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Has IceCube Spotted Cosmic Neutrinos?
Physicists at the IceCube Neutrino Observatory have detected high-energy neutrinos that may have come from cosmic events such as star formation or black holes. If so, these will be among the first observations of their kind, confirming the possibility of studying astronomy through particles seen in underground observatories. As blogger Michael DuVernois notes, this form of astronomy offers a new approach to studying our universe– instead of stargazing we can study the particles seen in underground observatories to better understand the cosmos.
IceCube probable astrophysical events
By Michael DuVernois | May 20, 2013Okay, so there hasn’t been an official IceCube press release on this, not until the paper finishes collaboration review and is posted on the Arxiv, but there have been some talks showing neutrino events observed by IceCube which are almost certainly astrophysical in origin. Short version, neutrino astronomy is now a real thing. We are observing the universe in photons (ever since we looked up at the night sky, and starting with Galileo with increasingly sophisticated instruments) and also in neutrinos (which travel undisturbed from deep within the astrophysical objects, reflecting the nuclear interactions deep within).
Leaping and hopping on a moonshadow
By Marcos Santander | August 31, 2011How do you align a telescope to make sure it’s pointing in the right direction? Piece of cake: you use any cheap sky mapping software that could give you the position of a star in the sky at a given time for your location, you point your telescope in that direction and make sure that you see the right star. Done!
Always check your sources
By Marcos Santander | August 1, 2010Haim Harari said once, and for all, that “neutrino physics is largely an art of learning a big deal by observing nothing.” These words are as true today as they were when Harari stated them, but today we finally have the necessary tools to start seeing something, if we’re patient enough to wait for these neutrino sources to reveal themselves to our telescopes watching the whole sky. So, if you’re as patient as we are to read this long post, you’ll have a decent idea of how we try to pinpoint these sources.
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This Fermilab press release came out today.
Fermilab’s new Run Like A Proton accelerator path at the Lederman Science Center is now open. Photo: Reidar Hahn
It’s one thing for kids to try to envision particles zipping around underground when learning about the science at Fermilab. It’s another thing entirely for them to pretend to be particles charging along an accelerator path, revealing new physics as they fly by.
This week the Fermilab Education Office celebrated the completion of its new Run Like A Proton accelerator path for middle- and high-school-age visitors to the laboratory.
Located at the Lederman Science Center, the path is an aboveground, scaled-down version of the routes a particle can take through Fermilab’s accelerator complex. While running along the path, kids can act like they are the particles of the lab’s physics program zipping through underground tunnels.
“Kids have different modes of learning,” said Spencer Pasero of Fermilab’s Education Office. “They can learn about the work of the lab with our indoor exhibits, but now they can also learn about it through our new outdoor playground.”
It’s a playground with a physics lesson. Kids playing the parts of protons and antiprotons “collide” by high-fiving each other as they run along the accelerator path. Signs along the path guide them in the right direction, whether they want to follow the path a proton would take as it circles the Main Injector or assume the flight of a neutrino headed toward Minnesota.
Kids won’t be limited to playing the part of particle. If they want a role as someone who sets the particles in motion, they can learn about how an operator interacts with the accelerator complex as she works with her controls on the playground.
At more than 100 feet across – longer than a basketball court – the path gives kids plenty of space to let loose in their particle impressions.
The accelerator path is the first stage in the laboratory’s long-term plan to build a larger physics playground.
The Fermilab Education Office has already taken the Run Like A Proton accelerator path for a test drive with a few student groups, and the new outdoor feature has been a hit.
“Students run like a proton around the accelerator path, and afterward when they go on a tour of Fermilab, the docents ask them, ‘Remember when you were running like a proton?’” said Marge Bardeen, head of the Education Office. “And they remember! What a great way to learn.”
The Run Like A Proton accelerator path is made possible by a grant from the Kane County Riverboat Fund and a contribution from an anonymous donor, both through the Fermilab Friends for Science Education, which supports innovative programs at Fermilab. A ribbon-cutting ceremony for the playground was held on Tuesday, May 21, at the Lederman Science Center.
The Lederman Science Center is open to the public Monday to Friday, 8:30 a.m. to 4:30 p.m. and on Saturdays from 9 a.m. to 3 p.m.
“We hope this playground will activate kids’ imaginations and that they immerse themselves in the physics we’ve been doing at the lab for 30 years,” Pasero said.
Note to readers: this is my best attempt to describe some issues in accelerator operations; I welcome comments from people more expert than me if you think I don’t have things quite right.
