Suppression of Upsilon(1S) at forward rapidity in Pb-Pb collisions at root s(NN)=2.76 TeV

We report on the measurement of the inclusive Upsilon(1S) production in Pb-Pb collisions at root s(NN) = 2.76 TeV carried out at forward rapidity (2.5 < y < 4) and down to zero transverse momentum using its mu(+)mu(-) decay channel with the ALICE detector at the Large Hadron Collider. Astrong suppression of the inclusive Upsilon(1S) yield is observed with respect to pp collisions scaled by the number of independent nucleo-nnucleon collisions. The nuclear modification factor, for events in the 0-90% centrality range, amounts to 0.30 +/- 0.05(stat) +/- 0.04(syst). The observed Upsilon(1S) suppression tends to increase with the centrality of the collision and seems more pronounced than in corresponding mid-rapidity measurements. Our results are compared with model calculations, which are found to underestimate the measured suppression and fail to reproduce its rapidity dependence. (C) 2014 The Authors. Published by Elsevier B. V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). Funded by SCOAP(3)

Beauty production in pp collisions at s=2.76 TeV measured via semi-electronic decays

The ALICE Collaboration at the LHC reports measurement of the inclusive production cross section of electrons from semi-leptonic decays of beauty hadrons with rapidity |y|<0.8 and transverse momentum 1<pT<10 GeV/c, in pp collisions at s=2.76 TeV. Electrons not originating from semi-electronic decay of beauty hadrons are suppressed using the impact parameter of the corresponding tracks. The production cross section of beauty decay electrons is compared to the result obtained with an alternative method which uses the distribution of the azimuthal angle between heavy-flavour decay electrons and charged hadrons. Perturbative QCD predictions agree with the measured cross section within the experimental and theoretical uncertainties. The integrated visible cross section, σb→e=3.47±0.40(stat)-1.33+1.12(sys)±0.07(norm) μb, was extrapolated to full phase space using Fixed Order plus Next-to-Leading Log (FONLL) calculations to obtain the total bb production cross section, σbb=130±15.1(stat)-49.8+42.1(sys)-3.1+3.4(extr)±2.5(norm)±4.4(BR) μb

Precision measurement of the mass difference between light nuclei and anti-nuclei

The measurement of the mass di erences for systems bound by the strong force has reached a very high precision with protons and anti-protons1,2. The extension of such measure- ment from (anti-)baryons to (anti-)nuclei allows one to probe any di erence in the interactions between nucleons and anti- nucleons encoded in the (anti-)nuclei masses. This force is a remnant of the underlying strong interaction among quarks and gluons and can be described by e ective theories3, but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the di erence between the ratios ofthemassandchargeofdeuterons(d)andanti-deuterons(d ̄), and 3He and 3He nuclei carried out with the ALICE (A Large Ion Collider Experiment)4 detector in Pb–Pb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV. Our direct measurement of the mass-over-charge di erences confirms CPT invariance to an unprecedented precision in the sector of light nuclei5,6. This fundamental symmetry of nature, which exchanges particles with anti-particles, implies that all physics laws are the same under the simultaneous reversal of charge(s) (charge conjugation C), reflection of spatial coordinates (parity transformation P) and time inversion (T)