Meson System Research Articles

Constraints on light dark sector particles from lifetime difference of heavy neutral mesons

Heavy meson decays with missing energy in the final state offer interesting avenues to search for light invisible new physics such as dark matter (DM). In this context, we show that such new physics (NP) interactions also affect lifetime difference in neutral meson-antimeson mixing. We consider general dimension-six effective quark interactions involving a pair of DM particles and calculate their contributions to lifetime difference in beauty and charm meson systems. We use the latest data on mixing observables to constrain the relevant effective operators. We find that lifetime differences provide novel and complementary flavor constraints compared to those obtained from heavy meson decays. Published by the American Physical Society 2024

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.

Probing quantum decoherence at Belle II and LHCb

With the advent of Belle II and the LHCb upgrade, the precision measurements of various B-Physics observables are on cards. This holds significant potential for delving into physics beyond the standard model of electroweak interactions. These measurements can also serve as means to establish limits on phenomena occurring at much finer length scales, such as quantum decoherence, which may arise due to potential discreteness in space-time or non-trivial topological effects. In this work, we set up the formalism to investigate the impact of quantum decoherence on several potential observables in B meson systems. The approach employs the trace-preserving Kraus operator formalism, extending unitary evolution to non-unitary dynamics while maintaining complete positivity. In this formalism, the decoherence effects are parametrized in terms of a single parameter. Through the analysis of purely leptonic, semileptonic, and non-leptonic decays of B mesons, we identify observables that could, in principle, be influenced by decoherence. The theoretical expressions are provided without neglecting the impact of decay width difference (∆Γ) and CP violation in mixing. Considering that many of these observables can be measured with high precision using the abundant data collected by LHCb and Belle II, our formalism can be applied to establish constraints on the decoherence parameter through multiple decay channels. This offers an alternative set-up for such studies, which, at present, are predominantly conducted in the neutrino sector.

Spectrum of the molecular pentaquarks

We investigate the mass spectrum of the molecular pentaquarks composed of a baryon and a meson. We establish the underlying relations among the near-threshold interactions of the molecular tetraquark and pentaquark systems. We find the existence of the molecule candidates in the ΣcD¯(*), DD*, and DD¯* systems indicates a substantial presence of the hadronic molecules in the heavy baryon plus heavy meson systems ( refers to the hadrons with the c and/or s quarks). We make an exhaustive prediction of the possible bound/virtual molecular states in the systems: Σc(*)D¯(*), Σc(*)D(*), Ξc(′,*)D¯(*), Ξc(′,*)D(*), Σc(*)K*, Σc(*)K¯*, Ξc(′,*)K*, Ξc(′,*)K¯*, Ξcc(*)D¯(*), Ξcc(*)D(*), Ξcc(*)K*, Ξcc(*)K¯*, Σ(*)D¯(*), Σ(*)D(*), Ξ(*)D¯(*), Ξ(*)D(*), Σ(*)K*, Σ(*)K¯*, Ξ(*)K*, Ξ(*)K¯*. Hunting for the predicted states in experiments will significantly deepen our understanding of the formation mechanism of the hadronic molecules, and shed light on the manifestation of flavor symmetry in the low-energy residual strong interactions. Published by the American Physical Society 2024

On the fractional quark–antiquark confinement and symplectic quantum mechanics

Using the formalism of generalized fractional derivatives, a two-dimensional nonrelativistic meson system is studied. The mesons are interacting by a Cornell potential. The system is formulated in the domain of the symplectic quantum mechanics by means of the generalized fractional Nikiforov–Uvarov method. The corresponding Wigner function and the energy eigenvalues are then derived. The effect of fractional parameters [Formula: see text] and [Formula: see text] with the ground state solution is analyzed through the Wigner function for the charm–anticharm, bottom–antibottom and [Formula: see text] mesons. One of the fundamental achievements of such Cornell model is the determination of heavy quarkonia mass spectra. We have computed these masses and the present results are in agreement with the experimental data, improving previous theoretical results.

