TEDxCERN breaks the rules

On 9 October, TEDxCERN brought together 15 "rule-breakers" to explore ideas that push beyond the boundaries of academia. They addressed a full house of 600 audience members, as well as thousands watching the event online.

TEDxCERN broke all of the rules this year – starting with its choice of venue. The CMS construction hall at Point 5 was converted into a gala centre, complete with sound stage and dance floor. It was a stunning transformation that also brought to life the hall’s to-scale photo of the CMS detector. The image served as the backdrop to a light-projection show entitled "Turbulence", by artist François Moncarey.

From singer-songwriter Imogen Heap to CERN’s own Edda Gschwendtner, the line-up of speakers was as diverse as it was educational. They discussed using tangible interfaces that allow human interaction via e-devices, the potential of 3D technology to revolutionise education and product fabrication, and even explored transformation of matter into habitable structures.

• You can find the full programme of speakers on the TEDxCERN website, see tedxcern.web.cern.ch/.


Life in extreme environments discussed at the LSC

The Deep Underground Laboratory Integrated Activity in biology (DULIA-bio) workshop was held on 13 and 14 October at the Canfranc Underground Laboratory (LSC), in Spain. The LSC (CERN Courier November 2015 p29) is one of the four deep-underground laboratories (DULs) in Europe, together with Boulby (UK), Gran Sasso (Italy) and Modane (France). Twenty-eight scientists, physicists and biologists, gathered at the LSC and others participated remotely from SNOlab, in Canada. The aim of the workshop, supported by DULs, the Astroparticle Physics European Consortium (ApPEC) and the Istituto de Fisica Corpuscular in Valencia, was to establish a common framework for DULs in deep-life studies and their applications in astrobiology.

In the 1990s it became apparent that life is also possible in subsurface and extreme environments, and could actually have originated in the subsurface of the Earth. Today, many questions remain. What factors control the maximum depth limit where life is still possible? What are the sources of carbon for deep-seated life? And what processes regulate the energy flux for deep-seated life? Micro-organisms living under extreme conditions on Earth could shed light on the question of life on other planets because subsurface ecosystems are functioning independently of the surface environment and this could be similar for subsurface life on other planets. In this respect, the search for life in the universe could be pursued through studies in deep-underground facilities on Earth, which offer a unique opportunity to investigate the subject and to answer these fundamental questions. The different geological locations of the DULs enhance the possibility and variability of investigations.

One of the subjects discussed at DULIA-bio was the effects on biological systems of prolonged exposure to ionising radiation levels below natural background. Studies on how natural-background radiation is essential for life to maintain genomic stability in living organisms were presented from research carried out at Gran Sasso and SNOlab. Micro-organisms inhabiting the inside of rocks are studied at Canfranc by the GOLLUM project, due to the fact that underground spaces are the perfect site for extremophile ecology studies. Ongoing work at the Boulby underground laboratory includes studies of microbial life found in salt layers, and on the development of instrumentation to look for life on other planets.

DULIA-bio has been the first of a number of workshops organised by DULs in Europe to strengthen the integrated activities and the multidisciplinary features of these unique facilities.

• For more information, see https://indico.cern.ch/event/436589/.


Strong coupling: a workshop at CERN reviews latest advances

The latest progress in measurement of the strong interaction coupling was discussed in a recent workshop on "High precision measurements of αs: from LHC to FCC-ee", held at CERN on 12–13 October. The meeting brought together leading experts in the field to explore in-depth recent theoretical and experimental developments on the determination of αs, new ways to measure this coupling in lepton–lepton, lepton–hadron and hadron–hadron collisions and, in particular, the improvements expected at the proposed Future Circular Collider e+e (FCC-ee) facility.

In quantum chromodynamics (QCD), the coupling constant αs sets the scale of the strength of the interaction at a given reference scale (usually taken at the Z boson mass), and it is one of the fundamental parameters of the Standard Model (SM). The αs coupling, known up to now with δα≈ ±0.5% uncertainty, is the least precisely known of all fundamental constants in nature, orders-of-magnitude less well known than the gravitational (δG ≈ ±10–5), Fermi’s (δGF ≈ ±10−8), and fine-structure (δα ≈ ±10−10) constants. Improving our knowledge of α is a prerequisite to reduce the theoretical uncertainties in the calculations of all perturbative QCD (pQCD) processes whose cross-sections or decay rates depend on higher-order powers of αs, as is the case for virtually all of those measured at the LHC. In the introductory session, S Bethke presented the preliminary 2015 update of the Particle-Data-Group (PDG) world-average αs, obtained from comparison of next-to-next-to-leading-order (NNLO) pQCD calculations with a set of six groups of experimental data. Enlarged uncertainties from lattice QCD and tau–lepton decays, as well as the first NNLO extraction from top-pair cross-sections at the LHC, have doubled the uncertainty on αs, which will move from αs = 0.1185±0.0006 to αs = 0.1177±0.0013. L Mihaila reviewed the impact on Higgs physics of αs, which is the second major contributor – after the bottom mass – to the parametric uncertainties of its dominant H → bb partial decay, and the largest source of uncertainty for the cc and gg decay modes. An accurate knowledge of the running of αs at TeV energy scales is also crucial for physics searches beyond the SM. F Sannino presented generic exclusion bounds on masses of new coloured particles based on LHC data.

