Synopsis: Background checking at LHC

Preliminary measurements of particle collisions at 7TeV get a handle on background events at this unprecedented energy.
Synopsis figure
Illustration: CERN

The Large Hadron Collider (LHC) at CERN has begun 18 to 24 months of running at a 7-TeV center-of-mass energy—more than three times that achieved at the Fermilab collider. Before they can start to look for signals of new physics, however, the four LHC experiments, ATLAS, CMS, ALICE, and LHCb, must understand the huge spectrum of background events.

Using data from the first hour of 7-TeV operations, the CMS collaboration, which stands for “Compact Muon Solenoid” and consists of more than 2000 authors from 166 institutions in 38 countries, extracted information about the multiplicity of background events as a function of a (logarithmic) measure of the particle emission angle called “pseudorapidity.” They found a large increase in the number of charged particles per unit pseudorapidity compared with what has been seen at lower energies. The discrepancy exceeds that predicted by established event simulation models, indicating the parameters in these models will need to be tuned to be accurate for such high-energy collisions.

And so begins the dawn of exploration of a new energy frontier at the LHC. – Robert Garisto


Announcements

More Announcements »

Subject Areas

Particles and Fields

Previous Synopsis

Next Synopsis

Superconductivity

Microtraps for ultracold atoms

Read More »

Related Articles

Viewpoint: Ghostly Neutrino Comes into Sharper Focus
Particles and Fields

Viewpoint: Ghostly Neutrino Comes into Sharper Focus

The first results from the NOvA experiment set new constraints on charge-parity violation in neutrinos and on the ordering of neutrino masses. Read More »

Synopsis: Explaining a 750  GeV Bump
Particles and Fields

Synopsis: Explaining a 750 GeV Bump

Theorists try to explain data from the LHC that could be hinting at the existence of new particles. Read More »

Synopsis: The Heavy Limit of Dark Matter
Particles and Fields

Synopsis: The Heavy Limit of Dark Matter

A theoretical investigation of super-heavy dark matter particles finds that their existence might be discerned in the cosmic microwave background. Read More »

More Articles