International committee maps future of particle physics

October 4, 2011 | 1:06 pm

Image from the "Beacons of Discovery" report, by Reidar Hahn.

This week an international organization made public their vision for the future of particle physics across the globe. The International Committee for Future Accelerators have placed on the web their report, “Beacons of Discovery.”

“Beacons of Discovery” lays out the basics of what particle physicists know, what questions they are asking and what experimental tools they are using to answer them.

The report underscores that modern particle physics is more than the hunt for the famous Higgs boson. Today physicists Saul Perlmutter, Brian Schmidt and Adam Riess received the 2011 Nobel Prize in Physics for a discovery that led to another of today’s biggest questions in particle physics: What is dark energy? The Nobel Committee chose to honor the three men for the discovery that the universe is expanding at an accelerating rate. Physicists had previously assumed the force of gravity would slow the expansion of the universe, potentially reversing expansion into retraction. Using exploding stars as markers, scientists found that the expansion was actually getting faster. This led physicists to conjecture that another force is working against gravity to push galaxies apart.

Modern physicists use three types of experiments in their searches for dark energy, the Higgs and other phenomena: those at the energy, intensity and cosmic frontiers. As “Beacons of Discovery” explains, at the energy frontier, physicists use machines to collide particles at high energies. The Large Hadron Collider recently became the main focus of physicists at the energy frontier with the shutdown of its predecessor, the Tevatron. At the intensity frontier, physicists use intense beams of particles to study rare processes, such as the neutrino interactions that recently caused such a stir at the OPERA experiment. At the cosmic frontier, physicists use the cosmos as a laboratory to observe processes, many of which they cannot replicate on Earth. Many searches for evidence of dark matter and dark energy use data from events in space.

Finally, “Beacons of Discovery” explains how the study of particle physics will continue to benefit society, providing for the needs of those in hospitals, industry, schools and the community.

Kathryn Grim

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Astronomers win Nobel Prize in Physics for discovering the accelerating expansion of the universe

October 4, 2011 | 12:53 pm

The 2011 Nobel Prize in Physics has been awarded to three scientists: Saul Perlmutter, Brian Schmidt and Adam Riess. Their observations of distant exploding stars led them to the startling discovery that the expansion of the universe is accelerating. This discovery laid the groundwork for the idea that a mysterious force called dark energy, which makes up 75 percent of the universe – yet has never been detected – is fueling the acceleration.

Perlmutter, a researcher at Lawrence Berkeley National Laboratory and the University of California, headed the Supernova  Cosmology Project, which began observations in 1988. Schmidt, of the Australian National University, started the High-Z Supernova Search Team in 1994; it was later joined by Riess, of Johns Hopkins University and the Space Telescope Science Institute, who played a crucial role in the observations.

Between them, the two teams found more than 50 supernovae whose light was weaker than expected – an indication not only that the universe was expanding, as had been expected, but that it was expanding ever faster. The discovery came as a complete surprise, even to the discoverers, and its announcement in 1998 profoundly shook our view of the universe.

“I’m thrilled for Adam, Brian and Saul and the teams they have led,” said Roger Blandford, director of the Kavli Institute of Particle Astrophysics and Cosmology at SLAC National Accelerator Laboratory. “It was a great discovery, and it’s looking like a vindication of the original proposal Albert Einstein made 94 years ago.”

More news at …

Nobel site: http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/

CNN: http://www.cnn.com/2011/10/04/world/europe/sweden-nobel-physics

Real-time blog at Guardian UK: http://www.guardian.co.uk/science/blog/2011/oct/04/nobel-prize-physics

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EXO releases first results

September 9, 2011 | 10:54 am

SLAC published this article on Sept. 8, 2011.

Cooks think of watched pots. Handymen grumble about drying paint. Kids dread the endless night before Christmas morning.

SLAC engineer Knut Skarpaas with half of the EXO 200 detector.

Turns out physicists have their own expression to convey the concept of “slow,” and now, thanks to the Enriched Xenon Observatory (EXO), they know how slow “slow” really is: The flurry of activity during the 13.75 billion years from the Big Bang to us was positively hasty in comparison.

The expression is “2nubb” and it stands for “two-neutrino double-beta decay”, a rare type of particle decay undergone by certain forms of radioactive elements. In this type of decay, two neutrons, the neutral subatomic particles in the nucleus of an atom, spontaneously decay into two protons, two electrons, and two antineutrinos, which are the antimatter twins of the tiny, nearly massless mystery particles called neutrinos. The EXO team announced yesterday at a conference in Munich that, according to their measurements of two-neutrino double-beta decay in Xe-136, an isotope of xenon, the half-life of the process clocks in at 2.11 x 10²¹ years. In other words, it would take 100 billion times longer than the universe has even existed for half of a sample of this radioactive isotope to decay via the 2nubb decay pathway.

“This represents the slowest Standard Model process ever measured,” said Giorgio Gratta, Stanford University physicist and member of the joint SLAC-Stanford Kavli Institute for Particle Astrophysics and Cosmology, who leads the team. The Standard Model is the best description scientists have for the way all the building blocks of matter, like the aforementioned neutrons, protons and electrons, fit together, and why two-neutrino double-beta decay happens in the first place.

