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CERN: The MoEDAL Experiment
The Monopole and Exotics Detector at the LHC (MoE...
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CERN: The MoEDAL Experiment
The Monopole and Exotics Detector at the LHC (MoEDAL) was the seventh detector to be approved by the LHC Management board. It will share the cavern at Point 8 with LHCb and will search for the massive stable (or pseudo-stable) particles, such as magnetic monopoles or dyons, produced at the LHC.
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AIMS OF THE MoEDAL EXPERIMENT
In 2010 the LHC opened up a new energy regime in which we can search for new physics beyond the Standard Model. The search strategy for exotics planned for the main LHC detectors can be extended with dedicated experiments designed to enhance, in a complementary way, the physics reach of the LHC.
The MoEDAL (Monopole and Exotics Detector at the LHC) project is such an experiment. The prime motivation of MoEDAL is to directly search for the Magnetic Monopole or Dyon and other highly ionizing Stable (or pseudo-stable) Massive Particles (SMPs) at the LHC.
MoEDAL Nuclear Track Detectors (NTDs) will be able to record the tracks of highly ionizing particles with magnetic/electric charges greater than 3gD (≡ 206e), the detection of even one magnetic monopole or dyon that fully penetrated a MoEDAL NTD stack is expected to be distinctive.
Another important area of physics beyond the Standard Model that can be addressed by MoEDAL is the existence of SMPs with single electrical charge which provide a second category of particle that is heavily ionizing by virtue of its small speed. The most obvious possibility for an SMP is that one or more new states exist which carry a new conserved, or almost conserved, global quantum number.
For example, SUSY with R-parity, extra dimensions with KK-parity, and several other models fall into this category. The lightest of the new states will be stable, due to the conservation of this new parity, and depending on quantum numbers, mass spectra, and interaction strengths, one or more higher-lying states may also be stable or meta-stable.
The third class of SMP which could be accessed by MoEDAL has multiple electric charge such as the black hole remnant, or long-lived doubly charged Higgs bosons. SMPs with magnetic charge, single or multiple electric charge and with Z/β (β=v/c) as low as five can, in principle, be detected by the CR39 nuclear track detectors, putting them within the physics reach of MoEDAL.
THE MoEDAL DETECTOR
The MoEDAL detector is comprised of an array of plastic Nuclear Track Detectors (NTDs) deployed around the (Point-8) intersection region of the LHCb detector, in the VELO (VErtex LOcator) cavern. The array consists of NTD stacks, ten layers deep, in Aluminium housings attached to the walls and ceiling of the VELO cavern.
The maximum possible surface area available for detectors is around 25 m2, although the final deployed area could be somewhat less due to the developing requirements of the infrastructure of the LHCb detector. A more detailed description of the MoEDAL detectors and the track-etch detector technology, can be found in the MoEDAL TDR
When a charged particle crosses a plastic nuclear track detector it produces damages at the level of polymeric bounds in a small cylindrical region around its trajectory forming he so-called latent track. The damage produced is dependent on the energy released inside the cylindrical region i.e. the Restricted Energy Loss (REL) which is a function of the charge Z and β=v/c (c the velocity of light in vacuum) of the incident highly ionizing particle (ion).
The subsequent etching of the solid nuclear detectors leads to the formation of etch-pit cones. These conical pits are usually of micrometer dimensions and can be observed with an optical microscope. Their size and shape yield information about charge, energy and direction of motion of the incident ion.
• http://web.me.com/jamespinfold/MoEDAL...
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Produced by: CERN Video Productions
Director: CERN Video Productions
© CERN 2010
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Best0fScience uploaded a new video
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Hubblecast 43: Hubble and Black Holes.
For centuries, scientists imagined ob...
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Hubblecast 43: Hubble and Black Holes.
For centuries, scientists imagined objects so heavy and dense that their gravity might be strong enough to pull anything in - including light. They would be, quite literally, a black hole in space. But it's only in the past few decades that astronomers have conclusively proved their existence.
