Category: Science & Technology
Key figures: Rolf-Dieter Heuer (CERN Director-General), the ATLAS, CMS, ALICE and LHCb collaborations
Summary
On 30 March 2010, at 13:06 CEST, CERN’s Large Hadron Collider (LHC) achieved its first proton–proton collisions at a centre-of-mass energy of 7 teraelectronvolts (TeV) — 3.5 TeV per beam — marking the formal start of the LHC’s research programme. It was the highest-energy particle collision ever produced in a laboratory, roughly three and a half times the energy previously achieved at any accelerator, and it opened the physics run that would culminate two years later in the discovery of the Higgs boson.
The milestone came after a difficult commissioning period. The LHC, built in a 27-kilometre ring beneath the France–Switzerland border near Geneva, had first circulated beams in September 2008 but was disabled days later by a faulty electrical connection between two superconducting magnets that damaged a section of the machine. Following repairs, beams returned in November 2009, and on 30 November 2009 the LHC reached 1.18 TeV per beam, surpassing the previous world record for accelerator energy. The 7 TeV collisions of 30 March 2010 confirmed that the repaired machine could run reliably at high energy.
“It’s a great day to be a particle physicist,” CERN Director-General Rolf-Dieter Heuer said as the collisions were recorded. “A lot of people have waited a long time for this moment, but their patience and dedication is starting to pay dividends.”
The record and the machine
The 7 TeV figure represented the combined energy of two counter-rotating proton beams, each accelerated to 3.5 TeV, colliding head-on at four points around the ring where the LHC’s large detectors sit. The new record displaced the 0.98 TeV per beam (1.96 TeV combined) that the Tevatron collider at Fermilab in the United States had held for roughly eight years. CERN chose 3.5 TeV per beam — half the LHC’s 7 TeV per-beam design energy — as a cautious operating point while engineers continued to consolidate the magnet interconnections implicated in the 2008 fault.
Collisions were observed by the LHC’s four main experiments: ATLAS and CMS, two large general-purpose detectors designed to search for the Higgs boson and physics beyond the Standard Model; ALICE, optimized for the study of quark–gluon plasma in heavy-ion collisions; and LHCb, dedicated to the physics of particles containing the bottom quark. Each recorded its first 7 TeV events on 30 March, and the collaborations — comprising thousands of physicists worldwide — began analysing the data almost immediately.
CERN announced that the LHC would then run continuously at 7 TeV for a period of 18 to 24 months, long enough for ATLAS and CMS to accumulate the collision data needed to probe a wide range of possible Higgs boson masses.
Significance
The 7 TeV collisions launched the experimental campaign that particle physicists had anticipated for decades. Operating at an energy frontier no earlier machine had reached, the LHC could produce and study particles too heavy to create elsewhere, allowing direct tests of the Standard Model and searches for supersymmetry, extra dimensions, and — above all — the Higgs boson, the last unconfirmed particle predicted by the Standard Model’s mechanism for giving mass to elementary particles.
That search succeeded: on 4 July 2012, drawing on data taken during the 7 TeV run (later raised to 8 TeV) that began in March 2010, the ATLAS and CMS collaborations jointly announced the discovery of a new particle consistent with the Higgs boson. The finding validated theoretical work by François Englert and Peter Higgs, who shared the 2013 Nobel Prize in Physics. The 30 March 2010 milestone thus stands as the practical beginning of the LHC’s scientific output and one of the defining moments in early twenty-first-century experimental physics.
Sources
- First LHC collisions at 7 TeV — CERN Timeline — CERN’s official record of the 30 March 2010 milestone.
- Large Hadron Collider — Wikipedia — encyclopedic overview of the collider, its energy records, and its four main experiments.
- LHC research programme launched with 7 TeV collisions — Symmetry magazine — contemporaneous specialist reporting, including the CERN Director-General’s remarks and the planned run length.
- CERN sets date for first attempt at 7 TeV collisions in the LHC — CERN press release — official announcement of the collision attempt and its physics goals.