Sharif Digital Repository

We search for supersymmetry in the same-sign dilepton final state in the first 35 pb1 of data collected by the CMS detector and find no evidence of new physics at this point. Since true same-sign physics backgrounds, such asWWjj, are negligible for this amount of integrated luminosity, we focus our attention on data-driven estimations of the backgrounds where one (W+jets and tt backgrounds) or both of the leptons (QCD background) are fake. We use the generalized fake ratio method documented to estimate the rates for these fake backgrounds. Another source of backgrounds in the case of electrons is the charge-flip, where the charge of one of the electrons in an opposite-sign di-electron pair... 

Among the proposals for new physics, Supersymmetry is the most popular to gradually appear at a yet unreached center-of-mass energy at the Large Hadron Collider (LHC). However, that doesn’t seem very likely. This thesis represents a search for any evidence of a minimal supergravity inspired scenario (mSUGRA) of R-parity conserving supersymmetry at the Compact Muon Solenoid (CMS) experiment. The analysis employs an event topology , which consists primarily of opposite-sign di-leptons accompanied by hadronic jets and missing transverse energy. The search utilizes data produced by the proton-proton collision of the LHC at a center-of-mass energy p s = 7 TeV and recorded by the CMS detector in... 

We revisit the damped string equation on a compact interval with a variety of boundary conditions and derive an infinite sequence of trace formulas associated with it, employing methods familiar from super symmetric quantum mechanics. We also derive completeness and Riesz basis results for the associated root functions under less smoothness assumptions on the coefficients than usual, using operator theoretic methods only.After discussion about there topices, we need to know little about the functional analysis and partial differential equations. chapter one satisfied this aim.
 

In chapter one, I introduce large hadron colider and it's detectors CMS and ATLAS. Then I reviewe the structure of CMS such as tracker,ECAL,HCAL and Muon chamber.
In chapter two and three standard model (SM) and supersymmetry (SUSY) were introduced as a beneficial theory of particle physics. Spontaneous symmetry breaking was applied on MSSM lagrangians (Minimal Supersymmetric Standard Model) and all supersymmetric particles gain masses.
In the last chapter I explain MT2 variable and it’s application in jets recognition. After applying all cuts I use MT2 analysis and compare distribution of all channels (QCD,Wjets,Zjets,Top) with real data. At last i use ABCD method for estimating... 

In this thesis, a general survey and reviewis done about the models that go beyond the standard model. Even it contains the great subjects like quantum gravity and alternative Quantum field theories. In addition to them, we concentrate on the supersymmetry that is one of the most important subjects in the beyond the standard model. Recently, the validityof supersymmetry has confronted a lot of controversy. This motivates reconsideration of many supersymmetric models. So we survey the main motivations and problems of the supersymmetry and finally we discuss some possible solutions to the problems  

In this thesis a brief review of the concept of vacuum has been studied. In addition, we shall see how we can determine the vacuum energy in a flat space-time. Also the renormalization and the regularization of zero point energy, which is 122 order of magnitude more than the critical density energy, has been represented. Then, we study supersymmetry which is a candidate to solve this problem. Furthermore, different ways to determine cosmological constant and the orbits of planets has been studied.Finally, by studying free fall experiments, the gravitational properties of vacuum has been represented.Caisimir effect, one of the most amazing predictions in the history of physics, and Lamb... 

The concept of symmetry has long been the focus of numerous debates in different fields; some have come up with an artistic approach looking for a beautiful notion germane to the concept of symmetry. Others have examined this issue from a philosophical viewpoint and studied the ontology of symmetry and philosophers like Kant moved beyond the limits and have given their symmetry a transcendental position. On the other hand, in an anti-realist position relying on the fact that the goal of science is not truth but merely it’s an empirical adequacy, Van Fraassen argued that “science was rapidly gaining autonomy not only from theology but from all of philosophy, and was exploiting concepts and... 

During years, supersymmetry has been a candidate for resolution of Higgs mass fine-tuning problem that is quadratic dependence of scalar mass radiative correction to UV-physics. So, supersymmetry phenomenology is of great importance. As accelerators have reached energy of 13 TeV in recent years and sparticles have not yet been observed, it is important to have a theory in hand, describing SUSY breaking dynamics with scale of SUSY breaking above the energies currently accessible to accelerators. As a result of mass-sum-rule constraint which holds in theories with spontaneous SUSY breaking at tree level and leads to light sparticles and even tachyonic directions, there are currently no...