Two-neutrino double-beta decay fits neatly within the Standard Model, “so in this sense the observation was not unexpected,” Gratta said. In fact, this form of decay has been seen before in other elements. “In that sense, it is not even new.”

Even so, the team’s results mean much more than a shot at the Guinness Book of World Records.

The EXO 200 detector is the first to capture the 2nubb decay process in Xe-136, for example, and the measurement is based on little more than a month of data – “remarkably clean” data, with very little interference from background noise, Gratta explained. This solid signal has provided valuable data to theorists, enabling them to resolve puzzling discrepancies between their calculations and the results of previous experiments.

But the experiment is far from over, and the speed and clarity of these early results bode well for the team as they go after their real quarry.

What the EXO 200 team wants to find is another decay process – one that is not only even more fantastically rare than 2nubb, but that no one is certain even exists. It’s called zero-neutrino double-beta decay, or 0nubb, and it is decidedly not a Standard Model process.

In 0nubb, two neutrons once again decay into two protons and two electrons, but the antineutrinos are nowhere to be found. They must have been there; the IRS has nothing on Nature for keeping the books balanced. The two antineutrinos must have annihilated each other, like positrons and electrons can annihilate each other, or protons and anti-protons, or any particle and its antiparticle.

This means in order for 0nubb decay to happen, neutrinos must be their own antiparticles.

Odd as this sounds, the possibility of a particle that could be both itself and its anti-self was hypothesized by an Italian theoretical particle physicist named Ettore Majorana in 1937. Such particles are called Majorana particles, and if they exist physicists would need to get busy revising the Standard Model.

“This is a decay that people have been trying to find for a long time,” Gratta said.

“Zero-neutrino double-beta decay would be a big deal,” agreed Marty Breidenbach, SLAC physicist and EXO team member. He explained how the EXO 200 experiment intends to pursue such a prize. It all comes down to distinguishing between something that’s nearly impossible to see because of its rarity and something that’s clearly impossible to see because it may not even exist.

The team’s chief strategy is to give the 0nubb decays as many opportunities to happen and as few places to hide as possible. A detector chamber filled with 200 kilograms of liquid xenon takes care of the first strategic objective – the xenon has been enriched until it’s 80 percent Xe-136, the double-beta decaying isotope – but the second one is a bit tougher.

In order to make sure they’ll recognize 0nubb – or even 2nubb – decays, the team has had to cut out every other source of radioactivity they could. The equipment, made of ultrapure, ultraclean, non-radioactive materials, was constructed at Stanford University and trucked, not flown – flying would expose it to more cosmic rays – to the Chihuahuan Desert near Carlsbad, New Mexico, where it was installed about a half-mile underground in the salt bed used by the Waste Isolation Pilot Plant, the Department of Energy’s repository for nuclear waste. The choice seems odd, but the reasoning was sound. The same salt that keeps radioactivity from nuclear waste trapped in the repository keeps radioactivity from cosmic rays and decaying rocks out of the EXO 200 detector.

As the low background readings in their initial results show, the EXO 200 strategy seems to be working. According to Breidenbach, the experiment will continue to take data for several years, possibly as many as five, depending on progress with what’s called “full EXO,” an experiment using several tons of Xe-136 that’s currently in development.

“EXO 200 was always intended as a pilot project,” Breidenbach said. “We’re actively doing R&D for full EXO.”

In the meantime, there’s no moss gathering on the EXO collaboration. EXO 200 has already made its mark.

- Lori Ann White

The EXO collaboration comprises researchers from the following institutions: Department of Physics and Astronomy, University of Alabama, Tuscaloosa AL, USA; LHEP, Albert Einstein Center, University of Bern, Bern, Switzerland; Kellogg Lab, Caltech, Pasadena CA, USA; Physics Department, Carleton University, Ottawa ON, Canada; Physics Department, Colorado State University, Fort Collins CO, USA; Physics Department and CEEM, Indiana University, Bloomington IN, USA; Institute for Theoretical and Experimental Physics, Moscow, Russia; Physics Department, Laurentian University, Sudbury ON, Canada; Physics Department, University of Maryland, College Park MD, USA; Physics Department, University of Massachusetts, Amherst MA, USA; Department of Physics, University of Seoul, Seoul, Korea; SLAC National Accelerator Laboratory, Stanford CA, USA; Physics Department, Stanford University, Stanford CA, USA; Technical University Munich, Munich, Germany; Waste Isolation Pilot Plant, Carlsbad NM, USA.

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Turning data into wild rides through dark domes

July 7, 2011 | 2:57 pm

Ralf Kaehler, right, and Ji-hoon Kim of KIPAC stand before a snapshot of a large-scale reionization simulation. The blue regions indicate hot, ionized hydrogen gas. (Photo by Brad Plummer.)

From their seats in the Morrison Planetarium at the California Academy of Sciences in San Francisco, visitors swoop through a redwood forest, into a single redwood leaf and finally into an individual cell to watch photosynthesis take place. Then they travel back billions of years to watch the first stars wink on, heat up and explode, scattering into space many of life’s essential chemical elements.

The point of the show, “Life: A Cosmic Story,” narrated by Jodie Foster, is that the connections between living things go all the way back to the distribution of dark matter in the early universe;  its gravitational influence allowed the formation of galaxies, stars and  planets.  Unlike shows of a decade ago, all the animations of things we can’t see are based on real scientific data – including visualizations made by researchers at KIPAC, the Kavli Institute for Particle Astrophysics and Cosmology, at SLAC National Accelerator Laboratory and Stanford University.

