Kevin Einsweiler is a senior scientist at Lawrence Berkeley National Lab (LBNL). He joined the ATLAS Collaboration in 1993, playing an instrumental role in bringing US institutes into the LHC programme. He served as ATLAS Pixel Project Leader (2005-2009), Physics Coordinator (2011-2013) and Upgrade Coordinator (2014-2019).

The ATLAS experiment at the Large Hadron Collider (LHC) is on the eve of a new data harvest with the restart of the LHC for Run 3. The upcoming four-year run will provide a dataset nearly twice the size of what was collected in Run 2 (2015–2018).

How do you track a particle’s trajectory when your detector keeps moving? What if you find slight biases in your detector’s measurements? These were the challenges faced by the ATLAS Inner Detector during Run 2 of the LHC (2015–2018). Located at the heart of the experiment, the Inner Detector provides efficient and precise measurements of charged-particle tracks. In a new paper released today, physicists describe the complex solutions they developed to align the Inner Detector, ensuring the continued accuracy of the experiment.

A new age of exploration dawned at the start of Run 2 of the Large Hadron Collider, as protons began colliding at the unprecedented centre-of-mass energy of 13 TeV. The ATLAS experiment now frequently observes highly collimated bundles of particles (known as jets) with energies of up to multiple TeV, as well as tau-leptons and b-hadrons that pass through the innermost detector layers before decaying. These energetic collisions are prime hunting grounds for signs of new physics, including massive, hypothetical new particles that would decay to much lighter – and therefore highly boosted – bosons.

Nature has surprised physicists many times in history and certainly will do so again. Therefore, physicists have to keep an open mind when searching for phenomena beyond the Standard Model.

I joined the ATLAS experiment in 2012 after graduating from the University of Tokyo, however my previous experience was completely different from collider physics. During my Master’s course, I focused on the behaviour of a kind of silicon detector operated in Geiger mode. At that time, the experiments at CERN looked like a “castle” to me.

ATLAS is ready for Run 2 of the Large Hadron Collider (LHC) where proton beams will be collided together at a higher centre of mass collision energy of 13 TeV, and reach higher luminosities than ever before.

Previously in Notes from Underground, Dave Robinson wrote in some detail about the work going on inside the ATLAS Detector, and Clara Nellist wrote about the inner detector of ATLAS, discussing the different types of detection units or Sensors (Planars & 3D). I will continue to delve into the exciting world of the inner detector with its brand new Insertable B-Layer (IBL) and its related parts.

Closest to the beam pipe where particle collisions will occur in the very heart of ATLAS, a new sub-detector – the Insertable B-Layer – was put in place on 7 May. The IBL team had been developing and practicing the insertion procedure and tooling for two years because of the operation’s delicate nature.

In last week’s post for this Notes from Underground series, David talked about the work that goes on in the ATLAS pit. I'm going to take a step back and talk about what happens before a detector is installed. Although the work I want to tell you about didn't technically take place underground, much of it was performed in what is essentially a large airport hangar without natural light, so it certainly feels like you’re 100m down!

We physicists refer to the vast underground cavern that houses the ATLAS experiment as ‘the pit’. That may be a strange term to use for a marvel of civil, mechanical and electrical engineering, but nonetheless there are parallels to what you might imagine a ‘pit’ to be. Working inside the ATLAS detector in the pit can be dark, sometimes hot and not suited to those with claustrophobia. It often involves climbing several sets of makeshift steps and gantries and crawling flat on your stomach through narrow gaps to get to the part of the detector where you need to be. You will be wearing a safety helmet with mounted lamp, steel toe-cap shoes, one or more dosimeters to monitor radiation exposure and even a harness, if working at heights. Not to mention tools, laptop and any equipment you need to do your job. You tend to recognize the experimental physicists, engineers and technicians who have just come up from the pit – they stand blinking in the sunlight with a tired and rather sweaty appearance.

Today ATLAS has started the integrated runs. This has happened before, nevertheless this is the first time ATLAS subdetectors get together after the winter break, a lot of work has been done since then.

On Sunday December 6, 2009 at 8.00 the ATLAS Pixel Detector has measured, for the first time, tracks emerging from LHC collisions. It has been a very smooth start.

It's been a busy weekend for ATLAS. Last night, well, actually early this morning, we received the "stable beam" flag from the LHC.

Leading up to the lowering of the pixel detector into the ATLAS cavern, final preparations were proceeding quickly.

Following the successful combined SCT/TRT barrel test in the Spring 2006, a similar combined SCT/TRT endcap test is currently being performed in the SR1 building on the ATLAS experimental site at CERN. One quadrant of the SCT and two sectors of the TRT have been cabled up and are used in this test. The data taking and combined testing is expected to last until December 11th.

After almost 15 years of R&D and prototyping, the ATLAS pixel detector is finally almost ready for installation in ATLAS, and its first rendez-vous with colliding beams!

Wednesday 23rd August was a memorable day for the Inner Detector community as they witnessed the transport and installation of the central part of the inner detector (ID-barrel) into the ATLAS detector.

The first few months of 2006 saw the delivery to CERN of the final components of the ATLAS semi-conductor tracker (SCT), namely the completed SCT end-caps.

The SCT barrel was inserted in the TRT on 17 February, just missing Valentine's day. This was a change of emphasis for the two detectors. In the preceeding months there had been a lot of focus on testing their performance. The TRT had been observing cosmic rays through several sectors of the barrel. The two detectors had to be painstakingly aligned to be concentric to within a millimetre.