Comprehensive search for new phenomena in the dilepton spectrum at the LHC

Introduction

While the Standard Model of particle physics (SM) has proven tremendously successful, experimental evidence points to it not being a complete description of our universe, but a low energy approximation of a more complete theory. The searches for new phenomena (NP) are therefore an important component of the experimental program of the Large Hadron Collider (LHC).

Current Understanding

While there is no direct evidence for NP at the LHC, measurements of beauty hadron decays display a seemingly coherent pattern of deviations with respect to the SM predictions. These deviations suggest that NP couples differently to three generations of matter. The quark-level processes responsible for these so-called ‘flavor anomalies’ are related to dilepton production processes (Drell-Yan scattering) through the crossing symmetry.

Project Goals

The measurements of the kinematics of the high mass Drell-Yan (HMDY) process are therefore uniquely sensitive to a wide variety of NP explanations of the ‘anomalies’.

1. The goal of this ground-breaking project is to provide for the first time the complete set of the world’s most precise HMDY differential cross-section measurements.
2. These measurements will cover not only the light lepton channels ev/μv/ee/µµ, but also extremely challenging third generation τv and ττ, ditau (DITTO), final states.
3. These measurements will be used to probe NP at mass scales beyond the reach of direct production at the LHC through the SM effective field theory framework.

Methodology

The innovative performance and trigger improvements of the DITTO project will allow the ensemble of the proposed measurements to reach maximum precision. This will boost the possibility for a NP discovery within the data sets expected to be collected by the ATLAS experiment at the LHC.

Significance

Just as dilepton resonances, such as the J/ψ and Y mesons and the Z and W bosons were crucial for the establishment of the SM, the study of the same final state, to be undertaken in the DITTO project, will help to pave the way for a better understanding of the physics processes beyond it.