Showing papers on "Meson published in 2008"
TL;DR: In this article, it was shown that there is an exact correspondence between the fth-dimensional coordinate of anti-de Sitter space z and a specic light-front impact variable which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time.
Abstract: at large distances. The AdS/CFT correspondence also provides insights into the inherently non-perturbative aspects of QCD such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fth-dimensional coordinate of anti{de Sitter (AdS) space z and a specic light-front impact variable which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and which allow the computation of decay constants, form factors and other exclusive scattering amplitudes. Relativistic light-front equations in ordinary space-time are found which reproduce the results obtained using the fth-dimensional theory. As specic examples we compute the pion coupling constant f , the pion charge radius r 2 and examine the propagation of the electromagnetic current in AdS space, which determines the space and time-like behavior of the pion form factor and the pole of the meson.
404 citations
TL;DR: In this paper, a number of improvements to the previous AKK extraction of fragmentation functions for π ±, K ±, p / p ¯, K S 0 and Λ / Λ ¯ particles at next-to-leading order are performed.
260 citations
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TL;DR: In this paper, the authors argue that relatively compact charmonium states, such as hadro-charmonium, can be bound inside light hadronic matter, in particular inside higher resonances made from light quarks and/or gluons.
220 citations
TL;DR: In this article, light scalar mesons in the holographic QCD soft-wall model with a background dilaton field were studied and the masses and decay constants were compatible with experiment and QCD determinations.
Abstract: We study light scalar mesons in the holographic QCD soft-wall model with a background dilaton field. The masses and decay constants are compatible with experiment and QCD determinations if a{sub 0}(980) and f{sub 0}(980) are identified as the lightest scalar mesons; moreover, the states are organized in linear Regge trajectories with the same slope of vector mesons. Comparing the two-point correlation function of scalar operators derived on the anti-de Sitter side and in QCD, information about the condensates can be derived. Strong couplings of scalar states to pairs of light pseudoscalar mesons turn out to be small, at odds with experiment and QCD estimates: we discuss how this discrepancy is related to the description of chiral symmetry breaking in this model, and the possible solutions.
213 citations
TL;DR: Charmonium, the spectroscopy of mesons, has recently enjoyed a renaissance with the discovery of several missing states and numerous unexpected charmonium-like resonances as mentioned in this paper.
Abstract: Charmonium, the spectroscopy of mesons, has recently enjoyed a renaissance with the discovery of several missing states and numerous unexpected charmonium-like resonances. These discoveries were made possible by the extremely large data samples made available by the B factories at SLAC and KEK, as well as CESR. Conventional states are well described by quark potential models; however, many of the newly discovered charmonium-like mesons do not seem to fit into the conventional spectrum. There is growing evidence that at least some of these new states are exotic, e.g., new forms of hadronic matter such as mesonic molecules, tetraquarks, and/or hybrid mesons. In this review we describe expectations for the properties of conventional charmonium states and the predictions for molecules, tetraquarks, and hybrids and the various processes that produce them. We examine the evidence for the new candidate exotic mesons, possible explanations, and experimental measurements that might reveal the nature of these states.
203 citations
TL;DR: In this article, a modified perturbative approach was used to construct generalized parton distributions from the CTEQ6 parton distribution with the help of double distributions for light vector mesons.
Abstract: Electroproduction of light vector mesons is analyzed on the basis of handbag factorization. The required generalized parton distributions are constructed from the CTEQ6 parton distributions with the help of double distributions. The partonic subprocesses are calculated within the modified perturbative approach. The present work extends our previous analysis of the longitudinal cross section to the transverse one and other observables related to both the corresponding amplitudes. Our results are compared to recent experimental findings in detail.
194 citations
TL;DR: In this article, the effect of instanton induced, six-fermion effective Lagrangian on the decays of the lightest scalar mesons in the diquark-antidiquark picture was discussed.
193 citations
TL;DR: In this paper, the authors elaborate the production of single heavy-flavored hadrons in e + e − annihilation at next-to-leading order in the general-mass variable-flavor-number scheme.
184 citations
TL;DR: In this article, a quantitative evaluation of dilepton sources in heavy-ion reactions is performed taking into account both thermal and non-thermal production mechanisms, and a convolution of the emission rates over a thermal fireball expansion results in good agreement with experiment in the low-mass spectra, confirming the predicted broadening of the ρ meson in hadronic matter in connection with the prevalence of baryon induced medium effects.
