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Turning noise into data: a discovery strategy for new weakly-interacting physics

Lay summary

L'objectif principal de ce projet est de rechercher et, espérons-le, de découvrir une nouvelle particule cachée dans les collisions du LHC à basse énergie, abondamment produites. Cela se fera en implémentant d'abord une nouvelle technique d'analyse des données capable d'extraire des informations utiles des collisions à faible énergie, puis élaborant trois stratégies de recherche distinctes et sensibles à différents types de nouvelles particules. Si l'une de ces recherches aboutit à la découverte d'une nouvelle particule, elle pourrait expliquer l'origine de la matière noire, la raison pour laquelle la force gravitationnelle est si faible par rapport aux autres forces fondamentales, ou, autrement, fournir des réponses à d'autres grandes questions ouvertes de la physique moderne.

Abstract

With the discovery of the Higgs boson in 2012 by the ATLAS and CMS Collaborations, the Standard Model (SM) of particle physics is now complete, and it forms a robust definition of the strong, weak, and electromagnetic interactions with matter. Nonetheless, it is clear that the SM is an incomplete description of the universe: there are multiple observed phenomena such as the existence of Dark Matter (DM) which are not explained by the SM. The experimental High Energy Physics (HEP) collaborations at the Large Hadron Collider (LHC) are hard at work looking for clues that would provide explanations for these phenomena, and possibly point towards an ultimate theory of particle physics.The LHC delivers so many proton-proton collisions to ATLAS and CMS that it is not possible to record them all. The collaborations must quickly sort through the incoming information and save only what they deem to be important; the ATLAS strategy prioritizes higher-energy or otherwise rare collisions.This choice works well for many applications, and it was fundamental to the discovery of the Higgs boson. However, it also discards the vast majority of the data of interest in searches for low-energy weakly-interacting new physics, thus limiting the sensitivity to new low-mass particles which could explain the nature of DM or other low-energy phenomena.This project proposes a solution: it is possible to recover an enormous yet currently unused low-energy dataset by turning the additional “noise” collisions recorded in every event into useful data. This novel approach, hereafter referred to as the Data Interpretation Strategy for COmplete Vertex Event Reconstruction in High Energy Physics (DISCOVERHEP), provides a means of searching for new weakly-interacting physics at a level that dramatically exceeds traditional approaches. I propose to build a team which will develop and make use of this new dataset in the search for new weakly-interacting physics. I will focus on hadronic physics (interactions with quarks and gluons), as this has traditionally been challenging to study at low energy and thus remains a mostly-unexplored area with a large discovery-potential.The proposed project is divided into four Work Packages (WPs). WP1 focuses on the development of the tools needed to reconstruct every event in the ATLAS dataset with respect to every vertex in the event, thus providing the enormous low-energy proton-proton collision dataset needed to conduct searches for new physics. WP2 represents the first analysis of this unique dataset using a traditional dijet resonance search, which is expected to provide dramatically improved sensitivity to new low-energy weakly-interacting physics models (including dark matter mediators) compared to competing approaches. WP3 exploits jet substructure techniques in this new dataset to identify low-energy jets inconsistent with Standard Model quarks and gluons, thus probing currently uncovered areas of parameter space in the search for more complex new physics models such as strongly-coupled dark sectors. WP4 exploits modern machine learning techniques and this novel dataset to generically search for anomalous low-energy hadronic interactions, thus probing a wide variety of different models of new physics, and which may point the way towards unexpected new forms of physics that would be missed using traditional directed search strategies.There are many well-motivated models of new low-energy weakly-interacting hadronic physics, and it is thus important to cover a wide range of possible options. The proposed research program does exactly this through both direct searches for specific well-motivated models of new physics and a generic search to minimize the impact of preconceptions on the forms that new physics may take. The proposal will furthermore probe low-energy weakly-interacting hadronic physics to unprecedented precision, thus expanding the ATLAS physics program and potentially leading the way towards new discoveries.

  Prof.Steven Randolph Schramm