Vector Meson Nonets Research Articles

Mass spectrum and decays of the first radial excitation axial vector meson nonet

In this work, the mass spectrum of the first radial excitation axial vector meson nonet is considered in the framework of the nonrelativistic constituent quark model and Regge phenomenology. After that, we investigate the strong decay characteristics of these states within the [Formula: see text] model. The results are compared to values from other phenomenological models, and they may be beneficial in the prospective search for [Formula: see text] meson nonets.

Quark-mass and 1/Nc corrections to the vector-meson pseudoscalar-meson photon ( VPγ ) interaction

We analyze quark-mass and $1/{N}_{c}$ corrections to all of the radiative transitions between the vector-meson nonet and the pseudoscalar-meson nonet within a chiral effective Lagrangian approach. We perform fits of the available coupling constants to experimental data and discuss the corresponding approximations. In terms of five (six) coupling constants, we obtain a reasonably good description of the twelve experimental decay rates.

Production of omega mesons in pp collisions at mathbf {sqrt{s}=7,text {TeV}}

The invariant differential cross section of inclusive omega (782) meson production at midrapidity (|y|<0.5) in pp collisions at sqrt{s}=7,hbox {TeV} was measured with the ALICE detector at the LHC over a transverse momentum range of 2< p_{mathrm {T}}< 17,hbox {GeV}/c. The omega meson was reconstructed via its omega rightarrow pi ^+pi ^-pi ^0 decay channel. The measured omega production cross section is compared to various calculations: PYTHIA 8.2 Monash 2013 describes the data, while PYTHIA 8.2 Tune 4C overestimates the data by about 50%. A recent NLO calculation, which includes a model describing the fragmentation of the whole vector-meson nonet, describes the data within uncertainties below 6,hbox {GeV}/c, while it overestimates the data by up to 50% for higher p_{mathrm {T}}. The omega /pi ^0 ratio is in agreement with previous measurements at lower collision energies and the PYTHIA calculations. In addition, the measurement is compatible with transverse mass scaling within the measured p_{mathrm {T}} range and the ratio is constant with C^{omega /pi ^{0}}= 0.67 pm 0.03 text {~(stat)~} pm 0.04 text {~(sys)~} above a transverse momentum of 2.5,hbox {GeV}/c.

Interactions between vector mesons and dynamically generated resonances

The rho rho interaction and the corresponding dynamically generated bound states are revisited. We demonstrate that an improved unitarization method is necessary to study the pole structures of amplitudes outside the near-threshold region. In this work, we extend the study of the covariant rho rho scattering in a unitarized chiral theory to the S-wave interactions for the whole vector-meson nonet. We demonstrate that there are unphysical left-hand cuts in the on-shell factorization approach of the Bethe–Salpeter equation. This is in conflict with the correct analytic behavior and makes the so-obtained poles, corresponding to possible bound states or resonances, unreliable. To avoid this difficulty, we employ the first iterated solution of the N / D method and investigate the possible dynamically generated resonances from vector-vector interactions. A comparison with the results from the nonrelativistic calculation is provided as well.

Fragmentation of ω and ϕ mesons in e+e− and pp collisions at NLO

A combined analysis of both [Formula: see text] (LEP, SLD) and [Formula: see text] (RHIC-PHENIX and LHC-ALICE) hadroproduction processes are done for the first time for the vector meson nonet at the next-to-leading order (NLO) using a model with broken SU(3) symmetry. The transverse momentum ([Formula: see text]) and rapidity ([Formula: see text]) dependence of the differential cross-section for [Formula: see text] and [Formula: see text] mesons of the [Formula: see text] data are also discussed. The input universal quark (valence and singlet) fragmentation functions at a starting scale of [Formula: see text], after evolution, have values that are consistent with the earlier analysis for [Formula: see text] at NLO. However, the universal gluon fragmentation function is now well determined from this study with significantly smaller error bars, as the [Formula: see text] hadroproduction cross-section is particularly sensitive to the gluon fragmentation since it occurs at the same order as the quark fragmentation, in contrast to the [Formula: see text] hadroproduction process. Additional parameters involved in describing the strangeness and sea suppression and octet–singlet mixing are found to be close to the earlier analysis; in addition, a new relation between the gluon and sea suppression in [Formula: see text] and [Formula: see text] hadroproduction has been observed.

