Faces and places

Tanaka to head SLAC neutrino group  • SESAME appoints technical director  • Four winners of 2018 Edison Volta Prize  • Accelerator awards presented at IPAC  • Panjab University honours Virdee  • Kaplan wins for Particle Fever  • Brazil signs up to IPPOG collaboration  • CERN: Science Bridging Cultures  • ALICE marks quarter century  • Accelerator aficionados meet in Vancouver  • The history and future of the PHYSTAT series  • Antimatter research leaps ahead  • FCC presents at tunnel congress
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Tanaka to head SLAC neutrino group

Neutrino physicist Hirohisa Tanaka has moved from the University of Toronto (Canada) to SLAC National Accelerator Laboratory in the US to expand the lab’s role in the Deep Underground Neutrino Experiment (DUNE). The experiment, which will study neutrinos produced by Fermilab’s Long-Baseline Neutrino Facility approximately 1300 km away, is due to start up in the mid-2020s and will address critical issues such as whether CP violation exists in the neutrino sector and what is the hierarchy of the neutrino masses.

Tanaka completed his PhD at SLAC in 2002 and went on to work on neutrino experiments at Fermilab (MiniBooNE) and J-PARC (T2K). The SLAC group’s growing activities include developing the data readout and reconstruction for liquid-argon detectors like those used in DUNE, and the design of the near detector at Fermilab.

“If we’re lucky, we may see the first hints of asymmetries between neutrinos and antineutrinos with current experiments,” says Tanaka. “In the long run, DUNE

will give us the definite answers due to its longer baseline and higher-power neutrino beam.”

SESAME appoints technical director

The third-generation light source SESAME in Jordan has appointed Riccardo Bartolini as technical director, overseeing the facility’s infrastructure through its start-up phase. Bartolini’s experience ranges from synchrotron light sources to free-electron lasers and colliders. While serving as SESAME’s technical director, he will divide his time between Jordan and the UK’s Diamond Light Source, where he is head of the accelerator physics group, and will be on leave from the John Adams Institute at the University of Oxford.

“It is great to be part of a project that promotes science and peace, and it is a privilege to carry on the work done by my predecessors Einfeld, Vignola, Nadji and Huttel,” he said.

SESAME was established under the auspices of UNESCO in 2002 and is modeled closely on CERN. It produced “first light” in 2017 and, last month, inaugurated a second beamline (CERN Courier March 2017 p8).

Four winners of 2018 Edison Volta Prize

The 2018 European Physical Society (EPS)Edison Volta Prize, organised in conjunction with the Fondazione Alessandro Volta and energy firm Edison S.p.A., has been awarded to four gravitational-wave researchers.

Alain Brillet (Observatoire de la Cote d’Azur, Nice, France), Karsten Danzmann (Max-Planck-Institut für Gravitationsphysik and Leibniz University, Hannover, Germany), Adalberto Giazotto (INFN, Pisa) and Jim Hough (University of Glasgow, UK) were recognised “for the development, in their respective countries, of key technologies and innovative experimental solutions, that enabled the advanced interferometric gravitational-wave detectors LIGO and Virgo to detect the first gravitational-wave signals from mergers of black holes and of neutron stars.” The EPS Edison Volta Prize is given biennially to individuals or groups of up to three people. Giazatto (CERN Courier April 2018 p55) was awarded posthumously.

Accelerator awards presented at IPAC

On 3 May, during a ceremony at the International Particle Accelerator Conference in Vancouver (see “Accelerator aficionados meet in Vancouver”), the American Physical Society (APS) and the Institute of Electrical and Electronics Engineers (IEEE) presented their 2018 awards recognising excellence in the accelerator field.

