Neutral Meson System Research Articles

CPT Symmetry Searches in the Neutral Meson System

A review of the landscape of CPT symmetry tests is presented, centered around the Standard-Model Extension and focusing on tests in the neutral meson system. A discussion of the relevant theories summarizes original ideas. It is followed by a short transition into phenomenology. A more detailed parameterization is presented. Various experiments are used to deliver an overview of testing CPT from every angle that the theory suggested and that the neutral meson (NM) system could accommodate.

Transition probabilities for flavor eigenstates of non-Hermitian Hamiltonians in the PT-broken phase

We investigate the transition probabilities for the “flavor” eigenstates in the two-level quantum system, which is described by a non-Hermitian Hamiltonian with the parity and time-reversal (PT) symmetry. Particularly, we concentrate on the so-called PT-broken phase, where two eigenvalues of the non-Hermitian Hamiltonian turn out to be a complex-conjugate pair. In this case, we find that the transition probabilities will be unbounded in the limit of infinite time t → +∞. However, after performing a connection between a non-Hermitian system, which exhibits passive PT symmetry and global decay, and the neutral-meson system in particle physics, we observe that the diverging behavior of the transition probabilities is actually applicable to the gauge-transformed neutral-meson states, whereas the transition probabilities for physical states are exponentially suppressed by the global decay. We also present a brief review on the situation at the so-called exceptional point, where both the eigenvalues and eigenvectors of the Hamiltonian coalesce.

Particle mixing and the emergence of classicality: A spontaneous-collapse-model view

Spontaneous collapse models aim to resolve the measurement problem in quantum mechanics by considering wave-function collapse as a physical process. We analyze how these models affect a decaying flavor-oscillating system whose evolution is governed by a phenomenological non-Hermitian Hamiltonian. In turn, we apply two popular collapse models, the Quantum Mechanics with Universal Position Localization and the Continuous Spontaneous Localization models, to a neutral meson system. By using the equivalence between the approaches to the time evolution of decaying systems with a non-Hermitian Hamiltonian and a dissipator of the Lindblad form in an enlarged Hilbert space, we show that spontaneous collapse can induce the decay dynamics in both quantum state and master equations. Moreover, we show that the decay property of a flavor-oscillating system is intimately connected to the time (a)symmetry of the noise field underlying the collapse mechanism. This (a)symmetry, in turn, is related to the definition of the stochastic integral and can provide a physical intuition behind the It\=o-Stratonovich dilemma in stochastic calculus.

Study of temporal quantum correlations in decoheringBandKmeson systems

In this work we study temporal quantum correlations, quantified by Leggett-Garg (LG) and LG-type inequalities, in the $B$ and $K$ meson systems. We use the tools of open quantum systems to incorporate the effect of decoherence which is quantified by a single phenomenological parameter. The effect of $CP$ violation is also included in our analysis. We find that the LG inequality is violated for both $B$ and $K$ meson systems, the violation being most prominent in the case of $K$ mesons and least for $B_s$ system. Since the systems with no coherence do not violate LGI, incorporating \textit{decoherence} is expected to decrease the extent of violation of LGI and is clearly brought out in our results. We show that the expression for the LG functions depends upon an additional term, apart from the experimentally measurable meson transition probabilities. This term vanishes in the limit of zero decoherence. On the other hand, the LG-type parameter can be directly expressed in terms of transition probabilities, making it a more appropriate observable for studying temporal quantum correlations in neutral meson systems.

Can a spontaneous collapse in flavour oscillations be tested at KLOE?

Why do we never see a table in a superposition of here and there? This problem gets a solution by so called collapse models assuming the collapse as a genuinely physical process. Here we consider two specific collapse models and apply them to systems at high energies, i.e. flavour oscillating neutral meson systems. We find on one hand a potentially new interpretation of the decay rates introduced by hand in the standard formalism and on the other hand that these systems at high energies constrain by experimental data the possible collapse scenarios.

The signal of ill-defined CPT weakening entanglement in the {B_d} system

In the presence of quantum-gravity fluctuations (space-time foam), the CPT operator may be ill-defined. Its perturbative treatment leads to a modification of the Einstein–Podolsky–Rosen correlation of the neutral meson system by adding an entanglement-weakening term of the wrong exchange symmetry, the omega -effect. In the current paper we identify how to probe the complex omega in the entangled B_d-system using the flavour (f)–CP(g) eigenstate decay channels: the connection between the intensities for the two time-ordered decays (f, g) and (g, f) is lost. Appropriate observables are constructed allowing independent experimental determinations of Re(omega ) and Im(omega ), disentangled from CPT violation in the evolution Hamiltonian Re(theta ) and Im(theta ). 2sigma tensions for both Re(theta ) and Im(omega ) are shown to be uncorrelated.

