Portuguese Laboratory of Instrumentation and Experimental Particle Physics

Lisbon, Portugal

Portuguese Laboratory of Instrumentation and Experimental Particle Physics

Lisbon, Portugal
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Maio A.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics | Maio A.,University of Lisbon
Journal of Physics: Conference Series | Year: 2015

The SNO+ experiment is adapting the Sudbury Neutrino Observatory (SNO) detector, in order to use isotope-loaded liquid scintillator as the active medium. SNO+ has multiple scientific goals, the main one being the search for neutrinoless double beta decay, the most promising signature for the possible Majorana character of neutrinos and for the absolute neutrino mass. Measurements of neutrinos from the Sun, the Earth, Supernovae and nuclear reactors are additional goals of the experiment. The detector consists of a 12m diameter spherical vessel, filled with 780 tonnes of Tellurium-loaded liquid scintillator, and surrounded by about 9500 PMTs. It is shielded by a large volume of ultra-pure water and the underground location at SNOLAB, Canada. This talk will review the Physics goals and current status of SNO+. © 2014 Published under licence by IOP Publishing Ltd.


Faccioli P.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics | Lourenco C.,CERN | Seixas J.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics | Seixas J.,University of Lisbon | Wohri H.K.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
European Physical Journal C | Year: 2010

We highlight issues which are often underestimated in the experimental analyses on quarkonium polarization: the relation between the parameters of the angular distributions and the angular momentum composition of the quarkonium, the importance of the choice of the reference frame, the interplay between observed decay and production kinematics, and the consequent influence of the experimental acceptance on the comparison between experimental measurements and theoretical calculations. Given the puzzles raised by the available experimental results, new measurements must provide more detailed information, such that physical conclusions can be derived without relying on model-dependent assumptions. We describe a frame-invariant formalism which minimizes the dependence of the measurements on the experimental acceptance, facilitates the comparison with theoretical calculations, and probes systematic effects due to experimental biases. This formalism is a direct and generic consequence of the rotational invariance of the dilepton decay distribution and is independent of any assumptions specific to particular models of quarkonium production. The use of this improved approach, which exploits the intrinsic multidimensionality of the problem, will significantly contribute to a faster progress in our understanding of quarkonium production, especially if adopted as a common analysis framework by the LHC experiments, which will soon perform analyses of quarkonium polarization in proton-proton collisions. © 2010 The Author(s).


Faccioli P.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics | Faccioli P.,University of Lisbon | Knunz V.,Institute of High Energy Physics HEPHY | Lourenco C.,CERN | And 3 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Polarization measurements are usually considered as the most difficult challenge for the QCD description of quarkonium production. In fact, global data fits for the determination of the non-perturbative parameters of bound-state formation traditionally exclude polarization observables and use them as a posteriori verifications of the predictions, with perplexing results. With a change of perspective, we move polarization data to the centre of the study, advocating that they actually provide the strongest fundamental indications about the production mechanisms, even before we explicitly consider perturbative calculations.Considering ψ(2. S) and Υ{hooked}(3. S) measurements from LHC experiments and state-of-the-art next-to-leading order cross sections for the short-distance production of heavy quark-antiquark pairs of relevant colour and angular momentum configurations, we perform a search for a kinematic domain where quarkonium polarizations can be correctly reproduced together with the respective cross sections, by systematically scanning the phase space and accurately treating the experimental uncertainties. This strategy provides a straightforward solution to the "quarkonium polarization puzzle" and reassuring signs that the factorization of short- and long-distance effects works, at least in the high-transverse-momentum region, least affected by limitations in the current fixed-order calculations. The results expose unexpected hierarchies in the phenomenological long-distance parameters that open new paths towards the understanding of bound-state formation in QCD. © 2014 The Authors.


Quaresma M.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
EPJ Web of Conferences | Year: 2014

The COMPASS experiment at CERN has been playing an important role in the studies of the spin content of the nucleon. The Semi-Inclusive Deep Inelastic Scattering (SIDIS) process gives access to the transverse momentum dependent parton distribution functions (TMDs) by the measurement of azimuthal asymmetries that have been studied in COMPASS and published in recent years. TMDs are also accessible by the transversely polarised Drell-Yan (DY) process which will be measured in COMPASS. This will be the first ever polarised DY measurement. The valence quarks region will be dominant due to the use of a negative pion beam at 190 GeV/c momentum impinging on a transversely polarised ammonia target. The QCD prediction that Sivers TMD change sign when accessed by SIDIS or by DY will be checked by the COMPASS measurement. The data taking is scheduled to start in the fall of this year. After one year of data collection, a statistical error below 2% in the azimuthal asymmetry related to the u quark Sivers function is expected. Details of the final experimental setup will be presented. © Owned by the authors, published by EDP Sciences, 2014.


