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Workshop Explores Potential Signatures for Early LHC Searches

Workshop participants ponder signatures versus models on the Kavli patio. (Photo by Lori Ann White.)

SLAC hosted a diverse group of about 100 particle theorists—and several particle experimentalists—last week at the Workshop on Topologies for Early LHC Searches. The workshop follows a June 4 meeting at CERN called "Characterization of New Physics at the LHC," during which experimentalists and theorists at the Large Hadron Collider grappled with how to ensure that important new physics can be filtered from the flood of data at the powerful particle collider.

"The experimenters said they needed more examples of signatures from the theory community," said workshop co-organizer Jay Wacker, of SLAC's Theory Group. These signatures, he explained, will show experimenters how physics beyond the Standard Model of particles and particle interactions might actually appear in the LHC data.

The LHC research program officially began March 30 when its two proton beams collided with a total energy of 7 trillion electron-volts. By late July, Wacker and two of his students authored a paper describing how the first public release data already extended searches beyond the capabilities of Fermilab's Tevatron. The LHC has since accumulated 100 times the amount of data it had in July and is expected to increase that amount by another factor of 100 by the end of next year.

"Every analysis from here on out has the potential for new physics," Wacker said, leaving experimenters hungry for "a whole class of new models" to guide their searches. "If you're not looking at the right channels, you have the potential to delay or even miss discoveries." Thus the SLAC workshop. According to Wacker, the goal is to compile the new signatures from the workshop and have them ready to present at a follow-up meeting at CERN in November. 

Theorists, for their part, welcome the opportunity for more input into LHC searches.

"There's been a movement in the theory community to broaden the view," said co-organizer Mariangela Lisanti of Princeton University. For example, she explained, while initial searches at the LHC have focused primarily on the theory of supersymmetry, well-motivated models exist that don't contain supersymmetry at all. Or the Higgs boson, another popular target of LHC searches. "What both theorists and experimentalists want are guidelines for data analysis with the broadest possible application to different theory models," Lisanti said.

"But it's been nearly ten years since the theory community has created specific proposals to cover as broad a range of new theories as possible," Wacker added. "This time our goal has been to focus on the experimental signatures of the theories and how similar many of them are, rather than how to distinguish different underlying theories through their details."

Both particle theorists and experimenters alike say they hope this strategy will offer the most bang for the buck. Or for the particle collision, as the case may be. 

Key organizers of the workshop included Wacker, Rouven Essig, also of the Theory Group, Tim Tait of the University of California at Irvine, and former SLACers Lisanti, Natalia Toro, Philip Schuster (both now at the Perimeter Institute). In keeping with the global nature of the LHC program, the workshop included such experts as Mihoko Nojiri (KEK), Hyungdo Kim (Seoul), David Morrisey (TRIUMF) and Ben Gripaios (CERN), who had come to SLAC specifically to participate in these discussions.

—Lori Ann White
SLAC Today, September 28, 2010