Study CP Violation Research Articles

First determination of the CP content of D → π+π−π+π− and updated determination of the CP contents of D → π+π−π0 and D → K+K−π0

Quantum-correlated ψ(3770)→DD‾ decays collected by the CLEO-c experiment are used to perform a first measurement of F+4π, the fractional CP-even content of the self-conjugate decay D→π+π−π+π−, obtaining a value of 0.737±0.028. An important input to the measurement comes from the use of D→KS0π+π− and D→KL0π+π− decays to tag the signal mode. This same technique is applied to the channels D→π+π−π0 and D→K+K−π0, yielding F+πππ0=1.014±0.045±0.022 and F+KKπ0=0.734±0.106±0.054, where the first uncertainty is statistical and the second systematic. These measurements are consistent with those of an earlier analysis, based on CP-eigenstate tags, and can be combined to give values of F+πππ0=0.973±0.017 and F+KKπ0=0.732±0.055. The results will enable the three modes to be included in a model-independent manner in measurements of the unitarity triangle angle γ using B∓→DK∓ decays, and in time-dependent studies of CP violation and mixing in the D0D‾0 system.

The discovery reach of CP violation in neutrino oscillation with non-standard interaction effects

We have studied the CP violation discovery reach in a neutrino oscillation experiment with superbeam, neutrino factory and monoenergetic neutrino beam from the electron capture process. For NSI satisfying model-dependent bound for shorter baselines (like CERN-Fréjus set-up) there is insignificant effect of NSI on the the discovery reach of CP violation due to δ. Particularly, for the superbeam and neutrino factory we have also considered relatively longer baselines for which there could be significant NSI effects on CP violation discovery reach for higher allowed values of NSI. For the monoenergetic beam only shorter baselines are considered to study CP violation with different nuclei as neutrino sources. Interestingly for non-standard interactions— and of neutrinos with matter during propagation in longer baselines in the superbeam, there is the possibility of better discovery reach of CP violation than that with only Standard Model interactions of neutrinos with matter. For complex NSI we have shown the CP violation discovery reach in the plane of Dirac phase δ and NSI phase . The CP violation due to some values of δ remain unobservable with present and near future experimental facilities in the superbeam and neutrino factory. However, in the presence of some ranges of off-diagonal NSI phase values there are some possibilities of discovering total CP violation for any value even at confidence level for neutrino factory. Our analysis indicates that for some values of NSI phases total CP violation may not be at all observable for any values of δ. Combination of shorter and longer baselines could indicate in some cases the presence of NSI. However, in general for NSIs the CP violation discovery reach is better in neutrino factory set-ups. Using a neutrino beam from the electron capture process for nuclei Sn and 152Yb, we have shown the discovery reach of CP violation in a neutrino oscillation experiment. Particularly for Sn nuclei CP violation could be found for about 51% of the possible δ values for a baseline of 130 km with boost factor . Although the nuclei 152Yb is technically more feasible for the production of a mono-energetic beam, it is found to be unsuitable in obtaining good discovery reach of CP violation.

Angular analysis and CP violation studies in B decays at CMS

Angular distributions of the decay B0 → K*0μ+μ− are a clean probe of physics beyond the standard model. In particular the forward-backward asymmetry and other variables which can be determined as a function of q2 provide fruitful information from a single decay channel. An angular and proper decay time analysis is applied to the Bs → J/ψϕ decays. The Bs signal candidates are reconstructed and used to extract the mixing phase ϕs. The theoretical prediction of the ϕs angle is particularly robust, thus any deviation from the prediction can be a smoking gun signal of new physics.

Towards new frontiers in CP violation in B decays

CP-violating effects in decays of B mesons offer a wide spectrum of probes for testing the phase structure of the quark-flavour sector of the Standard Model. After a brief discussion of the picture emerging from the current LHC data, the focus will be put on two specific topics: hadronic uncertainties from penguin topologies on measurements of the B0q-B̄0q mixing phases (q ∊ {d,s}), and the U-spin-related decays B0s → K+K− and B0d → π+π−. Valuable new insights are expected from future studies of CP violation in B decays. For the detection of possible new sources of CP violation, it will be crucial to match the experimental and theoretical precisions and to have a careful look at the underlying assumptions.