“Rather than relying purely on artistry and artwork to communicate the science, it’s going to the scientists and using the same data they’re using to create visuals,” said Ryan Wyatt, who directs Morrison Planetarium and the science visualization staff at the California Academy of Sciences. “To my mind that’s incredibly valuable. It’s authentic. It allows people to experience the science in a way they probably can’t do elsewhere.”

This is the third planetarium show that KIPAC scientists Ralf Kaehler and Tom Abel have collaborated on, and the fifth for Abel. “Life” at the Morrison features their animation of the birth and death of the earliest stars, an area in which Abel is a world expert.  A similar visualization appears in “Journey to the Stars,” narrated by Whoopi Goldberg, now playing at New York City’s Hayden Planetarium.  The team also contributed to a show narrated by Liam Neeson that welcomes visitors to the Hayden. For that, they put together a sequence that shows massive galaxies in the early universe colliding, merging and spinning away from each other.

Often created from simulations that scientists have run as part of their research, these visualizations are “kind of a byproduct of this work,” Kaehler says. “And it’s a great way of doing public outreach.” The pair’s work has appeared in books, newspapers, TV shows, exhibits and magazines–including, in February 2003, the first computer-generated image on the cover of National Geographic. 

Science-based planetarium shows are the latest advance in a tradition that dates back centuries. The first attempts were hollow globes, big enough to let a few people inside, pricked with holes to let “starlight” in.  About 85 years ago, the first modern planetarium opened in Munich; a light projector made by the Carl Zeiss Co. splashed starlight onto the dark, concave surface of the dome. Soon planetariums were springing up by the hundreds – from small ones used for teaching to large domes that seated hundreds of people. For many visitors, the technology provided their first glimpse of a truly dark sky, undimmed by city lights. 

In 2000, the opening of the new Hayden Planetarium at the American Museum of Natural History showcased a major leap in technology: The first show based on visualizations of real scientific data. Observations of the locations and brightness of more than 100,000 stars came from the European Space Agency’s Hipparcos satellite. Data on 45,000 galaxies came from an astronomer at the University of Hawaii. And data collected over the years on the Orion Nebula, a giant gas cloud studded with newborn stars, allowed visitors to fly through a stunning 3-D version of the nebula as if on magic carpets.
 

A visualization of a massive star in the early universe. The highly-energetic ultraviolet emissions from the star ionize the gaseous material in its neighborhood. (Visualization: Ralf Kaehler (KIPAC/SLAC) and Tom Abel (KIPAC/Stanford))

Presenting that show required a Silicon Graphics Onyx2 supercomputer, said Wyatt, who worked at the Hayden before joining the Morrison Planetarium. With the huge increases in computing power over the past decade, it can now be done with seven desktop computers.

Planning and developing a planetarium show can take anywhere from 16 months to two years.  For Abel and Kaehler, the process may start six months before the show is slated to go public, with a request for a visualization that will tell a story spanning billions of years in the space of a minute or two.

Abel, an associate professor of physics at SLAC and Stanford, leads KIPAC’s Computational Physics Department and specializes in creating numerical simulations – computer models based on scientific data and complex equations that describe the laws of physics.  Simulations have become a valuable tool – a sort of third arm of science, alongside theory and experiment – for understanding how nature works, allowing researchers to grasp patterns that are otherwise hidden inside reams of data.

A simulation of how the first stars formed might start with a map of the cosmic microwave background radiation, which has been measured in great detail by spacecraft. Scientists think these tiny variations in the energy left over from the big bang provided the gravitational seeds around which stars and galaxies formed.

The simulation software, which usually runs on large computer clusters, divides an enormous region of space, up to hundreds of thousands of light years across, into cubes. Within each of those cubes the software calculates physical quantities, such as the density, temperature, and velocity of hydrogen gas, Kaehler said. Then it divides those cubes into even smaller ones, identifies the regions where stars are most likely to form, and does another round of calculations. This is repeated until the simulation has zoomed in close enough to the star-forming regions to capture all the relevant physics with sufficient accuracy.

A test-rendering of galaxies merging for a show at the Big Bang Theatre in the Hayden Planetarium. Visualization: Ralf Kaehler (KIPAC/SLAC) and Tom Abel (KIPAC/Stanford). Simulation: Ji-hoon Kim (KIPAC).

But that still doesn’t give researchers a picture – just millions and billions of computer-generated numbers.  It’s the job of Kaehler, a research software developer at KIPAC, to turn those numbers into visualizations – both stills and animations – that allow the viewer to grasp what’s happening in a clear and intuitive way.

This involves a lot of software engineering, he said.  “Since we’re building all our 3-D visualization software from scratch, we can tailor everything just the way we need it.  Writing the code is a lot of work, but it also gives us a lot of freedom.”  Among other things, the visualization has to take into account what path the camera will take through the 3-D world the scientists have created, and what colors that world is painted in.

For “Life: A Cosmic Story,” the scientists worked closely with the Academy’s production staff, whose members   could claim a combined total of 120 years of visualization experience, Wyatt said. Kaehler and Abel, he said, “bring their technical savvy and scientific background, and work with our visual sensibilities.”

