Probing electroweak Symmetry Breaking at LHC: Higgs Physics with the CMS detector

Deutsches Elektronen-Synchrotron DESY
Notkestraße 85
22607 Hamburg

Institut für Experimentelle Kernphysik
76128 Karlsruhe

Particle physics attempts to describe the universe in terms of fundamental matter constituents and interaction between them. The present knowledge of mankind about elementary particles and the basic principles, governing their interactions, is comprised in a field theory, called Standard Model (SM), describing the electromagnetic, the weak and the strong interaction. So far the SM is in excellent agreement with experimental measurements.

However, the corner stone of the theory, explaining where the mass of particles is coming from, is not yet established. Of course, we know that most of the fundamental particles have a mass. It is widely believed that the origin of mass is the electroweak symmetry breaking, realized in the SM by the Higgs mechanism. A scalar field is added to the fundamental fields of the SM, and particles acquire mass by the interaction with this field.

The Higgs mechanism gives rise to one fundamental scalar particle, the Higgs boson, which has been so far elusive for experimental detection. The Higgs boson would be the first fundamental scalar particle in the universe. If it exists, it will be discovered in the near future at the Large Hadron Collider (LHC) at CERN. The energy of the LHC will be sufficient to cover the full mass range where a Higgs boson is expected. The LHC will be also a powerful facility to probe the dynamics of the electroweak symmetry breaking. The predictions of the SM will be either confirmed or new physics phenomena will occur as predicted by extensions of the Standard Model. The Compact Muon Solenoid (CMS), one of the four particle experiments at the LHC, will record and analyze the data delivered by LHC.

The central research topic of the proposed Young Investigator Group will be the study of the Higgs mechanism of the electroweak symmetry breaking with the CMS detector. The group’s program will be carried out in close collaboration with the CMS groups of the Deutsches Elektronen Synchrotron (DESY) and the University of Karlsruhe, the theory groups at DESY and Karlsruhe and the Monte Carlo Helmholtz Alliance Group at DESY.

The research program comprises two stages. In the first stage the group will use early LHC data to perform detector calibration and optimization of analysis tools crucial for establishing the Higgs signal in a number of channels. In particular the detection of the bottom and the top quark, called Heavy Flavors, will be a key issue for Higgs boson studies. The group will hence join the Heavy Flavor Identification Group of the CMS collaboration to develop and tune heavy flavor tagging tools based on precise track reconstruction in the pixel and silicon strip detectors.

In the second stage the group will commence the analysis of the Higgs channels, relying upon identification of bottom jets. These channels include the associated production of the Higgs boson with top quark and bottom quark pairs. The results of these analyses will be used to determine the Higgs boson mass and measure couplings to the heaviest fermions − the top and bottom quarks.

In a longer perspective the group will join activities focusing on the detector R&D program for the upgraded LHC facility. The group will participate in the development of novel detector technologies, such as ultra-radiation hard Chemical Vapor Deposited (CVD) diamond sensors, for the application at CMS and also at detectors at a future linear electron-positron collider.

Leader of the Helmholtz Young Investigators Group:

Dr. Alexei Raspereza
Deutsches Elektronen-Synchrotron
Notkestr. 85
22607 Hamburg
Office: 66/009
Tel.: +49-40-8998-4850
Email :

Weiterführende Links
application/pdf Sachbericht 2009 (260KB)
application/pdf Sachbericht 2010 (311KB)
application/pdf Sachbericht 2011 (82KB)
application/pdf Sachbericht 2012 (14KB)
application/pdf Sachbericht 2013 (67KB)
application/pdf Schlussbericht 2014 (131KB)