ALICE Apparatus Research Articles

Multiplicity dependence of the average transverse momentum in pp, p–Pb, and Pb–Pb collisions at the LHC

The average transverse momentum 〈pT〉 versus the charged-particle multiplicity Nch was measured in p–Pb collisions at a collision energy per nucleon–nucleon pair sNN=5.02 TeV and in pp collisions at collision energies of s=0.9,2.76, and 7 TeV in the kinematic range 0.15<pT<10.0 GeV/c and |η|<0.3 with the ALICE apparatus at the LHC. These data are compared to results in Pb–Pb collisions at sNN=2.76 TeV at similar charged-particle multiplicities. In pp and p–Pb collisions, a strong increase of 〈pT〉 with Nch is observed, which is much stronger than that measured in Pb–Pb collisions. For pp collisions, this could be attributed, within a model of hadronizing strings, to multiple-parton interactions and to a final-state color reconnection mechanism. The data in p–Pb and Pb–Pb collisions cannot be described by an incoherent superposition of nucleon–nucleon collisions and pose a challenge to most of the event generators.

Study of short-lived resonances with the ALICE Experiment at the LHC

The study of short-lived resonances allows the investigation of the collision dynamics and of the properties of the hot and dense medium created in high energy collisions. Moreover it is interesting to address the topics of the strangeness production by the analysis of strange resonances. First measurements of the ϕ(1020), Λ *(1520), K*(892), Ξ *(1530) and doubly charged Δ(1232) resonances in pp collisions at a center of mass energy of 7 TeV with the ALICE apparatus at the LHC are presented. Thermal model predictions of particle ratios in proton-proton collisions are shown.

Cosmic ray physics with ACORDE at LHC

The use of large underground high-energy physics experiments, for comic ray studies, have been used, in the past, at CERN, in order to measure, precisely, the inclusive cosmic ray flux in the energy range from 2·1010 ÷ 2· 1012 eV. ACORDE, ALICE Cosmic Rays DEtector, will act as Level 0 cosmic ray trigger and, together with other ALICE apparatus, will provide precise information on cosmic rays with primary energies around 1015 ÷ 1017 eV. This paper reviews the main detector features, the present status, commissioning and integration with other apparatus. Finally, we discuss the ACORDE-ALICE cosmic ray physics program.

Cooperative research in microgravity sciences during the French manned MIR missions

During the past ten years the French laboratories working in the field of fluids and material sciences had access to regular, long-lasting manned missions onboard the Russian MIR Space Station. Beyond the French scientific program that was performed with the ALICE apparatus, a cooperative research program was developed with DLR, NASA and RSA. This cooperation was based on bartered agreements that included the joint utilization of the instruments onboard the MIR station (ALICE, TITUS furnace from DLR, vibration device from RKK Energia) and the funding of dedicated cartridges (DLR) or thermostats (DLR and NASA), as well as launch services (NASA) by the Cooperating Agencies. We present a review of this program with a particular emphasis on its scientific results and on the progress that has been achieved in science and applications. They covered a large field of condensed matter physics, from material sciences to near-critical and off-critical phase separation kinetics and near critical fluid hydrodynamics (thermoacoustic heat transport and vibrational convection). The high microgravity relevance of all these investigations naturally led to outstanding results that was published in the world's best scientific journals. The analysis of the latest experiments performed during the PEGASUS mission shows they will not be an exception to that evaluation. Off-critical phase separation with NASA, pressure-driven piston effect and equiaxed solidification with DLR, heat transport under calibrated vibrations with RKK Energia, all will be presented. The conclusion will stress the international character of this microgravity research program, the conditions of its success and what can be gained from it in the perspective of the space station utilization.