163 citations
TL;DR: In this article, the authors studied the physics of finite temperature large N four dimensional SU(N) gauge theory, focusing on the dynamics of fundamental quarks in the presence of a background magnetic field.
Abstract: Using a ten dimensional dual string background, we study aspects of the physics of finite temperature large N four dimensional SU(N) gauge theory, focusing on the dynamics of fundamental quarks in the presence of a background magnetic field. At vanishing temperature and magnetic field, the theory has N = 2 supersymmetry, and the quarks are in hypermultiplet representations. In a previous study, similar techniques were used to show that the quark dynamics exhibit spontaneous chiral symmetry breaking. In the present work we begin by establishing the non-trivial phase structure that results from finite temperature. We observe, for example, that above the critical value of the field that generates a chiral condensate spontaneously, the meson melting transition disappears, leaving only a discrete spectrum of mesons at any temperature. We also compute several thermodynamic properties of the plasma.
145 citations
TL;DR: In this paper, a quark condensate forms at finite quark mass, and the value of the condensates varies smoothly with the quark masses for generic regions in parameter space.
Abstract: In studying the dynamics of large N{sub c}, SU(N{sub c}) gauge theory at finite temperature with fundamental quark flavors in the quenched approximation, we observe a first order phase transition. A quark condensate forms at finite quark mass, and the value of the condensate varies smoothly with the quark mass for generic regions in parameter space. At a particular value of the quark mass, there is a finite discontinuity in the condensate's vacuum expectation value, corresponding to a first order phase transition. We study the gauge theory via its string dual formulation using the AdS/CFT conjecture, the string dual being the near-horizon geometry of N{sub c} D3-branes at finite temperature, AdS{sub 5}-SchwarzschildxS{sup 5}, probed by a D7-brane. The D7-brane has topology R{sup 4}xS{sup 3}xS{sup 1} and allowed solutions correspond to either the S{sup 3} or the S{sup 1} shrinking away in the interior of the geometry. The phase transition represents a jump between branches of solutions having these two distinct D-brane topologies. The transition also appears in the meson spectrum.
TL;DR: An overview of the theory and phenomenology of hadrons and QCD is provided from a Dyson-Schwinger equation viewpoint in this article, followed by a discussion of the definition and realization of light quark confinement, the nonperturbative nature of the running mass in QCD and inferences from the gap equation relating to the radius of convergence for expansions of observables in the current quark mass are described.
TL;DR: In this article, the authors calculate the gravitational form factors of vector mesons using a holographic model of QCD using sum rules connecting stress tensor form factors to generalized parton distributions.
Abstract: We calculate gravitational form factors of vector mesons using a holographic model of QCD These provide restrictions on the generalized parton distributions of vector mesons, via the sum rules connecting stress tensor form factors to generalized parton distributions We concentrate on the traceless part of the stress tensor, which suffices to fix the momentum and angular momentum sum rules The vector mesons appear noticeably more compact measured by the gravitational form factors than by the charge form factor
TL;DR: In this paper, the parameter tuning of three flavors of dynamical clover quarks on anisotropic lattices was performed using three dimensional spatial stout-link smearing, and the gauge anisotropy was determined in a small box with Schr\"odinger-background using Wilson-loop ratios.
Abstract: DOI: http://dx.doi.org/10.1103/PhysRevD.78.054501 In this work we perform the parameter tuning of three flavors of dynamical clover quarks on anisotropic lattices. The fermion action uses three dimensional spatial stout-link smearing. The gauge anisotropy is determined in a small box with Schr\"odinger-background using Wilson-loop ratios. The fermion anisotropy is obtained from studying the meson dispersion relation with antiperiodic boundary conditions in the time direction. The spatial and temporal clover coefficients are fixed to the tree-level tadpole-improved values, and we demonstrate that they satisfy the nonperturbative conditions as determined by the Schroedinger functional method. For the desired lattice spacing $$a_s\approx 0.12$$~fm and renormalized anisotropy $$\xi=3.5$$, we find the gauge and fermionic anisotropies can be fixed to quark mass independent values up through the strange quark mass. This work lays the foundation needed for fur
TL;DR: In this article, the pion and sigma meson exchange potential of the D-0(D) over bar*(0) system were taken into account and a dynamical analysis was performed.