Study of the B¯q*→DM decays with perturbative QCD approach

The $\bar{B}_{q}^{\ast}$ ${\to}$ $DP$, $DV$ weak decays are studied with the perturbative QCD approach, where $q$ $=$ $u$, $d$ and $s$; $P$ and $V$ denote the ground $SU(3)$ pseudoscalar and vector meson nonet. It is found that the branching ratios for the color-allowed $\bar{B}_{q}^{\ast}$ ${\to}$ $D_{q}{\rho}^{-}$ decays can reach up to $10^{-9}$ or more, and should be promisingly measurable at the running LHC and forthcoming SuperKEKB experiments in the near future.

Numerical values of thefF,fD, andfScoupling constants in the SU(3) invariant interaction Lagrangian of the vector-meson nonet with1/2+octet baryons

It is demonstrated how an utilization of all existing experimental information on electric and magnetic nucleon form factors, to be described by the Unitary and Analytic (U\&A) nucleon electromagnetic structure model in space-like and time-like regions simultaneously, can provide numerical values of $f^F$, $f^D$, $f^S$ coupling constants in $SU(3)$ invariant interaction Lagrangian of the vector-meson nonet with $1/2^+$ octet baryons. The latter, together with universal vector-meson coupling constants $f_V$, play an essential role in a prediction of $1/2^+$ octet hyperon electromagnetic form factors behaviors.

Electromagnetic structure of vector mesons

Electromagnetic structure of the complete nonet of vector mesons (ρ 0 ,ρ + ,ρ − ,ω , φ,K ∗0 , K ∗+ , ¯ K ∗0 , K ∗− ) is investigated in the framework of the Unitary and Analytic model and insufficient experimental information on it is discussed.

Electromagnetic transitions in an effective chiral Lagrangian with the $ \eta^{{\prime}}_{}$ and light vector mesons

We consider the chiral Lagrangian with a nonet of Goldstone bosons and a nonet of light vector mesons. The mixing between the pseudoscalar mesons eta and eta-prime is taken into account. A novel counting scheme is suggested that is based on hadrogenesis, which conjectures a mass gap in the meson spectrum of QCD in the limit of a large number of colors. Such a mass gap would justify to consider the vector mesons and the eta-prime meson as light degrees of freedom. The complete leading order Lagrangian is constructed and discussed. As a first application it is tested against electromagnetic transitions of light vector mesons to pseudoscalar mesons. Our parameters are determined by the experimental data on photon decays of the omega, phi and eta-prime meson. In terms of such parameters we predict the corresponding decays into virtual photons with either dielectrons or dimuons in the final state.

Radiative decays of vector and pseudoscalar nonets

Using a counting scheme which treats the light pseudoscalar and the light vector-meson nonet on equal footing, the decays of the narrow light vector mesons into a pseudoscalar meson and a dilepton and of the 0 meson into an ! meson and a dielectron are calculated. Since all required parameters but one can be determined by other reactions, one has predictive power for the considered decay rates and form factors. The calculated partial decay widths are in good agreement with the available experimental data.

MASSES OF $s\bar{s}$ STATES AND NONET MIXING ANGLES

We first calculate the masses of the pure [Formula: see text] states for the pseudoscalar, vector, axial-vector, and tensor meson nonets in Regge phenomenology. Then based on the framework of meson–meson mixing and with the aid of the extracted masses of these pure [Formula: see text] states, we calculate the mixing angles for the pseudoscalar, vector, axial-vector, and tensor meson nonets. The results are in reasonable agreement with those obtained in many other approaches.

