Prospects for strangeness and charm measurements with the CBM experiment

Volker Friese (1)

1 GSI - Helmholtz zentrum für Schwerionenforschung GmbH

The CBM experiment will investigate strongly interacting matter at extreme densities at the future accelerator facility FAIR in Darmstadt, in search for the first-order phase transition from confined to deconfined matter. Key observables of CBM are strange and charmed hadrons. We discuss the performance of the planned experimental setup with respect to the measurement of strange and multi-strange hadrons, open charm and charmonium, based on detailed detector simulations which include a realistic detector response. Prospects for strangeness and charm measurements with the CBM experiment 2 1. The CBM experiment The interest in the high-density part of the QCD phase diagram and its features, namely the possible first-order phase transition from confined to deconfined matter, the critical endpoint separating the first-order transition region from that of a cross-over at lower densities, and the properties of hadrons in a dense environment, reflect in several experimental activities in accelerator laboratories around the world: the RHIC energy scan programme, the NA61 activities at CERN-SPS, the NICA project at JINR Dubna, and the CBM project at the future facility FAIR in Darmstadt [ 1 ]. Amongst them, the fixed-target experiment CBM provides the unique opportunity to study extremely rare probes like charmed hadrons, which are close to their production thresholds at FAIR beam energies (10- 45A GeV). This opportunity is due to the high beam intensities to be delivered by the SIS-300 synchrotron of FAIR (up to 10 9 ions/s), giving rise to interaction rates of up to 10 MHz with a typical 1 % interaction target. CBM is being designed to measure hadronic, leptonic and photonic observables in a large acceptance, covering the full p t range and rapidities from centre-of-mass rapidity close to beam rapidity. The planned experimental setup is shown in the left panel of Fig. 1. The core tracker (STS), consisting of eight stations of Silicon microstrip detectors, is located between the yokes of a super-conducting dipole magnet. Close to the target, the Micro-Vertex Detector (MVD) provides excellent resolution of displaced vertices from open charm decays. Downstream of the STS, a RICH and several layers of Transition Radiation Detectors (TRD) provide electron identification in a large momentum range. The TRD also serves for global tracking, connecting the tracks reconstructed in the STS with the time-of-flight wall located approximately 10 m downstream of the target. An electromagentic calorimeter after the TOF detector enables the measurement of neutral particles. The setup is completed with a downstream calorimeter (PSD) for event characterisation in terms of centrality and reaction plane angle. For muon measurements, the RICH will be replaced by an absorber system interlayed with several tracking detector planes, allowing to follow the tracks reconstructed in the main tracker through the setup (right panel of Fig. 1). In the following, we present results of physics performance studies in this detector system. They are based on the simulation of signals embedded into typical background events generated by UrQMD [ 2 ]. If not mentioned otherwise, all results refer to the collision system Au+Au at 25A GeV beam momentum. The results were obtained with full detector response simulation and event reconstruction.

Mots clés: Physical Sciences

Volker Friese. Prospects for strangeness and charm measurements with the CBM experiment. Journal of Physics G: Nuclear and Particle Physics, 2010, 37 (9), pp.94025. ⟨10.1088/0954-3899/37/9/094025⟩. ⟨hal-00600844⟩