Standard Model CP violation in B->X_d \ell^+\ell^- decays

We investigate the CP violating asymmetry, the forward backward asymmetry and the CP violating asymmetry in the forward-backward asymmetry for the inclusive B->X_d \ell^+\ell^- decays for the \ell=e,\mu \tau channels in the standard model. It is observed that these asymmetries are quite sizable and B->X_d \ell^+\ell^- decays seem promising for investigating CP violation.Comment: 13 pages, 6 figure

Amorf silisyum/p-tipi kristal silisyum heteroeklem güneş gözelerinin saçtırma ve PECVD tekniği ile üretilmesi.

Silicon heterojunction solar cells, a-Si:H/c-Si, are promising technology for future photovoltaic systems. An a-Si:H/c-Si heterojunction solar cell combines the advantages of single crystalline silicon photovoltaic with thin-film technologies. This thesis reports a detailed survey of heterojunction silicon solar cells with p-type wafer fabricated by magnetron sputtering and Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques at low processing temperature. In the first part of this study, magnetron sputtering method was employed to fabricate a-Si:H thin films and then a-Si:H/c-Si solar cells. Amorphous silicon (a-Si:H) films were grown on glass in order to perform electrical and optical characterizations. The J-V characteristics of the silicon heterojunction solar cells were analyzed as a function of a-Si:H properties. It was shown that a-Si thin films with well-behaved chemical and electronic properties could be fabricated by the magnetron sputtering. Hydrogenation of the grown film could be achieved by H2 introduction into the chamber during the sputtering. In spite of the good film properties, fabricated solar cells had poor photovoltaic parameters with a low rectification characteristic. This low device performance was caused by high resistivity and low doping concentration in the sputtered film. The second part of the thesis is dedicated to heterojunction solar cells fabricated by PECVD. In this part a systematic study of various PECVD processing parameters were carried out to optimize the a-Si:H(n) emitter properties for the a-Si:H(n)/c-Si(p) solar cell applications. In the next stage, a thin optimized a-Si:H(i) buffer layer was included on the emitter side and on the rear side of the c-Si(p) to improve the surface passivation. Insertion of an a-Si:H(i) buffer layer yielded higher high open circuit voltage (Voc) with lower fill factor. It was shown that high Voc is due to the efficient surface passivation by the front/rear intrinsic layer which was also confirmed by the measurement of high effective lifetime for photo-generated carriers. Low fill factor on the other hand is caused by increasing resistivity of the solar cells by inserting low conductivity a-Si:H(i) layers.Ph.D. - Doctoral Progra

İnklusif b-mezon bozunumlarındaki cp bozulmasının standart model analizi.

Being a flavor changing neutral current process, inclusive semileptonic B- meson decays provide reliable testing grounds for the Standard Model at the loop level. They are also importanat in the CKM phenomology and investing the CP violation due to the existence of sizable interference terms in the decay amplitude. In this work , the rare inclusive semileptonic B- meson decays for (lepton is electron ,muon , tau) are investigated in the context of the Standard Model.The differential branching ratio, forward-backward asymmetry ,CP 6violating asymmetry and CP 6 violating asymmetry in the forward-backward asymmetry in these processes are examined.The dependencies of these physical parameters on the Standard Model parametres are analyzed by paying a special attention to the long distance effects. Although the branching ratios predicted for the inclusive semileptonic B- meson decays are relatively small because of CKM suppression , it has been found that there is a significant ACP and ACP(AFB) for these processes.M.S. - Master of Scienc

Influence of Sn Doping on Cds Thin Film Grown by Ultrasonic Spray Pyrolysis

Sn doped CdS thin films were grown onto glass substrates through Ultrasonic Spray Pyrolysis technique. The effect of the Sn dopant on the optical and structural properties of CdS films was investigated. Undoped and doped CdS films presented a hexagonal structure. The band gap of each film was calculated as 2.43 eV by using transmission spectra. The electrical analysis proved the improvement in resistance by increasing Sn dopant atoms in CdS lattice. All the CdS:Sn films were evaluated as a potential window material for heterojunction solar cells

Effect of Au on the crystallization of germanium thin films by electron-beam evaporation

Metal induced crystallization is a widely used method to form crystalline/polycrystalline structures at low temperatures. In this work, Au was applied to enhance the crystallization of amorphous Ge films. Ge films with thicknesses of similar to 1.5 mu m were fabricated by electron beam evaporation on c-Si substrate with and without very thin Au layer. Crystallization properties of Ge films were analyzed for different growth and post annealing temperatures varied between 270 degrees C and 730 degrees C. The structures of polycrystalline Ge films were investigated by employing X-ray diffraction (XRD), Raman spectra and scanning electron microscopy (SEM)