Kaon System Research Articles

Verification of T Invariance in the Total Interaction Cross Section of Neutrons with Unpolarized Nuclei Using the Polarization–Asymmetry Theorem

To date, the violation of T invariance (TI) has been experimentally established for the decays [J.H.Christenson et al., Phys. Rev. Lett.13, 138 (1964)] and oscillations [A. Angelopoulos et al., Phys. Lett. B444, 43 (1998)] of neutral kaons. Phenomenologically, TI violation in the system of neutral kaons is associated with the difference of the Kobayashi–Maskawa phase from zero (or from π) in the standard model of the electroweak interaction. For nucleon–nucleus interactions, this phase turns out to be very small [P.Herszeg, inSymmetries and Fundamental Interactions in Nuclei, World Scientific, Singapore (1995), p.89)]. Estimates of the nucleon–nucleon matrix element corresponding to TI violation in various models are given in [V. Gudkov, inFundamental Physics with Pulsed Neutron Beams, World Scientific, Singapore (2001), p. 117]. All these estimates are small and have a large spread. Therefore, the verification of TI in nuclear processes actually means a search for other mechanisms for its violation. Below is a description of the experimental methods for TI verification in the total interaction cross sections of low-energy resonance neutrons with unpolarized nuclei with the use of the polarization–asymmetry (PA) theorem.

Direct tests of T, CP, CPT symmetries in transitions of neutral K mesons with the KLOE experiment

Tests of the T, CP and CPT symmetries in the neutral kaon system are performed by the direct comparison of the probabilities of a kaon transition process to its symmetry-conjugate. The exchange of in and out states required for a genuine test involving an antiunitary transformation implied by time-reversal is implemented exploiting the entanglement of K0K‾0 pairs produced at a ϕ-factory.A data sample collected by the KLOE experiment at DAΦNE corresponding to an integrated luminosity of about 1.7 fb−1 is analysed to study the Δt distributions of the ϕ→KSKL→π+π−π±e∓ν and ϕ→KSKL→π±e∓ν3π0 processes, with Δt the difference of the kaon decay times. A comparison of the measured Δt distributions in the asymptotic region Δt≫τS allows to test for the first time T and CPT symmetries in kaon transitions with a precision of few percent, and to observe CP violation with this novel method.

Implications of a matter-antimatter mass asymmetry in Penning-trap experiments

The Standard Model (SM) of particle physics, being a local, unitary and Lorentz-invariant quantum field theory, remains symmetric under the combined action of Charge, Parity, and Time Reversal (CPT) symmetry. This automatically implies that fundamental properties of particles and antiparticles should be equal in magnitude. These fundamental tenets of the CPT principle have been put to stringent tests in recent Penning-trap experiments, where the matter-antimatter mass asymmetry has been measured. In light of these recent advances, we compare the bounds arising on CPT invariance from kaon systems with those from Penning-trap experiments. Using a simple yet powerful argument of mass decomposition of hadrons, we show that bounds on quark-antiquark mass differences from kaon oscillations are way beyond the reach of Penning-trap experiments. We lay out a roadmap to discuss possible reformulations of our understanding of the SM in the case of a discovery of CPT violation by these precision experiments.

Geometric phases in kaon decays and baryogenesis

We studied the formalism for construction of Bargmann invariants (BIs) as quantum mechanical geometric phases and identified the CP invariance with the rephasing invariant phases in neutral kaon system, kaon decays, baryogenesis and leptogenesis. We develop this formalism to express the CP violation in terms of the Bargmann invariants, which allow us to interpret them as geometric phases. We then comment on the application of such generalized treatment of CP phases.

Two-loop Electroweak Corrections to ϵK

The parameter εK measures CP violation in the neutral kaon system. It is a sensitive probe of new physics and plays a prominent role in the global fit of the Cabibbo-Kobabyashi-Maskawa matrix. As one of the first discovered sources of CP violation, it has been measured in experiment to permil precision. A simple reparametrization of the efFective Hamiltonian has been recently shown to drastically reduce the perturbative errors coming from the charm-quark corrections, making the electroweak corrections relevant. In this proceedings, I will present the two-loop electroweak corrections to ϵK .

Generic model of heavy new physics for the kaon systems

Various precision observables, such as flavour changing decays, are loop induced in the standard model and their renormalisation involves cancellations between purely bosonic and fermionic interactions. Here, I will show how perturbative unitarity constraints can be used to derive renormalised matching conditions for generic theories. These general results comprise the matching conditions for specific models that address current flavour anomalies and can be used for phenomenological analyses for rare and CP violating kaon decays.

