Publications

Order by: publication date number of citations

• Masses of vector and pseudovector hybrid mesons in a chiral symmetric model

  Walaa I. Eshraim

  SciPost Phys. Proc. 6, 014 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We enlarge the chiral model, the so-called extended Linear Sigma Model (eLSM), by including the low-lying hybrid nonet with exotic quantum numbers $J^{PC}=1^{-+}$ and the nonet of their chiral partners with $J^{PC}=1^{+-}$ to a global $U(3)_r \times U(3)_l$ chiral symmetry. We use the assignment of the $\pi_1^{hyb}= \pi_1(1600)$ as input to determine the unknown parameters. Then, we compute the lightest vector and pseudovector hybrid masses that could guide ongoing and upcoming experiments in searching for hybrids.

  1 citation

• Confinement, mass gap and gauge symmetry in the Yang-Mills theory -- restoration of residual local gauge symmetry --

  Kei-Ichi Kondo, Naoki Fukushima

  SciPost Phys. Proc. 6, 013 (2022) · published 31 May 2022 | Toggle abstract · pdf

  In this talk we want to discuss the color confinement criterion which guarantees confinement of all colored particles including dynamical quarks and gluons. The most well-known criterion is the Kugo-Ojima color confinement criterion derived in the Lorenz gauge. However, it was pointed out that the Kugo-Ojima criterion breaks down for the Maximal Abelian gauge in which quark confinement has been verified according to the dual superconductivity caused by magnetic monopole condensations. We give the color confinement criterion based on the restoration of the residual local gauge symmetry which can be applied to the Abelian and non-Abelian gauge theories as well irrespective of the compact or non-compact formulation, and enables us to understand confinement in all the cases. Indeed, the restoration of the residual local gauge symmetry which was shown by Hata in the Lorenz gauge to be equivalent to the Kugo-Ojima criterion indeed occurs in the Maximal Abelian gauge for the SU(N) Yang-Mills theory in two-, three- and four-dimensional Euclidean spacetime once the singular topological configurations of gauge fields are taken into account. This result indicates that the color confinement phase is a disordered phase caused by non-trivial topological configurations irrespective of the gauge choice.

• Excitations of static isolated fermions in the Higgs phase of gauge Higgs theory

  Kazue Matsuyama, Jeff Greensite

  SciPost Phys. Proc. 6, 012 (2022) · published 31 May 2022 | Toggle abstract · pdf

  A spectrum of localized excitations of isolated static fermions has been discovered in several different gauge Higgs theories. In lattice numerical simulations, we show that the charged elementary particles can have the spectrum of excitations in the Higgs phase of SU(3) gauge Higgs theory, q=2 Abelian Higgs theory, Landau-Ginzburg theory, and in chiral U(1) gauge Higgs theory. Possibly these excited states of the isolated fermions can be observed in ARPES studies of conventional superconductors. Also, we consider that similar kinds of excitations could exist in other gauge Higgs theories, such as the electroweak sector of the Standard Model.

• Strong CP problem, electric dipole moment, and fate of the axion

  Gerrit Schierholz

  SciPost Phys. Proc. 6, 011 (2022) · published 31 May 2022 | Toggle abstract · pdf

  Three hard problems! In this talk I investigate the long-distance properties of quantum chromodynamics in the presence of a topological theta term. This is done on the lattice, using the gradient flow to isolate the long-distance modes in the functional integral measure and tracing it over successive length scales. It turns out that the color fields produced by quarks and gluons are screened, and confinement is lost, for vacuum angles |theta| > 0, thus providing a natural solution of the strong CP problem. This solution is compatible with recent lattice calculations of the electric dipole moment of the neutron, while it excludes the axion extension of the Standard Model.

• Central exclusive production of axial-vector f1 mesons in proton-proton collisions within the tensor-pomeron approach

  Piotr Lebiedowicz

  SciPost Phys. Proc. 6, 010 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We discuss the central exclusive production of $f_{1}$ mesons in proton-proton collisions. The diffractive pomeron-pomeron fusion process within the tensor-pomeron approach is considered. Two ways to construct the pomeron-pomeron-$f_{1}$ coupling are discussed. The theoretical calculation of coupling constants is a challenging problem of nonperturbative QCD. We adjust the parameters of the model to the WA102 experimental data. The total cross section and differential distributions are presented. Predictions for LHC experiments are given. Detailed analysis of the distributions in $\phi_{pp}$ the azimuthal angle between the transverse momenta of the outgoing protons can help to check different models and to study real pattern of the absorption effects.

  1 citation

• SU(3) hybrid static potentials at small quark-antiquark separations from fine lattices

  Carolin Schlosser, Marc Wagner

  SciPost Phys. Proc. 6, 009 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We summarize our recent lattice gauge theory computation of the $\Pi_u$ and $\Sigma_u^-$ hybrid static potentials at small quark-antiquark separations. We provide parameterizations of the resulting lattice data points, which can be used for investigating masses and properties of heavy hybrid mesons in the Born-Oppenheimer approximation.

• Inclusive decays of heavy quark hybrids

  Abhishek Mohapatra

  SciPost Phys. Proc. 6, 008 (2022) · published 31 May 2022 | Toggle abstract · pdf

  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 decays of heavy quarkonium hybrids into traditional quarkonium in the EFT framework. We begin with weakly coupled potential NRQCD effective theory that describes systems with two heavy quarks and incorporates multipole expansions and use it to develop a Born-Oppenheimer effective theory (BOEFT) to describe the hybrids and compute the semi-inclusive decay rates. We compute both the spin-conserving and spin-flipping decay rates and find that our numerical results of the decay rates are different from the previous studies. We also develop a systematic framework in which the theoretical uncertainty can be systematically improved.

• Double-J/ψ system in the spotlight of recent LHCb data

  V. Baru, X.-K. Dong, F.-K. Guo, C. Hanhart, A. Nefediev, B.-S. Zou

  SciPost Phys. Proc. 6, 007 (2022) · published 31 May 2022 | Toggle abstract · pdf

  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 proposed near-threshold state $X(6200)$ is discussed.

  1 citation

• Nucleon axial form factors from lattice QCD

  Constantia Alexandrou

  SciPost Phys. Proc. 6, 006 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We give an overview on the evaluation of the axial and pseudoscalar form factors of the nucleon within the lattice QCD formulation. We discuss recent results obtained from the analysisofNf =2+1+1twistedmassfermiongaugeensemblesgeneratedatphysical values of the pion mass. Besides evaluating the isovector form factors, and the PCAC and Goldberger-Treiman relations, we also discuss results for the strange and charm axial form factors. We provide a comparison with other recent lattice QCD results obtained with different discretization schemes of the fermion action.

  1 citation

• Some recent results on renormalization-group properties of quantum field theories

  Robert Shrock

  SciPost Phys. Proc. 6, 005 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We discuss some higher-loop studies of renormalization-group flows and fixed points in various quantum field theories.