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Scientists at CERN observe direct coupling of the Higgs boson to the top quark

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A large apparatus at the CERN in Geneva. © Cern
The CERN in Geneva.

Physicists of TU Dort­mund University work not only on campus, but also at the large-scale research facility CERN in Geneva, Switzerland. With the help of large experiments, they search for new elementary particles, decays, and couplings of rare particles. A TU Dort­mund University team took part in the first-ever observation of an extremely rare process with the ATLAS experiment, which was presented in June at one of the most important conferences in the field of elementary particle physics.

Physicists of TU Dort­mund University work not only on campus, but also at the large-scale research facility CERN in Geneva, Switzerland. With the help of large experiments, they search for new elementary particles, decays, and couplings of rare particles. A TU Dort­mund University team took part in the first-ever observation of an extremely rare process with the ATLAS experiment, which was presented in June at one of the most important conferences in the field of elementary particle physics.

Scientists from the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) particle accelerator at CERN, Geneva, have for the first time succeeded in directly observing the simultaneous generation of a top-quark pair, the heaviest elementary particle, and a Higgs boson. This observation shows the direct coupling of top quarks and Higgs bosons and represents an enormous step toward a better understanding of the mechanism that gives elementary particles their mass: the Higgs mechanism. The results were presented at the opening of the LHCP conference, one of the most important in this field. It took place June 4-9 in Bologna, Italy.

Coupling of the two particles

The Higgs boson was predicted in the 1960s and first discovered in 2012 at the LHC. The detection itself, though, is just the first step on the way to understanding all of the properties of the newly discovered particle. Scientists now want to find out how the Higgs boson interacts with other particles, so they can solve the mystery of how, precisely, it gives them mass. That is especially difficult with the top quark, the most massive elementary particle, since it only rarely occurs together with a Higgs boson – only about one percent of all Higgs bosons are produced in association with a top quark pair.

The new results came about through worldwide collaboration. Among the participating institutions from Germany is the Chair of Experimental Physics IV at TU Dort­mund University. Some of the scientists there have been working for more than five years on the search for the process that has now been observed. In particular, they made important contributions to this observation through lead authorship of the first publication of the ATLAS collaboration on this topic and through the development of complex statistical analysis methods. In Germany, this research is funded by the Federal Ministry for Education and Research (BMBF).

Data from the LHC that were recorded by the ATLAS and CMS experiments in the years 2011 to 2017 serve as the basis for the first-ever observation. The results of the CMS collaboration were published in the journal Physics Letters B in mid-June; the results of the ATLAS collaboration were submitted to the journal Physics Letters B for publication.

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Location & approach

The campus of TU Dort­mund University is located close to interstate junction Dort­mund West, where the Sauerlandlinie A 45 (Frankfurt-Dort­mund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dort­mund-Eichlinghofen" (closer to Campus Süd), and from B 1 / A 40 "Dort­mund-Dorstfeld" (closer to Campus Nord). Signs for the university are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dort­mund.

To get from Campus Nord to Campus Süd by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Campus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.

TU Dort­mund University has its own train station ("Dort­mund Universität"). From there, suburban trains (S-Bahn) leave for Dort­mund main station ("Dort­mund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The university is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.

You can also take the bus or subway train from Dort­mund city to the university: From Dort­mund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dort­mund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dort­mund main station to the stop "Dort­mund Kampstraße". From there, take U43 or U44 to the stop "Dort­mund Wittener Straße". Switch to bus line 447 and get off at "Dort­mund Universität S".

Dort­mund Airport offers flights to several destinations in Central Europe. There are regular connections to Katowice, Kraków, London and Munich. For the approximately 20km-trip from Dort­mund Airport to TU Dort­mund University, you can use a shuttle bus to the railway Station "Bahnhof Holzwickede", from which trains depart to Dort­mund main station (please visit Verkehrsverbund Rhein-Ruhr for more information). Normally, the fastest way is to catch a taxi at Dort­mund Airport.

The H-Bahn is one of the hallmarks of TU Dort­mund University. There are two stations on Campus Nord. One ("Dort­mund Universität S") is directly located at the suburban train stop, which connects the university directly with the city of Dort­mund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Campus Süd) Eichlinghofen. The other station is located at the dining hall at Campus Nord and offers a direct connection to Campus Süd every five minutes.