Studies of supernova remnant RCW 86 have revealed the origin of cosmic rays. (Image courtesy of ESO/E. Helder and NASA/Chandra.)
An international team of researchers has discovered strong evidence that extremely energetic cosmic rays are born in supernova remnants.
“Cosmic rays constantly bombard the earth’s atmosphere but, until now, we didn’t have proof of where in our galaxy they originated,” said co-author Stefan Funk of the Kavli Institute for Particle Astrophysics and Cosmology at SLAC National Accelerator Laboratory. “That’s because cosmic rays are almost entirely made of protons, which as charged particles are bent by magnetic forces as they travel to Earth. So we can’t just trace a straight line back to know where they originated, like we can with light.”
Instead, the researchers traced the sources of cosmic rays by indirect means.
In a paper published last week in Science Express, the researchers describe measurements made with the European Southern Observatory’s Very Large Telescope and NASA’s Chandra X-ray Observatory. These measurements, of a star that exploded in the year A.D. 185, compare the temperature of the gas immediately behind the shockwave created by the stellar explosion with the speed of the shockwave itself. If the energy of the stellar explosion was converted solely into heat and motion, these two measurements should have been directly related by a very well-known and well-tested equation. Yet when the researchers plugged their measurements into the equation, it didn’t balance. Something else was being energized by the explosion.
“When a star explodes in what we call a supernova, a large part of the explosion energy is used for accelerating some particles up to extremely high energies,” said co-author Eveline Helder of the Astronomical Institute Utrecht in the Netherlands. “The energy that is used for particle acceleration is at the expense of heating the gas, which is therefore much colder than theory predicts.”
The researchers concluded that the missing energy goes into accelerating protons to nearly the speed of light-creating the cosmic rays that continually pummel our solar system, creating flashes of light behind the eyelids of astronauts and causing glitches in electronic components on Earth.
“Our observations reveal the smoking gun,” said Helder.
This story was first published in SLAC Today on June 30, 2009.
Once produced, the Omega-sub-b (Ωb) particle travels about a third of a millimeter before it disintegrates into two intermediate particles called J/Psi (J/ψ) and Omega-minus (Ω-). The J/Psi then promptly decays into a pair of muons. The Omega-minus baryon, on the other hand, can travel several centimeters and occasionally be measured in the CDF silicon vertex detector. The particle decays into an unstable particle called a Lambda (Λ) baryon along with a long-lived kaon particle (K). The Lambda baryon, which has no electric charge, also can travel several centimeters prior to decaying into a proton (p) and a pion (π). Credit: CDF collaboration.
At a recent physics seminar at the Department of Energy’s Fermi National Accelerator Laboratory, Fermilab physicist Pat Lukens of the CDF experiment announced the observation of a new particle, the Omega-sub-b (Ωb). The particle contains three quarks, two strange quarks and a bottom quark (s-s-b). It is an exotic relative of the much more common proton and has about six times the proton’s mass.
The discovery of this “doubly strange” particle, predicted by the Standard Model, is significant because it strengthens physicists’ confidence in their understanding of how quarks form matter–and because it conflicts with a 2008 result announced by CDF’s sister experiment, DZero.
The Omega-sub-b is the latest entry in the “periodic table of baryons.” Baryons are particles formed of three quarks, the most common examples being the proton and neutron. The Tevatron particle accelerator at Fermilab is unique in its ability to produce baryons containing the b quark, and the large data samples now available after many years of successful running enable experimenters to find and study these rare particles. The observation opens a new window for scientists to investigate its properties and better understand this rare object.
Combing through almost half a quadrillion (1000 billion) proton-antiproton collisions produced by Fermilab’s Tevatron particle collider, the CDF collaboration isolated 16 examples in which the particles emerging from a collision revealed the distinctive signature of the Omega-sub-b. Once produced, the Omega-sub-b travels a few millimeters before it decays into lighter particles. This decay, mediated by the weak force, occurs in about a trillionth of a second.
