forward detector

Counting collisions

Whether searching for signs of new physics, or making precise measurements of known interactions, it is essential to know the total number of proton-proton collisions that the LHC delivers in ATLAS. This parameter, known as “luminosity”, is a vital part of ATLAS analysis.

27th October 2016
27th October 2016

One week to do it all – Days 4-7: Diffractive data taking

On Thursday morning the first fill reached “Stable Beam”.

19th February 2016

One week to do it all – Day 3: Preparing for Stable Beam

Tuesday at 23:55 I called the ATLAS shift leader and told them to stop the elastic physics run and ramp down the inner detector as the elastic program was over.

18th February 2016

One week to do it all – Day 2: Elastic data-taking

No time to waste after the alignment.

17th February 2016

One week to do it all – Day 1: Setting up

I have the pleasure to work for a very special sub-detector of ATLAS, called “Absolute luminosity For ATLAS” or ALFA in short.

16th February 2016

Measuring the way protons interact at 13 TeV

One of the most basic quantities in particle physics, the rate at which protons scatter off of one another (the cross section), cannot be calculated from the theory of strong interactions, quantum chromodynamics. It must instead be measured, and those measurements can then be used to tune the numerical models of LHC proton–proton collisions.

17th August 2015

Review before Run 2

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.

1st June 2015

Counting collisions with ALFA

Data from a special run of the LHC using dedicated beam optics at 7 TeV have been analysed to measure the total cross-section of proton-proton collisions in ATLAS. Using the Absolute Luminosity For ATLAS (ALFA), a Roman Pot sub-detector located 240 metres from the collision point, ATLAS has determined the cross-section with unprecedented precision to be σtot (pp → X) = 95.4 ± 1.4 millibarn.

5th July 2014