CERNLAND

Geneva, 13 March 2009. Web veteran Robert Cailliau today launchedCERNland, a new website for young people, on the occasion of the Web's20th anniversary. CERNland has been developed to bring the excitement ofCERN*'s research to a young audience aged 7 to 12 through a range offilms, games and multimedia applications. It is available athttp://www.cern.ch/cernland

Precision measurement of W boson mass:

Precision measurement of W boson mass:photos and graphics
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The Standard Model describes the interactions of the fundamental particle of the world around us. Experimental observations agree with the predictions of the Standard Model with high precision. The W boson, the carrier of the electroweak force, is a key element in these predictions. Its mass is a fundamental parameter relevant for many predictions, including the energy emitted by our sun to the mass of the elusive Standard Model Higgs boson, which provides elementary particles with mass. Credit: Fermilab

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Fermilab's DZero collaboration obtained the world’s most precise W mass value measured by a single experiment and announced its result at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond on March 8. Physicist Jan Stark, of the Laboratoire de Physique Subatomique in Grenoble, France, presented the result. Credit: DZero collaboration

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The DZero collaboration comprises about 550 scientists from 18 countries who designed and built the 5,500-ton DZero detector and now collect and reconstruct collision data. They research a wide range of Standard Model topics and search for new subatomic phenomena. Credit: DZero collaboration

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The Fermilab accelerator complex accelerates protons and antiprotons close to the speed of light. The Tevatron collider, four miles in circumference, produces millions of proton-antiproton collisions per second, maximizing the chance for discovery. Two experiments, CDF and DZero, record the collisions to look for signs of new particles and subatomic processes. Credit: Fermilab

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The DZero detector records particles emerging from high-energy proton-antiproton collisions produced by the Tevatron. For the W mass precision measurement, the DZero collaboration analyzed about 500,000 decays of W bosons into electrons and neutrinos and determined the particle's mass with a precision of 0.05 percent. Credit: Fermilab

