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Mars Base

Has Dark Matter Been Seen? | Dark Matter and Dark Energy | Space.com - 0 views

www.space.com/rk-matter-detection-wimps.html

scibyte91 DarkMatter

shared by Mars Base on 16 Apr 13 - No Cached
  • absolute zero, which is minus 459.67 degrees Fahrenheit, or minus 273.15 degrees Celsius
  • the signals detected could also be statistical hiccups
  • Scientists would expect to see three or more of these WIMP-like events 5.4 percent of the time simply due to random fluctuations in the experiment
  • ...4 more annotations...
  • But the fluctuations detected by the experiment are in a similar energy range, which is less likely to be a random accident
  • the signal is 99.81 percent more likely to be WIMP than simply background fluctuations, Cabrera said.
  • mass is consistent with earlier CDMS results as well as another dark-matter-hunting experiment called CoGeNT at the U.S. Department of Energy's Pacific Northwest National Laboratory
  • contradicts preliminary results seen at the international XENON Dark Matter Project, a major experiment located in Italy
Mars Base

Dark matter detector reports hints of WIMPs | Atom & Cosmos | Science News - 0 views

www.sciencenews.org/...etector_reports_hints_of_WIMPs

scibyte91 DarkMatter

shared by Mars Base on 16 Apr 13 - No Cached
  • Ultracold crystals designed to catch particles of dark matter deep underground have come up with three potential detections
  • The researchers do not have enough evidence to say they have discovered dark matter particles
  • Theoretical physicists have put forth some ideas for particles that might constitute dark matter, including one called a weakly interacting massive particle, or WIMP.
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  • The experiment that made the newly reported detections is designed to pick up the signal of a WIMP as Earth passes through the galaxy
  • The Cryogenic Dark Matter Search consists of a network of silicon and germanium crystals cooled to near absolute zero
  • in the Soudan Underground Laboratory in Minnesota, a former iron mine more than 700 meters beneath the surface
  • If WIMPs exist, one should very occasionally slam into the nucleus of a silicon or germanium atom, causing a release of energy and a detectable vibration in the crystal
  • The hundreds of meters of earth above the experiment prevent other particles, such as protons and neutrons, from reaching the crystals and triggering a false positive
  • between July 2007 and September 2008, two of the experiment’s 11 silicon crystal detectors picked up three signals consistent with those expected from WIMP interactions
  • If the signals were caused by WIMPs
  • estimates the dark matter particle would weigh in at about 10 times the mass of the proton, well below many theoretical estimates
  • While the crystals’ underground setup provides plenty of shielding, some non-WIMP particles, such as electrons on the crystals’ surface, can cloud the results
  • it’s extremely unlikely that three events would show up from non-WIMP sources.
  • the energy released by the potential WIMPs is at the very lower limit of the detectors’ sensitivity
  • making erroneous WIMP detections more likely
  • concerns that the two crystals that picked up the signal could be more susceptible to false positives than the rest
  • In 2009, CDMS published a paper reporting that its germanium detectors had snagged two potential WIMPs, but further analysis revealed them to be surface electrons
  • more convinced if the detectors had picked up 10 or 12 signs of WIMPs, rather than just three
  • definitive detection would require multiple experiments worldwide to converge on the same characteristics for a dark matter particl
  • One in Italy called DAMA, short for Dark Matter, has made bold claims of dark matter detection that have drawn skepticism from many scientists
  • Other experiments have claimed to find signals at masses similar to this latest CDMS calculation but have not definitively said they have observed WIMPs
  • each experiment uses a different detection technique and has its own protocol for distinguishing WIMPs from background noise, making it hard to compare results
  • As for CDMS, the silicon detectors that found these signals are no longer collecting data
  • Researchers recently upgraded the Soudan facility with supersensitive germanium detectors
  • Over the next few years, the germanium detectors will move to a new, deeper underground home in Sudbury, Ontario, about 2 kilometers below the surface
Mars Base

