Around midnight on April 22nd, CERN’s Large Hadron Collider set a new world record for beam intensity at a hadron collider when it collided beams with a luminosity of 4.67 × 1032cm-2s-1. This exceeds the previous world record of 4.024 × 1032cm-2s-1, which was set by the US Fermi National Accelerator Laboratory’s Tevatron collider in 2010, and marks an important milestone in LHC commissioning.
Credit: CERN
“Beam intensity is key to the success of the LHC, so this is a very important step,” said CERN Director General Rolf Heuer. “Higher intensity means more data, and more data means greater discovery potential.”
Luminosity gives a measure of how many collisions are happening in a particle accelerator: the higher the luminosity, the more particles are likely to collide. When looking for rare processes, this is important. Higgs particles, for example, will be produced very rarely if they exist at all, so for a conclusive discovery or refutation of their existence, a large amount of data is required.
The current LHC run is scheduled to continue to the end of 2012. That will give the experiments time to collect enough data to fully explore the energy range accessible with 3.5 TeV per beam collisions for new physics before preparing the LHC for higher energy running. By the end of the current running period, for example, we should know whether the Higgs boson exists or not.
“There’s a great deal of excitement at CERN today,” said CERN’s Director for Research and Scientific Computing, Sergio Bertolucci, “and a tangible feeling that we’re on the threshold of new discovery.”
After two weeks of preparing the LHC for this new level of beam intensity, the machine is now moving in to a phase of continuous physics running scheduled to last until the end of the year. There will then be a short technical stop, before physics running resumes for 2012.
A beam in the LHC is not a continuous string of particles, but is divided into chunks a few centimetres long squeezed down to the size of a human hair at the collision point. Elsewhere in the ring the beam size varies but is normally less than a millimetre.
AcJames Gillies and Mike Lamont at CERN's blog these chunks are what we call bunches. Each bunch contains about a hundred billion protons, and it’s a measure of just how small protons are that if you were to scale each one up to the size of a marble, the bunch length would be as far as the distance from Earth to Uranus and the width of the bunch would be something like the distance between the Earth and the Moon. Neighbouring marble sized protons would be as far apart as Geneva and Hamburg. So it’s not surprising that when bunches collide in the LHC, only a handful of proton-proton collisions happen.
Discovery in particle physics is a statistical process, so increasing the number of bunches is important. It increases the number of collisions, or the statistics as physicists put it. The LHC is designed to run with 2808 bunches per beam, separated by a gap of just 25 nanoseconds. Since this is still early days in LHC running, we’re still at relatively low numbers and the bunch spacing is 50 nanoseconds. Nevertheless, building the number of bunches steadily this year towards last night’s record-breaking 480 per beam and beyond means that LHC experiments have already collected far more data so far this year that they collected in all of 2010.
Increasing the number of bunches in the beam is a stepwise process, since although each proton only has the energy of a mosquito in flight, by the time you multiply that by hundreds of billions, you have a large amount of energy stored in the beams. The operators need to be sure that the systems designed to protect the machine from damage are all ready before increasing the number of bunches. When the LHC reaches its full design potential, the beams will carry the energy of a 20,000 tonne aircraft carrier travelling at 12 knots. With 480 bunches per beam at half the LHC’s design energy, the energy stored in the beams equates roughly to the same aircraft carrier travelling at the rather more sedate pace of a little under 3 knots. Not quite so impressive, but a significant amount of energy nevertheless.
CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. India, Israel, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer status.
Source: CERN
A screenshot of 'LHC Page One' — which displays the status of the accelerator.
“Beam intensity is key to the success of the LHC, so this is a very important step,” said CERN Director General Rolf Heuer. “Higher intensity means more data, and more data means greater discovery potential.”
Luminosity gives a measure of how many collisions are happening in a particle accelerator: the higher the luminosity, the more particles are likely to collide. When looking for rare processes, this is important. Higgs particles, for example, will be produced very rarely if they exist at all, so for a conclusive discovery or refutation of their existence, a large amount of data is required.
The current LHC run is scheduled to continue to the end of 2012. That will give the experiments time to collect enough data to fully explore the energy range accessible with 3.5 TeV per beam collisions for new physics before preparing the LHC for higher energy running. By the end of the current running period, for example, we should know whether the Higgs boson exists or not.
“There’s a great deal of excitement at CERN today,” said CERN’s Director for Research and Scientific Computing, Sergio Bertolucci, “and a tangible feeling that we’re on the threshold of new discovery.”
After two weeks of preparing the LHC for this new level of beam intensity, the machine is now moving in to a phase of continuous physics running scheduled to last until the end of the year. There will then be a short technical stop, before physics running resumes for 2012.
A beam in the LHC is not a continuous string of particles, but is divided into chunks a few centimetres long squeezed down to the size of a human hair at the collision point. Elsewhere in the ring the beam size varies but is normally less than a millimetre.
AcJames Gillies and Mike Lamont at CERN's blog these chunks are what we call bunches. Each bunch contains about a hundred billion protons, and it’s a measure of just how small protons are that if you were to scale each one up to the size of a marble, the bunch length would be as far as the distance from Earth to Uranus and the width of the bunch would be something like the distance between the Earth and the Moon. Neighbouring marble sized protons would be as far apart as Geneva and Hamburg. So it’s not surprising that when bunches collide in the LHC, only a handful of proton-proton collisions happen.
Discovery in particle physics is a statistical process, so increasing the number of bunches is important. It increases the number of collisions, or the statistics as physicists put it. The LHC is designed to run with 2808 bunches per beam, separated by a gap of just 25 nanoseconds. Since this is still early days in LHC running, we’re still at relatively low numbers and the bunch spacing is 50 nanoseconds. Nevertheless, building the number of bunches steadily this year towards last night’s record-breaking 480 per beam and beyond means that LHC experiments have already collected far more data so far this year that they collected in all of 2010.
Increasing the number of bunches in the beam is a stepwise process, since although each proton only has the energy of a mosquito in flight, by the time you multiply that by hundreds of billions, you have a large amount of energy stored in the beams. The operators need to be sure that the systems designed to protect the machine from damage are all ready before increasing the number of bunches. When the LHC reaches its full design potential, the beams will carry the energy of a 20,000 tonne aircraft carrier travelling at 12 knots. With 480 bunches per beam at half the LHC’s design energy, the energy stored in the beams equates roughly to the same aircraft carrier travelling at the rather more sedate pace of a little under 3 knots. Not quite so impressive, but a significant amount of energy nevertheless.
CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. India, Israel, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer status.
Source: CERN
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