750 GeV的共振（$S$）衰变为两个轻的轴子状粒子（ALPs $a$），这反过来又衰变为准直光子模仿观察到的信号的模型，是由隐谷的情况下，也可以提供一个机制，$S \to γγ$信号持续，而$S \to Z γ,\; ZZ$和$WW$保持在不久的将来抑制。我们指出，这些隐藏的山谷一样的模型调用$S \to aa \to 4 γ$还必须与$Z \to a (\to γγ) γ$来自CDF和ATLAS的约束。在一个有效的场论框架内，我们工作的约束$S$的耦合$a$和规范玻色子来自光子$Z$衰变，并确保ALP衰变内的电磁量能器，在两个制度-$a$衰变主要是光子，和$a$也有强子分支。当$S$具有大的以及窄的宽度时，以及对于来自$S \to γγ$和$a \to γγ$的信号的不同相对贡献，进行分析。结果的$S$和$a$属于同一个复杂的领域的特定情况下，也提出。在这类模型中，预期来自$Z \to a γ$的$Z$极点处的$γγ$共振。以基准ALP质量低于约0.4 GeV，并假设合理的假喷流率和识别效率的光子喷流的值，我们发现在$Z$极发现双光子的前景。
英文摘要：
Models in which the 750 GeV resonance ($S$) decays to two light axion-like particles (ALPs $a$), which in turn decay to collimated photons mimicking the observed signal, are motivated by Hidden Valley scenarios and could also provide a mechanism by which a $S \to γγ$ signal persists while $S \to Z γ,\; ZZ$ and $WW$ remain subdued in the near future. We point out that these Hidden Valley like models invoking $S \to aa \to 4 γ$ must also contend with $Z \to a (\to γγ) γ$ constraints coming from CDF and ATLAS. Within an effective field theory framework, we work out the constraints on the couplings of $S$ to $a$ and gauge bosons coming from photonic $Z$ decays and ensuring that the ALPs decay inside the electromagnetic calorimeter, in two regimes - where $a$ decays primarily to photons, and where $a$ also has hadronic branchings. The analysis is done for both when $S$ has a large as well as a narrow width, and for different relative contributions to the signal coming from $S \to γγ$ and $a \to γγ$. Results for the particular case where $S$ and $a$ belong to the same complex field are also presented. A $γγ$ resonance at the $Z$-pole coming from $Z \to a γ$ is expected in this class of models. Taking benchmark ALP masses below around 0.4 GeV and, assuming reasonable values for the fake jet rate and the identification efficiency of the photon-jet, we find the prospects for the discovery of diphotons at the $Z$-pole.
We investigate the physics case for a dedicated trigger-level analysis for very low mass diphoton resonances at ATLAS and CMS and introduce a new photon isolation criterion. This greatly increases the acceptance for light particles at the expense of a somewhat larger Standard Model background. We show how such an analysis would likely yield new experimental coverage for axion-like particles for masses below 15 GeV, bridging the gap with the region covered by flavor factories.
We have examined the sensitivity to the axion-like particle (ALP) couplings to electroweak gauge bosons in the diphoton production at a future muon collider. The collisions at the $μ^+ μ^-$ energies of 3 TeV, 14 TeV, and 100 TeV are addressed. The differential cross sections versus the invariant mass of the final photons and total cross section versus minimal diphoton invariant mass are presented. We have derived the exclusion regions for the ALP-gauge boson coupling. The obtained bounds are much stronger than the current experimental bounds in the ALP mass region 10 GeV -- 10 TeV. The partial…
The production of axionlike particles (ALPs) with small masses in ultraperipheral $Pb - p$ and $Pb - Pb$ collisions at the LHC is investigated. The cross section and kinematical distributions associated to the diphoton final state produced in the $γγ\rightarrow a \rightarrow γγ$ subprocesses are estimated considering a realistic set of kinematical cuts. A detailed analysis of the backgrounds is performed and the expected sensitivity to the ALP production is derived. Our results demonstrate that a future experimental analysis of the exclusive diphoton production for the forward rapidities probe…
The quantum chromodynamics axion with a decay constant near the Grand Unification (GUT) scale has an ultralight mass near a neV. We show, however, that axion-like particles with masses near the keV - PeV range with GUT-scale decay constants are also well motivated in that they naturally arise from axiverse theories with dark non-abelian gauge groups. We demonstrate that the correct dark matter abundance may be achieved by the heavy axions in these models through the misalignment mechanism in combination with a period of early matter domination from the long-lived dark glueballs of the same gau…
We perform a feasibility study to search for axion-like particles (ALPs) using vector boson fusion (VBF) processes at the LHC. We work in an effective field theory framework with cutoff scale $Λ$ and ALP mass $m_{a}$, and assume that ALPs couple to photons with strength $\propto 1/Λ$. Assuming proton-proton collisions at $\sqrt{s} = 13$ TeV, we present the total VBF ALP production cross sections, ALP decay widths and lifetimes, and relevant kinematic distributions as a function of $m_{a}$ and $Λ$. We consider the $a\toγγ$ decay mode to show that the requirement of an energetic diphoton pair co…
Axion-like particles (ALPs) decaying into photons are known to affect a wide range of astrophysical and cosmological observables. In this study we focus on ALPs with masses in the keV-MeV range and lifetimes between $10^4$ and $10^{13}$ seconds, corresponding to decays between the end of Big Bang Nucleosynthesis and the formation of the Cosmic Microwave Background (CMB). Using the CosmoBit module of the global fitting framework GAMBIT, we combine state-of-the-art calculations of the irreducible ALP freeze-in abundance, primordial element abundances (including photodisintegration through ALP de…
