The current status of the Bonn-Gatchna partial wave analysis is
presented. The main attention will be devoted to the analysis of the
data with production of the baryon states in gamma-N collision where
new baryon states had been found. The results of the combined analysis
of these data, measured by the CLAS, CB-ELSA and MAMI collaborations
together with earlier measured data are presented....
Evidence for the scalar and the tensor glueball is reported. The evidence stems from an analysis of BESIII data on radiative $J/\psi$ data into $\pi^0\pi^0$, $K_SK_S$, $\eta\eta$, and $\phi\omega$. The coupled-channel analysis is contrained by a large number of further data. The scalar intensity is described by ten scalar isoscalar mesons, covering the range from $f_0(500)$ to $f_0(2330)$....
The Fermilab Muon g-2 Experiment recently reported their first result for the anomalous magnetic moment of the muon that differs from the Standard Model (SM) prediction by 4.2$ standard deviations. The error on the SM prediction, which is comparable in size to the experimental uncertainty, is entirely dominated by the determination of the hadronic contributions, which arise from the...
In this talk I will review dispersive an analytic methods that have been used used to determine, in a a model-independent way, the existence and properties of light scalar mesons from scattering data. These include dispersive pole determinations of the long debated f_0(500) or sigma, K_0*(700) or kappa and f0(980). We also discuss the combination of dispersive scattering data analyses with...
I will review recent progress in the calculation of the axial and induced pseudoscalar form factors of the proton and neutron within lattice QCD.
In particular, I will emphasise results computed using physical point ensembles. The PCAC and Goldberger-Treiman relations will be discussed as well as the strange axial form factors.
Hadron yields measured in Pb-Pb collisions by the ALICE experiment at the LHC are very well described by the statistical hadronization model, leading to the phenomenologial determination of the hadronization temperature, which is in a very good agreement with predictions from Lattice QCD. This applies not only for hadrons carrying the u,d,s quarks, but also to hadrons with charm quarks, in...
The observation, in hadronic collisions, of "ideal fluid" type behavior in systems of a comparatively small number of particles, presents a conceptual puzzle, since the way we usually derive hydrodynamics is via approximating "many" particles as a continuum. I will argue that making sense of this requires re-deriving relativistic hydrodynamics as a "bottom-up" theory, with no reference to...
We present our results on the study of the electromagnetic
conductivity in dense quark-gluon plasma obtained within lattice simulations with 𝑁𝑓=2+1 dynamical quarks. We employ stout improved rooted staggered quarks at
the physical point and the tree-level Symanzik improved gauge action.
The simulations are performed at imaginary chemical potential and the
Backus-Gilbert method is used to...
The chiral phase transition for different numbers of quark flavours
I will present the latest progress in describing ultra-dense matter within the gauge-gravity correspondence. Using the holographic Sakai-Sugimoto model, I will discuss the phase structure at nonzero baryon and isospin chemical potentials, in particular pointing out the coexistence of baryonic matter and a pion condensate. As an application, I will show how this holographic approach can be used...
Since the first positive measurement of the Λ-hyperon global spin polarization in heavy-ion collisions by STAR in 2017, the understanding of the nature of this phenomenon is one of the most intriguing challenges for the community. As relativistic fluid dynamics celebrates multiple successes in describing collective dynamics of the QCD matter in such reactions, the natural question arises...
Due to the recent STAR data on the polarization of the $\Lambda$ hyperons produced in heavy ion collisions, it is interesting to consider the QCD phase transition in a medium exhibiting persistent polarization. Since during the chiral phase transition, the quarks acquire dynamical mass and the conservation of the axial charge current $J^\mu_A$ is broken, the chiral chemical potential $\mu_A$...
Dense QCD matter can exhibit spatially modulated regimes. They can be characterized by particles with a moat spectrum, where the minimum of the energy is over a sphere at nonzero momentum. Such a moat regime can either be a precursor for the formation inhomogeneous condensates, or signal a quantum pion liquid. We introduce the quantum pion liquid and discuss the underlying physics of the moat...
Recently the LHCb Collaboration announced intriguing results on the double-J/psi production in proton-proton collisions. A coupled-channel interpretation of the measured di-J/psi spectrum is presented and a possible nature of the near-threshold state X(6200) is discussed.
