Physicists love a challenge. Some have experiments up in space, while others work deep underground or at the tops of mountains. But just imagine how hard it must be for the those physicists who do experiments at sea.
The November 2017 issue of Physics World, which is now out in print and digital format, examines some of the challenges for physicists working below the waterline.
Jon Willis describes his experience on the exploration ship Nautilus in the Pacific Ocean, looking for mineral-rich “black smokers” that support life in conditions mimicking those on Jupiter’s icy moon Europa. Helen Czerski reveals why her studies of bubbles could help those who model climate change, while Antoine Kouchner and Véronique Van Elewyck explain why and how researchers are using the ocean as a giant neutrino detector.
Remember that if you’re a member of the Institute of Physics, you can read the whole of Physics World magazine every month via our digital apps for iOS, Android and Web browsers.
Physicists in the US reckon that cosmic-ray muons could help solve a major problem with nuclear waste – how to monitor the long-term storage of spent reactor fuel cheaply and safely. Applying detector technology normally used by particle physicists, the researchers have shown experimentally how the subatomic particles can be used on site to determine whether or not any fuel has gone missing from dry storage casks.
Spent nuclear fuel contains fission products as well as isotopes of plutonium, and must therefore be carefully monitored when removed from a nuclear reactor. It is first placed in a cooling pond for several years while short-lived fission products decay. It is then transferred to large and heavily shielded containers known as dry storage casks, located either close to the reactor or at a special waste facility.
Inspectors place special seals on the casks to reveal tampering. But if a seal degrades for any reason – it might, for example, simply corrode when exposed to the elements – then the cask in question ought to be sent back to a cooling pond for re-examination. As Matt Durham of the Los Alamos National Laboratory in New Mexico points out, the necessary handling and transport would be expensive and time-consuming. “All the nuclear workers I know in the US are careful professionals,” he says, “but there is always the possibility for accidents.”
On-site verification
Ideally, says Durham, the contents of casks would be verified on site. Numerous technologies have been put forward to do this, he notes, but all have their drawbacks – neutrons or X-rays, for example, cannot penetrate the casks’ thick shielding, while neutrinos would require enormous detectors. Muons, however, may provide the answer. Produced naturally by cosmic rays passing through the Earth’s atmosphere, muons penetrate material with a low atomic number – including a cask’s steel and concrete shielding – but are instead deflected by heavier elements, such as uranium fuel. Their degree of scattering as they pass through a cask should, therefore, reveal how much spent fuel is inside.
To put the idea to the test, Durham and colleagues at Los Alamos headed north to the Idaho National Laboratory. There they positioned a couple of muon trackers containing ionizable gas around a roughly 3 m-diameter, 5 m-high cask, with one tracker plotting the trajectories of muons as they entered the cask and the other mapping out the exit routes. The cask contained fuel removed from a Westinghouse power reactor in the 1980s. It was chosen because only 18 out of a possible 24 fuel assemblies were present, thereby allowing the researchers to try and identify the (known) empty slots.
There is always the possibility for accidents
Matt Durham, Los Alamos National Laboratory
Over the course of around three months, Durham and co-workers recorded about 450,000 muon tracks. With these data they plotted the muon scattering angle as a function of position along the cask’s diameter and also modelled how the scattering angle ought to vary if the 24 fuel-assembly slots are either all full or all empty. They then estimated the number of assemblies in six different groupings positioned along the cask diameter by gauging at each point whether the empirical plot was closer to the “all-full” or “all-empty” modelled curves.
Strong winds
Although they had to discard some of the data after strong winds shook the detectors for a few days, the researchers nevertheless correctly identified whether or not there were missing assemblies in four out of the six groupings. On this basis, they conclude that their technique is sensitive to the removal of a single fuel assembly from the centre of a cask. “This potentially represents a new method for inspectors to verify the content of a dry storage cask,” they wrote in a preprint uploaded to the arXiv server.
The researchers are now carrying out further modelling to establish whether their technique can be extended to more complicated “diversion scenarios”, such as the removal of just a portion of a fuel assembly or the replacement of an assembly with a dummy structure made from, say, lead. Durham says that the simulations look “promising” and that he and his colleagues aim eventually to test such scenarios experimentally. They also hope to carry out measurements on other types of dry storage cask.
