LHC experiments weigh up 2016 data

12 August 2016

The 38th International Conference on High-Energy Physics (ICHEP 2016) took place on 3–10 August in Chicago, US. Among numerous results presented, the LHC experiments released their latest analyses of 13 TeV proton–proton collision data recorded in 2016.

Based on a data set of 12 fb–1, ATLAS released many new results including 50 conference notes. Highlights included new and highly precise measurements of WZ production that constrain anomalous boson couplings. ATLAS also searched in many final states for signs of direct production of supersymmetric and other new particles from beyond the Standard Model. No compelling evidence was found. In particular, the intriguing hint of a possible new state with a mass of 750 GeV decaying into photon pairs seen in the 2015 data has not reappeared. The larger data set  also allowed ATLAS to “rediscover” the Higgs boson with high statistical significance.

The CMS collaboration presented more than 70 new results based on an integrated luminosity of 13 fb–1, also including a rediscovery of the Higgs. In line with the findings from ATLAS, an updated search for a 750 GeV diphoton resonance by CMS did not confirm the excess observed previously, setting a limit on its cross-section of 1.5 fb at the 95% CL. Searches for supersymmetric and exotic particles also showed no significant excesses, allowing mass limits to be increased by a few hundred GeV. New massive Z bosons up to 4 TeV and string resonances decaying into pairs of jets up to 7.4 TeV have now been excluded, while searches for dark matter exclude mediator masses up to 2 TeV in several standard scenarios.

LHCb presented many interesting new results in the domain of flavour physics. A particular highlight was the discovery of the decay mode B0 K+K, which is the rarest B-meson decay into a hadronic final state ever observed, as well as searches for CP violation in the charm system. Another first was a measurement of the photon polarisation in radiative decays of Bs mesons, and determinations of the production cross-sections of several key processes at a collision energy of 13 TeV – some of which at first sight are at variance with current predictions.

Based on lead–lead collisions with an energy of 5 TeV per nucleon pair, the ALICE collaboration presented new measurements of the properties of the quark–gluon plasma. These included fundamental measurements of the production of quarkonium at the highest collision energy ever reached at an accelerator. ALICE also measured the viscosity of the plasma at the new energy, showing that the system still behaves almost as an ideal liquid.

• CERN Courier went to press as ICHEP 2016 got under way. A full report will appear in the next issue.


bright-rec iop pub iop-science physcis connect