Detector-size upper bounds on dark hadron lifetime from cosmology
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Springer
Received: February Revised: April Accepted: April Published: May
12, 18, 30, 14,
2019 2019 2019 2019
Lingfeng Lia and Yuhsin Tsaib a
Jockey Club Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong S.A.R. b Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD 20742, U.S.A.
E-mail: [email protected], [email protected] Abstract: We show that in a confining hidden valley model where the lightest hidden particles are dark hadrons that have mass splittings larger than O(0.1) GeV, if the lightest dark hadron is either stable or decays into Standard Model (SM) hadrons/charged leptons during the big-bang nucleosynthesis (BBN), at least one of the heavier dark hadrons needs to decay into SM particles within O(10) nanosec. Once being produced at collider experiments, this heavier dark hadron is likely to decay within O(1) meter distance, which strengthens the motivation of searching for long-lived particles with sub-meter scale decay lengths at colliders. To illustrate the idea, we study the lifetime constraint in scenarios where the lightest dark particle is a pseudo-scalar meson, and dark hadrons couple to SM particles either through kinetic mixing between the SM and dark photons or by mixing between the SM and dark Higgs. We study the annihilation and decay of dark hadrons in a thermal bath and calculate upper bounds on the lightest vector meson (scalar hadron) lifetime in the kinetic mixing (Higgs portal) scenario. We discuss the application of these lifetime constraints in long-lived particle searches that use the LHCb VELO or the ATLAS/CMS inner detectors. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM ArXiv ePrint: 1901.09936
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP05(2019)072
JHEP05(2019)072
Detector-size upper bounds on dark hadron lifetime from cosmology
Contents 1 Introduction
1
2 Evolution of the hidden hadron density
4 8 8 11
4 Application to the long-lived particle searches 4.1 Vector meson decay in the photon mixing scenario 4.2 Scalar hadron decay in the Higgs portal scenario 4.3 Dark shower signals
13 14 16 18
5 Conclusion
18
1
Introduction
A Confining Hidden Valley (CHV) containing dark hadrons which weakly couple to SM particles appears in many beyond the SM scenarios. Such CHV models have been used to solve the Higgs hierarchy problem [1–6], strong CP problem [7, 8], and address astrophysical and cosmological anomalies [9–13]. Neutral hadrons in a CHV sector which are not stabilized by a symmetry can slowly decay into SM particles. The resulting long-lived particle (LLP) signatures have motivated active research programs aiming to improve searches in the existing detectors [14–21] and to propose new experiments [22–26]. Existing searches from the LHCb, ATLAS, and CMS collaborations have already set useful constrains on dark hadron production, see e.g. [27] for a review of the previous searches, and [28–31]
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