 "Photo: Alex Ransom")
The first paper with physics data from the Large Hadron Collider (LHC) will be published in January with help from UTD scientists and students’ work.
Physics professors Joe Izen and Xinchou Lou, along with several graduate students, are examining data from the world’s largest particle collider at UTD’s computing site.
They are working on ATLAS, one of four experiments using the LHC to data scientists hope will expand their understanding of physics and particles.
Information from ATLAS findings will be jointly released with the other experiments’ papers for presentation and a comment period.
The two UTD physicists spent their summer in 2007 crawling among and testing some of the 80 million channels in the electronics room of the LHC, in essence, paying their dues to work alongside about 2,500 scientists, Izen said.
The shutdown of the LHC from September 2008 to November 2009 gave scientists time to improve alignment of ATLAS’s pixel detector.
Prior to the Nov. 20, 2009 power-up of the LHC, the ATLAS detector gatheredinformation on cosmic rays, which are energy particles that entered the collider from outer space.
UTD research scientist Mahsana Ahsan works on-site near Geneva, Switzerland, with the UTD team. She aligns the innermost detector in the ATLAS experiment to 20-30 microns, about a fine hair’s width, to measure accurately, she said.
Ahsan worked the 5 a.m. Dec. 6 shift when scientists were able to turn on the pixel detector in the ATLAS experiment.
“Right now (Dec. 9) we’re running at rather low energy,” said UTD research scientist Kendall Reeves, who works on-site. “The energy we’re running at right now has already been explored by previous experiments with accelerators. One doesn’t really expect, at this point, something new.”
Once the accelerator began running with higher energy collisions than previous experiments, scientists had new data to analyze beyond the reach of other experiments, such as the 2.36 trillion electron volt collisions on Dec. 8 and 14.
“I was very happy to see that I was on shift and the pixel detector had been turned on, and I was also able to see immediately how the detector looks,” Ahsan said. “This time, we were even more excited because we had the pixel detector in.”
The pixel detector rests the closest to the beam at 1.5 centimeters away, making it the most precise and vulnerable detector, Izen said.
“(Dec. 6), for the very first time, the machine and the beams were stable enough and well understood enough that we dared turn it on,” Izen said.
Reeves, a six-year ATLAS project veteran, was added to UTD team in November from the University of Wuppertal in Germany to work on the pixel detector.
”I have been amazed by the quality of the data coming out,” Reeves said. “It’s very gratifying after working on this since 2003 to actually see it coming together so beautifully.”
Another experiment in the LHC, the Compact Muon Solenoid (CMS), uses a different approach to look for the some of the same characteristics as ATLAS. Lou and Izen said scientists working on the two experiments felt a sense of competition.
“We’re all in it together, but we’re both looking for the same signals,” Izen said. “When it comes to what we think are the analysis tricks, the talks of the experiment are password protected.”
At full operation, millions of interactions will occur each second during particles’ collisions. The scientists can select only 200 events to collect and review from these.
The scientists’ ability to gather and analyze the data could make the difference for discovering new particles such as the Higgs boson (see sidebar), the only unobserved particle in the standard model of physics, Izen said.
UTD undergraduate physics senior Alex Palmer worked on the ATLAS trigger system during a summer internship, which selects the events for data. High-energy physics graduate students Wei-Cheng Wong, Masa Kondo and Hari Namasivayam are contributing by helping code programs.
“Technically, on my coursework, this is one credit hour, and I’ve been spending more time than (on) my eight-credit-hour (course),” Namasivayam said.
Wong said they stayed at their laptops most of the time working on the project and would need years to go through the data. He joined the UTD team in 2006 and traveled to the European Organization for Nuclear Research (CERN) with Izen and Lou in 2007.
Izen hopes to spend a year at CERN to work more closely on the experiment.
Don't call it 'the God particle'
The Large Hadron Collider, the world’s largest particle collider, has the potential to give scientists the chance to observe and study the Higgs boson, sometimes referred to as ‘the God particle,’ to the chagrin of scientists.
The Higgs boson is thought to make up part of a particle’s mass, but has not been observed, Izen said.
The term ‘God particle’ was coined from Leon Lederman’s “The God Particle: If the Universe Is the Answer, What is the Question?”
“Everyone in high-energy physics hates it,” said Joe Izen, physics professor.
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