The operators of the Large Hadron Collider seek to collide as many protons as possible. The experimenters who study these collisions seek to observe as many proton collisions as possible. Everyone can agree on the goal of maximizing the number of collisions that can be used to make discoveries. But where the accelerator physicists and particle physicists might part ways over just how those collisions might best be delivered.
Let’s remember that the proton beams that circulate in the LHC are not a continuous current like you might imagine running through your electric appliances. Instead, the beam is bunched — about 1011 protons are gathered in a formation that is about as long as a sewing needle, and each proton beam is made up of 1380 such bunches. As the bunches travel around the LHC ring, they are separated by 50 nanoseconds in time. This bunching is necessary for the operation of the experiments — it ensures that collisions occur only at certain spots along the ring (where the detectors are) and the experiments can know exactly when the collisions are occurring and synchronize the response of the detector to that time. Note that because there are so many protons in each beam, there can be multiple collisions each time two bunches pass by each other. At the end of the last LHC run, there were typically 30 collisions that occurred per bunch crossing.
There are several ways to maximize the number of collisions that occur. Increasing the number of protons in each bunch crossing will certainly increase the number of collisions. Or, one could imagine increasing the total number of bunches per beam, and thus the number of bunch crossings. The collision rate increases like the square of the number of particles per bunch, but only linearly with the number of bunches. On the face of it, then, it would make more sense to add more particles to each bunch rather than to increase the number of bunches if one wanted to maximize the total number of collisions.
But the issue is slightly more subtle than that. The more collisions that occur per beam crossing, the harder the collisions are to interpret. With 30 collisions happening at the same time, one must contend with hundreds, if not thousands, of charged particle tracks that cross each other and are harder to reconstruct, which means more computing time to process the event. With more stuff going on each event, the most important parts of the event are increasingly obscured by everything else that is going on, degrading the energy and momentum resolution that are needed to help identify the decay products of particles like the Higgs boson. So from the perspective of an experimenter at the LHC, one wants to maximize the number of collisions while having as few collisions per bunch crossing as possible, to keep the interpretation of each bunch crossing simple. This argument favors increasing the number of bunches, even if this might ultimately mean having fewer total collisions than could be obtained by increasing the number of protons per bunch. It’s not very useful to record collisions that you can’t interpret because the events are just too busy.
This is the dilemma that the LHC and the experiments will face as we get ready to run in 2015. In the current jargon, the question is whether to run with 50 ns between collisions, as we did in 2010-12, or 25 ns between collisions. For the reasons given above, the experiments generally prefer to run with a 25 ns spacing. At peak collision rates, the number of collisions per crossing is expected to be about 25, a number that we know we can handle on the basis of previous experience. In contrast, the LHC operators generally to prefer the 50 ns spacing, for a variety of operational reasons, including being able to focus the beams better. The total number of collisions delivered per year could be about twice as large with 50 ns spacing…but with many more collisions per bunch crossing, perhaps by a factor of three. This is possibly more than the experiments could handle, and it could well be necessary to limit the peak beam intensities, and thus the total number of collisions, to allow the experiment to operate.
So how will the LHC operate in 2015 — at 25 ns or 50 ns spacing? One factor in this is that the machine has only done test runs at 25 ns spacing, to understand what issues might be faced. The LHC operators will re-commission the machine with 50 ns spacing, with the intention of switching to 25 ns spacing later, as soon as a couple of months later if all goes well. But then imagine that 50 ns running works very well outset. Would the collision pileup issues motivate the LHC to change the bunch spacing? Or would the machine operators just like to keep going with a machine that is operating well?
In ancient history I worked on the CDF experiment at the Tevatron, which was preparing to start running again in 2001 after some major reconfigurations. It was anticipated that the Tevatron was going to start out with a 396 ns bunch spacing and then eventually switch over to 132 ns, just like we’re imagining for the LHC in 2015. We designed all of the experiment’s electronics to be able to function in either mode. But in the end, 132 ns running never happened; increases in collision rates were achieved by increasing beam currents. This was less of an issue at the Tevatron, as the overall collision rate was much smaller, but the detectors still ended up operating with numbers of collisions per bunch crossing much larger than they were designed for.
In light of that, I find myself asking — will the LHC ever operate in 25 ns mode? What do you think? If anyone would like to make an informal wager (as much as is permitted by law) on the matter, let me know. We’ll pay out at the start of the next long shutdown at the end of 2017.
I’ve been away from blogging for quite some time – mainly to finish a book I was working on. The book is unrelated to particle physics, but follows a course I teach at Harvard, called Primitive Navigation. We explore navigational techniques used by cultures like the Polynesians and Norse, in addition to looking at environmental topics like the origins of ocean currents and global weather systems. While doing research for the book and the course, I found that humans have always been exceedingly clever in making sense of their environments and harnessing this knowledge to journey long distances. I found that the ability of humans to develop sophisticated constructs to bring order to their environment is not limited to the lineage of Western scientific thought but is a more universal trait.
