Physics at the LHC with CMS

Vanderbilt University, Nashville TN

Investigators

Abstract

One of the major intellectual achievements of the 20th century was the development of the Standard Model (SM) of particle physics. This model succeeded in classifying all of the elementary particles known at the time into a hierarchy of groups having similar quantum properties. The validity of this model to date was recently confirmed by the discovery of the Higgs boson at the Large Hadron Collider at CERN. However, the Standard Model as it currently exists leaves open many questions about the universe, including such fundamental questions as to why the Higgs mass has the value it has. The Large Hadron Collider (LHC) is the premier Energy Frontier particle accelerator operating at the CERN laboratory near Geneva Switzerland. It is currently one of the foremost facilities for answering these Beyond the Standard Model questions and studying the properties of the Higgs boson. One of the primary functions of the Compact Muon Solenoid (CMS) experiment at the LHC is to discover new physics beyond the Standard Model. The work proposed here will analyze data from the CMS experiment looking for signals of Beyond the Standard Model (BSM) physics. This award will fund two aspects of the CMS experiment: 1) further searches for BSM physics and 2) help build the CMS Phase I forward pixel detector (FPix) upgrade, which will enhance the ability of CMS to discover BSM physics. BSM theoretical predictions include several different new particles in the so-called Super Symmetric (SUSY) theory. These new particles are candidates for Dark Matter. This award will fund searches for SUSY via the decays to multiple leptons (electrons or muons) and jets (the experimental signature of quarks). The SUSY particle decays in these channels also include a SUSY particle that goes right through the detector without interacting, thus the event has missing energy. Many SUSY models have been ruled out by the analysis of LHC data from 2010-2013. With the new higher energy running at LHC starting summer 2015, new analysis techniques will be applied in order to separate out SUSY (or other Dark Matter candidates) signals from large backgrounds. This involves the Vector Boson Fusion (VBF) mode of production where the quark-quark collision produces a pair of vector bosons (either W or Z) which then interact (Fuse) to form new particles. The experimental signature of this VBF production is a pair of energetic jets in the forward direction in opposite hemispheres of the detector, with large di-jet mass. These jets stand out above background from SM particle decays and thus enhance the signal to background ratio in the possible discovery of BSM particles. The award also provides important parts of the FPix upgrade which are being tested at FermiLab. The CMS Forward pixel upgrade will allow the precise vertex location, needed for all physics studies, even in the harsh environment (very high luminosity) expected in near future LHC running. The CMS Forward Pixel Detector uses state-of-the art silicon technology for particle detection combined with equally sophisticated readout electronics. Innovative techniques of radiation hard technology and bump bonding have been used in the current detector to meet the real estate challenges in a high radiation environment. These techniques would greatly enhance the life span of detectors used in outer space research and improve bio-sensing miniature devices for medical applications.