Webex link: https://asmeet.webex.com/asmeet/j.php?MTID=mcf453053cd16f7e25a8ebab5966a4633
The LHC discovery of Higgs boson at 125 GeV open a new area of high energy physics. Several models were proposed and being tested to solve the naturalness and triviality problems. We focus on SU(4)/Sp(4) composite Higgs model. In particular, with Dirac fermions in fundamental and 2-index antisymmetric representations, we are able to study the partial compositeness of the top quark. Combining lattice formulation and Hybrid Monte Carlo method, we can obtain correlators, then further, use them to analyse the spectrum of low-lying hadronic states. The masses of mesons and chimera baryons with partially quenched fermions will be presented as our preliminary results.
Quark confinement mechanism is one of unsolved important problems. In the dual superconductor picture of color confinement, it is considered that the color flux tube between quarks is caused by the condensation of color magnetic monopoles in the QCD vacuum. In this talk, we show new results of the dual Meissner effect in SU(3) gauge theory.
Measurement of the exclusive neutral pion electroproduction at Jefferson Lab Hall A experiment E12-06-114 Generalized Parton Distributions (GPDs) correlates the longitudinal momentum to the transverse position of the partons inside of a nucleon and therefore provides a 3D picture of it. GPDs can be studied via exclusive processes such as Deeply Virtual Compton Scattering (DVCS) or Deeply Virtual Meson Production (DVMP). In the exclusive production of $\pi^0$, the contribution from the longitudinally polarized virtual photon was expected to be dominating in the Bjorken limit, but it turned out not to be the case in the previous measurements with limited reach in $Q^2$. The large contribution from the transversely polarized photon has been suggested to be the consequence of the convolution of the transversity GPDs and the Distribution Amplitudes (DA) of the $\pi^0$. The Jefferson Lab Hall A experiment E12-06-014 extended the kinematic coverage in the quark valence regime and has measured the cross section of exclusive $\pi^0$ production off protons at $x_B$ in the quark valence domain (0.36, 0.48, and 0.60) with extended $Q^2$ coverage (3.1 to 8.4 $GeV^2$). In this talk, these results of the E12-06-014 measurement will be presented.
Kaon, as one of Nambu-Goldstone bosons of QCD, plays a similarly important role as the pion in understanding the strong interaction. Comparison of pion and kaon PDFs reveals how significant SU(3) symmetry breaking is. In this talk I will introduce the data sets used for constraining the kaon and review recent theoretical predictions.
The CERN COMPASS experiment measured the Drell-Yan production using a 190 GeV π- beam interacting with a transversely polarized NH3 target, and nuclear alumina and tungsten targets in 2015 and 2018. We obtain the differential cross sections of pion-induced Drell-Yan production in the kinematic regions of Feynman xF=-0.2-0.9 and transverse momentum pt=0.0-3.6GeV/c. This information is an important input in constraining the pion partonic structures. In this talk, the preliminary results of Drell-Yan cross sections will be presented and compared to the fixed-order QCD calculations with different pion PDFs. The kinematic dependence of the nuclear effect of Drell-Yan production will be investigated by contrasting the cross sections from three different targets.
Motivated by a novel origin of transverse single spin
asymmetry (SSA) in semi-inclusive Deep Inelastic Scattering (SIDIS) uncovered by us, we quantitatively investigate its impact on the theoretical understanding of the mechanism responsible for SSA. This new contribution from the quark-initiated channel first appears
in two-loop perturbation theory and involves the gT(x) distribution. This contribution is solely expressed in terms of twist-two polarized parton distribution functions and twist-two fragmentation functions in the Wandzura-Wilczek approximation, such that they can be unambiguously evaluated without introducing free parameters. We make predictions for measurements of SSA at the future Electron-Ion Collider (EIC), and find that they can reach up to 1-2\% even at the top EIC energy.
Recent observations of the spin polarization and alignments in RHIC and LHC have triggered intensive studies for vorticity-induced polarization and spin dynamics in relativistic fluids. In this talk, I will briefly review some of important issues and progresses for the spin polarization in heavy ion collisions. In particular, I will introduce the newly developed quantum kinetic theory (QKT) for investigating spin transport in weakly coupled quark gluon plasmas (QGP) and discuss its application to phenomenology. Moreover, I will mention how dynamically generated chromo-electromagnetic fields could affect dynamical spin polarization of quarks from QKT beyond the expected contributions from collisions. Such an effect is induced by the parity-odd correlators of background color fields in QGP. Although further studies are needed, the induced spin polarization of quarks from background color fields may possibly explain the spin alignment of vector mesons measured in LHC and reveal its connection with local parity violation.
The Berry phase is analyzed for Weyl and Dirac fermions in the worldline formalism, a first quantized representation of quantum field theories. A phase space construction is utilized making possible a manifestly relativistic intuitive extension of the fermion Hamiltonian of quantum mechanics. A classical chiral kinetic theory is constructed. Whereas the kinetic theory for Weyl fermions agrees exactly with 3 dimensional theories, the Dirac case possesses a richer structure. It is found for the classical worldline Dirac kinetic theory axial-vector terms are required to see a non-conservation of axial current in a quantum motivated distribution function resembling the Wigner function. However, while the Berry phase can give rise to the non-conservation of axial current in a classical kinetic theory, the Berry phase under the adiabatic theorem is also analyzed for the full quantum index theorem where it is shown adiabaticity is incompatible with the axial anomaly. Further contrasts with the similarity transform of the worldline Berry phase and axial rotation of the axial anomaly are provided by way of the Fujikawa method adopted for the coherent state on the worldline.