#### Event Title

Analysis of the Collins-Soper Angle in Contact Interaction and Large Extra Dimension Monte Carlo Data Samples

#### Advisor(s)

Dr. Peter Dong, Illinois Mathematics and Science Academy

#### Location

Room A149

#### Start Date

26-4-2019 10:45 AM

#### End Date

26-4-2019 11:00 AM

#### Abstract

Abstract: The Collins-Soper angle θ* is the angle between the negatively-signed lepton and the Z axis in the center of mass reference frame, calculated using Lorentz-invariant kinematic variables. In CI analyses, cosθ* is used to control the lepton angular distributions (as 1 + cosθ), as well as determine forward-backward asymmetry of the dileptons in the sample. The cosθ distribution of a sample is a crater-shaped distribution ranging from -1 to +1, with an asymmetrical shift towards +1 caused by the transverse momentum asymmetries between interacting partons.

However, the Collins-Soper calculations can give rise to significant sources of error. One such error of particular importance is the Same-Sign Electron problem. Due to systematic error inherent to event reconstruction, the measured sign of about 5-10% of electrons and positrons is flipped, leading to positrons being labelled as electrons and vice versa. The Collins-Soper Angle calculation is dependent upon proper particle identification, and as such a method for labelling the particles in case of a sign flip is needed. This study aims to determine whether there are significant differences between random assignment, high Pt trusting, low Pt trusting, and other variable-dependent methods by comparing generator-level distributions with the various models of reconstructed distributions. If there are significant differences between methods, the study will determine which method yields the most accurate results.

Analysis of the Collins-Soper Angle in Contact Interaction and Large Extra Dimension Monte Carlo Data Samples

Room A149

Abstract: The Collins-Soper angle θ* is the angle between the negatively-signed lepton and the Z axis in the center of mass reference frame, calculated using Lorentz-invariant kinematic variables. In CI analyses, cosθ* is used to control the lepton angular distributions (as 1 + cosθ), as well as determine forward-backward asymmetry of the dileptons in the sample. The cosθ distribution of a sample is a crater-shaped distribution ranging from -1 to +1, with an asymmetrical shift towards +1 caused by the transverse momentum asymmetries between interacting partons.

However, the Collins-Soper calculations can give rise to significant sources of error. One such error of particular importance is the Same-Sign Electron problem. Due to systematic error inherent to event reconstruction, the measured sign of about 5-10% of electrons and positrons is flipped, leading to positrons being labelled as electrons and vice versa. The Collins-Soper Angle calculation is dependent upon proper particle identification, and as such a method for labelling the particles in case of a sign flip is needed. This study aims to determine whether there are significant differences between random assignment, high Pt trusting, low Pt trusting, and other variable-dependent methods by comparing generator-level distributions with the various models of reconstructed distributions. If there are significant differences between methods, the study will determine which method yields the most accurate results.