The FP420 R&D Project: Higgs and New Physics with forward protons at the LHC (0806.0302v2)

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 + phi + p, in which the outgoing protons remain intact and the central system phi may be a single particle such as a SM or MSSM Higgs boson. Other physics topics discussed are gamma-gamma and gamma-p interactions, and diffractive processes. The report includes a detailed study of the trigger strategy, acceptance, reconstruction efficiencies, and expected yields for a particular p p --> p H p measurement with Higgs boson decay in the b-bbar 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.

Summary of the FP420 R&D Project: Higgs and New Physics with Forward Protons at the LHC

The FP420 R&D project is a proposal for the installation of cutting-edge forward proton detectors in the LHC tunnel, specifically positioned at 420 meters from the interaction points of the ATLAS and CMS experiments. These detectors aim to precisely measure very forward proton momentum and timing in conjunction with central detectors, thereby facilitating specialized studies of the Standard Model (SM) physics and enhancing the search for New Physics phenomena. The primary goal is to leverage the Central Exclusive Production (CEP) mechanism to explore elusive particles such as the Higgs boson within different theoretical frameworks including the SM and MSSM.

Key Aspects of the Project

1. Proton Detection and Beam Optics:
   • The FP420 detectors measure scattered protons through a magnetic spectrometer setup, utilizing silicon tracking systems. Achieving precise spatial and angular measurements enables accurate calculation of proton momentum loss and transverse momentum, fundamental to reconstructing the mass of centrally produced systems.
   • Juvenile chromaticity grids assist in visualizing proton energy and emission angle correlations, crucial for optimizing detector design and analysis strategies.
2. Technical Design and Implementation:
   • A new connection cryostat design will replace existing structures at strategic tunnel locations. Enhanced with modified Arc Termination Modules, this structure incorporates room temperature regions to accommodate detector setups.
   • The use of Hamburg moving pipes is central, allowing detector insertion near the beam with minimal intrusiveness, facilitating simplified maintenance and lower risk to LHC operations.
3. Signal and Background Analysis:
   • Through simulations, various backgrounds such as double pomeron exchanges and overlap events are analyzed. Fast timing capability (targeting 10 ps resolution) assists in distinguishing legitimate signal production, especially amidst high luminosity-induced pile-up challenges.
   • Innovative trigger strategies integrate central and forward proton detection info, refining event selection for heightened sensitivity to CEP processes targeting Higgs production.
4. Theoretical Implications:
   • The research highlights theoretical predictions for cross sections across SM and MSSM frameworks, focusing on accessible signatures in a Higgs search. These studies inform the potential experimental reach, demonstrating expanded access to parameter spaces not available through traditional detection methods.
5. Future Research Directions:
   • The project's roadmap outlines testing phases, including beam tests and pilot runs, to refine detector technology and integration with LHC large-scale systems.
   • Future upgrades consider drift to enhanced timing resolution and detector efficiency, necessary to sustain research objectives as LHC transitions to higher luminosity phases.

Conclusion

The FP420 R&D project proposes transformative advancements in forward proton detection technologies, potentially elevating the standard in particle collider experiments. By enabling breakthroughs in the paper of CEP processes, the project stands to uniquely enrich the LHC's science output, priming it for discoveries in Higgs physics and beyond the Standard Model scenarios. The detailed design and comprehensive analysis encapsulated within this report exemplify the potential precision and scientific impact that forward proton tagging may contribute to high-energy particle physics.