Gauge boson signals at the cosmological collider
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Springer
Received: April 30, Revised: September 10, Accepted: October 5, Published: November 17,
2020 2020 2020 2020
Lian-Tao Wanga and Zhong-Zhi Xianyub a
Department of Physics, University of Chicago, Chicago, IL 60637, U.S.A. b Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, U.S.A.
E-mail: [email protected], [email protected] Abstract: We study the production of massive gauge bosons during inflation from the axion-type coupling to the inflaton and the corresponding oscillatory features in the primordial non-Gaussianity. In a window in which both the gauge boson mass and the chemical potential are large, the signal is potentially reachable by near-future large scale structure probes. This scenario covers a new region in oscillation frequency which is not populated by previously known cosmological collider models. We also demonstrate how to properly include the exponential factor and discuss the subtleties in obtaining power dependence of the gauge boson mass in the signal estimate. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM ArXiv ePrint: 2004.02887
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP11(2020)082
JHEP11(2020)082
Gauge boson signals at the cosmological collider
Contents 1 Introduction
1
2 Framework
4
signal Gauge boson production Approximating the propagators Estimate of signal size Explicit calculation
7 7 10 11 13
4 Constraints
17
5 Discussions
19
A More on estimating the signal strength
20
1
Introduction
Cosmological inflation in the early universe sets the stage for rich dynamics of particle physics at energy scales much above the reach of terrestrial experiments. In the coming decades, much more observational data will further shed light in this era. In particular, the precision in the primordial Non-Gaussianity (NG) measurement will be improved by orders of magnitudes [1]. Among various NG observables, the oscillatory shape in the squeezed limit due to particle production during the inflation is particularly striking. (We will henceforth refer to this oscillatory shape the “signal.”) Detecting such a signal at this so-called cosmological collider offers direct evidence of new physics particles and a tool of studying their properties [2–23]. The strength of the signal depend sensitively on the coupling between the inflaton and the new physics particles. One key difference between the cosmological collider and a terrestrial collider experiment is that the interaction with the inflaton can change the spectrum of the new physics particles significantly. Very often, the signal size is exponentially sensitive to the mass. Hence, we will only have observable signals with couplings of specific types [21]. This leads us to focus on a specific class of couplings by assuming the inflaton has an approximate shift symmetry, φ → φ + c, which is well motivated by the requirement of slow roll inflation. In [21], it is further argued that a sub-class of such couplings are particularly prom
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