Durham points out that although the technique was first proposed 10 years ago by his Los Alamos colleague Chris Morris, it is still quite new compared to say X-ray radiography. Nevertheless, he says that the “relevant authorities” at the International Atomic Energy Agency are aware of the work, and adds that “it has been considered” for probing the damaged reactors at Fukushima in Japan. Furthermore, he says it could be applied to the controversial nuclear deal with Iran, given that all spent nuclear fuel must be removed from the country inside heavily shielded containers.
Deployment in five years
David Ireland of the University of Glasgow, whose group has used muon scattering to inspect intermediate-level waste, says Morris and colleagues have carried out “a nice piece of work, despite the windy conditions”. He notes that although the use of naturally occurring cosmic-ray muons limits imaging speed, those muons have the virtue of not being dangerous to inspectors. Given sufficient support, and detector refinement, he estimates that a working system could be deployed “in the next five years or so”.
An auroral X-ray “hot spot” has been observed near Jupiter’s south pole for the first time. Astronomers had expected the dynamics of the planet’s northern and southern auroras to correspond – as they do on Earth – so were surprised to find that the brightness of two hot spots varied independently. Whether or not the measurements reflect a genuine discrepancy between the poles’ behaviour has consequences for our understanding of the physics behind Jupiter’s auroras.
Rare opportunity
Jupiter’s orbit and axial tilt with respect to Earth mean that chances to observe the giant-planet’s northern and southern auroras simultaneously are few and far between. Such opportunities arose in 2007 and 2016, and space-based X-ray telescopes Chandra and XMM-Newton were directed to take advantage. Now, an analysis of the data by William Dunn of University College London and collaborators in the UK, US and Spain, has revealed a persistent X-ray hot spot in the southern hemisphere. The southern hot spot has a periodicity unrelated to that of its northern counterpart, which varied much more irregularly during the observation campaign.
Even during favourable configurations like those of 2007 and 2016, the two auroral hot spots can be seen together only briefly: as one comes into view around the curve of the planet’s disc, the other recedes at the opposite limb. The simplest explanation for each pole’s different behaviour, therefore, is that the dynamics really are controlled globally, but that magnetospheric conditions varied during the observation window, suppressing the periodicity as the northern hot spot became visible.
Possible mechanisms
If the inconsistency between the poles is real, several mechanisms might explain it, according to Dunn and colleagues. Various magnetic reconnection processes; ultralow-frequency magnetic-field oscillations; and pole-specific local magnetic conditions have all been mooted.
By combining further X-ray studies over the next two years – while both poles are still visible from Earth – with measurements made in situ by NASA’s Juno mission, the researchers hope to determine whether the observed independence is normal behaviour for Jupiter’s auroras, and discover what this means for the origin of the phenomenon.
“On and around October 31, 2017, the world will celebrate the hunt for the unseen…” is the message on the Dark Matter Day website, which has been put together by physicists at universities and research labs across the globe. The site has links to more than 100 online and real-life events taking place in October and November of this year in more than 20 countries worldwide.
Why celebrate dark matter? Why not? After all, the elusive dark stuff appears to account for about 85% of the matter in the universe and its gravitational pull defines the fabric of the cosmos at galactic and greater distance scales. Furthermore, working out exactly what dark matter is could provide valuable information about physics beyond the Standard Model.
Based in Chile, the LSST will begin observing in 2021 and one of its primary goals is to create the best ever 3D map of dark matter in the universe. Rather than imaging dark matter directly – which is impossible because it doesn’t interact with light – the LSST will look at how dark matter’s gravitational tug distorts light from distant galaxies and galactic clusters.
At the risk of being apocryphal on Dark Matter Day, there is a possibility that dark matter doesn’t exist. Instead, the gravitational effect that it appears to have on visible matter could be explained by theories such as “modified Newtonian dynamics” (MOND) or other schemes that modify our conventional understanding of how gravity acts over large distances.
It turns out that the recent observation of gravitational waves and electromagnetic radiation from the merger of two neutron stars offers a way of testing theories such as MOND – according to a preprint on arXiv written by four physicists in Turkey, India and the US. The quartet calculates that if dark matter does not exist (and modified gravity is real) then the gravitational waves from the merger should have arrived 1000 days before the first gamma rays from the event were detected. Instead, the gamma rays turned-up just 1.7 s after the gravitational waves.
A triumph for dark matter, perhaps, but those calculations get us no closer to understanding exactly what dark matter is. Indeed, experiments that try to detect dark matter have so far only succeeded in telling us what dark matter isn’t.
