Boosted objects and jet substructure at the LHC (1311.2708v2)

Abstract: This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of the description of jet substructure in first-principle QCD calculations and study the accuracy of state-of-the-art Monte Carlo tools. Experimental limitations of the ability to resolve substructure are evaluated, with a focus on the impact of additional proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt during the deployment of substructure analyses in searches for new physics in the production of boosted top quarks.

Insights into Boosted Objects and Jet Substructure at the LHC

The workshop report titled "Boosted objects and jet substructure at the LHC," stemming from BOOST2012, explores advancements and challenges in the paper of jet substructure, especially in high-energy environments like the LHC. This work is pivotal for researchers focusing on jets arising from hadronic decays of boosted objects such as top quarks, W and Z bosons, and potentially new physics particles. It presents findings from multiple working groups on the predictive power and experimental handling of jet substructure.

Theoretical and Computational Developments

A primary focus of the report is on the theoretical prediction capabilities of jet substructure through first-principle QCD calculations. These calculations are essential for providing an accurate description, especially when considering resummation of leading logarithms. The integration of first-principle calculations into current methodologies aims to enhance precision and reduce uncertainties inherent in traditional models. The discussions highlight the use of both perturbative QCD and Soft Collinear Effective Theory (SCET) in advancing the description of jet invariant mass, with promising results pointing towards meaningful comparisons with empirical data soon.

Moreover, Monte Carlo simulations still play a crucial role in predicting jet substructure's behavior in various scenarios. The report examines several mainstream Monte Carlo generators, noting discrepancies, especially regarding the accuracy of jet mass predictions. Techniques such as jet grooming—namely trimming, filtering, and pruning—are emphasized for their ability to reconcile differences among Monte Carlo models and improve simulation outcomes.

Experimental Implications and Challenges

From an experimental perspective, the impact of simultaneous proton-proton interactions (pile-up) on jet reconstruction is thoroughly investigated. Despite significant challenges posed by pile-up, strategies involving combined pile-up subtraction and jet grooming techniques have shown effectiveness in preserving the jet mass scale and mitigating resolution degradation. This is particularly crucial as the LHC prepares for high-luminosity phases where pile-up levels are expected to soar.

Applications in Searches and Measurements

The application of these techniques in the search for new physics, particularly the production of boosted top quarks, is scrutinized. The deployment of top tagging strategies in ATLAS and CMS experiments has notably enhanced sensitivity to massive new states decaying to $t\bar{t}$ pairs. These advancements underline the necessity and effectiveness of specifically tailored approaches for boosted topology analyses.

The report notes a remarkable increase in exclusions for new physics scenarios, such as $t\bar{t}$ resonances, in recent searches—pointing to the efficacy of boosted-object techniques developed during the initial phases of LHC operations. Additionally, the potential expansion of these methods to other search domains, including $W'$ production and differential cross-section measurements, is anticipated, promising new insights into the field of high-energy particle physics.

Conclusion

In conclusion, the BOOST2012 workshop has significantly contributed to understanding jet substructure in the context of the LHC's demanding experimental landscape. The developments discussed in the report are pivotal for future high-energy physics explorations, both in theory and practice. Continued advancements in predictive models and experimental techniques are expected to further bridge the gap between theoretical predictions and empirical data, enriching the field's capacity to detect new particles and phenomena beyond the Standard Model. As jet substructure methodologies mature, their applications will likely extend across various domains, paving the way for new discoveries in the high-energy frontier.