After the well documented false start, the Large Hadron Collider at Cern was up-and-running at the end of 2009, but what are scientists hoping to achieve with one of the world’s biggest ever experiments?
As the Large Hadron Collider spent the New Year in stand-by to allow scientists to prepare the machine for higher energies, analysis of over a million collisions recorded last year has yielded unexpected results.
A team of researchers have analysed the number of particles produced in the aftermath of high-energy collisions at 1.18 tera electron volts (TeV), and found an unexpectedly high number of mesons.
The LHC smashes together counter-circulating high-energy beams of protons, and when they collide their energy is transformed into mesons – subatomic particles consisting of a quark and anti-quark. The researchers – from MIT, CERN and the KFKI Research Institute for Particle and Nuclear Physics –also found that the number of mesons increased faster with collision energy than was predicted by models.
“This is the very first step in a long road to performing extremely sensitive analyses that can detect particles produced only in one in a billion collisions,” said Gunther Roland, MIT associate professor of physics and member of the CSM experiment.
The scientists believe the presence of these mesons will have to be taken into account when looking for the Higgs boson and other rare particles. “If we’re looking for rare particles later on, these mesons will be in the background,” Roland said, “These results show us that our expectations were not completely wrong, but we have to modify things a bit.”
During experimentation, the opposing beams are kept on their path with over 1,000 dipole magnets, and additional quadrupole magnets focused the beams in order to maximise collisions. In November each beam was circulating at 1.18 TeV, but from March scientists aim to run each beams at 3.5 TeV.
Running at higher energies requires a higher electrical current – 6kAmps – running to the magnets, so the LHC was put on standby in December to allow preparations for higher energies to take place. A new quench protection system (nQPS) will help to improve the electrical reliability of the connection between the magnets and the nQPS, and ensure higher currents can be safely handled.
Other teams also took advantage of the brief technical stop to carry out other technical verifications and efficiency tests on vacuum pumping units and ventilation components. Repairs were also undertaken on the water cooling system for the CMS (Compact Muon Solenoid) experiment.
The LHC is due to be ready for experimentation again in early March.