First year of LHC operations at 13 TeV

 SUPA physicists have had pivotal roles during the first year of operations of the LHC detectors during Run 2, at 13 TeV proton-proton collision centre-of-mass energies. After the discovery of the Higgs boson, the main goals have been to characterise the main Standard Model processes at 13 TeV and to search for phenomena beyond the Standard Model. There was great excitement on 15 December 2015 when ATLAS and CMS presented their preliminary results from the 2015 data taking at a CERN seminar*, in which both experiments observe an unexpected excess in the two-photon resonant channel at around 750 GeV. The ATLAS and CMS results are consistent with a 3.6 sigma and 2.6 sigma excess, respectively (see for example Figure 1). When one looks in a wider mass window (the “look-elsewhere effect”), the global significance of the excess is smaller (2.0 sigma and 1.2 sigma for ATLAS and CMS). While the theoretical community is very excited at the prospects for new physics beyond the Standard Model, the experiments are cautiously suggesting that we should wait for the 2016 results to check whether this is a statistical fluctuation or not. 



Figure 1: Excess of diphoton events at 750 GeV seen by ATLAS from Run 2 data.


SUPA physicists have also been very active in the early measurements programme using Run 2 data at LHCb. The calibration and alignment process now takes place automatically online, with the data quality used in the trigger the same as that used in offline selections, and the stored data are immediately available offline for physics analysis. This led to important early-measurement results, such as the first charm cross-section results at 13 TeV^ (Figure 2), which is an important test of perturbative QCD at untested energies. Further results on CP violation, rare decays and exotic resonance searches, such as the recently discovered pentaquark by LHCb, are currently underway.



Figure 2: Charm cross-section results by LHCb from Run 2 data.