The Morrison Planetarium draws about 750,000 visitors per year, Wyatt said, and he is working to make “Life” available to the estimated 700 to 800 other planetarium domes that are capable of playing it.  As the show makes it way out into the expanding universe of planetarium fans, it may turn out that Abel and Kaehler’s outreach efforts have a very long reach indeed.

Glennda Chui

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TAUWER aims for cosmic heights

June 16, 2011 | 2:25 pm

The origin of ultra-high-energy cosmic rays is a question that makes it onto many top-unsolved-problems-in-physics lists.

The TAUWER experiment looks at particle showers that originate from tau neutrinos that take short paths through the earth (inset). An ideal site to observe these events is a mountain bowl. Image courtesy of Maurizio Iori.

The math says that these particles, which carry in excess of 10¹⁹ electron volts, or eV,  from somewhere in outer space, are far too energetic not to have interacted themselves out of existence before reaching the earth. And yet every year scientists see evidence in the earth’s atmosphere of a handful of these particles, which have several million times the energy of the protons being collided at the Large Hadron Collider.

Scientists are proposing a new experiment, called TAUWER, that would look to tau neutrinos to remove some of the mystery from these strange, over-stimulated cosmic rays.

“The question is, how do they get this energy?” says James Russ, TAUWER collaborator and professor of physics at Carnegie Mellon University. “We don’t know what the mechanism is.”

One idea for the mechanism is a rapid rebounding between plasma shock waves. In places such as those near black holes, where charged matter builds to extreme densities, protons may be ricocheting back and forth between shock wave fronts, accelerating and gathering energy over billions of years. Then one day the proton may escape and come to earth in the form of an ultra-high-energy cosmic ray or UHECR.

If these UHECRs are indeed protons escaped from star systems, they’ll reveal their existence, through a series of interactions, by producing ultra-high-energy neutrinos, neutrinos with energies greater than 10¹⁶ eV—over a billion times more energetic than those produced by supernovas.

TAUWER detectors would examine the particle showers brought on by these neutrinos’ interaction with the earth. The resulting energy measurements of the tau neutrinos could give scientists information about their conjectured parents, the UHECR protons.

“The neutrinos’ energy spectrum tells you about the nature of the protons’ acceleration,” Russ said. “That’s why it’s an interesting measurement to make.”

Collaborators are interested in particular in tau neutrinos – one of three known types – because of the high chance they’ll end up propagating particle showers that their detectors can see.

Rough layout scheme of TAUWER detectors on a mountainside. The straight blue line represents a tau lepton emerging from the earth. The white lines represent shower tracks from the tau lepton decay. Image courtesy of Maurizio Iori.

TAUWER isn’t the only program that’s using neutrinos to get to cosmic rays. The IceCube experiment at the South Pole looks for lower-energy neutrinos as they barrel through the length of the earth’s diameter with energies of up to 10¹⁶ eV. IceCube experimenters are currently busy with creative new schemes to extend their energy reach.

TAUWER picks up where the present IceCube design leaves off. Neutrinos with higher energies may not be able to make it from one end of the planet to the other since they’ll very likely be derailed by the rock in the earth. But if the trip through the earth is short enough, they can still make their way out.

TAUWER detectors would turn their attention particles that fly through short slices of the planet, about 1/13 the diameter of the earth. The neutrinos could, for example, enter San Francisco Bay and, a thousand kilometers later, exit Salt Lake. During these split-second trips through the earth, the ultra-high-energy neutrinos’ interaction with the rock would be close enough to the earth’s surface that its offspring, a tau lepton (a heavy cousin of the electron) could still push its way from beneath the ground into the air. TAUWER detectors, pointed at some angle toward the earth, will see the 1-kilometer-radius particle shower that springs from the tau lepton’s connection with the atmosphere.

The detectors, which have a very high pointing accuracy, can then pick out the direction of the UHECR that started it all. And with enough tau neutrino data, the UHECR phenomenon could very well lose its place on the top-unsolved-problems list – a good thing.

The Pierre Auger experiment in Argentina has also been on a quest to catch glimpses of UHECRs by way of tau neutrinos, but using very different methods. Auger detectors look for UHECRs that come uninterrupted from the sky. TAUWER detectors, on the other hand, would watch the ground to find tau neutrinos that come from below. Russ imagines TAUWER detectors searching for neutrino events from the height of a mountainside. The collaboration is scouting mountain bowls, sites where mountain ridges surround level stretches of land, in Europe, Mexico, and the US.

“A mountain bowl has the lovely feature that it screens horizontal cosmic rays, which are one background source,” Russ said. “You’re sitting on a mountain range that’s looking down on a nice flat space for neutrinos to come up through.”

The collaboration is currently testing a handful of detectors. Once the experiment is running full speed ahead, they’ll run 2,500 small detectors, each about as tall and wide as a CD case. Grouped in fours and spaced about 70 meters apart, the detectors will help map the energy spectrum of tau neutrinos that plow through the earth.

TAUWER collaborators are currently based at Carnegie Mellon University, Sapienza University of Rome and two Turkish institutions in the Bolu and Kars provinces. The TAUWER name is a nod both to the tau neutrino and to the aluminum frames – towers – that support the experiment’s instruments.

