Charge Parity Research Articles

Leptonic CP phase determined by an equation involving PMNS matrix elements

Several approximate equalities among the matrix elements of the Cabibbo–Kobayashi–Maskawa (CKM) and Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrices imply that hidden symmetries may exist and be common for both quark and neutrino sectors. The charge parity (CP) phase of the CKM matrix () is involved in these equalities and can be investigated when these equalities turn into several equations. As we substitute those experimentally measured values of the three mixing angles into the equations for quarks, it is noted that one of the equations which holds exactly has a solution . That value accords with determined from available data. Generalizing the scenario to the lepton sector, the same equality determines the leptonic CP phase to be . Thus we predict the value of from the equation. So far there is no direct measurement on , but a recent analysis based on the neutrino oscillation data prefers a phase close to 270°.

TaO+as a candidate molecular ion for searches of physics beyond the standard model

The TaO$^+$ molecular ion is proposed as a candidate system for detecting signatures of charge parity (${\cal{CP}}$) violating physics beyond the standard model of elementary particles. The electron electric dipole moment (EDM) effective electric field $E_{\text{eff}} = 20.2 \left[\frac{\rm GV}{\rm cm}\right]$, the nucleon-electron scalar-pseudoscalar (ne-SPS) interaction constant $W_{S} = 17.7$ [kHz] and the nuclear magnetic quadrupole interaction constant $W_M = 0.45$ [$\frac{10^{33} {\text{Hz}}}{e\, {\text{cm}}^2}$] are found to be sizeable ${\cal{P,T}}$-odd enhancements. The ratio of the leptonic and semi-leptonic enhancements differs strongly from the one for the ThO system which may provide improved limits on the electron EDM, $d_e$, and the SPS coupling constant, $C_S$. TaO$^+$ is found to have a ${^3\Delta_1}$ electronic ground state like the previously proposed ThF$^+$ molecular ion, but an order of magnitude smaller parallel G-tensor component which makes it less vulnerable to systematic errors in experiment.

Two-photon interactions with Majorana fermions

Because Majorana fermions are their own antiparticles, their electric and magnetic dipole moments must vanish, leaving the anapole moment as their only static electromagnetic property. But the existence of induced dipole moments is not necessarily prohibited. Through a study real Compton scattering, we explore the constraints that the Majorana fermion's self-conjugate nature has on induced moments. In terms of the Compton amplitude, we find no constraints if the interactions are separately invariant under charge conjugation, parity, and time reversal. However, if the interactions are odd under parity and even under time reversal, then these contributions to the Compton amplitude must vanish. We employ a simple model to confirm these general findings via explicit calculation of the Majorana fermion's polarizabilities. We then use these polarizabilities to estimate the cross-section for $s$-wave annihilation of two Majorana fermions into photons. The cross-section is larger than a na\"ive estimate might suggest.

Yukawa sector for lepton flavor violating inh→μτandCPviolation inh→ττ

The Higgs boson discovered at the LHC opened a new chapter for particle physics. Its properties need to be studied in detail to distinguish a purely standard model (SM) Higgs boson from one of many scalars in an enlarged Higgs sector. The CMS collaboration has reported a possible lepton flavor violating (LFV) signal $h\to\mu\tau$, which if confirmed, implies that the Higgs sector is larger than in the SM. New physics responsible for this type of decay may, in general, also introduce other observable effects such as charge-parity (CP) violation in $h\to \tau\tau$. We study two types of models that single out the third generation and can induce large $h \to \mu\tau$ rates with different consequences for CP violation in $h \to \tau \tau$. Predictions for the size of the CP violating couplings require knowledge of the lepton Yukawa matrices and we discuss this in the context of two different textures considering all existing constraints.

SuppressedB→PVCPasymmetry:CPTconstraint

Charge Parity asymmetry in charmless B meson decays is a key issue to be understood. Many theoretical calculations have been performed using short distance factorization approaches which, in general, do not take into account the CPT invariance constraint. For each channel with CP violation there is an equal amount of CP asymmetry in another channel or other channels, with an opposite sign. This happens if these channels are coupled through final state interactions (FSI). In the specific process $B\to PV$, involving one pseudo-scalar and one vector particle in the final state, we argue that the CP asymmetry, inherent from a short distance mechanism, could be suppressed due to the CPT constraint. In this case, we propose a sensitive and practical experimental method to identify even a small CP asymmetry, which provides the values for $A_{CP}$ without the need for an amplitude analysis. This method, if applied directly to data, will enable to extract the CP asymmetry information in a model independent way and check to which extend the suggested suppression due to the CPT constraint is verified.

