Search

The visible Universe is largely characterised by a single mass-scale; namely, the proton mass, $m_p$. Contemporary theory suggests that $m_p$ emerges as a consequence of gluon self-interactions, which are a defining characteristic of quantum chromodynamics (QCD), the theory of strong interactions in the Standard Model. However, the proton is not elementary. Its mass appears as a corollary of other, more basic emergent phenomena latent in the QCD Lagrangian, e.g. generation of nuclear-size gluon and quark mass-scales, and a unique effective charge that may describe QCD interactions at all accessible momentum scales. These remarks are explained herein; and focusing on the distribution amplitudes and functions of $\pi$ and $K$ mesons, promising paths for their empirical verification are elucidated. Connected therewith, in anticipation that production of $J/\psi$-mesons using $\pi$ and $K$ beams can provide access to the gluon distributions in these pseudo-Nambu-Goldstone modes, predictions for all $\pi$ and $K$ distribution functions are provided at the scale $\zeta=m_{J/\psi}$., Comment: 10 pages, 7 figures, 3 tables. Commissioned by and to appear as a Feature Article in the Bulletin of the Association of Asia Pacific Physical Societies (AAPPS)

Semileptonic decays of vector mesons $$\rho $$ , $$\omega $$ , ϕ into a pion and lepton pair $${{e}^{ + }}{{e}^{ - }},{{\mu }^{ + }}{{\mu }^{ - }}$$ are described in the chiral Nambu–Jona–Lasinio (NJL) model. Mixing of $$\omega $$ with ϕ is taken into account in a description of vector ϕ meson decay. Direct production via a photon field and production with the participation of intermediate vector mesons $$\rho $$ or $$\omega $$ are taken into account in the production of $${{l}^{ + }}{{l}^{ - }}$$ lepton pairs. The total and differential widths are compared with an experiment. Predictions for $$\rho \to \pi \,\,[{{e}^{ + }}{{e}^{ - }},{{\mu }^{ + }}{{\mu }^{ - }}]$$ and $$\phi \to \pi {{\mu }^{ + }}{{\mu }^{ - }}$$ decays are also given.

We revisit the calculation of the strong couplings D∗Dπ and B∗Bπ from the QCD light-cone sum rules using the pion light-cone distribution amplitudes. The accuracy of the correlation function, calculated from the operator product expansion near the light-cone, is upgraded by taking into account the gluon radiative corrections to the twist-3 terms. The double spectral density of the correlation function, including the twist-2, 3 terms at $$ \mathcal{O}\left({\alpha}_s\right) $$ O α s and the twist-4 LO terms, is presented in an analytical form for the first time. This form allows us to use various versions of the quark-hadron duality regions in the double dispersion relation underlying the sum rules. We predict $$ {g}_{D^{\ast } D\pi}={14.1}_{-1.2}^{+1.3} $$ g D ∗ Dπ = 14.1 − 1.2 + 1.3 and $$ {g}_{B^{\ast } B\pi}={30.0}_{-2.4}^{+2.6} $$ g B ∗ Bπ = 30.0 − 2.4 + 2.6 when the decay constants of heavy mesons entering the light-cone sum rule are taken from lattice QCD results. We compare our results with the experimental value for the charmed meson coupling and with the lattice QCD calculations.

Parameterizations of the electromagnetic form factors of $$f_{1}(1285)$$ meson are considered. Using these parameterizations theoretical predictions for the total cross section of the direct $$f_{1}(1285)$$ meson production in $$e^{+}e^{-}$$ annihilation, $$\sigma(e^{+}e^{-}\to f_{1}(1285))$$ , are obtained.

The modification of the spectral function of vector mesons in nuclear matter is predicted in many theoretical models. However, the existing experimental results for testing these models are contradictory. Possible effects of the modification of the mass and width of ω mesons produced in the collisions of 7-GeV/c positively charged mesons with C, Be, Al, Cu, Sn, and Pb nuclear targets have been sought in the Hyperon-M experiment. The measured mass and width of ω mesons produced on the indicated nuclei are in agreement with each other with a high accuracy, which does not confirm the theoretical models predicting modification of the mass and/or width of the ω meson in nuclear matter.

The rare leptonic decays Bs, d → l+l− (l = e, μ, τ) present an important base to analyse the flavour structure of the standard model (SM) and also become a potential source to dig out possible signatures of new physics (NP) beyond the SM. The muonic decay Bs, d → μ+μ− has been observed at the LHC as well as the upper limits of branching ratios for other Bs, d → l+l− decays have been updated recently. In this paper, using the χ2 fitting method we have studied all these decay channels considering the effect of a Z′ boson. Our analysing method reproduces the result of the muonic channel of Bs meson, hence we have used the same strategy for the other Bs, d → l+l− decays.

