Nonresonant Searches for Axion-Like Particles in Vector Boson Scattering Processes at the LHC

Abstract

We propose a new search for Axion-Like Particles (ALPs), targeting Vector Boson Scattering (VBS) processes at the LHC. We consider nonresonant ALP-mediated VBS, where the ALP participates as an off-shell mediator. This process occurs whenever the ALP is too light to be produced resonantly, and it takes advantage of the derivative nature of ALP interactions with the electroweak Standard Model bosons. We study the production of ZZ, Zγ, W ± γ, W ± Z and W ± W ± pairs with large diboson invariant masses in association with two jets. Working in a gauge-invariant framework, upper limits on ALP couplings to electroweak bosons are obtained from a reinterpretation of Run 2 public CMS VBS analyses. The constraints inferred on ALP couplings to ZZ, Zγ and W ± W ± pairs are very competitive for ALP masses up to 100 GeV. They have the advantage of being independent of the ALP coupling to gluons and of the ALP decay width. Simple projections for LHC Run 3 and HL-LHC are also calculated, demonstrating the power of future dedicated analyses at ATLAS and CMS.

Prospects for detecting axion-like particles via the decay $Z\rightarrow af\bar{f}$ at future $Z$ factories

“…The bounds on the couplings of ALPs to gluons, photons, fermions and massive gauge bosons have been extensively studied [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Generally, the bounds depend on the ALP mass range considered.…”

“…The couplings of ALPs to the massive gauge bosons are constrained mainly due to loop induced ALP decaying into two photons [4,7] and flavor-changing neutral current meson decays [11]. Focusing on non-resonant ALP-mediated vector boson scattering processes, constraints on ALP-boson couplings are obtained from analysis of LHC RUN 2 data in a recent study [20], which include an upper bound g aZZ < 2.84 TeV −1 .…”

“…However, this strong constraint is based on an assumption g agg >> g aγZ , which will be released for a tiny gluonic coupling g agg . Additionally, non-resonant production of two bosons via the gluon-gluon fusion ("non-resonant ggF") [19] and non-resonant vector boson scattering ("non-resonant VBS") [20] can provide important constraints on g aZZ and g aγZ . However, the "non-resonant ggF" constraints can be lifted completely for g agg → 0 .…”

“…As ALPs coming from the breaking of a global symmetry at high energy scale, their interactions with ordinary particles can be suitably described via an effective Lagrangian and studied in effective field theory (EFT) framework [3][4][5]. The constraints on the effective couplings of ALPs to the SM fermions or bosons have been widely studied [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] using various experimental data from particle physics, astroparticle physics and cosmology. The severity of the constraints depends on the ALP mass range considered.…”

Axion-like ALPs

“…Currently, an increasing experimental task force is being born aiming to set bounds on the several couplings of ALPs to both fermions and gauge bosons of the SM. Additionally, these particles and their couplings have been extensively studied in the literature [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], following an Effective Field Theory (EFT) approach. Our goal in this paper is to analyze this formulation, and identify promising benchmarks.…”