Recent work on a model computation of light hybrid properties are summarized and compared to lattice field theory. Applications to decay, production, and flavor mixing will be discussed.
Quantum Chromodynamics (QCD) provides a theoretical framework for understanding interactions among quarks and gluons within hadrons. However, the influence of gluonic excitations on hadron characteristics and structure remains uncertain. Recent discoveries of potentially ex- otic hadrons underscore the need for precise spectroscopic measurements to decipher the strong force. This discussion...
The GlueX experiment at Jefferson Lab has collected an unprecedented amount of data and will continue to do so on the production of light mesons with a polarized photon beam. These data can provide detailed insights into the photoproduction mechanisms, but their interpretation requires a parallel theoretical effort. In the high energy regime studied by GlueX, the photoproduction of single...
The GlueX experiment at Jefferson Lab probes the spectrum of light hadrons with a $6-12\text{ GeV}$ linearly polarized beam. We study the $\gamma p\to K_S K_S p$ channel at GlueX to investigate the production of light flavorless mesons with even spin, namely the $f$ and $a$ mesons. The $f_0$ states in the $1-2\text{ GeV}/c^2$ mass range are particularly interesting, as there are too many for...
The COMPASS experiment is a multi-purpose two-stage spectrometer located at the CERN SPS. One of its main goals is the investigation of the excitation spectrum of light mesons in diffractive reactions. One of the final states produced at COMPASS is $K_S^0 K^-$, in which only selected resonances, the $a_J$ states with even $J$, can appear at COMPASS’ high beam energies. Performing a...
The discovery of the pentaquark candidate in the amplitude analysis of Lb -> J/psi p K decays in 2015 has ignited an interest in heavy hadron spectroscopy at the LHCb experiment. This has lead to further discoveries of more pentaquark candidates at the LHCb experiment, notably in Bs -> J/psi p pbar and B -> J/psi Lambda p decays. A majority of these experimental discoveries rely heavily on...
In the helicity formalism the task of calculating the correct roations between two systems is non trivial. While it can be done in an analytical manner for three body decays, this is not the case for decays involving more particles. To reassure consistent treatment of quantization axes for particles with spin, a series of boosts and rotations has to be translated into one set of angles known...
B^{\pm} \to DK^+{\pm}, D—>K_S pi+ pi- and related decay modes provide an exceptionally precise way to measure the CP violating parameter gamma, one of the key measurements at LHCb and BELLE II. In order to avoid the theory uncertainties related to the description of the multi body D decay, model-independent methods are used - these use charm threshold (CLEO-c / BESIII data) to constrain the...
We present the first calculation in lattice QCD of the process $\gamma K \to K\pi$ in which the narrow $K^*$ vector resonance appears. Using a lattice on which the pion has a mass of 284 MeV, we determine the transition amplitude at 128 points in the $(Q^2, E_{K\!\pi})$ plane, and find suitable resonant scattering descriptions. We demonstrate the need to account for $S$--wave $K\pi$ elastic...
A precise and complete measurement of the excitation spectrum of light mesons allows us to study QCD in the non-perturbative regime and is an important input to other studies, e.g., of $B$ meson decays. While the non-strange light-meson spectrum is already mapped out rather well, the strange-meson spectrum may hold many surprises, as almost no new data have been available for the last 20...
The reproducibility of complex amplitude models from published papers poses a significant challenge in high-energy physics, hindering progress and reliability. If these models were readily reproducible, it would standardize verification, enhance community reanalysis, and improve the utility of MC generators. We propose a solution involving the serialization of amplitude models into a...
Electroproduction reactions reveal the structure of light baryon resonances. Recent results of a simultaneous analysis of $\pi N$, $\eta N$, and $K\Lambda$ electroproduction data with the Juelich-Bonn-Washington (JBW) approach are presented. The extraction of multipoles and their uncertainties is discussed, and preliminary results for transition form factors at the resonance poles are shown.
The exploration of nucleon structure and electromagnetic transitions from ground state to excited state is a cornerstone of nuclear physics research. Meson electro-production experiments have opened new avenues for investigating these phenomena, particularly in the 12 GeV era at Jefferson Lab with the CLAS12 spectrometer. The $\eta N$ final states, accessible only through isospin $I = 1/2$...
In order to connect theoretical predictions for the baryon spectrum in the non-perturbative energy regime to experimental data, coupled-channel approaches are the method of choice. In those approaches a simultaneous partial-wave analysis of multiple reactions with different initial and final states are performed.
I will present the framework of the Juelich-Bonn dynamical coupled-channel model...
Nowadays, experimentally observed states that are often assigned to the light meson or charmonium sector might indicate an exotic nature. Such exotic particles include glueballs, hybrids, and tetraquarks. Not only do these states pose a theoretical challenge, but experimentally it is often difficult to distinguish exotic and non-exotic matter and to characterise their nature. In such cases,...
We extend the scope of the extraction of the electromagnetic form factor of the pion, $f_\pi$, from lattice QCD.