In order to understand the nature of the XYZ particles, theoretical predictions of the various XYZ decay modes are essential. In this work, we focus on the semi-inclusive decay of heavy quarkonium hybrids into traditional quarkonium in the Born Oppenheimer EFT (BOEFT) framework. We present results of the decay rates for several heavy quark hybrids. We also develop a systematic framework in...
I discuss recent progress concerning the computation of the $\Pi_u$ and $\Sigma_u^-$ hybrid static potentials at small quark-antiquark separations. Such potentials are important for investigating masses and properties of heavy hybrid mesons in the Born-Oppenheimer approximation.
Recent lattice QCD studies of charmonium-like and bottomonium-like states will be presented. The masses and widths of charmonium-like states with isospin zero are extracted by considering the scattering on the lattice. We find conventional charmonia with J=0,1,2,3 in line with experiment and two exotic candidates just below D barD and Ds barDs thresholds. The bottomonium-like system with...
We study the hadronic production of $D$-wave states of $\bar b c$ quarkonium. The relative yield of such states is estimated for kinematic conditions of LHC experiments. The direct $B_c(D)$ production is complemented by NRQCD contributions being the same order $O(v^4)$. The NRQCD matrix elements are estimated within naive velocity scaling rule.
Recent results on heavy exotic hadrons obtained by the LHCb experiment are discussed:
- Tetraquarks with hidden charm (
X(3872),T_{cccc}(6900),Z_{cs}(4xxx)+,X(46xx)) - Pentaquarks with hidden charm (
P_c(4xxx)+,P_{cs}(4459)0) - Doubly charmed tetraquark (T_{cc}+)
Most of the results are based on an analysis of the full runs I and II LHCb dataset.
This talk is dedicated to...
We will describe the odderon discovery by the TOTEM and D0 experiments. The analysis compares the p pbar elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in pp collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeV. The two data sets disagree at the 3.4 sigma level and thus provide evidence for the t-channel exchange...
O.V. Selyugin
BLTPh JINR, 141980 Dubna, Russia
Many models predict that soft interactions will enter a new regime at the
LHC: given the huge energy, unitarization may play a crucial role as the central
part of the protons becomes black [1]. In most part, this depends on the
behaviour of the hadron potential at large distances. Our analysis of dσ/dt of
the TOTEM Collaboration data, carried...
The Precision Proton Spectrometer (PPS) is a subdetector of the CMS experiment that facilitates the study of Central Exclusive Production (CEP) in proton-proton collisions at the LHC, in standard data taking conditions, by measuring protons scattered at very small angles. It started operating in 2016 and collected more than 110 fb-1 throughout the LHC Run 2. In this talk the physics program of...
We discuss the central exclusive production (CEP) of f1 mesons in high-energy proton-proton collisions, where the diffractive pomeron-pomeron fusion process is expected to be dominant [1]. The theoretical results are calculated within the tensor-pomeron approach [2]. Two ways to construct the pomeron-pomeron-f1 coupling are discussed. First we consider phenomenological approach. We adjust the...
The Proton Precision Spectrometer is exploring gamma gamma collisions at high energy opening up a different window where to search for new physics beyond Standard Model. I will present the PPS potentiality looking for anomalies either for exclusive CEP or invisible particles production.
I will discuss recent results of quarkonium spectral functions and heavy quark diffusion coefficients. Our results are based on continuum extrapolated lattice correlation functions and spectral reconstructions that are constrained by perturbation theory.
We discuss thermal QCD phase transition for various number of flavours. We review the results for the transition from $N_f=3$ to larger values. We discuss the universality class for $N_f=2$, along the critical line for two massless light flavours and a third flavour whose mass serves as an interpolator between $N_f=2$ and $N_f=3$. We identify a possible scaling window for the 3D O(4)...
We compute the masses, decay constants and gluonic matrix elements on the $\eta$ and $\eta'$ mesons in lattice simulations across four lattice spacings with the light quark masses reaching down to the physical point. A comparison is made to the Large-$N_c$ chiral perturbation theory (ChPT) predictions and the NLO low energy constants are determined.
We study the interactions of a static quark-antiquark pair at non-zero temperature using realistic (2+1)-flavor lattice QCD calculations. The study consists of two parts: the first investigates the properties of Wilson line correlators in Coulomb gauge and compares to predictions of hard-thermal loop perturbation theory. As a second step we extract the spectral functions underlying the...