Some Aspects About Pushing the CPT and Lorentz Invariance Frontier With Neutrinos

The CPT symmetry, which combines Charge Conjugation, Parity, and Time Reversal, is a cornerstone of our model-building method, and its probable violation will endanger the most extended tool we presently utilize to explain physics, namely local relativistic quantum fields. However, the kaon system’s conservation constraints appear to be rather severe. We will show in this paper that neutrino oscillation experiments can enhance this limit by many orders of magnitude, making them an excellent instrument for investigating the basis of our understanding of Nature. As a result, verifying CPT invariance does not evaluate a specific model, but rather the entire paradigm. Therefore, as the CPT’s status in the neutrino sector, linked or not to Lorentz invariance violation, will be assessed at an unprecedented level by current and future long baseline experiments, distinguishing it from comparable experimental fingerprints coming from non-standard interactions is critical. Whether the entire paradigm or simply the conventional model of neutrinos is at jeopardy is significantly dependent on this.

Two-loop electroweak corrections to the Top-Quark Contribution to \u03f5K

The parameter ϵK measures CP violation in the neutral kaon system. It is a sensitive probe of new physics and plays a prominent role in the global fit of the Cabibbo-Kobabyashi-Maskawa matrix. The perturbative theory uncertainty is currently dominated by the top-quark contribution. Here, we present the calculation of the full two-loop electroweak corrections to the top-quark contribution to ϵK, including the resummation of QED-QCD logarithms. We discuss different renormalization prescriptions for the electroweak input parameters. In the traditional normalization of the weak Hamiltonian with two powers of the Fermi constant GF, the top-quark contribution is shifted by −1%.

Taming εK in little Randall-Sundrum models

The Randall Sundrum models receive significant constraints from the neutral kaon system. The $CP$ violating observable ${\ensuremath{\epsilon}}_{K}$, in the Randall Sundrum scenario, requires the lightest $KK$ gluon to be heavier than $\ensuremath{\sim}24\text{ }\text{ }\mathrm{TeV}$. The constraint is even stronger in the little Randall Sundrum (LRS) models, $\ensuremath{\gtrsim}32\text{ }\text{ }\mathrm{TeV}$. The LRS models are motivated for their possible visibility at the LHC. We show that the stringent constraints from $K$ physics can be relaxed in the LRS models, in the presence of the brane localized kinetic terms (BLKT). In particular, for a range of values, a UV BLKT could significantly modify the lightest $KK$ gluon wave function such that the limit can reduces to 5 TeV. We also show that such a relaxation of the constraints can also be achieved by imposing flavor symmetries \`a la minimal flavor protection.

Constraining CPT violation with Hyper-Kamiokande and ESSnuSB

CPT invariance is one of the most fundamental symmetries in nature and it plays a major role in the formulation of Quantum Field Theory. Although no definitive signal of CPT violation has been observed so far, there are many reasons to carefully investigate various low-energy phenomena that can provide better probes to test CPT symmetry. In this context, neutrino experiments are expected to provide more stringent bounds on CPT invariance violation when compared to the existing bounds from the Kaon system. In this work, we investigate the sensitivity of the upcoming long-baseline experiments: Hyper Kamiokande (T2HK, T2HKK), ESSnuSB and DUNE to constrain the CPT violating parameters $\Delta(\delta_{CP})$, $\Delta(m^2_{31})$ and $\Delta(\sin^2 \theta_{23})$, which characterize the difference between neutrino and antineutrino oscillation parameters. Further, we analyse neutrino and antineutrino data independently and constrain the oscillation parameters governing them by considering the combination of these experiments (DUNE+T2HKK and DUNE+ESSnuSB). In addition, assuming CPT symmetry is violated in nature, we study the individual ability of the aforementioned experiments to establish CPT violation. We found that the experiments Hyper-K (T2HK, T2HKK) and ESSnuSB, along with DUNE, will be able to establish CPT violation in their proposed run-times.

Finite-volume energy spectrum of the K−K−K− system

The dynamics of multi-kaon systems are of relevance for several areas of nuclear physics. However, even the simplest systems, two and three kaons, are hard to prepare and study experimentally. Here we show how to extract this information using first-principle lattice QCD results. We (1) extend the relativistic three-body quantization condition to the strangeness sector, predicting for the first time the excited level finite-volume spectrum of three kaon systems at maximal isospin, and (2) present a first lattice QCD calculation of the excited levels of this system in a finite box. We compare our predictions with the lattice results reported here and with previous ground state calculations and find very good agreement.

