Showing papers on "Pseudoscalar published in 2005"
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TL;DR: In this paper, the modern status of basic low energy QCD parameters is reviewed, including those induced by external fields, and it is demonstrated that the recent data allows one to determine the light quark mass ratios with an accuracy 10-15%.
Abstract: The modern status of basic low energy QCD parameters is reviewed. It is demonstrated, that the recent data allows one to determine the light quark mass ratios with an accuracy 10-15%. The general analysis of vacuum condensates in QCD is presented, including those induced by external fields. The QCD coupling constant alpha_s is found from the tau-lepton hadronic decay rate. V-A spectral functions of tau-decay are used for construction of the V-A polarization operator Pi_{V-A}(s) in the complex s-plane. The operator product expansion (OPE) is used up to dimension D=10 and the sum rules along the rays in the complex s-plane are constructed. The best values of quark condensate and alpha_s ^2 are found. The value of quark condensate is confirmed by considering the sum rules for baryon masses. Gluon condensate is found in four ways: by considering of V+A polarization operator based on the tau-decay data, by studying the sum rules for polarization operators momenta in charmonia in vector, pseudoscalar and axial channels. All of these determinations are in agreement and result in =0.005 \pm 0.004 GeV^4. Valence quark distributions in proton are calculated in QCD using the OPE in proton current virtuality. The quark distributions agree with those found from the deep inelastic scattering data. The same value of gluon condensate is favoured.
221 citations
TL;DR: In this article, a detailed numerical study of finite volume effects for masses and decay constants of the octet of pseudoscalar mesons is presented, using chiral perturbation theory and asymptotic formulae a la Luscher.
218 citations
TL;DR: In this paper, a one-boson-exchange model for the hyperon-nucleon (Lambda N, Sigma N) interaction is presented, which incorporates the standard one boson exchanges of the lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) flavor symmetry relations.
Abstract: A one-boson-exchange model for the hyperon-nucleon (\Lambda N, \Sigma N) interaction is presented. The model incorporates the standard one boson exchanges of the lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) flavor symmetry relations. As the main new feature of the model, the contributions in the scalar--isoscalar (\sigma) and vector--isovector (\rho) exchange channels are now constrained by a microscopic model of correlated \pi\pi and K \bar K exchange. Additional short-ranged ingredients of the model in the scalar--isovector (a_0) and scalar--isospin-1/2 (\kappa) channels are likewise viewed as arising from meson-meson correlations but are treated phenomenologically. With this model a satisfactory reproduction of the available hyperon-nucleon data can be achieved.
166 citations
TL;DR: In this paper, a density wave in quark matter is discussed at finite temperature, which occurs along with the chiral condensation, and is described by a dual standing wave in scalar and pseudoscalar condensates on the Chiral circle.
Abstract: A density wave in quark matter is discussed at finite temperature, which occurs along with the chiral condensation, and is described by a dual standing wave in scalar and pseudoscalar condensates on the chiral circle. The mechanism is quite similar to that for the spin density wave suggested by Overhauser and entirely reflects many-body effects. It is found within a mean-field approximation for the Nambu--Jona-Lasinio model that the chiral-condensed phase with the density wave develops at a high-density region just outside the usual chiral-transition line in phase diagram. A magnetic property of the density wave is also elucidated.
152 citations
TL;DR: In this article, the s-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons are studied in a unitarized coupled channel approach.
113 citations
TL;DR: In this paper, an extension to the ladder truncated Bethe-Salpeter equation for mesons and the rainbow truncated quark Schwinger-Dyson equations which includes quark-loop corrections to the gluon propagator is introduced.
Abstract: We introduce an extension to the ladder truncated Bethe-Salpeter equation for mesons and the rainbow truncated quark Schwinger-Dyson equations which includes quark-loop corrections to the gluon propagator. This truncation scheme obeys the axialvector Ward-Takahashi identity relating the quark self-energy and the Bethe-Salpeter kernel. Two different approximations to the Yang-Mills sector are used as input: the first is a sophisticated truncation of the full Yang-Mills Schwinger-Dyson equations, the second is a phenomenologically motivated form. We find that the spectra and decay constants of pseudoscalar and vector mesons are overall described well for either approach. Meson mass results for charge eigenstate vector and pseudoscalar meson masses are compared to lattice data. The effects of unquenching the system are small but not negligible.
