ForwArd Search ExpeRiment at the LHC

By Jonathan L. Feng, I. Galon, F. Kling, S. Trojanowski. 2017

399 citations recorded by the source corpus.

New physics has traditionally been expected in the high-$p_T$ region at high-energy collider experiments. If new particles are light and weakly-coupled, however, this focus may be completely misguided: light particles are typically highly concentrated within a few mrad of the beam line, allowing sensitive searches with small detectors, and even extremely weakly-coupled particles may be produced in large numbers there. We propose a new experiment, ForwArd Search ExpeRiment, or FASER, which would be placed downstream of the ATLAS or CMS interaction point (IP) in the very forward region and operated concurrently there. Two representative on-axis locations are studied: a far location, $400~\text{m}$ from the IP and just off the beam tunnel, and a near location, just $150~\text{m}$ from the IP and right behind the TAN neutral particle absorber. For each location, we examine leading neutrino- and beam-induced backgrounds. As a concrete example of light, weakly-coupled particles, we consider dark photons produced through light meson decay and proton bremsstrahlung. We find that even a relatively small and inexpensive cylindrical detector, with a radius of $\sim 10~\text{cm}$ and length of $5-10~\text{m}$, depending on the location, can discover dark photons in a large and unprobed region of parameter space with dark photon mass $m_{A'} \sim 10 - 500~\text{MeV}$ and kinetic mixing parameter $\epsilon \sim 10^{-6} - 10^{-3}$. FASER will clearly also be sensitive to many other forms of new physics. We conclude with a discussion of topics for further study that will be essential for understanding FASER's feasibility, optimizing its design, and realizing its discovery potential.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/0befd89692082578ab9bd4bb9912c3eb6c887884

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Citations in the corpus

The Dark Photon (2020, methodology): “, 2018a) at the SPS; FASER and FASER2 (Feng et al., 2018) at the LHC; SeaQuest (Berlin et al.”
The Forward Physics Facility: Sites, experiments, and physics potential (2021, background): “At the LHC, they are dominantly produced through meson decays and bremsstrahlung in the region that would be covered by the FPF [1,4,79].”
Neutrinoless double beta decay versus other probes of heavy sterile neutrinos (2019, background): “These include AL3X [73], CODEX-b [74], FASER2 [75], MATHUSLA [76] and the MoEDAL experiment’s”
Detecting and studying high-energy collider neutrinos with FASER at the LHC (2019, methodology): “FASER, the Forward Search Experiment at the Large Hadron Collider (LHC) [17], covers this blind spot.”
Physics case for an LHCb Upgrade II - Opportunities in flavour physics, and beyond, in the HL-LHC era (2018, background): “Because the range of possible LLP lifetimes and masses is very large, many different existing and future experiments have searched for or proposed to search for LLPs, including ATLAS and CMS, Belle II, SHiP [671], FASER [672], MATHUSLA [673], and DUNE [674].”
Beyond the Standard Model Physics at the HL-LHC and HE-LHC (2018, methodology): “The Beyond Collider experiments are AL3X (A Laboratory for Long-Lived eXotics) [319], CODEX-b (COmpact Detector for EXotics at LHCb) [320], FASER (ForwArd Search ExpeRiment) [321–323], milliQan [324,325], MATHUSLA (MAssive Timing Hodoscope for Ultra Stable neutraL pArticles) [326,327], and SHiP (Sea”
FASER’s physics reach for long-lived particles (2018, methodology): “The side tunnels TI12 and TI18 are nearly ideal locations for FASER [7].”
Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider (2019, background): “The sensitivity of FASER to detect LLPs has been studied in a plethora of new physics models, including dark photons [105], dark Higgs bosons [469], HNLs [297], axion-like particles (ALPs) [470], iDM [471], flavor-specific scalar mediators [472], ( ) U 1 B L-gauge bosons [473], R-parity violating su”