Flavor changing interactions confronted with meson mixing and hadron colliders

We have witnessed some flavor anomalies appearing in the past years, and explanations based on extended gauge sectors are among the most popular solutions. These beyond the Standard Model (SM) theories often assume flavor-changing interactions mediated by new vector bosons. Still, at the same time, they could yield deviations from the SM in the ${K}^{0}\ensuremath{-}{\overline{K}}^{0}$, ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$, ${B}_{d}^{0}\ensuremath{-}\overline{B}{{\text{ }}^{0}}_{d}$, and ${B}_{s}^{0}\ensuremath{-}\overline{B}{{\text{ }}^{0}}_{s}$ meson systems. Using up-to-date data on the mass difference of these meson systems, we derive lower mass bounds on vector mediators for two different parametrizations of the quark mixing matrices. Focusing on a well-motivated model based on the fundamental representation of the weak SU(3) gauge group, we put our findings into perspective with current and future hadron colliders to conclude that meson mass systems can give rise to bounds much more stringent than those from high-energy colliders and that recent new physics interpretations of the $b\ensuremath{\rightarrow}s$ and $R({D}^{*})$ anomalies are disfavored.

CP Violation in Baryon Decays at LHCb

Observations in astronomy suggest that our Universe contains an abundance of matter over antimatter, which can only be explained if the combined CP symmetry is violated. Studies of CP violation have driven the flavor physics with the aim of testing the Standard Model of particle physics and searching for physics beyond it. CP violation is discovered in strange, beauty, and charm meson systems; however, no conclusive sign of CP violation in baryon decays has been observed yet. This review summarizes CP violation studies performed by the LHCb experiment in charmless decays and rare decays of beauty baryons and singly Cabibbo-suppressed decays of charm baryons. A brief on prospects for future LHCb measurements is also discussed.

Solving hadron structures using the basis light-front quantization approach on quantum computers

Quantum computing has demonstrated the potential to revolutionize our understanding of nuclear, atomic, and molecular structure by obtaining forefront solutions in nonrelativistic quantum many-body theory. In this work, we show that quantum computing can be used to solve for the structure of hadrons, governed by strongly interacting relativistic quantum field theory. Following our previous work on light unflavored mesons as a relativistic bound-state problem within the nonperturbative Hamiltonian formalism, we present the numerical calculations on simulated quantum devices using the basis light-front quantization approach. We implement and compare the variational quantum eigensolver and the subspace-search variational quantum eigensolver to find the low-lying mass spectrum of the light meson system and its corresponding light-front wave functions as quantum states from ideal simulators, noisy simulators, and IBM quantum computers. Based on obtained quantum states, we evaluate the meson decay constants and parton distribution functions directly on the quantum circuits. Our calculations on the quantum computers and simulators are in reasonable agreement with accurate numerical solutions solved on classical computers when noises are moderately small, and our overall results are comparable with the available experimental data.

A new study of relativistic and nonrelativistic for new modified Yukawa potential via the BSM in the framework of noncommutative quantum mechanics symmetries: An application to heavy-light mesons systems

In this article, the deformed Dirac equation was solved with a new modified Yukawa potential within three tensor interactions (Coulomb-like, Yukawa-like, and Hulthén-type potentials) (NMYTTIs). This study is scrutinized by taking into consideration the noncommutative space-space effect within the relativistic and nonrelativistic regimes using the parametric of Bopp’s shift method and standard perturbation theory with the help of an approximation to the centrifugal term. In the framework of the spin and pseudospin (p-spin) symmetry, we obtain the global new energy eigenvalue which equals the energy eigenvalue in usual relativistic QM under the new modified Yukawa potential plus the corrected of energy induced with three infinitesimal additive parts of the relativistic Hamiltonian corresponds to the spin-orbit interaction, the new modified Zeeman and the rotational Fermi term. The new values that we get appeared sensitive to the quantum numbers (j,k,l,lps,s,sps,m,mps) and (j,l,s,m) (within the relativistic and nonrelativistic regimes, respectively), the potential depths (A,B,C), the range of the potential α, and noncommutativity parameters (η,σ,χ). The present results are applied for calculating the mass spectra of heavy mesons such as heavy-light mesons HLM such as cc¯, bb¯, bc¯, bs¯, cs¯ and bq¯, q=(u,d). Our results excellent agree perfectly with the ones in works of literature.

