Jens Jørgen Gaardhøje

Nuclear Modification Factor for Charged Pions and Protons at Forward Rapidity in Central Au+Au Collisions at 200-GeV

We present spectra of charged pions and protons in 0–10% central Au+Au collisions at √sNN = 200 GeV at mid-rapidity (y = 0) and forward pseudorapidity (η = 2.2) measured with the BRAHMS experiment at RHIC. The spectra are compared to spectra from p + p collisions at the same energy scaled by the number of binary collisions. The resulting nuclear modification factors for central Au + Au collisions at both y = 0 and η = 2.2 exhibit suppression for charged pions but not for (anti-) protons at intermediate pT . The p̄/π− ratios have been measured up to pT ∼ 3 GeV/c at the two rapidities and the results indicate that a significant fraction of the charged hadrons produced at intermediate pT range are (anti-) protons at both mid-rapidity and η = 2.2.

Giant resonances at finite temperature: A probe of the structure of hot nuclei

Abstract Giant dipole resonances (GDR) built on excited nuclear states probe the structure of heated and rotating nuclei. In the lecture a review is given of the current status of experiments on the photon decay of excited state GDRs. These experiments provide information on the deformations and fluctuations of the shapes of hot rotating nuclei, and on the characteristics and limits of collective motion at high temperatures.

THE ALICE FORWARD MULTIPLICITY DETECTOR

The ALICE Forward Multiplicity Detector (FMD) is a silicon strip detector with 51,200 strips arranged in 5 rings, covering the range −3.4 < η < 5.1. It is placed around the beam pipe at small angles to extend the charged particle acceptance of ALICE into the forward regions, not covered by the central barrel detectors.

High Spin Phenomena in the Mass 100-200 Region Seen Through the Crystal Ball

The average properties of the gamma ray entry region and the decay from it are studied systematically, for 49 nuclear systems, in the spin spectrometer. Preliminary results are given for the mass the neutron number dependence of the gamma ray fold distribution and of unresolved γ spectra. The possibility of gating simultaneously on narrow regions of fold and excitation energy is exploited.

THE LASER OF THE ALICE TIME PROJECTION CHAMBER

The large TPC (95 m3) of the ALICE detector at the CERN LHC was commissioned in summer 2006. The first tracks were observed both from the cosmic ray muons and from the laser rays injected into the TPC. In this article the basic principles of operating the 266 nm lasers are presented, showing the installation and adjustment of the optical system and describing the control system. To generate the laser tracks, a wide laser beam is split into several hundred narrow beams by fixed micro-mirrors at stable and known positions throughout the TPC. In the drift volume, these narrow beams generate straight tracks at many angles. Here we describe the generation of the first tracks and compare them with simulations.

Limits of nuclear stability at finite temperature explored with giant resonances

Abstract Experimental investigations of the properties of giant resonances at finite temperature provide new insights into the interplay between the quantal and macroscopic properties of hot nuclei and into the limits of stability of the various nuclear phases. Here, we discuss recent investigations aiming at understanding the shapes of hot nuclei by measuring the angular distribution of high energy gamma rays emitted from well defined regions of excitation energy and spin, and new attempts to study the properties of superheavy atomic nuclei by measuring their gamma ray decay prior to fission.

Finite Temperature Giant Resonances

The properties of Giant Dipole Resonances (GDR) built on excited nuclear states are sensitive to the structure of heated and rotating nuclei. Experiments measuring the spectral and strength distribution of the high energy gamma rays emitted in the decay of excited state GDRs can thus provide information on the deformations and fluctuations of the shapes of hot rotating nuclei, and on the characteristics and limits of collective motion at high temperatures.