BLOGS

Worrying trend Reliable climate models are needed so that societies can adapt to the impact of climate change. (Courtesy: Shutterstock/Migel)

Topics: Applied Physics, Atmospheric Science, CERN, Civilization, Climate Change

It was a scorcher last year. Land and sea temperatures were up to 0.2 °C (32.36 °F) higher every single month in the second half of 2023, with these warm anomalies continuing into 2024. We know the world is warming, but the sudden heat spike had not been predicted. As NASA climate scientist Gavin Schmidt wrote in Nature recently: “It’s humbling and a bit worrying to admit that no year has confounded climate scientists’ predictive capabilities more than 2023 has.”

As Schmidt went on to explain, a spell of record-breaking warmth had been deemed “unlikely” despite 2023 being an El Niño year, where the relatively cool waters in the central and eastern equatorial Pacific Ocean are replaced with warmer waters. Trouble is, the complex interactions between atmospheric deep convection and equatorial modes of ocean variability, which lie behind El Niño, are poorly resolved in conventional climate models.

Our inability to simulate El Niño properly with current climate models (J. Climate 10.1175/JCLI-D-21-0648.1) is symptomatic of a much bigger problem. In 2011 I argued that contemporary climate models were not good enough to simulate the changing nature of weather extremes such as droughts, heat waves and floods (see “A CERN for climate change” March 2011 p13). With grid-point spacings typically around 100 km, these models provide a blurred, distorted vision of the future climate. For variables like rainfall, the systematic errors associated with such low spatial resolution are larger than the climate-change signals that the models attempt to predict.

Reliable climate models are vitally required so that societies can adapt to climate change, assess the urgency of reaching net-zero or implement geoengineering solutions if things get really bad. Yet how is it possible to adapt if we don’t know whether droughts, heat waves, storms or floods cause the greater threat? How do we assess the urgency of net-zero if models cannot simulate “tipping” points? How is it possible to agree on potential geoengineering solutions if it is not possible to reliably assess whether spraying aerosols in the stratosphere will weaken the monsoons or reduce the moisture supply to the tropical rainforests? Climate modelers have to take the issue of model inadequacy much more seriously if they wish to provide society with reliable actionable information about climate change.

I concluded in 2011 that we needed to develop global climate models with spatial resolution of around 1 km (with compatible temporal resolution) and the only way to achieve this is to pool human and computer resources to create one or more internationally federated institutes. In other words, we need a “CERN for climate change” – an effort inspired by the particle-physics facility near Geneva, which has become an emblem for international collaboration and progress.

Why we still need a CERN for climate change, Tim Palmer, Physics World

Colleagues remember Peter Higgs as an inspirational scientist who remained humble despite his fame. Credit: Graham Clark/Alamy

Topics: CERN, Higgs Boson, High Energy Physics, Nobel Prize, Particle Physics, Quantum Mechanics, Theoretical Physics

Few scientists have enjoyed as much fame in recent years as British theoretical physicist Peter Higgs, the namesake of the boson that was discovered in 2012, who died on 8 April, aged 94.

It was 60 years ago when Higgs first suggested how an elementary particle of unusual properties could pervade the universe in the form of an invisible field, giving other elementary particles their masses. Several other physicists independently thought of this mechanism around the same time, including François Englert, now at the Free University of Brussels. The particle was a crucial element of the theoretical edifice that physicists were building in those years, which later became known as the standard model of particles and fields.

Two separate experiments at the Large Hadron Collider (LHC) near Geneva, Switzerland — ATLAS and the CMS — confirmed Higgs’ predictions when they announced the discovery of the Higgs boson half a century later. It was the last missing component of the standard model, and Higgs and Englert shared a Nobel Prize in 2013 for predicting its existence. Physicists at the LHC continue to learn about the properties of the Higgs boson, but some researchers say that only a dedicated collider that can produce the particle in copious amounts — dubbed a ‘Higgs factory’ — will enable them to gain a profound understanding of its role.

“Besides his outstanding contributions to particle physics, Peter was a very special person, an immensely inspiring figure for physicists around the world, a man of rare modesty, a great teacher and someone who explained physics in a very simple yet profound way,” said Fabiola Gianotti, director-general of CERN in an obituary posted on the organization’s website; Gianotti who announced the Higgs boson’s discovery to the world at CERN. “I am very saddened, and I will miss him sorely.”

Many physicists took to X, formerly Twitter, to pay tribute to Higgs and share their favorite memories of him. “RIP to Peter Higgs. The search for the Higgs boson was my primary focus for the first part of my career. He was a very humble man that contributed something immensely deep to our understanding of the universe,” posted Kyle Cranmer, physicist at the University of Wisconsin Madison and previously a senior member of the Higgs search team at the CMS.

Nanos gigantum humeris insidentes is a Latin phrase that translates to "dwarfs standing on the shoulders of giants." It's a Western metaphor that expresses the idea of "discovering truth by building on previous discoveries." The phrase is derived from Greek mythology, where the blind giant Orion carried his servant Cedalion on his shoulders.