Today, Hubble lets scientists measure the effects of black holes, make images of their surroundings and glean fascinating insights into the evolution of our cosmos.
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In science fiction, black holes are often portrayed as some kind of menacing threat to the safety of the whole Universe, like giant vacuum cleaners that suck up all of existence.
Now, in this episode, we're going to separate the fiction from the facts and we're going to look at the real science behind black holes and how Hubble has contributed to it.
Black holes come in different sizes. We've had solid evidence for the smaller ones since the 1970s. These form when a huge star explodes at the end of its life.
As the outer layers are blown away, the star's core collapses in on itself forming an incredibly dense ball. For instance, a black hole with the same mass as the Sun would have a radius of only a few kilometres.
These black holes won't suck you in unless you get very close to them though. In fact, contrary to popular belief, a black hole the size of the Sun doesn't actually exert any more gravitational pull than the Sun does. But these stellar black holes are just part of the story.
Before Hubble was launched, astronomers had noticed that the centres of many galaxies were somehow much denser and brighter than they were expected to be. And so they speculated that there must be some kind of huge, massive objects lurking in the centres of these galaxies in order to provide the additional gravitational attraction.
Now, could these objects be supermassive black holes, that is, black holes which are millions or even billions of times more massive than the stellar ones? Or was there perhaps a simpler, less exotic explanation, like giant star clusters?
Frustratingly, at that time, telescopes just weren't quite powerful enough to see enough detail to solve the mystery. Fortunately, Hubble was on its way, along with a range of other high-tech telescopes. When the space telescope was being planned, the search for supermassive black holes was in fact one of its main objectives.
Some of Hubble's early observations in the 1990s were dedicated to these dense, bright galactic centres. Where ground-based telescopes were just seeing a sea of stars, Hubble was able to resolve the details. In fact, around the very centres of these galaxies, Hubble discovered rotating discs of gas and dust.
When Hubble observed the disc at the centre of a nearby galaxy, Messier 87, the astronomers saw that its colour was not quite the same on both sides. One side was shifted towards blue and the other towards red, and this told the
scientists that it must have been rotating very quickly. This is because the wavelength of light is changed by the motion of an object emitting it. Think about how the pitch of an ambulance siren drops as it drives past you, because the sound waves are more spaced out as the vehicle moves away.
Similarly, if an object is moving towards you, the light's wavelength is squashed, making it bluer; if it's moving away, it's stretched, making it redder. This is also known as the Doppler effect. So, by measuring how much the colours had shifted on either side of the disk, astronomers were able to determine its speed of rotation. And it turned out that this disk was spinning at a rate of hundreds of kilometres per second.
This in turn allowed astronomers to deduce that, hidden at the very centre, there must be some kind of object which was two to three billion times the mass of our Sun — and this was very likely a supermassive black hole. Now, along with a lot of other observations, this was a key piece of evidence that led to the notion that there is a supermassive black hole lurking at the centre of most, if not all, giant galaxies, including our own Milky Way.
So far, so good. But this work was almost 20 years ago — what does it tell us about cutting-edge science today? Well, the science of black holes has moved along a lot since then. The mystery now isn't whether they exist, but why they behave in the strange ways they do.
For example, Hubble observations have helped to show that the mass of a black hole is closely related to the mass of its surrounding host galaxy. The bigger the black hole, the bigger the galaxy. Now the reason for this is totally unclear.
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Best0fScience uploaded a new video
(3 months ago)
Hubblecast 42: Hubble's Greatest Hits.
What makes a scientific discovery really important? It's partly down to how much scientists use the discovery...
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Hubblecast 42: Hubble's Greatest Hits.
What makes a scientific discovery really important? It's partly down to how much scientists use the discovery in subsequent work — but it's also partly down to what inspires their imagination. In this episode, the Hubblecast talks to some leading astronomers about their favourite Hubble discovery.
