Description:

Title: TBA

Speaker: Dr. Alexey Svyatkovskiy, Purdue University
 

Abstract:

The Compact Muon Solenoid (CMS) experiment is one of two major experiments at the Large Hadron Collider (LHC) at CERN which studies the physics of the Standard Model (SM) of particle physics and beyond. The new energy frontiers probed by the LHC and the large data samples collected made it possible for physicists to re-measure the parameters of SM with higher precision and to discover new physics. Currently, many precision measurements at the LHC are limited by the knowledge of the structure of the proton, which is described by so called parton distribution functions (PDFs). To overcome this limitation new PDFs based on LHC measurements are needed.

The precision measurements of electroweak interactions in a new energy regime and the application of these measurements to improve our understanding of the structure of the proton are presented in the talk. The results are based on proton-proton collision data at $\sqrt{s} = 7$ and 8\TeV recorded with the CMS detector at the LHC during the first years of operation. Measurements of the differential Drell--Yan cross section in the dimuon and dielectron channels covering the dilepton mass range of 15 to 2000\GeV and absolute dilepton rapidity from 0 to~2.4 are presented. In addition to the differential cross sections, the measurements of ratios of the normalized differential cross sections (double ratios) at $\sqrt{s} = 7$ and 8\TeV are performed in order to provide further constraints for PDFs, substantially reducing theoretical systematic uncertainties due to correlations.

The inclusion of DY data in PDF fits is shown to provide substantial constraints for the strange quark and the light sea quark distribution functions in a region of phase space which has not been accessible at hadron colliders in the past.