We use the Covariant Spectator Theory (CST) to calculate the mass spectrum and relativistic vertex functions of mesons as quark-antiquark bound states in which at least one of the quarks is either a charm or bottom quark. The quark-antiquark bound-state equation in CST is, similar to the Bethe-Salpeter equation, an integral equation in which the kernel consists of two-particle irreducible...
We present results for the electromagnetic form factors of the $\rho$ meson obtained within point-form relativistic quantum mechanics. In our formalism for the calculation of the meson current we treat elastic electron-meson scattering as a Poincaré-invariant coupled-channel problem for a Bakamjian-Thomas mass operator. From the resulting invariant one-photon-exchange amplitude we extract the...
An NJL-type three-flavor quark model with a complete set of explicit
chiral symmetry breaking terms is extended to include vector and axial vector
effective interaction terms. A suitable bosonization procedure is implemented
and discussed. The bosonized Lagrangian is written up to quadratic order in the
bosonic fields and the role of the new interactions is analysed in detail. The
model's...
Holographic AdS/QCD models provide a tool for calculating the spectra of glueballs and light mesons and baryons. In this talk we discuss some recent AdS/QCD models that extend the hadronic description to the case of heavy vector mesons.
Then we consider the finite temperature version of such a model in order to represent the thermal effects of a medium like the plasma in the states of heavy...
Light meson ($\pi,\sigma, a_0$) properties in the environment with chiral im-
balance will be analyzed with the help of meson effective lagrangian
associated with QCD. New spatial parity violating decays of scalar
meson arise as a result of mixing of $\pi$ and $a_0$ mesons. The pion electro-
magnetic formfactor obtains an unusual parity-odd contribution. Pion
effective masses vanish in flight....
The Green's functions of QCD encode the properties of hadrons, with the appearance of (colour singlet) poles in n-point functions corresponding to bound-states and resonances. There are several techniques by which such information may be extracted, including lattice QCD and functional methods. We discuss recent progress in applying nPI effective action techniques to the systematic truncation...
I will review results for the light baryon spectrum, obtained from solving the genuine three-body equation as well as its quark-diquark simplification. The basic ingredients are QCD's n-point functions which are solved self-consistently. This allows for a combined description of baryons, light and heavy mesons, tetraquarks and other observables from the same underlying building blocks. The...
In this talk I review the status of an ongoing study that is aimed at solving the quark propagator Dyson-Schwinger equation (qDSE) in the complex domain. Knowledge of the propagator's analytic properties is required for bound state equations, but can also potentially provide insights into fundamental phenomena such as confinement through its spectral characteristics. Using only the infrared...
Questions about quantum field theories at non-zero chemical potential and/or real-time correlators are often impossible to investigate numerically due to the notorious sign problem. A possible solution to this problem is to deform the integration domain for the path integral in the complex plane. We describe a family of such deformations, built using the holomorphic gradient flow, that...
We propose a new theoretical method for the practical lattice QCD calculation at finite density as a possible solution of the sign problem in finite-density QCD. In this method, the fermionic determinant becomes real and non-negative, and therefore no sign problem appears and the practical numerical calculation can be performed in lattice QCD.
The lattice Landau gauge gluon propagator at finite temperature is computed including the non-zero Matsubara frequencies. Furthermore, the Källén-Lehmann representation is inverted and the corresponding spectral density evaluated using a Tikhonov regularisation together with Morozov discrepancy principle. Implications for gluon confinement are also discussed.
I review important aspects of the interplay between center vortices and topological charge.
In the top-down holographic model of QCD based on D4/D8-branes in type IIA string theory and some of the bottom up models, the low energy effective theory of mesons is described by a 5 dimensional Yang-Mills-Chern-Simons theory in a certain curved background with two boundaries. The 5 dimensional Chern-Simons term plays a crucial role to reproduce the correct chiral anomaly in 4 dimensional...
QCD-like theories provide testing grounds for truncations of functional equations at non-zero density, since comparisons with lattice results are possible due to the absence of the sign problem. As a first step towards such a comparison, we determine for various theories the chiral and confinement/deconfinement transitions from the quark propagator Dyson-Schwinger equation by calculating the...
We study two types of excited vector mesons, radially excited vector mesons characterised by quantum numbers $n \hspace{0.15cm} ^{2s+1}L_J = 2 ^{3}S_{1}$ and angular-momentum excited vector mesons with quantum numbers $n \hspace{0.15cm}^{2s+1}L_J = 1 ^{3}D_{1}$. We evaluate the decays of these mesons into pseudoscalar and ground-state vector mesons. By using an effective relativistic QFT...
