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Release : 2007
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Book Synopsis Search for Randall-Sundrum Gravitons in Dilepton and Diphoton Final States with 1 Fb-1 of Data by :

Download or read book Search for Randall-Sundrum Gravitons in Dilepton and Diphoton Final States with 1 Fb-1 of Data written by . This book was released on 2007. Available in PDF, EPUB and Kindle. Book excerpt: The work presented in this thesis is the search for Randall-Sundrum (RS) gravitons from an analysis of approximately 1 fb−1 data collected with the D0 detector at Fermilab. The standard model has been a great success in explaining all experimental observations in particle physics. However, we also know that it has fundamental problems. One of these problems, called the hierarchy problem, is related to the large difference between the electroweak scale and the Planck scale. The model proposed by Randall and Sundrum presents a possible solution to the hierarchy problem by introducing physics beyond the standard model. Randall and Sundrum's theory postulates the existence of a 4th spatial dimension in addition to the conventional (3+1)-dimensional space. Gravity is localized on a 3+1 dimensional subspace, called a brane (Planck brane) that is separated in this new 4th spatial dimension from the standard model brane. As one moves away from this Planck brane, gravity is exponentially suppressed and this explains why gravity appears so weak at the standard model brane. In the simplest RS model, the only particles that propagate in the extra dimension are gravitons. The graviton manifests itself on the standard model brane as a series of excited states that couple to standard model particles with similar strength as the electroweak interaction. The ground state is the massless graviton and the order of magnitude of the mass of the lowest excited state is expected to be one TeV. The first excited mode of the graviton might be produced resonantly at the Tevatron. Gravitons can decay into fermion-antifermion or diboson pairs. Here I search for gravitons through their decay to ee− and [gamma][gamma] final states. These final states have similar signatures in our detector and can thus be treated together. After analyzing the data I do not find any excess over standard model expectations and set an upper limit on the production rate of such gravitons. I compare this limit to the production rate predicted by the theory for a range of possible couplings and set mass limits on the lowest excited gravitons state of up to 898 GeV.