In the past, the calculation of electroweak induced transitions to two hadron states has been restricted to the elastic region.
We implemented the technology required to calculate $f_\pi$ beyond the first inelasticity, specifically in a lattice with heavier than physical pions...
The sustainable use of energy should be fulfilled as well in the field of particle physics, especially considering that it has additional advantages. Over recent decades, the continuous increase of experimental data in high energy physics applications has led to a significant computational demand. In particular, time-consuming coupled channel analyses require sometimes fits with a hundred free...
The talk will discuss amplitude analyses techniques employed to study the spectrum of heavy mesons at LHCb.
Rare B meson decays like B->K* mu mu provide highly sensitive probes of physics beyond the standard model. Recent results show intriguing indications of discrepancies between standard-model prediction and observation. PWA techniques play a crucial role in these analyses, especially those related to the angular distribution of B->K( * ) mu mu. They are critical in understanding and properly...
The next generation of experimental facilities promises to extend current heavy spectroscopy efforts to electro- and photoproduction. I will summarize recent efforts from the JPAC collaboration in this sector which include predicting expected production rates for many exotic candidate XYZ states and amplitude analysis of conventional charmonium photoproduction. I will focus on interesting open...
The GlueX experiment has produced the world's largest data sample for peripheral photoproduction of mesons with a goal to expand our understanding of the strong interaction and search for hybrid mesons. The experiment at the Thomas Jefferson National Accelerator Facility utilizes the GlueX detector and a tagged linearly polarized photon beam that peaks between 8 - 9 GeV incident on a liquid...
Partial wave analysis (PWA) is often performed in one of two regimes: either the data is kinematically binned to remove assumptions about the dynamics, or parameterized models like Breit-Wigner functions are used to encode physical dynamics. The ability to bridge these regimes can provide additional flexibility in describing the underlying physics.
NIFTy[1], a probabilistic programming...
We present a partial-wave analysis of $\tau^-\to \pi^-\pi^-\pi^+ \nu_\tau$ decays using the world's largest sample of these decays from the Belle experiment at KEK, Japan.
We discuss the employed covariant tensor formalism and the treatment of large incoherent backgrounds in our sample.
We give preliminary results on light-meson resonances appearing in the $\pi^-\pi^-\pi^+$ system, including...
Accessing the hadron spectrum from Quantum ChromoDynamics (QCD) poses several challenges given its non-perturbative nature and the fact that most states couple to multi-particle decay modes. Although challenging, advances in both theoretical and numerical techniques have allowed us to determine few-body systems directly from QCD. A synergistic approach between lattice QCD and scattering theory...
Scattering of three pions is relevant for the analysis of axial resonances that can be studied on the lattice and in experiment. Conceptual developments of a finite-volume formalism (FVU) for the analysis of lattice data are presented, including coupled channels. Progress for infinite-volume coupled-channel systems and the effect of rescattering effects is reported, as well.
This talk presents study cases of the decay and production of hadrons with $c$-quark content from the point of view of effective field theories. A theoretical review of the $D^{+}_S\rightarrow K^+K^-K^+$ and $B\rightarrow H(c\bar{c})\;X$ decays is shown. The $D^{+}_S\rightarrow 3K$ $W$-radiation topology, also known as external $W$-emission, is introduced and visualized using Dalitz plots....
During the talk, I will discuss progress in applying the relativistic three-particle scattering formalism to systems of non-degenerate mesons of arbitrary angular momenta. For concreteness, I will focus on the $DD\pi$ system in the charm $C = 2$ and isospin $I = 0$ sectors, where the doubly charmed tetraquark $T_{cc}(3875)^+$ should appear as a pole in the elastic $3\to3$ scattering amplitude....
Ideally, we describe amplitude models with recognizable mathematical expressions and directly fit those models to large data sample with high performance. The ComPWA project achieves this by formulating models with a Computer Algebra System and using its symbolic expression trees as a code generation template for fast, computational back-ends like JAX.
We present...
The BESIII experiment is collecting e+e- annihilation data in the tau-charm region. A large number of datasets above the open-charm threshold with center-of-mass energies of up to 5 GeV allows detailed studies of both conventional charmonia and charmonium-like states. In this contribution, recent highlights and future plans for the spectroscopy of charmonium(-like) states will be presented.
The $\eta(1295)$ and $\eta(1405/1475)$ are assumed to be the candidates of the first radially-excited states of $\eta-\eta'$ and even the pseudo-scalar glueball. Ragarding to the recent BESIII $J/\psi\rightarrow\gamma K^0_S\bar{K}^0_S\pi^0$, we perform a dispersive analysis in the Khuri-Trieman framework which incoporates both the two- and three-body unitarity in the final state interactions....
Single-energy partial wave analysis has often been applied as a way to fit data with minimal model dependence. However, remaining unconstrained, partial waves at neighboring energies will vary discontinuously because the overall amplitude phase cannot be determined through single-channel measurement. This problem can be mitigated with the use of a constraining penalty function based on an...
