Vue plongeante sur le but de Philae 2020-10-0714_16:46:51 +0200
07 Oct 2014 04:46 pm | Anonymous
07/10/2014 - Philippe Henarejos
La sonde Rosetta continue de tourner autour de la comète Churyumov-Gerasimenko et de la mitrailler de photos. Cette image résulte de l'addition de 4 de ces photos prises le 30 septembre 2014 par la caméra de navigation alors que l'engin automatique n'était qu'à 18,1 km du noyau cométaire. Assemblées par Jean-Luc Dauvergne, de Ciel et Espace, l'image offre une vue plongeante sur le site J, qui a été sélectionné comme cible du petit module Philae. Une animation du modèle 3D de la comète permet de localiser précisément ce site. La résolution de 1,4 m permet de discerner les petits accidents du terrain et de constater que l'endroit choisi semble assez dégagé. En tout cas, il n...
Une approche darwinienne du cancer 2020-10-0714_16:20:58 +0200
07 Oct 2014 04:20 pm | Anonymous
Et si les lois de l'évolution établies par Darwin il y a 150 ans permettaient de poser un nouveau regard sur le cancer ? Explorée par des chercheurs, cette piste pourrait aboutir à de nouvelles approches thérapeutiques.
Liveblog: New ATLAS Higgs Results 2020-10-0714_08:44:45 +0000
07 Oct 2014 10:44 am | Anonymous
In a short while, starting at 11:00 CEST / 10:00 BST, ATLAS will announce some new Higgs results:
“New Higgs physics results from the ATLAS experiment using the full Run-1 LHC dataset, corresponding to an integrated luminosity of approximately 25 fb-1, of proton-proton collisions at 7 TeV and 8 TeV, will be presented.” [seminar link]
I don’t expect anything earth-shattering, because ATLAS already has preliminary analyses for all the major Higgs channels. They have also submitted final publications for LHC Run I on Higgs decaying to two photons, two b quarks, two Z bosons – so it’s reasonable to guess that Higgs decaying to taus or W’s is going to be covered today.
(Parenthetically, CMS has already published final results for all of the major Higgs decays, because we are faster, stronger, smarter, better looking, and more fun at parties.)
I know folks on ATLAS who are working on things that might be shown today, and they promise they have some new tricks, so I’m hoping things will be fairly interesting. But again, nothing earth-shattering.
I’ll update this very page during the seminar. You should also be able to watch it on the Webcast Service. 10:55 I have a front row seat in the CERN Council Chamber, which is smaller than the main auditorium that you might be more familiar with. Looks like it will be very, very full. 11:00 Here we go! (Now’s a good time to click the webcast, if you plan to.) 11:03 Yes, it turns out it will be taus and W’s. 11:06 As an entree, look how fabulously successful the Standard Model, including the Higgs, has been:
11:10 Good overview right now over overall Higgs production and decay and the framework we used to understand it. Have any questions I can answer during the seminar? Put them in the comments or write something at me on Twitter. 11:18 We’re learning about the already-released results for Higgs to photons and ZZ first. 11:24 Higgs to bb, the channel I worked on for CMS during Run I. These ATLAS results are quite new and have a lot of nice improvements from their preliminary analysis. Very pretty plot of improved Higgs mass resolution when corrections are made for muons produced inside b-jets. 11:30 Now to Higgs to tau tau, a new result! 11:35 Developments since preliminary analysis include detailed validation of techniques for estimating from data how isolated the taus should be from other things in the detector. 11:36 I hope that doesn’t sound too boring, but this stuff’s important. It’s what we do all day, not just counting sigmas. 11:37 4.5 sigma evidence (only 3.5 expected) for the Higgs coupling to the tau lepton! 11:39 Their signal is a bit bigger than the SM predicts, but still very consistent with it. And now on to WW, also new. 11:41 In other news, the Nobel Prize in Physics will be announced in 4 minutes: It’s very unlikely to be for anything in this talk. 11:44 Fixed last comment: “likely” –> “unlikely”. Heh. 11:48 When the W’s decay to a lepton and an invisible neutrino, you can’t measure a “Higgs peak” like we do when it decays to photons or Z’s. So you have to do very careful work to make sure that a misunderstanding of you background (i.e. non-Higgs processes) produces what looks like a Higgs signal. 11:50 Background-subtracted result does show a clear Higgs excess over the SM backgrounds. This will be a pretty strong result. 11:51 6.1 sigma for H –> WW –> lvlv. 3.2 sigma for VBF production mechanism. Very consistent with the SM again. 11:52 Lots of very nice, detailed work here. But the universe has no surprises for us today. 11:54 We can still look forward to the final ATLAS combination of all Higgs channels, but we know it’s going to look an awful lot like the Standard Model. Congratulations to my ATLAS colleagues on their hard work. 11:56 By the way, you can read the slides on the seminar link. 12:02 The most significant result here might actually be the single-channel observation of the Vector Boson Fusion production mechanism. The Higgs boson really is behaving the way the Standard Model says it should! Signing off here, time for lunch
Découvrez le ciel du mois d'octobre 2020-10-0714_10:25:00 +0200
07 Oct 2014 10:25 am | la rédaction de Futura-Sciences
Après un été maussade, voici la rentrée. En espérant que la météo soit plus coopérative, vous pourrez observer 3 maxima de météores, un coucher de Lune dans l'axe de l'Arc de Triomphe, la lumière zodiacale, Vénus en rapprochement avec Régulus, Mars qui flirte avec Antarès, et l'arrivée de...
