ATLAS of the world

29 January 1999

1800 physicists from 33 countries are participating in the ATLAS experiment, the largest detector being built for CERN’s LHC collider. CERN Courier asked ATLAS Spokesperson Peter Jenni how the collaboration works.


The LHC will collide protons at higher energies (7 TeV per beam) than ever achieved before under laboratory conditions to penetrate still further into the structure of matter and recreate the conditions of the universe just 10­12 seconds after the Big Bang when the temperature was 1016 degrees. Designing and building a particle physics detector like ATLAS – 7000 tonnes of high technology equipment ­ involves more than just following a sheet of instructions. In a modern-day parallel of a potential Tower of Babel scenario, scientists have to work together as a team while remaining thousands of miles apart.

What is the balance between individual creativity and being part of such a large collaboration?

The successful design and construction of a large and complex state-of-the-art detector requires the creative participation of many people. It is not the collaboration that is creative, but the sum of its individual members. There are many subsystems, so that people mostly work in small groups, contributing creatively. Ensuring that all systems fit and work together, and are affordable, constrains the creative process, but good ideas will make their way!

How are important decisions made? How are individuals heard?

Many important decisions involve just one or two subsystems. They are discussed initially in the subsystem plenary meetings, where everybody can participate and make their voices heard. Recommendations are then discussed in the ATLAS Executive Board, and presented in plenary meetings which play a primary role in forming a consensus when decisions are required. The leadership can only “lead” the collaboration to decisions which are understandable to all, or at least to a large majority. Practical constraints ­ costs, schedule, the availability of manpower etc ­ also come into the equation. There is a clear sequence of steps from subsystem to systems, with the vote by the Collaboration Board being the ultimate step for major decisions.

How is such a large and far-flung collaboration managed?

Each subsystem has its own management team. At the same time, the Executive Board and Spokesperson maintain general oversight.

The Technical Coordination team is responsible for making sure that all subsystems fit together. In parallel, there are national representatives who monitor the use of resources from their respective countries and make sure they are well used.

The Collaboration Board sets out policy issues, and is not involved with execution, which is a management responsibility. However, frequent contacts, between for example the Spokesperson and the Collaboration Board Chair, ensure that policy issues are properly handled, and that fair solutions are found for difficult problems. Finally, direct contacts between individuals and teams with the collaboration management also play an important role.

How do 1800 people communicate among themselves? How do you bridge large distances and overcome time differences?

Electronic communication (e-mail, Web, telephone, video conferencing) is obviously very important. However, regular direct human contacts are crucial. Meetings play a significant role.

How are tasks apportioned?

By trying to match the interests and resources of the participating teams to the tasks. This can succeed only if everyone is also willing to share the less interesting but necessary tasks such as building support structures, contributing to buying cables, writing utility software etc. This works because the physicists are motivated by the prospect of exciting results, which depend on having a complete, working detector system. Of course it is not always easy to arrive at an optimal task-sharing to everyone’s satisfaction, with all tasks assigned.

How are the costs apportioned?

There is no absolute formula. Large teams from wealthy countries are expected to carry a larger share of the costs than small teams from countries with developing economies. Matching the possible contributions of teams and countries to the overall effort is a central part of forming the collaboration.

Where does the money come from?

Mostly from the funding agencies of the various participating countries. There are also significant contributions from CERN, and some resources from individual universities.

How do people join?

Teams interested in ATLAS may contact the Spokesperson, and their interest is then brought to the attention of the Collaboration Board (CB). After examining their resources, their potential share of the work, their relationships with other teams already working on ATLAS etc, the CB votes on their admission.


How do you ensure that all the detector pieces fit together?

The Technical Coordinator, supported by the Technical Coordination Team, works with all the subsystem groups to ensure that the separate pieces will fit together without interfering with each other, and that the full detector can be assembled.

How will data analysis be shared among 1800 people?

The data will provide experimental input for many separate research topics. ATLAS scientists will pursue these research areas mostly in small groups working at their home institutions. All collaborators will be invited to analyse the data by being part of analysis teams.

In some respects data analysis by individual ATLAS physicists can be compared to data analysis by astronomers using the Hubble Space Telescope. In both cases, scientists choose the research areas and data that interest them most.

How does a collaborator get credit for his/her contributions?

This is of course a major question. Internal publications within the collaboration, usually with one or a few authors, will document individual contributions. These can be made known to the whole scientific community. Also, leading contributions are often recognized by asking the person to speak at conferences. However, the large collaborations still have to learn how to handle this question. Major results are obtained collectively, because people are willing to share the tasks. It is not only the final analysis which counts, but all the work which makes it possible to collect the data, and calibrate and prepare it for final analysis.

What is the impact of the global spread of the collaboration? How does one contribute from 6000 miles away?

The global spread implies that factors such as transport of components need to be taken into account during the construction, and that communication logistics play a major role. Full information, eventually including data analysis, must be available simultaneously all over the world. Nevertheless, it also implies that scientists from outside Europe have to travel long distances to participate in discussions and meetings, in the detector assembly and testing, and eventually in the operation of the experiment. They may have to spend extended periods away from their homes and home institutions. However, all ATLAS scientists are after the same goal of doing frontline LHC physics, and are therefore willing to endure these inconveniences to achieve that goal. But being away from home is not necessarily always a disadvantage. In particular young people are stimulated by such experience.

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