Andrei Gritsan |
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Project on CMS Tracker Alignment
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This project is supported in part by the U.S. National Science Foundation
(grants 0644849, 0758083, 1100862) and Alfred P. Sloan Foundation.
"Spin & alignment" group members at JHU
Tracker Alignment Project DescriptionModern silicon tracking detectors typically have a large number of measuring sensors, and statistical methods can be used to align individual sensors with respect to each other. For CMS there are more than 15,000 sensors which need to be aligned. The goal of the alignment procedure is to obtain six parameters for each independent sensor, these being the three spacial and three rotational parameters. Since 2005 we developed new analysis and modeling techniques and initiated improved procedures for the CMS pixel detector optical survey measurements at FNAL. We developed statistical methods for the alignment of thousands of silicon sensors using the chisq from survey together with tracks and demonstrating their performance within the CMS software framework. Since 2007 we are working on alignment of the first components of the CMS silicon tracker with cosmic tracks. In 2008-2009, the PI was a convener of the CMS tracker alignment group. In 2010-2011 Alessio Bonato is a convener. Understanding the alignment of thousands of silicon sensors, which track particle paths, is necessary to a micron precision and becomes the decisive factor in discovering of new particles.
Results presented at: The 2009 Europhysics Conference on High Energy Physics in Krakow (July 2009) [ slides] [ agenda] 3rd LHC alignment workshop in Geneva (June 2009) [ slides] [ agenda] 2nd LHC alignment workshop in Geneva (June 2007) [ slides] [ agenda] 1st LHC alignment workshop in Geneva (September 2006) [ proceedings in CERN-2007-004] Resonance Analysis Project DescriptionThe group has developed the tools to disentangle complicated angular structures in a broad range of models. This allows analysis of the spin, parity, and fundamental couplings of new particles which may be observed at the LHC, such as signatures of Higgs field, extra dimensions, or new gauge bosons. These studies start with analysis of the known Z boson to two leptons and measure its fundamental couplings to matter by measuring the weak-mixing angle, the only unknown parameter in the standard model which determines the relative couplings. These techniques have direct application to analysis of new potential resonances decaying to two fermions. We have also developed techniques for the search for more complicated di-boson decays of a Higgs or an exotic particle, such as H->ZZ, with subsequent decay to two leptons and two quark jets. This final state is complemented by the golden mode of four leptons in the final state, and our angular analysis provides powerful discrimination tool either against background or among different hypotheses of new physics. The program is designed to extract maximum information possible with the available LHC data, which also provides the tightest possible limit on any model to be excluded, including the limits on the Higgs boson.
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