Production of multi-strange baryons in 7 TeV proton-proton collisions with ALICE

In the perspective of comparisons between proton-proton and heavy-ion physics, understanding the production mechanisms (soft and hard) in pp that lead to strange particles is of importance. Measurements of charged multi-strange (anti-)baryons (Omega and Xi) are presented for pp collisions at sqrt(s) = 7 TeV. This report is based on results obtained by ALICE (A Large Ion Collider Experiment) from the 2010 data-taking. Taking advantage of the characteristic cascade-decay topology, the identification of Xi-, anti-Xi+, Omega- and anti-Omega+ can be performed, over a wide range of momenta (e.g. from 0.6 to 8.5 GeV/c for Xi-, with the present statistics analysed). The production at central rapidity (|y| < 0.5) as a function of transverse momentum, dN/dptdy, is presented. These results are compared to PYTHIA Perugia 2011 predictions.Comment: 6 pages, 3 figures, 1 table. Strangeness In Quark Matter (SQM 2011), 18-24 Sept. 2011, Krakow. To be published in Acta Physica Polonica B (APPB

Revelation and Phenomenal Relations

Revelation, or the view that the essence of phenomenal properties is presented to us, is as intuitively attractive as it is controversial. It is notably at the core of defences of anti-physicalism. I propose in this paper a new argument against Revelation. It is usually accepted that low-level sensory phenomenal properties, like phenomenal red, loudness or brightness, stand in relation of similarity and quantity. Furthermore, these similarity and quantitative relations are taken to be internal, that is, to be fixed by what their relata are. I argue that, under some plausible additional premises, no account of what grounds these relations in the essence of their relata is consistent with Revelation, at least if we take common phenomenological descriptions for granted. As a result, the plausibility of Revelation is undermined. One might however resist this conclusion by weakening the epistemic relation postulated between subjects and their phenomenal properties

Unitary and non-unitary transitions around a cosmological bounce

In this work, we investigate the notion of time and unitarity in the vicinity of a bounce in quantum cosmology, that is, a turning point for the scale factor. Because WKB methods drastically fail near a turning point, the scale factor cannot play the role of time in such scenarios. We overcome this difficulty by studying the dynamics of matter transitions when using its conjugate momentum as a time. We find precise conditions so as to recover unitarity, and hence, a consistent notion of probability. We then compute transitions in a concrete example, extract the specific feature of a bounce and argue about the necessity of the conjugate momentum representation to go beyond the background field approximation. Our analysis is also equally relevant for a closed Universe undergoing a recollapsing phase.Comment: 25 pages, 1 figure, published versio

Complexity of Grammar Induction for Quantum Types

Most categorical models of meaning use a functor from the syntactic category to the semantic category. When semantic information is available, the problem of grammar induction can therefore be defined as finding preimages of the semantic types under this forgetful functor, lifting the information flow from the semantic level to a valid reduction at the syntactic level. We study the complexity of grammar induction, and show that for a variety of type systems, including pivotal and compact closed categories, the grammar induction problem is NP-complete. Our approach could be extended to linguistic type systems such as autonomous or bi-closed categories.Comment: In Proceedings QPL 2014, arXiv:1412.810

Measurements of inclusive J/psi production in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV with the ALICE experiment

Charmonium is a prominent probe of the Quark-Gluon Plasma (QGP), expected to be formed in ultrarelativistic heavy-ion (A-A) collisions. It has been predicted that the J/psi(c-cbar) particle is dissolved in the deconfined medium created in A-A systems. However this suppression can be counterbalanced via regeneration of the charm/anti-charm bound state in QGP or via statistical production at the phase boundary. At LHC energies, the latter mechanisms are expected to play a more important role, due to a charm production cross section significantly larger than at lower energies. Measurements obtained by the ALICE experiment for inclusive J/psi production are shown, making use of Pb-Pb data at sqrt(s_NN) = 2.76 TeV, collected in 2010 and 2011. In particular, the focus is given on the nuclear modification factor, R_AA, derived for forward (2.5 < y < 4) and mid rapidities (|y| < 0.9), both down to zero transverse momentum (pT). The centrality, y and pT dependences of R_AA are presented and discussed in the context of theoretical models, together with PHENIX and CMS results.Comment: 8 pages, 7 figures. To be published in PoS. Proceedings of the Xth QCHS conference (Quark Confinement and the Hadron Spectrum), 2012, 8-12 October 2012, Munich. See corresponding presentation under TUM indico : http://intern.universe-cluster.de/indico/contributionDisplay.py?contribId=246&sessionId=36&confId=229