Abstract: After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the D-0(D) over bar*(0) system. The s meson exchange potential is repulsive from heavy quark symmetry and numerically important for a loosely bound system. Our analysis disfavors the interpretation of X(3872) as a loosely bound molecular state if we use the experimental D*D pi coupling constant g = 0.59 and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. Bound state solutions with negative eigenvalues for the D-0(D) over bar* system exist only with either a very large coupling constant (twice the experimental value) or a large cutoff (Lambda similar to 6GeV or beta similar to 6GeV(2)). In contrast, there probably exists a loosely bound S-wave B (B) over bar* molecular state. Once produced, such a molecular state would be rather stable, since its dominant decay mode is the radiative decay through B* -> B gamma. Experimental search of these states will be very interesting.
TL;DR: In this article, the authors reported precision measurements of the Feynman x (x(F)) dependence and transverse momentum (p(T)) dependence for the production of pi(0) mesons from polarized proton collisions at s = 200 GeV.
Abstract: We report precision measurements of the Feynman x (x(F)) dependence, and first measurements of the transverse momentum (p(T)) dependence, of transverse single-spin asymmetries for the production of pi(0) mesons from polarized proton collisions at s=200 GeV. The x(F) dependence of the results is in fair agreement with perturbative QCD model calculations that identify orbital motion of quarks and gluons within the proton as the origin of the spin effects. Results for the p(T) dependence at fixed x(F) are not consistent with these same perturbative QCD-based calculations.
TL;DR: In this paper, the authors reported the observation of a new DsJ meson produced in B+-->D0DsJ>D0D0K, which has a mass of M=2708+/-9(-10)(+11) MeV/c2, a width Gamma=108+/-23(-31)(+36) MeVs and a 1- spin-parity and statistical significance of this observation is 8.4 sigma.
Abstract: We report the observation of a new DsJ meson produced in B+-->D0DsJ-->D0D0K+. This state has a mass of M=2708+/-9(-10)(+11) MeV/c2, a width Gamma=108+/-23(-31)(+36) MeV/c2 and a 1- spin-parity. The statistical significance of this observation is 8.4 sigma. The results are based on an analysis of 449 x 10(6) BB events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
TL;DR: In this paper, the functional renormalization group and one-loop improved renormalisation group flows are reviewed and the associated flow equations and nonperturbative approximations schemes for its solutions are discussed.
Abstract: The idea of the functional renormalization group and one-loop improved renormalization group flows are reviewed. The associated flow equations and nonperturbative approximations schemes for its solutions are discussed. These techniques are then applied to the strong interaction in the framework of an effective quark meson model, which is introduced in great detail. The renormalization group analysis of the two flavor quark meson model is extended to finite temperature and quark chemical potential which allows for an analysis of the chiral phase diagram beyond the mean field approximation.
TL;DR: This paper derived expressions for mass shifts, continuum components, and mixing amplitudes of quark model states due to hadron loops, as perturbation series in the valence-continuum coupling Hamiltonian.
Abstract: In this paper, we develop a formalism for incorporating hadron loops into the quark model. We derive expressions for mass shifts, continuum components, and mixing amplitudes of ``quenched'' quark model states due to hadron loops, as perturbation series in the valence-continuum coupling Hamiltonian. We prove three general theorems regarding the effects of hadron loops, which show that given certain constraints on the external ``bare'' quark model states, the valence-continuum coupling, and the hadrons summed in the loops, the following results hold: (1) The loop mass shifts are identical for all states within a given $N,L$ multiplet. (2) These states have the same total open-flavor decay widths. (3) Loop-induced valence configuration mixing vanishes provided that ${L}_{i}\ensuremath{
e}{L}_{f}$ or ${S}_{i}\ensuremath{
e}{S}_{f}$. The charmonium system is used as a numerical case study, with the ${}^{3}{P}_{0}$ decay model providing the valence-continuum coupling. We evaluate the mass shifts and continuum mixing numerically for all $1S,1P$, and $2S$ charmonium valence states due to loops of $D,{D}^{*},{D}_{s}$, and ${D}_{s}^{*}$ meson pairs. We find that the mass shifts are quite large but numerically similar for all the low-lying charmonium states, as suggested by the first theorem. Thus, loop mass shifts may have been ``hidden'' in the valence quark model by a change of parameters. The two-meson continuum components of the physical charmonium states are also found to be large, creating challenges for the interpretation of the constituent quark model.
