“School of Particles”
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| Paper IPM / Particles / 18232 |
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| Abstract: | |||||
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Axion-like particles (ALPs) are pseudo Nambu-Goldstone bosons associated with spontaneously broken
global symmetries incorporated in the Standard Model (SM) Lagrangian in many models beyond the SM.
The existence of a light ALP is plausible due to the long-standing problems that the SM has not been able
to address, such as the dark matter (DM) problem and the observed matter-antimatter asymmetry.
There are many proposals in recent decades considering the ALP as a solution to some of these shortcomings.
Motivated by such potential, we search for ALPs with a mass of 1 MeV at the LHC in a model-independent fashion.
We explore two complementary production modes: ALP production in association with a pair of electroweak gauge
bosons ($ZZ$ or $WW$) and ALP production in association with a single gauge boson ($W$ or $Z$) plus jets.
For the $VV+a$ final state, signal and dominant SM backgrounds are generated, and a realistic detector response simulation is performed.
A multivariate analysis is employed to discriminate the $VV+a$ signal from background processes, and the expected
$95\%$ confidence level (CL) exclusion limits in two-dimensional parameter spaces involving the ALP couplings are subsequently derived.
The $V$+jets channel is interpreted using LHC measurements in regimes where the
ALP escapes detection, appearing as missing energy.
The two analyses are complementary: both the $VV+a$ and the $V$+jets channels probe simultaneously the
ALP couplings to gluons and to electroweak gauge bosons. While the $VV+a$ channel offers clean multi-lepton
final states and direct reconstruction of the $ZZ$ or $WW$ system, the $V$+jets channel benefits from larger
production cross sections, enabling stronger constraints in certain regions of the parameter space.
Comparing the limits obtained in this study with current and projected limits derived from LHC searches,
it is seen that competitive sensitivities to the ALP couplings are achieved, and a significant region of previously unexplored parameter space becomes accessible.
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