Scientists report hint of dark matter in first results from $2 billion cosmic ray detec... - 0 views

phys.org/...hint-dark-results-billion.html

scibyte89 DarkMatter

shared by Mars Base on 04 Apr 13 - No Cached
  • A $2 billion cosmic ray detector on the International Space Station has found the footprint of something that could be dark matter
  • the evidence isn't enough to declare the case closed
  • And after two years, the first evidence came in Wednesday: tantalizing cosmic footprints that seem to have been left by dark matter.
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  • the first results from the Alpha Magnetic Spectrometer, known by its acronym AMS,
  • show evidence of new physics phenomena that could be the strange and unknown dark matter or could be energy that originates from pulsars
  • expects a more definitive answer in a matter of months
  • Unraveling the mystery of dark matter could help scientists better understand the composition of our universe and, more particularly, what holds galaxies together
  • The 7-ton detector with a 3-foot magnet ring at its core was sent into space in 2011
  • The device is transmitting its data to CERN, where it is being analyzed
  • For 80 years scientists have theorized the existence of dark matter but have never actually observed it directly
  • They have looked for it in accelerators that smash particles together at high speed
  • deep underground with special detectors
  • no luck
  • there's a third way: looking in space for the results of rare dark matter collisions
  • If particles of dark matter crash and annihilate each other, they should leave a footprint of positrons—the anti-matter version of electrons—at high energy levels
  • found some. But they could also be signs of pulsars
  • What's key is the curve of the plot of those positrons. If the curve is one shape, it points to dark matter. If it's another, it points to pulsars
  • they should know the curve—and the suspect—soon
  • since its installation on 19 May 2011 it has measured over 30 billion cosmic rays at energies up to trillions of electron volts
  • Its permanent magnet and array of precision particle detectors collect and identify charged cosmic rays passing through AMS from the far reaches of space
  • Over its long duration mission on the ISS, AMS will record signals from 16 billion cosmic rays every year and transmit them to Earth for analysis by the AMS Collaboration.
  • In the initial 18 month period of space operations, from 19 May 2011 to 10 December 2012, AMS analyzed 25 billion primary cosmic ray events
  • Of these,
  • 6.8 million, were unambiguously identified as electrons and their antimatter counterpart, positrons.
  • Positrons are clearly distinguished from this background through the robust rejection power of AMS of more than one in one million
  • Currently, the total number of positrons identified by AMS, in excess of 400,000, is the largest number of energetic antimatter particles directly measured and analyzed from space
  • The exact shape of the spectrum, as shown in Figure 2, extended to higher energies, will ultimately determine whether this spectrum originates from the collision of dark matter particles or from pulsars in the galaxy
  • by measuring the ratio between positrons and electrons and by studying the behavior of any excess across the energy spectrum, a better understanding of the origin of dark matter and other physics phenomena can be obtained
Mars Base

Scientists sense breakthroughs in dark-matter mystery - 0 views

phys.org/...oughs-dark-matter-mystery.html

scibyte82 scibyte83 DarkMatter

shared by Mars Base on 19 Feb 13 - No Cached
  • Dark matter throws down the gauntlet to the so-called Standard Model of physics.
  • Elegant and useful for identifying the stable of particles and forces that regulate our daily life, the Standard Model only tells part of the cosmic story
  • it does not explain gravity, although we know how to measure gravity and exploit it for our needs
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  • the Standard Model has been found to account for only around four or five percent of the stuff in the Universe
  • dark matter, making up 23 percent, and dark energy, an enigmatic force that appears to drive the expansion of the Universe, which accounts for around 72 or 73 percent.
  • The dark matter theory was born 80 years ago when Swiss astrophysicist Fritz Zwicky discovered that there was not enough mass in observable stars or galaxies to allow the force of gravity to hold them together
  • why dark matter has six times the energy that is in ordinary matter
  • could be 10 trillions times bigger
  • first results will be published in two to three weeks
  • High-powered instruments track cosmic particles
  • To track these phantom particles, physicists rely on several methods and tools
  • One is the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station (ISS), which captures gamma rays coming from collisions of dark matter particles.
  • only suggesting that these highly anticipated results would give humans a better idea about the nature of dark matter
  • Another tool used by the scientists is the South Pole Neutrino Observatory, which tracks subatomic particles known as neutrinos, which, according to physicists, are created when dark matter passes through the Sun and interacts with protons
  • Another
  • is the Large Hadron Collider (LHC) near Geneva, the biggest particle smasher in the world
Mars Base