Brane parity orders in the insulating state of Hubbard ladders

The Mott insulating state of the Hubbard model at half-filling could be depicted as a spin liquid of singly occupied sites with holon-doublon quantum fluctuations localized in pairs. In one dimension the behavior is captured by a finite value of the charge parity string correlator, which fails to remain finite when generalized to higher dimensions. We recover a definition of parity brane correlator which may remain nonvanishing in presence of interchain coupling, by assigning an appropriate fractional phase to the parity breaking fluctuations. In case of Hubbard ladders at half-filling, we find that the charge parity brane is non-zero at any repulsive value of interaction. The spin parity brane instead becomes nonvanishing in the even-leg case, in correspondence to the onset of the spin gapped D-Mott phase, which is absent in the odd-leg case. The behavior of the parity correlators is also analyzed by means of a numerical DMRG analysis of the one- and two-leg ladder.

Higgs Sector with Spontaneous CP Violation in S(3) Standard Model

Conditions for spontaneous Charge-Parity (CP) violation in the scalar potential sector of general $S(3)$ Higgs-doublet model (3HDM) are analyzed. An analysis of the Higgs sector of the minimal $S(3)$-invariant extension of the Standard Model including CP violation arising from the spontaneous breaking of the electroweak symmetry is presented. This extended Higgs sector with three SU(2) doublets Higgs fields with complex vev's provides an interesting scenario to analyze the Higgs masses spectrum, trilinear self-couplings and CP violation. We present how the spontaneous electroweak symmetry breaking, coming from three $S(3)$ Higgs fields, gives an interesting scenario with nine physical Higgs and three Goldstone bosons, when spontaneous CP violation arises from the Higgs field $S(3)$ singlet $H_S$.

CP violation in h→ττ and LFV h→μτ

The CMS collaboration has reported a possible lepton flavour violating (LFV) signal $h\to\mu\tau$. Whereas this does not happen in the standard model (SM), we point out that new physics responsible for this type of decay would, in general, also produce charge-parity (CP) violation in $h\to \tau\tau$. We estimate the size of this effect in a model independent manner and find that a large asymmetry, of order 25\%, is allowed by current constraints.

Level crossing between the QCD axion and an axionlike particle

We study a level crossing between the QCD axion and an axionlike particle, focusing on the recently found phenomenon, the axion roulette, where the axionlike particle runs along the potential, passing through many crests and troughs, until it gets trapped in one of the potential minima. We perform detailed numerical calculations to determine the parameter space where the axion roulette takes place, and as a result domain walls are likely formed. The domain wall network without cosmic strings is practically stable, and it is nothing but a cosmological disaster. In a certain case, one can make domain walls unstable and decay quickly by introducing an energy bias without spoiling the Peccei-Quinn solution to the strong charge parity problem.

Constructing scalar-photon three point vertex in massless quenched scalar QED

Non perturbative studies of Schwinger-Dyson equations (SDEs) require their infnite, coupled tower to be truncated in order to reduce them to a practically solvable set. In this connection, a physically acceptable ansatz for the three point vertex is the most favorite choice. Scalar quantum electrodynamics (sQED) provides a simple and neat platform to address this problem. The most general form of the three point scalar-photon vertex can be expressed in terms of only two independent form factors, a longitudinal and a transverse one. Ball and Chiu have demonstrated that the longitudinal vertex is fixed by requiring the Ward-Fradkin-Green-Takahashi identity (WFGTI), while the transverse vertex remains undetermined. In massless quenched sQED, we construct the transverse part of the non perturbative scalar-photon vertex. This construction (i) ensures multiplicative renormalizability (MR) of the scalar propagator in keeping with the Landau-Khalatnikov-Fradkin transformations (LKFTs), (ii) has the same transformation properties as the bare vertex under charge conjugation, parity and time reversal, (iii) has no kinematic singularities and (iv) reproduces one loop asymptotic result in the weak coupling regime of the theory.

Probing QCD phase structure using baryon multiplicity distribution

The canonical partition functions $Z_n$ and the number distributions $P_n$ which are obervable in experiments, are related by a single parameter, the fugacities $\xi=\exp(\mu/T)$. With the charge parity invariance, $Z_n$ and $\xi$ can be determined. Thermodynamic quantities such as the number density susceptibility and the kurtosis are then calculated from the grand canonical partition function $Z(\xi,T)=\sum Z_n(T) \xi^n$, ($n=-N_{\rm max},\cdots, N_{\rm max}$), for any chemical potential $\mu$, although the region over which the results are reliable for these quantities is constrained by $N_{\rm max}$. We then calculate the Lee-Yang zeros, which are the zeros of $Z(\xi)$ in the complex fugacity plane, as poles of $d\log Z(\xi)/d\xi$ by using the Cauchy integral theorem. With the help of a multiple precision library, this method provides any precision required without misidentification of the zeros. We analyse $Z_n$ from the net-proton number distributions recently measured at the Relativistic Heavy Ion Collider (RHIC) by assuming the net-proton number is approximately propotional to that of the baryon after the freeze-out, and calculate the moments. We also evaluate the Lee-Yang zero structures obtained from RHIC data and compare them with those obtained from lattice quantum chromodynamics (QCD) calculations. Possible regions of QCD phase transition lines are estimated from the thermodynamics quantities and the Lee-Yang zeros. We discuss how the limited $N_{\rm max}$ in both experimental and numerical studies affects the reliability of the thermodynamic results and Lee-Yang zeros.