Measurement of CP violation in the B0s system

Studies of CP violation play a key role in the search for physics beyond the Standard Model. In the B0s system these mainly consist of measurements of mixing-induced CP violation, which arises from the interference between the B0s−B̄0s mixing process and the subsequent decay. This report focusses on two such asymmetry measurements recently published by the LHCb collaboration. The first analysis presents the measurement of a CP violating phase in B0s → φφ, which is found to be φφφ = −0.17±0.15(stat)±0.03(syst)rad. The second provides an updated measurement of the B0s−B̄0s mixing phase φs using the B0s → J/ψπ+π− channel. It yields φs = 0.070 ± 0.068 (stat) ± 0.008 (syst) rad. Both results are consistent with the Standard Model expectations and no indication for direct CP violation was found in either decay mode.

CKM angle γ measurements at LHCb

The CKM angle γ remains the least known parameter of the CKM mixing matrix. The precise measurement of this angle, as a Standard Model benchmark, is a key goal of the LHCb experiment. We present four recent CP violation studies related to the measurement of γ, including amplitude analysis of B± → DK± decays, the ADS/GLW analysis of B± → DK*0 decays and the time-dependent analysis of B± → DK±sK± decays.

New results from the T2K experiment

Since its discovery, neutrino oscillation has been the subject of intense research. The θ13 parameter of the neutrino mixing matrix is of particular importance. A non-zero θ13 opens the possibility to study CP violation in the neutrino sector which could help explain the matter anti-matter asymmetry in the Universe. The Tokai-To-Kamioka (T2K) experiment was designed to measure electron neutrino appearance and muon neutrino disappearance using a muon neutrino beam produced at the J-PARC facility in Tokai, Japan. The Super-Kamiokande detector, located 295 km from the neutrino source, acts as the far detector. An improved analysis and all the data taken through June 9, 2012 provide 11 electron neutrino candidates in the far detector corresponding to 3.1 standard deviations from the θ13=0 hypothesis. This excess is currently the strongest indication of electron neutrino appearance and it yields for normal hierarchy and δCP=0, 0.053<sin2⁡2θ13<0.141 at 68% confidence level.

A study of CP violation in B± → DK± and B± → Dπ± decays with [formula omitted] final states

A first study of CP violation in the decay modes B±→[KS0K±π∓]Dh± and B±→[KS0K∓π±]Dh±, where h labels a K or π meson and D labels a D0 or D‾0 meson, is performed. The analysis uses the LHCb data set collected in pp collisions, corresponding to an integrated luminosity of 3 fb−1. The analysis is sensitive to the CP-violating CKM phase γ through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of γ using other decay modes.

Neutrino super beam based on a superconducting proton linac

We present a new design study of the neutrino Super Beam based on the Superconducting Proton Linac at CERN. This beam is aimed at megaton mass physics, a large water Cherenkov detector, proposed for the Laboratoire Souterrain de Modane in France, with a baseline of 130 km. The aim of this proposed facility is to study CP violation in the neutrino sector. In the study reported here, we have developed the conceptual design of the neutrino beam, especially the target and the magnetic focusing device. Indeed, this beam presents several unprecedented challenges, related to the high primary proton beam power (4 MW), the high repetition rate (50 Hz), and the low kinetic energy of the protons (4.5 GeV). The design is completed by a study of all the main components of the system, starting from the transport system to guide the beam to the target up to the beam dump. This is the first complete study of a neutrino beam based on a pebble-bed target capable of standing the large heat deposition of MW class proton beams.24 MoreReceived 5 December 2012DOI:https://doi.org/10.1103/PhysRevSTAB.17.031001This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical Society

Discovery reach of CP violation in neutrino oscillation experiments with standard and non-standard interactions

Considering the value of mixing angle θ13 as obtained in recent Daya Bay and MINOS experiments we have explored the discovery reach of CP violation in the leptonic sector due to complex δ phase in neutrino oscillation experiments with superbeam. We have considered two experimental set-up corresponding to two baselines of 130 Km and 2300 Km respectively. Considering numerical simulation we have shown how the discovery reach of CP violation will change due to the presence of various non-standard interactions (NSIs). Although it is known that short baseline is better choice for CP violation study for Standard Model (SM) interactions of neutrinos with matter but in presence of NSI we find that sometimes better discovery reach is possible in relatively longer baselines.

Effects of $ {K^0}-{{\overline{K}}^0} $ mixing on determining γ from B ± → DK ±

The decay $B^{\pm}\to DK^{\pm}$ followed by the subsequent decay of the $D$ meson into final states involving a neutral kaon can be used to determine the CKM angle $\gamma$. We study CP violation effects due to mixing and decay of the final state kaon. We find that ignoring these effects produce a shift in $\gamma$ of order $\epsilon_{K}/r_{B}$, an enhancement of $1/r_B$ compared to the naive expectation. We then show how to take these effects into account such that, in principle, they will not introduce any theoretical error in the extraction of $\gamma$.

