280
P. Jenni and T. S. Virdee
familiar in particle physics, the scope, scale, and geographical spread of the LHC
computing and data analysis are unprecedented.
6.6 Operation of the LHC: The Start of Data Taking
On the tenth of September 2008 first beams circulated in the Large Hadron Collider.
Nine days later, during the powering test of the last octant, alarms reached the
LHC accelerator’s control room and safety systems were activated to protect the
accelerator. It turned out that one of the 50,000 soldered joints had malfunctioned.
This led to an electrical arc that pierced the vacuum enclosure of a superconducting
dipole bending magnet leading a massive escape of helium, the pressure wave
of which caused considerable damage. The accelerator went offline for repairs.
The ATLAS and CMS experiments continued to run round-the-clock for a few
months recording billions of traversals of muons from cosmic rays. These data
demonstrated that the experiments were in a good shape to take collision data. After
a few tweaks the ATLAS and CMS experiments were even better prepared for first
collisions, which came on 23rd November 2009. The first collision data were rapidly
distributed, analysed and physics results produced.
Following a preliminary low-energy run in the autumn of 2009, the ATLAS
and CMS experiments started recording high-energy proton-proton collisions in
March 2010 at
√
s = 7 TeV. Some 45 pb −1 of data were recorded, sufficient to
demonstrate that the experiments were working well, according to the ambitious
design specifications and the results they were producing were consistent with the
predictions from known SM physics. Many parameters were examined, including
the efficiency of identification and reconstruction of physics objects, the measured
energy and momentum resolutions, the resolution of peaks in invariant mass
distribution, and more. An example of the performance from the CMS experiment is
the comparison of the observed width of Y particle with the design mass resolution.
The width is expected to be dominated by instrumental resolution. Figure 6.6 shows
that the observed width is measured to be 70 MeV consistent with the design value.
Also observed in such di-muon invariant mass distributions is a history of decades of
particle physics indicating the excellent performance of the experiments. The next
step was to see if known physics could be measured as per the predictions of the
SM, extrapolated to the new energies.
6.6.1 Measurement of SM Processes to Verify Experiment
Performance
Observation and accurate measurement of the production of known SM particles
at the LHC collision energies is a pre-requisite for the exploration of new physics,
P. Jenni and T. S. Virdee
familiar in particle physics, the scope, scale, and geographical spread of the LHC
computing and data analysis are unprecedented.
6.6 Operation of the LHC: The Start of Data Taking
On the tenth of September 2008 first beams circulated in the Large Hadron Collider.
Nine days later, during the powering test of the last octant, alarms reached the
LHC accelerator’s control room and safety systems were activated to protect the
accelerator. It turned out that one of the 50,000 soldered joints had malfunctioned.
This led to an electrical arc that pierced the vacuum enclosure of a superconducting
dipole bending magnet leading a massive escape of helium, the pressure wave
of which caused considerable damage. The accelerator went offline for repairs.
The ATLAS and CMS experiments continued to run round-the-clock for a few
months recording billions of traversals of muons from cosmic rays. These data
demonstrated that the experiments were in a good shape to take collision data. After
a few tweaks the ATLAS and CMS experiments were even better prepared for first
collisions, which came on 23rd November 2009. The first collision data were rapidly
distributed, analysed and physics results produced.
Following a preliminary low-energy run in the autumn of 2009, the ATLAS
and CMS experiments started recording high-energy proton-proton collisions in
March 2010 at
√
s = 7 TeV. Some 45 pb −1 of data were recorded, sufficient to
demonstrate that the experiments were working well, according to the ambitious
design specifications and the results they were producing were consistent with the
predictions from known SM physics. Many parameters were examined, including
the efficiency of identification and reconstruction of physics objects, the measured
energy and momentum resolutions, the resolution of peaks in invariant mass
distribution, and more. An example of the performance from the CMS experiment is
the comparison of the observed width of Y particle with the design mass resolution.
The width is expected to be dominated by instrumental resolution. Figure 6.6 shows
that the observed width is measured to be 70 MeV consistent with the design value.
Also observed in such di-muon invariant mass distributions is a history of decades of
particle physics indicating the excellent performance of the experiments. The next
step was to see if known physics could be measured as per the predictions of the
SM, extrapolated to the new energies.
6.6.1 Measurement of SM Processes to Verify Experiment
Performance
Observation and accurate measurement of the production of known SM particles
at the LHC collision energies is a pre-requisite for the exploration of new physics,