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How do we know if a scientific discovery is really important, or somehow special?
Well, when astronomers obtain a result, they usually write it up in an article for a scientific journal. And one way to know whether the result is important or not is to look at how often other astronomers refer to this article in their work.
That's the simple answer anyway. But there's a human component too. Some results simply capture our imagination more than others, and that too is an important part of what makes a truly great discovery.
In this episode, we're going to be talking to some leading astronomers who use the Hubble Space Telescope, and we're going to ask them about their favourite Hubble moments.
Joe Liske: "There's so many discoveries that Hubble has made. Some that we knew we would make such as measuring the speed of the expansion of the Universe, verifying the existence of black holes, and then there's some that were completely unexpected. In fact, my favourite I think is one that when Hubble was launched, we didn't know about any extrasolar planets. So my favourite Hubble discovery if you will, is the measurement of the atmosphere of a planet around a nearby star, that was made by the STIS instrument. I think it really boggles the mind, or stimulates the imagination to think that here on Earth with a telescope in orbit, we can actually spy on other planets in other solar systems."
Bob O'Dell: "My favourite Hubble discovery is of course one of my own! It was a surprise that should not have been a surprise. When we first looked at the Orion nebula, this region of nearby star formation, we found that we could actually see protoplanetary discs around many of the stars. Now, we should have expected to see this, we should have been looking for it, but we were looking for something else and found that. It was a wonderful feeling, to discover the protoplanetary disc. It was the closest thing to a 'heureka' moment that I have ever had in science. You look at the image and then suddenly everything comes together. You know exactly what you've seen. And you're seeing something that no-one else had ever seen before. It was wonderful."
Laura Ferrarese: "I've done a lot of research with Hubble and in fact almost all my work has been done with or based on Hubble images. But perhaps my very favourite was this one galaxy that we observed very very early on. NGC 4261.
And what we saw when we looked at this galaxy was that there is a very small disc of gas and dust at the centre and we could use the velocity of the gas in the disc to measure the mass of the central supermassive black hole. And that was one of the very first conclusive evidence for the presence of a black hole in a galaxy."
Sandy Faber: "I think that my favourite Hubble discovery is based on aesthetics. And it's the imaging of these giant clusters of galaxies that show these beautiful gravitational lenses. The red cluster galaxies and the blue background galaxies. General relativity in action there, bending light and making images that are just stunning. I wish I had done that!"
Monica Tosi: "I tend to favour the wonderful images that have allowed to obtain very tight and deep colour-magnitude diagrams, see how stars form and evolve in nearby galaxies."
Joe Liske: "So clearly Hubble has made a lot of fantastic observations of the Universe during its lifetime. And I for one find it hard to pick what my favourite Hubble moment is. So one of my favourite Hubble achievements were the images Hubble took of planet Fomalhaut b. These were the first images of an extrasolar planet that were taken in optical light. And by using multiple observations, Hubble actually allowed us to watch this planet move on its orbit around its parent star. So another great Hubble moment were the images that it took of the so-called Bullet Cluster. These are actually two colliding clusters of galaxies that demonstrate beautifully the existence of dark matter. And then of course the Hubble Space Telescope measured the so-called Hubble constant, which is the expansion speed of the Universe. Hubble did this more precisely than was ever done before -- and of course this was one of the main reasons for building Hubble in the first place."
• http://www.spacetelescope.org/
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Best0fScience uploaded a new video
(3 months ago)
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NASA's Swift Finds 'Missing' Active Galaxies.
Most large galaxies contain a giant central black hole. In ...
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NASA's Swift Finds 'Missing' Active Galaxies.
Most large galaxies contain a giant central black hole. In an active galaxy, matter falling toward the supermassive black hole powers high-energy emissions so intense that two classes of active galaxies, quasars and blazars, rank as the most luminous objects in the universe. Thick clouds of dust and gas near the central black hole screens out ultraviolet, optical and low-energy (or soft) X-ray light.