The recipient of the 2018 thesis award granted by the APS division of physics of beams is Sergey Antipov of CERN, who was honoured “for experimental studies and analysis of the electron cloud build-up and corresponding instability in accelerators with combined function magnets and for the development of an effective mitigation technique applied in Fermilab’s recycler ring”. Also receiving his certificate was last year’s thesis-award recipient Spencer Gessner of SLAC National Accelerator Laboratory, who was cited for “an original theoretical treatment and an experimental demonstration of accelerating positrons in a hollow channel plasma wakefield accelerator”. Alexander Wu Chao of SLAC National Accelerator Laboratory, winner of the prestigious 2018 APS Robert R. Wilson Prize for Achievement announced late last year (CERN Courier December 2017 p35), also received his award during the Vancouver ceremony.

The IEEE Particle Accelerator Science and Technology (PAST) award, made on behalf of IEEE’s nuclear and plasma sciences society, is given to individuals who have made outstanding contributions to accelerator science and technology. Hermann Grunder, director emeritus at Argonne National Laboratory in the US, was honoured “for his far-reaching contributions to accelerator science and technology”, which span nuclear physics, high-energy and heavy-ion accelerators, and applications of accelerators in medical research. Sandra Biedron of the University of New Mexico received the award “for broad impact in accelerator science and technology”, which includes contributions to the FERMI@Elettra free-electron laser in Italy, and R&D in advanced controls, novel diagnostics and high-power electron guns.

The 2018 PAST Doctoral Student Award, in recognition of significant and innovative technical contributions to the field of particle accelerator science and technology, was presented to Martina Martinello of Fermilab “for contributions to physical understanding of limiting factors in SRF cavities”.

Panjab University honours Virdee

On 4 March, CMS physicist Tejinder (Jim) Virdee of Imperial College, London, was awarded an honorary doctorate by Panjab University, India, in recognition of his outstanding contribution to the LHC’s CMS experiment. Between 1993 and 2006, Virdee was the deputy spokesperson of CMS and, later, spokesperson for three years from 2007. He played a crucial role in all phases of the CMS experiment since its formation and, during the experiment’s early period, travelled widely to engage, excite and invite the participation of physicists from around the world.

Kaplan wins for Particle Fever

A documentary about the Large Hadron Collider (LHC) has won producer David Kaplan, a theorist at Johns Hopkins University in the US, the 2018 Andrew Gemant Award. The annual prize, awarded by the American Institute of Physics, recognises contributions to the cultural, artistic and human dimensions of physics and includes a cash sum of $5000 and a grant of $3000 to further the public communication of physics.

Particle Fever follows six physicists during the LHC switch-on, and the film has won multiple awards since its launch in 2013. Kaplan, whose research interests include the Higgs boson and dark matter, completed a year of film school before pursuing physics at the University of California, Berkeley.

“I wanted to give the experiential version of the story where people would learn the science only because it was a key part of the narrative – it wasn’t the goal to teach them physics. You can’t learn particle physics in 90 minutes, but you can experience the process of it,” he says.

Brazil signs up to IPPOG collaboration

The International Particle Physics Outreach Group (IPPOG) has welcomed Brazil as a new member, boosting efforts to expand the group’s international impact on scientific outreach. Established 20 years ago as a European network, IPPOG has grown to a global network that involves countries, laboratories and scientific collaborations active in particle physics. It is best known for its international masterclasses programme, which evolved in the late 1990s from national outreach efforts. Following the model of collaboration in experimental particle physics, IPPOG became a formal scientific collaboration based on a memorandum of understanding (MoU) in 2017 (CERN Courier March 2017 p5).

Brazil, which will be officially represented in IPPOG by Marcelo Munhoz of the University of São Paulo, is one of several countries to formally join the collaboration in recent months. In April, at the 15th IPPOG collaboration meeting in Pisa, two further countries – Slovenia and the Czech Republic – confirmed their membership, while Greece and Austria are finalising the process to sign IPPOG’s MoU. That will bring IPPOG’s total number of members to 26 – including the Belle II experiment, which has just started operations at KEK in Japan (see SuperKEKB steps out at the intensity frontier).

