Conveners
Light meson spectroscopy: Session 1
- Juan Nieves (IFIC (CSIC-UV))
Light meson spectroscopy: Session 2
- Eugene Chudakov (Jefferson Lab)
Light meson spectroscopy: Session 3
- Bruno El-Bennich (Federal University of São Paulo)
Light meson spectroscopy: Session 4
- Stephan Paul (TU Munich)
Light meson spectroscopy: Session 5
- Marco Battaglieri (Istituto Nazionale di Fisica Nucleare)
The MesonEx experiment seeks to take advantage ofthe high luminosity electron scattering reactions and large acceptance CLAS12 detector in Hall B of Jefferson Lab. Inclusion of the small angle electron detector allows the tagging of low Q^2 quasi-real meson photoproduction. The high resolution detector systems allow reconstruction of events with missing particles, allowing reactions with...
We determine, from Lattice QCD, the elastic $\pi \pi$ scattering amplitude in the three possible isospin channels for various quark masses. We observe that the extraction of the $\sigma$ pole position is very challenging when the state becomes unstable. By performing a full dispersive analysis, we eliminate the systematic uncertainties associated with model extractions, constrain the low...
We establish the existence of the long-debated f0(1370) resonance in the dispersive analyses of meson-meson scattering data. For this, we present a novel approach using forward dispersion relations, valid for generic inelastic resonances. We find its pole at (1245±40)-i(300-70+30) MeV in ππ scattering. We also provide the couplings as well as further checks extrapolating partial-wave...
We present the new measurement of the cross section of $e^+e^-\to\pi^+\pi^-$ process in the center of mass energy range from 0.32 to 1.2 GeV. The measurement is based on analysis of more than 30 million pion pairs collected by CMD-3 detector at VEPP-2000 collider (Novosibirsk). We discuss the design of experiment, the key elements of data analysis, the comparison of our result with existing...
The measurement of exclusive$e^+e^-$ to hadrons processes is a significant part of the physics program of $BABAR$ experiment, aimed to improve the calculation of the hadronic contribution to the muon g−2 and to study the intermediate dynamics of the processes. We present the most recent studies performed on the full data set of about 470 $\text{fb}^{-1}$ collected at the PEP-II $e^+e^-$...
At BESIII, the lineshapes of e+e- ->phi eta', phi eta, KK, omega pi0, eta pipi, omega pipi are measured
from 2.0 to 3.08 GeV, where resonant structures are observed in these processes. Multiple lineshapes of
intermediate state are obtained by a partial wave analysis of e+e- ->K+ K- pi0 pi0, K+K- pi0 and the
structures observed provide essential input to understand the nature of...
The COMPASS experiment is a multi-purpose fixed-target experiment at the CERN SPS. Part of its physics program is the study of non-strange light mesons produced via diffractive scattering of $190\,\mathrm{GeV}/c$ $\pi^{-}$ off a liquid-hydrogen target. This gives access to the excitation spectrum of all isovector mesons $a_J$ and $\pi_J$ in multiple final states. The spin-exotic meson...
We examine whether an isovector vector meson with a mass around 1.26 GeV or $\rho(1250)$ is seen in the $e^{+} e^{-} \rightarrow \omega \pi^{0}$ process, whose existence was recently reinforced with a multichannel and fully unitary S-matrix analysis of elastic $\pi\pi$ scattering data with crossing-symmetry constraints by Hammound et al. [1]. The combined cross section data of that process...
Recently, performing a reanalysis of elastic $P$-wave $\pi\pi$ phase shifts and inelasticities [1], it is argued strongly that there existed an isovector vector meson with a mass around 1.26 GeV, that is $\rho(1250)$. Its existence has a long history and is still in a long-standing controversy both experimentally and theoretically, so that its entry to the PDG listings has not yet been...
KLOE and KLOE-2 collected the largest dataset at an electron-positron collider operating at the $\phi$ resonance peak ($\sim$ 8 fb$^{-1}$),
corresponding to the production of about 24 billion of $\phi$ mesons, namely 8 billion pairs of neutral K mesons and 300 million $\eta$ mesons.
A wide hadron physics program, investigating rare meson decays, $\gamma\gamma$ interaction, and dark...
The talk will report on the observation of the decay of the eta meson to four muons
The light meson regime still is not too well understood and holds many open questions that can only be answered using sophisticated analysis strategies to describe the data.
In particular, searching and investigating exotic states e.g. glueballs, hybrids and tetraquarks is a real challenge among the many broad and overlapping resonances, but represent a key point towards a better...