Des panneaux solaires auto-refroidissants 2020-10-0714_06:10:00 +0000
07 Oct 2014 08:10 am | Anonymous
Des chercheurs de la prestigieuse Université de Stanford ont mis au point un nouveau type révolutionnaire de cellules solaires qui ont une capacité unique de refroidissement et peuvent donc capter plus d'énergie, plus longtemps.
Une puce radio fonctionnant sans batterie… 2020-10-0714_06:05:00 +0000
07 Oct 2014 08:05 am | Anonymous
Un ingénieur de Stanford, Amin Arbabian, a présenté une puce radio aussi petite qu'une fourmi et surtout capable de fonctionner sans aucune source d'énergie directe puisque le champ électromagnétique ambiant suffit à alimenter ce composant.
A terme, ces puces sans batterie pourraient révolutionner l'Internet des objets (ou objets connectés). Alimentée par une simple pile AAA, la puce d'Amin Arbabian serait capable d'émettre pendant plus de 100 ans. Mais pour l'instant, cette technologie se limite aux puces radio permettant des transferts limités d'informations.
Un manteau communicant pour suivre ses enfants à la trace ! 2020-10-0714_06:00:00 +0000
07 Oct 2014 08:00 am | Anonymous
La marque de vêtements Gémo vient de lancer un manteau, vendu 99 euros, pour enfant avec puce intégrée. Ce "manteau communicant" sera proposé aux filles ou garçons, de 3 à 10 ans, équipé d'un petit boîtier-balise accroché à l'intérieur par un anneau. Gemo précise que ce dispositif « permettra de rassurer les parents sur le trajet de leurs enfants, quand ils vont à l'école, faire du sport, participent à des sorties ou sont invités à un anniversaire ».
Blessé par arme... transfusé... et refroidi ! 2020-10-0714_00:00:00 +0200
07 Oct 2014 12:00 am | firstname.lastname@example.org (Damien)
Bien loin de nous l'idée de souhaiter qu'un fidèle omnilogiste(1) soit un jour blessé par arme à feu ou arme blanche !
Divers articles de cet excellent site ont déjà étudié le déroulement de la dégradation de l'état de santé dû à un tel acte condamnable.
Mais soyons plus positif et parlons ici thérapie !
Une nouvelle méthode espérée être révolutionnaire est en train de faire son apparition outre Atlantique : Il s'agit de l' « Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma » (EPR CAT), sous la direction du Dr Sam Tisherman de l'hôpital presbytérien de Pittsburgh.
L'idée ? Ralentir grâce au froid le métabolisme du corps humain afin de préserver le système nerveux à la suite d'un arrêt cardiaque associé à une hémorragie importante ayant entrainée une grande perte de sang.
Voici la « recette » : dans des conditions d'asepsie draconiennes, vider le blessé de l'intégralité de son sang, introduire par l'aorte 5 ou 6 litres de solution saline. Maintenir la température à 10 ℃.
« Hibernatus » consomme ainsi beaucoup moins d'oxygène dans ses organes, tous mis en état végétatif.
L'opération effectuée, remonter progressivement la température de la mixture en réintroduisant le sang précédemment récupéré et maintenir l'ensemble jusqu'à 37 ℃.
Pour le moment, seules les expériences menées sur des porcs ont validé cette méthode (encore qu'il était constaté sur les champs de bataille napoléonien de l'est que les blessés sur terrain très froids décédaient moins que les autres). Taux de survie chez les porcs sur lesquels est testée la méthode : 90 %, avec peu ou pas de séquelles neurologiques, alors que le taux était de… 0 % chez leurs compères à température ambiante.
