Proton-Proton Physics with ALICE

The goal of the ALICE experiment at LHC is to study strongly interacting matter at high energy densities as well as the signatures and properties of the quark-gluon plasma. This goal manifests itself in a rich physics program. Although ALICE will mainly study heavy-ion collisions, a dedicated program will concentrate on proton-proton physics. The first part will introduce the ALICE experiment from a pp measurement's point of view. Two unique properties are its low pT cut-off and the excellent PID capabilities. The various topics of the proton-proton physics program, which will allow a close scrutiny of existing theoretical models, will be described. Furthermore, the interpretation of measurements of heavy-ion collisions necessitates the comparison to measurements of pp collisions. The second part will concentrate on the day-1 physics program of ALICE. At startup, neither the LHC luminosity nor its energy will have their nominal values. Furthermore, the ALICE detector is in the process of being aligned and calibrated. Still several physics topics can be studied from the very beginning. These will be presented as well as the effort that is already ongoing to be ready for the first collision. The statistics needed for each of the topics will be given with respect to the foreseen LHC startup scenario.Comment: Contribution for the 1st International Workshop on Soft Physics in ultrarelativistic Heavy Ion Collisions, Catania, Italy, 200

Overview of ALICE Results at Quark Matter 2014

The results released by the ALICE collaboration at Quark Matter 2014 address topics from identified-particle jet fragmentation functions in pp collisions, to the search for collective signatures in p-Pb collisions to precision measurements of jet quenching with D mesons in Pb-Pb collisions. This paper gives an overview of the contributions (31 parallel talks, 2 flash talks and 80 posters) by the ALICE collaboration at Quark Matter 2014.Comment: Proceedings for ALICE overview plenary at Quark Matter 201

Minimum-Bias and Early QCD Physics in ALICE

A Large Ion Collider Experiment (ALICE) is the dedicated heavy-ion experiment at the Large Hadron Collider (LHC). In addition to its heavy-ion physics program, it also has a rich proton-proton physics program benefiting from a detector with a low momentum cut-off (pT about 50 MeV/c) and a small material budget (about 11% of a radiation length until the outer wall of the main tracking detector, the Time-Projection Chamber). ALICE has excellent means of particle identification (PID) with methods ranging from specific energy loss and time of flight to transition and Cherenkov radiation. The good primary and secondary vertex resolution allows for measurements of strangeness and heavy flavor with low backgrounds. ALICE has taken proton-proton collision data at 0.9, 2.36, and 7 TeV. In this article results of the first minimum-bias and soft-QCD measurements are presented. Inclusive pseudorapidity, multiplicity, and transverse momentum distributions are discussed as well as distributions of identified particles including strange particles. Further, results on two-pion Bose-Einstein correlations and the antiproton-to-proton ratio in collisions at the LHC are shown.Comment: Proceedings of the Hadron Collider Physics Symposium 201

Event-Shape Engineering and Muon-Hadron Correlations with ALICE

Angular correlations of two and more particles are a sensitive probe of the initial state and the transport properties of the system produced in heavy-ion collisions. Two recent results of the ALICE collaboration are presented. Event-shape engineering, a novel method, is applied to Pb-Pb collisions which splits events within the same centrality interval into classes with different average flow. The results indicate an interplay between radial and elliptic flow likely related to the initial-state eccentricity. In pp and p-Pb collisions, recent results revealed intriguing long-range correlation structures reminiscent of features observed in heavy-ion collisions. The use of forward detectors allowed to show that long-range correlation structures persist also at large rapidities in p-Pb collisions.Comment: Proceedings of the European Physical Society Conference on High Energy Physics (EPS-HEP2015), Vienna, Austria, 22-29 July 201

Measurement of jet quenching with I_CP and I_AA,Pythia in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV with ALICE

This paper discusses the measurement of I_CP and I_AA,Pythia with ALICE (A Large Ion Collider Experiment). An away-side suppression is found expected from in-medium energy loss. Further, and unexpected, a near-side enhancement is seen which has not been reported by previous experiments at lower energies.Comment: Proceedings: Rencontres de Moriond QCD and High Energy Interactions 201

Phenomenology of soft QCD: the role of minimum-bias measurements

This chapter summarizes minimum-bias measurements at the Large Hadron Collider. In particular, the pseudorapidity density, the transverse-momentum spectra, the multiplicity distribution, the correlation of average transverse momentum and the multiplicity, and a measurement of minijets are presented. In addition to an overview of the results obtained to date at the LHC, the experimental challenges of defining particle and event sample and correcting to this sample are discussed.Comment: Book chapter 12 of Multiple Parton Interactions at the LHC; published in Adv. Ser. Direct. High Energy Phys., 29, 2018, doi: 10.1142/1064

In-Medium Energy Loss and Correlations in Pb-Pb Collisions at sqrt(s_NN) = 2.76 TeV

ALICE (A Large Ion Collider Experiment) is the dedicated heavy-ion experiment at the LHC. In fall 2010, Pb-Pb collisions were recorded at a center-of-mass energy of 2.76 TeV per nucleon pair, about 14 times higher than the energy achieved in A-A collisions at RHIC. The study of the produced hot and dense matter with an unprecedented energy density allows the characterization of the quark-gluon plasma, the deconfined state of quarks and gluons, predicted by QCD. The study of in-medium partonic energy loss allows insights into the density of the medium and the energy-loss mechanisms. This paper presents results based on inclusive spectra as well as two and more-particle correlations of charged particles. These are well suited to assess in-medium effects, ranging from the suppression of particles (R_AA) and away-side jets (I_AA) at high pT to long-range phenomena attributed to collective effects like the ridge at low pT. The analysis is discussed and the results are presented in the context of earlier RHIC measurements where appropriate.Comment: Proceedings for EPIC@LHC, Bari, Ital

Results from ALICE

ALICE, the dedicated heavy-ion experiment at the LHC, has also a rich pp program benefiting from its low material budget, low magnetic field, and its extensive particle identification capabilities. The talk presents recent measurements of relevance for cosmic-ray physics. In particular, ALICE measured the inelastic, single- and doublediffractive cross-sections in pp collisions at √s = 0.9, 2.76, and 7 TeV [1]. Further, the charged-particle pseudorapidity distribution (dNch/dη) in Pb-Pb collisions at √sNN = 2.76 TeV was measured over a large pseudorapidity range (-5.0 < η < 5.5) using collisions from displaced vertices [2]. Potential direct contributions of ALICE to cosmic-ray physics are also reviewed [3]

The Future of High-Energy Heavy-Ion Facilities

The plans within the next decade of the high-energy heavy-ion facilities RHIC at BNL and LHC at CERN are reviewed in detail, focusing on the physics programme for $\sqrt{s_{NN}} \ge$ 200 GeV. The expected data samples are presented, together with a discussion of the physics programme and reach. Selected performance studies are presented. An outlook is given on the plans with these and new facilities beyond 2030.Comment: Proceedings of plenary talk at the XXVIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2018