Fermion mass and mixing pattern in a minimal T7 flavor 331 model

We present a model based on the SU(3)C ⨂ SU(3)L ⨂ U(1)X gauge symmetry having an extra flavor group, which successfully describes the observed Standard Model fermion mass and mixing pattern. In this framework, the light active neutrino masses arise via double seesaw mechanism and the observed charged fermion mass and quark mixing hierarchy is a consequence of the symmetry breaking at very high energy. In our minimal T7 flavor 331 model, the spectrum of neutrinos includes very light active neutrinos as well as heavy and very heavy sterile neutrinos. The model has 16 effective free parameters in total, which are fitted to reproduce the experimental values of the 18 physical observables in the quark and lepton sectors. The obtained physical observables for both quark and lepton sectors are compatible with their experimental values. The model predicts the effective Majorana neutrino mass parameter of neutrinoless double beta decay to be mββ = 3 and 40 meV for the normal and the inverted neutrino spectrum, respectively. Furthermore, our model features a vanishing leptonic Dirac charge parity violating phase.

Three loop neutrino model with isolatedk±±

We propose a three loop radiative neutrino mass scenario with an isolated doubly charged singlet scalar $k^{\pm\pm}$ without couplings to the charged leptons, while two other singly charged scalars $h_1^\pm$ and $h_2^\pm$ attach to them. In this setup, the lepton flavor violation originating from $k^{\pm\pm}$ exchanges is suppressed and the model is less constrained, where some couplings can take sizable values. As reported in our previous work, the loop suppression factor at the three loop level would be too strong and realized neutrino masses in a three loop scenario could be smaller than the observed minuscule values. The sizable couplings can help us to enhance neutrino masses without drastically large scalar trilinear couplings appearing in a neutrino mass matrix, which tends to drive the vacuum stability to become jeopardized at the one loop level. Now the doubly charged scalar $k^{\pm\pm}$ has less constraint via lepton flavor violation and the vacuum can be quite stable, and thus a few hundred GeV mass in $k^{\pm\pm}$ is possible, which is within the LHC reach and this model can be tested in the near future. Note that the other $h_1^\pm$ and $h_2^\pm$ should be heavy at least around a few TeV. We suitably arrange the charges of an additional global $U(1)$ symmetry, where the decay constant of the associated Nambu-Goldstone boson can be around a TeV scale consistently. Also, this model is indirectly limited through a global analysis on results of the LHC Higgs search and issues on a dark matter candidate, the lightest Majorana neutrino. After $h_1^\pm$ and $h_2^\pm$ are decoupled, this particle couples to the standard model particles only through two charge parity even scalars in theory and thus information on this scalar sector is important. Consistent solutions are found, but a part of them is now on the edge.

BASE – The Baryon Antibaryon Symmetry Experiment

The Baryon Antibaryon Symmetry Experiment (BASE) aims at performing a stringent test of the combined charge parity and time reversal (CPT) symmetry by comparing the magnetic moments of the proton and the antiproton with high precision. Using single particles in a Penning trap, the proton/antiproton g-factors, i.e. the magnetic moment in units of the nuclear magneton, are determined by measuring the respective ratio of the spin-precession frequency to the cyclotron frequency. The spin precession frequency is measured by non-destructive detection of spin quantum transitions using the continuous Stern-Gerlach effect, and the cyclotron frequency is determined from the particle*s motional eigenfrequencies in the Penning trap using the invariance theorem. By application of the double Penning-trap method we expect that in our measurements a fractional precision of δg/g 10−9 can be achieved. The successful application of this method to the antiproton will consist a factor 1000 improvement in the fractional precision of its magnetic moment. The BASE collaboration has constructed and commissioned a new experiment at the Antiproton Decelerator (AD) of CERN. This article describes and summarizes the physical and technical aspects of this new experiment.

