Occasional Musings of a Particle Physicist

ATLAS 2011 Public Results: End of Year Summary

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In the summer I started tweeting public results from the ATLAS Collaboration. These come in two formats: @ATLASpapers which are complete analyses submitted to scientific journals for peer review; @ATLASconf which are preliminary results, often a work in progress, where there may still be analysis work needed before journal submission but where the collaboration is satisfied with the robustness of the preliminary result to make it public and allow wider scrutiny.

2011 has been a very busy year for the collaboration. Towards the beginning of the year results were typically analysing the 2010 dataset of ~35/pb; however, since March new data has been flooding in and at the end of the year the total size of the 2011 dataset was almost 150 times the size of the 2010 dataset: ~5/fb! Throughout the year there have been many public results, both preliminary and submitted to journals, on subsets of the 2011 data; the fact that we can generate these results in a short time from a relatively complex experimental setup is testament to the hard work, planning and dedication of the collaboration as a whole. Not to mention hundreds of working group and review committee meetings every week!

ATLAS Papers

In 2011 ATLAS submitted 84 papers to scientific journals of which 58 were based on the 2010 dataset and 26 were based on various subsets of the 2011 dataset. The breakdown by physics topic is as follows:

2010 Data

  • Standard Model: 27
  • SUSY: 11
  • Exotics: 8
  • Performance: 5
  • B-Physics: 2
  • Heavy Ions: 2
  • Higgs: 2
  • Top: 1

2011 Data

  • Exotics: 9
  • SUSY: 7
  • Higgs: 6
  • Standard Model: 2
  • B-Physics: 1
  • Top: 1

Among these papers five I choose as highlights are:

    1. Measurement of the Inelastic Proton-Proton Cross-Section at sqrt{s}=7 TeV with the ATLAS Detector – This paper, published in Nature Communications, had the highest ‘impact factor’ of the year.
    2. Search for a heavy gauge boson decaying to a charged lepton and a neutrino in 1 fb-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector – This paper was the first submitted to a scientific journal using 2011 data.
    3. Search for the Higgs boson in the H->WW(*)->lvlv decay channel in pp collisions at sqrt{s} = 7 TeV with the ATLAS detector – This paper represents the largest dataset analysed for a paper submitted to a journal on the Higgs boson search in 2011.
    4. Search for production of resonant states in the photon-jet mass distribution using pp collisions at sqrt(s) = 7 TeV collected by the ATLAS detector – This paper was the 100th submitted to a scientific journal by the ATLAS Collaboration.
    5. Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS – This paper details the first new particle observed by the ATLAS Collaboration, albeit a composite particle predicted by the Standard Model.

ATLAS Conf Notes

In total 163 preliminary results were made public by ATLAS in 2011 of which a full list can be seen here. Although I don’t break them down by physics topic or dataset as above, the obvious highlights in terms of public interest were the Higgs boson searches:

  1. Combined Standard Model Higgs boson searches with up to 2.3 fb-1 of pp collision data at sqrt{s} = 7 TeV at the LHC – This note combined the ATLAS and CMS datasets using subsets of the 2011 data, this was the first such combination of ATLAS and CMS data.
  2. Combination of Higgs Boson Searches with up to 4.9 fb-1 of pp Collision Data Taken at sqrt(s)=7 TeV with the ATLAS Experiment at the LHC – This note was released soon after the Higgs boson seminar on December 13th 2011 and represents the best limits to date on the Higgs boson mass from ATLAS. Some of the input analyses use the full 2011 dataset.

So here’s to 2012, hoping it proves to be just as fruitful and that this time next year we can be discussing discoveries!


Written by Mark

02/01/2012 at 12:08 pm

Posted in Uncategorized

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