Summarising the detector performance

14 June 2010

One of the many plots found in the paper, this one on the Pixel dE/dx deposition showing the contributions from different types of particles

More than half a million minimum-bias events of LHC collision data were collected by the ATLAS experiment in December 2009 at centre-of-mass energies of 0.9 TeV and 2.36 TeV. The data went into many individual commissioning results, performance studies and notes from the various performance groups. The paper “Performance of the ATLAS Detector using First Collision Data” reports on studies of the initial performance of the ATLAS detector from these data.

The main editors (Bruno Mansoulié, Bill Murray and Hans-Christian Schulz-Coulon) put together all this information from notes and other sources and shrunk them to an intense 40 page document. “A summary of the different studies with the first collisions is that ATLAS works very well. The agreement between data and expectation (from simulations) was impressive. In the few cases where a discrepancy was found, the source was quickly identified and corrections were made to the detector description or to the software, which has been very useful for the 7 TeV collisions.” explains Bruno Mansoulié. “This would not have been possible without the work and contribution of so many physicists. All performance groups of Tracking, e/gamma, Jet/EtMiss, Muon, were very active and extremely helpful,” says Bruno. ”We not only chose among the existing, but we also triggered some complementary studies in order to have an homogeneous presentation of all important features (to our view).”

One of the physicists who was involved in the making of one of the contributing papers was Sky French: ”My role really began at the beginning of the year (before Christmas I'd been one of many people looking at the first 900 GeV electron candidates) when in mid-January, the e/gamma conveners, Laurent Serin and Mauro Donega, asked Marc Escalier and me if we would be willing to co-edit a note - which would become ’Electron and photon reconstruction and identification in ATLAS: expected performance at high energy and results at 900 GeV‘. This note was to contain ATLAS' understanding and studies of the 900 GeV electron and photon candidates - their kinematics, shower shapes, composition - and had to be completed within a timescale of a couple of weeks. "A challenge indeed!” adds Sky.

“The first step was to gather together everyone who had already started to, or wished to become involved in the endeavor. This fantastic team of people then stuck with Marc and me throughout the adventure, working tirelessly alongside us to develop our understanding of the data into that which can be seen in the note, and now the performance paper. With each weekly meeting came more and more progress, and it wasn't long before the first draft began to crystallize” remembers Sky. Once this (first) milestone had been reached, everyone continued to work hard, with many evenings, nights and weekends sacrificed, to make sure that, by the deadline, the draft grew into a complete note which would meet everyone's expectations and leave everyone satisfied that they'd done a thorough job. ”It was a bit frenetic at times to say the least - 3am phone calls, late night changes of selections - but we all made it to the finish line in the end!” she adds. Shortly after the note was approved and was integrated into the performance paper, their role as editors switched to being a role of assistance to the editors of the ATLAS performance paper - to be on hand to clarify and answer any questions they had about our note.

The decision to create the performance paper came from Fabiola Gianotti – it all started with an EB discussion on January 22nd. The whole process took four months, until the final draft was submitted to the journal on May 28th. “After each draft we had many comments from the collaboration and a few lively debates. We would like to thank these who took the time to read the paper and write comments. Then we (Bill, Hans-Christian and I) had to implement changes trying to accommodate the views of all the communities, without losing the homogeneity of the paper. Bill has many times taken the role of main editor, centralising corrections, providing new versions, answering all the comments on CDS one by one sometimes over whole nights! And Hans-Christian struggled with the plots… Also Karl Jakobs was a very active editorial board chair, even sometimes writing or correcting the paper himself." explains Bruno. In the intense process of reviewing the draft was not deeply changed but the corrections brought a lot of clarification and improved the reading.

The only difficulty to the end of the process was indeed a small one, but did cost a lot of work: the reformatting of the many plots in all the notes that did not have exactly the same appearance. “Our biggest role ended up being to reformat, or coordinate the reformatting of, the many plots in our note into an appearance appropriate for the performance paper (not much fun for anyone - but necessary to unite the CONF notes!),” remembers Sky. “We hope that this contributed to better defining the ATLAS standard style for plots in future papers.”, says Bruno.

“Finally, it's been really nice to sit and watch the hard work of the many different groups of people in ATLAS who worked on a CONF note combine together to make the 900 GeV performance paper,” summarises Sky. So it is no big surprise that the feedback of the referee of the JINST (journal of instrumentation) was “It (the paper) will certainly be acceptable for publication in JINST” with, as Bruno adds “just one page of minor editorial comments.”

Birgit Ewert

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