Users meeting highlights LHC successes

At Argonne National Laboratory earlier this month, U.S. scientists and students from the four LHC experiments gathered at their annual users organization meeting to discuss results from the recently completed 2011 run.

“Few of us could imagine how much you would achieve and we thank you,” said the organization’s chair, Harvey Newman, in response to CERN physicist Eva Barbara Holzer’s presentation of the successful performance of the LHC.

During her presentation, Holzer noted that the LHC outperformed expectations for the second year in a row. Running at a beam energy of 3.5 TeV for the 2011 run, the LHC delivered an enormous amount of data – around 12.4 inverse femtobarns total – to the experiments during 1,300 hours of stable beam. When the accelerator comes back online in 2012, Holzer and other scientists hope the peak luminosity will increase by another 60 to 75 percent, at a beam energy of 4 TeV.

“We haven’t seen evidence [of the Higgs], but we’re getting close. We’ve observed a wide range of channels,” Argonne physicist Alexander Paramonov said of the team’s search for the Higgs boson.

Fermilab physicist Joe Lykken, who presented on new ways to search for evidence of supersymmetry, also weighed in on the Higgs search.

“I don’t think you can hide it forever from the LHC, but you can hide it for a long time,” Lykken said.

The CMS detector, which operated at 99 percent efficiency for the 2011 run, also performed well.

“It was a fantastic year,” said Princeton graduate student David Lopes-Pegna of the CMS results, which have so far led to more than 100 publications.

Collaborators working on the ATLAS experiment, meanwhile, have published more than 80 papers.

One goal of the meeting was to provide graduate students with a chance to present their research. Andrew Adare of Yale, for example, detailed new results for the ALICE experiment. Like many of the collaborations, the ALICE team expects large increases in data sets over the coming years.

To keep up with the higher energy and luminosity, the LHC and its experiments will undergo various upgrades while the accelerator is shut down for the winter. More extensive upgrades are planned for 2013 and 2014 in order to prepare for a potential full beam energy of 7 TeV.

“There’s been a fantastic level of achievement here, both by the LHC and the experiments,” Newman said in summing up the meeting. “You can already see potential for new results with several times more data by the end of 2011 and greater potential for discoveries next year. There’s great anticipation by everyone.”

Brad Hooker