Sinan Sagir's Website
CMS strip tracker is an important part of the CMS detector. It is built at the innermost layer of the CMS detector, providing the tracks of particles originating from the proton-proton collisions and assigning vertex that is very important for physics analyses. Being very close to the interaction point, it is exposed to very high radiation. In order to make sure that CMS detector provides high quality data that is crucial for physics analyses, the tracker needs to be monitored. We perform simulations of different detector properties using the temperature and fluence history of the CMS strip tracker. These simulations are then compared to real measurements to determine the performance of the detector. We later use these simulations to estimate detector lifetime, improve annealing, and temperature settings so that the tracker will continue taking high quality data for a longer term. These simulations are also important for testing models that are developed from experimental studies and the results of our experimental studies on prototype silicon detectors are directly applicable in this project. For more information and some results, see the link
The Higgs boson discovered at the LHC by both ATLAS and CMS experiments has a mass of around 125 GeV, which is significantly smaller than new physics scales This causes the so called Hierarchy problem. There are different models that attempt to address this problem, one of which is the Composite Higgs Model that predicts a very heavy fermionic partner to top quark with a charge of 5/3 (often referred to as $X_{5/3}$). I led a searches for this particle where it is produced in pairs at center-of-mass energy of $\sqrt{s}=13$ TeV with the CMS detector in Run II. $X_{5/3}$ is expected to decay into a W boson and a top quark, which then decays into a bottom quark and a W boson. We analyze the events where one of the W bosons in the final state decays into a lepton and a neutrino and the rest of the three W’s decay hadronically. This was the first study of $X_{5/3}$ at the LHC using the semi-leptonic decay channel. The results were combined with the more sensitive same-sign dilepton channel nad published in JHEP.
After the discovery of the Higgs boson at the Large Hadron Collider (LHC) in 2012, the focus of interest now moved on to understanding the physics behind this particle, in particular whether it is the Higgs boson as predicted by the standard model (SM) or it has some theory beyond the SM. In order to find out if it is a Higgs boson or the Higgs boson, we need to characterize its full properties such as spin and parity. The studies showed that the new particle is a scalar particle with a spin of 0 as predicted by the SM. However, these results did not exclude very small anomalous couplings to other particles. In this work, we search for anomalous Higgs couplings to vector bosons in VH associated Higgs production channel with Higgs decaying to a pair of bottom quarks and vector boson decaying leptonically using the data collected with the Compact Muon Solenoid (CMS) detector at the LHC from proton-proton collisions in 2012 at center-of-mass energy of $\sqrt{s}=8$ TeV. We demonstrated that the VH channel is very powerful to put limits on very small anomalous Higgs couplings to vector bosons. This analysis was the first study of anomalous Higgs couplings at the LHC in VH associated Higgs production channel and the first study in Higgs fermionic decay channel. The resulting paper is published in PLB and can be found at this link
This project was a research into the development of radiation hard silicon sensors to be used in the CMS tracker during the high luminosity phase of the LHC (HL-LHC). Given the very high radiation environment with increased limunosity, it is very crucial to develop new sensor technologies that would be suitable in the presence of high radiation conditions during HL-LHC. We have built experimental setups at Brown University to perform tests on prototype silicon detectors and to investigate their radiation hardness. We have studied many prototype sensors on these experimental setups both before and after 800 MeV proton irradiations at LANSCE (Los Alamos National Lab). We have also extended our studies by performing an isothermal annealing study at different temperatures. The results of these studies helped understand more about the radiation damage dependency on particle type (protons, neutrons, muons) and/or different energies (23MeV and 23GeV).