We perform a SU(3) analysis for both semi-leptonic and non-leptonic heavy meson weak decays into a pseudoscalar meson and a fully-light tetraquark in 10 or 27 representation. A reduction of the SU(3) representation tensor for the fully-light tetraquarks is produced and all the flavor components for each representation tensor are listed. The decay channels we analysis include $B/D \to U/T~P~l\nu$, $B/D \to U/T~P $ and $B_c \to U/T~P/D$, with $U/T$ represents a fully-light tetraquark in 10 or 27 representation and $P$ is a pseudoscalar meson. Finally, among these results we list all the golden decay channels which are expected to have more possibilities to be observed in experiments., Comment: 32 pages, 5 figures

We consider the time-dependent analysis of Bd→ KSℓℓ taking into account the time-evolution of the Bd meson and its mixing into $$ {\overline{B}}_d $$ B ¯ d . We discuss the angular conventions required to define the angular observables in a transparent way with respect to CP conjugation. The inclusion of time evolution allows us to identify six new observables, out of which three could be accessed from a time-dependent tagged analysis. We also show that these observables could be obtained by time-integrated measurements in a hadronic environment if flavour tagging is available. We provide simple and precise predictions for these observables in the SM and in NP models with real contributions to SM and chirally flipped operators, which are independent of form factors and charm-loop contributions. As such, these observables provide robust and powerful cross-checks of the New Physics scenarios currently favoured by global fits to b → sℓℓ data. In addition, we discuss the sensitivity of these observables with respect to NP scenarios involving scalar and tensor operators, or CP-violating phases. We illustrate how these new observables can provide a benchmark to discriminate among the various NP scenarios in b → sμμ. We discuss the extension of these results for Bs decays into f0, η or η′.

By combining the variational principle with Heisenberg uncertainty principle in an effective Hamiltonian for heavy flavored mesons, we in- troduce a framework to estimate masses and radii of these states from an analytical constraint. In a novel manner, a model for quark velocity and a model for quark momentum width are introduced. These kinemat- ical model parameters are obtained as analytical functions of inter quark separation in heavy quarkonia. The values of such quark parameters are then used in the calculation of S -wave annihilation decay rates of \bar{ c} c and\bar{ b} b . To test the accuracy of our technique we first calculate the spin av eraged masses, scalar radii and annihilation decay rates of charmonium and bottomonium without and with relativistic corrections by solving the Schrodinger wave equation with the appropriate parametrization of the Song-Lin potential. The Schrodinger wave equation is solved numerically with the matrix Numerov method and we observe a good agreement with the experimental measurements and other theoretical calculations and ex tract strong running coupling constant for \bar{ c} c and \bar{ b} b systems. In non rel- ativistic settings, heavy meson spectra have been obtained and extended to rather higher excited states within our framework by using bare masses of c and b quarks which we have extracted from analysis of experimental data

In the present work, the form factors of $$B_{(s)}$$ B ( s ) to light P-wave tensor mesons ($$a_2(1320)$$ a 2 ( 1320 ) , $$K^*_2(1430)$$ K 2 ∗ ( 1430 ) , $$f_2(1270)$$ f 2 ( 1270 ) , $$f^\prime _2(1525)$$ f 2 ′ ( 1525 ) ) are calculated via the light cone sum rules (LCSR) in the framework of heavy quark effective field theory (HQEFT). Firstly, the expressions of form factors in terms of the light cone distribution amplitudes (DAs) of tensor mesons are derived via the LCSR at the leading order of heavy quark expansion. It is found that the penguin type form factors can be obtained directly from the corresponding semileptonic ones, which is similar to the case of S-wave mesons. Considering the light tensor meson DAs to twist-3, we give the numerical results of form factors systematically. As applications, we investigate the branching ratios, longitudinal polarization fractions and forward-backward asymmetries of relevant semileptonic decays induced by charged current and flavor changing neutral current (FCNC) separately. Our results may be tested by more precise experiments in the future.