We often think of the roots of science starting with the ancient Greeks, or even further back to the Babylonians. The canonical history is a marriage of mathematics and logic coupled with empirical observation. The story stretches through the Arab translations of works like Euclid’s Elements during the Dark and Middle Ages, through the emergence of the scientific revolution, and culminating in the dizzying heights of modern works like quantum field theory. This is not to say that there weren’t hiccups. Although most scientists would dismiss astrology as quackery, astronomy and astrology were once deeply intertwined from their Western birth in Babylon through the time of Kepler.
I invite you to take a big step back and ponder the following conjecture – that Homo sapiens has always been intrinsically disposed toward scientific thinking. This is perhaps not ‘science’ in the way we view Western science, but it still has the existence of conceptual framework on which to hang and connect observations.
In the process of doing research for the book, I interacted with a number of anthropologists who are studying the navigational schemes of Pacific Islanders. Their work demonstrates the existence of an exceedingly sophisticated ‘toolkit’ of navigational schema that allowed them to travel huge distances across the ocean to find small target islands successfully. Three anthropologists in particular have uncovered some amazing findings: Cathy Pyrek, Rick Feinberg, and Joe Genz.
Most archaeological evidence points to the emergence of long-distance voyaging by a group called the Lapita people, circa 1600 BC from the Bismarck Archipelago, near New Guinea. They built craft capable of sailing into the wind, making jumps of hundreds of miles eastward to locations like Fiji, Tonga, Tahiti and the Marquesas. Even more astonishing was the rapid explosion of voyages of thousands of miles around AD 1000 to Hawaii and the north island of New Zealand.
In order to sail against the wind, one needs to create a sail capable of lift, like a wing and use it in combination with a hull that ‘grabs’ the water as it slices through. The Lapita figured how to harness the complex fluid dynamics involved in lift and used it to their advantage. In the 18th century, Captain James Cook marveled at sophisticated design of the Polynesian voyaging canoes that allowed them to travel at speeds far in excess of Western European vessels. It wasn’t until 1904 that physicist Ludwig Prandtl laid out the theoretical basis for lift in wings, and wasn’t until the 1970’s that this theory was applied to sails.
The clever design of voyaging canoes was only part of the innovations the Pacific Islanders. In order to sail across vast stretches of ocean, they needed viable navigational schema. We don’t have written records from the height of the voyaging period for Polynesians (circa AD 1000), but we do have interviews with modern day practitioners of indigenous navigational techniques that hint at the ways their ancestors crossed large stretches of ocean accurately.
Anthropologists Rick Feinberg and Cathy Pyrek from Kent State have shown how indigenous navigators in eastern Solomon Islands use a ‘navigational tool-kit’, that consists of multiple signs. Stars that are rising or setting close to the horizon form a natural star-compass. Their rising and setting positions allow navigators to find the ‘azimuth’ or compass heading toward a destination island. This requires the navigator to memorize a large number of stars and become familiar with their paths across the sky at different times of the year.
While a star compass may be useful, what does a navigator do during the day or in overcast weather? Another helpful construct is a wind-compass. Winds blowing from different directions have different characteristics. In the eastern Solomons, the trade winds blow from the southeast, and are marked by characteristic ‘trade wind cumulus’ clouds that only grow to heights of roughly 15,000 feet and are then truncated. These winds mark the direction ‘tonga’, or the southeast, which corresponds to the direction of the island cluster of Tonga. Winds from the north arrive during the winter months and are associated with variable, stormy weather.
Steady winds and storm systems can also create ocean swells that act as reliable direction indicators. Often, multiple swells can arise – for example, the Southern Ocean produces a long swell from the south, while trade winds can create shorter wavelength swells from the east. Even if the wind shifts, the swells retain some ‘memory’ of the winds that created them allowing the navigator to maintain a steady heading.
The above tools are useful in maintaining direction under different conditions, but there’s an inherent uncertainty in the position of a vessel, and this uncertainty grows with time. A navigator completing a 200-mile journey may only be able to establish a position to within 20 or 30 miles. Another trick then comes into play: birds. Certain birds, like pelicans and frigate birds will fly some distance out to sea to feed, and then will return to their home islands in the evening. A sailor only has to get to within 30 miles of a target island and then observe land-based birds. The sail is dropped and when the birds fly home in the evening, a course is set.
The navigational toolkit allows for a kind of successive approximation, where the stars, wind, and swells form a rough guide, and the presence and behavior of birds provides the final precision.