Reste à passer à la pratique, avec un problème éthique majeur : pour valider la recherche, il faut appliquer l'un et l'autre des protocoles à des victimes, avec des risques évidents dans les deux cas. Comment choisir les « cobayes » aux urgences ?
Mais la décision d'essai clinique est bien validée par les autorités dans ce pays où les blessés par balle sont malheureusement nombreux !
With construction completed, the NOvA experiment has begun its probe into the mysteries of ghostly particles that may hold the key to understanding the universe. Image: Fermilab/Sandbox Studio
It's the most powerful accelerator-based neutrino experiment ever built in the United States, and the longest-distance one in the world. It's called NOvA, and after nearly five years of construction, scientists are now using the two massive detectors – placed 500 miles apart – to study one of nature's most elusive subatomic particles.
Scientists believe that a better understanding of neutrinos, one of the most abundant and difficult-to-study particles, may lead to a clearer picture of the origins of matter and the inner workings of the universe. Using the world's most powerful beam of neutrinos, generated at the U.S. Department of Energy's Fermi National Accelerator Laboratory near Chicago, the NOvA experiment can precisely record the telltale traces of those rare instances when one of these ghostly particles interacts with matter.
Construction on NOvA's two massive neutrino detectors began in 2009. In September, the Department of Energy officially proclaimed construction of the experiment completed, on schedule and under budget.
"Congratulations to the NOvA collaboration for successfully completing the construction phase of this important and exciting experiment," said James Siegrist, DOE associate director of science for high energy physics. "With every neutrino interaction recorded, we learn more about these particles and their role in shaping our universe."
NOvA's particle detectors were both constructed in the path of the neutrino beam sent from Fermilab in Batavia, Illinois, to northern Minnesota. The 300-ton near detector, installed underground at the laboratory, observes the neutrinos as they embark on their near-light-speed journey through the Earth, with no tunnel needed. The 14,000-ton far detector — constructed in Ash River, Minnesota, near the Canadian border – spots those neutrinos after their 500-mile trip and allows scientists to analyze how they change over that long distance.
For the next six years, Fermilab will send tens of thousands of billions of neutrinos every second in a beam aimed at both detectors, and scientists expect to catch only a few each day in the far detector, so rarely do neutrinos interact with matter.
From this data, scientists hope to learn more about how and why neutrinos change between one type and another. The three types, called flavors, are the muon, electron and tau neutrino. Over longer distances, neutrinos can flip between these flavors. NOvA is specifically designed to study muon neutrinos changing into electron neutrinos. Unraveling this mystery may help scientists understand why the universe is composed of matter and why that matter was not annihilated by antimatter after the big bang.
Scientists will also probe the still-unknown masses of the three types of neutrinos in an attempt to determine which is the heaviest.
"Neutrino research is one of the cornerstones of Fermilab's future and an important part of the worldwide particle physics program," said Fermilab Director Nigel Lockyer. "We're proud of the NOvA team for completing the construction of this world-class experiment, and we're looking forward to seeing the first results in 2015."
The far detector in Minnesota is believed to be the largest free-standing plastic structure in the world, at 200 feet long, 50 feet high and 50 feet wide. Both detectors are constructed from PVC and filled with a scintillating liquid that gives off light when a neutrino interacts with it. Fiber optic cables transmit that light to a data acquisition system, which creates 3-D pictures of those interactions for scientists to analyze.
The NOvA far detector in Ash River saw its first long-distance neutrinos in November 2013. The far detector is operated by the University of Minnesota under an agreement with Fermilab, and students at the university were employed to manufacture the component parts of both detectors.
"Building the NOvA detectors was a wide-ranging effort that involved hundreds of people in several countries," said Gary Feldman, co-spokesperson of the NOvA experiment. "To see the construction completed and the operations phase beginning is a victory for all of us and a testament to the hard work of the entire collaboration."
The NOvA collaboration comprises 208 scientists from 38 institutions in the United States, Brazil, the Czech Republic, Greece, India, Russia and the United Kingdom. The experiment receives funding from the U.S. Department of Energy, the National Science Foundation and other funding agencies.
For more information, visit the experiment's website: http://www-nova.fnal.gov. Note: NOvA stands for NuMI Off-Axis Electron Neutrino Appearance. NuMI is itself an acronym, standing for Neutrinos from the Main Injector, Fermilab's flagship accelerator.
Fermilab is America's premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab's website at www.fnal.gov and follow us on Twitter at @FermilabToday.