TL;DR: In this paper, the electromagnetic form factors of vector mesons are calculated in an explicitly Poincare covariant formulation, based on the Dyson-Schwinger equations of QCD.
Abstract: The electromagnetic form factors of vector mesons are calculated in an explicitly Poincare covariant formulation, based on the Dyson-Schwinger equations of QCD, that respects electromagnetic current conservation and unambiguously incorporates effects from vector meson poles in the quark-photon vertex. This method incorporates a two-parameter effective interaction, where the parameters are constrained by the experimental values of chiral condensate and f{sub {pi}}. This approach has successfully described a large amount of light-quark meson experimental data, including ground-state pseudoscalar masses and their electromagnetic form factors and ground-state vector meson masses and strong and electroweak decays. Here we apply it to predict the electromagnetic properties of vector mesons. The results for the static properties of the {rho} meson are as follows: charge radius =0.54 fm{sup 2}, magnetic moment {mu}=2.01, and quadrupole moment Q=-0.41. We investigate the quark-mass dependence of these static properties and find that our results at the charm quark mass are in agreement with recent lattice simulations. The charge radius decreases with increasing quark mass, but the magnetic moment is almost independent of the quark mass.
TL;DR: In this article, the meson-mass peaks of the AdS-Schwarzschild black hole background with embedded D7-brane probes were determined and the spectral functions at finite baryon density were investigated.
Abstract: We consider gauge/gravity duality with flavor for the finite-temperature field theory dual of the AdS-Schwarzschild black hole background with embedded D7-brane probes. In particular, we investigate spectral functions at finite baryon density in the black hole phase. We determine the resonance frequencies corresponding to meson-mass peaks as function of the quark mass over temperature ratio. We find that these frequencies have a minimum for a finite value of the quark mass. If the quotient of quark mass and temperature is increased further, the peaks move to larger frequencies. At the same time the peaks narrow, in agreement with the formation of nearly stable vector meson states which exactly reproduce the meson-mass spectrum found at zero temperature. We also calculate the diffusion coefficient, which has finite value for all quark mass to temperature ratios, and exhibits a first-order phase transition. Finally we consider an isospin chemical potential and find that the spectral functions display a resonance peak splitting, similar to the isospin meson-mass splitting observed in effective QCD models.
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TL;DR: Recently, many interesting new light hadron states were discovered experimentally, some of which do not fit into the quark model easily as discussed by the authors, and their possible interpretations are covered in this review.
Abstract: In the past four years we have witnessed the renaissance of the hadron spectroscopy. Many interesting new hadron states were discovered experimentally, some of which do not fit into the quark model easily. I will give a concise overview of these states and their possible interpretations. Topics covered in this review are: (1) candidates of new light hadrons including $p\bar p$ threshold enhancement, X(1835), X(1576), f0(1810), recent candidates of the 1-+ exotic mesons, Y(2175), $p\bar\Lambda$ threshold enhancement etc. (2) charmed mesons including p-wave non-strange charmed mesons, Dsj(2317) and Dsj(2460), recent candidates of higher excited charmed mesons, Dsj(2632) etc. (3) charmonium and charmonium-like states such as X(3872), Y(4260), X(3940), Y(3940), Z(3930) etc. The effect from the nearby S-wave open channels on the quark model spectrum above or near strong decay threshold is emphasized. Dynamical lattice simulations of DK and $D^0\bar D^{\ast 0}$ scattering and the extraction of their phase shift...
TL;DR: In this article, the one-loop chiral perturbation theory π π -scattering amplitude and dispersion theory in the form of the inverse amplitude method was used to study the quark-mass dependence of the two lightest resonances of the strong interactions, the f_0(600) (σ) and the ρ meson.
Abstract: We use the one-loop chiral perturbation theory π π -scattering amplitude and dispersion theory in the form of the inverse amplitude method to study the quark-mass dependence of the two lightest resonances of the strong interactions, the f_0(600) (σ) and the ρ meson. As the main results, we find that the rho π π coupling constant is almost quark mass independent and that the ρ mass shows a smooth quark-mass dependence while that of the σ shows a strong nonanalyticity. These findings are important for studies of the meson spectrum on the lattice.
TL;DR: How robust the theoretical prediction is is discussed, and it is shown that the discrepancy with experiment may be explained by a charged Higgs boson or a leptoquark.