A somewhat related but unique tradition is that of wave-piloting in the Marshall Islands. Most of us are familiar with refraction and reflection of waves, whether they’re light or sound waves. Waves on the oceans’ surface are similar, but have some notable differences. First waves in deep-water have a speed that is proportional to the square root of the wavelength. Second, waves in shallow water have a speed that’s proportional to the square root of the depth. This latter relation causes waves to refract in shallow water. When waves get into very shallow water, they’ll often break, losing much, if not all of their energy. On the other hand, waves impinging on a steep cliff that extends underwater will reflect with very little energy lost. Depending on the bathymetry surrounding an island, one can get very different wave patterns produced by the interaction of an incident swell with the island.
Joe Genz from the University of Hawaii studied the tradition of Marshall Island wave piloting for his doctoral thesis. Navigators in the Marshalls have their own language for describing characteristic wave patterns around islands. Nit in kōt is the name given to a crossing pattern of waves on the lee side of an island. If a uniform swell impinges in the eastern shore of an island, the waves passing the north shore will be refracted inside the swell-shadow toward the south and the waves passing the south shore will be refracted into the swell-shadow toward the north. The resulting pattern of crossing waves creates a disturbed region that’s easy to identify at distances beyond which the islands are visible.
In principle, reflected ways should also give clues to the presence of an island. Joe made the acquaintance of one Captain Korent Joel, a native Marshall Islander who was trying to revive the tradition of wave piloting. Joe persuaded Captain Korent to demonstrate his wave piloting technique to a group of oceanographers who deployed a set of sensitive wave buoys. As Captain Korent left the atoll of Arno, he first pointed out the incoming swell from the east, and then the reflected swell off of Arno.
There was only one problem. No one on the boat with Captain Korent could notice the reflections, although the dominant eastern swell was clearly visible. Even the sensitive wave buoys couldn’t detect the presence of the reflected swell. What was going on? Joe wondered whether Captain Korent just thought he should be seeing a reflected swell and was making this up.
In order to put Captain Korent to a sterner test, Joe waited until he (Captain Korent) was taking a nap on in the cabin. Joe instructed the crew to motor some 30 miles to the southwest of Arno to get to a new location. When Captain Korent woke up, Joe told him that he had taken the boat to an undisclosed location and asked him if he could identify the direction to Arno, and the kind of wave patterns he was seeing. Captain Korent was quite certain the Arno was to the northwest, and he was also quite correct! So, he was reading the waves properly after all!
I met Joe in person at a conference of the Association for Social Anthropology in Oceania (ASAO) in Portland Oregon in February 2012. Joe had some videos on his laptop of Captain Korent and shared them with me. I downloaded them to my computer. That evening, I watched the video where Captain Korent was pointing out the reflected swell to Joe on the boat. This was the reflected swell that Joe couldn’t see, and the oceanographer’s buoys couldn’t detect. Joe told me what Captain Korent was saying in Marshallese about the waves. I do some sea kayaking, and I’m often close to the water, and am a bit of an amateur wave-watcher myself.
In my first viewing of the video, I could definitely see the incoming dominant swell from the east. But, by the third or fourth viewing, I could see a weaker reflected swell moving at slight angle against the larger incoming swell. When I compared my observations to what Captain Korent was saying in Marshallese, they agreed completely! By the tenth viewing, I became 100% convinced that Captain Korent was pointing out the reflected swell correctly.
The next day, I called Joe over, along with Cathy Pyrek, who was also attending the ASAO conference. I pulled up the video on my laptop and showed what I saw as the reflected swell. Joe said, “Oh yeah, now I see it”. I turned to Cathy and asked if she really saw it, or I was just convincing them of it, but she said,“It’s definitely there, it’s strange that everyone missed it.”
We still have much to learn about how the human mind operates, but it struck me that Captain Korent’s talents show how we’re capable of picking up very weak signals in the presence of noise. Evidently there is more information on the surface of the ocean than the oceanographer’s buoys were capable of recording. This is perhaps not surprising, but it’s evidence that there are different frameworks of knowledge out there that are effective and are based on empiricism. It may not be Western, but it is a kind of science.
For further reading:
Joeseph Genz, et al., “Wave Navigation in the Marshall Islands,” Oceanography, 22, June 2009, 234-245.
Joseph Genz, “Marshallese Navigation and Voyaging: Re-learning and Reviving Indigenous Knowledge of the Ocean,” (PhD diss., University of Hawaii, 2008)
John Huth, The Lost Art of Finding Our Way, (Belknap Press, Cambridge MA, 2013).