The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
Theoretical high energy, nuclear, gravitational physics and/or cosmology - Senior at Massachusetts U., Amherst 2020-10-0614_18:24:57 +0000
06 Oct 2014 08:24 pm | Anonymous
Field of Interest:gr-qc, hep-lat, hep-ph, hep-th, nucl-th Deadline: 2014-12-01 Region: North America
The Physics Department of the University of Massachusetts Amherst invites applications for a tenure-track faculty position in theoretical high energy, nuclear, gravitational physics and/or theoretical cosmology to start September 1, 2015. The new faculty member will be part of the recently established Amherst Center for Fundamental Interactions, http://www.physics.umass.edu/acfi/.
Further information about the Department's theoretical and experimental efforts can be found at http://www.physics.umass.edu/.
The Department seeks an individual with outstanding research and a strong commitment to teaching. A PhD in areas closely related to theoretical high energy, nuclear, gravitational physics and/or theoretical cosmology, and postdoctoral experience are required. We are seeking talented applicants qualified for an assistant or associate professor position. Under exceptional circumstances, highly qualified candidates at the rank of full professor may receive consideration.
The university is committed to active recruitment of a diverse faculty and student body. The University of Massachusetts Amherst is an Affirmative Action/Equal Opportunity Employer of women, minorities, protected veterans, and individuals with disabilities and encourages applications from these and other protected group members. Because broad diversity is essential to an inclusive climate and critical to the University’s goals of achieving excellence in all areas, we will holistically assess the many qualifications of each applicant and favorably consider an individual’s record working with students and colleagues with broadly diverse perspectives, experiences, and backgrounds in educational, research or other work activities. We will also favorably consider experience overcoming or helping others overcome barriers to an academic degree and career
Premier bilan du programme de clusters de pointe en Allemagne (Politique d'innovation) 6 10 2014 17:02 +0100
06 Oct 2014 06:02 pm | email@example.com (BE Allemagne)
Les clusters de pointe (Spitzencluster) jouent un rôle moteur dans le développement économique et l'essor de la recherche et de l'innovation en Allemagne. Ce constat est dressé par une étude de l'Institut de recherche économique de Rhénanie du Nord-W...
IFA 2014, grand rendez-vous de l'électronique grand public (TIC) 6 10 2014 16:50 +0100
06 Oct 2014 05:50 pm | firstname.lastname@example.org (BE Allemagne)
Le salon de l'électronique IFA (Internationale Funkausstellung Berlin), s'est tenu à Berlin du 5 au 10 septembre 2014. Les montres connectées, écrans incurvés, smart home et une nouvelle génération de smartphones ont été à l'honneur cette année. Cet ...
Mother's behavior has strong effect on cocaine-exposed children 2020-10-0614_11:38:34 EDT
06 Oct 2014 05:38 pm | Anonymous
It is not only prenatal drug exposure, but also conditions related to drug use that can influence negative behavior in children, according to a new study. Maternal harshness, such as threats of physical discipline, can be influenced by drug use. Animal studies have shown that prenatal cocaine use can affect parenting by lowering the bonding hormones mothers usually experience after birth, resulting in less emotional engagement with the child.,
Teaming up on top and Higgs 2020-10-0614_15:16:59 +0000
06 Oct 2014 05:16 pm | Anonymous
While the LHC experiments are surely turning their attention towards the 2015 run of the collider, at an energy nearly double that of the previous run, we’re also busy trying to finalize and publish measurements using the data that we already have in the can. Some measurements just take longer than others, and some it took us a while to get to. And while I don’t like tooting my own horn too much here at the US LHC blog, I wanted to discuss a new result from CMS that I have been working on with a student, Dan Knowlton, here at the University of Nebraska-Lincoln, along with collaborators from a number of other institutions. It’s been in the works for so long that I’m thrilled to get it out to the public!
(This is one of many CMS results that were shown for the first time last week at the TOP 2014 conference. If you look through the conference presentations, you’ll find that the top quark, which has been around for about twenty years now, has continued to be a very interesting topic of study, with implications for searches for new physics and even for the fate of the universe. One result that’s particularly interesting is a new average of CMS top-quark mass measurements, which is now the most accurate measurement of that quantity in the world.)
The LHC experiments have studied the Higgs boson through many different Higgs decay modes, and many different production mechanisms also. Here is a plot of the expected cross sections for different Higgs production mechanisms as a function of Higgs mass; of course we know now that the Higgs has a mass of 125 GeV:
The most common production mechanism has a Higgs being produced with nothing else, but it can also be produced in association with other particles. In our new result, we search for a Higgs production mechanism that is so much more rare that it doesn’t even appear on the above plot! The mechanism is the production of a Higgs boson in association with a single top quark, and in the standard model, the cross section is expected to be 0.018 pb, about an order of magnitude below the cross section for Higgs production in association with a top-antitop pair. Why even bother to look for such a thing, given how rare it is?