Search for Higgs bosons decaying toaain theμμττfinal state inppcollisions ats=8 TeVwith the ATLAS experiment

A search for the decay to a pair of new particles of either the 125 GeV Higgs boson (h) or a second charge parity (CP)-even Higgs boson (H) is presented. The data set corresponds to an integrated luminosity of 20.3 fb−1 of pp collisions at s=8 TeV recorded by the ATLAS experiment at the LHC in 2012. The search was done in the context of the next-to-minimal supersymmetric standard model, in which the new particles are the lightest neutral pseudoscalar Higgs bosons (a). One of the two a bosons is required to decay to two muons while the other is required to decay to two τ leptons. No significant excess is observed above the expected backgrounds in the dimuon invariant mass range from 3.7 to 50 GeV. Upper limits are placed on the production of h→aa relative to the standard model gg→h production, assuming no coupling of the a boson to quarks. The most stringent limit is placed at 3.5% for ma=3.75 GeV. Upper limits are also placed on the production cross section of H→aa from 2.33 to 0.72 pb, for fixed ma=5 GeV with mH ranging from 100 to 500 GeV.Received 8 May 2015DOI:https://doi.org/10.1103/PhysRevD.92.052002This 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.© 2015 CERN, for the ATLAS Collaboration

New physics effects in

In this paper, we study the Cabibbo favored three body non-leptonic decay. We show that the corresponding direct charge parity (CP) asymmetry is extremely tiny in the framework of the Standard Model (SM) and is out of experimental range. Motivated by this result we extend the study of the CP asymmetries to include a generic model where the CPV weak phase equals in a2, a model with extra gauge bosons within left–right (LR) grand unification models and a model with a charged Higgs boson. We show that the generic model can strongly enhance CP asymmetries—reaching up to 30% in some regions of the Dalitz plots and still being compatible with the existing experimental limit on the total CP asymmetry in this channel. Large CP asymmetries can be achieved in the non-manifest LR models where partial CP asymmetries up to a few can be reached and the experimental limit on the total CP asymmetry already can be used to constraint these LR SM extensions. For the two Higgs doublets models the CP asymmetries are of order 10−3.

Two-Higgs-doublet model in terms of observable quantities

We found a minimal and a comprehensive set of directly measurable quantities defining the most general two-Higgs-doublet model (2HDM); we call these quantities observables. The potential parameters of the model are expressed explicitly via these observables (plus nonphysical parameters which are similar to gauge parameters). The model with arbitrary values of these observables can, in principle, be realized (up to general enough limitations). Our results open the door for the study of Higgs models in terms of measurable quantities only. The experimental limitations can be implemented here directly, without complex, often model-dependent, analysis of the Lagrangian coefficients. The principal opportunity to determine all parameters of the 2HDM from the (future) data meets strong practical limitation. It is the problem for a very long time. Apart from this construction per se, we also obtain some by-products. Among them are the following: a simple criterium for charge parity symmetry ($CP$) conservation in the 2HDM, a new sum rules for Higgs couplings, a clear possibility of the coexistence of relatively light Higgses with the strong interaction in the Higgs sector, and a simple expression for the triple Higgs vertex $g({h}_{a}{h}_{a}{h}_{a})$, useful for the analysis of future $hhh$ coupling measurements.

A study on the optimization of finite volume effects of B K in lattice QCD by using the CUDA

Lattice quantum chromodynamics (QCD) is the non-perturbative implementation of field theory to solve the QCD theory of quarks and gluons by using the Feynman path integral approach. We calculate the kaon CP (charge-parity) violation parameter B K generally arising in theories of physics beyond the Standard Model. Because lattice simulations are performed on finite volume lattices, the finite volume effects must be considered to exactly estimate the systematic error. The computational cost of numerical simulations may increase dramatically as the lattice spacing is decreased. Therefore, lattice QCD calculations must be optimized to account for the finite volume effects. The methodology used in this study was to develop an algorithm to parallelize the code by using a graphic processing unit (GPU) and to optimize the code to achieve as close to the theoretical peak performance as possible. The results revealed that the calculation speed of the newly-developed algorithm is significantly improved compared with that of the current algorithm for the finite volume effects.

Axial Current Generation by P-Odd Domains in QCD Matter.

The dynamics of topological domains which break parity (P) and charge-parity (CP) symmetry of QCD are studied. We derive in a general setting that those local domains will generate an axial current and quantify the strength of the induced axial current. Our findings are verified in a top-down holographic model. The relation between the real time dynamics of those local domains and the chiral magnetic field is also elucidated. We finally argue that such an induced axial current would be phenomenologically important in a heavy-ion collisions experiment.

Degenerate spectrum in the neutrino mass anarchy with Wishart matrices and implications for0νββandδCP

We show that a degenerate neutrino mass spectrum can be realized in the neutrino mass anarchy hypothesis, if the neutrino Yukawa and right-handed neutrino mass matrices are given by the Wishart matrix, i.e., products of $N\ifmmode\times\else\texttimes\fi{}3$ rectangular random matrices, whose eigenvalue distribution tends to degenerate for large $N$. The mixing angle and charge-parity (CP) phase distributions are determined by either the Haar measure of U(3) or that of SO(3). We study how large $N$ is allowed to be without tension with the observed neutrino mass squared differences and find that the predicted value of ${m}_{ee}$ can be within the reach of future $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ experiments especially for $N$ on the high side of the allowed range.