This paper purposes an explanation for the recent evidence for the violation of lepton universality in beauty-quark decays at CERN’s Large Hadron Collider. A beauty meson (B+) transforms into a strange meson (K+) with the emission of either electron-positron (e+e-) or muon-antimuon (μ+μ-). The ratio (RK) of branching fractions for B+ → K+μ+μ- and B+→ K+e+e- decays is measured to be RK = 0.846 instead of 1 in the violation of lepton universality in the Standard Model. This paper proposes that the violation is derived from the binary isotope mixture of two beauty-quarks, b7 (4979 MeV mass) and b8 (143,258 MeV mass) whose masses are calculated from the periodic table of elementary particles. b7 is the observable B, while b8 is the hidden B to preserve the generation number symmetry between the three lepton family generations and the three quark family generations in the Standard Model. The preservation of the generation number symmetry forbids b8 to decay into K+μ+μ-. In the transition state involving the virtual particles (γ, W± and Z°) before the decay, b7 and b8 emerge to form the binary isotope mixture from B. The rates of emergence as the rates of diffuse in Graham’s law of diffusion are proportional to inverse square root of mass. The rate ratio between b8/b7 is (4979/143,258)1/2 = 0.1864. Since b7 decays into K+, e+e-, and μ+μ-, while b8 decays into K+, e+e-, and forbidden μ+μ-, the calculated ratio (RK) of branching fractions for B+→ K+μ+μ- and B+→ K+e+e- is 0.5/(0.1864 × 0.5+ 0.5) = 0.843 in excellent agreement with the observed 0.846. The agreement between the calculated RK and the observed RK confirms the validity of the periodic table of elementary particles which provides the answers for the dominance of matter over antimatter, dark-matter, and the mass hierarchy of elementary particles.

A preliminary result of an analysis of the process $$e^{+}e^{-}\to K_{S}K^{\pm}\pi^{\mp}$$ whose cross section was measured in the range of center-of-mass collision energies between 1.2 and 2 GeV is presented. The analysis is based on the data sample corresponding to an integrated luminosity of about 120 pb $${}^{-1}$$ accumulated with the CMD-3 detector at the VEPP-2000 electron–positron collider. A procedure for separating signal events is developed, and the dominance of the $$K^{*}(892)K$$ neutral mode is confirmed. The cross section for the process $$e^{+}e^{-}\to K_{S}K^{\pm}\pi^{\mp}$$ is measured to a precision higher than that in earlier experiments. This permits improving the accuracy in measuring the mass and width of the $$\phi$$ (1680) meson, testing the accuracy of the isotopic relations, and more accurately calculating the hadronic contribution to the muon anomalous magnetic moment ( $$g-2$$ ).

An assumption that all the six flavour quarks are attributed to be the components of a same, a common isospin multiplets space named STS is proposed. Base on Pauli Exclusion Principle, every quark is assigned to different flavour marks in STS. Every flavour quark possesses its own colour spectral line array specially appointed. The collection of colour spectral line arrays of the six flavour quarks constructs together the CSDF, Colour Spectrum Diagram of Flavour, further baryons and mesons could be constructed from CSDF. STS, Spin Topological Space is a math frame with infinite dimensional matrix representation for spin angular momentum. Flavours is an isospin angular momentum coupling phenomena of the three-colour-quarks.

We investigate light meson mass spectra with massive u, d, and s quarks and with a spin effect under a bound system in 3 + 1 dimensional QCD by using the first order perturbation correction. In the process of determining charged kaon and neutral kaonmasses, we obtain masses of u, d, and s quarks that are slightly smaller than the currently accepted values. Using these masses, we obtain light meson mass spectra that includes mass splitting of charged and neutral kaons and ρ mesons. The most interesting of our results is that the pion mass remains unchanged even though u, d, and s quarks become massive.

The present article develops a model initially published in ref. [1]. It is a quasi-classical quantum model of composite particles with ultra-relativistic (UR) constituents (leptons and quarks). The model is used to calculate the mass energy of three composite particles: a UR tauonium, a UR bottomonium and a UR leptoquarkonium. The result is that these three hypothetic particles have masses close to 125 GeV: the Higgs boson mass energy. These results are recalled in the present article. Then the model is extended to calculate the mass energy of pi-mesons, W and Z bosons. Finally, the model provides a hypothesis on dark matter.

The charge-exchange reaction $${{\pi }^{ - }}p \to n\omega (783)\phi (1020)$$ , $$\omega \to {{\pi }^{ + }}{{\pi }^{ - }}{{\pi }^{0}}$$ , $$\phi \to {{K}^{ + }}{{K}^{ - }}$$ is studied on the upgraded VES facility (U-70, Protvino) upon the interaction of a 29 GeV/c meson beam with a beryllium target. There are 905 events of the $$\omega \phi $$ system selected. The distribution over the invariant mass of the $$\omega \phi $$ system, $${{M}_{{\omega \phi }}}$$ , shows a near-threshold signal with a mass of M ~ 1.9 GeV/c2. A five-particle partial wave analysis (PWA) reveals that the scalar state ( $${{J}^{{PC}}} = {{0}^{{ + + }}}$$ ) dominates in this mass region. Under the assumption of the resonant nature of the signal, the following values of its mass and width are obtained: M = 1819 ± 27 MeV/c2 and Γ = 167 ± 18 MeV/c2.

