Related papers: gamma* gamma -> pi pi at large Q^2
We evaluate the amplitude for gamma gamma --> pi^+ pi^- to two loops in the framework of chiral perturbation theory.The three new coupling constants that enter the result at this order in the low-energy expansion are estimated via resonance…
We discuss aspects of a covariant QCD modeling of meson physics by illustrating applications to several coupling constants and form factors. In particular, we cover the $\rho\pi\pi$ and $\pi^0 \gamma \gamma$ interactions, the $\rho$…
Precise measurement of the $\pi\pi$-phase shift $\delta^0_0(E)$ at very low energies would provide, for the first time, the experimental evidence in favour of or against the existence of a large quark condensate in the QCD vacuum, which is…
In this contribution the results from various transport models on different observables - considered as possible signals of the phase transition from hadronic matter to the quark-gluon plasma (QGP) - are briefly reviewed.
A distinct feature of Coulomb gauge QCD is that it can be formulated in terms of physical, transverse gluons and quarks alone. The state-counting is then transparent, and the gauge is suited for studies of the excited spectrum. Leaving…
The available experimental information is consistent with the Weinberg predictions for the threshold parameters of pi-pi-scattering. The data, however, only test those relations that are insensitive to the quark masses m_u and m_d. Recent…
Recent lattice calculations on the interaction energy of two heavy-light mesons (Q^2\bar{q}^2) are interpreted in terms of the potential of the corresponding single heavy-light meson (Q\bar{q}). This model leads to a large overestimate of…
It occurs that when we attempt to melt the nucleon in order to obtain the free quark gas, or QGP fluid the mass of the heat quantum (heaton) is equal to the pi-meson mass. Key words: Heat quanta; Quantum heat transport; Quantum diffusion…
The QCD (tri)critical point, a genuine second-order phase transition, implies existence of a massless scalar mode, and singular behavior near it. In this work we however focus on the finite region around it, defined by a condition…
We report the first complete leading-twist next-to-leading-order perturbative QCD predictions for the two-photon exclusive channels gamma gamma -> M+ M- (M=pi,K) at large momentum transfer. The asymptotic distribution amplitude is utilized…
We will discuss here some of the recent results obtained from lattice simulations of QCD at non-zero temperature. Such calculations aim at a quantitative understanding of the thermodynamics of strongly interacting matter in equilibrium. We…
Electromagnetic meson production formalisms are reviewed, with emphasise placed on their ability in search for new baryon resonances via gamma p -> K+ Lambda and gamma p -> eta p processes. The relevant studies, aiming to deepen our…
The parametrisation of the photon structure function in the low Q^2 region is formulated. It includes the VMD contribution and the QCD improved parton model component suitably extrapolated to the low Q^2 region. The parametrisation…
BRAHMS has the ability to study relativistic heavy ion collisions from the final freeze-out of hadrons all the way back to the initial wave-function of the gold nuclei. This is accomplished by studying hadrons with a very wide range of…
The notion of geometric phase has been recently introduced to analyze the quantum phase transitions of many-body systems from the geometrical perspective. In this work, we study the geometric phase of the ground state for an inhomogeneous…
A systematic study of the odd-intrinsic parity sector of QCD is presented. We briefly describe different applications including pi0 -> gamma gamma decay, muonic (g-2) factor and a test of the new holographic conjectures.
QCD predicts that the interactions between quarks and gluons change from a confining to a screened Yukawa form above a critical temperature $T_c\sim 150$ MeV. In this talk, I review some of the key observables in heavy ion reactions which…
The finite temperature QCD transition for physical quark masses is a crossover. For smaller quark masses a first-order phase transition is expected. Using Symanzik improved gauge and stout improved fermion action for 2+1 flavour staggered…
The study of electron-positron collisions at center-of-mass energies corresponding to charmonium production has reached new levels of sensitivity thanks to experiments by the BES and CLEO Collaborations. Final states $\gamma P$, where $P$…
After a brief summary of the QCD phase structure with light quarks, we discuss two recent developments on in-medium hadrons. First topic is the sigma-meson which is a fluctuation of the chiral order parameter \bar{q}q. Although sigma is at…