FASER

FASER
Name	FASER
Location	CERN, Geneva
Established	2019
Detector type	Forward physics experiment
Energy	LHC Run 3

FASER FASER is a small, forward particle physics experiment installed in the Large Hadron Collider tunnel near ATLAS at CERN designed to search for light, weakly interacting particles produced in proton–proton collisions. The experiment was proposed by a multinational team including researchers from institutions associated with University of Oxford, University of California, Berkeley, Stanford University, and Imperial College London and was installed during an upgrade phase prior to LHC Run 3 operations. FASER complements larger detectors such as CMS, ATLAS, LHCb, and ALICE by targeting long-lived particles predicted in models related to the Higgs boson, axion, and dark matter.

Overview

FASER occupies a service tunnel downstream of the ATLAS interaction point inside the Large Hadron Collider complex and was proposed following theoretical studies by groups connected to University of Cambridge, Harvard University, Princeton University, and ETH Zurich. The conceptual design built upon work from collaborations at Fermilab, SLAC National Accelerator Laboratory, Brookhaven National Laboratory, and DESY and was reviewed by committees including members from CERN management and the European Organization for Nuclear Research. The project timeline included approval alongside detector upgrades for LHC Run 3 and coordination with infrastructure teams from Geneva and technical divisions associated with CERN Accelerator operations.

Detector Design

The detector comprises a magnetized decay volume, tracking stations based on technologies developed at KEK, calorimetry inspired by designs from Fermilab and DESY, and a scintillator veto system similar to detectors at Super-Kamiokande, NOvA, and MINERvA. The tracking system uses silicon strip and scintillating fiber technologies deployed previously at LHCb, CMS, and ATLAS upgrade programs, and the calorimeter modules draw on prototypes tested at CERN SPS test beams and facilities at SLAC and Brookhaven National Laboratory. The magnet design incorporated engineering expertise from Siemens, ABB, and technical groups from CERN and the cryostat systems leveraged experience from ITER and HERA projects.

Physics Goals

FASER targets signatures of light, weakly interacting particles such as dark photons, axion-like particles, heavy neutral leptons, and other long-lived particles predicted in extensions of the Standard Model discussed at conferences like Rencontres de Moriond, ICHEP, and Neutrino 2020. The experiment seeks displaced decays in a low-background environment to test models motivated by anomalies reported in datasets from BaBar, Belle II, and AMS-02, and to probe parameter space complementary to searches at ATLAS, CMS, and fixed-target facilities such as NA62 and SHiP. FASER's sensitivity was evaluated with simulations using frameworks developed at CERN and validations drawing on results from LHCb and precision measurements at LEP and Tevatron.

Operation and Data Taking

FASER began data taking during LHC Run 3 with integration into the CERN control network, coordination with ATLAS operations, and scheduling with the LHC machine coordinators. The experiment's trigger and data acquisition systems used hardware and firmware concepts similar to those deployed at CMS, ATLAS, and LHCb, and data calibration pipelines adopted software tools from ROOT and computing resources provided by the Worldwide LHC Computing Grid and national centers such as CERN OpenLab, NERSC, and GridPP. Run plans were coordinated with beam physicists from CERN Accelerator Division and detector downtime scheduled according to maintenance windows defined with ATLAS and LHCb detector teams.

Results and Publications

FASER published initial commissioning and performance papers authored by collaborations including scientists from University of Oxford, University of Tokyo, Max Planck Institute for Physics, INFN, and CEA Saclay with results presented at conferences such as ICHEP, EPS-HEP, and LHCP. Preliminary searches produced limits that constrain models previously discussed in papers from groups at Caltech, MIT, University of Chicago, and Columbia University, and results have been compared to constraints from experiments including BaBar, Belle II, NA62, and E137. The collaboration communicates findings through peer-reviewed journals and preprints circulated on the arXiv and presented at workshops with participation from representatives of DOE, ERC, and national funding agencies.

Collaborations and Funding

The collaboration comprises universities and laboratories such as University of Oxford, Imperial College London, University of California, Berkeley, Stanford University, CERN, DESY, KEK, and INFN with technical contributions from Fermilab and SLAC National Accelerator Laboratory. Funding and support have been provided by national agencies including UK Research and Innovation, United States Department of Energy, National Science Foundation, European Research Council, Swiss National Science Foundation, Japan Society for the Promotion of Science, and institutional grants from affiliated universities. The project leverages shared resources coordinated via memoranda of understanding executed among participating institutions and the CERN management structure.

Category:Particle detectors