Precision measurement of W boson mass portends stricter limits for Higgs

Batavia, Ill.--Scientists of the CDF and DZero collaborations at theDepartment of Energy's Fermi National Accelerator Laboratory have observedparticle collisions that produce single top quarks. The discovery of thesingle top confirms important parameters of particle physics, includingthe total number of quarks, and has significance for the ongoing searchfor the Higgs particle at Fermilab's Tevatron, currently the world's mostpowerful operating particle accelerator.Previously, top quarks had only been observed when produced by the strongnuclear force. That interaction leads to the production of pairs of topquarks. The production of single top quarks, which involves the weaknuclear force and is harder to identify experimentally, has now beenobserved, almost 14 years to the day of the top quark discovery in 1995.Searching for single-top production makes finding a needle in a haystacklook easy. Only one in every 20 billion proton-antiproton collisionsproduces a single top quark. Even worse, the signal of these rareoccurrences is easily mimicked by other "background" processes that occurat much higher rates."Observation of the single top quark production is an important milestonefor the Tevatron program," said Dr. Dennis Kovar, Associate Director ofthe Office of Science for High Energy Physics at the U.S. Department ofEnergy. "Furthermore, the highly sensitive and successful analysis is animportant step in the search for the Higgs."Discovering the single top quark production presents challenges similar tothe Higgs boson search in the need to extract an extremely small signalfrom a very large background. Advanced analysis techniques pioneered forthe single top discovery are now in use for the Higgs boson search. Inaddition, the single top and the Higgs signals have backgrounds in common,and the single top is itself a background for the Higgs particle.To make the single-top discovery, physicists of the CDF and DZerocollaborations spent years combing independently through the results ofproton-antiproton collisions recorded by their experiments, respectively.Each team identified several thousand collision events that looked the wayexperimenters expect single top events to appear. Sophisticatedstatistical analysis and detailed background modeling showed that a fewhundred collision events produced the real thing. On March 4, the twoteams submitted their independent results to Physical Review Letters.The two collaborations earlier had reported preliminary results on thesearch for the single top. Since then, experimenters have more thandoubled the amount of data analyzed and sharpened selection and analysistechniques, making the discovery possible. For each experiment, theprobability that background events have faked the signal is now only onein nearly four million, allowing both collaborations to claim a bona fidediscovery that paves the way to more discoveries."I am thrilled that CDF and DZero achieved this goal," said FermilabDirector Pier Oddone. "The two collaborations have been searching for thisrare process for the last fifteen years, starting before the discovery ofthe top quark in 1995. Investigating these subatomic processes in moredetail may open a window onto physics phenomena beyond the StandardModel."Media Contacts:Judy Jackson, Fermilab, +1-630-840-3351, http://tr.mc371.mail.yahoo.com/mc/compose?to=jjackson@fnal.govKurt Riesselmann, Fermilab, +1-630-840-3351, http://tr.mc371.mail.yahoo.com/mc/compose?to=kurtr@fnal.govGraphics and photos are available at:http://www.fnal.gov/pub/presspass/images/Single-Top-Quark-2009.htmlNotes for Editors:Fermilab, the U.S. Department of Energy's Fermi National AcceleratorLaboratory located near Chicago, operates the Tevatron, the world'shighest-energy particle collider. The Fermi Research Alliance LLC operatesFermilab under a contract with DOE.CDF is an international experiment of 635 physicists from 63 institutionsin 15 countries. DZero is an international experiment conducted by 600physicists from 90 institutions in 18 countries. Funding for the CDF andDZero experiments comes from DOE's Office of Science, the National ScienceFoundation, and a number of international funding agencies.CDF collaborating institutions are athttp://www-cdf.fnal.gov/collaboration/index.htmlDZero collaborating institutions are athttp://www-d0.fnal.gov/ib/Institutions.htmlCopies of the two scientific papers submitted to Physical Review Lettersare available at: * http://arxiv.org/PS_cache/arxiv/pdf/0903/0903.0885v1.pdf * http://arxiv.org/PS_cache/arxiv/pdf/0903/0903.0850v1.pdfInterAction Collaboration media contacts:A full list of InterAction media contacts is available at:http://www.interactions.org/presscontacts/.

