In a new result released today, the ATLAS Collaboration announced strong evidence of the production of four top quarks. This rare Standard Model process is expected to occur only once for every 70 thousand pairs of top quarks created at the LHC and has proven extremely difficult to measure.

A quarter-century after its discovery, physicists at the ATLAS Experiment are gaining new insight into the heaviest-known particle: the top quark. The huge amount of data collected during Run 2 of the LHC (2015-2018) has allowed physicists to study rare production processes of the top quark in great detail, including its production in association with other heavy elementary particles.

As the heaviest elementary particle, the top quark is appropriately named. It is ideally suited for precision measurements that test the limits of our understanding and could provide indirect hints at new physics. Physicists from around the world gathered in Beijing, China, last week at the annual TOP2019 conference to exchange the latest news, results and ideas on the top quark. For the ATLAS collaboration, TOP2019 proved a great success, with several excellent talks and posters presented by its members.

As the heaviest known particle, the top quark plays a key role in studies of fundamental interactions. Due to its short lifetime, the top quark decays before it can turn into a hadron. Thus, its properties are preserved and transferred to its decay products, which can in turn be measured in high-energy physics experiments. Such studies provide an excellent testing ground for the Standard Model and may provide clues for new physics.

As the heaviest known elementary particle, the top quark has a special place in LHC physics. Top quark-antiquark pairs are copiously produced in collisions recorded by the ATLAS detector, providing a rich testing ground for theoretical models of particle collisions at the highest accessible energies. Any deviations between measurements and predictions could point to shortcomings in the theory – or first hints of something completely new.

Among the most intriguing particles studied by the ATLAS collaboration is the top quark. As the heaviest known fundamental particle, it plays a unique role in the Standard Model of particle physics and – perhaps – in yet unseen physics beyond the Standard Model. A new ATLAS result, presented today at the European Physical Society Conference on High-Energy Physics (EPS-HEP) in Ghent, Belgium, examines the full Run 2 dataset to find evidence of charge asymmetry in top-quark pair events, with a significance of four standard deviations.

The top quark is a unique particle due to its phenomenally high mass. It decays in less than 10-24 seconds, that is, before it had time to interact with any other particles. Therefore many of its quantum numbers, such as its spin, are transferred to its decay particles. When created in matter-antimatter pairs, the spins of the top quark and the antitop quark are expected to be correlated to some degree.

The top quark – the heaviest known fundamental particle – plays a unique role in high-energy physics. Studies of its properties have opened new opportunities for furthering our knowledge of the Standard Model. In a new paper submitted to Physical Review D, the ATLAS collaboration presents a comprehensive measurement of high-momentum top-quark pair production at 13 TeV.

The production of top quarks in association with vector bosons is a hot topic at the LHC. ATLAS first reported strong evidence for the production of a top quark in association with a Z boson at the EPS 2017 conference. In a paper submitted to the Journal of High-Energy Physics, the ATLAS experiment describes the measurement of top-quark production in association with a W boson in 13 TeV collisions.

Using Run 1 data, ATLAS reports a new differential production rate measurement of top quark pairs and a precise new determination of the top quark mass.

Ordinary matter is made of just three kinds of elementary particles: up and down quarks, which form the atomic nucleus, and electrons, which surround the nucleus. But the rest of nature is not so straightforward: heavier forms of quarks and leptons are produced regularly at particle accelerators.

The top quark, the heaviest known elementary particle, has a unique place in the Standard Model. By precisely measuring its properties, ATLAS physicists can probe physics beyond our current understanding.

The ATLAS collaboration presented exciting new results at the 10th International Workshop on Top Quark Physics (TOP2017), held in Braga (Portugal). The conference, which concluded today, brought together experimental and theoretical physicists specializing in the heaviest known elementary particle: the top quark.

For many physicists, discovering “new physics” means bringing to light a new particle. Another path to discovery lies in carefully measuring the properties of known particles and the interactions between them. The ATLAS experiment has now released new results on the top quark's interaction with the charged intermediate vector boson.

