Meson Energy Research Articles

Planning an Experiment to Determine the Weinberg Running Angle for the J/ψ Meson Energy at the Charm-Tau Factory

Planning an Experiment to Determine the Weinberg Running Angle for the J/ψ Meson Energy at the Charm-Tau Factory

The measurement of the omega meson parameters with the CMD-3 detector at the electron-positron collider VEPP-2000

The cross section of the process e+ e– → π+ π– π0 was measured with the CMD-3 detector at the electron-positron collider VEPP-2000 in the ω meson energy region based on the data collected in 2013–2018 and corresponding to an integrated luminosity of 40 pb–1. The parameters of the ω-meson: Mω = 782.67 ± 0.01 ± 0.1 MeV, Γω = 8.56 ± 0.02 ± 0.07 MeV, σ0(ω → π+ π– π) = 1629 ± 3 ± 36 nb with the precision match or even exceeding the previous data are obtained.

Symmetry breaking radiative corrections to B to tensor meson form factors at large recoil

In heavy-to-light B decays, the heavy-quark/large-energy symmetry reduces the number of QCD form factors. At large final state meson energy, these form factors receive sizeable perturbative corrections. The hard-gluon vertex corrections are absorbed in the coefficients of soft-form factors, while the hard-spectator interactions generate symmetry-breaking corrections and end-point singularities. At an order of 1/m b, using the heavy-quark/large-energy symmetry, the end-point singularities can also be absorbed in the soft form factors, whereas the symmetry breaking corrections add separately to the form factors. In this work, we calculate these perturbative corrections for B → Tμ + μ − decays, with T representing the tensor mesons all having J P = 2+. We find that the values of the branching ratio (Br) and the zero-position of the forward–backward asymmetry of decay receive nearly 5% and 14% contributions, respectively, from these radiative corrections. Compared to these observables, the radiative corrections change the averaged longitudinal lepton polarization asymmetry (⟨P L⟩) by 13%. Therefore, prior to attributing any deviation from the SM predictions of these asymmetries as a hint of NP, one has to take into account the contributions of vertex and hard-spectator corrections.

Radiative B to axial-vector meson decays at NLO in soft-collinear effective theory

The rare decay B → Aγ, with A representing axial-vector mesons such as K 1(1270), K 1(1400), b 1(1300), a 1(1260), is studied at next-to-leading order (NLO) in soft collinear effective theory (SCET). The large outgoing meson energy encourages the study of the decay with an appropriate factorization scheme that separates the factorizable and non-factorizable parts systematically. We have analyzed the leading-power and diagrams that contribute to matching to SCETI. The new intermediate theory is matched onto SCETII and the running of SCETI operators is performed to sum large perturbative logarithms. The values of soft-overlap function ζ ⊥ for K 1(1270, 1400), a 1 and b 1 mesons are estimated from the light cone-sum-rules, and later using it the corresponding branching fractions for decays are calculated. We find that in case of B → K 1(1270, 1400)γ decays the results are in good agreement with their experimental measurements. Also the estimated values of the branching ratios of the B → (b 1, a 1)γ decays are potentially large to be measured at the LHCb and future B-factories.

Gauge-invariant decomposition of meson energy in two-dimensional QCD

This work is driven by our curiosity towards some basic questions in QCD: how is the energy of a moving hadron partitioned among different gauge-invariant sectors in QCD Hamiltonian? How is the energy of an massless pion separated between quark and gluon sectors, particularly in the soft pion limit? Is it possible to decompose the celebrated Gell-Mann-Oakes-Renner (GOR) relation? To what extent can we justify the quark potential model from the field-theoretical mass decomposition for heavy quarkonium? Due to limitation of contemporary nonperturbative tools, we do not yet know answers to these questions in realistic QCD. In this work, we take the 't Hooft model (two-dimensional QCD in large-$N$ limit) as a prototype model that mimics some essential aspects of the true QCD. We investigate the gauge-invariant energy decomposition of a flavor-neutral meson that can carry an arbitrary momentum (including stationary case), with meson species ranging from massless pion to bottomonium. All the aforementioned questions can be addressed satisfactorily within this model, in particular some unexpected patterns related to pion are discovered for the first time in two-dimensional QCD. We hope that our study can offer some useful clues and stimulation for future investigations on hadron energy decomposition in realistic QCD.

