From Project X to the Higgs particle: AAAS slide set

February 27, 2009 | 10:19 am

Earlier this month, more than 40 scientists and teachers gave talks on particle physics, astrophysics, and cosmology at the annual conference of the American Association for the Advancement of Science in Chicago, one of the largest and most diverse science meetings in the United States. The conference coincided with the winter meeting of the American Association of Physics Teachers.

A Fermilab Web site now offers pdf and PowerPoint files of most of these presentations. Highlights include a session on Project X and physics at the intensity frontier; the hunt for the Higgs particle at the Tevatron and Large Hadron Collider experiments; and particle physics experiments for high school students. Craig Dukes’ talk gives a great explanation of what scientists hope to learn from Project X.

Kurt Riesselmann

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Neutrinos, Chastinos: Meet Tom, Dick, and Harry

February 26, 2009 | 10:07 am

Boris Kayser, a theoretical physicist at Fermilab, was part way into a Feb. 13 talk at the AAAS meeting in Chicago about the role of neutrinos in the evolution of the universe. He asked, are neutrinos the reason we exist? Maybe so–if, as some theorize, these ethereal particles were responsible for the triumph of matter over antimatter in the early universe.

He went on to explain that neutrinos come in three types, or flavors: the electron neutrino, the muon neutrino, and the tau neutrino, each denoted by the Greek letter ν followed by a number. But let’s just call them Tom, Dick and Harry.

Huh?

Kayser says he got the idea from the cover of the May 2007 isssue of symmetry, which featured a guide to subatomic particles, real and imagined, by New Yorker cartoonist Roz Chast. More of her cartoons are inside the issue, illustrating an article on the search for dark energy.

He said he always hated the rather sterile Greek-letter names of the neutrinos. So for a public lecture in Aspen in January 2008, he asked Chast for permission to use some of the symmetry cartoons in his slides, and he called the neutrinos by their Chastian monikers.

“I would rather the names be more poetic than Tom, Dick, and Harry,” he said, “but I’d rather have Tom, Dick, and Harry than the first, second, and third one.”

He said he was a bit apprehensive at first: Would the audience go for the pictures and not the physics?  But, he said, ”it turned out very well.”

Glennda Chui

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Why the dark side of the universe matters

February 24, 2009 | 3:45 pm

The world we see, including ourselves, barely makes a dent in the universe or our understanding of it. The 4 percent of the universe that is visible matter fails to shine a light on how the universe evolved or why galaxies spin the way they do. Those answers lie instead just out of reach of our understanding in the dark patches of the cosmos: the so called dark matter.

But year by year during the last decade scientists have inched their flashlights closer to this dark matter threatening to uncover its constitutes and how it works.

“Most of the matter in our universe, about 85 percent, is not explained. It is not stars or planets or dust or gas,” said Fermilab physicist Mike Crisler at the 2009 meeting of the American Association for the Advancement of Science in Chicago. “It is not made from atoms or molecules, protons, neutrons, or electrons. It does not absorb or emit light. We use the phrase “dark matter” in much the same way that ancient cartographers used the phrase ‘terra incognita.’ We do not know its nature.”

Even though we can’t “see” dark matter, we infer its presence because of its gravitational pull, affecting the rotation speed of stars and galaxies. Stars are moving faster than they would if they were only influenced by the gravitational pull of the galaxy core, so the galaxy itself must be embedded in large clouds of dark matter exerting another pull.

The power of the dark side

Luminous matter accounts for only about 4 percent of the universe.

Scientists believe that without dark matter, galaxies would fly apart, the universe wouldn’t have formed, and galaxies wouldn’t cluster.

“Until we find this stuff, we can’t really say that we understand gravity,” said Dan Akerib, a physics professor from Case Western Reserve University in Ohio, at another AAAS talk on dark matter.

While the discovery of what makes up dark matter wouldn’t change our everyday lives, it would change our perspective about the world, Crisler said.

“I think it would be a dramatic moment philosophically about the human role in the history of the universe,” said Crisler.