The recent confirmation of the Brookhaven measurement of the anomalous
magnetic of the muon by the Fermilab g-2 experiment has increased the
tension with the theory prediction for g-2 compiled in a 2020 White Paper.
The uncertainty of the theory prediction is entirely dominated by the
hadronic vacuum polarisation (HVP) and the hadronic light-by-light (HLbL)
contributions. I review the status...
The strong CP problem is one of the greatest puzzles in particle physics. It is fuelled by the absence of an electric dipole moment of the neutron. Peccei and Quinn proposed a new symmetry that suppresses CP-violating terms in the strong interactions, at the expense of predicting the existence of a new particle, the axion. In this talk I present a natural solution of the problem, arising...
This talk is devoted to machine learning methods applied to predict the critical behavior of lattice observables, in particular at the confinement / deconfinement phase transition in SU (2) and SU (3) gauge theories. We find that at the phase of deep deconfinement the neural network, trained on the lattice configurations of gauge fields as input data, finds correlations with the target...
Composite Higgs model often feature a new strongly interacting sector based on some gauge group and some number of fermions (flavors). The physical scale is typically set by the Goldstone decay constant $f_{PS}$ and a meson state with the appropriate quantum numbers is identified with the Higgs. The lightest vector meson in these scenarios is a potential new, so far undetected, particle. Its...
A major objective of lattice QCD is the computation of hadronic matrix elements. The standard method is to use three-point and four-point correlation functions. An alternative approach, requiring only the computation of two-point correlation functions is to use the Feynman-Hellmann theorem. In this talk we develop this method up to second order in perturbation theory, in a context appropriate...
We review the latest progress in lattice QCD calculations of x-dependent partonic distributions in the nucleon. These calculations rely on matrix elements probing spatial correlations between partons in a boosted hadron, that can be matched to light-cone correlations defining the relevant distributions. We discuss the recent theoretical and practical refinements of this strategy, as well as...
We investigate the properties of thermal magnetic monopoles in the high temperature phase of QCD with 2+1 flavours and physical quark masses, with a particular focus on their condensation and its possible relation with other non-perturbative features of strongly interacting matter.
The non-trivial ground-state vacuum fields of QCD generate quark and gluon condensates and form the foundation of matter. Using modern visualization techniques, this presentation examines the microscopic structure of these fields. Of particular interest are the centre vortices identified within the ground-state fields of lattice QCD. This vortex structure is illustrated through renderings...
When non-Abelian gauge fields in SU(3) QCD have a line-singularity leading to non-commutativity with respect to successive partial-derivative operations, the non-Abelian Bianchi identity is violated. The violation as an operator is shown to be equivalent to violation of the Abelian-like Bianchi identities. Then there appear eight Abelian-like conserved magnetic monopoles of the Dirac type in...
I present numerical evidence that the gauge+Higgs fields surrounding isolated charged fermions, in a variety of gauge Higgs theories, have a spectrum of localized excited states. This would appear as a mass spectrum of “elementary” fermions, taken to be static for simplicity.
I will discuss the possible relationship between confinement mechanism and the existence of mass gap in the Yang-Mills theory by respecting gauge symmetry.
It has been suggested that the Landau-gauge gluon propagator has complex singularities, which invalidates the Källén–Lehmann spectral representation. Since such singularities are beyond the standard formalism of quantum field theory, the reconstruction of Minkowski propagators from Euclidean propagators has to be carefully examined for their interpretation. In this talk, we present rigorous...
A longstanding question in QCD is the origin of the mass gap in the Yang-Mills sector of QCD, i.e., QCD without quarks. In Landau gauge QCD this is encoded in a mass gap of the gluon propagator, which is found both in lattice simulations and with functional approaches. While functional methods are well suited to unravel the mechanism behind the generation of such a mass gap, a fully...
4d gauge theories with massless fermions typically have axial U(1) transformations
that suffer from the ABJ anomaly. One can modify the theory of interest by adding
more fields in a way that restores the axial symmetry, and use it to derive rigorous
’t-Hooft anomaly matching conditions. These conditions are not valid for the original
theory of interest, but for the modified theory. We show...
We study four-dimensional gauge theories with arbitrary simple gauge group with 1-form global center symmetry and 0-form parity or discrete chiral symmetry. We canonically quantize on a three-torus in a fixed background field gauging the 1-form symmetry. We show that the mixed 't Hooft anomaly results in a central extension of the global-symmetry operator algebra. We determine this...
