Core Viewpoint - The ATLAS team at CERN has made significant advancements in understanding the Higgs boson, providing strong evidence for its decay into muons and improving detection sensitivity for its decay into Z bosons and photons, potentially revealing physics beyond the Standard Model [1][3][6][7]. Group 1: Higgs Boson Decay Findings - The ATLAS experiment aims to address fundamental questions regarding the consistency of Higgs interactions with the Standard Model and whether it is the sole source of mass for all fundamental particles [8]. - The decay process H→μμ (Higgs boson decaying into a pair of muons) is extremely rare, occurring approximately once in every 5,000 Higgs decays [9]. - Despite its rarity, this decay provides the best opportunity to study the interaction between the Higgs boson and second-generation fermions, which is crucial for understanding the origin of mass for different generations of particles [10]. - Identifying this rare decay is challenging due to its signal being easily obscured by thousands of muon pairs produced through other processes [11]. - The ATLAS experiment utilized data from different operational phases of the LHC, including Run-2 and Run-3, and developed complex background modeling methods to classify recorded events and improve signal detection [12]. - By combining data from Run-2 and Run-3, ATLAS has observed evidence for H→μμ decay with a significance of 3.4 standard deviations, indicating a less than 0.3% probability of statistical fluctuation [13][14]. Group 2: H→Zγ Decay Findings - The decay H→Zγ involves the Higgs boson decaying into a Z boson and a photon, with the Z boson further decaying into electron or muon pairs [17]. - This decay is also rare and occurs through a virtual particle "loop," which could provide clues to physics beyond the Standard Model if new particles contribute to this loop [18]. - Identifying H→Zγ decay is challenging, as the Z boson decays into detectable leptons only about 6% of the time, significantly reducing its observability [18]. - The complex conditions of LHC Run 3, including increased pile-up collisions, further complicate the identification of H→Zγ signals [18]. - By combining data from Run-2 and Run-3 and employing advanced modeling and event classification techniques, ATLAS reported an excess observation for H→Zγ decay with a significance of 2.5 standard deviations, providing the most stringent expected sensitivity for measuring the branching ratio of this decay to date [19]. Group 3: Background Knowledge on Higgs Boson - The Higgs boson, also known as the "God particle," was proposed by Nobel laureate Peter Higgs and is a zero-spin boson that is electrically and color neutral, highly unstable, and decays almost immediately after being produced [24][25]. - The term "God particle" originated from a 1993 book by physicist Leon Lederman, who initially intended to use a more vulgar term but opted for a more marketable name [27]. - The Higgs boson is a manifestation of the Higgs field, which is hypothesized to permeate the universe, allowing certain fundamental particles to acquire mass through their interaction with this field [34][35]. - The Standard Model describes the fundamental forces and particles, including fermions and bosons, and explains how particles acquire mass through the Higgs mechanism [37][39].