Dilepton production from both pion-pion and kaon-antikaon annihilation in heavy-ion collisions is studied using the relativistic transport model. The formation of a rho meson from pion-pion annihilation and a phi meson from kaon-antikaon annihilation, their propagation in the medium, and their decay into dileptons are explicitly treated. Including the medium modifications of the masses and widt...

We calculate the s-wave pion-pion scattering length in the isospin I = 2 channel in lattice QCD for pion masses ranging from 270 MeV to 485 MeV using two flavors of maximally twisted mass fermions at a lattice spacing of 0.086 fm. Additionally, we check for lattice artifacts with one calculation at a finer lattice spacing of 0.067 fm. We use chiral perturbation theory at next-to-leading order t...

The energy dependence of forward pion double charge exchange reactions on light nuclei is studied for both the Ground State transition and the Double-Isobaric-Analog-State transitions. A common characteristic of these double reactions is a resonance-like peak around 50 MeV pion lab energy. This peak arises naturally in a two-step process in the conventional pion-nucleon system with proper handl...

Despite its theoretical and practical importance, the pion structure is still badly constrained, particularly at low x π and in the sea-quark and gluon sectors. Recently ZEUS have presented data on dijet photoproduction with a leading neutron, which is dominated by slightly off-shell pion exchange and can be used to constrain the pion densities down to x π ≃ 0.01. We compare a recent NLO calcul...

We give reasons in support of the use of an effective intensity-dependent pion-nucleon coupling Hamiltonian for describing the properties of the pion multiplicity distribution and the corresponding factorial moments within the thermal-density matrix approach. We explain the appearance of the negative-binomial (NB) distribution for pions and the well-known empirical relation of Wróblewski . Our ...