Measurements of φ-mesons in such small colliding systems as p + Au and He + Au are used to study the effects of cold nuclear matter, in order to separate ones caused by the formation of quark–gluon plasma from those produced by cold nuclear matter in collisions between heavy ions. The effects of cold nuclear matter are multiple parton scattering, loss of the energy of partons in the initial state, dynamic shadows, and the Cronin effect.

Within the three-flavor PNJL and EPNJL chiral quark models we have obtained pseudoscalar meson properties in quark matter at finite temperature $T$ and baryochemical potential $\mu_B$. We compare the meson pole (Breit-Wigner) approximation with the Beth-Uhlenbeck (BU) approach that takes into account the continuum of quark-antiquark scattering states when determining the partial densities of pions and kaons. We evaluate the kaon-to-pion ratios along the (pseudo-)critical line in the $T-\mu_B$ plane as a proxy for the chemical freezeout line, whereby the variable $x=T/\mu_B$ is introduced that corresponds to the conserved entropy per baryon as initial condition for the heavy-ion collision experiments. We present a comparison with the experimental pattern of kaon-to-pion ratios within the BU approach and using $x$-dependent pion and strange quark potentials. A sharp "horn" effect in the energy dependence $K^+/\pi^+$ ratio is explained by the enhanced pion production at energies above $\sqrt{s_{NN}}=8$ GeV, when the system enters the regime of meson dominance. This effect is in line with the enhancement of low-momentum pion spectra that is discussed as a precursor of the pion Bose condensation and entails the occurrence of a nonequilibrium pion chemical potential of the order of the pion mass. We elucidate that the horn effect is not related to the existence of a critical endpoint in the QCD phase diagram., Comment: 20 pages, 7 figures

A holographic model of probe vector mesons (quarkonia) is presented, where the dynamical gravity-dilaton background is adjusted to the thermodynamics of 2 +1 flavor QCD with physical quark masses. The vector meson action is modified to account for various quark masses. We focus on the $\Phi$, $J/\psi$ and $\Upsilon$ meson melting in agreement with hadron phenomenology in heavy-ion collisions at LHC, that is the formation of hadrons at the observed freeze-out temperature of 155 MeV., Comment: Contribution to the 40th Max Born Symposium

We calculate the relativistic Fermi liquid parameters (RFLPs) for the description of the nuclear saturation energy using a chiral effective Lagrangian. Analytical expressions of Fermi liquid parameters (FLPs) are presented both for the direct and exchange contributions by retaining the meson masses. We present a comparative study of perturbative calculation with mean field results. The FLPs, so determined, are then used to calculate the chemical potential, energy densities, and binding energy for dense nuclear matter interacting via the exchange of σ, ω, and π mesons. In addition, we also estimate bulk quantities like incompressibility and first sound velocity in terms of RFLPs for dense nuclear matter.

On the statistics of ~1.7 × 108 interactions of positively charged kaons on copper nuclei, coherent events of the K+π0 system production are selected. The cross sections for the Coulomb and coherent strong components and their interference in the region of the K*(892) meson are measured. The partial width for the decay K*(892) → K+γ is determined. When studying the mass spectrum of the K+π0 system, an effect which can be interpreted as the interference of the chiral anomaly and the K*(892) s-channel amplitudes is found. This gives an estimate for the ratio of the observed amplitude of the chiral anomaly to the theoretical one: Aexp/Ath = 0.9 ± 0.24(stat.) ± 0.3(syst.).

Invariant transverse momentum spectra and nuclear modification factors of K*(892) mesons are measured in Cu + Au collisions at the energy of 200 GeV. The measurements are performed in five centrality bins in the transverse momentum range of 2.0 to 5.75 GeV c–1 in the PHENIX experiment at RHIC. The nuclear modification factors are compared to the earlier PHENIX data obtained for symmetric Cu + Cu systems at $$\sqrt {{{s}_{{NN}}}} $$ = 200 GeV. The nuclear modification factors of K* mesons in Cu + Cu and Cu + Au collisions at identical Npart (number of participants) have a similar shape.