Scientists across the globe are racing to make dark matter in the laboratory, see it in the sky, and catch it in deep underground caverns.

“This is a very active field. There are experiments being done in the United States, Europe, Asia,” Akerib said. “During the last decade the sensitivity has increased by a factor of 100.”

If that continues, the next five to 10 years could hold key discoveries, he added.

The AAAS talks highlighted upgrades in two of those experiments at Fermilab in Illinois that use temperature extremes to search for dark matter–the Chicagoland Observatory for Underground Particle Physics, COUPP; and the Cryogenic Dark Matter Search, CDMS.

COUPP bubble chamber

COUPP

Scientists first used superheated liquid in bubble chambers in the 1960s, but their use died out in the 1980s. COUPP revived and upgraded the bubble chamber and gave it a new use: the search for dark matter.

“Bubble chambers may be the next big thing in dark matter detection,” said Crisler.

Bubble chambers effectively trace the interactions of weakly interacting massive particles, or WIMPs, with normal matter. Scientists believe the abundance of WIMPs left over from particle collisions just after the big bang may account for dark matter, Crisler said.

Mike Crisler adds a one-liter jar to the COUPP bubble chamber.

The liquid in a bubble chamber—typically hydrogen—is kept just above its normal boiling point, but under enough pressure that it will not boil unless disturbed. When a charged particle zips through the liquid it triggers boiling along its path, visible as a series of small bubbles. The biggest limitation for bubble chambers of the past was an inability to keep the liquid in a superheated state for an extended period of time. This required operators to time short blasts of particles from an accelerator to the few milliseconds when the temperature was just right. The COUPP collaborators got around this by finding a way to keep their liquid on the verge of boiling 80 percent of the experiment time, increasing the probability of catching dark matter particles.

Crisler and his colleagues recently upgraded a one-liter bubble chamber to block out more background noise and are almost finished constructing a 30-liter chamber, which will increase the probability of dark matter interactions. The current bell jar-shaped bubble chamber sits 350 feet underground at Fermilab and is filled with iodotrifluoromethane.

CDMS

At the opposite end of the temperature spectrum, CDMS uses cryogenics rather than super-heated liquid to pin-point WIMPs.

CDMS fridge and icebox in Soudan Mine.

When particles interact they can give off energy, which registers as heat. Scientists super cool the detector so that it conducts electricity without resistance. When energy is released from an outside particle colliding with a particle in the detector, it warms up part of the detector, briefly removing its superconductivity ability, and allowing scientists to see an electrical charge.

By measuring the difference in voltages associated with the temperature increases from an interaction, scientists can determine if the particle was a WIMP or a more common particle not associated with dark matter. WIMPs produce a low-charge yield while electron recoil from a photon has a large-charge yield.

ZIP detector in its mount.Silicon and germanium ZIPs, weighing 100 g and 250 g respectively, will be used in CDMS II.

The CDMS detector has been taking data since 2003 in the Soudan Mine in Minnesota with a 5 kg of active detector mass. An upgraded detector, with 25 kg of active detector mass and four times more sensitivity to particle collisions, is under construction. It will consist of seven stacks of six detectors, creating what Akerib calls the equivalent of a dark matter telescope underground.

Each type of technology used to search for dark matter has its strength. Which will prove the most useful remains to be seen.

CDMS and COUPP are racing other experiments in the United States, Europe, and Asia to find dark matter with accelerators, various types of underground detectors and telescopes.

“The search for dark matter is a horse race…,” Crisler said. But many physicists see the finish line in sight.

With additional reporting by Kristine Crane.

Tona Kunz

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The Galileoscope: an ultra-cheap, high-quality telescope for the IYA

February 17, 2009 | 12:36 pm

One of the fun aspects of being at a conference like AAAS is that you can be sitting at breakfast in the hotel when a group of people suddenly pull out a bunch of plastic parts which they rapidly assemble into a telescope and start looking at the skyline.

Now just about anybody will be able to see the moons of Jupiter, the rings of Saturn, and other astronomical objects not visible to the naked eye. Stephen Pompea from the National Optical Astronomy Observatory is leading the charge to make the Galileoscope, a high-quality, cheap telescope, available to anybody interested in star-gazing, especially in an urban environment, for the International Year of Astronomy, or IYA.

