Shots from the Long Shutdown

8th April 2015 – As ATLAS gears up to record data from proton collisions delivered by the Large Hadron Collider (LHC) at an unprecedented energy level, here are glimpses from the last two years of preparations.

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A Week of Firsts

7th April 2015The annual conference, Moriond, is in its 50th edition this year, and I’ve had the pleasure of coming down to Aosta in Italy to participate in the QCD session; for the first time. It’s actually a week of firsts for me. The conference organizers described it as being in a kind of “QCD confinement”.

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Beam Splash in ATLAS

ATLAS is ready and waiting for collisions

6th April 2015 – The first long shutdown of the Large Hadron Collider has now ended, after two years of intense but careful activity refurbishing and improving many aspects of ATLAS, mirroring the work to prepare the LHC for collisions at the new energy of 13 TeV.

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New physics and Italian food

Moriond Electroweak: physics, skiing and Italian food

30th March 2015 – If you’re a young physicist working in high energy physics, you realize very soon in your career that “going for Moriond” and “going to Moriond” are two different things, and that neither of the two means that you’re actually going to Moriond. This year’s “Moriond Electroweak” was held in the Italian mountain resort of La Thuile, and had a special significance.

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The coupling of the Higgs boson to fermions and bosons as a function of the particle’s mass.

ATLAS further verifies Standard Model coupling/mass relationship of Higgs boson

27th March 2015The discovery of a Higgs Boson in 2012 by the ATLAS and CMS experiments marked a key milestone in the history of particle physics. It confirmed a long-standing prediction of the Standard Model, the theory that underlines our present understanding of elementary particles and their interactions.

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Angular observables sensitive to the spin and parity of a Higgs boson decay.

The scalar boson

26th March 2015The ATLAS experiment has released results confirming that the Higgs boson has spin 0 (it is a so-called “scalar”) and positive parity as predicted by the Standard Model, making it the only elementary scalar particle to be observed in nature.

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Candidate event in the search for a Higgs boson produced together with a top-antitop quark pair.

In search of rare Higgs boson production with top quarks

24th March 2015In proton-proton collisions, several processes can lead to the production of a Higgs boson. The most “frequent” process (which is about one collision in four billion!) is the fusion of two gluons, contained in the initial protons, into a Higgs boson through a “top-quark loop”. Least frequent is a mode where the Higgs boson is produced in association with a pair of top-quarks.

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Latest ATLAS Results on the Higgs Boson

19th March 2015 – On 17 March, ATLAS presented their latest Higgs physics results at an LHC seminar at CERN from data collected during the LHC's first run. The updated results include searches for the Higgs boson in association with top quarks, measurements of the spin and parity, and improved and combined coupling measurements, all showing good compatibility with Standard Model predictions. These results are also being presented at the 50th Rencontres de Moriond ElectroWeak conference, in La Thuile, Italy, this week.

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ATLAS physicist wins L'Oreal-UNESCO Women in Science award

12th March 2015 – Rajaâ Cherkaoui El Moursli is one of the five laureates of the L'Oreal-UNESCO for Women in Science Awards this year.

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ATLAS' Higgs ML Challenge Data Open to Public

5th March 2015 – The dataset from the ATLAS Higgs Machine Learning Challenge has been released on the CERN Open Data Portal.

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Winners of the ATLAS Thesis Awards Announced

27th February 2015 – Six PhD students were announced as the winners of the ATLAS Thesis Awards 2014 from 28 nominations received. The winners – Andrew Chisholm, Kun Liu, Marcus Morgenstern, Priscilla Pani, Dennis Perepelitsa, and James Saxon – were given certificates and an engraved glass model of the ATLAS detector during a ceremony on 19 February 2015 at CERN, Geneva.

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Second ATLAS PhD Grants

23rd February 2015 – The recipients of the second ATLAS PhD Grant were announced last week. The three young ATLAS physicists – Danijela Bogavac, Silvia Fracchia, and Declan Millar – were given certificates at a small ceremony at CERN, Geneva.

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Looking at the Dark side of Matter

19th February 2015The search continues for dark matter, a new kind of matter that doesn’t emit or absorb light. It is assumed to account for the missing amount of mass in our Universe. The total mass in our Universe can be inferred from the observation of gravitational effects of stars in galaxies, and galaxies in clusters of galaxies. However the amount of mass calculated from the observed distribution of light is much less. It is proposed that dark matter makes up the discrepancy as it does not emit light.

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Cleaning ATLAS cables

The Ties That Bind

15th January 2015A few weeks ago, I found myself in one of the most beautiful places on earth: wedged between a metallic cable tray and a row of dusty cooling pipes at the bottom of Sector 13 of the ATLAS Detector at CERN. My wrists were scratched from hard plastic cable ties, I had an industrial vacuum strapped to my back, and my only light came from a battery powered LED fastened to the front of my helmet. It was beautiful.

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ATLAS collision event with two charm-tagged jets.

In search of super charm

9th January 2015 – If all the experimental evidence supports a theory, why should anyone want to dream up additional particles? Yet exactly this situation arose in the late 1960s. At that time, when the complete table of the known hadrons could be explained with just three quarks, theorists were already proposing a fourth, which they whimsically called “charm”.

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After subtracting off the background from the data, the boson-pairs are clearly visible in the data!

The Art of Rediscovery

7th January 2015When I tell people I’m a particle physicist, one of the most frequent questions I get asked is: “So, have you discovered anything?” Funnily, I’ve spent much of the past two years trying to rediscover something that’s already been seen before. In today’s world, which fetishizes the New, this may seem slightly lame, but just because we’ve discovered something, doesn’t mean we’ve fully understood it.

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ATLAS Muon Big Wheel

Handing In the ATLAS Keys

8th December 2014 – After completing more than 250 work packages concerning the whole detector and experimental site, the ATLAS and CERN teams involved with Long Shutdown 1 (LS1) operations are now wrapping things up before starting the commissioning phase in preparation for the Large Hadron Collider's restart. The giant detector is now more efficient, safer and even greener than ever thanks to the huge amount of work carried out over the past two years.

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"Dirt Detectives"

5th December 2014 – For five days last week, 110 ATLAS collaborators worked in 10 different shifts to help clean and inspect the detector and the cavern that houses it before the toroid magnets are turned on.

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The ATLAS experiment on Scholarpedia

3rd December 2014 – An overview of the ATLAS experiment written by physicists Monica Dunford and Peter Jenni has been published on Scholarpedia. The article is the first in the series on experimental high-energy physics that the editors of the subject hope to host on the website.

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Join the Higgs Hunt

1st December 2014 – Higgs Hunters, the first particle physics venture on Zooniverse, a citizen science project, has been launched in collaboration with the University of Oxford, New York University and the ATLAS Experiment. Higgs Hunters invites online volunteers to participate in studying the properties of the new boson, which may hold clues as to what lies beyond our current understanding of the universe.

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