A joint Fermilab/SLAC publication

LHC experiments push limits in new publications


The LHCb collaboration at CERN tightened constraints on previously imprecise theories in b-flavor production in its first paper using data from 7 TeV collisions.

The results mark the collaboration’s first inquiry into one of the main subjects it was built to study: rare decays that result in composite particles that contain bottom quarks or their antiparticles.

Physicists measured how often these particles, called b-flavored hadrons, appeared in the aftermath of collisions in the LHCb detector. The results fit within predictions from theory, said LHCb physicist Sheldon Stone, who worked on the paper. But those predictions were not well defined.

“The theoretical predictions had very large errors, 50 percent,” Stone said. “This will serve to constrain the theories. It’s a number we need to know to estimate what we can do in the future.”

The collaboration members hope eventually to see evidence of new physics, which means finding results that don’t match expectations. “But this result tells us we have enough b-quarks to do our job,” Stone said.

They should have enough information to sift through as well. When they wrote this result, they had collected 15 inverse nanobarns of collision data.

“We already have 3,500 for the next one,” Stone said.

The about 700 members of the LHCb collaboration, a small group compared to other experiments at the LHC, hope to build up to a rate of publishing 50 to 100 papers per year, he said.

The study built upon earlier measurements taken at lower energies in the Large Electron-Positron Collider and Fermilab’s Tevatron.

Another collaboration at the Large Hadron Collider, ATLAS, also recently published results that stretched physicists’ knowledge of particle interactions up to the 7 TeV range. Results from the ATLAS detector expanded the range over which physicists could rule out the existence quarks in an excited state. The discovery of excited quarks would have raised suspicions that quarks, the smallest units of matter detected, might be composed of even smaller particles.

The collaboration first announced the results at the International Conference on High Energy Physics in July.

Edit: The LHCb paper is also available here.

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