Late in 2008, DZero, the sister experiment to CDF, announced its own observation of the Omega-sub-b based on a smaller sample of Tevatron data. Interestingly, the new CDF observation announced here is in direct conflict with the earlier DZero result. The CDF physicists measured the Omega-sub-b mass to be 6054.4±6.8(stat.) ±0.9(syst.) GeV/c2 , compared to DZero’s 6.165 ± 0.016 GeV/c2. These two experimental results are statistically inconsistent with each other leaving scientists from both experiments wondering whether they are measuring the same particle. Furthermore, the experiments observed different rates of production of this particle. Perhaps most interesting is that neither experiment sees a hint of evidence for the particle at the other’s measured value.
Although the latest result announced by CDF agrees with theoretical expectation for the Omega-sub-b both in the measured production rate and in the mass value, further investigation is needed to solve the puzzle of these conflicting results.
The Omega-sub-b discovery follows the observation of the Cascade-b-minus baryon (Ξb), first observed at the Tevatron in 2007, and two types of Sigma-sub-b baryons (Σb), discovered at the Tevatron in 2006.
Speaking to a crowd of more than 800 this morning at SLAC National Accelerator Laboratory, Secretary of Energy Steven Chu urged researchers to confront what he called “the energy challenge.”
“For the first time in history, science has shown humans altering the destiny of our planet in a meaningful way,” he said. “We have to try to enlist some of the very best intellectual horsepower to deal with this.”
In a wide-ranging speech that touched on worldwide emissions, climbing global temperatures, changing precipitation patterns, increasing atmospheric carbon dioxide concentrations, and the rising sea level, Chu demonstrated how the energy challenge cuts across many areas and is intensely tied to our economic prosperity.
“But there’s reason for hope,” he said. “Scientists by their very nature have to be very optimistic… We can fix this.”
Pointing to historical examples of research easing global problems-including the invention of artificial fertilizer, which helped set off the so-called “green revolution”-Chu expressed his belief that science research would again come to the world’s aid.
“It was scientific discoveries that enabled the world to feed itself,” Chu said. Now, he continued, scientific discoveries can increase energy efficiency and develop improved means of generating clean energy.
“There are lots of really exciting things that people at SLAC can think about,” he said. “Research can spur incredible intellectual achievement. And in the field of energy, I think we can do some really great science. A physicist or applied mathematician can really start to drool at these problems.”
Chu, who received the 1997 Nobel Prize in Physics for his work in cooling and trapping atoms with laser light, is a former chair of the Stanford University physics department. Prior to becoming Secretary of Energy, he was a professor of physics and molecular and cellular biology at the University of California, Berkeley, and the director of the Lawrence Berkeley National Laboratory.
The crew will blast through 50 feet of rock at the NOvA site to accommodate the detector facility.
Construction crews began digging at the future site of the NOvA detector facility in Ash River, Minn., on June 1.
The American Reinvestment and Recovery Act provided funds for the civil construction project.
Fifteen workers from Hoover Construction, a subcontractor of Adolfson & Peterson Construction, have been clearing the top layer of dirt and developing the roads at the site.
“It’s pretty much earth work now,” said Davin “Buddy” Juusola, senior project manager for Adolfson & Peterson. But once the dirt is cleared, the construction crew will face the Canadian Shield, a mass of 2.7 billion-year-old Precambrian rock that stretches 3 million square miles across Canada and dips into a small northern edge of the U.S.
Crews from Adolfson & Peterson often work with rock, but blasting at the NOvA site will present a unique challenge, said Juusola, who has worked with the construction company for nine years.
The crew will blast down 50 feet to accommodate the NuMI Off-Axis Electron Neutrino Appearance, NOvA, detector facility. The laboratory will house a 15,000-ton particle detector that physicists will use to study a beam of neutrinos originating at Fermilab.
Members of the crew have talked to local residents about the project, Juusola said. “They seem very excited. They’re very receptive to it.”
The appeal goes beyond an interest in the science. Local supplier Seppi Brothers Concrete Products, based in Virginia, Minn., will provide concrete for the site, and other businesses will likely become involved.
Juusola said this will be his first experience building a laboratory.
“There are not too many neutrino labs built,” he said. “It’s very unique, which makes it exciting. It’s a nice project to have on your resume.”