Investigating S-wave bound states composed of two pseudoscalar mesons* *Supported by National Natural Science Foundation of China (12105149, 11775024)

In this study, we systematically investigated two-pseudoscalar meson systems with the Bethe-Salpeter equation in the ladder and instantaneous approximations. By solving the Bethe-Salpeter equation numerically with the kernel containing the one-particle exchange diagrams, we found that the , , , , , , , , and systems with can exist as bound states. We also studied the contributions from heavy meson ( and ) exchanges and found that the contributions from heavy meson exchanges cannot be ignored.

Quark-Antiquark Effective Potential in Symplectic Quantum Mechanics

In this paper, we study within the structure of Symplectic Quantum Mechanics a bidimensional nonrelativistic strong interaction system which represent the bound state of heavy quark-antiquark, where we consider a Cornell potential which consists of Coulomb-type plus linear potentials. First, we solve the Schrödinger equation in the phase space with the linear potential. The solution (ground state) is obtained and analyzed by means of the Wigner function related to Airy function for the c c ¯ meson. In the second case, to treat the Schrödinger-like equation in the phase space, a procedure based on the Bohlin transformation is presented and applied to the Cornell potential. In this case, the system is separated into two parts, one analogous to the oscillator and the other we treat using perturbation method. Then, we quantized the Hamiltonian with the aid of stars operators in the phase space representation so that we can determine through the algebraic method the eigenfunctions of the undisturbed Hamiltonian (oscillator solution), and the other part of the Hamiltonian was the perturbation method. The eigenfunctions found (undisturbed plus disturbed) are associated with the Wigner function via Weyl product using the representation theory of Galilei group in the phase space. The Wigner function is analyzed, and the nonclassicality of ground state and first excited state is studied by the nonclassicality indicator or negativity parameter of the Wigner function for this system. In some aspects, we observe that the Wigner function offers an easier way to visualize the nonclassic nature of meson system than the wavefunction does phase space.

Erratum: Scattering lengths for two pseudoscalar meson systems [Phys. Rev. D 89 , 054502 (2014)

Received 15 December 2021DOI:https://doi.org/10.1103/PhysRevD.105.019901© 2022 American Physical Society

The charm of 331

We perform a detailed analysis of flavour changing neutral current processes in the charm sector in the context of 331 models. As pointed out recently, in the case of Z′ contributions in these models there are no new free parameters beyond those already present in the Bd,s and K meson systems analyzed in the past. As a result, definite ranges for new Physics (NP) effects in various charm observables could be obtained. While generally NP effects turn out to be small, in a number of observables they are much larger than the tiny effects predicted within the Standard Model. In particular we find that the branching ratio of the mode D0→ μ+μ−, despite remaining tiny, can be enhanced by 6 orders of magnitude with respect to the SM. We work out correlations between this mode and rare Bd,s and K decays. We also discuss neutral charm meson oscillations and CP violation in the charm system. In particular, we point out that 331 models provide new weak phases that are a necessary condition to have non-vanishing CP asymmetries. In the case of ∆ACP, the difference between the CP asymmetries in D0→ K+K− and D0→ π+π−, we find that agreement with experiment can be obtained provided that two conditions are verified: the phases in the ranges predicted in 331 models and large hadronic matrix elements.

