Measurement of jet pTp_{\mathrm{T}} spectra in Pb-Pb collisions at sNN=2.76 TeV\sqrt{s_{\mathrm{NN}}}=2.76~\mathrm{TeV} with the ALICE detector at the LHC

Reconstruction of jets in high-energy heavy-ion collisions is challenging due to the large and fluctuating background coming from the underlying event. We report results on full jet reconstruction, obtained from data collected in 2011 by the ALICE detector at LHC for Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76~\mathrm{TeV}$. The analysis makes use of the tracking system and the electromagnetic calorimeter. Signal jets, which come from hard scattered partons, are reconstructed using the anti-$k_{\mathrm{T}}$ jet finder algorithm. The average background is subtracted on a jet-by-jet basis to reduce the contribution to the jet reconstructed energy coming from the underlying event. The jet spectrum is corrected to account for fluctuations in the background momentum density and detector effects through unfolding.Comment: 4 Pages, Hot Quarks 2012 Proceeding

New results on jets and heavy flavor in heavy-ion collisions with ALICE

The large statistics accumulated during the LHC Run-1 and Run-2 have provided the unique opportunity to study the properties of the Quark-Gluon Plasma using rare hard probes. The ALICE Collaboration has presented new results on the jet shape observables in p--Pb and Pb--Pb collision. Using data from Run-2, the elliptic flow of open and hidden charm mesons have been measured with much better precision, confirming that charm quarks participate in the collective dynamic expansion with the medium. In p--Pb collisions the absence of jet quenching correlated with high event activity has been confirmed by a self-normalized semi-inclusive hadron+jet measurement.Comment: 8 pages, 5 figures, Proceedings of the Fifth Annual Conference of Large Hadron Collider Physics, May 15-20, 2017, Shanghai, Chin

Measurement of jet pTp_{\rm T} spectra and RAAR_{\rm AA} in pp and Pb-Pb collisions at sNN\sqrt{s_{\rm NN}} = 2.76 TeV with the ALICE detector

Hard-scattered partons provide an ideal probe for the study of the Quark-Gluon Plasma because they are produced prior to the formation of the QCD medium in heavy-ion collisions. Jet production is therefore susceptible to modifications induced by the presence of the medium ("jet quenching"). Both RHIC and LHC experiments have provided compelling evidence of jet quenching. Jets are reconstructed in ALICE utilizing the central tracking system for the charged constituents and the Electromagnetic Calorimeter for the neutral constituents. Jet spectra are reported for central (0-10%) and semi-central (10-30%) Pb-Pb events at $\sqrt{s_{\rm NN}}=2.76$ TeV. The nuclear modification factor, determined using a pp baseline measured at the same collisional energy, shows a strong suppression of jet production in central Pb-Pb collisions with the expected centrality ordering. Observations are in qualitative agreement with medium-induced energy loss models. Furthermore, indication of a path-length dependence of jet suppression is inferred from measurements of the yields relative to the orientation of the event plane.Comment: 5 pages, 3 figures, Proceedings of the XXIV International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions Quark Matter 201

Educational measurements of cosmic rays using small scintillation detectors

An experimental set-up, based on a small plastic scintillator tile with an embedded wavelength shifter fibre and APD sensors has been used to perform educational cosmic rays measurements. Readout electronics has made advantage of Quarknet card timing capabilities. The time-over-threshold technique has been exploited as a simple method to extract information about the signal amplitude, in order to estimate the energy deposit in the detector. Coincidence measurements have been performed both in two-fold and three-fold configurations, unveiling the possibility to reconstruct the shower axis using the triangulation method

New Probes of Cosmic Microwave Background Large-Scale Anomalies

Fifty years of Cosmic Microwave Background (CMB) data played a crucial role in constraining the parameters of the ΛCDM model, where Dark Energy, Dark Matter, and Inflation are the three most important pillars not yet understood. Inflation prescribes an isotropic universe on large scales, and it generates spatially-correlated density fluctuations over the whole Hubble volume. CMB temperature fluctuations on scales bigger than a degree in the sky, affected by modes on super-horizon scale at the time of recombination, are a clean snapshot of the universe after inflation. In addition, the accelerated expansion of the universe, driven by Dark Energy, leaves a hardly detectable imprint in the large-scale temperature sky at late times. Such fundamental predictions have been tested with current CMB data and found to be in tension with what we expect from our simple ΛCDM model. Is this tension just a random fluke or a fundamental issue with the present model? In this thesis, we present a new framework to probe the lack of large-scale correlations in the temperature sky using CMB polarization data. Our analysis shows that if a suppression in the CMB polarization correlations is detected, it will provide compelling evidence for new physics on super-horizon scale. To further analyze the statistical properties of the CMB temperature sky, we constrain the degree of statistical anisotropy of the CMB in the context of the observed large-scale dipole power asymmetry. We find evidence for a scale-dependent dipolar modulation at 2.5σ. To isolate late-time signals from the primordial ones, we test the anomalously high Integrated Sachs-Wolfe effect signal generated by superstructures in the universe. We find that the detected signal is in tension with the expectations from ΛCDM at the 2.5σ level, which is somewhat smaller than what has been previously argued. To conclude, we describe the current status of CMB observations on small scales, highlighting the tensions between Planck, WMAP, and SPT temperature data and how the upcoming data release of the ACTpol experiment will contribute to this matter. We provide a description of the current status of the data-analysis pipeline and discuss its ability to recover large-scale modes

Differential studies of inclusive J/ψ and ψ(2S) production at forward rapidity in Pb-Pb collisions at √sNN = 2.76 TeV

The production of J/psi and psi (2S) was studied with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity (2.5 < y < 4) down to zero transverse momentum (p(T)) in the dimuon decay channel. Inclusive J/psi yields were extracted in different centrality classes and the centrality dependence of the average p(T) is presented. The J/psi suppression, quantified with the nuclear modification factor (R-AA), was measured as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/psi production is the result of an interplay between color screening and recombination mechanisms in a deconfined partonic medium, or at its hadronization. Results on the psi(2S) suppression are provided via the ratio of psi(2S) over J/psi measured in pp and Pb-Pb collisions