86 citations
TL;DR: In this paper, the amplitude at the two-loop level in QCD for a general neutral Higgs boson which has both scalar and pseudoscalar couplings to quarks is given in terms of a scalar vertex form factor.
Abstract: As a first step in the aim of arriving at a differential description of neutral Higgs boson decays into heavy quarks, $h\ensuremath{\rightarrow}Q\overline{Q}X$, to second order in the QCD coupling ${\ensuremath{\alpha}}_{S}$, we have computed the $hQ\overline{Q}$ amplitude at the two-loop level in QCD for a general neutral Higgs boson which has both scalar and pseudoscalar couplings to quarks. This amplitude is given in terms of a scalar and a pseudoscalar vertex form factor, for which we present closed analytic expressions in terms of one-dimensional harmonic polylogarithms of maximum weight 4. The results hold for arbitrary four-momentum squared, ${q}^{2}$, of the Higgs boson and of the heavy-quark mass, $m$. Moreover, we derive the approximate expressions of these form factors near threshold and in the asymptotic regime ${m}^{2}/{q}^{2}\ensuremath{\ll}1$.
61 citations
TL;DR: In this article, the scaling behavior of quenched Wilson twisted mass fermions at maximal twist was investigated by applying two definitions of the critical mass: vanishing of pseudoscalar meson mass mPS and vanishing of PCAC quark mass mPCAC.
Abstract: We investigate the scaling behaviour of quenched Wilson twisted mass fermions at maximal twist applying two definitions of the critical mass The first definition uses the vanishing of the pseudoscalar meson mass mPS while the second employs the vanishing of the PCAC quark mass mPCAC We confirm in both cases the expected O(a) improvement In addition, we show that the PCAC quark mass definition leads to substantially reduced O(a2) cut-off effects even when the pseudoscalar meson mass mPS is as small as 270 MeV At a fixed value of mPS we perform continuum limits for the vector meson mass mV and for the pseudoscalar decay constant fPS and discuss the renormalisation constant ZV of the vector current
47 citations
TL;DR: In this article, the relativistic kinematics and quark spins were taken into account to reproduce the masses of the self-conjugate and non-self-convoyate mesons in the context of the spinless Salpeter equation.
Abstract: We reproduce masses of the self-conjugate and non-self-conjugate mesons in the context of the spinless Salpeter equation taking into account the relativistic kinematics and the quark spins. The hyperfine splittings for the 2S charmonium and 1S bottomonium are also calculated. Further, the pseudoscalar and vector decay constants of the Bc meson and the unperturbed radial wave function at the origin are also calculated. We have obtained a local equation with a complete relativistic corrections to a class of three attractive static interaction potentials of the general form V(r) = -Ar-β + κrβ + V0, with β = 1, 1/2, 3/4 decomposed into scalar and vector parts in the form VV(r) = -Ar-β + (1-∊)κrβ and VS(r) = ∊κrβ + V0; where 0≤∊≤1. We have used the shifted large-N-expansion technique (SLNET) to solve the reduced equation for the scalar (∊ = 1), equal mixture of scalar-vector (∊ = 1/2), and vector (∊ = 0) confinement interaction kernels. The energy eigenvalues are carried out up to the third order approximation.
41 citations
TL;DR: In this article, the authors considered the Resonance Chiral Theory with one multiplet of scalar and pseudoscalar resonances, up to bilinear couplings in the resonance fields, and evaluated its β-function at one-loop with the use of the background field method.
Abstract: We consider the Resonance Chiral Theory with one multiplet of scalar and pseudoscalar resonances, up to bilinear couplings in the resonance fields, and evaluate its β-function at one-loop with the use of the background field method. Thus we also provide the full set of operators that renormalize the theory at one loop and render it finite.
39 citations
TL;DR: In this article, it was shown that the Goldstone mesons have a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken, while the decay constants of their radial excitations vanish.
Abstract: A strongly momentum-dependent dressed-quark mass function is basic to QCD. It is central to the appearance of a constituent-quark mass-scale and an existential prerequisite for Goldstone modes. Dyson-Schwinger equation (DSEs) studies have long emphasised this importance, and have proved that QCD's Goldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken, while the decay constants of their radial excitations vanish. Such features are readily illustrated using a rainbow-ladder truncation of the DSEs. In this connection we find (in GeV): fηc(1S)=0.233, mηc(2S)=3.42; and support for interpreting η(1295), η(1470) as the first radial excitations of η(548), η′(958), respectively, and K(1460) as the first radial excitation of the kaon. Moreover, such radial excitations have electromagnetic diameters greater than 2 fm. This exceeds the spatial length of lattices used typically in contemporary lattice-QCD.