Abstract: The measured rate for D{s}{+}-->l+nu decays, where l is a muon or tau, is larger than the standard model prediction, which relies on lattice QCD, at the 38sigma level We discuss how robust the theoretical prediction is, and we show that the discrepancy with experiment may be explained by a charged Higgs boson or a leptoquark
TL;DR: A review of the experimental status of glueballs can be found in this paper, where theoretical expectations of phenomenological models and QCD on the lattice are briefly discussed.
Abstract: Glueballs and other resonances with large gluonic components are predicted as bound states by Quantum Chromodynamics (QCD). The lightest (scalar) glueball is estimated to have a mass in the range from 1 to 2 GeV/c**2; a pseudoscalar and tensor glueball are expected at higher masses. Many different experiments exploiting a large variety of production mechanisms have presented results in recent years on light mesons with J(PC) = 0(++), 0(-+), and 2(++) quantum numbers. This review looks at the experimental status of glueballs. Good evidence exists for a scalar glueball which is mixed with nearby mesons, but a full understanding is still missing. Evidence for tensor and pseudoscalar glueballs are weak at best. Theoretical expectations of phenomenological models and QCD on the lattice are briefly discussed.
TL;DR: In this paper, the pion and sigma meson exchange potential were taken into account and a dynamical calculation of the system was performed for a loosely bound S-wave molecular state.
Abstract: After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the $D^0\bar{D}^{\ast0}$ system. The $\sigma$ meson exchange potential is repulsive from heavy quark symmetry and numerically important for a loosely bound system. Our analysis disfavors the interpretation of X(3872) as a loosely bound molecular state if we use the experimental $D^\ast D\pi$ coupling constant $g=0.59$ and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. Bound state solutions with negative eigenvalues for the $D\bar{D}^\ast$ system exist only with either a very large coupling constant (two times of the experimental value) or a large cutoff ($\Lambda \sim 6$ GeV or $\beta \sim 6$ GeV$^2$). In contrast, there probably exists a loosely bound S-wave $B\bar{B}^\ast$ molecular state. Once produced, such a molecular state would be rather stable since its dominant decay mode is the radiative decay through $B^\ast\to B \gamma$. Experimental search of these states will be very interesting.
TL;DR: In this article, the masses and decays of the scalar D s 0 ∗ (2317) and axial-vector D s 1 ∗(2460 ) charmed mesons are calculated consistently in the hadrogenesis conjecture.
TL;DR: In this article, the authors studied the off-shell dynamics of vector mesons explicitly and showed that their Dalitz decays provide a sizeable contribution to the dilepton invariant mass spectra up to about 0.5 GeV.
TL;DR: A fully reconstructed B-c -> J/psi pi signal was observed with the D0 detector at the Fermilab Tevatron p (p) over bar collider using 1.3 fb(-1) of integrated luminosity as mentioned in this paper.
Abstract: A fully reconstructed B-c -> J/psi pi signal is observed with the D0 detector at the Fermilab Tevatron p (p) over bar collider using 1.3 fb(-1) of integrated luminosity. The signal consists of 54 +/- 12 candidates with a significance that exceeds 5 standard deviations, and confirms earlier observations of this decay. The measured mass of the B-c meson is 6300 +/- 14(stat)+/- 5(syst) MeV/c(2).
TL;DR: The vector dominance of the electromagnetic form factors both for mesons and baryons arises naturally in holographic QCD, where both the number of colors and the 't Hooft coupling are taken to be very large, offering a bona-fide derivation of the notion of vector dominance as mentioned in this paper.
Abstract: The vector dominance of the electromagnetic form factors both for mesons and baryons arises naturally in holographic QCD, where both the number of colors and the 't Hooft coupling are taken to be very large, offering a bona-fide derivation of the notion of vector dominance. The crucial ingredient for this is the infinite tower of vector mesons in the approximations made which share features that are characteristic of the quenched approximation in lattice QCD. We approximate the infinite sum by contributions from the lowest four vector mesons of the tower which turn out to saturate the charge and magnetic moment sum rules within a few percent and compute them totally free of unknown parameters for momentum transfers ${Q}^{2}\ensuremath{\lesssim}1\text{ }\text{ }{\mathrm{GeV}}^{2}$. We identify certain observables that can be reliably computed within the approximations and others that are not, and discuss how the improvement of the latter can enable one to bring holographic QCD closer to QCD proper.