Hadron photoproduction is an essential experimental tool that gives important information on the spectroscopic and structural nature of hadrons. At large photon energies and low invariant mass of the $\pi\pi$ subsystem, the differential cross section is dominated by the prominent $\rho(770)$ resonance. At forward angles, the production of the $\rho$ is mostly diffractive, and exhibits a...
We have identified the decay modes of the $D_s^+ \to \pi^+ K^{*+} K^{*-} , \pi^+ K^{*0} \bar{K}^{*0}$ reactions producing a pion and two vector mesons. The posterior vector-vector interaction generates two resonances that we associate to the $f_0(1710)$ and the $a_0(1710)$ recently claimed, and they decay to the observed $K^+ K^-$ or $K_S^0 K_S^0$ pair, leading to the reactions $D_s^+ \to ...
According to lattice QCD results, the two lightest glueballs are the scalar ($J^{PC}=0^{++}$) and the tensor ($J^{PC}=2^{++}$). From the well known dilaton potential that depends on a single dimentionful parameter, $\Lambda_G$, we study the scattering of two scalar and two tensor glueballs. From the scattering of two scalar glueballs we find that, using a proper unitarization scheme, a bound...
We present a novel extraction of the pole position of the f0(980) from the available dispersive analyses of the $\pi\pi\to\pi\pi, \bar{K}K$ channels using an effective range expansion. Afterwards, we use a neural network as a classifier to investigate the possible nature of the state, finding that a molecular interpretation is the most likely.
The excitation spectrum of light mesons which are composed of up, down, and strange quarks, allows us to study QCD at low energies and is an important input to other analyses such as searches for $CP$ violation in hadronic $B$-meson decays. While the non-strange light-meson spectrum is already mapped out rather well, many predicted strange mesons have not yet been observed experimentally and...
The unpolarized twist-2 (leading) and twist-3 (subleading), T-even,
transverse-momentum dependent quark distributions in the pion are
evaluated for the first time by using the actual solution of a
dynamical equation in Minkowski space. The adopted theoretical framework
is based on the homogeneous Bethe-Salpeter integral equation with
an interaction kernel given by a ladder...
I present preliminary results of a partial-wave analysis of $\tau^-\to\pi^-\pi^-\pi^+\nu_\tau$ in data from the Belle experiment at the KEK $\mathrm{e}^+\mathrm{e}^-$ collider. I demonstrate the presence of the $\mathrm{a}_1(1420)$ and $\mathrm{a}_1(1640)$ resonances in $\tau$ decay and measure their parameters. I also present validation of our findings using a model-independent approach. ...
The $a_1(1260)$ is cleanly observed in $\tau$ decays and can therefore serve as a testbed for resonant three-body physics. The first calculation of a three-body resonance from lattice QCD and its mapping to the infinite volume is presented. In addition, the resulting three-body unitary amplitude is continued to complex energies allowing for the extraction of the $a_1$ pole and its branching...
The GlueX experiment at Jefferson Lab was specifically designed for precision studies of the light-meson spectrum. For this purpose, a photon beam with energies up to 12$\,$GeV is directed onto a liquid hydrogen target contained within a hermetic detector with near-complete neutral and charged particle coverage. Linear polarization of the photon beam with a maximum around 9$\,$GeV provides...
In this talk, recent results from the Joint Physics Analysis Center (JPAC) collaboration will be discussed, mainly based on 2006.01058 and 2304.09736. We will address the decays V to 3pi, with V either the omega or the J/psi meson, in the context of Khuri-Treiman equations. These allow a representation of a three-body decay amplitude that takes into account unitarity (final state interactions)...
In this contribution we discuss and present the holographic graviton soft-wall model
(GSW) description of the meson and glueball spectra. This model relies on a semi-classic
approximation of non perturbative QCD. We summarize the main results of Ref. [1]
where the scalar and tensor components of the glueball spectrum have been calculated.
In particular, we proposed to consider a graviton,...
We present a lattice QCD calculation of the electromagnetic form factor of the pion in the timelike region.
This calculation was performed on a lattice with N=2+1 dynamical quark flavors, with a heavier than physical pion mass of 284 MeV.
At this pion mass, the rho meson main contribution to pion-pion scattering and the timelike form factor appears in the elastic energy region.
The...
Analysis of vector and axial vector meson systems will give insight into the light quark meson spectrum. Vector-pseudoscalar final states provide access to a rich set of intermediate states, including those mentioned above, but their analysis is complicated by the non-zero spin of the vector meson. A resonance amplitude model in the reflectivity basis is used to perform a partial wave analysis...
