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The Large Hadron Collider (LHC) is due to resume operation in early May 2017 [!!!] and preparations are even ahead of schedule, by three days. On 21 April beams circulated in the Super Proton Synchrotron (SPS) for the first time this year. All four elements of CERN’s accelerator chain – Linear Accelerator 2 (Linac2), the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS) and the Super Proton Synchrotron – are now in operation.
Measuring nearly seven kilometres in circumference, the SPS takes particles from the PS and accelerates them to provide high-energy beams to the LHC. It also feeds the SPS North experimental area where, among others, the Common Muon and Proton Apparatus for Structure and Spectroscopy (COMPASS), and the NA61/Shine, NA62 and NA63 experiments are situated.
Ever since the discovery of the Higgs Boson in 2012, the Large Hadron Collider has been dedicated to searching for the existence of physics that go beyond the Standard Model. To this end, the Large Hardon Collider beauty experiment (LHCb) was established in 1995, specifically for the purpose of exploring what happened after the Big Bang that allowed matter to survive and create the Universe as we know it.
Since that time, the LHCb has been doing some rather amazing things. This includes discovering five new particles, uncovering evidence of a new manifestation of matter-antimatter asymmetry, and (most recently) discovering unusual results when monitoring beta decay.
Since the beginning of December, hundreds of people have been busy underground at CERN, working to make important repairs and to upgrade many facilities, across the whole of CERN’s accelerator chain and experiments.
This year the annual shutdown, called the Extended Year End Technical Stop (EYETS) is particularly long, lasting until May 2017, to allow more work to be carried out than in previous years.
At the beginning of the shutdown, the entire machine was drained of its liquid helium to avoid wasting any of the precious element...
Next, the technical team have had to replace one of the 1232 magnets in the LHC’s ring.
Also, the Super Proton Synchrotron (SPS) beam dump needed replacing.
Over the past few weeks the helium has been re-injected into the system and is being slowly cooled so that the machine can be handed back to the operations teams.
The Standard Model has worked beautifully to predict what experiments have shown so far about the basic building blocks of matter, but physicists recognize that it is incomplete. Supersymmetry is an extension of the Standard Model that aims to fill some of the gaps. It predicts a partner particle for each particle in the Standard Model. These new particles would solve a major problem with the Standard Model – fixing the mass of the Higgs boson. If the theory is correct, supersymmetric particles should appear in collisions at the LHC.
Finally, in many theories scientists predict the lighest supersymmetric particle to be stable and electrically neutral and to interact weakly with the particles of the Standard Model. These are exactly the characteristics required for dark matter, thought to make up most of the matter in the universe and to hold galaxies together. The Standard Model alone does not provide an explanation for dark matter. Supersymmetry is a framework that builds upon the Standard Model’s strong foundation to create a more comprehensive picture of our world.
The ALICE [A Large Ion Collider Experiment] experiment has been designed to study collisions of heavy nuclei. It also studies proton-proton collisions, which primarily provide reference data for the heavy-nuclei collisions. The reported measurements have been performed with 7 TeV proton collision data from LHC run 1.
In a paper published today in Nature Physics, the ALICE collaboration reports that proton collisions sometimes present similar patterns to those observed in the collisions of heavy nuclei. This behaviour was spotted through observation of so-called strange hadrons in certain proton collisions in which a large number of particles are created. Strange hadrons are well-known particles with names such as Kaon, Lambda, Xi and Omega, all containing at least one so-called strange quark. The observed ‘enhanced production of strange particles’ is a familiar feature of quark-gluon plasma... But it is the first time ever that such a phenomenon is unambiguously observed in the rare proton collisions in which many particles are created. This result is likely to challenge existing theoretical models that do not predict an increase of strange particles in these events.
Since particles began circulating in the large ring once more, the LHC’s operators have been testing and adjusting 24 hours a day to turn the LHC into a veritable collision factory. Their work involves forming trains of bunches, building them up over the next few weeks to several hundred and then several thousand bunches per beam.
To establish this production line of particles, all of the accelerator’s systems must be perfectly adjusted. The LHC is an extremely complex machine comprising thousands of subsystems and it takes weeks to adjust them all.
Last Wednesday, they started to collide the beams to be able to adjust the interaction points at the heart of the experiments. This step is carried out with so-called “pilot” beams, containing fewer than ten bunches and fewer protons than during the physics runs. These first collisions also allow the experiments to adjust their detectors.
In the coming days, the operators will continue to adjust and align the equipment. Once all of these steps are complete, they will be able to announce “stable beams”, the long-awaited signal for the start of the new data-taking season for the experiments.
Physics at the LHC has kicked off for another season. Today, the Large Hadron Collider shifted up a gear, allowing the experiments to start taking data for the first time in 2017. Operations are starting gradually, with just a few proton bunches per beam. The operators who control the most powerful collider in the world will gradually increase the number of bunches circulating and will also reduce the size of the beams at the interaction points. In a few weeks’ time, over a billion collisions will be produced every second at the heart of the experiments.
To find out more about physics at the LHC, you can watch our Facebook Live event tomorrow Wednesday 24 May at 4 pm CEST.