English scientist Sir Isaac Newton also coined the phrase "to stand on (someone's) shoulders" in his letter, "If I have seen further it is by standing on the shoulders of Giants." This means that we are who we are because of the hard work of the people who came before us. Newton was talking about collective learning, or our species' ability to share, preserve, and build upon knowledge over time. Source: AI overview

Peter Higgs: science mourns giant of particle physics, Davide Castelvecchi, Nature

Image source: CERN - accelerating science

Topics: CERN, Condensed Matter Physics, Entanglement, Lasers, Quantum Mechanics

Much of modern experimental physics relies on a counterintuitive principle: Under the right circumstances, zapping matter with a laser doesn’t inject energy into the system; rather, it sucks the energy out. By cooling the system to a fraction of a degree above absolute zero, one can observe quantum effects that are otherwise invisible.

Laser cooling works like a charm, but only when a system’s ladder of quantum states is just right. Atoms of alkali metals and a few other elements are ideal. Molecules, with their multitudes of energy levels, pose a much greater challenge. And fundamental particles such as protons, which lack internal states altogether, can’t be laser-cooled at all.

Nevertheless, there’s a lot of interest in experimenting on protons at low temperature—in particular, precisely testing how their mass, magnetic moment, and other properties compare with those of antiprotons. Toward that end, the Baryon Antibaryon Symmetry Experiment (BASE) collaboration has now demonstrated a method for using a cloud of laser-cooled beryllium ions to sympathetically cool a single proton, even when the proton and ions are too distant to directly interact.

A superconducting circuit is a cooling teleporter, Johanna L. Miller, Physics Today

New territory Two candidate collider-neutrino events from the FASERν pilot detector in the plane longitudinal to (top) and transverse to (bottom) the beam direction. The different lines in each event show charged-particle tracks originating from the neutrino interaction point. Credit: FASER Collaboration.

Topics: CERN, High Energy Physics, Particle Physics, Research

Think “neutrino detector” and images of giant installations come to mind, necessary to compensate for the vanishingly small interaction probability of neutrinos with matter. The extreme luminosity of proton-proton collisions at the LHC, however, produces a large neutrino flux in the forward direction, with energies leading to cross-sections high enough for neutrinos to be detected using a much more compact apparatus.

In March, the CERN research board approved the Scattering and Neutrino Detector (SND@LHC) for installation in an unused tunnel that links the LHC to the SPS, 480 m downstream from the ATLAS experiment. Designed to detect neutrinos produced in a hitherto unexplored pseudo-rapidity range (7.2 < 𝜂 < 8.6), the experiment will complement and extend the physics reach of the other LHC experiments — in particular FASERν, which was approved last year. Construction of FASERν, which is located in an unused service tunnel on the opposite side of ATLAS along the LHC beamline (covering |𝜂|>9.1), was completed in March, while installation of SND@LHC is about to begin.

Both experiments will be able to detect neutrinos of all types, with SND@LHC positioned off the beamline to detect neutrinos produced at slightly larger angles. Expected to commence data-taking during LHC Run 3 in spring 2022, these latest additions to the LHC experiment family are poised to make the first observations of collider neutrinos while opening new searches for feebly interacting particles and other new physics.

Collider neutrinos on the horizon, Matthew Chalmers, CERN Courier

Illustration of the FASER experiment. Image Credit: FASER/CERN.

Topics: CERN, Dark Matter, High Energy Physics, Neutrinos, Particle Physics

Neutrinos are ubiquitous and notorious. Billions are passing through you at this moment. Occasionally described as a “ghost of a particle,” neutrinos are nearly massless, thereby making them extremely difficult to detect experimentally (“Neutrino,” meaning “little neutral one” in Italian, was first used by Enrico Fermi in the early 1930s). Neutrinos were first confirmed in 1956 (thanks to a nearby nuclear reactor), and they’ve since been detected from different sources, including the Sun and cosmic rays, but not yet in a particle collider. Their elusiveness has been the source of much intrigue (and, of course, research funding) within the particle physics community since.

What else makes them so curious? Neutrinos come in three flavors — electron neutrino, muon neutrino, and tau neutrino — and may switch between them through the process of oscillation. Neutrino oscillations have been experimentally confirmed only in the past decade at the Super-K Detector in Japan (physicists Takaaki Kajita and Arthur B. McDonald shared the 2015 Nobel Prize in Physics for it). This discovery signified an important direction in the search for physics beyond the Standard Model because the longstanding theory does not explain neutrino oscillations and describes them as completely massless particles. Something isn’t quite adding up.

Enter: FASER. Initially proposed in 2018, the ForwArd Search ExpeRiment (FASER) is CERN’s newest experiment poised to detect neutrinos, potentially up to 1300 electron neutrinos, 20,000 muon neutrinos, and 20 tau neutrinos. Constructed in an unused service tunnel located about 500 meters from an Atlas experiment interaction point, FASER and its corresponding sub-detector, FASERν, have been designed to probe interactions of high-energy neutrinos (predicted to be between 600 GeV and 1 TeV).

FASER Poised to Further Our Understanding of Neutrinos, Dark Matter, Hannah Pell, Physics Central Buzz Blog