Just yesterday two dark-matter searches reported that they have not detected the dark stuff. One is the XENON1T experiment at Italy’s Gran Sasso National Laboratory and the other is PandaX-II at the China Jinping Underground Laboratory. Both cost considerable sums of money to build and represent the hopes and dreams of many physicists worldwide. Rather than declaring this a failure, Fermilab’s Dan Hooper points out that the two null results “have further ruled out many theoretically attractive dark matter particle candidates”. You can read his article “The relentless hunt for dark matter” in Physics.
By incorporating divalent cations into alginate solutions, PhD student Thomas Valentin and colleagues at Brown University in the US have produced a noncovalently crosslinked hydrogel that is responsive to multiple stimuli. The biocompatible material, derived from algae, was used to create temporary ordered structures that could be further used as templates for fabricating more complex architectures. The researchers demonstrated the versatility of this process by creating microfluidic channels, and degradable barriers were found to direct cellular migration.
As crosslinked polymeric networks with high water content, hydrogels are an obvious choice in many different areas of research. Despite containing a lot of water, they will exhibit solid-like behaviour due to strong interactions between the polymer chains known as crosslinks. However, across all fields, the use of hydrogels is limited by the lack of control over the inner architecture of these crosslinked polymer networks.
Valentin and his colleagues used a hydrogel solution composed of alginate, metal-based cationic salts and photoinitiators. Upon exposure to a laser, the light-sensitive photoinitiators enabled the metal salts to dissolve in solution, which generated free metal cations. These cations bound to the polymer and, due to their charge, facilitated ionic crosslinking between the polymer chains. Sequential layers of hydrogel can be crosslinked through this “bottom-up” technique known as photopatterning, facilitating the production of 3D structures. Having optimized the gel composition, the researchers used light-based 3D printing to fabricate stepped structures 1.7 mm tall with a vertical resolution of 250 μm.
In contrast to conventional hydrogel crosslinking routes based on permanent covalent bonds between polymers, the ionic crosslinking is entirely reversible, enabling on demand, temporally rapid, degradation of the hydrogel material. This charge interaction is entirely reversible through chelation, where ions bind to metals. The addition of a solution containing chelating agents will dissociate the metal cations bound to polymers, thus disrupting the crosslinking and hydrogel network.
Following this new method, the alginate gels successfully templated a secondary material; agarose, a hydrogel derived from seaweed. Agarose gelled around the features already patterned within the alginate gel. Addition of chelating agents then degraded the alginate gel templates. Unaffected by this process, the agarose gel remained intact, with hollow channels where the alginate gel once was. Senior author Ian Wong describes the patterning and degradation process as being “a bit like Lego bricks. We can attach polymers together to build 3-D structures, and then gently detach them again under biocompatible conditions.”
Utilising the biocompatibility of the material, controlled patterning and degradation of the alginate hydrogel revealed new cell migration behaviour in mammary cells. Structures patterned in the alginate hydrogels spatially limited the growth of the cells within the network to certain regions. Subsequent degradation of the alginate presented unoccupied regions to the cells, which they moved into. Collective cell behaviour revealed that migration of the frontmost cells would act to straighten out the initial geometrical shapes where the cells had initially been patterned. The cells moved to occupy all available regions within two days, showing no compromise in cell viability throughout the patterning and degradation processes.
Future work is planned to improve the spatial resolution as well as control of the mechanical properties and degradation kinetics. The development of this 3D technique for patterning gels also opens the door for other ionically crosslinked gels to be patterned in this way, revolutionizing many different areas of research.
Full details of the work are reported in Lab on a Chip.
Directing chemical reactions by exploiting the quantum nature of electrons has been demonstrated for the first time by physicists at the Tata Institute of Fundamental Research, India, and the Open University in the UK. The technique could prove a cheaper alternative to lasers, which until now have been the main way researchers have sought to achieve coherent control of chemical reactions.
Tata’s E Krishnakumar and collaborators exposed molecular hydrogen and deuterium to a low-energy electron beam, and used a velocity map imaging (VMI) apparatus developed by Nigel Mason and colleagues at the Open University to observe the angular distribution of the reaction products (see video). Electrons interacting with hydrogen or deuterium molecules formed temporary negative ions in a process called resonant attachment. The molecular ions then dissociated to form neutral atoms and stable hydrogen or deuterium ions.
