FP420

FP420. FP420 was a proposed international research project to install advanced proton spectrometers in the forward regions of the Large Hadron Collider (LHC) interaction points at CERN. The initiative aimed to complement the central detectors of the ATLAS and CMS collaborations by measuring protons scattered at very small angles. This capability was designed to provide unique insights into electroweak symmetry breaking and to search for new physics beyond the Standard Model.

Overview

The project derived its name from the proposed placement of detectors approximately 420 meters from the LHC interaction points. This strategic position was chosen to detect protons that lose a small fraction of their momentum in high-energy collisions and are deflected by the LHC magnetic lattice. By precisely measuring the kinematics of these forward protons, physicists could reconstruct the mass and quantum numbers of centrally produced systems with high resolution. The concept built upon earlier techniques pioneered at the CERN Intersecting Storage Rings and the Tevatron at Fermilab.

Detector Design

The FP420 detector design centered on installing sophisticated tracking stations inside movable beam pipes, known as "Roman Pots," positioned close to the LHC beam. These stations would employ ultra-thin silicon sensors to measure the trajectory of protons with micron-level precision without interfering with the primary beam. Key sub-detector technologies included 3D silicon sensors for tracking and scintillating fibre hodoscopes for precise timing measurements. The entire system required integration with the existing ATLAS experiment and CMS experiment infrastructure and their complex trigger systems.

Physics Goals

A primary physics goal was the study of Central Exclusive Production, particularly for the Higgs boson. FP420 aimed to measure the rare process where the Higgs boson is produced alone, with the colliding protons remaining intact, offering a clean experimental signature. This would allow precise measurements of the Higgs boson quantum numbers, such as its CP properties. Furthermore, the project sought to explore signals of supersymmetry, search for new heavy resonances like excited quarks, and investigate anomalous vector boson couplings in processes involving W and Z bosons.

Technical Challenges

The implementation faced significant hurdles due to the extreme radiation environment and the need for exceptional positional stability near the LHC beam. Developing radiation-hard sensors and electronics that could withstand doses exceeding 10^16 protons per square centimeter was a major engineering endeavor. Synchronizing the proton timing measurements with the central ATLAS experiment and CMS experiment events to within a few picoseconds posed another critical challenge. Additionally, aligning the Roman Pot detectors to within micrometers relative to the beam required novel precision mechanics and control systems.

Collaboration and Timeline

The FP420 collaboration was a joint effort between the ATLAS experiment and CMS experiment communities, involving institutes from the United Kingdom, the United States, Germany, Italy, and Russia. An extensive Research and development program was conducted throughout the mid-2000s, producing numerous technical design reports and prototype tests. While the project generated considerable interest and advanced detector technologies, it was not installed during the initial runs of the Large Hadron Collider. Many of its scientific goals and technical concepts were subsequently pursued by the ATLAS Forward Proton and CMS-TOTEM Precision Proton Spectrometer projects. Category:High energy physics experiments Category:CERN experiments Category:Proposed particle physics experiments