Introduces echo signatures from vector long-lived particles in nucleon decay, showing high geometric acceptance up to 80% in Super-K, Hyper-K and JUNO for a range of decay lengths.
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FASER's Physics Reach for Long-Lived Particles
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abstract
FASER,the ForwArd Search ExpeRiment,is a proposed experiment dedicated to searching for light, extremely weakly-interacting particles at the LHC. Such particles may be produced in the LHC's high-energy collisions and travel long distances through concrete and rock without interacting. They may then decay to visible particles in FASER, which is placed 480 m downstream of the ATLAS interaction point. In this work we briefly describe the FASER detector layout and the status of potential backgrounds. We then present the sensitivity reach for FASER for a large number of long-lived particle models, updating previous results to a uniform set of detector assumptions, and analyzing new models. In particular, we consider all of the renormalizable portal interactions, leading to dark photons, dark Higgs bosons, and heavy neutral leptons (HNLs); light B-L and $L_i - L_j$ gauge bosons; axion-like particles (ALPs) that are coupled dominantly to photons, fermions, and gluons through non-renormalizable operators; and pseudoscalars with Yukawa-like couplings. We find that FASER and its follow-up, FASER 2, have a full physics program, with discovery sensitivity in all of these models and potentially far-reaching implications for particle physics and cosmology.
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representative citing papers
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A forward neutrino detector at a muon collider can exceed current and upcoming bounds on non-standard neutrino interactions by exploiting high neutrino flux, known flavor composition, and chirality.
Classically conformal SU(2)_X model with triplet dark scalar yields viable WIMP and supercooled DM parameter spaces whose production histories are set by the model's first-order phase transition, with gravitational waves as a common probe.
Radiative electroweak symmetry breaking with a logarithmic potential yields analytical vacuum solutions, four thermal history patterns, and supercooled FOPT gravitational waves whose signals combined with collider data can probe conformal scales to 10^5-10^8 GeV.
Hybrid string-bounded domain wall networks from sequential U(1)_F and Z2 symmetry breaking generate a GW spectrum with a unique low-frequency slope that future detectors can observe and an MLP surrogate can characterize for fast SNR inference.
Phenomenological study predicting incomplete tau polarization at FASER2, observable neutrino and muon trident processes, and contributions to hadron structure from IceCube neutrino events.
The paper surveys theoretical motivations, experimental searches, and bounds on the dark photon as a kinetically mixed gauge boson from a dark sector, covering both massive and massless cases along with related milli-charged fermion constraints.