TL;DR: In this paper, it was shown that the induced pseudoscalar interactions are strongly constrained by data on π ± → l ± ν l decay, which implies limits on the underlying fundamental scalar interactions that in many cases are substantially stronger than limits on scalar interaction from direct β-decay searches.
TL;DR: In this paper, the phase diagram of the three-flavor Nambu-Jona-Lasinio model at zero and finite temperature was calculated as a function of the up, down, and strange quark chemical potentials.
Abstract: We calculate numerically the phase diagram of the three-flavor Nambu-Jona-Lasinio model at zero and finite temperature as a function of the up, down, and strange quark chemical potentials. We focus on the competition between pseudoscalar condensation and color superconductivity. We find that the two types of phases are separated by first-order transitions.
TL;DR: In this article, bound state masses of the self-conjugate and non-self-convoyate mesons in the context of the Schrodinger equation taking into account the relativistic kinematics and the quark spins are presented.
Abstract: We present bound state masses of the self-conjugate and non-self-conjugate mesons in the context of the Schrodinger equation taking into account the relativistic kinematics and the quark spins. We apply the usual interaction by adding the spin dependent correction. The hyperfine splittings for the 2S charmonium and 1S bottomonium are calculated. The pseudoscalar and vector decay constants of the Bc meson and the unperturbed radial wave function at the origin are also calculated. We have obtained a local equation with a complete relativistic corrections to a class of three attractive static interaction potentials of the general form V(r) = -Ar-β+κrβ+V0, with β = 1, 1/2, 3/4 which can also be decomposed into scalar and vector parts in the form VV(r) = -Ar-β+(1-∊)κrβ and VS(r) = ∊κrβ+V0; where 0≤∊≤1. The energy eigenvalues are carried out up to the third order approximation using the shifted large-N-expansion technique.
TL;DR: In this paper, the masses and decay constants of pseudoscalar mesons D, D s, and K in quenched lattice QCD with exact chiral symmetry were determined.
TL;DR: In this paper, the scalar and pseudoscalar sector in a five-dimenional model describing chiral symmetry breaking has been studied, and scalar coefficients of the chiral lagrangian coefficients have been obtained.
Abstract: We study the scalar and pseudoscalar sector in a five-dimenional model describing chiral symmetry breaking. We calculate the scalar and pseudoscalar two-point correlator, the mass spectrum and interactions. We also obtain the scalar and pseudoscalar contributions to the coefficients of the chiral lagrangian and determine the scalar form factor of the pseudo-Goldstone bosons. Most quantities show a good agreement with QCD.
01 Jan 2005
TL;DR: In this article, the pseudoscalar and vector meson masses and leptonic decay constants, ranging from pions up to c bound states, were discussed and the results were in good agreement with data.
Abstract: Two-body bound states such as mesons are described by solutions of the Bethe-Salpeter equation. We discuss recent results for the pseudoscalar and vector meson masses and leptonic decay constants, ranging from pions up to c bound states. Our results are in good agreement with data. Essential in these calculation is a momentum-dependent quark mass function, which evolves from a constituent-quark mass in the infrared region to a currentquark mass in the perturbative region. In addition to the mass spectrum, we review the electromagnetic form factors of the light mesons. Electromagnetic current conservation is manifest and the influence of intermediate vector mesons is incorporated self-consistently. The results for the pion form factor are in excellent agreement with experiment.
TL;DR: In this paper, the pseudoscalar mesons are discussed in the quark-flavor basis, and the divergences of the axial vector currents are combined with the assumption that the decay constants follow the pattern of particle state mixing in that basis, determining the mixing parameters for given masses of the physical mesons.
Abstract: Mixing of the pseudoscalar mesons is discussed in the quark-flavor basis. The divergences of the axial vector currents which embody the axial vector anomaly, combined with the assumption that the decay constants follow the pattern of particle state mixing in that basis, determine the mixing parameters for given masses of the physical mesons. These mixing parameters are compared with results from other work in some detail. Phenomenological applications of the quark-flavor mixing scheme are presented with particular interest focussed on isospin symmetry breaking which is generated by means of η and η′ admixtures to the pion. Consequences of a possible difference in the basis decay constants fu and fd for the strength of isospin symmetry breaking are also examined.