Fully coupled-channel study of K−pp resonance in a chiral SU(3)-based [formula omitted] potential

We have investigated the most essential kaonic nucleus “K−pp” as a resonant state of the K¯NN-πΣN- πΛN coupled-channel system using a chiral SU(3)-based K¯N potential. We treat the “K−pp” resonance adequately with a fully coupled-channel complex scaling method (full ccCSM). Self-consistency needs to be considered for the energy dependence of the chiral SU(3)-based potential. In the present study, we propose a simple prescription for the treatment of self-consistency, considering the averaged threshold and averaged binding energy of mesons. With this prescription, we have successfully found the self-consistent solutions of the “K−pp” three-body resonance. The results indicate that the “K−pp” system is bound rather shallowly. In particular, when the potential parameters are constrained with the latest K¯N scattering length, the binding energy and half of the mesonic decay width are obtained as 14–50 MeV and 8–19 MeV, respectively.

Utility of geometry in lattice QCD simulations

We propose a way to improve the resolution of the spatial momentum and the time interval for hadron propagators utilizing the lattice geometry. We demonstrate the validity of the method presenting results for pseudoscalar meson energies with and without finite momenta in a large-scale quenched QCD simulation. The method should be useful especially for master-field simulations.

Hadronic vacuum polarization and e+e− → μ+μ− cross section: Reanalysis with new precise data for σh with 4π final states included

The interference effect between leptonic radiative corrections and hadronic polarization functions is calculated via optical theorem for μ–pair production in vicinity of narrow resonances. Within seven most dominant exclusive channels of the production cross section σh(e+e− → hadrons) one achieves high acuracy which is necessary for the comparison with experiments. The result is compared with KLOE and KLOE2 experiments for μ−μ+ and μ−μ+γ productions at φ and ω/ρ meson energy.

Magnetic structure of vector mesons in lattice QCD

We have explored the response of the charged vector mesons on the external magnetic field. The g-factor of the charged vector ρ and K* mesons has been found. For the charged vector ρ meson the magnetic polarizability and hyperpolarizability have been calculated depending on the spin projection on the the magnetic field. We have estimated the intervals of the magnetic field for which the nonlinear terms in field give a significant contribution to the meson energy.

Mesons in strong magnetic fields: (I) General analyses

We study properties of neutral and charged mesons in strong magnetic fields |eB|≫ΛQCD2 with ΛQCD being the QCD renormalization scale. Assuming long-range interactions, we examine magnetic-field dependences of various quantities such as the constituent quark mass, chiral condensate, meson spectra, and meson wavefunctions by analyzing the Schwinger–Dyson and Bethe–Salpeter equations. Based on the density of states obtained from these analyses, we extend the hadron resonance gas (HRG) model to investigate thermodynamics at large B. As B increases the meson energy behaves as a slowly growing function of the meson's transverse momenta, and thus a large number of meson states is accommodated in the low energy domain; the density of states at low temperature is proportional to B2. This extended transverse phase space in the infrared regime significantly enhances the HRG pressure at finite temperature, so that the system reaches the percolation or chiral restoration regime at lower temperature compared to the case without a magnetic field; this simple picture would offer a gauge invariant and intuitive explanation of the inverse magnetic catalysis.

