Study On Nanoparticles Of ZnSe Synthesized By Chemical Method And Their Characterization

The properties of semiconductor nanoparticles depend mainly on their shape and size due to high surface-to-volume ratio. The II – VI semiconductors have many applications such as, LED, acousto-optical effects and biological sensors. The ZnSe nanoparticles have wide-ranging applications in laser, optical instruments etc. because it has wide band gap and transmittance range, high luminescence efficiency, low absorption coefficient. In recent years, much attention was paid on the preparation methods, performances and applications of ZnSe nanoparticles and thin solid films, and a lot of important accomplishments have been obtained. In the present study ZnSe nanoparticles were successfully prepared by reacting Zn(CH3COO)2·2H2O and Na2SeSO3 at 343 K. The size of the crystallite was estimated by X-ray diffraction and TEM, whereas EDAX has confirmed of no foreign impurity inclusion in ZnSe nanoparticles. XRD shows the crystallite size of 5.68 nm and TEM gives a distribution ranging from 20 nm to 71 nm. A SEM image shows that the particles are spherical in a shape. Quantum confinement has resulted in the blue shift compared to bulk ZnSe as observed from the absorption spectra of particles dispersed in DMF. We obtained the photoluminescence spectra on these particles with two different excitation wavelength which shows broad band emission peak at 573 nm. Photoluminescence spectra taken with other excitation wavelength also gives sharp emission peaks at 484 nm, 530 nm, 551 nm and 600 nm. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/967

Studies on ZnO Nanorods Synthesized by Hydrothermal Method and their Characterization

ZnO nanorods, with a wide band gap of 3.37 eV have been attracting much attention due to its wide range of applications. Looking to this aspect in the present paper, ZnO nanorods were synthesized by hydrothermal method at 120 C for 2 hrs in an autoclave by using zinc acetate and sodium hydroxide as the starting materials. The final product obtained was then characterized by Energy Dispersive analysis of X-rays (EDAX), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Raman Spectroscopy. X-ray diffraction and Raman spectra showed that ZnO nanorods are belonging to wurtzite structure without any impurity phases. The ZnO nanorods shows polycrystalline behaviour as observed from SAED pattern and the calculated lattice parameters from this pattern which matches with the XRD results.The optical properties of the ZnO nanorods were then further studied with the help of absorption, photoluminescence (PL) and FTIR spectra. The optical energy band gap determined from the absorption spectra comes about 3.33 eV. In the photoluminescence spectra of ZnO nanorods the UV emission appears at 380 nm and strong blue emission appears at 445 nm. FTIR spectra indicate the existence of distinct characteristic absorption peak at 520 cm – 1 for ZnO stretching modes. The potential toxicity of nanosized ZnO nanorods were investigated using Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Serratia marceseus and Proteus vulgaris bacteria as test organism. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3560

Higgs-Boson Production Induced by Bottom Quarks

Bottom quark-induced processes are responsible for a large fraction of the LHC discovery potential, in particular for supersymmetric Higgs bosons. Recently, the discrepancy between exclusive and inclusive Higgs boson production rates has been linked to the choice of an appropriate bottom factorization scale. We investigate the process kinematics at hadron colliders and show that it leads to a considerable decrease in the bottom factorization scale. This effect is the missing piece needed to understand the corresponding higher order results. Our results hold generally for charged and for neutral Higgs boson production at the LHC as well as at the Tevatron. The situation is different for single top quark production, where we find no sizeable suppression of the factorization scale. Turning the argument around, we can specify how large the collinear logarithms are, which can be resummed using the bottom parton picture.Comment: 18 page

B→η(η′)K(π)B \to \eta(\eta') K(\pi) in the Standard Model with Flavor Symmetry

The observed branching ratios for $B\to K \eta'$ decays are much larger than factorization predictions in the Standard Model (SM). Many proposals have been made to reconcile the data and theoretical predictions. In this paper we study these decays within the SM using flavor U(3) symmetry. If small annihilation amplitudes are neglected, one needs 11 hadronic parameters to describe $B\to PP$ decays where $P$ can be one of the $\pi$, $K$, $\eta$ and $\eta'$ nonet mesons. We find that existing data are consistent with SM with flavor U(3) symmetry. We also predict several measurable branching ratios and CP asymmetries for $B \to K (\pi) \eta(\eta')$, $\eta(\eta')\eta(\eta')$ decays. Near future experiments can provide important tests for the Standard Model with flavor U(3) symmetry.Comment: 13 pages, 4 table

Electroweak Corrections to the Charged Higgs Boson Decay into Chargino and Neutralino

The electroweak corrections to the partial widths of the $H^+ \to \tilde{\chi}^+_i \tilde{\chi}_j^0 (i=1,j=1,2)$ decays including one-loop diagrams of the third generation quarks and squarks, are investigated within the Supersymmetric Standard Model. The relative corrections can reach the values about 10%, therefore they should be taken into account for the precise experimental measurement at future colliders.Comment: 21 pages, 6 eps figures, 1 Latex fil

Charged Higgs Boson Production in Bottom-Gluon Fusion

We compute the complete next-to-leading order SUSY-QCD corrections for the associated production of a charged Higgs boson with a top quark via bottom-gluon fusion. We investigate the applicability of the bottom parton description in detail. The higher order corrections can be split into real and virtual corrections for a general two Higgs doublet model and into additional massive supersymmetric loop contributions. We find that the perturbative behavior is well under control. The supersymmetric contributions consist of the universal bottom Yukawa coupling corrections and non-factorizable diagrams. Over most of the relevant supersymmetric parameter space the Yukawa coupling corrections are sizeable, while the remaining supersymmetric loop contributions are negligible.Comment: 18 pages, v2: some discussions added, v3: published versio

Measurement of Bottom versus Charm as a Function of Transverse Momentum with Electron-Hadron Correlations in p+p Collisions at sqrt(s)=200 GeV

The momentum distribution of electrons from semi-leptonic decays of charm and bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative quantum chromodynamics (pQCD) calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is \sigma_{b\b^bar}= 3.2 ^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.Comment: 432 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Proximity effect at superconducting Sn-Bi2Se3 interface

We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions down to 250 mK and in different magnetic fields. A number of conductance anomalies were observed below the superconducting transition temperature of Sn, including a small gap different from that of Sn, and a zero-bias conductance peak growing up at lower temperatures. We discussed the possible origins of the smaller gap and the zero-bias conductance peak. These phenomena support that a proximity-effect-induced chiral superconducting phase is formed at the interface between the superconducting Sn and the strong spin-orbit coupling material Bi2Se3.Comment: 7 pages, 8 figure

Heavy Quarks and Heavy Quarkonia as Tests of Thermalization

We present here a brief summary of new results on heavy quarks and heavy quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma Thermalization" Workshop in Vienna, Austria in August 2005, directly following the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop (Vienna August 2005) Proceeding

Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV

PHENIX has measured the centrality dependence of charged hadron p_T spectra from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction of the contribution from hard scattering to high p_T hadron production. For central collisions the yield at high p_T is shown to be suppressed compared to binary nucleon-nucleon collision scaling of p+p data. This suppression is monotonically increasing with centrality, but most of the change occurs below 30% centrality, i.e. for collisions with less than about 140 participating nucleons. The observed p_T and centrality dependence is consistent with the particle production predicted by models including hard scattering and subsequent energy loss of the scattered partons in the dense matter created in the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to Phys. Lett. B. Revised to address referee concerns. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm