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European Particle physics Latin American NETwork

Final Report Summary - EPLANET (European Particle physics Latin American NETwork)

1. Publishable Summary

Objective of EPLANET (European Particle physics Latin American NETwork) is the formation of the scientific personnel of Beneficiary and Partner Institutions by participation in world class experiments at two of the most advanced research infrastructure in basic physics: CERN, for Particle Physics at the Large Hadron Collider (LHC), located in Geneva, Switzerland, and the Pierre Auger Observatory (PAO), for the observation of Ultra-High Energy Cosmic Rays, located in Malargue, Mendoza, Argentina. For the five years of the project, and for many years to come, these facilities have represented European flagships of fundamental research.
Leadership in fundamental science will generate breakthrough technologies with the potential to contribute to future competitiveness of European Industry in key areas like healthcare, big data, electronics, to name few. Training young generations in these frontier facilities guarantees the quality of the future researchers. The new technologies developed for research will open solid ground for young innovative companies and entrepreneurs.
The years of the project, 2011 to 2016, have witnessed important developments coming from CERN and PAO, with an important participation of LA and EU researchers supported by EPLANET, explicitly recognised in the discovery papers.
In 2011, the Large Hadron Collider went into operation and data collection was started by four large experiments: ALICE, ATLAS, CMS, LHCb. A first run in 2011-2012, Run1, was followed by a long shutdown, 2013 to 2015, after which operations at LHC have been resumed, with the beam energy increased by about a factor of two and the prospect of even higher luminosities. During the same years, the PAO facility has been consolidated and went into extensive data taking. The data collection was followed by planning and execution of important, second generation, upgrades.
The discovery of the Higgs boson with mass around 125 GeV was reported by ATLAS and CMS during Run1(G. Aad et al. [ATLAS Collaboration], Phys. Lett. B 716 (2012) 1; V. Khachatryan et al.[CMS Collaboration], Eur.Phys.J. C75 (2015)212). The discovery led to the award of the 2013 Nobel Prize in Physics to Francois Englert and Peter Higgs, who had predicted the particle’s existence back in 1964.
In 2013-2015, the LHC collaborations have produced important results in particle and high energy nuclear physics. Data on lead-lead and proton-lead collisions by ALICE (B. Abelev et al. [ALICE Collaboration],Phys. Lett. B 719 (2013) 29) have produced remarkable progress on the understanding of a new phase of matter, with liberated quark and gluon constituents. High precision studies of the new 125 GeV particle have confirmed its compatibility with the Standard Model Higgs boson (ATLAS and CMS). Data on the rare decays of mesons containing a beauty quark have strongly confirmed the validity of the Standard Model (CMS Collaboration & LHCb Collaboration, Nature 522, (2015) 68). The observation by LHCb of a new exotic baryon made by five quarks has opened up new perspectives to the understanding of the basic strong interactions (R. Aaij et al. [LHCb Collaboration], Phys. Rev. Lett. 115 (2015) 072001).
With Run2, the LHC has initiated the exploration of an entirely new frontier at high energy. Lower limits to the mass of hypothetical new particles associated to SuperSymmetry have been produced, in the order of 700 GeV (stop quark) and 1200 GeV (gluino).
No positive new signal of new physics has emerged from the data of Run1, or from the preliminary data from Run2. On the positive side, an unprecedented confirmation of the Standard Theory has emerged from the complex of the Electroweak data, including mass and decay modes of the Higgs boson.
The Pierre Auger Observatory (PAO) at Malargue, Argentina, operated by a large international collaboration with important European participation, has explored the Ultra High Energy frontier of cosmic rays and possibly the interactions of high energy neutrinos in the atmosphere.
Two important results have been obtained with the PAO during the years of EPLANET, with a significant contribution from EU researchers. The first is the unequivocal demonstration of the high energy cutoff in the spectrum of Ultra High Energy cosmic rays, predicted long ago by Greisen-Zatsepin and Kuzmin and presumably due to the interaction of cosmic protons and nuclei with the photons of the Cosmic Microwave background (A. Aab et al. [Pierre Auger Collaboration], JCAP 1508 (2015) 049). The second is a tantalising, albeit preliminary, evidence of a clustering of Ultra High Energy cosmic rays in the directions of Ursa Maior and Centaurus A (A. Aab et al. [Pierre Auger Collaboration], Astrophys. J. 789 (2014)160). The measurements of the Auger collaboration in these two areas have opened a new era in Cosmic Ray physics.
EPLANET is participated by internationally recognised Institutions, with proven experience and know-how. Beneficiary Institutions in Europe include CERN as well as main Universities and Research Institutions for Particle and Cosmic Ray physics in France, Italy, Spain and Portugal. Partner Institutions from Latin America include main Universities of Argentina, Brazil, Chile and Mexico.
Luciano Maiani, former Director General of CERN and Emeritus at Università di Roma La Sapienza, Italy, has coordinated EPLANET. Deputy coordinator was Veronica Riquer PhD, Università di Roma La Sapienza and ICTP, Trieste (see
The program has supported visits from Argentina, Brazil, Chile and Mexico to CERN and other European Institutions and from European countries to LA, notably to PAO, with short exchanges (1-2 months) for senior and longer exchanges (2-12 months) for junior investigators, for a total close to 1500 months.
EPLANET has successfully fostered the development of the community in Latin America and contributed to develop the educational, technological and industrial potential of HEP. The detachment of European ER and ESR scientists in Latin America has strengthened research partnership. In brief, EPLANET has made a substantial step towards a sustainable collaboration between Europe and Latin America in HEP and the associated technologies, while participating to fundamental discoveries.

The EPLANET Logo, Fig. 1, and a few pictures are provided, for illustration.
The technological complexity of the ATLAS and CMS detectors is well illustrated by Figs. 2-3. Mastering such complexity and identifying interesting events in the enormous flux of data originating from the particle collisions recorded by them requires sophisticated technologies that will find many applications in everyday life. Fig. 4 shows the peaks in the spectrum of two photons observed by ATLAS and by CMS, with 5 standard deviations significance. These results provided the basis for the announcement of the discovery of the Higgs boson by the two collaborations, on July 4th, 2012. Francois Englert and Peter Higgs, the future Nobel Prizes who had predicted in 1964 the existence of this particle, were present at the announcement, Fig. 5.
A selection of images of the Pierre Auger Observatory (Fig. 6) shows the fascination of the Malargue site, in the Pampa Amarilla, dominated by the Aconcagua massif. The complex of 1600 detectors form an array covering a total area of 3000 km2, which allows to detect the large shower of particle produced by the most energetic cosmic rays observed on Earth.
The important results obtained at the PAO are illustrated in Figs. 7-8. Fig. 7 shows the data on the spectrum of Ultra High Energy cosmic rays measured at PAO, showing the cosmic ray GKZ cutoff at high energy, clearly revealed, if compared with the spectra obtained previously at other installations. Fig. 8 shows the possible clustering of UHE cosmic rays, in the directions of Ursa Maior and Centaurus A.
Fig. 9 shows a tutorial class on Machine Learning with hands-on exercises based on the ROOT platform used by CERN experiments. Courses were held at the Universidad do Estado de Rio de Janeiro, UERJ, November 2015, by CERN staff.