The GKLS Master Equation in High Energy Physics

Utilizing the GKLS master equation we show that the decay property of a particle can be straightforwardly incorporated. In standard particle physics the decay is often described by an efficient non-hermitian Hamiltonian, in accord with the seminal Wigner-Weisskopf approximation. We show that by enlarging the Hilbert space and defining specific GKLS operators we have attained a formalism with a hermitian Hamiltonian and probability conserving states. This proves that the Wigner-Weisskopf approximation is Markovian and completely positive. In addition, this formalism allows a straightforward generalization to many-particle decays. Last, but not least, some impacts of the GKLS master equation onto systems at high energies are reported, such as for neutral meson, neutrino and hyperon systems.

Entangled Bd mesons and genuine T, CP and CPT asymmetry parameters

We establish the precise connection between the theoretical T, CP, CPT asymmetries, in terms of transition probabilities between the neutral meson Bd states, and the experimental asymmetries, in terms of the double decay rate intensities for Flavour-CP eigenstate decay products in a B-Factory of entangled states. Genuine asymmetry parameters in the time distribution of the asymmetries are identified and their measurability analysed, disentangling genuine and possible fake terms. The nine asymmetry parameters – three different observables for each one of the three symmetries – are expressed in terms of the ingredients of the Weisskopf-Wigner dynamical description of the entangled Bd-meson states and we obtain a global fit to their values from the BaBar Collaboration experimental results. The possible fake terms are all compatible with zero. The information content of the nine asymmetry parameters is indeed different. The non-vanishing and are impressive separate direct evidence of Time-Reversal-Violation and CP-Violation in these transitions (and compatible with Standard Model expectations). A 2σ effect for the Re(θ) parameter responsible of CPT-Violation appears; interpreted as an upper limit, it leads to eV at 95% C.L. for the diagonal flavour terms of the mass matrix. Finally, we consider scenarios where, in the presence of quantum gravity fluctuations (space-time foam), the CPT operator may be ill-defined. Its perturbative treatment leads to a modification of the Einstein-Podolsky-Rosen correlation of the neutral meson system by adding an Entanglement-weakening term of the wrong exchange symmetry, the ω-effect. The analysis is extended to identify how to probe the complex ω when the connection between the Intensities for the two time-ordered decays (f, g) and (g, f) is lost (f flavour and g CP eigenstate decay channels), and how the ω-effect is disentangled from CPT violation in the evolution Hamiltonian.

Three-family left-right symmetry with low-scale seesaw mechanism

We suggest a new left-right symmetric model implementing a low-scale seesaw mechanism in which quantum consistency requires three families of fermions. The symmetry breaking route to the Standard Model determines the profile of the “next” expected new physics, characterized either by the simplest left-right gauge symmetry or by the 3-3-1 scenario. The resulting Z′ gauge bosons can be probed at the LHC and provide a production portal for the right-handed neutrinos. On the other hand, its flavor changing interactions would affect the K, D and B neutral meson systems.

Constraining flavor changing interactions from LHC Run-2 dilepton bounds with vector mediators

Within the context of vector mediators, is a new signal observed in flavor changing interactions, particularly in the neutral mesons systems $K^{0}-\bar{K}^{0}$, $D^{0}-\bar{D}^{0}$ and $B^0-\bar{B^0}$, consistent with dilepton resonance searches at the LHC? In the attempt to address this very simple question, we discuss the complementarity between flavor changing neutral current (FCNC) and dilepton resonance searches at the LHC run 2 at $13$TeV with $3.2\, {\rm fb^{-1}}$ of integrated luminosity, in the context of vector mediators at tree level. Vector mediators, are often studied in the flavor changing framework, specially in the light of the recent LHCb anomaly observed at the rare B decay. However, the existence of stringent dilepton bound severely constrains flavor changing interactions, due to restrictive limits on the $Z^{\prime}$ mass. We discuss this interplay explicitly in the well motivated framework of a 3-3-1 scheme, where fermions and scalars are arranged in the fundamental representation of the weak SU(3) gauge group. Due to the paucity of relevant parameters, we conclude dilepton data leave little room for a possible new physics signal stemming from these systems, unless a very peculiar texture parametrization is used in the diagonalization of the CKM matrix. In other words, if a signal is observed in such flavor changing interactions, it is unlikely comes from a 3-3-1 model.

Self-cancellation of a scalar in neutral meson mixing and implications for the LHC

Flavor-changing neutral scalar interactions are a standard feature of generic multi-Higgs models. These are constrained by mixing in the neutral meson systems. We consider situations where there are natural cancellations in such contributions. In particular, when the spin-0 particle has both scalar and pseudoscalar couplings, one may have a self-cancellation. We illustrate one such partial cancellation with Branco-Grimus-Lavoura models. We also inquire whether the flavor-changing quark interactions can lead to new production mechanisms for a neutral scalar at LHC.

Re-examining [formula omitted] and [formula omitted] from evolution of [formula omitted] mesons with decoherence

In the time evolution of neutral meson systems, a perfect quantum coherence is usually assumed. The important quantities of the Bd0 system, such as sin⁡2β and Δmd, are determined under this assumption. However, the meson system interacts with its environment. This interaction can lead to decoherence in the mesons even before they decay. In our formalism this decoherence is modelled by a single parameter λ. It is desirable to re-examine the procedures of determination of sin⁡2β and Δmd in meson systems with decoherence. We find that the present values of these two quantities are modulated by λ. Re-analysis of Bd0 data from B-factories and LHCb can lead to a clean determination of λ, sin⁡2β and Δmd.