22 Apr 2005
TL;DR: In this paper, the meson spectrum in the framework of a second order quark-antiquark Bethe-Salpeter formalism was studied, and an analytic one loop running coupling constant αs(Q) was used in the calculations.
Abstract: In line with some previous works, we study in this paper the meson spectrum in the framework of a second order quark‐antiquark Bethe‐Salpeter formalism which includes confinement. An analytic one loop running coupling constant αs(Q), as proposed by Shirkov and Sovlovtsov, is used in the calculations. As for the quark masses, the case of a purely phenomenological running mass for the light quarks in terms of the c. m. momentum is further investigated. Alternatively a more fundamental expression mP(Q) is introduced for light and strange quarks, combining renormalization group and analyticity requirements with an approximate solution of the Dyson‐Schwinger equation. The use of such running coupling constant and masses turns out to be essential for a correct reproduction of the the light pseudoscalar mesons.
TL;DR: In this article, a nonperturbative determination of the renormalization factor ZS of the scalar density in quenched QCD with overlap fermions is presented.
Abstract: We present a non-perturbative determination of the renormalization factor ZS of the scalar density in quenched QCD with overlap fermions. Results are obtained at four values of the lattice spacing. By combining ZS with results for the low-energy constant ? we are able to compute the renormalization group invariant scalar condensate in the continuum limit with a total accuracy of 7%, excluding dynamical quark effects. Our result translates to ?(2 GeV) = (285?9 MeV)3 if the scale is set by the kaon decay constant. We have also performed scaling studies of the pseudoscalar decay constant and the vector mass. Our results indicate that quantities computed using overlap quarks exhibit excellent scaling behaviour, with small residual lattice artifacts.
TL;DR: In this paper, the scaling behavior of quenched Wilson twisted mass fermions at maximal twist was investigated by applying two definitions of the critical mass: the vanishing of the pseudoscalar meson mass m_PS and the PCAC quark massm_PCAC.
Abstract: We investigate the scaling behaviour of quenched Wilson twisted mass fermions at maximal twist applying two definitions of the critical mass. The first definition uses the vanishing of the pseudoscalar meson mass m_PS while the second employs the vanishing of the PCAC quark mass m_PCAC. We confirm in both cases the expected O(a) improvement. In addition, we show that the PCAC quark mass definition leads to substantially reduced O(a^2) cut-off effects even when the pseudoscalar meson mass m_PS is as small as 270 MeV. At a fixed value of m_PS we perform continuum limits for the vector meson mass m_V and for the pseudoscalar decay constant f_PS and discuss the renormalisation constant Z_V of the vector current.
TL;DR: In this article, the decay constants of the pseudoscalar mesons to two loops for three flavors of sea quarks were studied in Partially Quenched Chiral Perturbation Theory (PQChPT).
Abstract: This paper presents a first study of the decay constants of the charged, or flavor-off-diagonal, pseudoscalar mesons to two loops for three flavors of sea quarks, in Partially Quenched Chiral Perturbation Theory (PQChPT). Explicit analytical expressions up to order p 6 in the momentum expansion are given. The calculations have been performed within the supersymmetric formulation of PQChPT. We also present some numerical results to indicate the size of the corrections.
TL;DR: In this article, the masses and decay constants of light pseudoscalar and scalar mesons within the QCD sum rules method are briefly reviewed and the predictions are based on the 1/Nc-supported model spectra, which consist of an infinite number of infinitely narrow resonances.
Abstract: The calculations of masses and decay constants of the radial excitations of light pseudoscalar and scalar mesons within the QCD sum rules method are briefly reviewed. The predictions are based on the 1/Nc-supported model spectra, which consist of an infinite number of infinitely narrow resonances, and on the assumption that the ground states of light scalar mesons may be considered as \(\bar qq\)-bound states. The results of the studies are compared with the existing experimental data and with the predictions of other theoretical approaches.
TL;DR: In this paper, the axial radius and pseudoscalar form factor of the nucleon axial current were derived under twisted heavy baryon chiral perturbation theory.
Abstract: With twisted boundary conditions on the quark fields, we study nucleon matrix elements of the axial current utilizing twisted heavy baryon chiral perturbation theory. One can explore the momentum transfer dependence of the axial form factors more easily than by using ordinary lattice quantized momenta alone. As examples, we derive expressions for the nucleon axial radius and pseudoscalar form factor.