A method of employing semileptonic $$K^{0}$$ -meson decays is proposed. Combined with a time-dependent analysis of decay parameters of initially produced combination, it permits extracting $$K^{0}{-}\bar{K}^{0}$$ . These measurements could be applied to heavy-flavor physics problems—in particular, charm physics. A feasibility study for the strong-phase difference in charm decays is performed.

The first observation of two excited states of the $$B^{+}_{c}$$ is presented together with the measurements of the $$B_{c}(2S)^{+}$$ mass and the mass difference $$M(B_{c}^{\ast+})-M(B_{c}^{+})-[M(B_{c}(2S)^{\ast+})-M(B_{c}(2S)^{+})]$$ . Additionally, we present a study of $$\Lambda^{0}_{b}$$ -baryon excited states, namely, $$\Lambda_{b}(5912)^{0}$$ , $$\Lambda_{b}(5920)^{0}$$ , $$\Lambda_{b}(6146)^{0}$$ , and $$\Lambda_{b}(6152)^{0}$$ , decaying into $$\Lambda^{0}_{b}\pi^{+}\pi^{-}$$ . The two analyses are carried out using the data collected in proton-proton collisions at a centre-of-mass energy of 13 TeV by the CMS experiment and corresponding to an integrated luminosity of about 140 fb $${}^{-1}$$ .

Prospects of a further investigation of excited states of $$B_{c}$$ mesons are discussed. Preliminary estimates of the relative yield of $$D$$ -wave states of $$B_{c}$$ mesons at the LHC are presented for the first time.

Spectrum, radial wave functions at origin, decay constants, weak decay widths, life-time, and branching ratios for radially excited conventional and hybrid $$B_{c}$$ mesons are derived within non-relativistic quark model framework employing Schrodinger equation by shooting method. Calculated results are compared with available theoretical results and experimental observations. This work may help in identifying the new discovered $$B_{c}$$ meson states at CDF, LHCb, and ATLAS.

The Super Charm-Tau Factory project proposed at Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, in Novosibirsk is discussed. An electron–positron collider with the luminosity of $$10^{35}$$ cm $${}^{-2}$$ s $${}^{-1}$$ and energies of 2 to 6 GeV in the beam center-of-mass frame and with a state-of-the-art particle detector arranged at the point of $$e^{+}e^{-}$$ interaction will permit studying, at a new precision level, the physics of charmonium, exotic charmonium-like states, charmed mesons and baryons, and the tau lepton, as well as the production of light hadrons in $$e^{+}e^{-}$$ -annihilation processes and in two-photon processes. A longitudinal polarization of the electron beam at the interaction point will provide a number of competitive advantages to the Super Charm-Tau Factory in relation to Super B factories such as Belle II and LHCb.

Nuclear modification factors of φ mesons produced in Cu + Au and U + U collisions at cms energies of $$\sqrt {{{s}_{{NN}}}} $$ = 200 and 192 GeV, respectively, are studied using data from the PHENIX experiment. The nuclear modification factors of φ mesons produced in U + U and Cu + Au collisions are compared to results obtained in Au + Au and Cu + Cu systems, and to those of the π0, η, KS, and ω mesons produced in the same U + U and Cu + Au collisions.

We correct a number of figures in [1], in which the PYTHIA MC result of secondary π0 mesons was displayed wrongly due to a missing factor of 2. Scrutinizing the corrected data-MC comparsion, we review and model the trigger condition used in the LEBC-EHS experiment, and present an improved data-MC comparison.

In this work, the relative Underlying event (UE) transverse multiplicity activity classifier ($$R_\mathrm{{T}}$$ R T ) is used to study the strange and multi-strange hadron production in proton-proton collisions. Our study with $$R_\mathrm{{T}}$$ R T would allow to disentangle these particles, which are originating from the soft and hard QCD processes. We have used the PYTHIA 8 Monte-Carlo (MC) with a different implementation of color reconnection and rope hadronization models to demonstrate the proton-proton collisions data at $$\sqrt{s}~$$ s = 13 TeV. The relative production of strange and multi-strange hadrons are discussed extensively in low and high transverse activity regions. In this contribution, the relative strange hadron production is enhanced with increasing $$R_\mathrm{{T}}$$ R T . This enhancement is significant for the strange baryons as compared to mesons. In addition, the particle ratios as a function of $$R_\mathrm{{T}}~$$ R T confirm the baryon enhancement in new Color Reconnection (newCR), whereas the Rope model confirms the baryon enhancement only with strange quark content. Experimental confirmation of such results will provide more insight into the soft physics in the transverse region, which will be useful to investigate various tunes based on hadronization and color reconnection schemes.