Twitter: @JohnHuth1
Okay, so there hasn’t been an official IceCube press release on this, not until the paper finishes collaboration review and is posted on the Arxiv, but there have been some talks showing neutrino events observed by IceCube which are almost certainly astrophysical in origin. Short version, neutrino astronomy is now a real thing. We are observing the universe in photons (ever since we looked up at the night sky, and starting with Galileo with increasingly sophisticated instruments) and also in neutrinos (which travel undisturbed from deep within the astrophysical objects, reflecting the nuclear interactions deep within).
One of the over 5000 DOMs (Digital Optical Modules) which make up the IceCube Observatory being deployed into the ice.
There’s a nice Gizmodo article with interesting comments.
University of Wisconsin news item.
Phys.org coverage of the news item.
New Scientist entry written by our friend Anil who got to visit IceCube during construction.
Since the middle of last week, the news are spread around and there are Russian, Spanish, and French language versions (at a minimum!) of the news. Previously, only the neutrinos from Supernova 1987A had been seen from beyond the sun and the Earth’s atmosphere. Analysis is still ongoing, so this isn’t a final result by any means, but it is a proof-of-functionality of the IceCube detector and of neutrino astronomy.
Addition:
Scientific American’s article includes good quotes from the three Wisconsin-Madison postdocs who led the analysis, Nathan, Claudio, and Naoko.
This essay makes a point that is only implicit in most of my other essays–namely that scientists are arro—oops that is for another post. The point here is that science is defined not by how it goes about acquiring knowledge but rather by how it defines knowledge. The underlying claim is that the definitions of knowledge as used, for example, in philosophy are not useful and that science has the one definition that has so far proven fruitful. No, not arrogant at all.
The classical concept of knowledge was described by Plato (428/427 BCE – 348/347 BCE) as having to meet three criteria: it must be justified, true, and believed. That description does seem reasonable. After all, can something be considered knowledge if it is false? Similarly, would we consider a correct guess knowledge? Guess right three times in a row and you are considered an expert –but do you have knowledge? Believed, I have more trouble with that: believed by whom? Certainly, something that no one believes is not knowledge even if true and justified.
The above criteria for knowledge seem like common sense and the ancient Greek philosophers had a real knack for encapsulating the common sense view of the world in their philosophy. But common sense is frequently wrong, so let us look at those criteria with a more jaundiced eye. Let us start with the first criteria: it must be justified. How do we justify a belief? From the sophists of ancient Greece, to the post-modernists and the-anything-goes hippies of the 1960s, and all their ilk in between it has been demonstrated that what can be known for certain is vanishingly small.
Renee Descartes (1596 – 1960) argues in the beginning of his Discourse on the Method that all knowledge is subject to doubt: a process called methodological skepticism. To a large extend, he is correct. Then to get to something that is certain he came up with his famous statement: I think, therefore I am. For a long time this seemed to me like a sure argument. Hence, “I exist” seemed an incontrovertible fact. I then made the mistake of reading Nietzsche[1] (1844—1900). He criticizes the argument as presupposing the existence of “I” and “thinking” among other things. It has also been criticized by a number of other philosophers including Bertrand Russell (1872 – 1970). To quote the latter: Some care is needed in using Descartes’ argument. “I think, therefore I am” says rather more than is strictly certain. It might seem as though we are quite sure of being the same person to-day as we were yesterday, and this is no doubt true in some sense. But the real Self is as hard to arrive at as the real table, and does not seem to have that absolute, convincing certainty that belongs to particular experiences. Oh, well back to the drawing board.
The criteria for knowledge, as postulated by Plato, lead to knowledge either not existing or being of the most trivial kind. No belief can be absolutely justified and there is no way to tell for certain if any proposed truth is an incontrovertible fact. So where are we? If there are no incontrovertible facts we must deal with uncertainty. In science we make a virtue of this necessity. We start with observations, but unlike the logical positivists we do not assume they are reality or correspond to any ultimate reality. Thus following Immanuel Kant (1724 – 1804) we distinguish the thing-in-itself from its appearances. All we have access to are the appearances. The thing-in-itself is forever hidden.
But all is not lost. We make models to describe past observations. This is relatively easy to do. We then test our models by making testable predictions for future observations. Models are judged by their track record in making correct predictions–the more striking the prediction the better. The standard model of particle physics prediction of the Higgs[2] boson is a prime example of science at its best. The standard model did not become a fact when the Higgs was discovered, rather its standing as a useful model was enhanced. It is the reliance on the track record of successful predictions that is the demarcation criteria for science and I would suggest the hallmark for defining knowledge. The scientific models and the observations they are based on are our only true knowledge. However, to mistake them for descriptions of the ultimate reality or the thing-in-itself would be folly, not knowledge.