He had been frustrated that most telescopes for children were expensive, had poor optics, and the eyepieces were hard to use. He had discovered from his experience that many children would look through a telescope, not really be able to see what they had been told about, and essentially shrug it off and give up. “The view of Saturn is exciting to kids and will get them interested in science,” Pompea said. But first the child has to actually see the rings.

Shortly after this interview, Sir Martin Rees, Astronomer Royal of the United Kingdom, took an interest in the Galileoscope and played around with it. Photo courtesy of Doug Isbell, AAS.

Chatting with me at his breakfast table in the hotel lobby, Pompea told me that “most telescope kits are good to demonstrate the principles of optics, but not good for actually looking at things.” The Galileoscope is powerful enough to see the kinds of objects Galileo could see but the simple design is based on how kids use small telescopes. Eyepieces, in particular, are typically difficult for children to use. This eyepiece has a wide angle from which it be seen into, and it works well wearing glasses, as I discovered looking through the high atrium windows at the Chicago skyline.

The Galileoscope debuted at the opening of the IYA in Paris a few weeks ago, but it will be available for orders starting this week.

At breakfast, Kevin Marvel, executive officer of the American Astronomical Society, said, “Our goal is to have one million telescopes around the world this year.” He hopes to have them widely distributed in time for the northern hemisphere autumn observing season. The telescope will cost US$15, with discounts for orders of 100 or more.

Doug Isbell, also of AAS, added that “Jupiter is great in August and September” in the United States. He hopes that the telescope becomes one of the major legacies of the IYA.

After peering through the telescope, I called over a colleague who knows a lot more about telescopes than I and asked him to take a look. He was impressed and commented that he has a nice telescope but doesn’t use it as often as he would like because he doesn’t want to leave it setup on a tripod all the time, and it takes too long setup and pack away for casual use. He seemed to think this would be much more useful for casual viewing and thought he would probably get one.

The Gaileoscope will be supplemented by educational activities for teachers, astronomy clubs, and anybody else interested in using it.

See the Galileoscope being pulled apart and reconstructed in this video shot at AAAS in Chicago.

Video credit: Brad Plummer, SLAC National Accelerator Laboratory

David Harris

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After 15 years, CMS crystals ready for prime time

February 16, 2009 | 7:41 pm

A year may sound like a long time to shut down an experiment.

But it’s all relative to researchers working on the Compact Muon Solenoid detector, which will study the results of particle collisions in the Large Hadron Collider.

Physicists guided proton beams in a complete loop around the LHC for the first time in September 2008. But an electrical problem brought operations to a halt, and the LHC is not scheduled to start up again until September 2009.

That’s nothing compared to the time it took the CMS collaboration to obtain the lead tungstate scintillating crystals they needed to build the detector’s electromagnetic calorimeter–15 years.

A technician works on crystals for the CMS detector's electromagnetic calorimeter at CERN.

They began working on the crystals just after the fall of the Soviet Union and finally collected the complete set about a year ago.

The Soviet military began developing the crystals, possibly for use in lasers, said CMS Collaboration Board Chair Dan Green. But after the fall of the Soviet Union, they shared their research with CMS physicists.

“Only about a handful (of the crystals) existed,” said CMS Spokesman Jim Virdee at a presentation at the AAAS conference in Chicago. “We needed about 75,000 of them.”

Physicists wanted the crystals because they could absorb a large amount of energy in a short space and then release it rapidly as light. The electromagnetic calorimeter measures the energy of particles that interact with electromagnetic force by reading the amount of light generated by the photons and electrons the crystals capture from particle collisions in the detector.

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Kathryn Grim

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A first: String theory predicts an experimental result

February 16, 2009 | 4:49 pm

A slide from Barbara Jacak's presentation, originally from icanhascheezburger.com

One of the biggest criticisms of string theory is that its predictions can’t be tested experimentally–a requirement for any solid scientific idea.

