Run 1 (LHC)

Run 1 (LHC)
Name	Run 1 (LHC)
Location	CERN
Period	2010–2012
Energy	7–8 TeV center-of-mass
Beam	Large Hadron Collider
Experiments	ATLAS experiment, CMS experiment, LHCb experiment, ALICE experiment

Run 1 (LHC)

Run 1 (LHC) was the first operational data-taking period of the Large Hadron Collider at CERN spanning 2010–2012, delivering proton–proton collisions at center-of-mass energies of 7 and 8 TeV and heavy-ion collisions including lead–lead runs. The dataset collected during Run 1 enabled landmark discoveries and precision measurements that involved collaborations such as ATLAS experiment, CMS experiment, LHCb experiment, and ALICE experiment, and informed the strategy of the subsequent Long Shutdown 1 and upgrades overseen by European Organization for Nuclear Research management.

Overview

Run 1 commenced after commissioning phases at CERN and followed the initial machine incident in 2008 that delayed operations; it produced collisions used by ATLAS experiment, CMS experiment, LHCb experiment, and ALICE experiment for searches and measurements across the Standard Model sector and beyond. The period comprised a 2010–2011 stretch at 7 TeV and a 2012 extension at 8 TeV, enabling joint publications by the collaborations on topics ranging from electroweak processes to searches for supersymmetry and exotic resonances. International collaborations including teams from United States Department of Energy, Max Planck Society, Fermi National Accelerator Laboratory, INFN, and institutions across Europe, North America, and Asia contributed to detector operation, analysis, and theory interpretation.

Preparations and Upgrades

Before data-taking, extensive commissioning at CERN included cryogenics tests of the superconducting niobium–titanium magnets, systems integration with the Super Proton Synchrotron, and beam transfer studies involving the Injector chain institutions. Following the 2008 incident, repair campaigns led by CERN engineering teams implemented sector reconnections and enhancements to the quench protection system inspired by input from Accident Investigation Board reports and industrial partners such as Alstom in cryogenics. Detector upgrades and calibration tasks before Run 1 involved the ATLAS Pixel Detector teams, CMS Silicon Tracker groups, LHCb Vertex Locator engineers, and ALICE Time Projection Chamber specialists, coordinated with computing and grid readiness checks from Worldwide LHC Computing Grid partners including CERN IT and national grid initiatives.

Operations and Performance

Operational management was coordinated through CERN's accelerator complex and the LHC Machine Committee, achieving routine fills and luminosity ramp-up under direction from the LHC Operations Group. Beam energies, optics and luminosity levelling were tuned using feedback from Beam Loss Monitors, the Beam Position Monitor network, and accelerator physics studies by groups including OPR teams and luminosity working groups involving ATLAS experiment and CMS experiment luminosity contacts. Performance milestones included progressive increases in peak instantaneous luminosity, stable running at 3.5 TeV per beam in 2010–2011 and 4 TeV per beam in 2012, and successful heavy-ion operation coordinated with the ALICE experiment heavy-ion program and CERN Committee for Experiments scheduling.

Major Physics Results

Run 1 produced the discovery of a new boson consistent with the Higgs boson hypothesis, jointly announced by ATLAS experiment and CMS experiment in 2012, following analyses building on theoretical predictions from groups associated with Peter Higgs, François Englert, and Robert Brout and phenomenology from institutions such as CERN Theory Division and DESY. Precision electroweak measurements constrained parameters of the Standard Model and informed global fits involving the Particle Data Group and collaborations with Tevatron results from Fermi National Accelerator Laboratory and SLAC National Accelerator Laboratory. Flavor physics breakthroughs by LHCb experiment included measurements of CP violation and rare decays relevant to work by the Belle experiment and BaBar experiment. Heavy-ion collisions studied by ALICE experiment characterized quark–gluon plasma properties, connecting to theoretical frameworks developed at Brookhaven National Laboratory and RIKEN. Searches during Run 1 set stringent limits on models such as supersymmetry, extra dimensions proposed by Lisa Randall-type scenarios, and new gauge bosons anticipated in extensions studied at Institute for Advanced Study and major university groups.

Detector and Machine Issues

Run 1 operations exposed challenges including magnet quench protection, vacuum and cryogenic stability in superconducting sectors, and radiation-induced degradation in silicon detectors that involved interventions by CERN engineering, ATLAS detector maintenance teams, and CMS detector operations groups. The 2008 sector failure led to design reviews and the installation of additional quench relief and interconnect instrumentation with oversight from safety and technical review committees such as LHC Safety Assessment Group and industry partners. Detector-level issues included ageing of the CMS Pixel Detector and spark-related problems in gaseous detectors addressed by ATLAS muon and ALICE TRD teams, with mitigation strategies implemented during Long Shutdown 1.

Legacy and Impact on Subsequent Runs

Data and operational lessons from Run 1 directly shaped the scope of Long Shutdown 1 upgrades, the redesign and replacement of the CMS Pixel Detector, the installation of new ATLAS Insertable B-Layer, and accelerator upgrades to permit 13–14 TeV operations in Run 2 under the stewardship of CERN Directorate. Run 1 results influenced theoretical research programs at institutions such as Institute for Advanced Study, Perimeter Institute, and Max Planck Institute for Physics, and guided funding and strategic decisions by agencies including European Commission, UK Research and Innovation, and National Science Foundation. The run left a lasting imprint on particle physics collaborations, analysis techniques, and the Worldwide LHC Computing Grid model, setting benchmarks for detector performance, data preservation, and international scientific coordination.

Category:Large Hadron Collider