Measurements and Analysis

Elliptic Flow

In high-energy nuclear collisions a hot and dense system is created. This system will immediately expand due to its internal pressure. A possible spatial anisotropy of the reaction zone at this moment will result in an anisotropy of the final state particle distributions that we measure. The dominant feature is an elliptical deformation, also called elliptic flow. The strength of this elliptic flow contains information about the equation of state and the viscosity of matter. (contact: R. Snellings)

Parton Energy Loss

Highly energetic partons (i.e. quarks or gluons) are produced in the collisions. When they traverse the dense matter, which is created simultaneously, they will loose a significant fraction of their energy. This parton energy loss can be measured via the abundance of high momentum hadrons and also via particle correlations. It can be used to deduce information on the density of the hot and dense state. (contact: M. van Leeuwen)

Heavy Quark Production

Heavy quarks (charm or bottom) are particularly sensitive to the properties of the produced matter. Their measurement is challenging, as they are rare and unstable. We perform measurements of the spectra and correlations of hadrons containing heavy quarks. (contact: A. Grelli)

Direct Photon Production

Direct photons are considered to be the cleanest messenger of the initial and early phases of high-energy collisions, as they can leave the reaction zone after production without further interaction. We study extremely energetic photons to understand the initial distribution of quarks and gluons. We also attempt to study the emission of thermal photon radiation to measure the early temperature in the collisions – this can be done e.g. by measuring virtual photons and extrapolating the results to the case of real photons. (contact: M. van Leeuwen, T. Peitzmann)

Polarization and Magnetic Fields

When two atomic nuclei collide off-center then the hot and dense system created in the overlap zone is expected to rotate. In addition the nucleons not participating in the collision represent electric currents generating an intense magnetic field. The magnetic field could be as large as 10^18 gauss, orders of magnitude larger than the strongest magnetic fields found in astronomical objects. Proving the existence of the rotation and/or the magnetic field could be done by checking if particles with spin are aligned with the rotation axis or if charged particles have different production rates relative to the direction of the magnetic field. (contact: P. Christakoglou, P. Kuijer)