This story first appeared in Fermilab Today on June 26, 2009.
If CERN's Large Hadron Collider (LHC) can create Higgs bosons, a handful may appear in rare "exclusive" reactions that don't destroy the colliding protons--similar to a reaction now observed at Fermilab. CERN's ATLAS and CMS teams are considering adding equipment to their detectors (CMS shown here) to look for such events. Photo: CERN
Particle physicists at CERN’s Large Hadron Collider (LHC) hope to discover the Higgs boson amid the froth of particles born from proton-proton collisions. Results in the 19 June Physical Review Letters show that there may be a way to cut through some of that froth. An experiment at Fermilab’s proton-antiproton collider in Illinois has identified a rare process that produces matter from the intense field of the strong nuclear force but leaves the proton and antiproton intact. There’s a chance the same basic interaction could give LHC physicists a cleaner look at the Higgs.
A proton is always surrounded by a swarm of ghostly virtual photons and gluons associated with the fields of the electromagnetic and strong nuclear forces. Researchers have predicted that when two protons (or a proton and an antiproton) fly past one another at close range, within about a proton’s diameter, these virtual particle clouds may occasionally interact to create new, real (not virtual) particles. The original protons would merely lose some momentum and separate from the beam. Such an “exclusive” reaction–where the original particles don’t break apart–gives unusually clean data because there are so few particles to detect.
In the new experiment, researchers were looking for signs that the interaction of virtual gluons had generated short-lived particles including the Χc (“Chi-c”) and J/ψ mesons, which are charm-anticharm quark pairs that decay into muons and antimuons. The Χc reaction would be especially rare because it requires protons to donate two gluons each, a requirement that also makes detailed predictions challenging, says Fermilab’s Mike Albrow, a member of the Collider Detector at Fermilab (CDF) collaboration.
In 2007, CDF researchers observed hints of exclusive, virtual gluon reactions in the form of high-energy photons radiating from colliding protons and antiprotons. Now the team has sifted through nearly 500 muon-antimuon pairs, identifying 65 that must have come from the decay of the Χc–very close to the rate predicted in 2005 by a team at Durham University in England. Because the Χc has similar particle properties to the much heavier Higgs boson, the same basic reaction should produce the Higgs at the higher collision energies provided by the LHC, says Albrow. “It’s the strongest evidence that the Higgs boson must be produced this way, if it does exist.”
Based on the rate of Χc production, Albrow estimates LHC collisions could produce 100 to 1000 Higgs bosons per year in each of the accelerator’s two largest particle detectors, ATLAS and CMS. “Even a few dozen events per year would enable you to measure the [Higgs's] mass, spin, and other properties,” he says. That’s why ATLAS and CMS teams are reviewing proposals to add detectors to look for exclusive Higgs events.
But not everyone is so optimistic that these events would be detectable in significant numbers. “It looks hard, but one should never say never,” says Joseph Incandela of the University of California, Santa Barbara, deputy physics coordinator for CMS. Incandela points out that once the LHC is operating at full capacity, every crossing of its twin proton beams is expected to yield about 20 collisions, throwing up other particles that may obscure exclusive reactions. But he says there are scenarios such as supersymmetry, a proposed extension to the standard model (the textbook theory of particle physics) in which there could be multiple Higgs bosons. In those situations, Albrow adds, exclusive reactions might be the only ones clean enough to distinguish the different Higgs particles.
by JR Minkel
JR Minkel is a freelance science writer in Nashville, Tennessee. His first book, Instant Egghead Guide: The Universe, comes out in July.
This story was first published in Physical Review Focus and is copyright American Physical Society. Reprinted with permission.
For more information on exclusive events, see the CERN Courier.
In honor of the start of construction for NSLS-II, members of the Center for Dance, Movement and Somatic Learning at Stony Brook University performed a special interpretive dance titled Time and Space for Celebration. Photo: Brookhaven National Laboratory
While writers have produced volumes of words on the beauty of scientific discovery, science and the performing arts have traditionally had a much lower rate of interaction.
However, such happy anomalies do sometimes occur.
