Local Alignment of the BABAR Silicon Vertex Tracking Detector

The BABAR Silicon Vertex Tracker (SVT) is a five-layer double-sided silicon detector designed to provide precise measurements of the position and direction of primary tracks, and to fully reconstruct low-momentum tracks produced in e+e- collisions at the PEP-II asymmetric collider at Stanford Linear Accelerator Center. This paper describes the design, implementation, performance, and validation of the local alignment procedure used to determine the relative positions and orientations of the 340 SVT wafers. This procedure uses a tuned mix of in-situ experimental data and complementary lab-bench measurements to control systematic distortions. Wafer positions and orientations are determined by minimizing a chisquared computed using these data for each wafer individually, iterating to account for between-wafer correlations. A correction for aplanar distortions of the silicon wafers is measured and applied. The net effect of residual mis-alignments on relevant physical variables is evaluated in special control samples. The BABAR data-sample collected between November 1999 and April 2008 is used in the study of the SVT stability.Comment: 21 pages, 20 figures, 3 tables, submitted to Nucl. Instrum. Meth.

Testing CP and Time Reversal Symmetries with Λb→ΛV(1−)\Lambda_b \to \Lambda V(1-) Decays

In this letter, an overview is given for interesting tests of both CP and Time Reversal symmetries with the beauty baryon $\Lambda_b$. Extensive use of the helicity formalism and HQET is done for all calculations. Then, emphasis is put on sophisticated methods like analysis of resonance polarizations and particular angle distributions which can exhibit a clear signal of TR violation.Comment: 4 pages, 1 figure, 3 tables. Talk given at the 13th International QCD Conference 3-7th July 2006 Montpellier (France

Influence of Different Preparation Processes on the Mechanical Properties of Carbon Nanotube-Reinforced Copper Matrix Composites

Experiments on the uniform distribution of carbon nanotubes in the copper matrix using different ball milling methods were performed. The effect of different preparation processes for carbon nanotube (CNT)-reinforced copper matrix composites on their conductivity and mechanical properties was also analyzed. High-performance carbon nanotube-reinforced copper matrix composites containing 1 vol.% CNT by the best preparation process termed flake ball milling (FBM) possess good interface bonding strength not only with CNT evenly dispersed in the copper matrix but also with the CNT morphology and structure having the utmost integrity. Tensile strength increased by 30% with an elongation of 26% and electrical conductivity of 85% IACS as compared to a pure copper block prepared from the same FBM powders.Выполнены эксперименты по оценке равномерности распределения углеродных нанотрубок в медной матрице с использованием разных методов размола в шаровой мельнице. Проанализировано влияние различных методов изготовления композиционных материалов с медной матрицей, упрочненных углеродными нанотрубками, на их электропроводность и механические свойства. Высококачественные композиционные материалы (содержат 1 об.% углеродных нанотрубок), изготовляемые наиболее эффективным способом, получившим навание размол в шаровой мельнице для придания пластинчатой структуры , приобретают хорошую прочность сцепления на поверхности контакта не только при равномерном распределении углеродных нанотрубок в медной матрице, но и при максимальной целостности их морфологии и структуры. Предел прочности при растяжении возрастал на 30% при удлинении 26% и электропроводности 85% по стандарту IACS по сравнению с заготовкой из чистой меди, изготовленной из тех же пластинчатых порошков

Effect of cytokinins on shoot regeneration from cotyledon and leaf segment of stem mustard (Brassica juncea var. tsatsai)

Cotyledon and leaf segments of stem mustard (Brassica juncea var. tsatsai) were cultured on Murashige and Skoog medium supplemented with various concentrations of different cytokinins [6-benzyladenine (BA), N-(2-chloro-4-pyridyl)-n-phenylurea (CPPU), 6-furfurylaminopurine (KT) and thidiazuron (TDZ)] in combinations with different levels of ¿-naphthalene acetic acid (NAA). The shoot regeneration frequency of cotyledon and leaf segment was dependent on the kinds and concentrations of cytokinins used in the medium, while in most cases cotyledon gave high regeneration frequency than leaf segment. TDZ proved to be the best cytokinin to induce shoot from both cotyledon and leaf segments compared to BA, KT and CPPU. The highest frequency of shoot regeneration was 61.3¿67.9 % in cotyledon and 40.7¿52.4% in leaf segment respectively when 2.27 or 4.54 ¿M TDZ was combined with 5.37 ¿M NAA. Next to TDZ, CPPU was also very suitable to induce shoot formation both in cotyledon and leaf segment. When 1.61 ¿M CPPU was combined with 2.69 ¿M NAA, shoot regeneration frequency was 45.0% in cotyledon and 36.4% in leaf segment, respectively. It was also shown that KT and BA affected shoot regeneration from cotyledon and leaf segment, the shoot regeneration was greatly increased when NAA was added together with cytokinins. The efficient and reliable shoot regeneration system was developed in both cotyledon and leaf segments. This regeneration protocol may be applicable to the improvement of this crop by genetic engineering in the futur