Glueballs, i.e. bound state of gluons, were predicted to exist in the very early days of QCD. This expectation has been confirmed by numerous lattice calculations. However, glueballs could not yet be experimentally identified. While in the low-energy sector (below 2.6 GeV) some candidates exist, in the high-mass sector (between 2.6-5 GeV) the situation is not satisfactory. In this talk,...
Masses and decays of excited scalar and pseudoscalar $\bar{q}q$ states are studied in depth within the Extended Linear Sigma Model (eLSM). The model also contains ground-state scalar, pseudoscalar, vector and axial-vector mesons. The main objective is to investigate the hypothesis that the $f_0(1790)$ resonance, observed a decade ago by the BES Collaboration and recently by LHCb, represents an...
Here we will discuss a recent dispersive determination of pion-kaon scattering and the use of analytic methods to extract the parameters of the poles associated to light strange resonances, without assuming a specific model.
The experimental investigation of hadrons is an unique way to understand how QCD behaves at the low-energy non-perturbative scale, where the bulk of the Universe visible mass exists. The search for "exotic" states, in particular, could permit to access further degrees of freedom of the theory that are characteristics of these particles, behind those of the Constituent Quark Model that well...
Besides the unitarity and symmetry requirements for a multi-resonance scattering amplitude, several other natural conditions can easily exclude unrealistic proposals. In particular, the behaviour of singularities under the variation of model parameters yield important information. We discuss how resonance poles should move in the complex-energy plane when coupling constants and masses are...
Modern approaches to mesons and baryons go beyond the traditional description in terms of pure valence quark-antiquark or three-quark systems confined by some infinitely rising interquark potential inspired by QCD. As most hadrons are broad to very broad resonances, with decay widths often of the same order of magnitude as the average level splittings, pretending that they are stable systems...
We perform calculations for the $\eta_c \to \eta \pi^+ \pi^-$ decay using elements of SU(3) symmetry to see the weight of different trios of pseudoscalars produced in this decay, prior to the final state interaction of the mesons. After that, the interaction of pairs of mesons, leading finally to $\eta \pi^+ \pi^-$, is done using the chiral unitary approach. We evaluate the $\pi^+ \pi^-$ and...
We will report on recent results of the KLOE-2 experiment on
the measurement of the running of the fine structure constant below 1 GeV, and the search for the light gauge boson in the mass range below 1 GeV.
We present the derivation of second-order relativistic viscous hydrodynamics from an effective Boltzmann equation for a system consisting of quasiparticles of a single species. We consider temperature-dependent masses of the quasiparticles and devise a thermodynamically-consistent framework to formulate second-order evolution equations for shear and bulk viscous pressure corrections. The main...
We analyse the role of the excited Baryonic spectrum in Quark Hadron Duality.
Statistical moments of particle multiplicities in heavy-ion collision experiments are an important probe in the exploration of the phase diagram of strongly-interacting matter and, particularly, in the search for the QCD critical endpoint. In order to appropriately interpret experimental measures of these moments, however, it is necessary to understand the role of experimental limitations, as...
We study the fluctuations and correlations of the average transverse momentum of particles emitted in heavy-ion collisions. The momentum fluctuations are related to event-by-event fluctuations of the size and entropy of the initial source. Hydrodynamic calculations using a Glauber model with quark degrees of freedom reproduce the data. We study correlation of the average transverse momentum...
We will illustrate how our recently developed
nonperturbative variational technique combined with renormalization group (RG) properties efficiently resums perturbative expansions in thermal field theories. The resulting convergence and scale dependence of optimized thermodynamical quantities are drastically improved as compared to standard perturbative expansions, as well as to other related...
I shall report on two unitary coupled channels works where the Λc(2595) (1/2- ) and Λc(2625) (3/2-) states are generated on one side and the Xi_c^0 (2790), Xi_c^0 (2815) are generated in another case. After that I shall show the formalism by means of which these resonances are produced in the decays of Lambda_b and Xi_b, with results and comparison with experiment.
COMPASS is a fixed-target experiment that was put in operation in 2002 at CERN (SPS, M2 beamline). An important part of its physics programme is the exploration of the transverse spin structure of the nucleon via measurements of spin (in)dependent azimuthal asymmetries in semi-inclusive DIS and, recently, also in Drell-Yan processes. Drell-Yan measurements with a $\pi^-$ beam interacting with...