CERN: Science Bridging Cultures

A book launched at CERN on 26 April in the presence of Pedro Afonso Comissário, ambassador of Mozambique to the United Nations, provides a glimpse into CERN’s nature as a centre of knowledge creation and a true melting pot of skills. Devised, edited and assembled by Marilena Streit-Bianchi, a former member of staff, CERN: Science Bridging Cultures brings together texts written by CERN scientists, project leaders, department heads and directors. It contains illustrations by the Mozambican artist Justino António Cardoso and has been translated into several languages.

ALICE marks quarter century 

On 21 March, members of the ALICE collaboration celebrated 25 years since the experiment was founded. On 1 March 1993, the recently formed ALICE collaboration submitted a letter of intent to the CERN Large Hadron Collider (LHC) committee, proposing the construction of a heavy-ion experiment dedicated to the study of strongly interacting matter produced in nucleus–nucleus collisions. The effort has been rewarded with major advances in our understanding of the quark–gluon plasma and with the discovery of new phenomena, such as the detection of collective effects and strangeness enhancement in small collision systems (CERN Courier April 2017 p26). The ATLAS and CMS collaborations celebrated their 25th birthdays in October.

Accelerator aficionados meet in Vancouver

The 9th International Particle Accelerator Conference (IPAC18) was held in Vancouver, Canada, from 29 April to 4 May. Hosted by TRIUMF and jointly sponsored by the IEEE Nuclear and Plasma Sciences Society and the APS Division of Physics of Beams, the event attracted more than 1210 delegates from 31 countries, plus 80 industry exhibits staff. The scientific programme included 63 invited talks and 62 contributed orals, organised according to eight main classes. While impossible to summarise the full programme in a short article, below are some of the highlights from IPAC18 that demonstrate the breadth and vibrancy of the accelerator field at this time.

A foray into the future of accelerators by Stephen Brooks of Brookhaven National Laboratory was a walk on the wild side. The idea of a single-particle collider was presented as a possibility to achieve diffraction-limited TeV beams to bridge the potential “energy desert” between current technology and the next energy regime of interest. Relevant technological and theoretical challenges were discussed, including multiple ideas for overcoming emittance growth from synchrotron radiation, focusing beams (via gravitational lensing!) and obtaining nucleus-level alignment, as was how to reduce the cost of future accelerators.

The rise of X-ray free-electron lasers in the past decade, opening new scientific avenues in areas highly related to wider society, was a strong theme of the conference. In addition, in the session devoted to photon sources and electron accelerators, Michael Spata described the Jefferson Laboratory’s 12 GeV upgrade of CEBAF, which began full-power operation in April after overcoming numerous challenges (including installation and operation of a new 4 kW helium liquefier, and field-emission limitations in the cryomodules). James Rosenzweig (UCLA) described progress towards an all-optical “fifth-generation” light source. Here, a TW laser pulse would be split into two, with half being used to accelerate high-quality electron bunches as they co-propagate in a tapered undulator, and the other half striking the accelerated electron beam head on so that the back-scattered photons are shifted to much shorter wavelengths. The scheme could lead to a compact, tunable multi-MeV gamma-ray source, and successful demonstrations have already taken place at the RUBICONICS test stand at UCLA.

Concerning novel particle sources and acceleration techniques, plasma-wakefield acceleration featured large. CERN’s Marlene Turner described progress at the AWAKE experiment, which aims to use a high-energy proton beam to generate a plasma wake that is then used to accelerate an electron beam. Last year, the AWAKE team demonstrated self-modulation of the proton beam and measured the formation of the plasma wakefield. Now the team has installed the equipment to test the acceleration of an injected electron beam, which is expected to be completed in 2018. Felicie Albert of Lawrence Livermore National Laboratory also described the use of laser-wakefield technology to generate betatron X rays, which could enable new measurements at X-ray free-electron lasers.