TL;DR: In this paper, the masses and decay constants of pseudoscalar mesons to two loops for two flavors of sea-quarks were studied in Partially Quenched Chiral Perturbation Theory (PQ chi PT).
Abstract: This paper presents a first study of the masses and decay constants of the charged, or flavor-off-diagonal, pseudoscalar mesons to two loops for two flavors of sea-quarks, in Partially Quenched Chiral Perturbation Theory (PQ chi PT). Explicit analytical expressions up to O(p(6)) in the momentum expansion are given. The calculations have been performed within the supersymmetric formulation of PQ chi PT. A numerical analysis is done to indicate the size of the corrections.
TL;DR: In this paper, the authors considered the dissociation of J / ψ by the lowest-lying pseudoscalar and vector mesons in the hadronic fireball formed in heavy ion collisions, assumed to be a hadron gas at temperature T. From data at low centrality, they found T = 165 − 185 MeV, close to the predicted temperature of the transition to quark-gluon plasma and to the temperatures measured by hadron abundances.
TL;DR: In this paper, the SU(3) symmetry breaking effects of the coefficients of the non-leptonic two body decays were investigated based on the diagrammatic decomposition in a generalized factorization formalism.
Abstract: The non-leptonic two body decays $D\to PP$
and $D\to PV$
are investigated based on the diagrammatic decomposition in a generalized factorization formalism. It is shown that to fit the experimental data, the SU(3) flavor symmetry breaking effects of the coefficients a
i
s should be considered in $D\to PP$
decay modes. In $D\to PV$
decays, the final state hadron structure due to the pseudoscalar and vector mesons has more important effects on the coefficients a
i
s than the SU(3) symmetry breaking.
TL;DR: In this article, an improved version of the so-called NLA scheme, which allows a better treatment of the hard fermionic modes, is proposed and the impact of the improved NLA on the pseudoscalar temporal correlator is investigated.
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TL;DR: In this article, the authors explore the Higgs sector of the NMSSM in the limit when the Peccei-Quinn symmetry is exact or only slightly broken.
Abstract: We explore the Higgs sector of the NMSSM in the limit when the Peccei--Quinn symmetry is exact or only slightly broken In this case the Higgs spectrum has a hierarchical structure which is caused by the stability of the physical vacuum We find a strong correlation between the parameters of the NMSSM if \kappa=0 or \kappa\lesssim \lambda^2 It allows one to distinguish the NMSSM with exact or softly broken PQ-symmetry from the MSSM even when extra scalar and pseudoscalar Higgs states escape direct detection
TL;DR: The spectrum of meson and diquark excitations of dense color neutral cold quark matter is investigated in the framework of a two-flavored Nambu-Jona-Lasinio-type model, including a quark {mu}- and color {mu-sub 8}-chemical potential.
Abstract: The spectrum of meson and diquark excitations of dense color neutral cold quark matter is investigated in the framework of a two-flavored Nambu-Jona-Lasinio-type model, including a quark {mu}- and color {mu}{sub 8}-chemical potential. It was found that, in the color superconducting (2SC) phase, i.e. at {mu}>{mu}{sub c}=342 MeV, {mu}{sub 8} acquires rather small values {approx}10 MeV in order to ensure the color neutrality. In this phase the {pi} and {sigma} meson masses are evaluated around {approx}330 MeV. The spectrum of scalar diquarks in the color neutral 2SC phase consists of a heavy [SU{sub c}(2)-singlet] resonance with mass {approx}1100 MeV, four light diquarks with mass 3|{mu}{sub 8}|, and one Nambu-Goldstone boson, which is in accordance with the Goldstone theorem. Moreover, in the 2SC phase there are five light stable particles as well as a heavy resonance in the spectrum of pseudoscalar diquarks. In the color symmetric phase, i.e. for {mu}<{mu}{sub c}, a mass splitting of scalar diquarks and antidiquarks is shown to arise if {mu}{ne}0, contrary to the case of {mu}=0, where the masses of scalar antidiquarks and diquarks are degenerate at the value {approx}700 MeV. If the coupling strength in the pseudoscalar diquark channel is the same as in themore » scalar diquark one (as for QCD-inspired Nambu-Jona-Lasinio models), then in the color symmetric phase pseudoscalar diquarks are not allowed to exist as stable particles.« less