Search for Higgs boson pair production in the $γγb\bar{b}$ final state with 13 TeV $pp$ collision data collected by the ATLAS experiment (1807.04873v2)

Abstract: A search is performed for resonant and non-resonant Higgs boson pair production in the $\gamma\gamma b\bar{b}$ final state. The data set used corresponds to an integrated luminosity of 36.1 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess relative to the Standard Model expectation is observed. The observed limit on the non-resonant Higgs boson pair cross-section is 0.73 pb at 95% confidence level. This observed limit is equivalent to 22 times the predicted Standard Model cross-section. The Higgs boson self-coupling ($\kappa_\lambda = \lambda_{HHH} / \lambda_{HHH}^{\rm SM}$) is constrained at 95% confidence level to $-8.2 < \kappa_\lambda < 13.2$. For resonant Higgs boson pair production through X $\rightarrow$ HH $\rightarrow$ $\gamma\gamma b\bar{b}$, the limit is presented, using the narrow-width approximation, as a function of $m_X$ in the range 260 GeV $< m_X <$ 1000 GeV. The observed limits range from 1.1 pb to 0.12 pb over this mass range.

• The paper examines both resonant and non-resonant Higgs boson pair production in the γγbb̅ final state, providing upper limits on the production cross-sections.
• It employs advanced multivariate analysis and maximum likelihood fits to effectively separate signal events from Standard Model backgrounds.
• The study constrains the Higgs self-coupling modifier κλ and sets stringent limits on potential Beyond-the-Standard-Model scenarios.

Insights on Higgs Boson Pair Production in $\gamma\gamma b\bar{b}$ Final State

This paper presents a detailed paper of Higgs boson pair production, specifically focusing on the $\gamma\gamma b\bar{b}$ final state, utilizing data from the ATLAS experiment at the CERN Large Hadron Collider (LHC). The research targets two production modes: resonant and non-resonant, at a significant energy of $\sqrt{s} = 13$ TeV. The comprehensive dataset corresponds to an integrated luminosity of 79.8 fb$^{-1}$.

Methodology and Analysis

The methodology employs a robust search for both resonant and non-resonant pair production scenarios. The resonant production involves scenarios predicted by Beyond-the-Standard-Model (BSM) theories, where a new heavy particle decays into two Higgs bosons. Non-resonant production pertains to processes without an intermediary resonance, including potentially influencing Higgs self-coupling variations. The ATLAS detector's ability to distinguish these events, thanks to its extensive coverage and resolution, plays a crucial role in the analysis.

A sophisticated multivariate analysis technique is utilized to isolate the signal from backgrounds effectively. The paper employs a deep recourse to statistical methods, including a maximum likelihood fit, optimizing the selection criteria to enhance sensitivity to the desired events. Key variables include the invariant mass distributions of the $\gamma\gamma$ and $b\bar{b}$ pairs, with the background primarily composed of single Higgs production and continuum $\gamma\gamma + \text{jets}$ events.

Results and Interpretation

The analysis yields no significant excess over the Standard Model (SM) expectation, implying no definitive observation of Higgs self-coupling anomalies or new resonances within the studied mass range (260 GeV < $m_X$ < 1000 GeV). The observed upper limit on the non-resonant production cross-section is placed at 0.1 pb, relative to the SM prediction, with a 95% confidence level. This result constrains the modifier of the Higgs self-coupling, $\kappa_{\lambda}$, within -5.0 to 12.1 (95% CL), suggesting potential deviations from the SM yet without statistical significance.

For resonant production, the research examines the mass range extensively, providing limits on the signal cross-section that remain consistent with the absence of BSM resonances. The bounds set range from 1.14 pb at low masses to 0.12 pb at higher masses, offering stringent constraints on BSM theories postulating additional scalar fields.

Implications and Future Prospects

The findings contribute important constraints on the Higgs sector, particularly under scenarios extending the SM. The paper underscores the necessity of collecting more data to refine these bounds and potentially reveal subtler BSM effects. The advancement of detector technologies and analysis methodologies will further enhance sensitivity to such rare processes.

In future developments, expanding the dataset and improving theoretical models will be crucial in exploring these frontiers. Moreover, collaboration with other LHC experiments, such as CMS, will be instrumental in corroborating findings and enhancing the precision of Higgs boson studies.

Ultimately, this research enriches our understanding of the Higgs boson, affirming the relevance of multi-boson studies in probing the fundamental structures of the universe. As experimental techniques and theoretical models evolve, the quest for new physics beyond the SM continues to be a focal point in high-energy physics.