With IPAC18 coinciding with TRIUMF’s 50th anniversary (CERN Courier May 2018 p31), laboratory director Jonathan Bagger described the evolution of TRIUMF from its founding in 1968 by three local universities to the present-day set-up with 20 member universities, users drawn from 38 countries and an annual budget of CA$100 million. Also in the hadron-accelerator session was a talk by Sergei Nagaitsev of Fermilab about the path to the Long-Baseline Neutrino Facility, which is actually three parallel paths: one for the proton beams (PIP-II), one for the detector which will be located in the Homestake mine in South Dakota (DUNE) 1300 km away, and one for the facilities at Fermilab and Homestake. The three projects will engage more than 175 institutions from around the world with the aim of investigating leptonic CP violation and the mass hierarchy in the neutrino sector. The International Facility for Antiproton and Ion Research (FAIR) under construction in Germany (CERN Courier July/August 2007 p4) was another focus of this session, with Mei Bai of GSI Darmstadt summarising the significant upgrade of the heavy-ion synchrotron SIS18 that will drive the world’s most intense uranium beams for future FAIR operation.

In the session devoted to beam dynamics and electromagnetic fields, Valery Telnov (Budker Institute) introduced a cautionary note about bremsstrahlung at the interaction points of future electron–positron colliders (such as FCC-ee) that will impact beam lifetimes whereas present-generation colliders (such as SuperKEKB) are dominated by synchrotron radiation in the arcs. Tessa Charles of the University of Melbourne, meanwhile, introduced the method of “caustics” to understand and optimise longitudinal beam-dynamics problems, such as how to minimise coherent synchrotron radiation effects in recirculation arcs.

The proton linac for the European Spallation Source (ESS) under construction in Sweden was presented by Morten Jensen during the session on accelerator technology. He outlined the variety of radio-frequency (RF) power sources used in the ESS proton linac and the development of the first-ever MW-class “inductive out tubes” for the linac’s high-beta cavities, which have been tested at CERN and reached record-beating performances of 1.2 MW output for 8.3 kW input power. Pending the development of a production series, the accelerator community may have a new RF workhorse.

As indicated, these are just a few of the many scientific highlights from IPAC18. Industry was also a major presence. In an industry panel discussion, speakers talked about successful models for technology transfer, while talks such as that from Will Kleeven (IBA) described the Rhodotron compact industrial CW electron accelerator producing intense beams with energies in the range from around 1 to 10 MeV, which has key industry applications including polymer cross-linking, sterilisation, food treatment and container security scanning.

IPAC is committed to welcoming young researchers, offering more than 100 student grants and heavily discounted fees for all students. Almost 1500 posters were presented by authors from 233 institutions over four days. The regional attendance distribution was 24% from Asia, 41% from Europe and 35% from the Americas, demonstrating the truly international nature of our field. The 10th IPAC will take place in Melbourne, Australia, on 19–24 May 2019.

  • Shane Koscielniak (TRIUMF) and Tor Raubenheimer (SLAC), IPAC18 chairs.

The history and future of the PHYSTAT series

Most particle-physics conferences emphasise the results of physics analyses. The PHYSTAT series is different: speakers are told not to bother about the actual results, but are reminded that the main topics of interest are the statistical techniques used, the resulting uncertainty on measurements, and how systematics are incorporated. What makes good statistical practice so important is that particle-physics experiments are expensive in human effort, time and money. It is thus very worthwhile to use reliable statistical techniques to extract the maximum information from data (but no more).

Origins

Late in 1999, I had the idea of a meeting devoted solely to statistical issues, and in particular to confidence intervals and upper limits for parameters of interest. With the help of CERN’s statistics guru Fred James, a meeting was organised at CERN in January 2000 and attracted 180 participants. It was quickly followed by a similar one at Fermilab in the US, and further meetings took place at Durham (2002), SLAC (2003) and Oxford (2005). These workshops dealt with general statistical issues in particle physics, such as: multivariate methods for separating signal from background; comparisons between Bayesian and frequentist approaches; blind analyses; treatment of systematics; p-values or likelihood ratios for hypothesis testing; goodness-of-fit techniques; the “look elsewhere” effect; and how to combine results from different analyses.

