Study of Unparticle plus Lepton Signatures at CMS

This diploma thesis describes a study of the discovery and exclusion potential of unparticle signatures with the CMS experiment at the LHC at a center-of-mass energy of 10 TeV during early data taking. The reviewed channel contains the real production of a vector unparticle and an associated SM Z boson. As unparticles leave no trace in the detector, missing transverse energy is their dominant indication of existence. The SM Z boson has various decay channels, the muonic one is chosen herein. “Unparticle stuff will astonish us immediately”, H. Georgi states in his first unparticle paper in Spring 2007. More than 200 papers published so far containing “unparticle(s)” in the header do not beg to differ. Many new theories for physics beyond the SM involving more or less new particle states try to overcome certain shortcomings of the SM. They all have one thing in common, they are more particles. The concept of unparticles is different. It is just ONE new object, and it is NOT a particle. What constitutes a particle state? Of course the fact that it has a fixed mass eigenvalue. There is the electron rest mass, no other. Unparticles are different, occupying a continuous mass spectrum. This is the result of a new symmetry embedded in unparticle theory, extending the Poincaré group by the conformal group. Unparticle theory provides suitable solutions to some SM problems. But why bother about yet another theory? As the underlying truth is yet to be discovered – hopefully evidences will be collected at the LHC – all theories are equally possible. Theories like the more talked over supersymmetry are not more likely just because we have not seen an evidence of them for over 40 years. In this thesis, discovery and exclusion potentials are derived making use of the CLs method after separating signal events from SM events making use of a conventional cut- based analysis. The events have been simulated with the full detector simulation. It is possible to discover a real vector unparticle signature at a one-sided 5$\sigma$ CL in the muonic channel in 100 pb$^{−1}$ in a certain range of the unparticle parameter space. Adding the electronic decay channel of the Z boson increases the sensitivity and therefore the discovery range. If no signal is present, an exclusion for $\lambda_{u}$=2 TeV of vector unparticles for 1.01 < dU < 1.24 can be set at 95% CL, where dU is the scaling dimension and $\lambda_{u}$ is the renormalization scale of the unparticle sector.