We discuss higher-loop calculations of renormalization-group (RG)
flows of quantum field theories. We focus on properties at infrared
fixed points of the RG in vectorial asymptotically free gauge
theories with various gauge groups and fermion contents, including the
anomalous dimensions of the fermion bilinear operator $\bar\psi\psi$.
We have calculated these with inputs up to five-loop order...
We present the results of a first-principles lattice study of the Chiral Separation Effect in finite-density gauge theory with dynamical fermions. We find that the CSE is well described by the free quark result in the high-temperature quark-gluon plasma phase. As one enters the confinement regime with broken chiral symmetry at chemical potential smaller than half of the pion mass, the CSE...
The effect of rotation changes the critical temperature in the phase diagram of hot and dense hadronic matter explored in heavy-ion collision experiments. The recent lattice-QCD calculation suggests that the rotation effect pushes up the critical temperature, and there has been some controversy over the interpretation of this result. In this talk, we use a parameter-free approach, which is the...
The influence of relativistic rotation on the confinement/deconfinement transition in gluodynamics has been studied within lattice simulation. The simulation is performed in the reference frame which rotates with the system under investigation, where rotation is reduced to external gravitational field. Different types of boundary conditions (open, periodic, Dirichlet) are imposed in...
The transport phenomena involving spin are instrumental in investigating quantum effects in many-body systems. In heavy-ion collisions, the recent measurement of spin polarization and spin alignment opens a new avenue to explore the properties of hot and dense QCD matter. Based on linear response theory and quantum kinetic equation, we have systematically studied spin-momentum correlation...
We present the first calculation of the jet transport coefficient $\hat{q}$ in quenched and (2+1)-flavor QCD on a 4-D Euclidean lattice. The light-like propagation of an energetic parton is factorized from the mean square gain in momentum transverse to the direction of propagation, which is expressed in terms of the thermal field-strength field-strength correlator. The leading-twist term in...
Briefly after the Big Bang, the early universe was in a high temperature and high density environment. In order to recreate this state of matter in the laboratory, mini bangs are created by colliding heavy ions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory and subsequently at the Large Hadron Collider (LHC) at CERN. In this talk I shall be covering on the...
State-of-the-art lattice QCD studies of hot and dense strongly interacting matter currently rely on extrapolation from zero or imaginary chemical potentials. The ill-posedness of numerical analytic continuation puts severe limitations on the reliability of such methods. We performed simulations of the QCD chiral transition at finite real baryon density with the more direct sign reweighting...
In this contribution I consider masses of chiral partners in the context of the chiral symmetry restoration at finite temperature. Using an effective quark model I first review the common situation where two mesonic chiral partners become nearly degenerate when temperature is increased above the chiral restoration one. Then I turn to an effective hadron theory for describing charm mesons where...
Chiral effective field theory is been advanced to a precision tool for analyzing low-energy few-nucleon dynamics. I will outline the foundations of this theoretical framework and discuss our recent and ongoing precision studies of the electromagnetic structure of light nuclei.
I present an overview about chiralspin symmetry and its relation with confinement and the deconfined phase of QCD, as well as its chirally restored phase. I focus on high temperature QCD and some interesting “truncated” lattice studies, proposing an alternative chiralspin group which would be worth to check at high temperature QCD.
This talk is intended as an introduction to the application of chiral effective field theory to lattice simulations of nuclear systems. I present work by the Nuclear Lattice Effective Field Theory Collaboration studying the connection between microscopic nuclear forces and nuclear structure and reactions. I also describe recent results calculating nuclear thermodynamics and the phase diagram...
We study the vacuum properties of hybrids by using the so-called extended Linear Sigma Model (eLSM). This model includes scalar and pseudoscalar mesons, as well as vector and axial-vector mesons. We enlarge the eLSM by including the low-lying hybrid nonet with exotic quantum numbers $J^{P C} = 1^{−+}$ and the nonet of their chiral partners with $J^{P C} = 1^{+−}$ to a global $U(3)_r\times...
We discuss the strong CP problem in the context of quantum field theory in the presence of horizons. We argue that general covariance places constraints on the topological structure of the theory. In particular, as in QCD, it means that different topological sectors of the theory can only sum incoherently, because the degrees of freedom beyond the horizon must be traced over for general...