Observing rare productions of heavy elementary particles can provide fresh insight into the Standard Model of particle physics. In a new result, the ATLAS Experiment presents strong evidence for the production of a single top-quark in association with a Z boson.

For the first time, ATLAS has measured the kinematics of the top quark and of the tt̅ system in 13 TeV events containing two charged leptons, two neutrinos and two jets (called “dilepton” events).

The ATLAS experiment has been searching for the process in which a pair of top quarks is produced, where one is a “virtual” particle that emits a Higgs boson on the way to becoming a “real” particle. This process is referred to as ttH production after the particles that are produced.

My work involves analyzing data to try to understand how nature works at the most fundamental level, by searching for new particles and ways in which they interact. Specifically, I am looking at the top quark, which is the heaviest fundamental particle known to exist, with a mass of about 180 times that of a proton.

ATLAS has released a new precise measurement of the mass of the top quark, the heaviest known elementary particle.

The top quark conference normally follows the same basic structure. The first few days are devoted to reports on the general status of the field and inclusive measurements; non-objectionable stuff that doesn’t cause controversy. The final few days are given over to more focused analyses; the sort of results that professors really enjoy arguing about.

This week, physicists from around the world are gathering at the Top 2015 workshop in Ischia, Italy to discuss the latest measurements of the top quark. As the heaviest known fundamental particle, the top quark plays a special role in the search for "new physics".

The annual top conference! This year we’re in Ischia, Italy. The hotel is nice, the pool is tropical and heated, but you don’t want to hear about that, you want to hear about the latest news in the Standard Model’s heaviest and coolest particle, the top quark! You won’t be disappointed.

With a precision of just under 14% − currently dominated by our ability to understand how many proton-proton collisions have occurred at ATLAS (i.e. luminosity) − this measurement is able to confirm that quantum chromodynamics, the theory of the strong interaction, still seems to be going strong!

Evidence for the production of a W or Z boson together with a top quark pair, referred to as tt̄W and tt̄Z processes, has been found in the ATLAS analysis of the 8 TeV data from the LHC’s first run.

Using the full data sample from the LHC’s first run of proton-proton collisions, ATLAS has measured the production rate of top and anti-top quarks.

At the EPS HEP conference today, ATLAS released a new precise measurement of the top quark mass using events where both top quarks decay via W bosons to electrons or muons. ATLAS also presented limits on the possibility of the top quark decaying to channels not foreseen in the Standard Model. A comparison of the behaviour of top quarks and anti-top quarks produced at the LHC is in agreement with the prediction of the Standard Model, disfavouring models of new physics that require a large top/anti-top asymmetry.

Welcome back, dedicated top quark enthusiast. I’m sure you’ve all been waiting on the edge of your seats for an update from TOP 2012, and I can now confirm that a combined team of LHC & Tevatron physicists narrowly beat a mixed team of physicists from LHC & Tevatron at croquet.

Greetings from the TOP 2012 conference, Winchester UK! What’s a ‘Winchester’ I hear you asking? A type of gun? Indeed yes, though sadly not of the smoking variety that we’re all so keen to find. However in this particular case Winchester is a historical town in the south of England, complete with the typical rolling green fields, a cathedral, and the not so typical contingent of visiting physicists!

The 5th International Workshop on Top Quark Physics (TOP2012) will take place in Winchester, UK, from the 16th to the 21st of September. It will gather experts in the field of top quark physics as well as PhD students and will highlight the newest results and topics related to the physics of top quarks.

For the last months (which feel like years…) I’ve been working, within a small group of people, on the precision measurement of the top quark pair production cross section, and if you think that sounds complicated – the German word is “Top-Quark-Paarproduktionswechselwirkungsquerschnitt”.

ATLAS is about to check one more particle off of its Standard Model (SM) checklist. Namely the top quark. This famous quark is perhaps one of the most complex of the SM particles.