TOTEM: Discoveries may go “forward” at the LHC

After two very intense years of activity during which the TOTEM apparatus has gone through an extensive upgrade programme, the collaboration is now ready to explore the new territories in forward physics that will open at 13 TeV.


One vertical TOTEM Roman Pot and a tilted one, in the LHC tunnel. The rotation of the Roman Pots was one of the operations performed by the TOTEM collaboration during the LS1 upgrade programme.

The TOTEM experimental apparatus that will operate during Run 2 of the LHC will be significantly better than before: the Roman Pot detectors have been re-configured to resolve pile-up and prepared for the addition in the near future of high-precision time-of-flight detectors. In addition, their impedance characteristics have been significantly improved to allow the beam to be approached safely at higher intensities. Finally, following up on the Memorandum of Understanding signed in 2014 by TOTEM and CMS, the two experiments have worked on upgrading their data acquisition and read-out systems and building a common trigger.

In Run 1, the LHC operators performed dedicated runs with special optics to produce large beam sizes and smaller angular spread at the interaction points to allow TOTEM to probe the very small angle scattering regime. Thanks to the special runs in Run 2, TOTEM physicists will further investigate the interactions between the LHC protons that result exclusively in a modification of their direction of propagation (elastic scattering), and will precisely measure the total cross-section at the new LHC energy.

Besides the elastic scattering, TOTEM is also studying more complex interaction processes, known as “Pomeron-Pomeron interactions”. The new experimental apparatus makes it possible for TOTEM/CMS to be very flexible and perform measurements at a wide range of beam interaction scenarios both in special runs and standard LHC fills, up to full luminosity (β*values from 0.5m to ~ 2500m).

The upgraded instrumentation will provide TOTEM/CMS teams with an improved capability to tag protons in the very forward region (particles travelling at small angles with respect to the beam axis) and study the associated particle production at central rapidities (particles travelling at large angles with respect to the beam axis). During Run 2, for the first time, the collaboration will perform these studies over the complete invariant mass range up to 1 TeV, which represents a potential for discovery of new physics beyond the Standard Model by searching for missing energy events and new particle production. In addition, the improved capability to tag and measure produced masses in the low-energy (several GeV) region opens up unique opportunities for discovering new QCD bound states.

Totem is fully ready for the restart of the LHC to give even more interesting results.

by TOTEM Collaboration