The talk will cover the application of the Bayesian parameter-inference method to a truncated partial-wave analysis in pseudoscalar meson photoproduction. As an example, a dataset from the photoproduction of eta mesons is examined. The basics of the method as well as its possible limitations will be discussed.
A reliable determination of the pole parameters and residues of nucleon resonances is notoriously challenging, given the required analytic continuation into the complex plane. We provide a comprehensive analysis of such resonance parameters accessible with Roy-Steiner equations for pion-nucleon scattering - a set of partial-wave dispersion relations that combines the constraints from...
Machine learning offers many tools that can be exploited to understand physics. In this talk I will present how neural networks can help understanding the hadron spectrum, its properties and the underlying dynamics that leads to the formation of resonances.
Artificial Intelligence (AI) generative models have been successfully used in several field. In this contribution I will present results of the A(I)DAPT (AI for Data Analysis and Data PreservaTion) working group. Our objective is to develop AI-based tools to address the main challenges in Nuclear Physics and High Energy Physics measurements: unfold detector effects and preserve...
Resonances are characterized uniquely by their complex pole location and the
corresponding residues. On the other hand experimentally resonances
are typically identified as structures in amplitudes - in particular
branching ratios of resonances are determined as ratios of count rates. To make contact
between these quantities it is necessary to connect line shapes and...
We determine, from Lattice QCD, the elastic $\pi\pi$ scattering amplitude in the three possible isospin channels for various quark masses. We observe that, once the $\sigma$ becomes an unstable particle, its pole position is very noisy. By performing a full dispersive analysis, we drastically reduce the systematic uncertainties associated with model extractions, constrain the low energy...
The GlueX experiment at Jefferson Lab uses linearly polarized photoproduction to study the light quark meson spectrum and search for spin-exotic mesons. The linear polarization of the beam allows separation of the natural and unnatural production mechanisms in $t$-channel production. The production mechanisms of the axial vector $b_1(1235)$ meson can be measured via amplitude analysis of the...
Contrary to the general notion that the background part of resonant scattering amplitude must be large and complicated for broad resonances, we show that the size of background depends only on the geometry, more precisely, on the angle at which the resonant pole is "seen" from the threshold. We use an approximation which treats the threshold as a simple zero instead of a branch point [1,2],...
In this talk, we perform a comprehensive amplitude analysis on photon-photon scattering into pion&\eta and kaon pairs within the isovector channels. The coupled channel scattering of \pi\eta-K\bar{K}-\pi\eta' are taken into account, and the photon-photon reaction amplitudes are constrained based on the Au-Morgan-Pennington method, where the final states interaction theorem is imposed. The...
The ALICE detector at the LHC has undergone a major upgrade in the long shutdown 2019-2022 to be able to take data at much higher rates in Run 3 and beyond. I will present the various challenges of this upgrade, and will show first results of pion and kaon pairs in double gap events taken in pp collisions in Run 3. I will discuss the prospects of developing a partial wave analysis for these...
Commissioned in 2017, the CLAS12 spectrometer is the flagship detector system in Hall B at Jefferson Lab, replacing the previous spectrometer, CLAS, which operated from 1997 until 2012. CLAS12 enables large acceptance studies of electron-induced reactions using the now energy-doubled CEBAF electron beam, with access to quasi-real photoprodcution processes via the low-Q2 Forward Tagger. The...
I report the preliminary results of the Regge model study of the spin density matrix elements (SDMEs) of the $\Delta(1232)$ in the photoproduction reaction ${\vec\gamma} p \to \pi^-\Delta^{++}$. This reaction is being studied by GlueX in its ongoing efforts to understand the spectrum the light hybrid mesons. The intensity profile of the photoproduction of resonance(s) from a polarized photon...
A lattice QCD computation of the I=0 and S=-1 coupled channel \pi \Sigma - K N scattering amplitudes in the Λ(1405)region is detailed. We use a single ensemble of gauge field configurations with N_f = 2+ 1 dynamical quark flavors where the mass of the pion is around 200 MeV. Hermitian correlation matrices using both single baryon and meson-baryon interpolating operators for a variety of...
The intense photon fluxes of relativistic nuclei provide an opportunity
to study photonuclear interactions in ultra-peripheral collisions. Exclusive final states of vector mesons can be studied in the process $\gamma$ + A → meson + A. The measurement of photoproduced $\pi^+\pi^− \pi^+ \pi^−$ final states in ultra-peripheral Pb–Pb collisions at √sNN = 5.02 TeV is presented for the first time....
The High Acceptance Di-lepton Spectrometer (HADES) collaboration at GSI employs a pion beam to examine the characteristics of baryonic resonances and their decay channels. This pion-beam facility enables the generation of baryonic resonances at a fixed center of mass energy ($\sqrt{s}$), i.e. in the S-channel. Consequently, these beams possess a significant advantage over proton-induced...