Properties of theρandσmesons from unitary chiral dynamics

The chiral limit of theandmasses and widths is discussed. We work within the inverse am- plitude method to one loop in SU(2) ChPT and analyze the consequences that all chiral logarithms cancel out in thechannel, while they do not cancel for thecase, and how they strongly influence the properties of this latter resonance. Our results confirm and explain the different behavior of theandpoles for NC not far from 3, but we extend the analysis to very large NC, where the behavior of these two resonances is re-analyzed. We note that the rather natural requirement of consistency between resonance saturation and unitarization imposes useful constraints. By looking only at thechannel, and within the single resonance approximation, we find that the masses of the first vector and scalar meson nonets, invoked in the single resonance approximation, turn out to be degenerated in the large NC limit. On the contrary we show that, for sufficiently largeNC, the scalar meson evolution lies beyond the applicability reach of the one-loop inverse amplitude method and if the scalar channel is also incorporated in the analysis, it may lead, in some cases, to phenomenologically inconsistent results.

Vector meson-vector meson interaction in a hidden gauge unitary approach

The formalism developed recently to study vector meson-vector meson interaction, and applied to the case of $\ensuremath{\rho}\ensuremath{\rho}$, is extended to study the interaction of the nonet of vector mesons among themselves. The interaction leads to poles of the scattering matrix corresponding to bound states or resonances. We show that 11 states (either bound or resonant) get dynamically generated in nine strangeness-isospin-spin channels. Five of them can be identified with those reported in the PDG, i.e., the ${f}_{0}(1370)$, ${f}_{0}(1710)$, ${f}_{2}(1270)$, ${f}_{2}^{\ensuremath{'}}(1525)$, and ${K}_{2}^{*}(1430)$. The masses of the latter three tensor states have been used to fine-tune the free parameters of the unitary approach, i.e., the subtraction constants in evaluating the vector meson-vector meson loop functions in the dimensional regularization scheme. The branching ratios of these five dynamically generated states are found to be consistent with data. The existence of the other six states should be taken as predictions to be tested by future experiments.

Nature of the axial-vector mesons from their Nc behavior within the chiral unitary approach

By describing within the chiral unitary approach the s-wave interaction of the vector meson nonet with the octet of pseudoscalar Goldstone Bosons, we find that the main component of the axial vector mesons b_1(1235), h_1(1170), h_1(1380), a_1(1260), f_1(1285) and the two states associated to the K_1(1270) does not follow the QCD dependence on the number of colors for ordinary qqbar mesons.

From Sakata Model to Goldberg-Ne'eman Quarks and Nambu QCD Phenomenology and “Right" and “Wrong" Experiments

The basic theoretical milestones were the Sakata SU(3) symmetry, the Goldberg-Ne'eman composite model with SU(3) triplets having baryon number (1/3) and the Nambu color gauge Lagrangian. The transition was led in right and wrong directions by interpreted by phenomenology. A experiment on $\bar p p$ annihilation at rest showed that the Sakata model predictions disagreed with experiment. A bad experiment prevented the use of the Goldberg-Ne'eman triplet model to predict the existence and masses of the of the $\Xi^*$ and $\Omega^-$. More revealed the existence and mass of the $\Xi^*$ and the $\Omega^-$ and the absence of positive strangeness baryon resonances, thus confirming the tenfold way. Further good experiments revealed the existence of the vector meson nonet, SU(3) breaking with singlet-octet mixing and the suppression of the $\phi \to \rho \pi$ decay. These led to the quark triplet model. The paradox of peculiar statistics then arose as the $\Delta^{++}$ and $\Omega^-$ contained three identical spin-1/2 fermions coupled symmetrically to spin (3/2). This led to color and the Nambu QCD. The book Lie Groups for Pedestrians used the Sakata model with the name sakaton for the $pn\Lambda$ triplet to teach the algebra of SU(3) to particle physicists in the U.S. and Europe who knew no group theory. The Sakata model had a renaissance in hypernuclear physics in the 1970's.

