A conferência de física de altas energias da Sociedade Europeia de Física terminou na semana passada em Gent, na Bélgica, e o LIP esteve bem representado — com comunicações nas sessões sobre Física do Higgs, Física dos Iões Pesados e ainda Outreach, Educação e Diversidade. Investigadores do LIP contribuíram ainda na moderação de sessões e nos comités internacionais que ajudaram a preparar o encontro. Na foto, vemos alguns dos investigadores do LIP que estiveram presentes em Ghent.

A EPS-HEP, organizada de dois em dois anos desde 1971 pela Divisão de Física de Partículas e de Altas energias da Sociedade Europeia de Física, é uma das principais conferências mundiais nesta área. É sempre uma conferência cheia de novos resultados e oportunidades de discussão, cobrindo de forma exaustivas a física de partículas e astropartículas.

Abaixo, citamos alguns destaques da conferência, baseados na excelente newsletter publicada todos os dias durante a conferência, a Standard Waffle:

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An impressive set of new results of the ATLAS and CMS Collaborations using the full Run II data sets were presented. The emphasis was naturally put on the most recent Higgs measurements, showing the enormous progress made by the two experiments since the Higgs discovery. Promising results on the couplings of the Higgs boson to quarks and leptons of the second generation are now available, even if more data will be needed to reach the sensitivity to test the SM couplings. Additionally, many other important results on a broad range of physics topics have been highlighted, including electroweak measurements involving vector bosons and the top quark, and searches for supersymmetry and exotica. It is also interesting to note that both experiments are now exploiting innovative data analysis methods and techniques, including scouting, data parking and machine learning, to maximize their discovery potential. Precision calculations in the SM are also becoming increasingly sophisticated, with conceptual and technical solutions drawing from recent developments in formal theory and pure mathematics. BSM physics is broadening its theoretical viewpoints to embrace a multitude of possible scenarios, opening up new perspectives and observables.

Concerning flavour physics, the latest results from the LHCb experiment were presented, including CP violation results, tests of lepton universality, and discovery of several new states. Also ATLAS and CMS join LHCb, e.g. regarding rare B decays and tests of lepton universality. An interesting pattern of flavour anomalies still persists! Attention also focused on the e + e - results from BESIII and BaBar/Belle, along with first results from Belle-II. The theoretical view focused on flavour physics as a new physics probe. We now await more LHC Run2 results, the start of the upgraded LHCb detector and key physics results from Belle-II.

Turning to astroparticle physics, the results from Ligo-Virgo were reviewed, highlighting the birth of multimessenger astronomy. Neutrino astronomy with IceCube saw a neutrino measurement in conjunction with gamma rays in the MAGIC detector and 18 astronomical observatories, giving first compelling evidence for a non-stellar neutrino source: a Blazar. This strongly motivates the need for next generation detectors in this field. To conclude, the positron and antiproton spectra from AMS-02 were highlighted, along with measurements of UHECR and insights in their composition.

The neutrino overview started from the current anomaly status. Highlights were the comparisons of Double Chooz, RENO and Daya Bay, the rich programme of very short baseline experiments, and the next frontier experiment, JUNO. On neutrinos from particle beams, current results from T2K and NOvA were presented, with a focus on leptonic CP violation, MicroBooNE and T2K results on neutrino-nucleon interactions, and future sensitivities of DUNE and HK. Sterile neutrinos and other BSM physics at current and future experiments were presented, highlighting the importance of the CERN neutrino platform. From a theoretical perspective, the determination of a New Standard Model explaining neutrino masses is the ultimate goal. We need to understand the origin of neutrino masses and their properties, by means of a rich experimental programme.

Dark matter searches were reviewed from the complementary direct and indirect detection, and accelerator perspectives. Direct detection approaches the neutrino floor, prompting interesting proposals with directional sensitivity. A revived fixed target program aims at exploring sub-GeV dark matter. The status on searches for axions was given, with light-shining-through-wall experiments like ALPS-II, and tunable haloscopes like ADMX producing new results. For solar axions, we look forward to BabyIAXO. Overall, a large fraction of parameter space is in reach. From the theory perspective, the concept of ultra-light fuzzy dark matter was highlighted, already constrained by EHT’s recent observation of the M87 black hole.

The last day of the session started with heavy ion physics, studying the high-T state of the strong interaction, the QGP. Highlights from ALICE included new results on nuclear modification and suppression of heavy D mesons, and determinations of the heavy quark diffusion and scattering transport coefficient in the QGP. A new Upsilon result shows a surprisingly small azimuthal anisotropy, which indicates quarkonia in the QGP to behave differently from single heavy quarks. A new ML technique to subtract uncorrelated background in large cones was also presented. Next, the emergence of QGP phenomena in small systems such as pp and pPb collisions was discussed, in particular the onset of collective effects and how theoretical modelling allows to learn about the underlying QCD. Among the recent insights are studies in archived ee collision data and in γ +A collisions at the LHC. The experimental overview focused on high-momentum probes, discussed for example new results on gamma-jet coincidence measurements, which allow to measure both momentum flow outside and fragmentation softening inside the jet cone. The theory review, finally, discussed recent developments in early thermalisation, the Equation of State as determined from gravitational wave measurements, as well as developments in the understanding of parton fragmentation and energy loss in the QGP.

The day continued with presentations on novel data-analysis techniques and R&D for detector and collider technologies. The use of Machine Learning was discussed in analysis, simulation, and in some aspects of collider operation, and the peculiarities of HEP were highlighted. A wide survey of R&D for collider experiments underlined the ever more severe demands of the high energies and luminosities of colliders. New technologies such as deep sub-micron microelectronics, nano-materials, photonics, and more might be brought to bear on the problems of radiation damage, rates and high resolution tracking requirements. Focus then turned to the somewhat different requirements of non-collider experiments, such as neutrino experiments, dark matter searches, high energy cosmic rays. Challenges here include very feeble signals in large detector masses, detector performance questions and extremely demanding control of backgrounds. R&D on isotope enrichment, pure materials and underground structures is under way. R&D for collider technologies took the floor next. Although further extensions of the present technologies such as superconducting magnets and RF accelerating systems are possible, it will become necessary, for reasons of size and cost, to find new ways to reach ever higher energies. Muon colliders or plasma accelerators may offer such paths, with a number of R&D initiatives exploring them. Investment and smaller-scale demonstrations are necessary steps on the way to realising new kinds of particle colliders.

The session was closed with an inspiring “Highlights” talk by Jon Butterworth (UCL).

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