“By next summer, we should be ready to find more interested people who want to take on the ice and snow of a mountain environment to help make things work,” Russ said.

Leah Hesla

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Bob’s most excellent particle detector adventure

June 13, 2011 | 12:02 pm

One month ago, Fermilab’s Bob Peterson embarked on a month-long journey in the Atlantic Ocean with two cosmic ray muon detectors, collecting data for science and education programs. This offers a chance to study how cosmic ray recordings differ on land and sea and at different latitudes. The data will be accessible to high school students and teachers in several countries who use similar detectors to learn about particle physics. Bob recorded the entire adventure, which concluded last week, in Quantum Diaries. He posted the following entry on May 12, just as his ship was about to pass the equator.

Enduring a branding for QuarkNet science education

Bob Peterson holds part of the electronics for the cosmic ray muon detector. Credit: Tona Kunz

4 May 2011
R/V Polarstern
Latitude: 9-47.1 N
Longitude: 19-46.2 W
off the coast of Guinea
Ship course 320 ° T
Ship velocity 10.1 knots

4 May 2011:
Two days ago, the R/V Polarstern stopped mid-ocean at latitude: 00-00.053S, longitude: 11-39.259W.

By my reckoning, that’s 318 feet south of that east-west line “painted” in the water. Guilty parties were forced into very little rubber rafts and pointed in obscure directions and told to “cross the line”. Only one actually knew which way to go. After circular paddling, which amounted to three times the distance required to cross the line, those guilty of being equator-crossing newbies were initiated as shellbacks .

And what an initiation it was.

Neptune, lord of the sea, and his court rose up out of the Atlantic for the ritual baptism of those who had violated his domain. A trial was held and renaming of the pollywogs was required. Much fun and antics was had by the entire crew as they put on a real show of cruel and dastardly deeds. I could almost hear them cackling like the pirates of days past: “Arrrghhh! Avast ye maties!”

Bathing in stinky slop ensued, ceremonial memorizing of creeds was demanded and kissing of the feet of Neptune’s wives was enjoyed. Men in drag wearing clown shoes slathered in mustard and horseradish sauce stood in for Neptune’s wives. Lovely. I was also assisted by large, burly men with tattoos into a baptismal font made from a large fish basket. Four times I went in it; I must have been extra sinful. Each dunking got nastier as more people were “baptized”.

Finally they branded our stomachs with Neptune’s trident. This was a bit scary because they covered our faces with hoods execution-style and we could hear the metal trident heating in a charcoal grill and sizzling as it pressed onto flesh. Thankfully, when it came to my turn I found out the sizzle was the trident branding a raw piece of meat that then got slapped onto my stomach.  The crew got a great laugh out of our initiation.

We earned certificates for our ceremonial passage and a feast at sunset. Neptune felt the ceremony was befitting and left without taking the ship with him. So I am now the shellback known as Cosmic-Ray Rider, and I have pictures and a certificate to prove it.

Those will have to do because I skipped one of the most permanent parts of the ceremony. While I appreciate all the suggestions of earring types from friends and family, I decided to forego that little ritual. It’s the burly men that punch the hole, and they’re none too delicate.

So, the cosmic ray muon detector gave me my shellback name, but it’s also been my source of grief. Sometimes delicate instruments refuse to cooperate. For me, the trouble has been channel four and a scintillator counter that drops off line. Of course, it’s the one on the bottom of the stack, and it chooses to act up in the middle of the night. Several times in the morning I find it asleep, and that no data was taken during the night. Suspecting a light leak, I rewrapped it twice. Nope; that’s not it. Then I discover a flakey wire into the photo multiplier tube. There must be a short inside that photo multiplier tube. To compensate, I have lowered the coincidence to 3-fold from four so that a particle signal recorded in the three working sections of the detector will count as cosmic ray remnant event. Now, I will at least get some data. A replacement wire is some 8,000 miles away at Fermilab and the parts you can find along our route are pretty wet wheeling, as they say.

After many days in the southeast trade winds, we pushed through the doldrums, an area of still air near the equator that seems to rise rather than blow, and into the northeast trade winds. Other than the stop for the equator crossing, our course and speed have been relentless: 320 ° T, 11 knots; however, the following winds and swell have now turned on the nose and have become quite lumpy. Max, the weather guesser, promises it will get worse. In several days we make a turn to the north and a planned stop at the Canary Islands to pick more scientists.

Glossary:
*Pollywog: Some no good, inexperienced mariner who has never crossed the equator.

*Shellback: The opposite of a pollywog.

*Coincidences: The cosmic ray muon detector looks for what we call coincidences, two signals, one from each photo multiplier tubes, received within a short time. These are reported to the computer; all other signals are vetoed as likely background noise from the photo multiplier tubes.

– Bob Peterson

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The AMS detector heads for the International Space Station

April 27, 2011 | 11:50 am

The following press release was issued today by CERN.

The AMS particle detector on the space Shuttle Endeavour. Credit: Michele Famigliett

Geneva 27 April 2011. The AMS particle detector will take off on 29 April 2011 at 21.47 CEST onboard the very last mission of the space Shuttle Endeavour. AMS, the Alpha Magnetic Spectrometer, will then be installed on the International Space Station from where it will explore the Universe for a period of over 10 years. AMS will address some of the most exciting mysteries of modern physics, looking for antimatter and dark matter in space, phenomena that have remained elusive up to now.

