ATLAS

LHC takes on the SMEFT challenge

The quest for new physics at the LHC is entering a new phase: the experiments are designing new strategies to target potential deviations from the Standard Model (SM) predictions in a systematic way, to complement the traditional “bump hunts” and,…

ATLAS faces the challenge of Run 3

The ATLAS experiment is a general-purpose particle detector operating at the LHC. It consists of several concentric layers of particle detectors occupying a cylindrical volume 46m long and 25m in diameter. The innermost detectors reconstruct the…

The likelihood is dead, long live the likelihood

Among the sciences, particle physics has the luxury of having a well established theoretical basis. Often we focus on the elementary particles and model them mathematically with quantum field theories like the Standard Model. In order to compare…

CERN's new open data policy supports open science

The four main LHC collaborations (ALICE, ATLAS, CMS and LHCb) have unanimously endorsed a new open data policy for scientific experiments at the Large Hadron Collider (LHC), which was presented to the CERN Council today. The policy commits to…

Stephanie Zimmermann (1973 – 2020)

We have been deeply saddened to hear about the passing of Stephanie Zimmermann, an outstanding physicist, who has made a long-lasting contributions to the ATLAS experiment. Stephanie was involved in the Muon Detector Control System activities and…

Machine learning ushers in a new paradigm for particle searches at the LHC

Searching for physics beyond the Standard Model (BSM) is a major part of the research programme at the LHC experiments. Nearly all of these searches pick a signal model that addresses one or more of the experimental (e.g., dark matter) or…

What is the likelihood function, and how is it used in particle physics?

In statistical data analysis, “likelihood” is a key concept that is closely related to, but crucially distinct from, the concept of “probability”, which is often a synonym in everyday English. In this article, I first lay some necessary foundations…

ATLAS New Small Wheel Upgrade – activities resumed after down-time from COVID-19

As discussed in a previous issue of the EP Newsletter (The ATLAS New Small Upgrade – entering new waters, preparing to install and commission its first sector, October 2019), the New Small Wheel (NSW) Upgrade is the most challenging and complex one…

CERN experiments find first evidence for rare Higgs boson decay

The strength of the interaction between the Higgs field and a particle determines the mass it obtains from the Higgs and it is a mystery why the interaction strength is different for different particles. This puzzle is exacerbated as the leptons,…

How to search for new physics without knowing about it?

BSM searches at the LHC increasingly profit from ML techniques since this approach allows more general searches that minimise the probability of missing evidence of new physics. Very recently, the ATLAS collaboration has published a novel approach […

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