Decay properties of beauty and charm mesons within Isgur–Wise function formalism

We investigate the decay properties of some beauty and charm mesons with a phenomenological potential model. First, we consider the nonrelativistic Hamiltonian of the mesonic system with Coulomb plus exponential terms and study the wave function and the energy of the system using the variational approach. Thereby, we compute the masses, the decay constants, the leptonic branching fractions of heavy–light mesons and the mixing mass parameter $$\Delta {m_{{B_q}}}$$ . We study the radiative leptonic decay widths of $${D_s} \rightarrow \gamma \ell {{\bar{\nu }}} $$ , $${D^ - } \rightarrow \gamma \ell {{\bar{\nu }}} $$ and the semileptonic decay widths of $${{{\bar{B}}}_{(s)}} \rightarrow {D_{(s)}}\ell {{\bar{\nu }}} $$ and $${{{\bar{B}}}_{(s)}} \rightarrow D_{(s)}^*\ell {{\bar{\nu }}} $$ . Using Isgur–Wise function, we calculate the branching ratios of $$B \rightarrow {D^{(*)}}\pi $$ and two-body nonleptonic decay of $$D \rightarrow K\pi $$ . Our results are consistent with other theoretical models and the experimental results.

Observation of the Mass Difference between Neutral Charm-Meson Eigenstates.

A measurement of mixing and CP violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb^{-1}. A total of 30.6 million D^{0}→K_{S}^{0}π^{+}π^{-} decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for CP violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be x_{CP}=[3.97±0.46(stat)±0.29(syst)]×10^{-3} and y_{CP}=[4.59±1.20(stat)±0.85(syst)]×10^{-3}, respectively. The CP-violating parameters are measured as Δx=[-0.27±0.18(stat)±0.01(syst)]×10^{-3} and Δy=[0.20±0.36(stat)±0.13(syst)]×10^{-3}. This is the first observation of a nonzero mass difference in the D^{0} meson system, with a significance exceeding seven standard deviations. The data are consistent with CP symmetry and improve existing constraints on the associated parameters.

Calculation of the Top-Quark Yukawa coupling constant

In this work, we study meson systems consisting of quark–antiquark. We solve Lippman–Schwinger equation numerically for heavy meson systems. We attempt to find a nonrelativistic potential model through which we can solve the quark–antiquark bound state problem. The coefficients obtained are in agreement with Martin potential coefficients. Via this method we also determine the strong coupling constant of Cornell and Yukawa potentials for the heavy meson.

Recent results on branching fraction and CP asymmetry in B → ϕϕK decays

We present precise measurements of the branching fraction and CP-violation asymmetry in the B meson system, specifically in the charmless decays B → ϕϕK, ϕ → K+K−. This study is based on the full ϒ(4S) data set of 772×106BB‾ pairs collected by the Belle detector at KEKB asymmetric energy e+e− collider. These decays are mediated by the b → s flavor-changing neutral current (FCNC) transition, which could exhibit large CP violations due to interference of potential new-physics amplitudes appearing in the quantum loop with the b → c tree-level transition of B → ηcK, ηc → ϕϕ. Therefore, an observation of direct CP violation in B → ϕϕK decays would be a clear sign of physics beyond the standard model. In addition to being an NP probe, the decay is sensitive to possible production of glue-ball candidate that later decays as ξ → ϕϕ. Our results obtained with nine times larger statistics and refined analysis techniques significantly improve upon, and supersede, the Belle's earlier result with due consideration of the nonresonant K+K− contribution underneath the ϕ resonance.

Kinetics of the chiral phase transition in a quark–meson [formula omitted]-model

In this study an effective description in the 2PI effective-action formalism for systems of quarks and mesons in and out of equilibrium within a numerical approach is developed, allowing to approximate the complexity of QCD by taking only the lightest and most relevant degrees of freedom into account. In particular the temporarily building up of fluctuations of the net-baryon number encoded by the fourth-order cumulant (or the rescaled curtosis) for lower momenta is being demonstrated when the phase transition occurs near the critical point, or even stronger when the phase transition is of first order, although the initial system is prepared with purely Gaussian fluctuations in the net baryon number. This is the result of the evolving slow and critical order parameter, i.e., the σ-field. On the other hand, depending on the speed of the (Hubble-)expansion scale, the final dissipative evolution due to the collisions among the mesons, the quarks and anti-quarks and the order field weakens the final fluctuations considerably.