Before the official speeches began at the National Synchrotron Light Source II start-of-construction celebration on June 15, 2009, employees, users, and guests of Brookhaven National Laboratory were reminded of the more poetic side of science by a distinctly non-verbal type of communication.
Slowly creeping in from stage-right, a lone dancer dressed in fluorescent green quickly commanded the attention of the audience with tribal stomps and dramatic leaps, performing a contemporary dance piece titled, Time and Space for Celebration.
Michelle Mitchell, a dance student majoring in engineering at Stony Brook University, seemed to question and explore her environment through movement, dancing to music that was both primal and futuristic. Her only companion on the stage was a giant three-dimensional geometric figure-an icosahedron-constructed of white PVC pipe.
A sense of curiosity, according to Amy Yopp Sullivan, choreographer and director of the Center for Dance, Movement and Somatic Learning at Stony Brook, was the main inspiration for the piece.
“We [the creative team] played with the idea of a primal, organic creature interacting with a mathematical structure,” she recalled. “We explored the mystery of discovery.”
To convey the scientific aspect of the theme, Yopp chose a life-sized icosahedrons-the 20-sided Platonic solid-to be the focal point of the piece. Mitchell interacted with the figure throughout the dance, approaching it with hesitation at first, but eventually dancing with and even inside of the structure. But the icosahedron was no arbitrary prop.
In addition to being visually striking, this figure also has strong ties to the “spatial harmony” ideas of the dance theorist Rudolf Laban. Working in the early decades of the 20thCentury, Laban is most famous for his development of a highly influential system of movement notation, much akin to the dots and shapes used by composers to represent sound. His further contributions included introducing concepts typically associated with music, such as scale, resonance, and harmony, to the world of dance. Like a symphony from the few notes of a theme, Laban’s theory facilitated the construction of large-scale choreography from the rudimentary materials of movement.
Another key element of Laban’s work was his intense fascination with the Platonic solids-a family of three-dimensional geometric figures which includes the tetrahedron, cube, and icosahedron-and with what he saw to be the movements suggested by their division of space. Sullivan found this idea to be particularly relevant to Celebration, relying heavily on Laban’s work in constructing her choreography.
“Through Laban’s theory, we can understand how movement is organized by space,” Sullivan explained. “The shape of the space suggests certain pulls and following those pulls yields organization in the body.”
Mitchell added that it was “a lot of fun” to experiment with how her body could relate to the shape.
While the inherent structure of the icosahedron influenced much of Mitchell’s movements in Celebration, the accompanying musical score was equally important. Written by professional composer and SBU graduate student Max Giteck Duykers, the 10 minutes of music comprised a wide palate of electronic and acoustic sounds layered over driving rhythms.
According to Duykers, scientific concepts of light-appropriate for a new light source-figured heavily in his compositional process.
“I was thinking a lot about light frequencies and particles moving, slowing down, and speeding up,” he said regarding the origins of the music. “You can hear that in the way that the tempo changes.”
Another notable aspect of the score was a repeated fluttering figure, a gesture that Mitchell seemed to imitate in her physical motions at times by quickly tapping her chest and stamping her feet. Remarking that, as a choreographer, she “is always inspired by Max’s music,” Sullivan explained that this correlation has to do with the heart being the organic “core” of the body.
“The heart feeds the whole body. The fluttering in Max’s music seems to echo that enlivening process,” she said. Reflecting on the gesture, Sullivan and Mitchell agreed that the tapping motion may have been the actual seed of the choreography. “The rest probably grew organically from there,” Mitchell concluded.
Indeed, “organic” was the main word the artists used to describe the creation of the piece. A main question for both choreographer and composer, Sullivan said, was, “How do we remain connected to an organic existence in an increasingly artificial world?” In discussing the development of the work, the team stressed the importance of a “collaborative, creative process” in which the movements and music changed and grew toward the final product in tandem.
Considering the result of their efforts, each artist hoped that the audience would leave the performance with a new perspective on the connectedness of art and science, as well as an invigorated passion for discovery.
“I hope people see that they can reach past their current circumstances,” Mitchell said with a smile. “We shouldn’t be stagnant. We can go after our dreams.”
