Vector Meson Masses Research Articles

Semileptonic D(s) → Aℓ+ν and nonleptonic D → K1(1270, 1400)π decays in LCSR

In this work, the transition form factors are calculated for the semileptonic D(s) → Aℓ+ν where A = a1, b1, K1(1270, 1400), i.e. , , and in the frame work of the light-cone QCD sum rules (LCSR) approach up to the twist-3 distribution amplitudes (DAs). Since the masses of these axial vector mesons are comparable to the charm quark mass, we keep out in our calculations all terms including mA/mc (all orders) in expansion of two-parton DAs. Branching ratio values are estimated for the semileptonic D(s) → Aℓν and nonleptonic D→K1 (1270, 1400) π decays. A comparison is also made between our results and predictions of other methods and the existing experimental values.

$\rho$-meson spectral function in hot asymmetric nuclear matter

The $\rho$-meson spectral function in hot and dense asymmetric nuclear matter (number densities of proton and neutron different) is evaluated in an effective chiral SU(3) model within the mean field approximation (MFA). The dependence of the vector meson masses on density and temperature, their variation with the asymmetry parameter, the form of the spectral function when the $ p \longleftrightarrow n$ symmetry is broken are studied. One can observe a clear splitting of the longitudinal and the transverse modes among the $\rho$ isospin multiplets. The role of a running tensor coupling on the spectral function is also studied.

On light vector mesons and chiral SU(3) extrapolations

A chiral extrapolation of the light vector meson masses in the up, down and strange quark masses of QCD is presented. We apply an effective chiral Lagrangian based on the hadrogenesis conjecture to QCD lattice ensembles of PACS-CS, QCDSF-UKQCD and HSC in the strict isospin limit. The leading orders low-energy constants are determined upon a global fit to the lattice data set. We use the pion and kaon masses as well as the size of the finite volume as lattice ensemble parameters only. The quark mass ratio on the various ensembles are then predicted in terms of our set of low-energy constants. An accurate reproduction of the vector meson masses and quark-mass ratios as provided by the lattice collaborations and the Particle Data Group (PDG) is achieved. Particular attention is paid to the ω−ϕ mixing phenomenon, which is demonstrated to show a strong quark mass dependence.

On pion and kaon decay constants and their chiral SU(3) extrapolations

We consider the dependence of the pion and kaon decay constants on the up, down and strange quark masses in QCD with strict isospin symmetry. The role of dynamical vector meson degrees of freedom is scrutinized in terms of an effective chiral Lagrangian for vector mesons. Applying a set of low-energy parameters as determined previously from QCD lattice data on the masses of the light vector mesons from PACS-CS, QCDSF-UKQCD and HSC we compute its implications on the pion and kaon decay constants for QCD lattice ensembles of HPQCD, CLS and ETMC. It is shown that with Gasser-Leutwyler L4 and L5 parameters fixed to the empirical decay constants an accurate reproduction of their values at unphysical quark masses as computed by HPQCD, CLS and ETMC is achieved. Results for the masses of the light vector meson, the ω−ϕ mixing angles and the quark mass ratios for the ensembles used by HPQCD, CLS and ETMC are discussed.

Hadron modification in a dense baryonic matter

Starting with the Strongly Correlated Quark Model of a hadron structure, SCQM, we demonstrate how the properties of mesons and baryons are modified in a hot and dense nuclear environment. These in-medium modifications can lead to observable effects in heavy ion collisions, such as enhancement of strangeness and dropping vector meson masses.

Analysis of Dalitz decays with intrinsic parity-violating interactions in resonance chiral perturbation theory