Unexpected asymmetry
Homonuclear diatomic molecules like hydrogen are inversion-symmetric, so such dissociative attachment involving just one electron should result in a symmetric distribution of ion products. Under the laser-induced scheme, the inversion symmetry is only broken when two coherent photons deliver odd and even angular momenta simultaneously. Yet the velocity slice images obtained by the team using VMI showed a distinct asymmetry along the inter-nuclear axis.
According to the researchers, a single electron can achieve the same symmetry breaking when it causes a superposition of two negative ion resonances with opposite parity. As the resulting quantum paths interfere, the relative phase between them determines the degree of asymmetry in the fragmentation pattern produced.
Understanding the dynamics of electron-induced dissociation will allow further insight into natural processes like radiation damage to DNA, and promises improved control over chemical reactions and nanofabrication techniques.
The capability of cells to retain the mechanosensitivity developed from different stiffness environments has been investigated by a cellular mechanobiology research groupfrom Washington University in St. Louis. The group, led by Amit Pathak, has established that cells acclimatize to a stiff surface and retain their “mechanical memory” when moved onto a soft surface, affecting their migratory behaviour (Biomaterials 146 146).
Cells are known to interact with their extracellular environment (the extracellular matrix, or ECM), with different tissues’ ECM having different physical and architectural properties. The physical stiffness of the ECM will affect cell migration and the translation of mechanical provocations to intracellular pathways. These cell behaviours, in relation to ECM stiffness, can be replicated and tested by placing cells on surfaces with different mechanical properties, enabling the testing of different microenvironments on epithelial cells.
Migration mechanics
The researchers discovered this mechanical memory through priming the cells on a stiff substrate, followed by subsequent migration to a soft substrate, where the cells retained previous migratory behaviour adopted during priming. This led to the conclusion that mechanical forces will affect cell genetics and behaviour. Overall, this affects the ability of a cell to attach to surrounding surfaces (i.e. the ECM) and migrate through tissues.
Some intracellular regulators of protein expression are also triggered by mechanical forces. When cells are placed on stiff surfaces these regulators are moved into position to increase protein expression for certain mechanisms. The translocation of a protein called yes-associated protein (YAP) to a cell’s nucleus will prime a cell for stiffness-sensitive migration. The research group showed that this mechanical memory is caused by YAP, as when YAP is deleted, this memory is lost. With YAP removed from the cellular arsenal of proteins, cells migrate across the soft surface in the same way as they do across the stiff surface.
Hydrogel-ECM stiffness
To mimic the ECM and alter the stiffness of the surface, the researchers used tuneable materials called hydrogels. Hydrogels are highly water-saturated polymeric structures, with the physical properties of a solid. In the model developed in this study, they fabricated a hydrogel construct with both a stiff and a soft section. Having regions of stiff and soft hydrogel combined within the same construct allows for seeding of cells on the stiff portion of hydrogel and easy monitoring of cell motility. This enabled the researchers to investigate cell behaviour after priming in the stiff region and movement to the softer hydrogel region.
Primed for the future
The findings from this study exemplify the importance of YAP and ECM stiffness in cell migration. These results illuminate the processes involved with cellular mechanical memory and its influence on cell migration. This can lead to insights into many different biological processes; with cellular invasion during cancer, wound healing and morphogenesis suggested as potential applications for these findings.
The authors state that potential limitations of this research arise from the use of non-physiologically relevant immortalized cell lines, which are able to proliferate freely. Also, the model presented utilizes a 2D platform for cells, unlike the in vivoenvironment where cells would be encapsulated within a 3D ECM. The information gained from these experiments, however, provides the basis for further experiments in more physiologically relevant models and cell types – potentially invaluable to research into cell migration.
Walk into a bookshop today, or even a gift shop, and you will most likely come across an entire section of colouring books for adults. This rather unexpected global trend has flourished over the past five years or so, with such books topping Amazon’s list of bestsellers in 2015. And if you thought that adult colouring books were a passing fad, as I did when they first started popping up everywhere, then you would be wrong – the market is booming.
The idea behind these books was for adults to have an easy and relaxing activity – whether it’s some form of childhood nostalgia, or a way of switching off and doing something completely different from what most of us do at work. Now, you can find colouring books for grown-ups that feature everything from abstract patterns and detailed nature scenes to books based on films, television shows and even celebrity figures.