The second session of the workshop was devoted to low-energy studies of the QCD coupling, such as from lattice QCD (covered by P Mackenzie and X Garcia i Tormo), pion (J-L Kneur), τ (A Pich) and Υ (J Soto) decays, and soft parton-to-hadron fragmentation functions (FFs) (R Perez-Ramos). The comparison of pQCD predictions with computational lattice-QCD "data", yielding αs = 0.1184±0.0012, still provides the most precise αs extraction with a δαs ≈ ±1% uncertainty. Hadronic decays of the tau lepton yield αs = 0.1187±0.0023 (i.e. δαs = ±1.9%), although the results of different theoretical approaches are still a matter of debate. The pion decay factor was proposed as a new observable to extract αs = 0.1174±0.0017, notwithstanding the low scales involved, which challenge the pQCD applicability. Decays of the b–bbound state (Υ) used to constrain the QCD coupling until a few years ago (αs = 0.1190±0.0070), but their lower degree of (NLO) theoretical accuracy should be improved to be included in future PDG updates. Similarly, the energy evolution of the distribution of hadrons in jets has proven to be a novel robust method to extract αs = 0.1205±0.0022, but the calculations need to go beyond their current approximate-NNLO accuracy.

Future measurements

Determinations of αs at higher energy scales – including global fits of parton distribution functions (PDFs) (reviewed by J Bluemlein), hard parton-to-hadron FFs (B Kniehl), jets in e±p (M Klasen), e+e event shapes (S Kluth, A Hoang), jet cross-sections in e+e (A Banfi), Z and W decays (K Moenig, M Srebre), and the e+e  hadrons cross-section (J Kuehn)– were covered in the third workshop section. The NNLO analyses of PDFs have good precision (δαs = ±1.7%), albeit yielding a central value lower than the rest of the methods: αs = 0.1154±0.0020.

Upcoming NNLO fits of the jet FFs will provide a QCD coupling that is more accurate than the current one at NLO (αs = 0.1176±0.0055). Similarly, a full-NNLO analysis of jet production in e±p is needed to improve the current αs = 0.121±0.003 extraction from these observables. Electron–positron event shapes and jet rates yield αs = 0.1174±0.0051 with a δαs = ±4.3% uncertainty, but new e+e data at lower and higher energies than LEP are required for better control of hadronisation corrections. The hadronic decays of electroweak bosons are high-precision observables for extraction of the strong coupling. The current Z data provide αs = 0.1196±0.0030, i.e. δαs = ±2.5%, which can be reduced to below ±0.3% with the huge statistical data sets expected at the FCC-ee. The W hadronic decay data are not as precise today, but promise the same αs sensitivity with measurements at the FCC-ee. The final session was dedicated to αs extractions at hadron colliders. Important NNLO theoretical developments for top-quark pair and jet cross-sections were reviewed by A  Mitov, G Salam and J Pires. A lowish αs = 0.1151±0.0028 value with δαs = ±2.5% uncertainty is obtained using the only tt- cross-sections published so far by CMS, although inclusion of all preliminary data increases it to αs ≈ 0.1201±0.0025. The imminent release of the NNLO calculation for jets will provide a huge boost for PDFs, FFs and cross-section studies in pp, e±p and γp collisions. To date, the NLO combination of ATLAS, CMS and Tevatron jet results yields αs = 0.1179±0.0023. Existing and planned measurements of αs at the LHC were also reviewed by B Malaescu (ATLAS) and K Rabbertz (CMS), clearly confirming asymptotic freedom at multi-TeV scales. The results of the workshop will be incorporated into the FCC Conceptual Design Report under preparation. Whereas the strong force decreases with energy, scientific interest in the QCD interaction clearly proves constant, if not increasing, with time.

• For more information, see indico.cern.ch/e/alphas2015.


CAS course on Advanced Accelerator Physics held in Warsaw, Poland

The CERN Accelerator School (CAS) and the National Centre for Nuclear Research (NCBJ) recently organised a course on advanced accelerator physics, which took place in Warsaw, Poland, from 27 September to 9 October.