Observables of light hadron decays are analyzed in a model of chiral Lagrangian which includes resonance fields of vector mesons. In particular, transition form factors are investigated for Dalitz decays of $V\to Pl^+l^-$ and $P\to \gamma l^+l^-$ $(V=1^-, P=0^-)$. Moreover, the differential decay width of $P\to \pi^+\pi^-\gamma$ and the partial widths of $P\to2\gamma, V\to P\gamma, \eta^\prime\to V\gamma, \phi(1020)\to\omega(782)\pi^0$ and $V\to 3P$ are also calculated. In this study, we consider a model which contains octet and singlet fields as representation of $SU(3)$. As an extension of chiral perturbation theory, we include 1-loop ordered interaction terms. For both pseudoscalar and vector meson, we evaluate mixing matrices in which isospin/$SU(3)$ breaking is taken into account. Furthermore, intrinsic parity violating interactions are considered with singlet fields. For parameter estimation, we carry out $\chi^2$ fittings in which a spectral function of $\tau$ decays, vector meson masses, decay widths of $V\to P\gamma$ and transition form factor of $V\to Pl^+l^-$ are utilized as input data. Using the estimated parameter region in the model, we give predictions for decay widths and transition form factors of intrinsic parity violating decays. As further model predictions, we calculate the transition form factors of $\phi(1020)\to \pi^0l^+l^-$ and $\eta^\prime\to\gamma l^+l^-$ in the vicinity of resonance regions, taking account of the contribution for intermediate $\rho(770)$ and $\omega(782)$.

On the chiral expansion of vector meson masses

We study the chiral expansion of meson masses and decay constants using a chiral Lagrangian that was constructed previously based on the hadrogenesis conjecture. The one-loop self energies of the Goldstone bosons and vector mesons are evaluated. It is illustrated that a renormalizeable effective field theory arises once specific conditions on the low-energy constants are imposed. For the case where the hadrogenesis mass gap scale Lambda_{HG} is substantially larger than the chiral symmetry breaking scale Lambda_chi a partial summation scheme is required. All terms proportional to (M/\Lambda_\chi)^n can be summed by a suitable renormalization, where M is the chiral and large-N_c limit of the vector meson masses in QCD. The size of loop effects from vector meson degrees of freedom is illustrated for physical quarks masses. Naturally sized effects are observed that have significant impact on the chiral structure of low-energy QCD with three light flavours.

Large-Nc masses of light mesons from QCD sum rules for nonlinear radial Regge trajectories

The large-[Formula: see text] masses of light vector, axial, scalar and pseudoscalar mesons are calculated from QCD spectral sum rules for a particular ansatz interpolating the radial Regge trajectories. The ansatz includes a linear part plus exponentially degreasing corrections to the meson masses and residues. The form of corrections was proposed some time ago for consistency with analytical structure of Operator Product Expansion of the two-point correlation functions. We revised that original analysis and found the second solution for the proposed sum rules. The given solution describes better the spectrum of vector and axial mesons.

Meson masses in electromagnetic fields with Wilson fermions

We determine the light meson spectrum in QCD in the presence of background magnetic fields using quenched Wilson fermions. Our continuum extrapolated results indicate a monotonous reduction of the connected neutral pion mass as the magnetic field grows. The vector meson mass is found to remain nonzero, a finding relevant for the conjectured $\rho$-meson condensation at strong magnetic fields. The continuum extrapolation was facilitated by adding a novel magnetic field-dependent improvement term to the additive quark mass renormalization. Without this term, sizable lattice artifacts that would deceptively indicate an unphysical rise of the connected neutral pion mass for strong magnetic fields are present. We also investigate the impact of these lattice artifacts on further observables like magnetic polarizabilities and discuss the magnetic field-induced mixing between $\rho$-mesons and pions. We also derive Ward-Takashi identities for QCD+QED both in the continuum formulation and for (order $a$-improved) Wilson fermions.

Continuum extrapolation of quarkonium correlators at non-zero temperature

In the investigation of in-medium modifications of quarkonia and for determining heavy quark diffusion coeffcients, correlation functions play a crucial role. For the first time we perform a continuum extrapolation of charmonium and bottomonium correlators in the vector channel based on non-perturbatively clover-improved Wilson fermions in quenched lattice QCD. Calculations were done at 4 different lattice spacings, spatial extents between 96 and 192, aspect ratio from 1/6 to 1/2, for 5 temperatures between T/Tc = 0:75 and T/Tc = 2:2. We interpolate between different quark masses to match to the same vector meson mass over different lattice setups. Afterwards we extrapolate the renormalized correlators to the continuum. While we find a strong temperature dependence for charmonium, bottomonium states are only slightly affected at higher temperatures.

