Mechanism Of CP Violation Research Articles

Parisi–Wu quantization, CP violation and beyond the standard model

The Parisi–Wu scheme of quantization opens up the possibility of using anomalous fermionic gauge theories. An analysis of ultra-violet divergences reveals that the structure of counter terms is different from what is expected in conventional quantization schemes. In this paper, it is argued that there exists a possible mechanism of CP violation that requires at least three generations of quarks, a result well known from a phenomenological analysis of mass mixing of quarks. A few observations on possible ways of going beyond the Standard Model are included.

A toy Monte Carlo simulation for the transverse polarization of high-energy electron beams

Transversely-polarized beams are heuristic to the mechanism of CP violation and explore new physics. Besides, the transverse-polarization monitoring is a key point for the beam energy calibration by the resonant depolarization technique. In the article, the transverse polarization measurement of a high-energy electron beam is performed by Monte Carlo simulation on the circular electron-positron collider. The principle based on the Compton back-scattering combining a deflection magnetic field is discussed in detail. The physical presentation of the analyzing power is used to fit the asymmetric distribution of scattered electrons, which is proportional to the transverse polarization. Furthermore, we develop an efficient algorithm that obtain this analyzing power function and use different strategies to measure the transverse polarization for cross-check. Our measurement method is theoretically suitable with a statistical error 1% within few tens of seconds in Z pole on the circular electron-positron collider. The total systematic uncertainties are controlled to be about 0.6% related to the magnetic field, the drift distance, the laser polarization, the beam energy spread and the related uncertainties of a position sensitive detector.

New approach to search for parity-even and parity-odd time-reversal violation beyond the Standard Model in a storage ring

Time-reversal breaking and parity-conserving millistrong interactions, suggested in 1965, still remain a viable mechanism of CP-violation beyond the Standard Model. One of its possible manifestations is the T-odd asymmetry in the transmission of tensor-polarized deuterons through a vector-polarized hydrogen gas target. Upon the rotation of the deuteron polarization from the vertical direction into the ring plane, the T-odd asymmetries, odd against the reversal of the proton polarization in the target, will continuously oscillate with first or second harmonics of the spin precession frequency. The Fourier analysis of the oscillating T-odd asymmetries allows for an easy separation from background persistent in conventional experiments employing static vector and tensor polarizations.

Electric Dipole Moment Measurements at Storage Rings

Electric Dipole Moments (EDM) of elementary particles, including hadrons, are considered as one of the most powerful tools to discover CP-violation beyond the already known sources of the Standard Model. Such CP-violating mechanisms are required to explain the dominance of matter over anti-matter in our universe.Up to now experiments concentrated on neutral systems. Storage rings offer the possibility to measure EDMs of charged particles by observing the influence of the EDM on the spin motion. Different options and a strategy towards storage ring EDM measurements will be discussed.

CP violation in three-body B decays: a model ansatz

The mechanism of CP violation remains one of the puzzles in particle physics. Key to understanding this phenomenon are nonleptonic B decays, especially multibody decays which exhibit large CP asymmetries in various regions of phase space. A full QCD- based theoretical description of these decays is still missing, requiring the use of models to fit the data. In this paper, we suggest a model ansatz which reflects the underlying physics and the known mechanism of CP violation via the CKM matrix. In addition, since CP violation is driven by the interference between amplitudes with and without valence charm quarks, we argue that the opening of the open-charm threshold may play an important role in generating CP violation in the high invariant mass region. We present a natural extension of the isobar model to incorporate these effects. We suggest an analysis of nonleptonic three-body B decay data including this extension, which would be interesting as it may give new hints to the sources of CP violation both at low and high invariant mass.

Study of CP violation in the process of associated Higgs boson production with a decay into muon pair

After the Higgs boson discovery at the LHC, a lot of additional measurements should be performed to understand in detail the properties of the observed particle. Searches for CP violation in different physics sectors are one of the most promising and important parts of these measurements. Associated Higgs boson production in pp collisions can be a powerful tool for searches for possible CP violation in the Higgs sector. In this paper, the study of CP sensitive observables constructed for a four lepton final state is presented. It is shown that azimuthal angle distributions of leptons in this process demonstrate a strong sensitivity to CP violation at the current limits on Higgs boson coupling parameters and can reveal a genuine mechanism of CP violation.