The magnetic polarizabilities andg-factor of the neutral and chargedρmesons in a strong magnetic field on the lattice

Study of the ground state energies of neutral and charged vector meson was performed in SU (3) lattice gauge theory in the strong abelian magnetic field. Our method allows us to distinguish the ground state energy of mesons for various spin projections on the axis of the external magnetic field . We are observe the splitting the ground state energy of ρ mesons depending on spin projections: for neutral ρ 0 meson with zero spin projection on the axis of the field ground state energy decreases, while the energies with non-zero spins increase with the field value. For charged ρ ± mesons we observe the agreement between Landau level picture and our data at magnetic field less then 0.6GeV 2 . The magnetic polarizabilities of vector mesons were found for the lattice volume 18 4 fitting the ground state energies. We found the g -factor of ρ ± in the chiral limit. This value is compatible with experimental determination and theoretical value from relativistic quark model.

Hadron interferences in the proton-induced coherentη-meson-production reaction on a scalar-isovector nucleus

The coherent $\eta$ meson energy $E_\eta$ distribution spectra in the proton nucleus reaction have been calculated to investigate the $\pi^0 - \eta$ mesons' interference, in addition to the study of resonance $N^*$ dynamics in the nucleus. The elementary reaction occurring in the nucleus is assumed to proceed as $ pN \to pN^* $; $ N^* \to N\eta $. Born terms in the intermediate state is also considered. In a scalar-isovector nucleus, this reaction occurs because of $\pi^0$ and $\eta$ meson exchange interactions for the forward going proton and $\eta$ meson; other meson exchange potentials do not contribute in this process. The sensitivity of the cross section to the hadron nucleus interactions, and the beam energy dependence of the cross section are studied for this reaction.

Overview of quarkonia and heavy flavour measurements by CMS

This writeup summarizes the recent CMS results on quarkonia measurements in pp, pPb and PbPb collisions at LHC. The excellent muon detection capability of CMS allows measurement of charmonia states at high transverse momentum (pT ) while thestates can be reconstructed starting at zero pT . The absolute and relative yields of different charmonia and bottomonia states modified in PbPb collisions (over pp collisions) are described. The vertexing capability of CMS enables measurement of B meson energy loss via its decay to J=ˆ. An overview of these measurements is given. How these measurements compare with other experiments at RHIC and LHC and have improved the understanding of heavy ion collisions has been discussed.

Medium induced Lorentz symmetry breaking effects in nonlocal Polyakov–Nambu–Jona-Lasinio models

In this paper we detail the thermodynamics of two flavor nonlocal Polyakov-Nambu-Jona-Lasinio models for different parametrizations of the quark interaction regulators. The structure of the model is upgraded in order to allow for terms in the quark selfenergy which violate Lorentz invariance due to the presence of the medium. We examine the critical properties, the phase diagram as well as the equation of state. Furthermore, some aspects of the Mott effect for pions and sigma mesons are discussed explicitly within a nonlocal Polyakov-Nambu-Jona-Lasinio model. In particular, we continued the meson polarization function in the complex energy plane and under certain approximations, we were able to extract the imaginary part as a function of the meson energy. We were not able to calculate the dynamical meson mass, and therefore resorted to a technical study of the temperature dependence of the meson width by replacing the meson energy with the temperature dependent spatial meson mass. Our results show that while the temperature behavior of the meson widths is qualitatively the same for a wide class of covariant regulators, the special case where the nonlocal interactions are introduced via the instanton liquid model singles out with a drastically different behavior.

Propagation of B mesons in the atmosphere

Collisions of cosmic rays in the atmosphere may create heavy hadrons. B mesons of energy above 108 GeV becomelong lived. Since their decay length grows larger than 10 km they tend to interact in the air before decaying. We show that the fraction of energy depositedin these interactions is much smaller than in proton and pioncollisions. We parameterize their elasticity and determine the average number of interactions and the atmosphericdepth at the decay point for different initial energies. We find that the profile of a 3 × 109 GeV bottom shower may be very different from the profileof a proton shower of the same energy, defining either a verydeep maximum, or two maxima, or other features that cannot be parameterized with a single Gaisser-Hillas function.Finally, we discuss under what conditions a bottom hadroninside the parent air shower may provideobservable effects.