Fermilab collider experiments discover rare single top quark

Batavia, Ill.--Scientists of the CDF and DZero collaborations at theDepartment of Energy's Fermi National Accelerator Laboratory have observedparticle collisions that produce single top quarks. The discovery of thesingle top confirms important parameters of particle physics, includingthe total number of quarks, and has significance for the ongoing searchfor the Higgs particle at Fermilab's Tevatron, currently the world's mostpowerful operating particle accelerator.Previously, top quarks had only been observed when produced by the strongnuclear force. That interaction leads to the production of pairs of topquarks. The production of single top quarks, which involves the weaknuclear force and is harder to identify experimentally, has now beenobserved, almost 14 years to the day of the top quark discovery in 1995.Searching for single-top production makes finding a needle in a haystacklook easy. Only one in every 20 billion proton-antiproton collisionsproduces a single top quark. Even worse, the signal of these rareoccurrences is easily mimicked by other "background" processes that occurat much higher rates."Observation of the single top quark production is an important milestonefor the Tevatron program," said Dr. Dennis Kovar, Associate Director ofthe Office of Science for High Energy Physics at the U.S. Department ofEnergy. "Furthermore, the highly sensitive and successful analysis is animportant step in the search for the Higgs."Discovering the single top quark production presents challenges similar tothe Higgs boson search in the need to extract an extremely small signalfrom a very large background. Advanced analysis techniques pioneered forthe single top discovery are now in use for the Higgs boson search. Inaddition, the single top and the Higgs signals have backgrounds in common,and the single top is itself a background for the Higgs particle.To make the single-top discovery, physicists of the CDF and DZerocollaborations spent years combing independently through the results ofproton-antiproton collisions recorded by their experiments, respectively.Each team identified several thousand collision events that looked the wayexperimenters expect single top events to appear. Sophisticatedstatistical analysis and detailed background modeling showed that a fewhundred collision events produced the real thing. On March 4, the twoteams submitted their independent results to Physical Review Letters.The two collaborations earlier had reported preliminary results on thesearch for the single top. Since then, experimenters have more thandoubled the amount of data analyzed and sharpened selection and analysistechniques, making the discovery possible. For each experiment, theprobability that background events have faked the signal is now only onein nearly four million, allowing both collaborations to claim a bona fidediscovery that paves the way to more discoveries."I am thrilled that CDF and DZero achieved this goal," said FermilabDirector Pier Oddone. "The two collaborations have been searching for thisrare process for the last fifteen years, starting before the discovery ofthe top quark in 1995. Investigating these subatomic processes in moredetail may open a window onto physics phenomena beyond the StandardModel."Media Contacts:Judy Jackson, Fermilab, +1-630-840-3351, jjackson@fnal.govKurt Riesselmann, Fermilab, +1-630-840-3351, kurtr@fnal.govGraphics and photos are available at:http://www.fnal.gov/pub/presspass/images/Single-Top-Quark-2009.htmlNotes for Editors:Fermilab, the U.S. Department of Energy's Fermi National AcceleratorLaboratory located near Chicago, operates the Tevatron, the world'shighest-energy particle collider. The Fermi Research Alliance LLC operatesFermilab under a contract with DOE.CDF is an international experiment of 635 physicists from 63 institutionsin 15 countries. DZero is an international experiment conducted by 600physicists from 90 institutions in 18 countries. Funding for the CDF andDZero experiments comes from DOE's Office of Science, the National ScienceFoundation, and a number of international funding agencies.CDF collaborating institutions are athttp://www-cdf.fnal.gov/collaboration/index.htmlDZero collaborating institutions are athttp://www-d0.fnal.gov/ib/Institutions.htmlCopies of the two scientific papers submitted to Physical Review Lettersare available at: * http://arxiv.org/PS_cache/arxiv/pdf/0903/0903.0885v1.pdf * http://arxiv.org/PS_cache/arxiv/pdf/0903/0903.0850v1.pdfInterAction Collaboration media contacts:A full list of InterAction media contacts is available at:http://www.interactions.org/presscontacts/.

Kepler's Supernova Remnant:

Using NASA's Chandra X-ray Observatory, scientists have created a stunning new image of one of the youngest supernova remnants in the galaxy. This new view of the debris of an exploded star helps astronomers solve a long-standing mystery, with implications for understanding how a star's life can end catastrophically and for gauging the expansion of the universe.
Over 400 years ago, sky watchers -- including the famous astronomer Johannes Kepler -- noticed a bright new object in the night sky. Since the telescope had not yet been invented, only the unaided eye could be used to watch as a new star that was initially brighter than Jupiter dimmed over the following weeks.
Chandra's latest image marks a new phase in understanding the object now known as Kepler's supernova remnant. By combining nearly nine days of Chandra observations, astronomers have generated an X-ray image with unprecedented detail of one of the brightest recorded supernovas in the Milky Way galaxy.
The explosion of the star that created the Kepler remnant blasted the stellar remains into space, heating the gases to millions of degrees and generating highly energized particles. Copious X-ray light, like that shining from many supernova remnants, was produced.
Astronomers have studied Kepler intensively over the past three decades with radio, optical and X-ray telescopes, but its origin has remained a puzzle. On the one hand, the presence of large amounts of iron and the absence of a detectable neutron star points toward a so-called Type Ia supernova. These events occur when a white dwarf star pulls material from an orbiting companion until the white dwarf becomes unstable and is destroyed by a thermonuclear explosion.
On the other hand, when viewed in optical light, the supernova remnant appears to be expanding into dense material that is rich in nitrogen. This would suggest Kepler belongs to a different type of supernova (known as "Type II") that is created from the collapse of a single massive star that sheds material before exploding. Type Ia supernovas do not normally have such surroundings.
A team of astronomers, led by Stephen Reynolds of North Carolina State University in Raleigh, N.C., was able to use the Chandra dataset to address this mystery. By comparing the relative amounts of oxygen and iron atoms in the supernova, the scientists were able to determine that Kepler resulted from a Type Ia supernova.
In solving the mystery of Kepler's identity, Reynolds and his team have also given an explanation for the dense material in the remnant. Kepler could be the nearest example of a relatively rare "prompt" Type Ia explosion, which occur in more massive progenitors only about 100 million years after the star formed rather than several billion years. If that is the case, Kepler could teach astronomers more about all Type Ia supernovas and the ways in which prompt explosions from massive stars differ from their more common cousins associated with lower mass stars. This information is essential to improve the reliability of the use of Type Ia stars as "standard candles" for cosmological studies of dark energy as well as to understand their role as the source of most of the iron in the universe.
In the new Chandra Kepler image, red represents low-energy X-rays and shows material around the star -- dominated by oxygen -- that has been heated up by a blast wave from the star's explosion. The yellow color shows slightly higher energy X-rays, mostly iron formed in the supernova, while green (medium-energy X-rays) shows other elements from the exploded star. The blue color represents the highest energy X-rays and shows a shock front generated by the explosion.
NASA's three Great Observatories -- the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory -- joined forces to probe the expanding remains of a supernova. Now known as Kepler's supernova remnant, this object was first seen 400 years ago by sky watchers, including famous astronomer Johannes Kepler.
The combined image unveils a bubble-shaped shroud of gas and dust that is 14 light years wide and is expanding at 4 million miles per hour (2,000 kilometers per second). Observations from each telescope highlight distinct features of the supernova remnant, a fast-moving shell of iron-rich material from the exploded star, surrounded by an expanding shock wave that is sweeping up interstellar gas and dust.
Each color in this image represents a different region of the electromagnetic spectrum, from X-rays to infrared light. These diverse colors are shown in the panel of photographs below the composite image. The X-ray and infrared data cannot be seen with the human eye. By color-coding those data and combining them with Hubble's visible-light view, astronomers are presenting a more complete picture of the supernova remnant.
Visible-light images from the Hubble telescope (colored yellow) reveal where the supernova shock wave is slamming into the densest regions of surrounding gas.
The bright glowing knots are dense clumps from instabilities that form behind the shock wave. The Hubble data also show thin filaments of gas that look like rippled sheets seen edge-on. These filaments reveal where the shock wave is encountering lower-density, more uniform interstellar material.
The Spitzer telescope shows microscopic dust particles (colored red) that have been heated by the supernova shock wave. The dust re-radiates the shock wave's energy as infrared light. The Spitzer data are brightest in the regions surrounding those seen in detail by the Hubble telescope.
The Chandra X-ray data show regions of very hot gas, and extremely high energy particles.
The hottest gas (higher-energy X-rays, colored blue) is located primarily in the regions directly behind the shock front. These regions also show up in the Hubble observations, and also align with the faint rim of glowing material seen in the Spitzer data. The X-rays from the region on the lower left (blue) may be dominated by extremely high energy electrons that were produced by the shock wave and are radiating at radio through X-ray wavelengths as they spiral in the intensified magnetic field behind the shock front. Cooler X-ray gas (lower-energy X-rays, colored green) resides in a thick interior shell and marks the location of heated material expelled from the exploded star.
The remnant of Kepler's supernova, the last such object seen to explode in our Milky Way galaxy (with the possible exception of the Cassiopeia A supernova, for which ambiguous sightings were reported around 1680), is located about 13,000 light years away in the constellation Ophiuchus.
The Chandra observations were taken in June 2000, the Hubble in August 2003, and the Spitzer in August 2004.