Search results for "Field Theory"
showing 10 items of 1188 documents
Heavy Quark Symmetries: Molecular Partners of the X(3872) and $Z_{b}(10610)/Z_{b}'(10650)$
2013
In this work, we have used an Effective Field Theory (EFT) framework based on Heavy Quark Spin (HQSS), Heavy Flavour (HFS) and Heavy Antiquark-Diquark symmetries (HADS). Using a standard lagrangian for the heavy meson-heavy antimeson system, we fit the counter-terms of the model to predict some promising experimental data that can be interpreted as heavy meson-heavy antimeson molecules, that is, the X(3872) and the $Z_{b}(10610)/Z'_{b}(10650)$. Next, and, taking advantage of HADS, we use the same lagrangian to explore the consequences for heavy meson-doubly heavy baryon molecules, which can also be interpreted as triply heavy pentaquarks.
Low-energy particle physics and chiral extrapolations
2012
In this review I discuss the role of chiral extrapolations for the determination of several phenomenologically relevant quantities, including light quark masses, meson decay constants and the axial charge of the nucleon. In particular, I investigate whether chiral extrapolations are sufficiently controlled in order to rightfully claim the accuracy which is quoted in recent compilations of these quantities. While this is the case for the masses of the light quarks and the ratio fK/fpi of decay constants, small inconsistencies in the chiral and continuum behaviour of individual decay constants fK and fpi, as well as the hadronic radii r0, r1 remain and must be clarified. In the case of the nu…
$$\bar K^{0*} (892)$$ andK 0*(892) production at lowp t and the quark parton model
1990
Data on the production of the neutralK*(892) resonances at lowpt by 200 GeVK− and π− is compared with the predictions of various models based on the quark parton model of hadrons.
CP-violating correlations in the reactione + e ?�hadrons
1991
We investigateCP-violating observables involving jets in the processe+e−»hadrons. These observables are sensitive to sources ofCP-violation beyond the standard model. We use an effective Lagrangian approach to parametrize possible newCP-violating interactions. Bounds on electric and weak diple moments of leptons and quarks are discussed.
Heavy quark symmetry at large recoil: the case of baryons
1993
We analyze the large recoil behaviour of heavy baryon transition form factors in semileptonic decays. We use a generalized Brodsky-Lepage hard scattering formalism where diquarks are considered as quasi-elementary constituents of baryons. In the limit of infinitely heavy quark masses the large recoil form factors exhibit a new model-independent heavy quark symmetry which is reminiscent but not identical to the Isgur-Wise symmetry at low recoil.
Inverse magnetic catalysis in nonlocal chiral quark models
2018
We study the behavior of strongly interacting matter under an external magnetic field in the context of nonlocal Polyakov-Nambu-Jona-Lasinio (PNJL) -like models. We find that at zero temperature the condensates display the well-known Magnetic Catalysis effect, showing a good quantitative agreement with lattice QCD results. Moreover, when extended to finite temperature we find that the Inverse Magnetic Catalysis effect is naturally incorporated.
Nonperturbative renormalization and O(a) -improvement of the nonsinglet vector current with Nf=2+1 Wilson fermions and tree-level Symanzik improved g…
2019
In calculating hadronic contributions to precision observables for tests of the Standard Model in lattice QCD, the electromagnetic current plays a central role. Using a Wilson action with $\mathrm{O}(a)$ improvement in QCD with ${N}_{\mathrm{f}}$ flavors, a counterterm must be added to the vector current in order for its on-shell matrix elements to be $\mathrm{O}(a)$ improved. In addition, the local vector current, which has support on one lattice site, must be renormalized. At $\mathrm{O}(a)$, the breaking of the $\mathrm{SU}({N}_{\mathrm{f}})$ symmetry by the quark mass matrix leads to a mixing between the local currents of different quark flavors. We present a nonperturbative calculation…
Quark Contraction Tool -- QCT
2016
We present a Mathematica package for the calculation of Wick contractions in quantum field theories - QCT. Furthermore the package aims at automatically generating code for the calculation of physical matrix elements, suitable for numerical evaluation in a C++ program. To that end commonly used algebraic manipulations for the calculation of matrix elements in lattice QCD are implemented.
Abelian dominance and the dual Meissner effect in local unitary gauges in SU(2) gluodynamics
2007
Performing highly precise Monte-Carlo simulations of SU(2) gluodynamics, we observe for the first time Abelian dominance in the confining part of the static potential in local unitary gauges such as the F12 gauge. We also study the flux-tube profile between the quark and antiquark in these local unitary gauges and find a clear signal of the dual Meissner effect. The Abelian electric field is found to be squeezed into a flux tube by the monopole supercurrent. This feature is the same as that observed in the non-local maximally Abelian gauge. These results suggest that the Abelian confinement scenario is gauge independent. Observing the important role of space-like monopoles in the Polyakov g…
Δ-baryon electromagnetic form factors in lattice QCD
2008
We develop techniques to calculate the four Delta electromagnetic form factors using lattice QCD, with particular emphasis on the sub-dominant electric quadrupole form factor that probes deformation of the Delta. Results are presented for pion masses down to approximately 350 MeV for three cases: quenched QCD, two flavors of dynamical Wilson quarks, and three flavors of quarks described by a mixed action combining domain wall valence quarks and dynamical staggered sea quarks. The magnetic moment of the Delta is chirally extrapolated to the physical point and the Delta charge density distributions are discussed.