Testing CPT Symmetry with Neutral K Mesons: A Review

The neutral kaon system is a very peculiar system that offers unique possibilities to perform precise tests of the CPT symmetry. The entanglement of neutral kaon pairs that are produced at a ϕ-factory opens up new ways and scenarios in order to test this fundamental discrete symmetry. In this paper, the results of the most recent and significant CPT tests are reviewed. Experiments have set stringent limits on the CPT-violating parameters of different phenomenological models, some of them associated to possible decoherence mechanisms or Lorentz symmetry violation which might be justified in a quantum gravity framework. The present results show no violation of CPT symmetry, while their accuracy in some cases reaches the interesting level at which–in the most optimistic scenarios–quantum gravity effects might show up.

Standard-Model Prediction of ε_{K} with Manifest Quark-Mixing Unitarity.

The parameter ε_{K} describes CP violation in the neutral kaon system and is one of the most sensitive probes of new physics. The large uncertainties related to the charm-quark contribution to ε_{K} have so far prevented a reliable standard-model prediction. We show that Cabibbo-Kobayashi-Maskawa unitarity enforces a unique form of the |ΔS=2| weak effective Lagrangian in which the short-distance theory uncertainty of the imaginary part is dramatically reduced. The uncertainty related to the charm-quark contribution is now at the percent level. We present the updated standard-model prediction ε_{K}=2.16(6)(8)(15)×10^{-3}, where the errors in parentheses correspond to QCD short-distance, long-distance, and parametric uncertainties, respectively.

CP asymmetry in the angular distribution of \u03c4 \u2192 KS\u03c0\u03bd\u03c4 decays

In this work, we study the C P asymmetry in the angular distribution of τ → KSπντ decays, taking into account the known C P violation in {K}^0-{overline{K}}^0 mixing. It is pointed out for the first time that, once the well-measured C P violation in the neutral kaon system is invoked, a non-zero C P asymmetry would appear in the angular observable of the decays considered, even within the Standard Model. By employing the reciprocal basis, which is most convenient when a KS(L) is involved in the final state, the C P -violating angular observable is derived to be two times the product of the time-dependent C P asymmetry in K → π+π− and the mean value of the angular distribution in {tau}^{pm}to {K}^0left({overline{K}}^0right){pi}^{pm }{overline{nu}}_{tau}left({nu}_{tau}right) decays. Compared with the Belle results measured in four different bins of the K π invariant mass, our predictions lie within the margins of these measurements, except for a 1.7 σ deviation for the lowest mass bin. While being below the current Belle detection sensitivity that is of mathcal{O} (10−3), our predictions are expected to be detectable at the Belle II experiment, where sqrt{70} times more sensitive results will be obtained with a 50 ab−1 data sample.

Problems with experimental observation of violation of Wigner inequalities in a system of neutral kaons

In the current work we add background to a system of neutral kaons using a Werner state. We show that the violation of Wigner inequalities is only observervable in experiment in case when the background contribution is less than 1%.

Search for CP Violation in D_{s}^{+}→K_{S}^{0}π^{+}, D^{+}→K_{S}^{0}K^{+}, and D^{+}→ϕπ^{+} Decays.

A search for charge-parity (CP) violation in Cabibbo-suppressed D_{s}^{+}→K_{S}^{0}π^{+}, D^{+}→K_{S}^{0}K^{+}, and D^{+}→ϕπ^{+} decays is reported using proton-proton collision data, corresponding to an integrated luminosity of 3.8 fb^{-1}, collected at a center-of-mass energy of 13TeV with the LHCb detector. High-yield samples of kinematically and topologically similar Cabibbo-favored D_{(s)}^{+} decays are analyzed to subtract nuisance asymmetries due to production and detection effects, including those induced by CP violation in the neutral kaon system. The results areA_{CP}(D_{s}^{+}→K_{S}^{0}π^{+})=(1.3±1.9±0.5)×10^{-3},A_{CP}(D^{+}→K_{S}^{0}K^{+})=(-0.09±0.65±0.48)×10^{-3},A_{CP}(D^{+}→ϕπ^{+})=(0.05±0.42±0.29)×10^{-3},where the first uncertainties are statistical and the second systematic. They are the most precise measurements of these quantities to date, and are consistent with CP symmetry. A combination with previous LHCb measurements, based on data collected at 7 and 8TeV, is also reported.