[1] Reading Nietzsche is always a mistake. He was a madman.
[2] To be buzzword compliant, I mention the Higgs boson.
A l’occasion de l’ouverture de l’appel à candidature 2013 de “Sciences à l’Ecole” pour l’accueil d’enseignants français au CERN durant une semaine, nous publions ces jours-ci le journal quotidien plein d’humour de Jocelyn Etienne qui a suivi ce programme l’année dernière, au mois de novembre dernier.
Chambre à brouillard: la chasse aux particules commence !
Mardi 06 novembre 2012
On a beau être dans un des plus grands centre de recherche fondamentale du monde, rien de vaut un tableau noir et une craie (cette dernière difficile à trouver par ici parait-il).
Les conférences du jour :
David Rousseau (IN2P3 / LAL-Orsay) nous confirme la découverte presque peut-être sûre du boson de Higgs, en tout cas, si c’est pas lui, c’est quand même quelque chose. Il travaille sur le détecteur ATLAS, il doit savoir de quoi il parle. Il y a des détecteurs sur le LHC, comme ATLAS et CMS et chacun est un monstre de technologie et de compétences, et tous deux confirment indépendamment la détection du Higgs (c’est comme ça qu’on dit).
Julien Lesgourgues (Ecole Polytechnique Fédérale de Lausanne) nous parle de la courbure de l’espace qui en fait est plat, à moins que ce ne soit l’inverse, mais j’arrive un quart d’heure en retard…
Sylvie Rosier-Lees du CNRS/IN2P3 au laboratoire d’Annecy, s’occupe du détecteur spatial AMS (spectromètre magnétique Alpha ndlr), accroché à l’ISS. AMS s’occupe des particules cosmiques, et il y en a qui viennent de très loin ! (ici: les dernières new d’AMS ndlr).
A droite, la personne semblait coder un programme pour un traitement graphique de données, mais il basculait souvent sur son compte facebook… tsss tsss tsss… Pour les connaisseurs, son portable est sous Xubuntu.
Enfin, Corinne Berat du CNRS/IN2P3 au laboratoire de Grenoble a plus les pieds sur Terre. Son joujou se trouve en Argentine et détecte les rayons cosmiques (encore) qui arrivent au sol après avoir éclaboussé l’atmosphère d’une multitude de particules (des gerbes…). L’observatoire Pierre Auger recouvre quelque chose comme 3000 km² et se délecte des particules de haute énergie provenant peut être de collisions de galaxies ou de supernovae.
Après le repas du soir, je me rends à une conférence dans le cadre de « The 4th International Conference on Particle and Fundamental Physics in Space ». Aujourd’hui, William H. Gerstenmaier de la NASA qui nous présente in English, les recherches faites sur l’ISS. La vidéo finale (un film qui compile les plus belles vues de la Terre prises de la station) est absolument sublime.
Earth from Michael König – Même ceux qui ont bossé sur leur ordinateur (occupés à coder ou traiter les informations du LHC) toute la durée de la présentation sans écouter un mot du conférencier, stoppent leur activité pour regarder le film. on Vimeo.
A suivre…
Jocelyn Etienne est enseignant au lycée Feuillade de la ville de Lunel.
Pour soumettre sa candidature pour la prochaine session du stage au CERN, c’est par ici.
Revolutionary muon experiment to begin with 3,200-mile move of 50-foot-wide particle storage ring
This Fermilab press release came out on May 8. Read the original press release.
A model of the truck that will be used to transport the Muon g-2 ring, placed on a streetscape for scale. The truck will be escorted by police and other vehicles when it moves from Brookhaven National Laboratory in New York to a barge, and then from the barge to Fermi National Accelerator Laboratory in Illinois. Credit: Fermilab
Scientists from 26 institutions around the world are planning a new experiment that could open the doors to new realms of particle physics. But first, they have to bring the core of this experiment, a complex electromagnet that spans 50 feet in diameter, from the U.S. Department of Energy’s Brookhaven National Laboratory in New York to the DOE’s Fermi National Accelerator Laboratory in Illinois.
The experiment is called Muon g-2 (pronounced gee-minus-two), and will study the properties of muons, tiny subatomic particles that exist for only 2.2 millionths of a second. The core of the experiment is a machine built at Brookhaven in the 1990s, and the centerpiece of that machine is a circular electromagnet made of steel and aluminum, 50 feet wide, with superconducting cable inside.
“It costs about 10 times less to move the magnet from Brookhaven to Illinois than it would to build a new one,” said Lee Roberts of Boston University, spokesperson for the Muon g-2 experiment. “So that’s what we’re going to do. It’s an enormous effort from all sides, but it will be worth it.”