The answer lies in the reason for why this process is so rare. There are actually two ways for this particular final state to be produced. Here are the Feynman diagrams for them:
In one case, the Higgs is radiated off the virtual W, while in the other it comes off the real final-state top quark. Now, this is quantum mechanics: if you have two different ways to connect an initial and final state, you have to add the two amplitudes together before you square them to get a probability for the process. It just so happens that these two amplitudes largely destructively interfere, and thus the production cross section is quite small. There isn’t anything deep at work (e.g. no symmetries that suppress this process), it’s just how it comes out.
At least, that’s how it comes out in the standard model. We assume certain values for the coupling factors of the Higgs to the top and W particles that appear in the diagrams above. Other measurements of Higgs properties certainly suggest that the coupling factors do have the expected values, but there is room within the constraints for deviations. It’s even possible that one of the two coupling values has the exact opposite sign from what we expect. In that case, the destructive interference between the two amplitudes would become constructive, and the cross section would be almost a factor of 13 larger than expected!
The new result from CMS is a search for this anomalous production of the Higgs in association with a single top quark. CMS already has a result for a search in which the Higgs decays to pair of photons; this new result describes a search in which the Higgs decays to bottom quarks. That is a much more common Higgs decay mode, so there ought to be more events to see, but at the same time the backgrounds are much higher. The production of a top-antitop pair along with an extra jet of hadrons that is mis-identified as arising from a bottom quark looks very much like the targeted Higgs production mechanism. The top-antitop cross section is about 1000 times bigger than that of the anomalous production mechanism that we are looking for, and thus even a tiny bottom mis-identification rate leads to a huge number of background events. A lot of the work in the data analysis goes into figuring out how to distinguish the (putative) signal events from the dominant background, and then verifying that the estimations of the background rates are correct.
The analysis is so challenging that we predicted that even by throwing everything we had at it, the best we could expect to do was to exclude the anomalous Higgs production process at a level of about five times the predicted rate for it. When we looked at the data, we found that we could exclude it at about seven times the anomalous rate, roughly in line with what we expected. In short, we do not see an anomalous rate for anomalous Higgs production! But we are able to set a fairly tight limit, at around 1.8 pb.
What do I like about this measurement? First, it’s a very different way to try to measure the properties of the Higgs boson. The measurements we have are very impressive given the amount of data that we have so far, but they are not very constraining, and there is enough wiggle room for some strange stuff to be going on. This is one of the few ways to probe the Higgs couplings through the interference of two processes, rather than just through the rate for one dominant process. All of these Higgs properties measurements are going to be much more accurate in next year’s data run, when we expect to integrate more data and all of the production rates will be larger due to the increase in beam energy. (For this anomalous production process, the cross section will increase by about a factor of four.) In this particular case, we should be able to exclude anomalous Higgs couplings through this measurement…or, if nature surprises us, we will actually observe them! There is a lot of fun ahead for Higgs physics (and top physics) at the LHC.
I’ve also really enjoyed working with my CMS colleagues on this project. Any measurement coming out of the experiment is truly the work of thousands of people who have built and operated the detector, gotten the data recorded and processed, developed and refined the reconstruction algorithms, and defined the baselines for how we identify all kinds of particles that are produced in the proton collisions. But the final stages of any measurement are carried out by smaller groups of people, and in this case we worked with colleagues from the Catholic University of Louvain in Belgium, the Karlsruhe Institute of Technology in Germany, the University of Malaya in Malaysia, and the University of Kansas (in Kansas). We relied on the efforts of a strong group of graduate students with the assistance of harried senior physicists like myself, and the whole team did a great job of supporting each other and stepping up to solve problems as they arose. These team efforts are one of the things that I’m proud of in particle physics, and that make our scientists so successful in the wider world.
How cosmic rays help us understand the universe (Video: Veronica Bindi/TEDed)
How cosmic rays help us understand the universe is the first video in a series of three, short physics-related lessons created by TED-ED and CERN for the TEDxCERN event held on 25 September 2014. In this video, Veronica Bindi – AMS physicist at CERN – takes us on a journey through space to understand where cosmic rays come from and how they act as space messengers by bringing us physical data from parts of the cosmos beyond our reach. Read more about making this video on this TEDed blog
Stayed tuned for the next video in this series later this week.
For more info on this years event see http://tedxcern.ch where the videos for this year's talks will soon be available.