Although there are many different types of active galaxy, astronomers explain the different observed properties based on how the galaxy angles into our line of sight. We view the brightest ones nearly face on, but as the angle increases, the surrounding ring of gas and dust absorbs increasing amounts of the black hole's emissions.
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Most big galaxies contain big black holes. Not just big, supersized, with millions of times the sun's mass. Some of these black holes are actively devouring gas. This drives particle jets that can spew matter millions of light-years into space, and it also makes the holes a source of penetrating, or hard, X-rays. At these energies, the sky glows in every direction, even far away from bright sources.
Astronomers have long suspected that active supermassive black holes in galaxies were responsible, but they just couldn't find enough of them to account for the X-ray glow — especially the peak of the energy spectrum. Now, astronomers using NASA's Swift satellite confirm that a largely unseen population of black-hole-powered galaxies is out there.
There are so many that scientists say they might fully account for the cosmic X-ray background. What emission we detect from an active black hole is a function of how we see it — whether we're looking face-on and into one of it's jets, or viewing it from the side, through the disk of gas and dust that surrounds it.
The brightest active black holes, which include quasars and blazars, are those we see face-on. But as the viewing angle increases, the surrounding disk absorbs increasing amounts of radiation. Astronomers have always assumed that many active galaxies were oriented edgewise to us, but because the disk of gas smothers most of their X-rays, these sideways black holes just weren't detected.
And that's where Swift comes in. Since 2004, the satellites Burst Alert Telescope has been building up the largest, most sensitive X-ray map of the sky. Using these data, astronomers found that the most heavily absorbed galaxies create the energy peak in the cosmic X-ray background.
What does it all mean? When the universe was about half its present age, about 7 billion years ago, galaxies crashed together more frequently and these collisions produced gas rich galaxies with heavily obscured black holes.
The Swift survey shows that galaxy mergers helped activate these black holes by feeding them torrents of fresh gas. The new findings are consistent with idea that the X-ray background peaked around this time, when our own galaxy was young and before our solar system was born.
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Best0fScience uploaded a new video
(3 months ago)
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CERN News: First heavy ions in the LHC.
The LHC runs led ions for the first time, reaching unprecedented ...
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CERN News: First heavy ions in the LHC.
The LHC runs led ions for the first time, reaching unprecedented collision energy. Interviews with Jürgen Schukraft (ALICE spokesperson), Bolek Wyslouch (CMS run coordinator), Peter Steinberg (ATLAS Brookhaven National Laboratory), William Brooks (ATLAS Brookhaven National Laboratory).
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First heavy-ion collisions in CMS
The CMS experiment at CERN's Large Hadron Collider (LHC) has recorded its first Lead-Lead collisions at a centre-of-mass energy of 2.76 TeV per nucleon pair, marking the start of its heavy ion research programme. Physicists around the world expect a wealth of new results and phenomena from these collisions, which occur at energies 14 times higher than previously achieved by the Relativistic Heavy Ion Collider (RHIC, Brookhaven, USA).
At 11:20:56, on 8th November the LHC Control Centre declared stable colliding beams of heavy ions. CMS immediately detected the first collisions, each producing thousands of particles whose trajectories are reconstructed in the CMS silicon detectors and whose energies are measured in the calorimeters. Moments later, the data were analysed and the first images of these events were produced.
• http://cms.web.cern.ch/cms/News/2010/...
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CERN, the European Organization for Nuclear Research, is one of the world's largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world's largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.
The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.
Founded in 1954, the CERN Laboratory sits astride the Franco--Swiss border near Geneva. It was one of Europe's first joint ventures and now has 20 Member States.
CERN's mission:
• Research: Seeking and finding answers to questions about the Universe
• Technology: Advancing the frontiers of technology
• Collaborating: Bringing nations together through science
• Education: Training the scientists of tomorrow
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