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ALICE results on vector meson photoproduction in ultra-peripheral p-Pb and Pb-Pb collisions
Lead nuclei, accelerated at the LHC, are sources of strong electromagnetic
fields that can be used to measure photon-induced interactions in a new
kinematic regime. These interactions can be studied in ultra-peripheral p-Pb
and Pb-Pb collisions where impact parameters are larger than the sum of the
nuclear radii and hadronic interactions are strongly suppressed. Heavy
quarkonium photoproduction is of particular interest since it is sensitive to
the gluon distribution in the target. The ALICE Collaboration has studied J/psi
and psi(2S) photoproduction in ultra-peripheral Pb-Pb collisions and exclusive
J/psi photoproduction off protons in ultra-peripheral p-Pb collisions at the
LHC. Implications for the study of gluon density distributions and nuclear
gluon shadowing are discussed. Recent ALICE results on rho photoproduction are
also presented.Comment: 4 pages, 2 figures, proceedings of the International Conference on
Particles and Nuclei (PANIC 2014), Hamburg, Germany, August 25-29, 201
Overview of ALICE results
Selected ALICE results on the global event properties, particle spectra,
azimuthal anisotropy, heavy flavour and quarkonium production in Pb-Pb
collisions at sqrt(s_NN) = 2.76 TeV are presented. First results on p-Pb
collisions at sqrt(s_NN) = 5.02 TeV are briefly reviewed.Comment: 5 pages, proceedings of the conference "New Trends in High Energy
Physics", Alushta, Ukraine, September 23-29, 201
Photoproduction of heavy vector mesons in ultra-peripheral Pb-Pb collisions
Ultra-peripheral Pb-Pb collisions, in which the two nuclei pass close to each
other, but at an impact parameter greater than the sum of their radii, provide
information about the initial state of nuclei. In particular, heavy vector
meson production, where the particle mass sets a hard scale, proceeds in such
collisions by photon-gluon interactions, and gives access to nuclear PDFs. The
ALICE collaboration has published measurements of J/psi and psi(2S)
photoproduction in ultra-peripheral collisions in LHC Run 1 at forward (J/psi)
and mid-rapidity, and has obtained a substantially larger data set in 2015 from
LHC Run 2, allowing much more detailed studies of the production mechanism to
be performed. In particular, the increased energy and more detailed
measurements in the forward region in Run 2 give access to significantly lower
values of Bjorken-x than in previous studies. In this talk, the latest
available results from Run 2 will be given.Comment: 4 pages, 5 figures, XXVIth International Conference on
Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017
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