Neutron Electric Dipole Moment on the Lattice

For the neutron to have an electric dipole moment (EDM), the theory of nature must have T, or equivalently CP, violation. Neutron EDM is a very good probe of novel CP violation in beyond the standard model physics. To leverage the connection between measured neutron EDM and novel mechanism of CP violation, one requires the calculation of matrix elements for CP violating operators, for which lattice QCD provides a first principle method. In this paper, we review the status of recent lattice QCD calculations of the contributions of the QCD Θ-term, the quark EDM term, and the quark chromo-EDM term to the neutron EDM.

CP Violation in the models of fermion localization on a domain wall (brane)

A brief survey of fermion localization mechanism on a domain wall ("thick brane") generated by a topologically nontrivial vacuum configuration of scalar fields is given. The extension of scalar fields interaction with fermions which supplies fermions with an axial mass is proposed. For several flavors and generations of fermions this extension can entail the Cabibbo-Kobayashi-Maskawa matrix of the Standard Model. As well the model with two scalar doublets which provide a supplementary CP violation mechanism is considered.

Electric dipole moments: Flavor-diagonal CP violation

Abstract Searches for permanent electric dipole moments of particles, nuclei, atoms and molecules offer an extraordinary discovery potential to new mechanisms of CP violation beyond those incorporated in the standard electroweak model. The electric dipole moments induced by speculative scenarios, on different physical systems, require a complementary approach to pave the way to the fundamental CP-violating mechanisms. New avenues presently being explored in order to improve the experimental sensitivities include projects that consider the trapping of neutral particles, the confinement of charged particles in storage rings as well as the use of radioactive nuclei.

Study of the η → π+π−e+e− decay at KLOE

The KLOE experiment has concluded its data taking in March 2006, having acquired an integrated luminosity of 2.5 fb_1 of e+e- collisions at the center of mass energy around the ø(1020) resonance. The complete data set includes a sample of 100 million η's produced through the radiative decay ø → ηγ and tagged by means of the monochromatic recoil photon. This huge amount of data allows to perform the first test of CP violation in η decays through the study of the rare η → π+π-e+e channel, measuring the asymmetry between the π+π- and the e+e- decay planes in the η rest frame (\U0001d49cϕ). Being this process flavor conserving, such an observation will point to unexpected mechanism of CP violation, thus providing an hint of new physics beyond the Standard Model. A study of the η→ π+π-e+e- decay based on a data sample of 1.7 fb_1 will be presented. Electrons and pions are identified using both the time of flight to the calorimeter and the momentum of each track. Cuts on track momenta and on photon conversion on the beam pipe allow to significantly reduce the background, with a final 20% contamination. The analysis efficiency for the signal is 8%, dominated by geometrical acceptance. The final sample of about 1600 signal events, 100 times larger than today best measurement, is used to measure both the η→ π+π-e+e-(γ) branching fraction and the asymmetry \U0001d49cϕ.

Measurements of |Vub| and |Vcb| at Belle

Precise determinations of the magnitudes of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |Vcb| and |Vub| are crucial for testing the mechanism of CP violation in the Standard Model and searching for hints of New Physics in B decays. In this article, we review recent Belle measurements of these two quantities.

B-physics prospects with the LHCb experiment

This paper summarizes the B-physics prospects of the LHCb experiment. Firstly, a brief introduction to the CKM matrix and the mechanism of CP violation in the Standard Model is given. The advantages of the LHCb experiment for B-physics exploitation will then be described, together with a short description of the detector components. Finally, the LHCb physics aims and prospects will be summarized, focusing on the measurements of sin(2β) in tree and gluonic penguin diagrams, sin(2α) in Bd0 → π+π− and π+π−π0, neutral B-meson oscillations and the Bs0 mixing phase, and the measurement of γ using a variety of complementary methods.

CP Violation in B Meson Decays

Recent CP asymmetry measurements in tree-dominated processes, $B^0\to \pi^+\pi^-, \rho^+\rho^-, \rho^{\pm}\pi^{\mp}, B^+\to DK^+$, and in penguin-dominated decays, $B \to \pi^0 K_S, \eta' K_S, \phi K_S$, are interpreted in the framework of the Kobayashi-Maskawa (KM) mechanism of CP violation. The KM phase emerges as the dominant source of CP violation in tree-dominated decays, which are beginning to constrain the unitarity triangle beyond other constraints. Improving precision of CP asymmetry measurements in penguin-dominated decays may indicate the need for new physics.