Properties of the vector meson nonet at largeNcbeyond the chiral limit

Coupling constants of the vector meson nonet are determined in the large-${N}_{c}$ limit, but beyond the chiral limit taking into account terms up to quadratic order in the Goldstone boson masses. With two input parameters five coupling constants for hadronic and dilepton decays are determined which agree very well with the experimental results. The obtained parameters are also used to calculate the pion and kaon decay constant in the large-${N}_{c}$ limit. A consistent picture is only obtained, if the correct assignment of the ${N}_{c}$-dependence of the electromagnetic charges of the quarks is taken into account.

Low lying axial-vector mesons as dynamically generated resonances

We make a theoretical study of the $s$-wave interaction of the nonet of vector mesons with the octet of pseudoscalar mesons starting from a chiral invariant Lagrangian and implementing unitarity in coupled channels. By looking for poles in the unphysical Riemann sheets of the unitarized scattering amplitudes, we get two octets and one singlet of axial-vector dynamically generated resonances. The poles found can be associated with most of the low lying axial-vector resonances quoted by the Particle Data Group: ${b}_{1}(1235)$, ${h}_{1}(1170)$, ${h}_{1}(1380)$, ${a}_{1}(1260)$, ${f}_{1}(1285)$, and two poles to the ${K}_{1}(1270)$ resonance. We evaluate the couplings of the resonances to the $VP$ states and the partial decay widths in order to reinforce the arguments in the discussion.

Gaussian Source One-Boson-Exchange Potential between Two Octet Baryons

The nonstatic baryon-baryon potential arising from the Gaussian meson source function, G i exp (- 2 i r 2 /4), is constructed by exchanging the scalar, pseudoscalar and vector meson nonets, where G i is the strength and A i the size parameter of source i (i = 1,2). This potential is referred to as GSOBEP. It has no singularity at the origin. In this potential, the radial function behaves like the Yukawa function in the outer region (r > 1 fm), and like the Yukawa function multiplied by the error function in the inner region (r < 1 fm). The Gaussian source is assumed to originate from the statistical distribution of valence quarks and many sea quarks. The potential parameters consist of the SU(3) parameters, such as the singlet and octet coupling constants, g 1 and g 8 , the coupling ratio α = g F /(g D + g F ), the singlet-octet mixing angle 0 for each meson, and the effective source size parameter, expressed as Λ = Λ 1 Λ 2 /√Λ 2 1 + Λ 2 2 . The potential parameters are determined by the X 2 -fitting to the nucleon-nucleon, hyperon-nucleon and hyperon-hyperon data. The fit is quite good on the whole.

A chiral effective field U(3) L⊗ U(3) R theory for light mesons

We consider mixing schemes and masses of light vector mesons within the framework of an extended U(3) L ⊗ U(3) R effective field theory based on the hidden local symmetry approach, where the light mass pseudoscalar and vector meson nonets play the role of dynamic variables. The mixing schemes and model free parameters are determined through diagonalization of the kinetic and mass matrices, supplemented with the assumption that eigenvalues of the resulting mass matrix be equal to the physical meson masses. We show that a particular choice of the Lagrangian which breaks SU(3) F incorporates VMD as a good first approximation for low-momentum electromagnetic processes, and reproduces the radii of charged pions and kaons fairly well.

Meson U(3) L⊗ U(3) R chiral theory with flavor and nonet symmetry breaking

An extended U(3) L ⊗ U(3) R chiral effective field theory which includes pseudoscalar and vector meson nonets as dynamic variables is presented. The theory combines a hidden local symmetry approach with a general procedure of including the η′ meson into chiral theory, and accounts for direct and indirect flavor and nonet symmetry breaking effects via a mechanism based on the quark mass matrix. The theory is applied to anomalous radiative decays of pseudoscalar and vector mesons, using particle mixing schemes that correspond to different symmetry breaking assumptions and are uniquely determined by the Lagrangian presumed. Radiative decays of light flavor mesons are best explained within the framework of a single mixing angle scheme, providing evidence for SU(3) F and nonet symmetry breaking. Based on our general treatment of symmetry breaking and the analysis of radiative decays we propose the value θ P =−14.3±2.2.