Thursday, March 26, 2009

How Massive is the Higgs?

Probing for the Higgs Boson may be the greatest quest in high energy physics. But two Duke-led efforts are narrowing the search. As a result, the Higgs may be discovered sooner at a particle smasher outside Chicago rather than later at its replacement, the CERN Large Hadron Collider spanning the Swiss and French borders.

Scientists at the Fermi National Accelerator Laboratory in Batavia, Ill. are hoping that the energy of smashing protons together at near light speed will summon up these Higgs particles, which can't exist in today's low-energy universe. But those researchers want to shrink the range of possibilities, because each analysis involves interpreting a bewildering array of subatomic fragments from two million collisions a second.

On March 13, Fermilab announced that work-to-date suggests the Higgs' will likely show itself at a mass less than 160 billion electron volts but more than 114. (Using an energy measurement to define massiveness is a rule-of-thumb conversion under Einstein's famous E=MC2 equation.)

Energy ranges higher than 160 and less than 170 were excluded from the Fermilab search after an intensive analysis led by Duke physics professor Mark Kruse and his graduate student Dean Hidas. Under the Standard Model that defines the theoretical underpinnings of matter, a Higgs boson that heavy should usually immediately decay to two other fundamental particles known as W bosons. But "we see no indication of the Higgs," Kruse says.

Meanwhile, other work by Duke physics professor Ashutosh Kotwal and his students -- also involving W bosons -- is moving the search toward the lower end of likely masses. Ws are "force" particles mainly known as agents of radioactivity. But, under the Standard Model, knowing the mass of the W also predicts the mass of the Higgs.

And painstaking measurements by Kotwal's group have pegged the W's mass at about 80 times heavier than a proton. As a result, a Standard Model mass ratio suggests the Higgs should be comparatively light.

Kotwal initially made those measurements in 2007 by developing special software and novel techniques to analyze W decays within a barrel-shaped Fermilab fragment tracking chamber. Followup efforts could result in measurements three times more precise, Kotwal says.

A low-mass Higgs might weigh-in at about 120 billion electron volts, adds Kruse, who is also helping overseeing all Higgs searches at Fermilab. A 120 billion EV Higgs would be hard to detect there because its breakdown products are less than obvious, Kruse said. But detection would be harder still at the more powerful CERN collider because there would be many more breakdown products.

So Kotwal's graduate student Ravi Shekhar is now looking for the most characteristic fragments from a Higgs of that lower mass range. Those would include two bottom quarks from each Higgs breakdown, plus two electrons or two muons from the associated devolution of a Z boson. Z particles, like the W, are ordinarily involved in radioactive decay.

Stay tuned.

Sunday, March 22, 2009

Seeing Through Time: Historic Maps, Google Earth, and the Transformation of Durham

"Durham is a fascinating place in post civil war history," Trudi J.Abel, developer of the Digital Durham website, told the Visualization Friday Forum on March 20.

The Digital Durham website is a repository of maps, census data, photographs, personal and public records from post civil war Durham, built with grant support from the Center of Instructional Technology at Duke.

"The attempt for Digital Durham was to bring together special collections and manuscripts that had mainly been a part of the Duke Libraries," Abe said.

As of now the maps of Durham that have been digitized and available through the website are mostly pre-1923. Many of the post-1923 maps and manuscripts are still protected by copyright laws.

However, Abel has been in talks with the Mayor and is hopeful that these maps, including landscape, historic fire insurance, and other sketched maps, could be published on the website soon.

"One of the oldest views of Durham is of 1867-68, which was left by Lewis Blount. The only problem was that he carved out this map in 1923 based on how he remembered Durham at that time," Abel said.

She said these historic maps and census data can help explore the race and occupational diversity in different areas and analyze how segregation occurred in the various regions. Abel's current focus is to broaden the collection of historic maps of Durham, and trying to integrate satellite imagery and other sets of statistical data and tie it together for a detailed analysis.

"We are trying to put historic maps on Google Earth and compare the present infra- structure with the one that existed about a century ago. For example, we overlaid an 1888 map of Sanborn on Google Earth to analyze the changes that have taken place over time."

Abel also plans to make an interactive 3-dimensional map of Durham that can extract people's names, race, occupations and addresses and observe behavior of a particular population set through time.