Searching for the squark flavor mixing in CP violations of Bs -&gt; K+ K- and K0 K0 decays

We study CP violations in the B_s-> K+K- and Bs->K0K0 decays in order to find the contribution of the supersymmetry, which comes from the gluino-squark mediated flavor changing current. We obtain the allowed region of the squark flavor mixing parameters by putting the experimental data, the mass difference Delta M_Bs, the CP violating phase phi_s in Bs to J/psi phi decay and the b to s gamma branching ratio. In addition to these data, we take into account the constraint from the asymmetry of B0->K+pi because the Bs->K+K- decay is related with the B0->K+pi- decay by replacing the spectator s with d. Under these constraints, we predict the magnitudes of the CP violation in the Bs->K+K- and Bs->K0K0 decays. The predicted region of the CP violation C_{K+K-} is strongly cut from the direct CP violation of barB0 to K-pi+, therefore, the deviation from the SM prediction of C_{K+K-} is not found. On the other hand, the CP violation S_{K+K-} is possibly deviated from the SM prediction considerably, in the region of 0.1- 0.5. Since the standard model predictions of C_{K0bar K0} and S_{K0bar K0} are very small, the squark contribution can be detectable in C_{K0bar K0} and S_{K0bar K0}. These magnitudes are expected in the region C_{K0bar K0}=-0.06-0.06 and S_{K0bar K0}=-0.5-0.3. More precise data of these CP violations provide us a crucial test for the gluino-squark mediated flavor changing current.

Measurements of IndirectCPAsymmetries inD0→K−K+andD0→π−π+Decays

A study of indirect CP violation in $D^0$ mesons through the determination of the parameter $A_\Gamma$ is presented using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected with the LHCb detector and recorded at the centre-of-mass energy of 7 TeV at the LHC. The parameter $A_\Gamma$ is the asymmetry of the effective lifetimes measured in decays of $D^0$ and $\bar{D}^0$ mesons to the CP eigenstates $K^-K^+$ and $\pi^-\pi^+$. Fits to the data sample yield $A_\Gamma(KK)=(-0.35\pm0.62\pm0.12)\times 10^{-3}$ and $A_\Gamma(\pi\pi)=(0.33\pm1.06\pm0.14)\times 10^{-3}$, where the first uncertainties are statistical and the second systematic. The results represent the world's best measurements of these quantities. They show no difference in $A_\Gamma$ between the two final states and no indication of CP violation.

CPandCPTviolating parameters determined from the joint decays ofC=+1entangled neutral pseudoscalar mesons

Entangled pseudoscalar neutral meson pairs have been used in studying CP violation and searching CPT violation, but almost all the previous works concern $C=-1$ entangled state. Here we consider $C=+1$ entangled state of pseudoscalar neutral mesons, which is quite different from $C=-1$ entangled state and provides complementary information on symmetry violating parameters. After developing a general formalism, we consider three kinds of decay processes, namely, semileptonic-semileptonic, hadronic-hadronic and semileptonic-hadronic processes. For each kind of processes, we calculate the integrated rates of joint decays with a fixed time interval, as well as asymmetries defined for these joint rates of different channels. In turn, these asymmetries can be used to determine the four real numbers of the two indirect symmetry violating parameters, based on a general relation between the symmetry violating parameters and the decay asymmetries presented here. Various discussions are made on indirect and direct violations and the violation of $\Delta {\cal F} =\Delta Q$ rule, with some results presented as theorems.

Mixing and CP violation in the beauty and charm sectors at LHCb

The LHCb detector is a dedicated heavy flavour experiment operating at the Large Hadron Collider designed to pursue an extensive study of CP violation in the beauty and charm sectors. In the first part of this contribution, important milestones towards the measurement of CP violation in the beauty sector using B ± and B 0 s decays are presented. In the second part, highlights of the searches of CP violation in the charm sector are reported.