Has Dark Matter Finally Been Found? Big News Soon | Space.com - 0 views

www.space.com/ter-found-nasa-experiment.html

scibyte82 scibyte83 DarkMatter

shared by Mars Base on 19 Feb 13 - No Cached
  • the Alpha Magnetic Spectrometer, a particle collector mounted on the outside of the International Space Station
  • first paper of results
  • in about two weeks
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  • e said the results bear on the mystery of dark matter,
  • "It will not be a minor paper,"
  • important enough that the scientists rewrote the paper 30 times before they were satisfied with it
  • it represents a "small step" in figuring out what dark matter is, and perhaps not the final answer
  • Some physics theories suggest that dark matter is made of WIMPS (weakly interacting massive particles), a class of particles that are their own antimatter partner particles
  • When matter and antimatter partners meet, they annihilate each other, so if two WIMPs collided, they would be destroyed, releasing a pair of daughter particles — an electron and its antimatter counterpart, the positron, in the process
  • Alpha Magnetic Spectrometer has the potential to detect the positrons and electrons produced by dark matter annihilations in the Milky Way
  • was installed on the International Space Station in May 2011, and so far, it has detected 25 billion particle events, including about 8 billion electrons and positrons
  • This first science paper will report how many of each were found, and what their energies are
  • If the experiment detected an abundance of positrons peaking at a certain energy, that could indicate a detection of dark matter,
  • while electrons are abundant in the universe around us, there are fewer known processes that could give rise to positrons
  • The smoking gun signature is a rise and then a dramatic fall" in the number of positrons with respect to energy
  • he positrons produced by dark matter annihilation would have a very specific energy, depending on the mass of the WIMPs making up dark matter
  • Another telling sign will be the question of whether positrons appear to be coming from one direction in space, or from all around
  • f they're from dark matter, scientists expect them to be spread evenly through space, but if they're created by some normal astrophysical process, such as a star explosion, then they would originate in a single direction
  • There is a lot of stuff that can mimic dark matter,"
  • Regardless of whether AMS has found dark matter yet, the scientists said they expected the question of dark matter's origin to become clearer soon
Mars Base

Cosmology group finds measurable evidence of dark matter filament - 0 views

phys.org/...up-evidence-dark-filament.html

scibyte53 DarkMatter

shared by Mars Base on 05 Jul 12 - No Cached
  • As time passes and more research is done, more evidence is compiled supporting the theory that suggests that dark matter is a real thing, even though no direct evidence for its existence has ever been found
  • evidence comes about as measurements of other phenomenon are taken, generally involving gravitational pull on objects in the universe we can see that cannot be explained by other means
  • One of these instances is where weak gravitational lensing occurs, which is where light appears to bend as it passes by large objects
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  • Theory suggests that in cases where lensing occurs but there is no detectable object behind its cause, the reason for it is dark matter exerting a gravitational influence
  • That has been the case with what are known as filaments; gravitational effects that connect galactic superclusters, keeping them bound together.
  • Abell 222/223 is a galactic supercluster system in the constellation Cetus. It’s made up of two parts, 222 and 223, separated by a gas cloud and something else that cannot be seen
  • Dietrich and his team found that lensing occurred as light behind the gas cloud made its way to us by passing between the two parts
  • after careful study and mathematical analysis, they found that the observable matter that existed in the gas cloud could only account for about nine percent of the mass required to cause the degree of lensing that was occurring
  • the only possible explanation was that dark matter in the shape of a filament was the cause.
  • results
  • are doubly interesting
  • they strengthen all of the theories surrounding dark matter
  • because the team has found a means of not just demonstrating an example of dark matter at work, but have done so in a way that is so precise that they were able to determine the actual shape of a dark matter filament
  • measurements of lensing were taken at different parts of the area between 222 and 223 showing different degrees of light bending
  • only possible because of the unique way the supercluster is situated relative to us, allowing a nearly straight on view
Mars Base

Could 'Mirror Neutrons' Account for Unobservable Dark Matter? - 0 views

www.universetoday.com/...t-for-unobservable-dark-matter

scibyte52 DarkMatter neutron

shared by Mars Base on 19 Jun 12 - No Cached
  • Could mirror universes or parallel worlds account for dark matter
  • new paper by a team of theoretical physicists hypothesizes the existence of mirror particles as a possible candidate for dark matter
  • Each neutron would have the ability to transition into its invisible mirror twin, and back, oscillating from one world to the other
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  • reanalyzed the experimental data
  • which showed that the loss rate of very slow free neutrons appeared to depend on the direction and strength of the magnetic field applied.
  • oscillations between the parallel worlds could occur within a timescale of a few seconds
  • This isn’t the first time the existence of mirror matter has been suggested and has been predicted to be sensitive to the presence of magnetic field such as Earth’s
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