Results are presented from measuring nuclear modification factors RAA of the π0, η, KS, and ω mesons produced in systems of Cu + Au and U + U collisions at cms energies of $$\sqrt {{{s}_{{NN}}}} $$ = 200 and 192 GeV, respectively, in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). The RAA values are found not to depend on the type of neutral meson and to vary in the ~0.4–0.6 and ~0.2–0.3 intervals for central Cu + Au and U + U collisions, respectively. The mean RAA values for different collision systems (Au + Au, Cu + Cu, Cu + Au, and U + U) are found to coincide within the measuring errors when estimated at comparable values of collision energy $$\sqrt {{{s}_{{NN}}}} $$ , and of the number of nucleons participating in a nucleus–nucleus collision, Npart.

Based on an integrated luminosity of 1.61 fb$^{-1}$ $e^+e^-$ collision data collected with the KLOE detector at DA$\Phi$NE, the Frascati $\phi$-factory, a search for the $P$- and $CP$-violating decay $\eta\to\pi^{+}\pi^{-}$ has been performed. Radiative $\phi\to\eta\gamma$ decay is exploited to access the $\eta$ mesons. No signal is observed in the $\pi^{+}\pi^{-}$ invariant mass spectrum, and the upper limit on the branching fraction at 90\% confidence level is determined to be ${\mathcal B}(\eta\to\pi^{+}\pi^{-}), Comment: 11 pages, 3 figures

In this work we investigate the implication of low-energy precision measurements on the quark-lepton charged currents in general neutrino interactions with sterile neutrinos in effective field theories. The physics in low-energy measurements is described by the low-energy effective field theory extended with sterile neutrinos (LNEFT) defined below the electroweak scale. We also take into account renormalization group running and match the LNEFT onto the Standard Model (SM) effective field theory with sterile neutrinos (SMNEFT) to constrain new physics (NP) above the electroweak scale. The most sensitive low-energy probes are from leptonic decays of pseudoscalar mesons and hadronic tau lepton decays in terms of precise decay branching fractions, the lepton flavor universality and the Cabibbo-Kobayashi-Maskawa (CKM) unitarity. We also consider other constraints including nuclear beta decay. The constraints on charged current operators are generally stronger than the ones for quark-neutrino neutral current operators. We find that the most stringent bounds on the NP scale of lepton-number-conserving and lepton-number-violating operators in SMNEFT are 74 (110) TeV and 9.8 (13) TeV, respectively, for the operators with down (strange) quark., Comment: 34 pages, 12 tables. Version accepted by JHEP

Protons and neutrons are not fundamental particles, instead are formed by quarks. Thousands of multi-quark particles were discovered in cosmic rays or particle accelerators. However, within the past decades after the quark model was proposed by Gell-Mann and Zweig, only two categories of strongly interacting particles were known: Baryons (such as protons and neutrons) that are made from three quarks, and mesons that are made from one quark and one antiquark. But what other configurations of quarks and antiquarks can form a particle? This question is theoretically difficult to answer. Yet new particles with different combinations of quarks keep popping up in experiments. In 2015, the best evidence for the existence of an exotic type of particle called as pentaquark, a never-before-seen formation of five quarks, was discovered by physicists working on the Large Hadron Collider beauty (LHCb) experiment at European Organization for Nuclear Research (CERN). The detection of this particle is a major breakthrough in learning more about the nature of the strong forces that bound quarks together. In a sample of about 26000 Λ b 0 → J/ψK − p decays collected by the LHCb detector, a significant enhancement structure was observed in the J/ψp mass distribution. The pentaquark signal populated well separatedly from those contributions of Λ * → K − p on the “Dalitz” plot using the K–p and J/ψp invariant mass-squared as independent variables. The amplitude analysis revealed two pentaquark states were needed to describe dataset. They were formally named as Pc(4450)+ and Pc(4380)+ with statistical significances greater than 9 standard deviations: One has a mass of (4449.8 ±1.7±2.5) MeV and a width of (39 ±5±19) MeV, while the other is wider, with a mass of (4380 ±8±29) MeV and a width of (205 ±18±86) MeV. Both pentaquarks that LHCb physicists observed decaying strongly into a J/ψ particle and a proton, must have a minimal quark content of c c ¯ uud, and thus are charmonium pentaquarks. Recently the analysis has been reoptimized based on the data collected to date. A sample of 2.5×105 Λ b 0 → J/ψK − p decays was selected, nine times more than those used in the previous analysis. A new pentaquark state Pc(4312) was discovered with a mass near 4312 MeV. The Pc(4450) state was found to be the superposition of two nearby states at 4440 and 4457 MeV respectively. In an attempt to interpret the discoveries by the LHCb experiment, the pentaquark was conjectured as a tightly bound system of all five quarks, or a weakly bound “molecular” system of a baryon and a meson. Accurate description of a multi-quark system using the theory of the strong force and quantum chromodynamics (QCD) is an extremely difficult problem. In fact, there are many combinations how five quarks are bound within the pentaquark. The five quarks could be tightly bound within a single structure, for example. Another possibility is that a quark and an antiquark are bound together to form a meson and the remaining three quarks form a baryon. The meson and baryon could then be bound to each other to create a structure resembling a subatomic molecule. Exploring the structure of pentaquarks as one of novel frontiers in high energy physics paves a new era to study the nature of strong interactions, which is an important stepping-stone in our good understanding of the strong force, the least well known of the four forces in nature.