Thermal dynamics of quarks and mesons $ \mathcal{N} = {2^*} $ Yang-Mills theory

We study the dynamics of quenched fundamental matter in \( \mathcal{N} = {2^*} \) supersymmetric large N c SU(N c ) Yang-Mills theory, extending our earlier work to finite temperature. We use probe D7-branes in the holographically dual thermalized generalization of the \( \mathcal{N} = {2^*} \) Pilch-Warner gravitational background found by Buchel and Liu. Such a system provides an opportunity to study how key features of the dynamics are affected by being in a non-conformal setting where there is an intrinsic scale, set here by the mass, m H , of a hypermultiplet. Such studies are motivated by connections to experimental studies of the quark-gluon plasma at RHIC and LHC, where the microscopic theory of the constituents, QCD, has a scale, ΛQCD. We show that the binding energy of mesons in the \( \mathcal{N} = {2^*} \) theory is increased in the presence of the scale m H , and that subsequently the meson-melting temperature is higher than for the conformal case.

Propagation in the atmosphere of ultrahigh-energy charmed hadrons

Charmed mesons may be produced when a primary cosmic ray or the leading hadron in an air shower collide with an atmospheric nucleon. At energies $\ensuremath{\ge}{10}^{8}\text{ }\text{ }\mathrm{GeV}$ their decay length becomes larger than 10 km, which implies that they tend to interact in the air instead of decaying. We study the collisions of long-lived charmed hadrons in the atmosphere. We show that $({\ensuremath{\Lambda}}_{c},D)$-proton diffractive processes and partonic collisions of any ${q}^{2}$ where the charm quark is a spectator have lower inelasticity than $(p,\ensuremath{\pi})$-proton collisions. In particular, we find that a $D$ meson deposits in each interaction just around 55% of the energy deposited by a pion. On the other hand, collisions involving the valence $c$-quark (its annihilation with a sea $\overline{c}$-quark in the target or $c$-quark exchange in the $t$ channel) may deposit most of the $D$ meson energy, but their frequency is low (below 0.1% of inelastic interactions). As a consequence, very energetic charmed hadrons may keep a significant fraction of their initial energy after several hadronic interactions, reaching much deeper in the atmosphere than pions or protons of similar energy.

The role of the form factor and short-range correlation in the relativistic Hartree-Fock model for nuclear matter

The role of the form factor and short-range correlation in nuclear matter is studied within the relativistic Hartree-Fock approximation. We take, first, the mean-field approximation for meson fields and obtain the fluctuation terms of mesons to be used for the Fock energies. We introduce form factors in the meson-nucleon coupling vertices to take into account the finite-size effect of the nucleon. We use further the unitary correlation operator method for the treatment of the short-range correlation. The form factors of the size ( \( \Lambda\) ∼ 1.0 -2.0GeV) of the nucleon-nucleon interaction cut down largely the contribution of the \( \rho\) -meson in the Fock term. The short-range correlation effect is not large but has a significant effect on the pion and \( \rho\) -meson energies in the relativistic Hartree-Fock approximation for nuclear matter.

Mathematical modeling of the strong coupling parameter based upon the gluon emission model for hadron production associated with vector meson decay