While most of the machine can be disassembled and brought to Fermilab in trucks, the massive electromagnet must be transported in one piece. It also cannot tilt or twist more than a few degrees, or the complex wiring inside will be irreparably damaged. The Muon g-2 team has devised a plan to make the 3,200-mile journey that involves loading the ring onto a specially prepared barge and bringing it down the East Coast, around the tip of Florida and up the Mississippi River to Illinois.
The ring is expected to leave New York in early June, and land in Illinois in late July. Once it arrives, the ring will be placed onto a truck built just for this purpose, and driven to Fermilab in Batavia, a suburb of Chicago. The land transport portions on both the New York and Illinois ends of the trip will occur at night—to minimize traffic delays—and the truck will only travel, at most, 10 miles per hour. On the New York end, the trip from Brookhaven Lab’s gate to the departure port should take one night. The complete trip from the Illinois port to Fermilab should take two consecutive nights.
“The transport of the ring from Brookhaven to Fermilab is a great example of the cooperation that exists between national laboratories,” said James Siegrist, associate director of science for high-energy physics with the U.S. Department of Energy. “The Muon g-2 experiment is an important component of the future of particle physics in the United States.”
Once at Fermilab, the storage ring will be used to hold muons created in the laboratory’s accelerators. Muons “wobble” when placed in a magnetic field, and based on what we know about the universe, scientists have predicted the exact value of that wobble. An experiment using the same machine at Brookhaven in the 1990s saw evidence for – though not definitive proof of – a departure from that expected value.
“Fermilab can generate a much more intense and pure beam of muons, so the Muon g-2 experiment should be able to close that margin of error,” said Chris Polly, project manager for Fermilab. “If we can do that, this experiment could indicate that there is exciting science awaiting beyond what we have observed.”
The experiment is scheduled to begin taking data in 2016.
“The ring is a wonder of scientific engineering,” said William Morse of Brookhaven. “We’re extremely proud of it, and excited to see it used in this next-generation experiment.”
The US high-energy physics community is planning the next two or three decades of its future. The process, called Snowmass, is a big deal for everyone interested in astro/particle physics, cosmology and related areas. That is especially important in these times of shrinking budgets and dire job prospects, which affect academic career paths of researchers worldwide — the folks at PhD Comics have a great take on this topic. Brilliant.
At Snowmass, the contribution of all segments of the community is necessary to ensure that its outcome truly reflects our views. The Snowmass Young Physicists group was formed to facilitate the participation of young people in this process. I am one of the organizers of this group and we are pursuing a Career and Science Aspirations Survey as an opportunity for everyone in our field to have their voices heard and help paint the big picture.
We are reaching out to people in all demographics: current, past and prospective students at the undergraduate and graduate levels; postdocs or former postdocs now working in other areas; and you, Quantum Diaries reader.
If you are part of our community, please take 10 minutes to respond the online survey. If you think this doesn’t apply to you, then please help us spread the news! The link is: http://tinyurl.com/snowmassyoung
The survey was launched in April and will be open until mid-July. Results will be published by the Snowmass Young team later this summer.
—Marcelle Soares-Santos
A l’occasion de l’ouverture de l’appel à candidature 2013 de “Sciences à l’Ecole” pour l’accueil d’enseignants français au CERN durant une semaine, nous publions ces jours-ci le journal quotidien plein d’humour de Jocelyn Etienne qui a suivi ce programme l’année dernière, au mois de novembre dernier.
Immersion au pays des particules
Lundi 05 novembre 2012
C’est moi ou la pièce de 5 francs est énorme ?
Grosse journée, petit déjeuner au restaurant du CERN, bon café, tartine beurrée confiturée pour 1 franc suisse ! A tester. Tiens d’ailleurs, c’est moi ou la pièce de 5 francs est énorme ?
L’hôtel-foyer du CERN
Il ne pleut pas ce matin (ça ne va pas durer, la promenade post-déjeuner s’est faite sous la pluie) alors j’en profite pour prendre une photo de l’hôtel-foyer qui m’héberge. C’est une des fenêtres du 1er étage derrière laquelle se trouve ma chambre, mais inutile de zoomer pour chercher à m’apercevoir. Qui prend la photo à votre avis ?