Proposal for experimental test of the time-dependent Wigner inequalities for neutral pseudoscalar meson systems

Recently a new class of time-dependent Bell inequalities in Wigner form was introduced. The structure of the inequalities allows experimental studies of quantum and open quantum systems in external fields. In this paper we study the properties of the time dependent Wigner inequalities using the time evolution of neutral pseudoscalar mesons. It is shown that it is always possible to find a range of parameters to test for violation in an experimentally accessible area. The effect of the relaxation of the inequalities for large time scales is demonstrated.

Novel T-violation observable open to any decay channel at meson factories

Two genuine Quantum phenomena: Entanglement and Filtering Measurement are at the origin of the first direct observation of Time-Reversal-Violation in the time evolution of the B neutral meson system by BaBar. The used meson transitions are directly connected to semileptonic and CP-eigenstate decay channels. We analyse the possibility of extending the observable asymmetries to more decay channels. We propose an alternative T-Violation Asymmetry in the meson factories which allows its opening to any pair of decay channels. The new asymmetry needs also the measurement of the time dependent total survival probability of the initial tagged states. By combining several asymmetries these total survival probabilities can be avoided. We analyse carefully the channels that can be used and the sufficient condition in order the proposed asymmetry be a genuine T violation measurement.

Experimental prospects for C, P, T, CP, and CPT tests

Discrete symmetry violation in the weak interaction is central to the Standard Model of particle physics, however the origin of these violations is not well understood. Nor are we able to provide a satisfactory explanation of the Universal dominance of matter over antimatter, an issue related to CP violation. As a result study of discrete symmetry violation remains a topic of broad interest. These proceedings discuss experimental prospects of studying C, P, T, CP and CPT symmetries in a number of contexts, including the use of triple product asymmetries and entangled neutral meson systems.

Newtonian self-gravitation in the neutral meson system

We derive the effect of the Schr\"odinger-Newton equation, which can be considered as a nonrelativistic limit of classical gravity, for a composite quantum system in the regime of high energies. Such meson-antimeson systems exhibit very unique properties, e.g., distinct masses due to strong and electroweak interactions. This raises an immediate question: what does one mean by mass in gravity for a state that is a superposition of mass eigenstates due to strong and electroweak interactions? We find conceptually different physical scenarios due to lacking of a clear physical guiding principle to explain which mass is the relevant one and due to the fact that it is not clear how the flavor wave function relates to the spatial wave function. There seems to be no principal contradiction. However, a nonlinear extension of the Schr\"odinger equation in this manner strongly depends on the relation between the flavor wave function and spatial wave function and its particular shape. In opposition to the continuous spontaneous localization collapse models we find a change in the oscillating behavior and not in the damping of the flavor oscillation.

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.

Comment on testing the time-reversal symmetry in neutral meson systems

Following a stimulating question raised by R. Winston during the CP violation session of the BEACH 2012 Conference, we briefly comment about testing the time reversal symmetry in neutral meson systems, reviewing the criticism of a previous test in the neutral K meson system performed using the Kabir asymmetry, and discussing how this difficulty can be overcome exploiting the entanglement in K and B meson pairs produced at ϕ- and B-factories.

CP violation measurements with the ATLAS detector

The ATLAS experiment at the Large Hadron Collider measures CP violation in the neutral Bs0 meson system through the exclusive decay Bs0→J/ψ(μ+μ−)ϕ(K+K−) by analysing time dependent angular correlations of the final state. With 4.9fb−1 of integrated luminosity recorded in 2011 in pp collisions at the LHC at a centre of mass energy of s=7 TeV, first ATLAS results on the values of the CP-violating phase ϕs, the decay width difference ΔΓs as well as other physics parameters of the Bs0 meson decay have been obtained and will be presented here.

Novel sources of Flavor Changed Neutral Currents in the 331 RHN model

Sources of Flavor Changed Neutral Currents (FCNC) emerge naturally from a well motivated framework called 3-3-1 with right-handed neutrinos model, 331 RHN for short, mediated by an extra neutral gauge boson Z′. Following previous work we calculate these sources and in addition we derive new ones coming from CP-even and -odd neutral scalars which appear due to their non-diagonal interactions with the physical standard quarks. Furthermore, by using 4 texture zeros for the quark mass matrices, we derive the mass difference terms for the neutral mesons systems K 0– $\bar{K}^{0}$ , D 0– $\bar{D}^{0}$ and B 0– $\bar{B^{0}}$ and show that, though one can discern that the Z′ contribution is the most relevant one for mesons oscillations purposes, scalar contributions play a role also in this processes and hence it is worthwhile to investigate them and derive new bounds on space of parameters. In particular, studying the B 0– $\bar {B^{0}}$ system we set the bounds M Z′≳4.2 TeV and $M_{S_{2}},M_{I_{3}} \gtrsim7.5~\mbox{TeV}$ in order to be consistent with the current measurements.