Subsequent meetings were devoted to topics in specific areas within high-energy physics. Thus, in 2007 and 2011, CERN hosted two more meetings focusing on issues relevant for data analysis at the Large Hadron Collider (LHC), and particularly on searches for new physics. At the 2011 meeting, a whole day was devoted to unfolding, that is, correcting observed data for detector smearing effects. More recently, two PHYSTAT-ν workshops took place at the Institute for Physics and Mathematics of the Universe in Japan (2016) and at Fermilab (2017). They concentrated on issues that arise in analysing data from neutrino experiments, which are now reaching exciting levels of precision. In between these events, there were two smaller workshops at the Banff International Research Station in Canada, which featured the “Banff Challenges” – in which participants were asked to decide which of many simulated data sets contained a possible signal of new physics.

The PHYSTAT workshops have largely avoided having parallel sessions so that participants have the opportunity to hear all of the talks. From the very first meetings, the atmosphere has been enhanced by the presence of statisticians; more than 50 have participated in the various meetings over the years. Most of the workshops start with a statistics lecture at an introductory level to help people with less experience in this field understand the subsequent talks and discussions. The final pair of summary talks are then traditionally given by a statistician and a particle physicist.

A key role

PHYSTAT has played a role in the evolution of the way particle physicists employ statistical methods in their research, and has also had a real influence on specific topics. For instance, at the SLAC meeting in 2003, Jerry Friedman (a SLAC statistician who was previously a particle physicist) spoke about boosted decision trees for separating signal from background; such algorithms are now very commonly used for event selection in particle physics. Another example is unfolding, which was discussed at the 2011 meeting at CERN; the Lausanne statistician Victor Panaretos spoke about theoretical aspects, and subsequently his then student Mikael Kuusela became part of the CMS experiment, and has provided much valuable input to analyses involving unfolding. PHYSTAT is also one of the factors that has helped in raising the level of respectability with which statistics is regarded by particle physicists. Thus, graduate summer schools (such as those organised by CERN) now have lecture courses on statistics, some conferences include plenary talks, and books on particle-physics methodology have chapters devoted to statistics. With the growth in size and complexity of data in this field, a thorough grounding in statistics is going to become even more important.

Recently, Olaf Behnke of DESY in Hamburg has taken over the organisation and planning of the PHYSTAT programme and already there are ideas regarding having a monthly lecture series, a further PHYSTAT-ν workshop at CERN in January 2019 and a PHYSTAT-LHC meeting in autumn 2019, and possibly one devoted to statistical issues in dark-matter experiments. In all probability, the future of PHYSTAT is bright.

  • Louis Lyons, Imperial College, London, and University of Oxford, UK.

Antimatter research leaps ahead

The 13th Low Energy Antiproton Physics (LEAP) conference was held from 12–16 March at the Sorbonne University International Conference Center in Paris. A large part of the conference focused on experiments at the CERN Antiproton Decelerator (AD), in particular the outstanding results recently obtained by ALPHA and BASE.

One of the main goals of this field is to explain the lack of antimatter observed in the present universe, which demands that physicists look for any difference between matter and antimatter, apart from their quantum numbers. Specifically, experiments at the AD make ultra-precise measurements to test charge-party-time (CPT) invariance and soon, via the free-fall of antihydrogen atoms, the gravitational equivalence principle to look for any differences between matter and antimatter that would point to new physics.