MajoranaCP-violating phases in neutrino-antineutrino oscillations and other lepton-number-violating processes

If the massive neutrinos are identified to be the Majorana particles via a convincing measurement of the neutrinoless double beta (0\nu\beta\beta) decay, how to determine the Majorana CP-violating phases in the 3 x 3 lepton flavor mixing matrix U will become a desirable experimental question. The answer to this question is to explore all the possible lepton-number-violating (LNV) processes in which the Majorana phases really matter. In this paper we carry out a systematic study of CP violation in neutrino-antineutrino oscillations, whose CP-conserving parts involve six independent 0\nu\beta\beta-like mass terms <m>_{\alpha\beta} and CP-violating parts are associated with nine independent Jarlskog-like parameters V^{ij}_{\alpha\beta} (for \alpha, \beta = e, \mu, \tau and i, j = 1, 2,3). With the help of current neutrino oscillation data, we analyze the sensitivities of |<m>_{\alpha\beta}| and V^{ij}_{\alpha\beta} to the three CP-violating phases of U, and illustrate the salient features of six independent CP-violating asymmetries between \nu_\alpha \to \bar{\nu}_\beta and \bar{\nu}_\alpha \to \nu_\beta oscillations. As a by-product, the effects of the CP-violating phases on the LNV decays of doubly- and singly-charged Higgs bosons are reexamined by taking account of the unsuppressed value of \theta_{13}. Such CP-conserving LNV processes can be complementary to the possible measurements of neutrino-antineutrino oscillations in the distant future.

CP violation at the B factories

One of the primary goals of the B factory experiments was to measure and study CP violation in B meson decays, a goal which has been met very successfully. This paper reports on recent measurements of CP violation at the Babar and Belle experiments. Particular focus is placed on the measurements of the three angles of the Unitarity Triangle, β, α and γ.

CP violation and mass hierarchy at medium baselines in the large θ 13 era

The large value of theta(13) recently measured by rector and accelerator experiments opens unprecedented opportunities for precision oscillation physics. In this paper, we reconsider the physics reach of medium baseline superbeams. For theta(13) ~ 9 degree we show that facilities at medium baselines -- i.e. L ~ O(1000 km) -- remain optimal for the study of CP violation in the leptonic sector, although their ultimate precision strongly depends on experimental systematics. This is demonstrated in particular for facilities of practical interest in Europe: a CERN to Gran Sasso and CERN to Phyasalmi nu_mu beam based on the present SPS and on new high power 50 GeV proton driver. Due to the large value of theta(13), spectral information can be employed at medium baselines to resolve the sign ambiguity and determine the neutrino mass hierarchy. However, longer baselines, where matter effects dominate the nu_mu->nu_e transition, can achieve much stronger sensitivity to sign(Delta m^2) even at moderate exposures.

Analysis of the resonant components inB¯0→J/ψπ+π−

Interpretation of CP violation measurements using charmonium decays, in both the B0 and Bs systems, can be subject to changes due to "penguin" type diagrams. These effects can be investigated using measurements of the Cabibbo-suppressed B0->J/\psi pi+pi- decays. The final state composition of this channel is investigated using a 1.0/fb sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz plot analysis is performed using both the invariant mass spectra and the decay angular distributions. An improved measurement of the B0->J/\psi pi+pi- branching fraction of (3.97 +/-0.09+/- 0.11 +/- 0.16)x10^{-5} is reported where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainty of the branching fraction of the decay B- -> J/\psi K- used as a normalization channel. In the J/\psi pi+pi- final state significant production of f0(500) and rho(770) resonances is found, both of which can be used for CP violation studies. In contrast evidence for the f0(980) resonance is not found, thus establishing the first upper limit on the branching fraction product B(B0->J/\psi f0(980) x B(f0(980)-> pi+ pi-) < 1.1x10^{-6}, leading to an upper limit on the absolute value of the mixing angle of the f0(980)$ with the f0(500) of <31 degrees, both at 90% confidence level.

Experimental Prospect

This is the first conference of this series the three of the lepton mixing angles are known. The non-zero value of the third mixing angle (θ13) has been reported by νe appearance in accelerator νμ beam and by ν¯e disappearance in reactor experiments. The observation of the νe appearance in νμ beam is the first clear evidence of the flavor oscillations. The results also show that neutrino oscillations phenomena can be described by three-generation scheme to the first approximation, where mixing of neutrinos can be described by three angles and one complex phase. There are two main issues to be investigated by neutrino oscillation experiments. One is the study of CP violation in lepton secto. Namely, the measurement of CP violating complex phase δCP and the studies of the nature of CP violation phenomena in lepton sector. The other is search for neutrinos beyond three generations. There are indications of the existence of additional neutrinos, which should be tested by definitive experiments. The number of neutrino species has important implications not only in particle physics but also in physics of early Universe. Also many fundamental natures of neutrinos remain to be studied, such as absolute values of masses, nature of the particle (Majorana or Dirac particle). This article concentrates on the future experimental prospects on the study of neutrino physics by means of neutrino oscillation.