In laboratories like CERN, physicists observe matter and antimatter behaving in an almost identical way. Each matter particle has an equivalent antiparticle, very similar but with opposite charge. When particles of matter and antimatter meet, they annihilate. Matter and antimatter would have been created in equal amounts at the Big Bang, yet today we live in a Universe apparently made entirely of matter. Does nature have a preference for matter over antimatter? One of the main challenges of AMS will be to address this question by searching for single nuclei of antimatter that would signal the existence of large amounts of antimatter elsewhere in the Universe. To achieve this, AMS will track cosmic rays from outer space with unprecedented sensitivity.

“The cosmos is the ultimate laboratory,” said Nobel laureate and AMS Spokesperson Samuel Ting. “From its vantage point in space, AMS will explore such issues as Antimatter, Dark Matter and the origin of Cosmic Rays. However, its most exciting objective is to probe the unknown because whenever new levels of sensitivities are reached in exploring an unchartered realm, exciting and unimagined discoveries may be expected.”

In the same way that telescopes catch the light from the stars to better understand the Universe, AMS is a particle detector that will track incoming charged particles such as protons, electrons and atomic nuclei that constantly bombard our planet. By studying the flux of these cosmic rays with very high precision, AMS will have the sensitivity to identify a single antinucleus among a billion other particles.

“This is a very exciting moment for basic science,” said CERN Director General Rolf Heuer. “We expect interesting complementarities between AMS and the LHC. They look at similar questions from different angles, giving us parallel ways of addressing some of the Universe’s mysteries.”

AMS may also bring an important contribution to the search for the mysterious dark matter that would account for about 25% of the total mass-energy balance of the Universe. In particular, if dark matter is composed of supersymmetric particles, AMS could detect it indirectly by recording an anomaly in the flux of cosmic rays.

“Never in the history of science have we been so aware of our ignorance,” said AMS Deputy Spokesperson Roberto Battiston. “Today we know that we do not know anything about what makes up 95% of our Universe.”

AMS is a CERN recognized experiment and as such has benefited from CERN’s expertise in integrating large projects, from CERN’s vacuum and magnet groups and from test beam facilities for calibrating the detectors. In addition, the Payload Operation Centre (POC) of AMS will open in June 2011 at CERN, very near to the place where the AMS detector was assembled in clean room facilities. From the POC, physicists will be able to run the AMS detector as well as receive and analyse data arriving from the International Space Station.

AMS is the result of a large international collaboration with a major European participation. It is led by Nobel laureate Samuel Ting and involves about 600 researchers from CERN Member States (Denmark, Finland, France, Germany, Italy, the Netherlands, Portugal, Spain, Switzerland) as well as from China, Korea, Mexico, Taiwan, and the United-States.

Follow the launch of AMS live:

The launch of AMS can be followed live via webcast at: http://webcast.cern.ch
Questions can be asked during the webcast by sending them to @cern on twitter

The live will also be broadcasted through EBU Eurovision services.
A VNR preview will be broadcasted on 28 April 2011, 10:00 – 10:15 GMT.
More information on http://www.eurovision.net/

Videos are available at: http://bit.ly/cernamsfootage
Videos are subject to the CDS conditions of use: http://bit.ly/CDSconditionsofuse

For updates about of AMS, follow @astroparticle and @ams_02

Information about AMS can be found at www.ams02.org

Elizabeth Clements

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Dark Energy Camera ready for shipping to Chile

April 16, 2011 | 10:41 am

This story first appeared in DOE Pulse on April 4.

A replica ring of the top-end of the Blanco telescope allowed technicians at Fermilab to test the installation of a 570-megapixel camera and check how camera parts would function as the telescope rotates. This testing significantly reduces the amount of telescope down time that will be required during the assembly in Chile.

Building and installing one of the world’s largest digital cameras to solve the mystery of dark energy requires the collaboration of scientists and industry from across the globe. The Dark Energy Survey’s combination of survey area and depth will far surpass the scope of previous projects and provide researchers for the first time with four search techniques in one powerful instrument. More than 120 scientists are collaborating to determine the true nature of dark energy, the mysterious force that accelerates the expansion of the universe. Taking images of galaxies from the time the universe was only a few billion years old, the DES will trace the history of the expanding universe roughly three-quarters of the way back to the time of the Big Bang.

But first researchers needed to build the 570-megapixel camera at DOE’s Fermi National Accelerator Laboratory and make sure it works. Nearly all of the camera’s parts made their way to Fermilab for assembly and testing during the last 12 months. The components were assembled and operated on a full-size replica of the front end of the 4-meter Blanco telescope in Chile, built by Fermilab and Argonne National Laboratory.  Testing finished successfully in February. During the next few months, physicists will be putting the finishing touches on pieces of the camera and shipping them to the Cerro Tololo Inter-American Observatory in Chile where they will receive another round of tests before installation.

The high-tech supply chain tapped the expertise at four DOE Office of Science national laboratories and more than two dozen institutions and universities in the United States and abroad.  More than 120 companies in the United States contributed know-how and parts. Fermilab took the lead in the assembly and testing of the camera and building a cryogenics system several times larger than those used in previous ground-based sky surveys, while Berkeley and Argonne national laboratories played key roles in the camera development.