The course followed an established format with lectures in the mornings and practical courses in the afternoons. The lecture programme consisted of 34 talks, supplemented by private study, tutorials and seminars. The practical courses provided "hands-on" experience in three topics: beam instrumentation and diagnostics; RF measurement techniques; and optics design and corrections. Participants selected one of the three courses and followed the chosen topic throughout the school.

Sixty-six students representing 18 nationalities attended the course, with most participants coming from European counties, but also from Korea, Taiwan and Russia. Feedback from the participants was positive, reflecting the high standard of the lectures and teaching.

NCBJ provided excellent facilities and invaluable support for the highly technical courses, which are a key feature of the advanced school. They also organised an optional visit to their reactor, which is used for research and industrial purposes, and provided live beam facilities through electron linacs for "hands-on" experience.

Forthcoming CAS courses will be a specialised school on free electron lasers and energy-recovery linacs (FELs and ERLs) (Hamburg, Germany, 31 May–10 June 2016), an introduction to accelerator physics (Istanbul, Turkey, September 2016) and a specialised school on beam injection, extraction and transfer to be held at CERN in November 2016.

• See www.cern.ch/schools/CAS.


Science pops in Geneva

This year, CERN celebrated European Researchers’ Night with a series of events and activities organised in the framework of the EU-funded project POPScience. The day was jam-packed with activities that presented science through comic strips, games, cinema and television. Around 500 children attended the sessions for schools organised at Balexert, Geneva’s popular multiplex cinema, and 600 spectators flocked to the public screenings.

Using the big screen, scientists, directors and authors were on hand to disentangle truth from untruths and science from science fiction. The guests, some of whom appeared in person and others via video link, included Jorge Cham, author of PhD Comics and the spin-off film; David Saltzberg, physicist at CMS and scientific consultant for the television series The Big Bang Theory; Kip Thorne, scientific consultant for the film Interstellar; Lawrence Krauss, author of The Physics of Star Trek; and Italian astronaut Roberto Vittori, who gave a commentary on the film Gravity.

In the main area of the shopping centre, CERN scientists performed experiments for the public. In the multimedia shop FNAC, authors signed books, customers enjoyed virtual tours of the CMS experiment via television screens, physicists answered numerous questions, and children built Lego detectors.


HEPMAD 15 brings high-energy physics to Madagascar

HEPMAD 15, the 7th High-Energy Physics International Conference, was held in Antananarivo, the capital of Madagascar, on 17–22 September, with the official opening ceremony taking place at the National Malagasy Academy and sessions at the École Normale Supérieure.

The conference, initiated by Stephan Narison of the Laboratoire Univers et Particules of Montpellier in 2001, alternates with the series of QCD-Montpellier conferences that he started in 1985. It aims both to be pedagogical – Narison presented his book for the general public, Particles and the Universe (World Scientific, in press) to a large audience – and to report on the latest experimental and theoretical results. There were around 50 participants with 15 invited speakers from abroad.

Recent results were presented from ATLAS and CMS on tests of the Standard Model, improved measurements of the Higgs couplings, searches for new physics beyond the Standard Model, top-quark properties and B-meson physics. The ALICE collaboration reported results on heavy quarkonia in quark–gluon plasma, while results on kaon and B-meson physics, CP-violation and the Cabibbo–Kobayashi–Maskawa matrix were presented by NA48/NA62 and BELLE. BELLE has also reviewed searches for exotic XYZ hadrons, which have been complemented by preliminary predictions of their masses and couplings from QCD spectral sum rules, including next-to-next-to-leading-order perturbative corrections. Other reports covered some aspects of astrophysics and the new HAWC gamma-ray observatory in Mexico. The conference also included poster presentations by national researchers on other areas of physics: climatology, physics of the atmosphere, the environment and nuclear physics.

There were also discussions on the organisation of the next conference, HEPMAD 17, the possibility of holding the African School of Physics in Madagascar in the near future and, in general, the development of physical sciences in Africa and in the Indian Ocean area. Here, Narison emphasised his wish for the creation of an International Physics Centre in Madagascar for African Sub-Saharan, Indian Ocean, South Asian and Australian physicists.

Finally, the conference provided an opportunity for foreign participants to discover the natural richness and traditions of Madagascar, as well as its social poverty, exemplified by the "exotic" bus used for the excursions.

• HEPMAD 15 was co-organised by the HEPMAD Research Institute of Antananarivo and the Association Gasy Miara-Mandroso (AGMM). Visit www.lupm.univ-montp2.fr/users/qcd/hepmad15/.