The monitoring system for the aerogel Cherenkov counter of the BELLE detector

We report on a design and performances of a monitoring system developed for the aerogel Cherenkov counters (ACC) of the BELLE detector. The system consists of blue LEDs, a diffuser box, and optical distributors which distribute the LED light to the ACC modules. The employed LED (NSPB series) has been observed to have high reliability on the long term stability and the temprature dependence. The diffuser box is employed to reduce the intrinsic non-uniformity of the LED light intensity. The overall performances of the present monitoring system on uniformity and intensity of the light output have been found to satisfy all the requirements for the monitoring.Comment: 24 pages, LaTeX, 13 eps figures, to be published in Nucl. Instrum. and Meth. A. Postscript file (4.5 MB) is available at http://www-hep.phys.saga-u.ac.jp/~murakami/paper/xxx_accmon.p

Electron Identification in Belle

We report on electron identification methods and their performance in the Belle experiment at the KEK-B asymmetric B-Factory $e^{+} e^{-}$ storage ring. Electrons are selected using a likelihood approach that takes information from the electromagnetic calorimeter, the central drift chamber, and the silica aerogel Cherenkov counters as input. We achieve an electron identification efficiency of $(92.4 \pm 0.4)$ with a $\pi^{\pm}$ fake rate of $(0.25 \pm 0.02)$ for the momentum range between 1.0 GeV/$c$ and 3.0 GeV/$c$ in laboratory frame.Comment: 20 page

Geomagnetically Conjugate Relationship of Polar Geomagnetic Disturbances -Particularly the Distinct Geomagnetic Conjugacy between Syowa Station in Antarctica and Reykjavik in Iceland

In Chapter I, the average pattern of the ionospheric current system of polar geomagnetic storms for the northern and southern polar regions is constructed by analyzing exactly simultaneous events during the IGY period. Those events are classified into two groups; i.e., severe storms where K_P=7.4 and moderate storms where K_p=4.3. In both cases, the average D_p fields for northern and southern polar regions are almost exactly symmetric with each other with respect to the geomagnetic coordinates, suggesting that the geomagnetic linkage holds well between the two polar regions. Several remarks are made on the mechanism of causation of the D_p field. It is emphasized that the D_p field may comprise two components, namely, SP-component which is characterized by enhancement of the S_q^p field by the stronger solar wind in storm time, and defined AEJ-component which has been known as the auroral electrojet concentrating along the narrow region of the auroral zone. In Chapter II, similarity and simultaneity of geomagnetic bay type variations in geomagnetically conjugate areas in the northern and southern polar regions are discussed, based upon simultaneous data of individual bays. From the observed facts, it has been concluded that charged particles of nearly the same flux are precipitating simultaneously in the northern and southern polar ionospheres over the conjugate areas. Besides, it seems likely that nearly the same intensity of electric field is transferred to the both polar regions simultaneously from the magnetosphere. The conjugacy always holds well between the conjugate stations located in the auroral zone and the polar cap at the best-developed stage of geomagnetic bays. Some theoretical discussions are attempted on the structure of instantaneous and individual D_p field of geomagnetic bays. In Chapter III, the conjugacy of storm sudden commencement (SSC) between conjugate points in the auroral zone is described based upon the simultaneous data observed at Syowa Station and Reykjavik. Similarity and simultaneity are good at the conjugate points for SSCs. Observed SSCs are elliptically polarized and the sense of rotation of polarization is counterclockwise and clockwise on the morning and afternoon sides respectively as viewed along the magnetic lines of force in both conjugate points. Comparing the characteristics of polarization and other morphological facts revealed by the present analysis with those of the S_q^p field, it is concluded that the polar part of SSC is attributable to the transfer of excess electric charge to the polar ionosphere from the outer magnetosphere, which is caused by fluctuation and enhancement of the S_q^p field of a pre-SSC stage by the impact of storm time solar wind to the magnetosphere. The propagation of SSC seems to take the form of hydromagnetic wave propagation. In Chapter IV, the conjugacy of sudden impulses (SI) between the conjugate stations in the auroral zone is described, using the simultaneous data obtained at Syowa Station and Reykjavik. Comparison of morphological characteristics of sudden impulse with those of storm sudden commencement indicates that SI and SSC are quite similar and sudden impulse may be caused by the same mechanism as that for SSC. In Chapter V, the conjugacy of geomagnetic pulsations of several minutes in period (pc-5) between conjugate points in the auroral zone is discussed. Pc-5 pulsations have extremely good conjugate relations in regard to their time of occurrence and their wave forms. The polarization of the observed pc-5 is elliptic and the plane of polarization is approximately perpendicular to the geomagnetic lines of force. The sense of rotation of polarization vector is counterclockwise in the morning and clockwise in the afternoon as viewed along the magnetic lines of force. Therefore, pc-5 pulsation may be attributable to low frequency hydromagnetic wave generated in the outer magnetosphere and transmitted along the lines of force to both polar