It’s no surprise then, that there are quite a few colouring books that are distinctly science-themed. Visions of Numberland: a Colouring Journey Through the Mysteries of Maths by Alex Bellos and Edmund Harriss is one such book that landed on my desk. Its brightly coloured cover is immediately eye-catching and a quick flick through it will reveal a dazzling array of shapes, patterns and illustrations, all waiting to be filled in. The book boasts a total of 60 patterns you can colour in, as well as a “create” section at the end of the book that helps you build your own patterns.
Bellos, who regularly writes about mathematics for the Guardian, is also the author of Alex’s Adventures in Numberland (2010) and Alex Through the Looking-Glass. As for Harriss, he is also a mathematician, teaching at the University of Arkansas, US, but he also specializes in illustrating and creating mathematical art. Between the two of them, Bellos and Harriss have released four colouring books including this latest one, all of which have a mathematical twist.
The illustrations in Visions of Numberland span concepts in algebra, geometry, topology and even computer algorithms. You will come across everything from the familiar Pythagoras theorem to the “hairy ball theorem” (see image). Some of the concepts discussed are well known and understood, while others, such as the Collatz conjecture, are famous “unsolved problems”, making it an interesting mix of things old and new. The square-format book has large illustrations and simple explanations.
Multidimensional spiral: Sarah adds colour to the Hopf fibration. (Courtesy: James Dacey)
But let’s not forget that this is primarily a colouring book, and if the proof of the pudding is in the eating, then the proof of Visions of Numberland is in the filling (in). I do own a few other grown-up colouring books (mostly presents), and while I liked the idea of them initially, I had never actually taken the time to sit down and colour. For the sake of this review, I did have a go at some of the illustrations in the book. The first one I coloured in was the seaweed-like illustration of the aforementioned Collatz conjecture, which describes a mathematical number sequence. I did enjoy pencilling in the tendril-like branches and I was pleased with the final blue and purple hues of my completed picture, which you can see above, but I did find myself getting a bit frustrated with carefully filling in the many small sections.
Despite my impatience, I realized by the time I finished that I was focused solely on the colouring – so maybe it does work as a de-stressing activity? My colleague and Physics World features editor Sarah Tesh, who is more artistically inclined, also coloured in one of the images – she picked the “Hopf fibration”, which is (rather confusingly) a 2D image of a 3D structure built to visualize the surfaces of a 4D sphere – and found the activity rather relaxing. Although I did enjoy the colouring activity and the beautiful pictures that feature in Visions of Numberland, what I ultimately liked best about the book was the actual mathematics discussed. More than half of the concepts and conjectures in the book were new to me and I found them fascinating enough to look them up in an effort to learn more about them. This book is therefore less relaxing colouring book and more mathematical popularization in the best way possible.
Another colouring book for adults, released last month, is Phases of Matter, written and created by condensed-matter physicists Colm P Kelleher, Rodrigo E Guerra, Andrew D Hollingsworth and Paul M Chaikin. According to the authors, the book’s aim is to “explore the beautiful patterns create by microscopic particles in the experiments and computer simulations we conduct in our labs at New York University”. At first glance, I thought this book was a fascinating experiment in popularizing an area of physics that doesn’t often hit the headlines, and I am sure that is what the authors intended. Unfortunately, I do not think they were very successful.
Comb over: The hairy-ball theorem states that it is impossible to comb a hairy sphere completely flat – at least one tuft will be left sticking up. (Image adapted from Visions of Numberland published by Bloomsbury Publishing)
While I enjoyed some of the initial write-up on how the researchers image colloidal particles in the lab, how the particles arrange themselves in a lattice, and how changes in phase occur, I do not think it works as an actual colouring book at all. All of the “images” are full pages covered in minuscule triangles or hexagons with little to no variation. While it is clear to see that each image is tessellated in different ways (to show changes in phase) the patterns look mostly the same. While this does show the reader how a solid and a liquid do not differ that much on a microscopic scale, it makes for an extremely tedious colouring book and I could not bring myself to even try fill in the endless tiny shapes. Indeed, the patterns are so repetitive that you could use this as a distraction akin to doodling while you work, rather than a fun activity. Also, some of the initial microscope images are blurry and out of focus – especially frustrating for pictures that mainly consist of a grid of black dots.
Phases of Matter, while a good idea, was unfortunately badly executed – the book could have really used a professional artist or designer who would have taken the basic ideas and shapes suggested by the researchers and made the patterns more compelling.