Is X(7200) the heavy anti-quark diquark symmetry partner of X(3872)?

The D^{(*)}Xi _{cc}^{(*)} system and {bar{Xi }}_{cc}^{(*)}Xi _{cc}^{(*)} system can be related to the D^{(*)}{bar{D}}^{(*)} system via heavy anti-quark di-quark symmetry (HADS). In this work, we employ a contact-range effective field theory to systematically investigate the likely existence of molecules in these systems in terms of the hypothesis that X(3872) is a 1^{++}~D{bar{D}}^{*} bound state in the isospin symmetry limit, with some of the unknown low energy constants estimated using the light-meson saturation approximation. In the meson–meson system, a J^{PC}=2^{++}~{bar{D}}^{*}D^{*} molecule commonly referred to as X(4013) is reproduced, which is the heavy quark spin partner of X(3872). In the meson-baryon system, we predict two triply charmed pentaquark molecules, J^{P}=1/2^{-}~D^{*}Xi _{cc} and J^{P}=5/2^{-}~D^{*}Xi _{cc}^{*}. In the baryon-baryon system, there exist seven di-baryon molecules, J^{PC}=0^{-+}~{bar{Xi }}_{cc}Xi _{cc}, J^{PC}=1^{--}~{bar{Xi }}_{cc}Xi _{cc}, J^{PC}=1^{-+}~{bar{Xi }}_{cc}Xi _{cc}^{*}, J^{PC}=1^{--}~{bar{Xi }}_{cc}Xi _{cc}^{*}, J^{PC}=2^{-+}~{bar{Xi }}_{cc}Xi _{cc}^{*}, J^{PC}=2^{-+}~{bar{Xi }}_{cc}^{*}Xi _{cc}^{*}, and J^{PC}=3^{--}~{bar{Xi }}_{cc}^{*}Xi _{cc}^{*}. Among them, the J^{PC}=0^{-+}~{bar{Xi }}_{cc}Xi _{cc} molecule may contribute to the X(7200) state recently observed by the LHCb Collaboration, which implies that X(7200) can be related to X(3872) via HADS. As a byproduct, with the heavy quark flavor symmetry we also study likely existence of molecular states in the B^{(*)}{bar{B}}^{(*)}, {bar{B}}^{(*)}Xi _{bb}^{(*)}, and {bar{Xi }}_{bb}^{(*)}Xi _{bb}^{(*)} systems.

A high precision narrow-band neutrino beam: The ENUBET project

The knowledge of the initial flux, energy and flavor of current neutrino beams is the main limitation for a precise measurement of neutrino cross-sections. The ENUBET ERC project is studying a facility based on a narrow-band neutrino beam capable of constraining the neutrino fluxes normalization through the monitoring of the associated charged leptons in an instrumented decay tunnel. In ENUBET, the identification of large-angle positrons from [Formula: see text] decays at single particle level can potentially reduce the [Formula: see text] flux uncertainty at the level of 1%. This setup would allow for an unprecedented measurement of the [Formula: see text] cross-section at the GeV scale. This input would be highly beneficial to reduce the budget of systematic uncertainties in the next long baseline oscillation projects. Furthermore, in narrow-band beams, the transverse position of the neutrino interaction at the detector can be exploited to determine a priori with significant precision the neutrino energy spectrum without relying on the final state reconstruction. This contribution will present the advances in the design and simulation of the hadronic beam line. Special emphasis will be given to a static focusing system of secondary mesons that can be coupled to a slow extraction proton scheme. The consequent reduction of particle rates and pile-up effects makes the determination of the [Formula: see text] flux through a direct monitoring of muons after the hadron dump viable, and paves the way to a time-tagged neutrino beam. Time-coincidences among the lepton at the source and the neutrino at the detector would enable an unprecedented purity and the possibility to reconstruct the neutrino kinematics at source on an event-by-event basis. We will also present the performance of positron tagger prototypes tested at CERN beamlines, a full simulation of the positron reconstruction chain and the expected physics reach of ENUBET.