Light hidden mesons through the Z portal

Abstract

Confining hidden sectors are an attractive possibility for physics beyond the Standard Model (SM). They are especially motivated by neutral naturalness theories, which reconcile the lightness of the Higgs with the strong constraints on colored top partners. We study hidden QCD with one light quark flavor, coupled to the SM via effective operators suppressed by the mass M of new electroweak-charged particles. This effective field theory is inspired by a new tripled top model of supersymmetric neutral naturalness. The hidden sector is accessed primarily via the Z and Higgs portals, which also mediate the decays of the hidden mesons back to SM particles. We find that exotic Z decays at the LHC and future Z factories provide the strongest sensitivity to this scenario, and we outline a wide array of searches. For a larger hidden confinement scale Λ ∼ O(10) GeV, the exotic Z decays dominantly produce final states with two hidden mesons. ATLAS and CMS can probe their prompt decays up to M ∼ 3 TeV at the high luminosity phase, while a TeraZ factory would extend the reach up to M ∼ 20 TeV through a combination of searches for prompt and displaced signals. For smaller Λ ∼ O(1) GeV, the Z decays to the hidden sector produce jets of hidden mesons, which are long-lived. LHCb will be a powerful probe of these emerging jets.Furthermore, the light hidden vector meson could be detected by proposed dark photon searches.

Collider constraints on dark mediators

“…In this work, we answer these questions for scenarios where a t-channel mediator communicates between the standard model (SM) and a QCD-like dark sector. This complements and extends similar studies for minimal dark sectors [1][2][3], as well as searches for complex dark sectors coupled via s-channel mediators [4][5][6][7][8][9][10][11][12][13][14].…”

Searching for elusive dark sectors with terrestrial and celestial observations

“…Previous studies of the phenomenology of dark sectors coupled to the SM through irrelevant portals include refs. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. While these papers have some aspects in common with our work and some of their assumptions are similar to ours, we believe that our approach is original and our analysis extends previous results.…”

Detecting and studying high-energy collider neutrinos with FASER at the LHC

“…The FASER location is currently being prepared with lighting and power, and a passarelle (stairs) and support structures are already in place to safely transport detector components around the LHC. In this location, starting in Run 3 from 2021-23, FASER will provide sensitive searches for many proposed light and very weakly-interacting particles, such as dark photons, axion-like particles, and light gauge bosons [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”