves $D^0\bar{D}^0$ in the final state. We briefly discuss how $B\to D^* \bar{D}^* P$ can also be used in a similar way.

Study on the Neutrino Oscillation with a Next Generation Medium-Baseline Reactor Experiment

For over fifty years, reactor experiments have played an important role in neutrino physics, in both discoveries and precision measurements. One of the methods to verify the existence of neutrino is the observation of neutrino oscillation phenomena. Electron antineutrinos emitted from a reactor provide the measurement of the small mixing angleθ13, providing rich programs of neutrino properties, detector development, nuclear monitoring, and application. Using reactor neutrinos, future reactor neutrino experiments, more precise measurements ofθ12, Δm122, and mass hierarchy will be explored. The precise measurement ofθ13would be crucial for measuring the CP violation parameters at accelerators. Therefore, reactor neutrino physics will assist in the complete understanding of the fundamental nature and implications of neutrino masses and mixing. In this paper, we investigated several characteristics of RENO-50, which is a future medium-baseline reactor neutrino oscillation experiment, by using the GloBES simulation package.

Evidence for the suppressed decayB−→DK−,D→K+π−π0

We report a study of the suppressed decay B^- -> DK^-, D -> K^+\pi^-\pi^0, where D denotes either a D^0 or a \bar{D}^0 meson. The decay is sensitive to the CP-violating parameter \phi_3. Using a data sample of 772 x 10^6 B\bar{B} pairs collected at the \Upsilon(4S) resonance with the Belle detector, we measure the ratio of branching fractions of the above suppressed decay to the favored decay B^- -> DK^-, D -> K^-\pi^+\pi^0. Our result is R_{DK} = [1.98 +/- 0.62(stat.) +/- 0.24(syst.)] x 10^{-2}, which indicates the first evidence of the signal for this suppressed decay with a significance of 3.2 standard deviations. We measure the direct CP asymmetry between the suppressed B^- and B^+ decays to be A_{DK} = 0.41 +/- 0.30 (stat.) +/- 0.05 (syst.). We also report measurements for the analogous quantities R_{D\pi} and A_{D\pi} for the decay B^- -> D\pi^-, D -> K^+\pi^-\pi^0.

The string origin of SUSY flavor violation

We argue that in large classes of string compactifications with a MSSM-like structure substantial flavor violating SUSY-breaking soft terms are generically induced. We specify to the case of flavor dependent soft-terms in type IIB/F-theory SU(5) unified models, although our results can be easily extended to other settings. The Standard Model (SM) degrees of freedom reside in a local system of 7-branes wrapping a 4-fold S in the extra dimensions. It is known that in the presence of closed string 3-form fluxes SUSY-breaking terms are typically generated. We explore the generation dependence of these soft terms and find that non-universalities arise whenever the flux varies over the 4-fold S. These non-universalities are parametrically suppressed by (M GUT /M Pl)1/3. They also arise in the case of varying open string fluxes, in this case parametrically suppressed by $ \alpha_{\mathrm{GUT}}^{{{1 \left/ {2} \right.}}} $ . For a standard unification scheme with M GUT ≃ 1016 GeV and α GUT ≃ 1/24 these suppressions are very mild. Although limits from the kaon mass difference Δm K are easily obeyed for squark masses above the present LHC limits, constraints from the CP-violation parameter ϵ K imply squark masses in the multi-TeV region. The constraints from BR(μ → eγ) turn out to be the strongest ones, with slepton masses of order ~ 10 TeV or heavier required to obey the experimental limits. These sfermion masses are consistent with the observed large value m H ≃ 126 GeV of the Higgs mass. We discuss under what conditions such strong limits may be relaxed allowing for SUSY particle production at LHC.

Time-dependentCPviolations ofB(Bs)decays in the perturbative QCD approach

We study the decay modes of ${B}_{s}^{0}({\overline{B}}_{s}^{0})\ensuremath{\rightarrow}{D}_{s}^{\ifmmode\pm\else\textpm\fi{}}{K}^{\ensuremath{\mp}}$, ${B}_{s}^{0}({\overline{B}}_{s}^{0})\ensuremath{\rightarrow}{D}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$, and ${B}^{0}({\overline{B}}^{0})\ensuremath{\rightarrow}{D}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ in the perturbative QCD approach based on ${k}_{T}$ factorization, including the branching ratios and $CP$ violation parameters which provide a clear way to extract the Cabibbo-Kobayashi-Maskawa angle $\ensuremath{\gamma}$. Our results of branching ratios of ${B}_{s}^{0}({\overline{B}}_{s}^{0})\ensuremath{\rightarrow}{D}_{s}^{\ifmmode\pm\else\textpm\fi{}}{K}^{\ensuremath{\mp}}$ and ${B}^{0}({\overline{B}}^{0})\ensuremath{\rightarrow}{D}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and the $CP$ asymmetry of ${B}^{0}({\overline{B}}^{0})\ensuremath{\rightarrow}{D}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ agree well with the experimental data. We also give predictions of the other observables, which provide some guidance for experiments in the future, especially for the LHCb experiment.

Enhanced CP violation in D 0→ρ 0(ω)ρ 0(ω)→π + π − π + π −

In the factorization approach we study the direct CP violation in D0→ρ0(ω)ρ0(ω)→π+π−π+π− (with unpolarized ρ0(ω)) via the ρ−ω mixing mechanism. We find that the CP violation can be enhanced due to a large strong phase difference when the masses of the π+π− pairs are in the vicinity of the ω resonance. The CP violation parameter depends on the effective parameter Nc which includes nonfactorizable effects and is determined by the experimental data. Taking into account double ρ−ω mixing contributions, we find the CP violating asymmetry is larger than these in the cases where no ρ−ω mixing or single ρ−ω mixing is taken into account. We also discuss the possibility to observe the predicted CP violation at BEPCII.

Recent Charm Physics Results from BaBar

I present recent results from the BaBar experiment based on a data sample corresponding to an integrated luminosity of about 480 fb−1 collected at the PEP-II asymmetric energy e+e− collider. In particular, I will discuss the search for CP violation in D+→Ks0K+ and Ds+→Ks0K+,Ks0π+ decays, and in three-body D+→K+K−π+ decays. I will report on the measurement of the mixing parameter yCP and of the CP-violation parameter ΔY, in the lifetime ratio analysis of the transitions to the CP-even eigenstates D0→K+K−,π+π−, relative to the transitions to the CP-mixed state D0→K−π+, where we obtain yCP=[0.72±0.18(stat)±0.12(syst)]% and ΔY=[0.09±0.26(stat)±0.06(syst)]%. Finally, I will present a precision measurement of the D⁎(2010)+ total width, Γ=83.5±1.7(stat)±1.2(syst) keV, and of the D⁎(2010)+−D0 mass difference, Δm=145426.5±0.4(stat)±2.6(syst) keV.