F. Close’s Gluon Emission Model (GEM), employed in conjunction with the general form for the absorption cross-section of the gluon involved in hadron production as associated with vector meson decay, has been shown to enable very accurate determinations of the widths of the K* (892) and the J (3097), a reasonably accurate determination of the width of the ϒ (1S), and, by construction, essentially exact determinations of the widths of the ρ (776) and the φ (1019). In determining the theoretical widths of the known vector mesons (and that of the K* (892)) via GEM, it is seen that said widths are proportional to the product of three main factors. The first such factor indicates the very significant electromagnetic component involved in vector meson (and K* (892)) decay, as said first factor involves the fourth power of the quark charge comprising the resonant state just prior to its decay. The second factor, a property of all quantum systems decaying directly to complete dissolution, is proportional to the mass of the resonant state raised to the negative third power. The third factor is the one of primary interest for the present work, as the third main factor involved in calculating the widths of vector mesons via the GEM is the strong coupling parameter, δ5 . As the charges of the quarks making up the ρ (776), the K* (892), the φ (1019), the J (3097), and the ϒ (1S) are all well-known, as are each of their masses, the GEM obviously may be employed to obtain δ s at a number of energies (E) over a wide range, viz., from E ≈ 700Mev ≈ the ρ -meson energy to E ≈ 10, 000 Mev ≈ the ϒ (1S) energy. Notably, we find that over the entire range of energy stated immediately above the strong coupling parameter may be described by one very simple function, viz., δ s ≈ 1.2[1n(E/50Mev)]-1 , interesting for two reasons: (1) the QCD “Scale Factor” (Λ) shows itself as Λ = 50 Mev from considerations of the GEM as evidenced by the behavior of δ s above; such value for Λ is quite small – only about one sixth of the average value of same as determined by the Particle Data Group (PDG) in recent times. Nevertheless, formal gauge theory does consider Λ to be an arbitrary parameter; its usefulness, therefore, no matter the value assumed for it, may be ascertained in the full context in which it is employed. (2) At the low end of the energy scalementioned above (i.e., E ≈ 700 Mev) the strong coupling parameter has a value (as determined via the GEM) of roughly 0.45. Even at the high end (i.e., E ≈ 10, 000 Mev) its associated value is about 0.23. Hence, the entire range of energy overwhich δ s is determined via the GEM cannot be considered as a range of energy over which δ s may be determined accurately via perturbative methods – certainly not any such to only the first order. Yet, the GEM yields a very simple form for the strong coupling parameter, and, as will be shown, it meets the test of experiment to a high degree of accuracy over said range. Beyond the ϒ (1S) energy, δ s as equal to 1.2[1n(E/50Mev)]-1 , becomes no longer viable. A simplemathematical “smoothing” function is derived to “blend” δ s as determined via the GEM in its “low energy range” into its asymptotic, ultra-high energy behavior. We evaluate δ s at the Z -boson mass, such evaluation having become a popular ldquo;standard” over the recent years. We find a statistical match to the experimental findings reported for such in each of two excellent review articles pertaining to the status of the strong coupling parameter – one authored by Michael Schmelling and the other by C. Amsler et al. (available on the PDG’s www pages). Further, we show that unless a given experiment agrees to within 10% of the GEM determination of δ s at a given energy, there is a less than 10% chance that such experiment will yield the presently accepted value of δ s associated with the Z mass.

Neutral meson oscillations and equivalence principle for particles and antiparticles

Oscillations of neutral meson (K0-\( \overline {K^0 } \), D0-\( \overline {D^0 } \), and B0-\( \overline {B^0 } \) are extremely sensitive to the meson and antimeson energies at rest. This energy is determined as mc2—with the corresponding inertial mass—and as the energy of gravitational interaction. Assuming that the CPT theorem is correct for inertial masses and estimating the gravitational potential for which the largest contribution originates from the field of the galaxy center, we obtain the estimate from experimental data on K0-\( \overline {K^0 } \) oscillations: $$ \left| {\left( {\frac{{m_g }} {{m_i }}} \right)_{K^0 } - \left( {\frac{{m_g }} {{m_i }}} \right)_{\overline {K^0 } } } \right| \leqslant 8 \times 10^{ - 13} , at C.L. = 90\% $$ . This estimate is model dependent; in particular, it depends on the method used to estimate the gravitational potential. An analysis of K0-\( \overline {K^0 } \), D0-\( \overline {D^0 } \), and B0-\( \overline {B^0 } \) oscillations provides weaker but model independent estimates which, in particular, eliminate the possibility of antigravity for antimatter.