With a projected commissioning date in 2015, the scientists and engineers currently constructing NSLS-II are doing just that.
Cervando Castro (left) watches the monitors and operates the remote crane control with technicians John Featherstone and Keith Anderson (center) for the NuMI experiment.
In a few weeks, Cervando Castro will use a remote control crane to change a key piece of equipment in Fermilab’s neutrino program. He will be located behind several feet of concrete shielding at distances of up to 100 feet from the component. It’s a job where steady hands and sharp eyes are essential.
“Cervando’s very focused and very calm in high-pressure situations,” said Kris Anderson, lead engineer for NuMI target hall operations. “We rely on him a lot.”
As part of regular maintenance, Cervando will swap out the NuMI target, the piece of the experiment that helps to create neutrinos from protons. But, because the target sits directly in the beam path and becomes radioactive, Castro will use several video monitors and a remote crane control from behind shielding to do the job.
“Cervando has a lot of experience in the lab, he’s our main crane guy,” said Mike Andrews, NuMI shutdown coordinator.
Castro, who has a background in welding and auto mechanics, is the senior technician for the NuMI target hall. He assembles, installs and maintains equipment and parts for the experiment, a job he previously did in the mechanical support department for the Tevatron.
While assembly and maintenance are relativelyf commonplace for the 25-year laboratory veteran, Castro was thrilled about his new challenges and his vertical commute when he started at NuMI.
“The first couple of times I was pretty excited to go down 150 feet into the NuMI target hall,” Castro said.
Then, the diversity of tasks Castro’s job includes–from assembling very delicate pieces of equipments to moving large chunks of concrete–keep him challenged. The largest piece of equipment he has had to move with the crane weighed 50,000 pounds. His schedule keeps him busy too. As a NuMI technician, Castro has to make himself available day or night as his job requires.
“I’m willing to do that because I want help make this place run smoothly,” Castro said.
by Tia Jones
This story first appeared in Fermilab Today on June 22, 2009.
Collaborators on the Sloan Digital Sky Survey think they can pull off a “three-peat”–duplicating the success of two earlier sky sweeps.
The survey started in 1998 and made its way into the astronomical journals in 2000. Every year since then, at least one paper about the SDSS has made it in the list of the top 10 astronomy papers of the year.
SDSS-I and SDSS-II have spawned the spin offs Galaxy Zoo and Galaxy Zoo 2, which allowed anyone to classify galaxies from a home computer. More than 200,000 have done just that so far.
The Sloan Web site has gotten more than 467 million hits since 2001.
The astrophysics experiment has a following worthy of a championship sports team, and collaborators hope to keep the excitement rolling with the survey’s third phase started last year.
SDSS galaxy map
The most anticipated results from the six-year Sloan Digital Sky Survey-III will be from the Baryon Oscillation Spectroscopic Survey, one of three scientific themes researched by the project’s four surveys, says SDSS Director and University of Chicago Professor Richard Kron.
BOSS will map the 3-D distribution of 1.5 million luminous red galaxies, to measure the scale of density fluctuations in the universe, using spectra–an ordered array of the components of radio-frequency waves–collected from fall 2009 to spring 2014.
Pressure waves in the early expanding universe oscillated up to the time when the pressure fell to zero as the universe created conditions for ions and electrons to recombine and form atoms. The dark matter was pulled in by the density enhancements in the normal atomic matter, called baryonic matter. This resulted in a frozen pattern with a recognizable scale. Scientists can use the scale of these patterns in the density of matter to map the universe’s outward acceleration, caused by “dark energy.”
Kron, a scientist with the Fermilab Experimental Astrophysics group, highlighted this focus of the upcoming third survey in a talk to peers at a retreat of Fermilab’s Center for Particle Astrophysics in April, held at Fermilab. Kron, the project director for the first two SDSS runs, also discussed the discoveries of the original SDSS, which took place from 2000 to 2005, and SDSS-II which took place from 2005 to 2008.
Fermilab had a number of collaborators on the first two SDSS runs and continues to analyze data from those. Fermilab scientists Jim Annis, Huan Lin, Brian Yanny, Chris Stoughton, John Peoples, and Kron are collaborators for SDSS-III.