The coherent photoproduction of $$\pi^{0}\pi^{0}$$ and $$\pi^{0}\eta$$ on nuclei in the mass-number region of $$A\leqslant 7$$ is studied systematically over the range between the threshold and the laboratory photon energy of $$E_{\gamma}=2$$ GeV. The amplitude for photoproduction on nuclei is constructed on the basis of the impulse approximation with allowance for a number of processes responsible for meson–nucleus final-state interaction. The pion-rescattering processes $$\pi N\to\pi N$$ and $$\pi N\to\eta N$$ occurring on spectator nucleons, $$\pi^{+/-}\pi^{0}\pi^{0}$$ and $$\pi^{+/-}\pi^{0}\eta$$ production followed by $$\pi^{+/-}$$ absorption by spectator nucleons, and three-body $$\pi$$ –NN and $$\eta$$ –NN interactions are described for the first time within a unified microscopic approach.

Inspired by recent measurement of possible fully charmed tetraquarks in LHCb Collaboration, we investigate the mass spectra of fully heavy tetraquarks $QQ \bar Q \bar Q$ in an extended relativized quark model. Our estimations indicate that the broad structure around 6.4 GeV should contain one or more ground $cc \bar c \bar c$ tetraquark states, while the narrow structure near 6.9 GeV can be categorized as the first radial excitation of $cc \bar c \bar c$ system. Moreover, with the wave functions of the tetraquarks and mesons, the strong decays of tetraquarks into heavy quarkonium pair are qualitatively discussed, which can be further checked by the LHCb and CMS Collaborations., Comment: 7 pages, 3 figures, comments and suggestions are welcome

We present an analytic calculation of Branching Ratio (BR) and Charge–Parity (CP) violating asymmetries of the $$B_{s}^{0}$$ -meson decay into the two light vectors $$\rho^{0}\phi$$ . In doing this we calculate the helicity amplitude of the present decay in the framework of QCD factorization approach. We find the BR of $$B_{s}^{0}\rightarrow\rho^{0}\phi=(0.26\pm 0.04)\times 10^{-6}$$ which is in agreement with the recent theoretical predictions and experimental measurements. We also calculate the direct CP violation, CP violation in mixing and CP violation due to interference which are $$0.107\pm 0.013$$ , $$0.256\pm 0.036$$ , and $$0.960\pm 0.009$$ , respectively.

We construct the D4/D8 brane configuration in the Witten-Sakai-Sugimoto model by introducing a pair of heavy flavour brane with a heavy-light open string. The multiplets created by the heavy-light string acquire mass due to the finite separation of the heavy and light flavour branes thus they could be identified as the heavy-light meson fields in this model. On the other hand the glueball field is identified as the gravitational fluctuations carried by the close string in the bulk, so this model is able to describe the interaction of glueball and heavy-light meson through the open-close string interaction in gauge-gravity duality. We explicitly derive the effective action for the various glueballs and heavy-light mesons then numerically evaluate the associated coupling constants. Afterwards the decay widths of various glueballs to the lowest heavy-light meson, which is identified as $D^{0}$ meson, are calculated by using our effective action. This work extends the previous investigations of glueball in holographic QCD and it is also a further prediction of glueball-meson interaction., Comment: 33 pages, 2 figures, 2 tables

New experimental data on the multifragmentation of carbon nuclei that is initiated by the photoproduction of neutral pions and eta mesons are discussed. The novelty is associated with the exclusive character of the processes being studied, in which case a determination of partial meson-photoproduction reactions is followed by an analysis of complementary particles for coincidence. The experiment being discussed was performed by the GRAAL (GRenoble Accelerateur Anneau Laser) Collaboration in a beam of 500- to 1500-MeV Compton photons. The possibility of performing new experiments within the BGO-OD Collaboration (Bonn, Germany) is considered. A new method for studying the interaction of short-lived mesons with nuclei on the basis of detecting cascade recoil nucleons is proposed.