That’s not true anymore.

At a AAAS session on Sunday, physicists said string theory is making important contributions to the study of two extreme forms of matter –one heated to trillions of degrees, the other chilled to near-absolute zero. In both cases the matter became a “perfect liquid” that ripples and flows freely, like water. String theorists analyzed the results by applying what they had learned from pondering how a black hole might behave in five dimensions. Then they went on to calculate just how free-flowing these liquids might be, predictions that the experimenters are using to guide the next stage of their work.

“It’s really a surprising, I would say serendipitous, once-in-a-generation convergence of scientific communities,” says Peter Steinberg, a nuclear physicist at Brookhaven National Laboratory and one of the organizers of the  panel. “None of us saw this coming.” (Full disclosure: Peter invited me to be a discussant for the session, which meant I got to take in all the talks and then ask the panel whatever I wanted. Sweet!)

Not to say that string theory has been proved. Clifford Johnson of the University of Southern California, the string theorist on the panel, was very clear about that. All the arguments about whether nature is composed of unimaginably tiny vibrating strings and multiple dimensions, and whether this will eventually explain the basic workings of the universe, are still unresolved.

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Glennda Chui

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LHC repairs almost complete

February 16, 2009 | 2:42 am

Engineers at CERN are installing the last component necessary to fix the Large Hadron Collider, LHC production manager Lyn Evans said at the AAAS conference in Chicago.

In about a month, they will begin the process of cooling the accelerator’s eight sectors, one by one. And by late September, “we’ll be ready to be back where we were last September,” Evans said.

The LHC saw first beams in September 2008, but shortly afterward a flaw in one of its electrical components brought the accelerator to a halt.

Researchers at CERN are in fact working to be in an even better position for collisions this time around. They’re spending their downtime training new physicists and practicing using the worldwide computer grid that will process the information the detectors collect. They have taken data from naturally occurring cosmic rays with the detectors in preparation for recording actual collisions. Once the machine is cooled, experimentalists will make partial beam runs to test pieces of the detector they have improved since the last run.

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Kathryn Grim

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Hunt for the Higgs kicking into high gear

February 16, 2009 | 2:40 am

Researchers with the Tevatron experiments at Fermilab told fellow scientists and journalists not to count them out of the race to discover the Higgs boson.

“In the next few years, if the Higgs lives in the expected mass range of 114 to 185 GeV, we will most probably see evidence of its existence,” said Dmitri Denisov, co-spokesman of DZero and a Fermilab staff scientist, Sunday at the American Association for the Advancement of Science conference in Chicago.

If the Tevatron experiments collect data through 2011, their chance of finding evidence for the Higgs particle is larger than 30 percent for most of the Higgs mass region of interest, 114 to 185 GeV/c2. A Higgs mass of 170 GeV/c2 already is excluded by the analysis of Tevatron data last summer (see plot below).

The Higgs explains how particles acquire mass, and is the last, missing piece of the Standard Model, which explains matter and how it acts. Essentially, the Higgs is the last piece of a puzzle describing everything around the world, including ourselves, Denisov said.

While the Large Hadron Collider in Europe is the new, bigger kid on the high-energy physics’ block, Tevatron researchers said their smaller experiments bring a finely-tuned machine and a head start to the game.

It might take the LHC until 2011 or 2012 to reach the sensitivity needed to find the Higgs, said Jim Virdee, spokesman of CMS and a professor at Imperial College of London.

Measurement constraints, including some from the Tevatron experiments, have narrowed in on the region considered the most likely home of a light-mass Higgs, the 114 to 185 GeV mass region.

LHC’s so-called sweet-spot sits in the mass range of 155 to 170 GeV.

“The Standard Model Higgs (if it exists) is being produced now at the Tevatron–we have enough energy,” said CDF co-spokesman Jacob Konigsberg, a University of Florida professor, who has worked with CDF since its beginning in the 1980s. ”There is just not enough of them.”

But that is quickly changing.