Alex Bellos and Edmund Harriss Visions of Numberland: a Colouring Journey Through the Mysteries of Maths 2017 Bloomsbury Publishing 144pp £9.99pb
Colm P Kelleher, Rodrigo E Guerra, Andrew D Hollingsworth and Paul M Chaikin Phases of Matter 2017 Green Frog Publishing 62pp £10.99pb
Researchers in the US have been inspired by octopuses and cuttlefish to create a new kind of shape-shifting artificial “skin”. Based at Cornell University and the Marine Biological Laboratory in Woods Hole, Massachusetts, the scientists have shown that the artificial skin can rapidly change from flat sheets to pre-programmed 3D shapes that imitate stones, plants and other natural objects.
Octopuses and cuttlefish camouflage themselves by transforming their skin from smooth to complexly textured, as well as changing colour. The purpose is primarily to hide the outline of the body as seen from different perspectives, explains Roger Hanlon, of the Marine Biological Laboratory. “Moreover, the 3D texture tends to resemble the surrounding 3D texture of algae, corals, etc,” he says. “It is a general resemblance to 3D surrounds, not meant to specifically mimic one sort of plant, animal or inert background.”
Muscular hydrostats
The creatures do this using sets of independently controlled 3D features (called “papillae”) in their skin. The shapes of these papillae can transform from flat to protruding because of erector muscle fibres that are stacked horizontally in concentric circles around each papilla’s central axis. When the fibres contract, they create a force towards the centre of the papilla that pressurizes the surrounding soft tissue and causes it to stretch, in tension, away from the skin. This is an example of a muscular hydrostat – movable biological structures based around tightly packed, incompressible muscle with no skeletal support. Other examples include elephant trunks, octopus arms, and our own tongues.
In their simplest form, when extended, the papillae would be conical in shape. But different arrangements of muscles, and papillae consisting of multiple muscular hydrostats working together, create more complex shapes. By changing them from flat to fully extended, or any shape in between, octopuses and cuttlefish can rapidly transform their skin through a cascade of 3D forms.
Fibre-mesh rings
Inspired by the structure of the papillae, the researchers created a silicon elastomer skin embedded with rings of fibre mesh. When this skin is inflated, the silicone stretches, while the fibre mesh takes on the role of muscle fibres, providing a force towards the central axis and controlling the 3D shape. By changing the shape and positioning of the fibre-mesh rings, the team was able to produce a range of complex 3D structures, including a bed of non-symmetrical and hierarchical stones, and a succulent plant, with leaves arranged in a spiral around a central point.
Cornell team member James Pikul told Physics World that the shapes they produced function in the same way as the papillae, as “they do not change their fully inflated shape, but can be expressed anywhere between fully flat and fully actuated”. “By combining both the degree of inflation and which synthetic shape we actuate, we can change our texture. This ability allows cephalopods to use the same papillae to camouflage into many different environments. It would also allow us to control the specific surface area, for future technologies, or shadowing, for camouflaging in a sunny environment.”
Robots and computers
“Soft, stretchable materials are really great for human–robot or human–computer interaction,” adds Pikul. “So making controllers or displays that can change shape, or disappear into a surface, could be exciting applications.”
Pikul also points out that the surfaces of materials play an important role in many technologies – such as batteries, and heat and cooling technologies – and that there could be “a lot of opportunities in coupling these geometric transformations with technologies where surface structure and chemistry are important”.
A new measurement technique used by CERN’s BASE collaboration has constrained the magnetic moment of the antiproton with parts-per-billion precision – a huge improvement over the roughly one-part-per-million precision achieved by the same team in January. The result means that the magnetic moment of the antiproton is now known even more precisely than the magnetic moment of the proton itself.
Crucial to the 350-fold improvement in precision was the simultaneous measurement of the cyclotron frequency of one antiproton and of the Larmor frequency of another antiproton. By using a “hot” particle in the cyclotron measurement, the researchers avoided the need for a time-consuming cooling step in each cycle of their experiment. This allowed the team to make measurements at a much greater rate than before, and three times faster than they managed when they measured the proton’s magnetic moment in 2014.
Equal and opposite
Discrepancies between the properties of protons and antiprotons could explain the overwhelming dominance of normal matter in the universe – something that is not explained by the Standard Model of particle physics. Anybody hoping for hints of new physics beyond the Standard Model will be disappointed, however, because the result is consistent with protons and antiprotons having magnetic moments that are opposite but equal.
The researchers expect to achieve a further improvement in precision by upgrading the experiment’s magnetic shielding and cooling system, and by using a more homogeneous magnetic field in the precision trap.
By Matin Durrani
