The Compressed Baryonic Matter Experiment at FAIR: Progress with feasibility studies and detector developments

Abstract

The Compressed Baryonic Matter (CBM) experiment is being planned at the international research center FAIR, under realization next to the GSI laboratory in Darmstadt, Germany. Its physics programme addresses the QCD phase diagram in the region of highest net baryon densities. Of particular interest are the expected first order phase transition from partonic to hadronic matter, ending in a critical point, and modifications of hadron properties in the dense medium as a signal of chiral symmetry restoration. Laid out as a fixed-target experiment at the heavy-ion synchrotrons SIS-100/300, the detector will record both proton-nucleus and nucleus-nucleus collisions at beam energies between 10 and 45A GeV. Hadronic, leptonic and photonic observables have to be measured with large acceptance. The interaction rates will reach 10 MHz to measure extremely rare probes like charm near threshold. Two versions of the experiment are being studied, optimized for either electron-hadron or muon identification, combined with silicon detector based charged-particle tracking and micro-vertex detection. The CBM physics requires the development of novel detector systems, trigger and data acquisition concepts as well as innovative real-time reconstruction techniques. Progress with feasibility studies of the CBM experiment and the development of its detector systems are reported.

Examination of the species and beam energy dependence of particle spectra using Tsallis statistics

“…A combination of spectra of J/ψ and open charmed hadrons and/or their elliptic flow will enable us to break the correlation among β, T and q. All these improvements await low-energy scan at RHIC, and future charm measurements at FAIR, RHIC and LHC [49,50,51,52].…”

Viscosity, wave damping, and shock-wave formation in cold hadronic matter

“…At zero temperature the expression for the baryon density reduces to (16) and k F refers to highest occupied momentum level. The energy density and the pressure are given respectively by…”

“…Inserting (16) into (17) and into (18) we find the energy density and pressure as functions of the baryon density, respectively,…”

“…Since we consider only a pure QGP or a pure HG and do not study waves in the presence of phase changes, the real nature of the cold quark-hadron transition (which is not know) is not important in our work. A dense hadron gas may also exist and play a more important role in lower energy collisions, such as those which will be performed at FAIR [16]. Finally, a dense and cold hadron gas is expected to exist in the core of compact stars.…”

Particle identification

“…Driven by the environment in which TOF systems are planned to be operated in future experiments, a number of R&D projects currently address the rate limitation of Timing RPCs. The requirements for the TOF wall of the CBM experiment, for example, include a rate capability up to 25 kHz/cm 2 with a time resolution of 80 ps on a large system (120m 2 ) [64]. The effective drop of the operating voltage at larger rates (see Sect.…”