The global polarization of the Λ and Λ hyperons is measured for Pb-Pb collisions at sNN=2.76 and 5.02 TeV recorded with the ALICE at the Large Hadron Collider (LHC). The results are reported ...differentially as a function of collision centrality and hyperon's transverse momentum (pT) for the range of centrality 5-50%, 0.5<pT<5 GeV/c, and rapidity |y|<0.5. The hyperon global polarization averaged for Pb-Pb collisions at sNN=2.76 and 5.02 TeV is found to be consistent with zero, (PH)(%)≈0.01±0.06(stat.)±0.03(syst.) in the collision centrality range 15-50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at the Relativistic Heavy Ion Collider, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%.
Cross sections for the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Pb-Pb collisions at sNN−−−√ = 5.02 TeV are reported. The measurements, which rely on the π+π− decay channel, ...are presented in three regions of rapidity covering the range |y| < 0.8. For each rapidity interval, cross sections are shown for different nuclear-breakup classes defined according to the presence of neutrons measured in the zero-degree calorimeters. The results are compared with predictions based on different models of nuclear shadowing. Finally, the observation of a coherently produced resonance-like structure with a mass around 1.7 GeV/c2 and a width of about 140 MeV/c2 is reported and compared with similar observations from other experiments.
How to extract physics from nu (dyn) Christiansen, Peter; Haslum, Eva; Stenlund, Evert
Physics of atomic nuclei,
2012, Letnik:
75, Številka:
6
Journal Article
Recenzirano
In this paper we summarize the properties of nu (dyn) and discuss briefly how the results can be interpreted in terms of a simple pair-production model. The ideas are then illustrated in detail with ...a PYTHIA simulation study of forward-backward correlations in pp collisions.
The measurement of single leptons from the semi-leptonic decay of heavy-flavor hadrons has long been a means for studying heavy-quark production. PHENIX has measured single muons in pp collisions at ...forward rapidity and single electrons in both pp and AuAu collisions at mid-rapidity at . The most recent PHENIX single lepton results are presented in the context of state-of-the-art pQCD calculations. An updated azimuthal anisotropy, v2(pT), measurement for heavy-flavor single electrons in AuAu collisions is also presented.
The 'shoulder' and the 'ridge' in PHENIX McCumber, M P
Journal of physics. G, Nuclear and particle physics,
10/2008, Letnik:
35, Številka:
10
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Comparison of two-particle correlations in heavy-ion collisions with measurements in proton collisions shows strong modification of the correlation shape and particle yields. Two new structures are ...created; both extended in Δη, one centered at Δ = 0 ('ridge') and the other occurring at Δ π ± 1.1 ('shoulder'). In these proceedings, we describe the measurements of these structures that show consistency with a scenario of parton–medium interaction and response. We discuss a new analysis with improved resolution in selections on the angle of trigger particles relative to the reaction plane. New measurements of the centrality and pT dependences of the structures raise the possibility that the same production mechanism may give rise to both phenomena.
PDF
