Counting collisions with ALFA

5th July 2014 – 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.

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Hunting for the top squark

5th July 2014 – Completion of the analysis of 2012 data recorded by the ATLAS detector at the LHC’s collision energy of 8 TeV has significantly improved our capability of finding a supersymmetric partner of the top quark – also known as the top squark or the stop.

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Second anniversary of the Higgs boson discovery!

4th July 2014 – It’s been two years since the ATLAS and CMS experiments at CERN jointly announced the discovery of a new boson consistent with the Higgs particle of the Standard Model. Since then, the Higgs boson has been intensely examined. We’ve measured its spin, its mass, its lifetime, and observed its decay into bosons and fermions. In the next run of the Large Hadron Collider, we hope to learn more about how it interacts with other particles and to make many more precise measurements of its properties. By doing, we hope to extend the limits of our current understanding of the fundamental components of nature, and to seek clues for discovery.

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Precise measurement of the Higgs boson mass

3rd July 2014 – The ATLAS Collaboration has analyzed its full Run 1 data sample of seven and eight TeV (tera electron Volts) proton-proton collisions delivered by the Large Hadron Collider (LHC), to produce an accurate measurement of the Higgs boson mass. The Higgs boson resonance appears as a narrow peak in the mass spectra of its decays to two photons or to four charged leptons, as shown in the two figures below.

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Measuring top production in the LHC

3rd July 2014 – 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.

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New evidence for top quark pairs produced with W or Z bosons

3rd July 2014 – 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.

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The Symphony of ATLAS

23rd June 2014 – Bringing the nine-storey high, many-layered ATLAS detector back to life and preparing it for the Large Hadron Collider's next run is a complex task. Each sub-detector is setup and thoroughly tested before they are joined and the detector as a whole can begin recording data again.

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Are You Up for the Higgs Challenge?

16th June 2014 – It's been four weeks since the four-month long Higgs Machine Learning Challenge was announced. Almost 700 teams have signed up and more than 200 have beaten the in-house benchmark already.

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Higgs Mass to String Balls

6th June 2014 – ATLAS presented new results at the Large Hadron Collider Physics (LHCP) Conference in Columbia University, New York, 2 to 7 June. Many new searches and improved measurements were presented, among which were an updated Higgs boson mass measurement, a search for double Higgs boson production and new searches for Supersymmetry and exotic phenomena.

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A New Sub Detector for ATLAS

2nd June 2014 – 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.

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New Results from ATLAS at Quark Matter 2014

30th May 2014 – ATLAS has prepared a variety of new results for the Quark Matter 2014 conference using lead-lead (Pb+Pb) and proton-lead (p+Pb) data collected during Run1. 

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ATLAS Book Wins the IPPY Awards

29th May 2014 – "Hunting the Higgs", published by Papadakis Publishers in collaboration with the ATLAS Experiment won the Bronze prize in the Science category of the Independent Publisher Book Awards. 

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ATLAS Cavern Banjo Video Wins Third Place

27th May 2014
Joe Izen playing the banjo during the early hours of the morning in the ATLAS Control Room during the Large Hadron Collider's first run. (Image: Steven Goldfarb/CERN)


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Notes from Underground: Servicing Silicon

13th May 2014 – 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.

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"A hard day, with so much beauty"

13th May 2014 – ATLAS physicists travelled with Physics Without Frontiers 2014, a project run by International Centre for Theoretical Physics (ICTP), to three Palestinian universities this April to share the joy of scientific research with 140 students. 

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ATLAS Connects with Science Fest Visitors

29th April 2014 – On 5 and 6 April, Michigan State University's ATLAS physicists who are based at CERN connected virtually via video-conference to visitors attending the annual Science Festival in East Lansing, USA, to talk about particle physics and what it is like to be a physicist.

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ATLAS to present new results at Moriond

14th March 2014 – ATLAS collaborators and other scientists will be presenting new findings at the two weeks of the Rencontres de Moriond conferences, which starts on 15 March, at La Thuile in Italy.

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Five Outstanding Students Win ATLAS Thesis Awards

25th February 2014The ATLAS Thesis Awards recognize some of our postdoctoral colleagues who have made exceptional contributions to the experiment, across all areas, in the context of a PhD thesis. 

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ATLAS PhD Grant Scholars Announced

13th February 2014 – The first recipients of the ATLAS PhD Grant were presented with a certificate on 11 February at CERN by the programme’s selection committee. The three scholars, Lailin Xu of China, Josefina Alconada of Argentina, and Gagik Vardanyan of Armenia, were delighted at being able to continue their PhD programmes at CERN.

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Dealing With Data

16th January 2014 – In the first run of the Large Hadron Collider, almost a billion proton-proton collisions took place every second in the centre of the ATLAS detector. That amounts to enough data to fill 100,000 CDs each second. If you stacked the CDs on top of each other, in a year it would reach the moon four times. Only a small fraction of the observed proton–proton collisions have interesting characteristics that might lead to discoveries. How does ATLAS deal with this mountain of data? 

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