Berkeley Lab developed the Charge Coupled Devices used in the camera and did some of the processing of the silicon for the CCDs before sending the pieces to Fermilab for packaging of CCD chips. The unique design of these CCDs will give the camera unprecedented sensitivity for red and near-infrared wavelengths, allowing it to record more light for a given exposure time. The camera contains 62 CCDs for observing with 8 million pixels each, plus 12 CCDs with 4 million pixels each for guiding and focusing.

Argonne National Laboratory helped construct the calibration camera to conduct a mini-sky survey last year from a telescope adjacent to the Blanco telescope. This scaled-down version of the dark energy camera allowed for testing of the experiment hardware, software and observing strategies as well as created a baseline of celestial objects for Dark Energy Survey. Argonne also constructed several smaller components for the full-size camera and some large mechanical systems, including the heavy apparatus that installs and removes a 1-ton mirror from the front of the camera.

SLAC National Accelerator Laboratory took the lead in constructing a separate, small telescope with an infrared camera that will sit on a mountain near the Blanco telescope in a separate enclosure. This telescope will monitor cloud coverage so that the Dark Energy Camera can adapt its survey modes to various atmospheric conditions.

The DES collaboration expects to take its first astronomical images with the installed Dark Energy Camera before the end of 2011.

Tona Kunz

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Particle physicist lends skills to planet hunt

February 4, 2011 | 2:11 pm

Artist's illustration of Kepler spacecraft. Credit: NASA/ Kepler Mission/ Wendy Stenzel.

You don’t normally think of high-energy physicists working with NASA to find planets that humans could live on. Working on the Large Hadron Collider or dark-energy-seeking telescopes, yeah, but, planet hunting? Not so much.

Yet, Jason Steffen, an astrophysicist at Fermilab, is a long-time member of NASA’s Kepler Mission and its only practicing  particle physicist. He helped make possible the mission’s discoveries announced Wednesday of a six-planet solar system 2,000 light years away, tits first Earth-sized planet candidate, and the first such candidate that potentially could support human life.

It’s one small step for Steffen and his Kepler collaborators and one giant step for dreamers everywhere.

“In one generation we have gone from extraterrestrial planets being a mainstay of science fiction, to the present, where Kepler has helped turn science fiction into today’s reality,” says NASA administrator Charles Bolden upon announcing the data release.

The Kepler spacecraft-mounted telescope, 11 million miles from Earth,  scans the sky to find, for the first time, distant life-sustaining planets the size of Earth.  Telescopes can’t directly spot planets smaller than Jupiter, but Kepler uses starlight to indirectly see smaller planets. Planets that could potentially sustain life fall into a Goldilocks-like “habitable zone,” orbiting the perfect distance from a star like our sun so as to not be too hot or too cold. Often these planets’ orbits cross close in front of a star, or “transit,” making them visible through the blinking out of the stars’ light.  By measuring the brightness change of a star as a planet passes in front of it, as well as  the time between these transits, scientists can tell the planet’s size, orbit, and estimated temperature.

But the closeness to the star that allows Kepler to “see” the planet also often makes it too hot for life. The more distant planets outside Kepler’s view hold a greater chance of being just right to sustain life. Kepler has difficulty spotting these planets because of orbit cycles that are longer than the time frame of the released data or because they do not transit stars.

That’s where Steffen comes in.

Jason Steffen

“We are sensitive to planets that Kepler can’t see directly,” says Steffen of the analysis team he leads. “That is where it gets interesting.”

He helped pioneer a search method that can detect distant planets more than 600 times smaller than Jupiter and out of range of Kepler‘s telescope. He uses computerized mathematical procedures, called algorithms, including many that are commonplace to particle physics, to probe deeper into space in the area around a planet Kepler sees to find planets in that often cooler, more habitable zone.

This is done by studying the amount of time it takes a planet to complete its orbit past a star. Deviations from a constant orbit time  indicate the presence of some additional unseen planet whose gravitational pull is changing the orbit speed of the observed planet. This technique is used to confirm that distant images seen by the Kepler telescope are planets and not pairs eclipsing binary stars blurred by the telescope to resemble an object of planet size.

Steffen expects to look at hundreds of planetary systems during the mission’s 3 ½ years. By looking at patterns in the times it takes planets to transit, scientists could fill in some blanks about how planetary systems form with relation to their distance from a sun.

The discoveries announced Wednesday are part of several hundred planet candidates identified in new Kepler mission science data release. The findings increase the number of planet candidates identified by Kepler to date to 1,235. Of these, 68 are approximately Earth-size; 288 are super-Earth-size; 662 are Neptune-size; 165 are the size of Jupiter; and 19 are larger than Jupiter. Of the 54 new planet candidates found in the habitable zone, five are near Earth-sized. The remaining 49 habitable-zone candidates range from super-Earth size — up to twice the size of Earth — to larger than Jupiter.

The findings are based on the results of observations conducted from May 12 to Sept. 17, 2009, of more than 156,000 stars in Kepler’s field of view, which covers approximately 1/400th of the sky.

Based on this large data sample “….it turns out that close to 20 percent of all stars are orbited by
planets, meaning that a significant fraction of the stars in the sky are orbited by alien worlds,” says Tim Brown, Kepler co-investigator and physics professor at the University of California Santa Barbara, in a press release.