Elastic and electronic properties of fluorite RuO₂ from first principle

The elastic, thermodynamic, and electronic properties of fluorite RuO₂ under high pressure are investigated by plane-wave pseudopotential density functional theory. The optimized lattice parameters, elastic constants, bulk modulus, and shear modulus are consistent with other theoretical values. The phase transition from modified fluorite-type to fluorite is 88 GPa (by localized density approximation, LDA) or 115.5 GPa (by generalized gradient approximation, GGA). The Young's modulus and Lamé's coefficients are also studied under high pressure. The structure turned out to be stable for the pressure up to 120 GPa by calculating elastic constants. In addition, the thermodynamic properties, including the Debye temperature, heat capacity, thermal expansion coefficient, Grüneisen parameter, and Poisson's ratio, are investigated. A small band gap is found in the electronic structure of fluorite RuO₂ and the bandwidth increases with the pressure. Also, the present mechanical and electronic properties demonstrate that the bonding nature is a combination of covalent, ionic, and metallic contributions.Пружнi, термодинамiчнi та електричнi властивостi флюориту RuO₂ при високому тиску дослiджуються за допомогою теорiї функцiоналу густини з плоскохвильовим псевдопотенцiалом. Оптимiзованi параметри гратки, пружнi сталi, об’ємний модуль i модуль зсуву узгоджуються з iншими теоретичними значеннями. Фазовий перехiд з модифiкованого флюориту до флюориту є при 88 GPa (наближення локальної густини, LDA), чи при 115.5 GPa (узагальнене градiєнтне наближення, GGA). Також дослiджено модуль Юнга i коефiцiєнти Ламе при високих тисках. Структура є стабiльною для тискiв до 120 GPa, якщо обчислювати пружнi сталi. Крiм того, дослiджено термодинамiчнi властивостi, включаючи температуру Дебая, теплоємнiсть, коефiцiєнт теплового розширення, параметр Грюнайзена i коефiцiєнт Пуассона. В електроннiй структурi флюориту RuO₂ знайдено малу зонну щiлину i ширина зони зростає iз тиском. Також, представленi механiчнi та електроннi властивостi демонструють, що природа зв’язування є комбiнацiєю ковалентного, iонного i металiчного вкладiв

Search for Invisible Decays of η\eta and η′\eta^\prime in J/ψ→ϕηJ/\psi \to \phi\eta and ϕη′\phi \eta^\prime

Using a data sample of $58\times 10^6$ $J/\psi$ decays collected with the BES II detector at the BEPC, searches for invisible decays of $\eta$ and $\eta^\prime$ in $J/\psi$ to $\phi\eta$ and $\phi\eta^\prime$ are performed. The $\phi$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag the $\eta$ and $\eta^\prime$ decays. No signals are found for the invisible decays of either $\eta$ or $\eta^\prime$, and upper limits at the 90% confidence level are determined to be $1.65 \times 10^{-3}$ for the ratio $\frac{B(\eta\to \text{invisible})}{B(\eta\to\gamma\gamma)}$ and $6.69\times 10^{-2}$ for $\frac{B(\eta^\prime\to \text{invisible})}{B(\eta^\prime\to\gamma\gamma)}$. These are the first searches for $\eta$ and $\eta^\prime$ decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo

Observation of Two New N* Peaks in J/psi -> ppi−nˉp pi^- \bar n and pˉπ+n\bar p\pi^+n Decays