Phenomenology of charmless hadronic B decays

The decays of B mesons to a pair of charmless pseudoscalar mesons ( PP decays) or to a vector and pseudoscalar meson ( V P decays) have been analyzed within the framework of flavor SU(3) symmetry and the Kobayashi-Maskawa mechanism of CP violation. Separate PP and V P fits proved to be successful in describing the experimental data (branching ratios, CP asymmetries and time-dependent parameters). Decay magnitudes and relative weak and strong phases have been extracted from the fits. Values of the weak phase γ were found to be consistent with the current indirect bounds from other analyses of CKM parameters.

CP asymmetries in b→(s/d) transitions as a test of CKM CP violation

We point out that a simple test of the mechanism of CP violation can be performed by a measurement of the CP asymmetries in exclusive and inclusive radiative rare decays. We show that the rate asymmetries $\Delta \Gamma = \Gamma(B^- \to f \gamma) - \Gamma(B^+ \to \bar{f} \gamma)$} for certain final states $f$ can be predicted in a theoretically clean way. Some implications for $b \to s \ell^+ \ell^-$ decays are discussed.

Search for the decay KL --> pi(0)e+e-.

We report on a search for the decay KL-->pi(0)e+e- carried out by the KTeV/E799 experiment at Fermilab. This decay is expected to have a significant CP violating contribution and the measurement of its branching ratio could support the Cabibbo-Kobayashi-Maskawa mechanism for CP violation or could point to new physics. Two events were observed in the 1997 data with an expected background of 1.06+/-0.41 events, and we set an upper limit B(KL-->pi(0)e+e-)<5.1 x 10(-10) at the 90% confidence level.

Search for the decay K(L) --> pi(0)&mgr;(+)&mgr;(-)

We report on a search for the decay K(L)-->pi(0)&mgr;(+)&mgr;(-) carried out as a part of the KTeV experiment at Fermilab. This decay is expected to have a significant CP violating contribution and a direct measurement will either support the Cabibbo-Kobayashi-Maskawa mechanism for CP violation or point to new physics. Two events were observed in the 1997 data with an expected background of 0.87+/-0.15 events, and we set an upper limit B(K(L)-->pi(0)&mgr;(+)&mgr;(-))<3. 8x10(-10) at the 90% confidence level.

HEAVY MAJORANA NEUTRINOS AND BARYOGENESIS

The scenario of baryogenesis through leptogenesis is reviewed in models involving heavy Majorana neutrinos. The various mechanisms of CP violation occurring in the out-of-equilibrium lepton-number-violating decays of heavy Majorana neutrinos are studied within a resummation approach to unstable-particle mixing. It is explicitly demonstrated how the resummation approach preserves crucial field-theoretic properties such as unitarity and CPT invariance. Predictions of representative scenarios are presented after solving numerically the Boltzmann equations describing the thermodynamic evolution of the Universe. The phenomenological consequences of loop effects of heavy Majorana neutrinos on low-energy observables, such as lepton-flavor and/or lepton-number nonconservation in τ and Z-boson decays and electron electric dipole moment, are discussed.

CPviolation and baryogenesis due to heavy Majorana neutrinos

We analyze the scenario of baryogenesis through leptogenesis induced by the out-of-equilibrium decays of heavy Majorana neutrinos and pay special attention to CP violation. Extending a recently proposed resummation formalism for two-fermion mixing to decay amplitudes, we calculate the resonant phenomenon of CP violation due to the mixing of two nearly degenerate heavy Majorana neutrinos. Solving numerically the relevant Boltzmann equations, we find that the isosinglet Majorana mass may range from 1 TeV up to the grand unification scale, depending on the mechanism of CP violation and/or the flavour structure of the neutrino mass matrix assumed. Finite temperature effects and possible constraints from the electric dipole moment of electron and other low-energy experiments are briefly discussed.

Topological evolution and cosmic chaos

An account on the origins of cosmic chaos and its physical impact in an open and multiply connected universe is given. A new type of cosmic evolution by topological deformations, unpredicted by Einstein's equations, is pointed out. The chaoticity of the galactic world-lines provides a mechanism to create the galactic equidistribution. Global metrical deformations of the open and multiply connected spacelike slices induce angular fluctuations in the temperature of the microwave background. They cause backscattering of electromagnetic fields and particle creation in quantum fields. The topological microstructure of spacetime provides a mechanism for CP violation by self-interference.