Just as Kepler collaborators look  for a planet that is just right for habitation, the group also needed just the right skill set to expand its search reach. Steffen happened to be one of the only people in the world versed in that area of research because of his graduate degree work in transit timing variations.

NASA to note and asked him to join the Kepler mission as a participating scientist, collaborators drawn from outside the normal NASA research field to to enable the team to more effectively execute the mission’s science program.

Steffen and his thesis advisor Eric Agol, associate professor of astronomy at the University of Washington, fine-tuned this method of tracking fluctuations in the orbits of planets, making it unexpectedly useful for short-time mission such as Kepler’s planet hunting.

Scientists had tracked orbit fluctuations before but always on the time scale of comparing  many thousands of orbit cycles during the course of many decades. Using smaller data sets taken during shorter periods of time seemed pointless because they generated such small effects–until Steffen and Agol came along.

By introducing a  new tracking method, they reduced the time needed to identify these hard-to-find planets to a year with only a dozen or two orbit cycles.  Matt Holman, an astronomer with the Harvard-Smithsonian Center for Astrophysics, had also been focusing on the same problem. The two joined together to adapt their tracking methods, along with help from colleagues across the country, for the Kepler exoplanet hunt.

This work with exoplanets doesn’t have direct applications to high-energy physics or Steffen’s other work at Fermilab on chameleons, axion particles, and holographic noise. However, particle physics uses many of the same mathematical algorithms in experiments and there is no telling whether Steffen’s technique could become useful in that field in the future.

“It’s fair to say I can cannibalize the components of the algorithm for future projects,” Steffen says.

–Tona Kunz

For more information:

Kepler mission website

Kepler discovers new planetary system press release

Kepler finds Earth-size planet in habitable zone press release

Kepler public data website

Kepler search range. Credit: NASA.

Tona Kunz

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Students prepare to launch particle detector into space

December 3, 2010 | 10:40 am

Rachel O'Leary, Rachel Powell and Adam Sandey, three of the original student members of the LUCID project. Image courtesy of the Langton Star Centre.

High school physics teacher Becky Parker and her students thought they would soon be the first to send a new type of particle-detecting microchip into outer space.

In 2012 the TechDemoSat-1 satellite will blast into orbit carrying a cosmic-ray detector that the students designed and adorned with their school mascot, a Langton lion.

But NASA will narrowly beat the students to the task. The space agency plans to fly detectors made up of the same microchips to the International Space Station before the end of 2011 to help monitor astronauts’ exposure to cosmic rays and other space radiation in real time.

This does not faze Parker, who teaches at Simon Langton Grammar School for Boys in Canterbury, England. Rather, it serves to her as proof that the extracurricular science project she orchestrates gives her students a taste of real, cutting-edge physics.

“It’s not a school experiment; it’s proper high technology,” Parker said. “It makes me sort of lose my breath sometimes that we’re sending up an experiment that probably has as much significance as many other experiments being sent up into space.”

It started with a field trip and a contest, as Parker noted in the June 2010 issue of symmetry magazine. Parker regularly takes groups of students to the CERN laboratory on the border of France and Switzerland. During a trip in 2007, tour guides took them to the laboratory of a British scientist, Michael Campbell. Campbell showed the students microchips he and his collaboration designed to detect particles in collisions in the Large Hadron Collider. The advanced, radiation-hard technology could detect the energy and direction of motion of individual particles.

Parker remembered the chips when, soon after the visit, Surrey Satellite Technology Ltd. held a competition to choose a student experiment to send into orbit on one of its satellites. She received permission for her students to use the technology in designing a cosmic-ray detector to go into space.

Diagram of the LUCID detector. Image courtesy of Surrey Satellite Technology Ltd.

To support the Langton Ultimate Cosmic-ray Intensity Detector – LUCID – project, more than 50 students have formed a miniature laboratory, complete with computer programmers and a publicity team. When students graduate, they hand their responsibilities down to the lower grades. Both boys and girls participate; Simon Langton Grammar School for Boys kept its historical name when the institution began admitting both genders.

Student William Matcham, 18, who has been working on LUCID since 2007, said he appreciates the independence the project offers the students.

“Most times in the classroom, we’re told what to do and what the result’s going to be,” he said. “This is the opposite.”

Before the detector heads to the great beyond, the students need to develop software that will control how often and for how long an electronic “gate” that activates the detector will open to expose its 65,000 pixels to cosmic radiation. When the detector is moving through an area with little radiation, the gate can stay open longer to gradually collect signals from cosmic rays passing through it. But when it is in an area with a high concentration of particles, such as the South Atlantic Anomaly, it needs to spend more time shut to avoid overloading the available bandwidth.

The students are developing an algorithm to make the detector constantly readjust the timing of the gate in response to its readings, said Professor Larry Pinsky, chair of physics at the University of Houston, who has been advising the students. The detector will beam cosmic-ray data from the satellite back to the students, who will distribute it to colleagues from at least 10 other schools in the Kent area and other schools around Europe.

“It’s like playing at being NASA or the European Space Agency, but they’re not really playing,” Pinsky said. “They’re doing the real thing.”

Since the project began, more Langton students have gone on to enroll in physics and engineering classes at university and, Parker hopes, will continue their pursuit of real-world science into the future.

Kathryn Grim

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