Abstract
We present the FP420 R&D project, which has been studying the key aspects of the development and installation of a silicon tracker and fast-timing detectors in the LHC tunnel at 420 m from the interaction points of the ATLAS and CMS experiments. These detectors would measure precisely very forward protons in conjunction with the corresponding central detectors as a means to study Standard Model (SM) physics, and to search for and characterise new physics signals. This report includes a detailed description of the physics case for the detector and, in particular, for the measurement of Central Exclusive Production, pp→p+ϕ+p, in which the outgoing protons remain intact and the central system ϕ may be a single particle such as a SM or MSSM Higgs boson. Other physics topics discussed are γγ and γp interactions, and diffractive processes. The report includes a detailed study of the trigger strategy, acceptance, reconstruction efficiencies, and expected yields for a particular pp→pHp measurement with Higgs boson decay in the bb̄ mode. The document also describes the detector acceptance as given by the LHC beam optics between the interaction points and the FP420 location, the machine backgrounds, the new proposed connection cryostat and the moving (``Hamburg'') beam-pipe at 420 m, and the radio-frequency impact of the design on the LHC. The last part of the document is devoted to a description of the 3D silicon sensors and associated tracking performances, the design of two fast-timing detectors capable of accurate vertex reconstruction for background rejection at high-luminosities, and the detector alignment and calibration strategy.
Highlights
1.1 Executive summary forward proton detectors have been used to study Standard Model (SM) physics for a couple of decades, the benefits of using proton detectors to search for New Physics at the LHC have only been fully appreciated within the last few years [1, 2, 3, 4, 5, 6]
2.1 Introduction A forward proton tagging capability can enhance the ability of the ATLAS and CMS detectors to carry out the primary physics program of the LHC
By central exclusive production we refer to the process pp → p + φ + p, where the ‘+’ signs denote the absence of hadronic activity between the outgoing protons and the decay products of the central system φ
Summary
1.1 Executive summary forward proton detectors have been used to study Standard Model (SM) physics for a couple of decades, the benefits of using proton detectors to search for New Physics at the LHC have only been fully appreciated within the last few years [1, 2, 3, 4, 5, 6]. A forward proton tagging capability can enhance the ability of the ATLAS and CMS detectors to carry out the primary physics program of the LHC This includes measurement of the mass and quantum numbers of the Higgs boson, should it be discovered via traditional searches, and augmenting the discovery reach if nature favours certain plausible beyond the Standard Model scenarios, such as its minimal supersymmetric extension (MSSM). In order to detect protons from the production of central systems of masses ∼ 100 GeV/c2, the detector edge has to approach the beam axis to a minimum distance of 5 mm (see Figure 28) This represents a challenge for the radiation hardness and radio-frequency pick-up in the detector and the nearby front-end electronics, as described in Sections 5 and 8. These results have to be confirmed and crosschecked with BDSIM
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