On the interplay between astrophysical and laboratory probes of MeV-scale axion-like particles
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Springer
Received: April 27, 2020 Accepted: June 11, 2020 Published: July 8, 2020
Fatih Ertas and Felix Kahlhoefer Institute for Theoretical Particle Physics and Cosmology (TTK), RWTH Aachen University, D-52056 Aachen, Germany
E-mail: [email protected], [email protected] Abstract: Studies of axion-like particles (ALPs) commonly focus on a single type of interaction, for example couplings only to photons. Most ALP models however predict correlations between different couplings, which change the phenomenology in important ways. For example, an MeV-scale ALP coupled to Standard Model gauge bosons at high energies will in general interact with photons, W ± and Z bosons as well as mesons and nucleons at low energies. We study the implications of such scenarios and point out that astrophysical constraints, in particular from SN1987A, may be substantially relaxed, opening up new regions of parameter space that may be explored with laboratory experiments such as NA62. Keywords: Beyond Standard Model, Kaon Physics, Thermal Field Theory ArXiv ePrint: 2004.01193
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP07(2020)050
JHEP07(2020)050
On the interplay between astrophysical and laboratory probes of MeV-scale axion-like particles
Contents 1
2 Theoretical framework 2.1 ALP effective theory 2.2 Mixing effects of light ALPs 2.3 Interactions of light ALPs with photons and nucleons 2.4 Computation of K + → π + + a
3 3 4 5 6
3 Experimental and observational constraints 3.1 K + → π + + inv 3.2 Beam dump experiments 3.3 Z → γ + inv. 3.4 Astrophysical bounds
8 8 9 10 10
4 Results 4.1 Couplings to electroweak gauge bosons only 4.2 Couplings to all Standard Model gauge bosons
14 15 16
5 Conclusions
18
A Details on ALP interactions with hadrons
19
B Mixing contributions to K + → π + a
20
C Details on the computation of the ALP luminosity in SN1987A
21
D Uncertainties affecting the SN1987A cooling bounds
23
E Prospects of NA62 for signal region 2
24
1
Introduction
Axions, which were first introduced as a solution to the strong CP problem [1–4], have since been studied more generally as potential new pseudoscalar particles with small mass and tiny interaction rates with the Standard Model (SM) particle content. These candidates are then commonly referred to as Axion-like particles (ALPs). What makes them in particular intriguing is that they can arise as Pseudo-Goldstone bosons of a spontaneously broken approximate global symmetry explaining both their small mass and couplings. Since the ALP coupling strength to SM particles as well as their precise cosmological history are
–1–
JHEP07(2020)050
1 Introduction
• For a given ALP interaction at high scales we consider the effect of all induced lowenergy interactions. For example, if the ALP couples to SM SU(2)L gauge bosons we do not only include the resulting W boson interaction but also the effective ALPphoton coupling and the Zγa vertex. In the case of ALP-gluon interactions we include the induced
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