The significant increase of the centre-of-mass energy of the Large Hadron Collider (LHC) from 8 to 13 TeV has allowed the LHC experiments to explore previously inaccessible kinematic regimes in their search for phenomena beyond the Standard Model (BSM).
Many BSM theories predict new phenomena accessible by the LHC. Searches for new physics models are performed using the ATLAS experiment at the...
Studies of meson spectra via strong decays provide insight regarding QCD at the
confinement scale. These studies have led to phenomenological models for QCD
such as the constituent quark model. However, QCD allows for a much richer
spectrum of meson states which include extra states such as hybrids, exotics,
multi-quarks, and glueballs. Within the past two decades a number of
experiments...
Gamma-Ray Bursts (GRBs) are the brightest events in the universe since the big bang. Detailed studies of the electromagnetic emission from these transient events have show that the short GBRs are likely associated with the merger of two compact objects such as neutron stars. With the start of gravitational wave detection a new window is opened to study these events and their progenitors. The...
Two-particle correlations measurements of $v_{n}$ (n=2-4) in 8.16 TeV pPb collisions, and event-by-event correlations of different $v_{n}$ measured using symmetric cumulants in 13 TeV pp, 5.02 and 8.16TeV pPb and 5.02 TeV PbPb collisions at the LHC. These new results give important insights to the origin of collectivity observed in small collision systems. Additionally, using the scalar...
Starting from local equilibrium distribution functions for particles and antiparticles with spin 1/2, which are generalised to two by two hermitian matrices to include spin degrees of freedom, and using the conservation laws for energy, momentum and angular momentum, we derive hydrodynamic equations for the local temperature, chemical potential and hydrodynamic flow, as well as for the spin...
The Color Glass Condensate picture, or shockwave formalism, provides the non-planar extensions of the non-linear extension of the BFKL formalism for low-x physics. In such a framework, we will detail how to obtain IR- and UV-finite impact factors for two exclusive diffractive processes at one-loop accuracy.
The NA48/2 experiment presents a final result of the charged kaon semileptonic decays form factors measurement based on 4.28 million $K^\pm_{e3}$ and 2.91 million $K^\pm_{\mu 3}$ selected decays collected in 2004. The result is competetive with other measurements in $K^\pm_{\mu 3}$ mode and has a smallest uncertainty for $K^\pm_{e3}$, that leads to the most precise combined $K^\pm_{l3}$ result...
The cross section of the process $e^+e^- ->\mu^+\mu^-$ is calculated within hadronic polarization taken into account. The interference effects in vicinity of $\phi$ and $\omega$ mesons are calculated (not only) from $\sigma(e^+e^- -> hadrons)$ and compared with available experiments.
Relativistic hydrodynamics has been a fundamental tool to understand the evolution of matter in heavy-ion experiments at RICH and LHC. Despite the success of second order viscous hydrodynamics in reproducing collective behavior and particle spectra, there are still theoretical shortcomings that may question the validity of the approach in heavy-ion experiments conditions. Large gradients and...
NA61/SHINE at the CERN SPS is a fixed-target experiment pursuing a rich physics program including measurements for heavy ion, neutrino and cosmic ray physics. The main goal of the ion program is to study the properties of the onset of deconfinement and to search for the signatures of the critical point.
In this contribution the latest NA61/SHINE results on particle spectra as well as on...
Ultrarelativistic heavy ion collisions at the LHC produce the Quark Gluon Plasma. Jets are a useful probe to study this state of matter as they are produced at the early stages of the collisions and are expected to be modified as propagating through the medium. One observable is the energy loss lowering the jet yields at a given transverse momentum. Other observables are the modification of...
Parameterizations of the pp scattering data at the LHC collision
energies indicate a hollow in the inelasticity profile of the pp
interaction, with, curiously, less absorption for the
head-on collisions than for collisions at a non-zero
impact parameter. We argue that the hollowness in the impact
parameter is a quantum effect; it precludes models of inelastic
collisions where inelasticity...
Rather convincing evidence is discussed for the possible existence of a boson with a mass of about 38 MeV. Furthermore, it is shown that a boson with mass of 57.5 GeV might exist.
According to recent measurements, the mass of jets created in LHC energy pp collisions has broad fluctuation. Typically, the mean mass of a jet with transverse momentum 200-600 GeV/c is around 40-100 GeV/c^2, so the ratio (jet mass)/(jet energy) is of order 0.2. As this value is not negligibly small, as required for factorisation to be applicable, the virtualitis of partons created in the hard...