SU(3) sextet model with Wilson fermions

We present our final results for the SU(3) sextet model with the non-improved Wilson fermion discretization. We find evidence for several phases of the lattice model, including a bulk phase with broken chiral symmetry. We study the transition between the bulk and weak coupling phase which corresponds to a significant change in the qualitative behavior of spectral and scale setting observables. In particular the t0 and w0 observables seem to diverge in the chiral limit in the weak coupling phase. We then focus on the study of spectral observables in the chiral limit in the weak coupling phase at infinite volume. We consider the masses and decay constants for the pseudoscalar and vector mesons, the mass of the axial vector meson and the spin-1/2 baryon as a function of the quark mass, while controlling finite volume effects. We then test our data against both the IR conformal and the chirally broken hypotheses. Preprint: CP3-Origins-2017-49 DNRF90

Exclusive Charmonium Photo-Production at HERA and LHC with Color Glass Condensate**Supported by the National Natural Science Foundation of China under Grant Nos 11765005, 11305040, IRG11521064, 11775097 and 11465021, the Fund of Science and Technology Department of Guizhou Province under Grant No [2015]2114, and the Education Department of Guizhou Province under Grant No.KY[2017]004.

We calculate the exclusive charmonium photo-production in the framework of color glass condensate. To obtain a good description of the vector meson production experimental data at HERA, we introduce a vector meson mass dependent skewness factor into the skewness effect. Then we extend the skewness improved model to the LHC energies. The numerical results of our model are in good agreement with the J/ψ and ψ(2S) data in ultra-peripheral proton–proton collisions at LHC, which show the significance of the vector meson mass-dependent skewness factor. A prediction of the exclusive charmonium photo-production in ultra-peripheral nucleus–nucleus collisions is performed since it can provide a good way to test the effectiveness of the color glass condensate.

Light meson masses using AdS/QCD modified soft wall model

We analyze light vector and scalar meson mass spectra using a novel approach where a modified soft wall model with a UV cutoff is considered. Including this cutoff introduces an extra energy scale. For this model, we found that the masses for the scalar and vector spectra are well fitted within a very small root mean square (RMS) error for 14 of these states, with nonlinear trajectories given by two common parameters, the UV locus ${z}_{0}$, and the quadratic dilaton profile slope $\ensuremath{\kappa}$. We concluded that in this model the ${f}_{0}(500)$ scalar resonance cannot be fitted holographically as a $q\overline{q}$ state since we could not find a trajectory that included this pole. This result is in agreement with the most recent phenomenological and theoretical methods.

Delocalized SYZ mirrors and confronting top\u2013down SU(3)-structure holographic meson masses at finite g and N_c with P(article) D(ata) G(roup) values

Meson spectroscopy at finite gauge coupling – whereat any perturbative QCD computation would break down – and finite number of colors, from a top–down holographic string model, has thus far been entirely missing in the literature. This paper fills this gap. Using the delocalized type IIA SYZ mirror (with SU(3) structure) of the holographic type IIB dual of large-N thermal QCD of Mia et al. (Nucl Phys B 839:187. arXiv:0902.1540 [hep-th], 2010) as constructed in Dhuria and Misra (JHEP 1311:001. arXiv:1306.4339 [hep-th], 2013) at finite coupling and number of colors (N_c = number of D5(overline{D5})-branes wrapping a vanishing two-cycle in the top–down holographic construct of Mia et al. (Nucl Phys B 839:187. arXiv:0902.1540 [hep-th], 2010) = mathcal{O}(1) in the IR in the MQGP limit of Dhuria and Misra (JHEP 1311:001. arXiv:1306.4339 [hep-th], 2013) at the end of a Seiberg-duality cascade), we obtain analytical (not just numerical) expressions for the vector and scalar meson spectra and compare our results with previous calculations of Sakai and Sugimoto (Prog Theor Phys 113:843. doi:10.1143/PTP.113.843. arXiv:hep-th/0412141, 2005) and Dasgupta et al. (JHEP 1507:122. doi:10.1007/JHEP07(2015)122. arXiv:1409.0559 [hep-th], 2015), and we obtain a closer match with the Particle Data Group (PDG) results of Olive et al. (Particle Data Group) (Chin Phys C 38:090001, 2014). Through explicit computations, we verify that the vector and scalar meson spectra obtained by the gravity dual with a black hole for all temperatures (small and large) are nearly isospectral with the spectra obtained by a thermal gravity dual valid for only low temperatures; the isospectrality is much closer for vector mesons than scalar mesons. The black-hole gravity dual (with a horizon radius smaller than the deconfinement scale) also provides the expected large-N suppressed decrease in vector meson mass with increase of temperature.