The $\pi N$ system in decays of $J/\psi\to\bar NN\pi$ is limited to be isospin 1/2 by isospin conservation. This provides a big advantage in studying $N^*\to \pi N$ compared with $\pi N$ and $\gamma N$ experiments which mix isospin 1/2 and 3/2 for the $\pi N$ system. Using 58 million $J/\psi$ decays collected with the Beijing Electron Positron Collider, more than 100 thousand $J/\psi \to p \pi^- \bar n + c.c.$ events are obtained. Besides two well known $N^*$ peaks at 1500 MeV and 1670 MeV, there are two new, clear $N^*$ peaks in the $p\pi$ invariant mass spectrum around 1360 MeV and 2030 MeV. They are the first direct observation of the $N^*(1440)$ peak and a long-sought "missing" $N^*$ peak above 2 GeV in the $\pi N$ invariant mass spectrum. A simple Breit-Wigner fit gives the mass and width for the $N^*(1440)$ peak as $1358\pm 6 \pm 16$ MeV and $179\pm 26\pm 50$ MeV, and for the new $N^*$ peak above 2 GeV as $2068\pm 3^{+15}_{-40}$ MeV and $165\pm 14\pm 40$ MeV, respectively

Charm multiplicity and the branching ratios of inclusive charmless b quark decays in the general two-Higgs-doublet models

In the framework of general two-Higgs-doublet models, we calculate the branching ratios of various inclusive charmless b decays by using the low energy effective Hamiltonian including next-to-leading order QCD corrections, and examine the current status and the new physics effects on the determination of the charm multiplicity $n_c$ and semileptonic branching ratio $B_{SL}$. Within the considered parameter space, the enhancement to the ratio $BR(b \to s g)$ due to the charged-Higgs penguins can be as large as a factor of 8 (3) in the model III (II), while the ratio $BR(b \to no charm)$ can be increased from the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II). Consequently, the value of $B_{SL}$ and $n_c$ can be decreased simultaneously in the model III. The central value of $B_{SL}$ will be lowered slightly by about 0.003, but the ratio $n_c$ can be reduced significantly from the theoretical prediction of $n_c= 1.28 \pm 0.05$ in the SM to $n_c= 1.23 \pm 0.05$, $1.18 \pm 0.05$ for $m_{H^+}=200, 100$ GeV, respectively. We find that the predicted $n_c$ and the measured $n_c$ now agree within roughly one standard deviation after taking into account the effects of gluonic charged Higgs penguins in the model III with a relatively light charged Higgs boson.Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be published in Phys.Rev.

The Vacuum System of HIRFL

AbstractThe vacuum system of Heavy Ion Research Facility in Lanzhou (HIRFL) is a large and complex system. HIRFL consists of two ECR ion sources, a sector focus cyclotron (SFC), a separate sector cyclotron (SSC) and a multi-purpose cooling storage ring system which has a main ring (CSRm) and an experiment ring (CSRe). Several beam lines connect these accelerators together and transfer various heavy ion beams to more than 10 experiment terminals. According to the requirements of the ion acceleration and ion lifetime, the working pressure in each accelerator is different. SFC is nearly 50 years old. After upgrade, the working pressure in SFC is improved from 10-6mbar to 10-8mbar. The pressure in SSC which was built in the 1980s reaches the same level. The cooling storage ring system with a length of 500m came into operation in 2007. The average pressures in CSRm and CSRe are 5×10-12mbar and 8×10-12mbar respectively. Different designs were adopt for vacuum system of a dozen beam lines to meet specific requirement of each experiment terminal. Along with the extensive development of the heavy ion researches and applications, new accelerators of HIRFL are under construction. The vacuum system of the new machines will be designed and constructed followed the overall schedule

Measurements of the Mass and Full-Width of the ηc\eta_c Meson

In a sample of 58 million $J/\psi$ events collected with the BES II detector, the process J/$\psi\to\gamma\eta_c$ is observed in five different decay channels: $\gamma K^+K^-\pi^+\pi^-$, $\gamma\pi^+\pi^-\pi^+\pi^-$, $\gamma K^\pm K^0_S \pi^\mp$ (with $K^0_S\to\pi^+\pi^-$), $\gamma \phi\phi$ (with $\phi\to K^+K^-$) and $\gamma p\bar{p}$. From a combined fit of all five channels, we determine the mass and full-width of $\eta_c$ to be $m_{\eta_c}=2977.5\pm1.0 ({stat.})\pm1.2 ({syst.})$ MeV/$c^2$ and $\Gamma_{\eta_c} = 17.0\pm3.7 ({stat.})\pm7.4 ({syst.})$ MeV/$c^2$.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.