Silva L.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
Few-Body Systems | Year: 2013

Over the last decade the COMPASS experiment has successfully obtained precise results on nucleon structure and hadron spectroscopy, with statistical errors much lower than previously reported. Recently, the new COMPASS-II program, focused on the study of a more complete nucleon description, was approved by CERN. The goal of the program is to access the nucleon structure beyond the collinear approxi-mation, including the quark intrinsic transverse momentum distributions, which are described by the Transverse Momentum Dependent (TMD) Parton Distribution Functions (PDFs) and by Generalised Parton Distributions (GPDs). The COMPASS collaboration proposes to measure the TMD PDFs, for the first time, via the polarised Drell-Yan process. The results will be complementary to those already obtained in polarised Semi-Inclusive Deep Inelastic Scattering (SIDIS). The GPDs can be accessed using deeply virtual Compton scattering and hard exclusive meson production using an unpolarised hydrogen target in a kinematic region not yet covered by any existing experiment. Also unpolarised SIDIS will be studied, by improving the knowledge of the strange quark PDF and obtaining the kaon fragmentation functions. Another topic covered in this COMPASS-II program is the measurement of the pion and kaon polarisabilities using the Primakoff reaction, which corresponds to a test of the chiral perturbative theory. © 2013 Springer-Verlag Wien.


Quaresma M.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
Acta Physica Polonica B, Proceedings Supplement | Year: 2012

The Parton Distribution Functions (PDFs) and the spin structure of the nucleon are important topics studied by the COMPASS experiment. The Drell-Yan (DY) process will be used in the future COMPASS-II measurements to access the Transverse Momentum Dependent PDFs (TMD PDFs). Studying the angular distributions of dimuons from the DY reactions with a negative pion beam with 190 GeV/c momentum and a transversely polarised proton target, we will be able to extract the azimuthal spin asymmetries and to access the various TMD PDFs, such as Sivers and Boer-Mulders functions. The start of the COMPASS DY experiment is scheduled for 2014. Three beam tests have been already performed, one of them in 2009 using a prototype hadron absorber downstream of the target, to understand the background reduction factors and the spectrometer response, and also to verify our results from Monte Carlo simulations. COMPASS aims at performing the first DY experiment with a transversely polarised target.


Quintans C.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
Journal of Physics: Conference Series | Year: 2011

The COMPASS experiment at CERN studies the spin structure of the nucleon, using its unique polarized target in both longitudinal and transverse polarization modes. The future Drell-Yan measurement by the COMPASS collaboration proposes to access the transverse momentum dependent parton distribution functions, namely Sivers and Boer-Mulders functions. The Drell-Yan process with unpolarized and with transversely polarized target is a very promising tool for this purpose, complementary to the semi-inclusive deep inelastic scattering measurements available from COMPASS, HERMES and JLab experiments. Also interesting related studies like the J/ψ-Drell-Yan duality are proposed. The physics case, as well as the most important technical aspects of this project are presented.


Seabra L.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2015

ALFA (Absolute Luminosity For ATLAS) is one of the sub-detectors of ATLAS (A Toroidal LHC Apparatus). The ALFA system is composed by four stations installed in the LHC tunnel 240 m away from the ATLAS interaction point. Each station has a vacuum and ventilation system, movement control and all the required electronics for signal processing. The Detector Control System (DCS) provides control and monitoring of several components and ensures the safe operation of the detector contributing to good Data Quality. This paper describes the ALFA DCS system including a detector overview, operation aspects and hardware control through a SCADA system, WinCC OA. © 2015 IEEE.


Silva L.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
EPJ Web of Conferences | Year: 2015

The COMPASS experiment, at CERN SPS, has been compiling for more than a decade successful and precise results on nucleon structure and hadron spectroscopy, leading to statistical errors much smaller than previously measured. The new COMPASS spin physics program, starting this year, aims to a rather complete nucleon structure description; this new representation goes beyond the collinear approximation by including the quark intrinsic transverse momentum distributions. The theoretical framework, for this new picture of the nucleon, is given by the Transverse Momentum Dependent distributions (TMDs) and by the Generalised Parton Distributions (GPDs). The TMDs, in particular Sivers, Boer-Mulders, pretzelosity and transversity functions will be obtained through the polarised Drell-Yan process, for the first time. The results will be complementary to those already obtained via polarised Semi-Inclusive Deep Inelastic Scattering (SIDIS). Also unpolarised SIDIS will be studied, allowing the knowledge improvement of the strange quark PDF and the access to the kaon fragmentation functions (FFs). Deeply Virtual Compton Scattering (DVCS) off an unpolarised hydrogen target will be used to study the GPDs, in a kinematic region not yet covered by any existing experiment. © Owned by the authors, published by EDP Sciences, 2015.


Maneira J.,Portuguese Laboratory of Instrumentation and Experimental Particle Physics
Nuclear Physics B - Proceedings Supplements | Year: 2011

SNO+ is a new multi-purpose Neutrino Physics experiment, presently in construction at SNOLAB, succeeding to the Sudbury Neutrino Observatory by replacing heavy water with liquid scintillator. In the Neodymium-loading phase, SNO+ will search for the double-beta decay of 150Nd. With pure scintillator, SNO+ will measure several components of the solar neutrino spectrum, with special relevance for the pep and CNO neutrinos that have much less cosmogenic background at the SNOLAB depth. In addition, interesting measurements can be carried out with antineutrinos from nuclear reactors and the Earth's natural radioactivity. This paper summarizes the Physics goals of SNO+, as well as the main ongoing detector developments. © 2011 Elsevier B.V.

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