Absolute Hidden Symmetry in Time and Absolute Asymmetry in Mass and Velocity between a Particle and Its Anti-Particle

In this paper we will the discuss possible hidden symmetry in time and the possible asymmetry in mass and velocity between a particle and its anti-particle. Possible hidden symmetry in time between a particle and its anti-particle manifested in their corresponding possible hidden variables in time, fr and -fr  was first discussed in Brodet (2017b). In this paper we will extend the discussion and discuss how the above possible hidden symmetry in time and its corresponding possible symmetry in absolute position, energy and momentum, may yield an asymmetry in mass and velocity of a particle and its corresponding anti-particle. We will deconstruct the particle’s and anti-particle’s absolute position, into three complex number describing the particle/anti-particle time, velocity and mass. The particle/anti-particle symmetry and asymmetry of the above complex numbers will be discussed in the context of parity violation and the known asymmetry in angular production of particles and anti-particles. Moreover, the possible mass asymmetry will be used to explain the CP violation in the neutral kaon system. Finally, experimental ways to investigate and test the above are presented.

Charge-conjugation-parity violation of neutral K-mesons in a temporal wave function model

The founding fathers of the quantum theory already struggled with the different roles of space and time in quantum theory. Position is by default represented by an operator, whereas time is usually treated as a parameter. Time operator models exist, in particular a certain Time Operator model denoted the Temporal Wave Function (T.W.F.). This one extends the Born's rule to the time domain. The statistics of pure exponential decay does not allow to exclude this Born rule for time. However the tiny violation of the combined discrete symmetries $P$ (parity) and $C$ (charge conjugation) observed in the K-meson system allows us, as we prove in this paper, to discriminate between the standard predictions, made in the framework of the so-called mass-decay matrix formalism, and the T.W.F. predictions. We also present experimental data of a particular $CP$ violating decay channel, that is in contrast with the prediction of T.W.F. approach model, resulting in its falsification.

Tests of discrete symmetries with the neutral kaon system at the KLOE and KLOE-2 experiments

The KLOE-2 experiment continues and extends the program of its predecessor KLOE in the field of discrete symmetry tests with the K meson system, among other studies which comprise light meson spectroscopy, dark matter searches and γγ physics. Together, KLOE and KLOE-2 have recorded the largest sample (almost 8 fb− 1) of e+e− collisions at the energy equal to ϕ meson mass, amounting to 2.4 × 1010 of produced ϕ mesons. We report on the latest results and ongoing analyses of KLOE and KLOE-2 concerning discrete symmetry tests and measurements of symmetry-violating observables. A measurement of the CPT violation sensitive asymmetry in semileptonic decays of K˙S with 1.7 fb− 1 of KLOE data will be presented, which improves the sensitivity w.r.t. previous measurements about twice. Moreover, status of direct tests of T and CPT in transitions of neutral kaons performed with the ϕ →K˙SK˙L → πeν, 3π0(2π) processes will be reported, followed by the search of the CP-violating decay K˙S → 3π0 using the data recently acquired by KLOE-2.

Neutrinos, DUNE and the world best bound on CPT invariance

CPT symmetry, the combination of Charge Conjugation, Parity and Time reversal, is a cornerstone of our model building strategy and therefore the repercussions of its potential violation will severely threaten the most extended tool we currently use to describe physics, i.e. local relativistic quantum fields. However, limits on its conservation from the Kaon system look indeed imposing. In this work we will show that neutrino oscillation experiments can improve this limit by several orders of magnitude and therefore are an ideal tool to explore the foundations of our approach to Nature.Strictly speaking testing CPT violation would require an explicit model for how CPT is broken and its effects on physics. Instead, what is presented in this paper is a test of one of the predictions of CPT conservation, i.e., the same mass and mixing parameters in neutrinos and antineutrinos. In order to do that we calculate the current CPT bound on all the neutrino mixing parameters and study the sensitivity of the DUNE experiment to such an observable. After deriving the most updated bound on CPT from neutrino oscillation data, we show that, if the recent T2K results turn out to be the true values of neutrino and antineutrino oscillations, DUNE would measure the fallout of CPT conservation at more than 3σ. Then, we study the sensitivity of the experiment to measure CPT invariance in general, finding that DUNE will be able to improve the current bounds on Δ(Δm312) by at least one order of magnitude. We also study the sensitivity to the other oscillation parameters. Finally we show that, if CPT is violated in nature, combining neutrino with antineutrino data in oscillation analysis will produce imposter solutions.