Journal of high energy physics 2020(8), 146 (2020). doi:10.1007/JHEP08(2020)146, Published by SISSA, [Trieste]

In this study, the fragmentation functions (FF) for the production of Bc meson (1S and 2S-states) in c → Bc and b → Bc processes at the leading order (LO) and next-to-leading order (NLO) are derived. Moreover, some technical details about the contributions of the first two sets, n = 1 and n = 2 of S-wave states currents in dimensional regularization scheme are discussed. The differences between the fragmentation functions indicated that the NLO corrections enhanced the fragmentation probability (FP). Also, the probability of production of Bc meson in 1S state and in b → Bc process was more than the one in 1S state and c → Bc process.

The conventional nuclear forces at low energies are described by NN-potentials that arise within the framework of the classical mesonic theory as a consequence of the interchange of mesons. Under the situation the mentioned NN-potentials depend on the mesonic masses as parameters. From the point of view of quantum chromodynamics (QCD), however, the mesons and nucleons are composed of quark-gluon configurations and are the result of a confinement mechanism, i.e., the quark-gluonic hadronization into mesons (nucleons). Hence the above mesonic masses should be some functions of quark-gluonic degrees of freedom. When using the confinement mechanism proposed earlier by one of the authors in QCD we adduce the sought functions in an explicit form which enables us to conclude that the NN-potentials only correspond to some residual interactions while the latter are the direct result of the quark-gluonic hadronization into mesons when approching two nucleons.

We report the results for charge radii and decay constants of heavy–light D and B mesons in an improved QCD potential model. To enhance the effectiveness of short-range and long-range effect of the potential $$V(r)=-\frac{4 \alpha _\mathrm{s}}{3r}+\mathrm{br}$$ in the perturbative procedure a cutoff parameter $$r^P$$ is introduced as an integration limit. Another cutoff $$r_0$$ is used for the polynomial approximation of the series expansion used in the Dalgarno’s method of perturbation. The results obtained are found to be in agreement with other available data. The limitation of the approach is discussed in the manuscript.

The phenomena of hadron mass generating, strong running coupling and radiative transitions of charmonium excited states have been studied in the framework of a relativistic field model with analytic confinement. A meson mass equation is derived and a specific new behavior of the mass-dependent strong coupling $$\mathop {\bar {\alpha }}\nolimits_s $$ is revealed in the time-like region. A new infrared fixed point $$\mathop {\bar {\alpha }}\nolimits_s (0) = 1.032$$ has been found at origin. Independent and new estimates on the scalar glueball mass, radius and gluon condensate value have been performed. The spectrum of conventional mesons have been calculated by introducing a minimal set of parameters with relative errors less than 1.8 percent compared to the latest data. Accurate estimates of the leptonic decay constants of pseudoscalar and vector mesons have also been performed. Partial decay widths of the dominant radiative transitions of the charmonium orbital excitations have been estimated with reasonable accuracy.

We explore the hypothesis that the unexplained data from LSND and MiniBooNE are evidence for a new, heavy neutrino mass-eigenstate that mixes with the muon-type neutrino and decays into an electron-type neutrino and a new, very light scalar particle. We consider two different decay scenarios, one with Majorana neutrinos, one with Dirac neutrinos; both fit the data equally well. We find a reasonable, albeit not excellent, fit to the data of MiniBooNE and LSND. The decaying-sterile-neutrino hypothesis, however, cleanly evades constraints from disappearance searches and precision measurements of leptonic meson decays, as long as $1~{\rm MeV}\gtrsim m_4\gtrsim 10$~keV. The SBN program at Fermilab should be able to definitively test the decaying-sterile-neutrino hypothesis., This version v2 has been accepted for publication in JHEP. The changes from previous version are: inclusion of the data from KARMEN in the analysis, a new subsection about the sensitivity of SBN to nonzero decay effects, an new appendix describing the details of MiniBooNE analysis, additional references and some other minor changes

Tau-lepton semileptonic decays are described in the Nambu–Jona-Lasinio framework, and the validity of this description is discussed. Tau decays with a neutrino, a vector meson, and a pseudoscalar meson in the final state are considered. The extended version of the NJL model is employed, which makes possible the consideration of the contributions of both the ground and first radially excited meson states.