“The survey [BOSS] will also help us calibrate photometric redshifts from the Dark Energy Survey,” Kron says.
To measure distances, astrophysicists need to look for objects in the universe that have known values of luminosity or physical size.
BOSS will precisely measure the apparent size of a ruler using galaxy clustering (the baryon oscillation scale). The size of the ruler depends on only basic physical quantities: the distance sound traveled up to the time when particles recombined to form atoms and when the pressure waves stalled.
SDSS telescope
The SDSS surveys use a 2.5 meter telescope at the Apache Point Observatory in New Mexico. The telescope has a large-format digital camera and fiber-fed spectrographs.
The original goal of the first SDSS was to map large-scale structures using galaxies and quasars as tracers, both in imaging and spectroscopy. In five years, the scientists measured one million galaxy redshifts and 100,000 quasar redshifts. Kron says that the data gained from the first survey was useful across many fields of astronomy.
The SDSS-II survey used the same instrumentation and same selection of galaxies and quasars as the first.Improvements were made to the processing software.One of the discoveries of SDSS-II was a number of hyper-velocity stars, which move so fast they are hypothesized to have been accelerated with a slingshot-like effect as they passed near the massive black hole at the center of the Milky Way.
“The project has been a big success and has already made substantial contributions to the field of dark energy research,” Kron says.
In the months of May and June, more than 60 lectures about the science behind the book and film Angels & Demons took place in the United States, Canada, and Europe. If you weren’t one of the more than 5000 people who attended a lecture in person, now you can catch a lecture online.The Angels & Demons Virtual Lectures page features videos, audio, and PDFs of more than one dozen lectures.So sit back, relax, and learn about antimatter, the Large Hadron Collider and the excitement of particle physics in the comfort of your own home. (Popcorn not included.)
Bill Gates recently bought the rights to a series of lectures by legendary Caltech physicist Richard Feynman. The former Microsoft head’s purchase shows that the cultural and scientific legacy of Feynman remains strong even 21 years after his death.
The lectures, given in 1964 as part of Cornell University’s Messenger Lecture Series, were filmed by the BBC, who had retained the rights since. Gates purchased the lectures for an undisclosed amount.
But what would the former Microsoft head want with the copyright to lectures by the revered physicist? In a recent interview with the CERN Bulletin, Gates said that his only plan is to make the footage freely available to the public.
Add to that Gates’ reverence for Feynman, and it makes sense. The lectures are only the latest addition to Gates’ personal collection of Feynman-related material, which includes original manuscripts of some of Feynman’s best known work.
“I have heard that Gates really respects and admires Feynman. They exchanged a few calls back in the 1980s,” said author and cognitive neuroscientist Al Seckel, who became a close friend and student of Feynman’s.
Feynman is perhaps best known for his series of autobiographical books and for the transcriptions of lectures he gave as a faculty member at Caltech, The Feynman Lectures on Physics.
California-based photographer Joe Decker, who took several classes from Feynman while studying for a mathematics degree at Caltech, remembers Feynman as being unparalleled as a teacher.
“Feynman had an uncanny ability to convey the essence of an idea,” Decker said. “That, in addition to his incredible abilities of storytelling…was why he was so incredibly loved.”
Although Gates has yet to announce how the lectures will be made available, anyone too anxious to wait can catch segments on YouTube. The lectures are also available in Feynman’s book The Character of Physical Law.
On the cover:
As symmetry celebrates its 50th issue, big changes are afoot at Fermilab.
The lab’s Tevatron Collider, once the most powerful particle collider in
the world, is shutting down, and a new project is on the horizon: Project X.
This proposed $1.8 billion accelerator complex would keep Fermilab at
the forefront of high-energy physics, this time at the Intensity Frontier—a realm
in which scientists bring incredible numbers of particles into collision to
search for extremely rare processes with a big physics impact. It’s exactly
the kind of place where discoveries may lie. See “Solving for X”.
Photo illustrations: Reidar Hahn, Fermilab and Sandbox Studio