Daniel Denegri aurait peut-être vu le boson de Higgs…
Après une première présentation de l’in2p3 par Arnaud Marsollier, suivi de Mick Storr pour le CERN, c’est Daniel Denegri qui nous présente l’expérience CMS, incroyable projet de détection de particule qui s’étend sur 20 ans. Denegri lui-même est un brillant chercheur croate qui parle parfaitement le français, l’anglais entre autres, il aurait peut-être vu le boson de Higgs qui semble plus facile à détecter que son bras droit, tellement le bonhomme est énergique. L’après-midi, c’est au tour de Simone Gilardoni, théoricien des « accélérateurs collisionneurs » de nous montrer que les prouesses nécessaires pour maintenir un faisceau de protons dans un tube de 27 km de long, ne sont pas à la portée des bricoleurs du dimanche. Ou devrais-je dire 2 faisceaux dans 2 tubes qui se croisent de temps en temps ?…
Simone Gilardoni, théoricien des “accélérateurs collisionneurs”
Le petit point visible derrière Simone est visible ici en direct, si le LHC n’est pas à l’arrêt. Il y en a même deux, comme je l’ai dit précédemment ; nos deux faisceaux de protons dont on contrôle l’état notamment par des miroirs qui renvoient le rayonnement qu’il diffuse… enfin, c’est ce que j’ai compris…
D’ailleurs le LHC va bientôt être arrêté pour quelques mois (il est actuellement arrêté, ndlr, voir ici pourquoi en vidéo). J’espère que ce n’est pas lié à ce bouton sur lequel j’ai appuyé en pensant que c’était l’éclairage de ma salle de bains. Il reprendra ensuite de plus belle pour tenter d’atteindre les 13-14 TeV contre 7 TeV actuellement. Je sais, ça fait beaucoup…
L’après –midi se poursuit par une présentation des masterclasses par Nicolas Arnaud, chercheur à Orsay et organisateur de notre French Teacher Programme au CERN. Puis il nous initie à la détection de particules à l’aide d’un logiciel et de vraies mesures.
Atelier “masterclasses”: J’ai trouvé les W qui se désintègrent, donc j’ai le droit de prendre une photo de mes collègues en plein effort.
Pour finir, je me rends à une conférence tardive sur les sondes Voyager 1 et 2 donnée par Edward Stone, responsable scientifique de ces sondes depuis 1972.
Sur le chemin, j’immortalise la version suisse du principe de superposition d’état, ou comment un vélo peut être en deux endroits différents au même moment…
A suivre…
Jocelyn Etienne est enseignant au lycée Feuillade de la ville de Lunel.
Pour soumettre sa candidature pour la prochaine session du stage au CERN, c’est par ici.
Principe de superposition d’état…
…ou comment un vélo peut être en deux endroits au même moment !
This article originally appeared in Fermilab Today on April 26, 2013.
Images from the Dark Energy Camera before (left) and after (right) a supernova explosion in a galaxy about 2 billion light-years away.
The Dark Energy Survey (DES) collaboration has captured images of 176 star explosions, called supernovae, including 16 that occurred farther than 7 billion light-years away and when the universe was only about half as old as it is today. A new type of CCD detector contained in the Dark Energy Camera enabled identification of the distant supernovae, making DECam about 10 times more sensitive than other optical cameras to the long-wavelength (red and near-infrared) light coming from these very distant explosions. This improved sensitivity will allow the DES collaboration to find more supernovae from this period in the history of the universe than any other project.
Our current understanding is that the universe is made up of about 70 percent dark energy and that this dark energy is causing the universe to expand at an accelerating rate. Measuring Type 1a supernovae is a way to study dark energy. The fainter the observed explosion, the further away it is, similar to the difference in brightness between nearby and distant candles. As the light of the explosion travels to us, it is stretched by the expansion of the universe and becomes redder. By combining the measured brightness and information about how much the light is stretched, cosmologists can calculate the expansion rate of the universe.
The Dark Energy Survey collaboration includes scientists, postdocs and graduate students from around the world, who worked together to build the camera, collect the images and identify the supernovae described in this result.
The amount and wavelength of a supernova’s light determines its age and type. Researchers use filters that divide optical light into four separate parts, with each filter allowing only certain wavelengths to pass through. We know these 16 supernovae are about 7 billion light-years away because most of the light was observed with the filter that allowed only the reddest light to pass through and be measured by the special red-sensitive detectors in the camera. Less sensitive cameras require time-consuming follow-up observations to determine the supernova age.
To search for supernovae, the DES observers take images of the same patch of sky every four to seven days. Then they subtract the images from each other and search for differences. Computers and teams of people looked at thousands of sets of DECam images to find the 176 candidate supernovae. So far five of the candidates have been followed up, and all five were confirmed to be type 1a supernovae.
The Dark Energy Survey will measure more than 3,000 type-1a supernovae in the next five years and provide new information about the mysterious nature of dark energy. For more information, see the Dark Energy Survey website.
–Brenna Flaugher