The March meeting began with talks about antimatter in space. AMS-02 results, based on a sample of 3.49 × 105 antiprotons detected during the past four years onboard the International Space Station, showed that antiprotons, protons and positrons have the same rigidity spectrum in the energy range 60–500 GeV. This is not expected in the case of pure secondary production and could be a hint of dark-matter interactions (CERN Courier December 2016 p31). The development of facilities at the AD, including the new ELENA facility, and at the Facility for Antiproton and Ion Research Facility (FAIR), were also described. FAIR, under construction in Darmstadt, Germany, will increase the antiproton flux by at least a factor of 10 compared to ELENA and allow new physics studies focusing, for example, on the interactions between antimatter and radioactive beams (CERN Courier July/August 2017 p41).

Talks covering experimental results and the theory of antiproton interactions with matter, and the study of the physics of antihydrogen, were complemented with discussions on other types of antimatter systems, such as purely leptonic positronium and muonium. Measurements of these systems offer tests of CPT in a different sector, but their short-lived nature could make experiments here even more challenging than those on antihydrogen.

Stefan Ulmer and Christian Smorra from the AD’s BASE experiment described how they managed to keep antiprotons in a magnetic trap for more than 400 days under an astonishingly low pressure of 5 × 10–19 mbar. There is no gauge to measure such a value, only the lifetime of antiprotons and the probability of annihilation with residual gas in the trap. The feat allowed the team to set the best direct limit so far on the lifetime of the antiproton: 21.7 years (indirect observations from astrophysics indicate an antiproton lifetime in the megayear range). The BASE measurement of the proton-to-antiproton charge over mass ratio (CERN Courier September 2015 p7) is consistent with CPT invariance and, with a precision of 0.69 × 10–12, it is the most stringent test of CPT with baryons. The BASE comparison of the magnetic moment of the proton and the antiproton at the level of 2 × 10–10 is another impressive achievement and is also consistent with CPT (CERN Courier March 2017 p7).

Three new results from ALPHA, which has now achieved stable operation in the manipulation of antihydrogen atoms that has allowed spectroscopy to be performed on 15,000 antiatoms, were also presented. Tim Friesen presented the hyperfine spectrum and Takamasa Momose presented the spectroscopy of the 1S–2P transition. Chris Rasmussen presented the 1S–2S lineshape, which gives a resonant frequency consistent with that of hydrogen at a precision of 2 × 10–12 or an energy level of 2 × 10–20 GeV, already exceeding the precision on the mass difference between neutral kaons and antikaons. ALPHA’s rapid progress suggests hydrogen- like precision in antihydrogen is achievable, opening unprecedented tests of CPT symmetry (CERN Courier March 2018 p30).

The next edition of the LEAP conference will take place at Berkeley in the US in August 2020. Given the recent pace of research in this relatively new field of fundamental exploration, we can look forward to a wealth of new results between now and then.

  • Patrice Pérez, CEA Saclay.

FCC presents at tunnel congress

The World Tunnel Congress (WTC) brings together leading tunnel and underground-space experts from all around the world. This year, the congress was held in Dubai from 21 to 26 April and was attended by nearly 2000 professionals, with case studies illuminating the latest trends and innovations and discussions about the role of tunnels in supporting future sustainable cities. CERN’s Future Circular Collider (FCC) study – which is exploring the possibility of a 100 km-circumference collider (see CERN thinks bigger) – would require one of the world’s largest ever underground projects, generating great interest from WTC delegates.

The extensive underground tunnel works required for FCC were presented by John Osborne from CERN and by Werner Dallapiazza from ILF Consulting, who have been tasked with performing a cost and schedule study for the civil-engineering aspects of the FCC study.

The FCC could provide a facility able to host machines in several different collider modes, as well as four very large experimental caverns and service caverns at depths of up to approximately 300 m below the surface. The key challenges for civil engineering come from the difficult geology under Lake Geneva, the river Arve crossing and the area where the river Rhone exits the Geneva basin. In addition, solutions for the 9.2 million cubic metres of excavated rock and other environmental issues need to be studied further.

  • John Osborne, CERN.