LHCb sends gift to PANDA


The decommissioned outer tracker of CERN’s LHCb experiment embarked on a one-week journey to FAIR in Darmstadt, Germany, where it will be used by the PANDA experiment to study how subatomic particles build up matter.

Located near Geneva airport, the LHCb experiment is one of the four big experiments at CERN’s Large Hadron Collider (LHC). Dedicated to study so-called b-quarks, LHCb uses a set of successive detectors to study the traces of the particles thrown forward from the collision point. One of these detectors is the outer tracker, that was replaced during Long Shutdown 2 by a new setup based on scintillating fibers, the SciFi. The latter comes with a more refined granularity, allowing for a higher spatial resolution of the tracked particles.

After a decade of detecting particles, the outer tracker was still in good shape and working perfectly. After discussing the spare detector module at a conference with colleagues from the GSI Helmholtzzentrum für Schwerionenforschung, the LHCb collaboration decided to donate it to the PANDA (antiProton ANihilation at DArmstadt) experiment, which will be hosted by FAIR – the Facility for Antiproton and Ion Research – currently under construction at GSI.

At PANDA, the outer tracker will partly go back to resume its initial function of tracing the smallest building blocks of matter. With the aid of the FAIR accelerators, antiproton beams will be generated and stored, then collided with fixed targets (e.g. hydrogen) inside the PANDA detector setup. As this will happen at lower energies, the outer tracker will fit in perfectly to detect the light hadrons produced by the collisions. Hadron spectroscopy is where the physics goals of LHCb and PANDA overlap, and the two will be able to collect complementary data that can later be analyzed and compared. The tracker will also be used by students and young researchers in R&D projects, and in addition, in outreach activities for schools and the general public.

Transporting the tracker was no easy feat: In its transport frame, it is seven meters long, 3.5 meters wide and 5.5 meters high. It also weighs 24 tons. In 2018, when the disassembly started, the whole outer tracker was unmounted, placed in its transport frame – a specially designed handling cage – and removed from the LHCb cavern. Subsequently, it was moved to a storage hall within CERN, and more recently to near Sergy, France for the release procedures and finally back to near LHCb in Meyrin, Switzerland, where it was prepared for shipping. Hoisted up by cranes onto a truck, the detector began its journey from CERN to GSI/FAIR. Near Colmar, France, it was loaded on a ship for a multi-day journey up the Rhine river. At Gernsheim, Germany, another truck waited for the tracker and brought it safely to GSI/FAIR in Darmstadt where it will start its second life.

The close cooperation in the logistics and technical aspects by several colleagues at CERN and GSI/FAIR made the donation possible, in particular the relentless efforts of Niels Tuning (LHCb, Nikhef/CERN) and Anastasios Belias (PANDA, GSI/FAIR) with their vision for a second life of the formidable outer tracker. The donation was kindly agreed upon by the LHCb groups who meticulously built and operated the outer tracker, namely,

  • the National Institute for Subatomic Physics, Nikhef, The Netherlands,
  • the Physikalisches Institut der Universität Heidelberg, Germany,
  • the National Center for Nuclear Research, Warsaw, Poland,
  • the Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland,
  • and the Technische Universität Dortmund, Germany. (CP)
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