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Tona Kunz

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Stimulus creates science enthusiasm, long-term questions

February 15, 2009 | 2:05 pm

Science policy experts told journalists and researchers in Chicago Saturday that the outlook for federal support for science during the next decade exceeds expectations, but that it’s not time to dance in the streets yet.

Experts talking to a couple hundred people at the annual American Association for the Advancement of Science, or AAAS, conference said scientists face several hurdles and policy makers must answer tough questions. The answers will determine whether the boost to science lives past the memory of campaign promises and the spending of the stimulus bill passed by Congress Friday and expected to receive President Barack Obama’s signature this weekend.

The $790 billion stimulus bill allocates $21.5 billion for federal research and development, well beyond the $13 billion proposed by the House and $18 billion by the Senate.

“That is a lot more than I would have expected,” said Kei Koizumi, AAAS director of budget and policy. “The outlook is great for sustainable growth for research funding, especially for competitiveness.”

Koizumi served on Obama’s transition team and moves to the White House Tuesday as part of the OSTP staff.  He said the stimulus package, which had competitiveness-related basic research as one of four main priorities, puts the National Science Foundation, Department of Energy, and the DOE Office of Science on track to double their budgets over the next seven to 10 years, as promised in the 2007 America Competes Act.

The bill also targets billions of dollars at infrastructure improvement at universities and national laboratories.

Potentially, the stimulus bill also could have favorable impacts on budgets for basic and applied research, which have been declining since 2004.

But with research mainly comprised of multi-year projects, the money can’t stop once the economy gets back on track.

“There are some big questions,”  Koizumi said.

How funding will be sustained is a key question. Other concerns include: what role will the National Science and Technology Council play in the administration and how will it coordinate across groups, will the administration view universities as government contractors or a key vehicle to carry out federal research, and how will science be used to shape policy.

David Goldston, a former Congressional staffer for more than 20 years, said putting science in the stimulus bill removed much of the partisan stigma, but long-term, societal issues of how laws regulate science and technology and how it is used will foster new divisions.

There is a lot to be done, but the nation has the right people to do it–the Obama administration has arguably paid more attention to science policy than any administration ever, he said.

“… but that doesn’t mean anything is going to be easy,” he added.

Tona Kunz

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Hands-on physics

February 15, 2009 | 12:27 pm

Sunday morning, 10 a.m. While most teachers are at home enjoying their weekend, several hundred have come to Chicago to attend the conference of the American Association of Physics Teachers, which coincides with the AAAS meeting. I’m sitting in a meeting room with about 40 teachers who have huddled in groups of two to four to solve a tricky particle physics puzzle to build protons and other particles made of quarks.

“It is really neat to see how engaged you are,” says Marge Bardeen, who presents this AAPT session. “Imagine how your students would get engaged in this activity.”

Bardeen is the head of the Fermilab Education Office. Teachers regularly come to Fermilab to develop new classroom activities and experiments. Here at the AAPT/AAAS conference, Bardeen shares their results with other teachers.

A good example is a low-cost particle detector that teachers and students can use to detect cosmic rays, the stream of invisible particles that constantly bombard earth. The detector allows students to record the particles and make scientific measurements, which they then compare with results obtained by other students at different locations.

“One student even observed solar flares,” said Bardeen. “He then communicated with a student in Australia to confirm his observation.”

Other examples include the measurement of radioactive decay in pennies. The coins mostly consist of copper, and the challenge is to find out whether all coins have the same content. Measuring the radioactivity of many coins made in the same year, the students discover that pennies made before 1982 cause different peaks in their charts than those made post 1982. The composition of the material used for pennies changed in 1982. The United States switched the penny’s core to zinc and coated it with copper.

Another teacher developed a teaching unit that allows students to determine the mass of the top quark. Starting with the tracks of particles recorded by the collider experiments at Fermilab, students measure the length of particle tracks, measure the angles between pairs of tracks and then use simple vector addition to calculate the mass of the top quark.

All activities are geared toward physics master classes, which science teachers usually offer as extracurricular sessions at their schools. To find out more about these activities and programs, visit the Web pages of the Fermilab Education Office.

Kurt Riesselmann

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