Low-mass electron pairs from Au+Au collisions at 1.23A GeV with HADES

Lepton pairs are considered as an ideal probe to access the microscopic properties of strongly-interacting matter under extreme conditions of temperature and density. The spectral distribution of lepton pairs in the region below the low mass vector mesons is characterized by an excess radiation above contributions from late meson decays, the so-called hadronic cocktail. It is theoretically understood as a thermal radiation based on Vector Meson Dominance assuming a strong broadening of the in-medium spectral function due to coupling to baryons and anti-baryons.In continuation of a systematic investigation of the emissivity of strongly interacting matter, HADES has recently measured the dielectron emission in Au+Au collisions at 1.23A GeV beam energy. The first measurement for Au+Au completes the systematics of dilepton production in NN/pA/AA collisions in the SIS18 energy range.This contribution will present new results for the Au+Au system based on a data sample of 5.0 billion events of the 40% most central collisions.

Extended soft wall model with background related to features of QCD thermodynamics

The soft wall model is extended to accommodate at the same time (i) approximately linear $\rho$ meson Regge trajectories at zero temperature $T$, (ii) various options for the thermodynamics with reference to QCD (cross over or second-order transition or first-order transition at $T_c$), and (iii) the appearance of vector meson states at $T \leq T_c$. While the vector meson masses display some modest model dependence very near to $T_c$, they stay below $T_c$ to good accuracy independent of the temperature, that is nearly as at $T=0$, thus being very consistent with the thermo-statistical models widely employed in analyses of the hadron yields in relativistic heavy-ion collisions in a region where baryon densitiy effects can be neglected and the vacuum hadron masses are used.

Chiral imbalance in QCD

The chiral imbalance (ChI) is given by a difference between the numbers of RH and LH quarks which may occur in the fireball after heavy ion collision. To characterize it adiabatically a quark chiral (axial) chemical potential must be introduced taking into account emergence of a ChI in such a phase. In this report the phenomenology of formation of Local spatial Parity Breaking (LPB) in the hot and dense baryon matter is discussed and its simulation within a number of QCD-inspired models is outlined. The appearance of new states in the spectra of scalar, pseudoscalar and vector particles in such a matter is elucidated. In particular, from the effective vector meson theory in the presence of Chern-Simons interaction it is demonstrated that the spectrum of massive vector mesons splits into three polarization components with different effective masses. The asymmetry in production of longitudinally and transversely polarized states of ρ and ω mesons for various values of the dilepton invariant mass can serve as a characteristic indication of the LPB in PHENIX, STAR and ALICE experiments.

Statistical tweaks and meson masses

We compare lattice scales determined from the vector meson mass and the Wilson flow scale w_0 in QCD with two-flavours of rooted naive staggered fermions over a wide range of lattice spacing and quark mass. We find that the distributions of meson correlation functions are non-Gaussian. We modify the statistical analysis to take care of the non-Gaussianity. Current day improvements in the statistical quality of data on hadron correlations further allow us to simplify certain aspects of the analysis of masses. We examine these changes through the analysis of pions and apply them to the vector meson. We compare the flow scale determined using the rho mass with that using Lambda_{MSbar}.

Higgs Phase in a Gauge U(1) Non-Linear CP1-Model. Two Species of BPS Vortices and Their Zero Modes

In this paper, zero modes of fluctuation are dissected around the two species of BPS vortices existing in the critical Higgs phase, where the scalar and vector meson masses are equal, of a gauged U ( 1 ) nonlinear CP 1 -model. If 2 π n , n ∈ Z , is the quantized magnetic flux of the two species of BPS vortex solutions, 2 n linearly-independent vortex zero modes for each species are found and described. The existence of two species of moduli spaces of dimension 2 n of these stringy topological defects is thus locally shown.

Lattice study of largeNcQCD

We present a lattice simulation study of large $N_c$ regularities of meson and baryon spectroscopy in $SU(N_c)$ gauge theory with two flavors of dynamical fundamental representation fermions. Systems investigated include $N_c=2$, 3, 4, and 5, over a range of fermion masses parametrized by a squared pseudoscalar to vector meson mass ratio between about 0.2 to 0.7. Good agreement with large $N_c$ scaling is observed in the static potential, in meson masses and decay constants, and in baryon spectroscopy. This is an update of the published version of the paper (Phys. Rev. D94 (2016) 034506).