Finding physics signals with shower deconstruction (1102.3480v2)

Abstract: We introduce shower deconstruction, a method to look for new physics in a hadronic environment. The method aims to be a full information approach using small jets. It assigns to each event a number chi that is an estimate of the ratio of the probability for a signal process to produce that event to the probability for a background process to produce that event. The analytic functions we derive to calculate these probabilities mimic what full event generators like Pythia or Herwig do and can be depicted in a diagrammatic way. As an example, we apply this method to a boosted Higgs boson produced in association with a Z-boson and show that this method can be useful to discriminate this signal from the Z+jets background.

Analysis of Physics Signal Detection Using Shower Deconstruction

The paper "Finding physics signals with shower deconstruction" by Davison E. Soper and Michael Spannowsky introduces the method of shower deconstruction, aimed at identifying new physics signals in a hadronic environment, such as those encountered at the Large Hadron Collider (LHC). This method focuses on isolating the decay products of new heavy particles from the predominant QCD background by leveraging small jets or microjets, derived from standard jet algorithms with reduced effective cone size.

Methodology

Shower deconstruction is designed as a comprehensive information approach, assigning a quantitative value, $\chi$, to each event. This value approximates the probability ratio of a signal process producing the event compared to a background process. The authors work within a framework that parallels conventional event generators like {\sc Pythia} or {\sc Herwig}, allowing for an analytical calculation of these probabilities. Specifically, protoparticle histories constructed from microjets are examined to disentangle the substructure formed by possibly new heavy particles amidst complex backgrounds.

In the mathematical formulation of shower deconstruction, the probability $P(\{p,t\}_N|S)$ of an observed microjet configuration $\{p,t\}_N$, given a signal hypothesis, is contrasted against the corresponding background probability $P(\{p,t\}_N|B)$. The method enables systematic evaluation through an extensive indexing of potential shower histories, with probabilities derived based on virtuality-ordered processes, color flow assignments, and successive emission probabilities. These elements were simplified to facilitate analytic computation while maintaining a degree of physical realism necessary for practical application in high energy experiments.

Application and Results

The paper exemplifies the utility of shower deconstruction through the specific case of Higgs boson production associated with a $Z$-boson, analyzing events where the Higgs undergoes a boosted decay into $b\bar{b}$ pairs. The model focuses on contrasting these events against a $Z$+jets background, highlighting the methodology's potential to refine the signal from the overwhelming standard model background. Significantly, the authors demonstrate a markedly improved signal-to-background separation when employing shower deconstruction, as opposed to previous event tagging approaches.

Through detailed simulations using both {\sc Pythia} and {\sc Herwig} generated datasets, the analysis showed consistently strong performance in enhancing discrimination power, thanks largely to its inherent adaptability to varying microjet patterns characteristic of signal and background events.

Implications and Future Work

Shower deconstruction presents a notable advancement towards efficient signal identification amidst hadronic processes at colliders. By systematically assessing particle distributions at the sub-jet level, it provides a versatile tool capable of discerning intricate patterns that would otherwise be obscured in coarse-grained analyses. This potential stands to have substantial implications for probing beyond-standard model physics, offering a refined approach for experiments targeting signatures of supersymmetric particles and alternative Higgs boson production mechanisms.

The paper sets forth a foundation upon which future advancements can build, potentially incorporating more nuanced modeling of non-perturbative effects and systematic uncertainties prevalent in collider data. An immediate trajectory for future research could involve integration with larger datasets and incorporation into live collider experiments, assessing robustness across numerous experimental conditions and processes beyond the specific cases addressed.

In conclusion, Soper and Spannowsky's work opens avenues for deepening our understanding of signal extraction techniques through shower deconstruction, marking a significant step in collider physics and offering an enduring contribution to experimental methodologies in the field.