Semiconductor-enriched single wall carbon nanotube networks applied to field effect transistors

Substantial progress on field effect transistors "FETs" consisting of semiconducting single wall carbon nanotubes "s-SWNTs" without detectable traces of metallic nanotubes and impurities is reported. Nearly perfect removal of metallic nanotubes is confirmed by optical absorption, Raman measurements, and electrical measurements. This outstanding result was made possible in particular by ultracentrifugation (150 000 g) of solutions prepared from SWNT powders using polyfluorene as an extracting agent in toluene. Such s-SWNTs processable solutions were applied to realize FET, embodying randomly or preferentially oriented nanotube networks prepared by spin coating or dielectrophoresis. Devices exhibit stable p-type semiconductor behavior in air with very promising characteristics. The on-off current ratio is 10^5, the on-current level is around 10 $\mu$A, and the estimated hole mobility is larger than 2 cm2 / V s

A novel type of proximity focusing RICH counter with multiple refractive index aerogel radiator

A proximity focusing ring imaging Cherenkov detector, with the radiator consisting of two or more aerogel layers of different refractive indices, has been tested in 1-4 GeV/c pion beams at KEK. Essentially, a multiple refractive index aerogel radiator allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation in single photon angular resolution associated with the increased uncertainty of the emission point. With the refractive index of consecutive layers suitably increasing in the downstream direction, one may achieve overlapping of the Cherenkov rings from a single charged particle. In the opposite case of decreasing refractive index, one may obtain well separated rings. In the former combination an approximately 40% increase in photon yield is accompanied with just a minor degradation in single photon angular resolution. The impact of this improvement on the pion/kaon separation at the upgraded Belle detector is discussed.Comment: submitted to Nucl. Instr. Meth.

Monte-Carlo Simulation for an Aerogel Cherenkov Counter

We have developed a Monte-Carlo simulation code for an aerogel \v Cerenkov Counter which is operated under a strong magnetic field such as 1.5T. This code consists of two parts: photon transportation inside aerogel tiles, and one-dimensional amplification in a fine-mesh photomultiplier tube. It simulates the output photoelectron yields as accurately as 5% with only a single free parameter. This code is applied to simulations for a B-Factory particle-identification system.Comment: 40 pages, latex(article), 19 figure

Fat transforms ascorbic acid from inhibiting to promoting acid-catalysed N-nitrosation

<b>Background</b>: The major potential site of acid nitrosation is the proximal stomach, an anatomical site prone to a rising incidence of metaplasia and adenocarcinoma. Nitrite, a pre-carcinogen present in saliva, can be converted to nitrosating species and N-nitroso compounds by acidification at low gastric pH in the presence of thiocyanate. <b>Aims</b>: To assess the effect of lipid and ascorbic acid on the nitrosative chemistry under conditions simulating the human proximal stomach. <b>Methods</b>: The nitrosative chemistry was modelled in vitro by measuring the nitrosation of four secondary amines under conditions simulating the proximal stomach. The N-nitrosamines formed were measured by gas chromatography–ion-trap tandem mass spectrometry, while nitric oxide and oxygen levels were measured amperometrically. <b>Results</b>: In absence of lipid, nitrosative stress was inhibited by ascorbic acid through conversion of nitrosating species to nitric oxide. Addition of ascorbic acid reduced the amount of N-nitrosodimethylamine formed by fivefold, N-nitrosomorpholine by .1000-fold, and totally prevented the formation of N-nitrosodiethylamine and N-nitrosopiperidine. In contrast, when 10% lipid was present, ascorbic acid increased the amount of Nnitrosodimethylamine, N-nitrosodiethylamine and N-nitrosopiperidine formed by approximately 8-, 60- and 140-fold, respectively, compared with absence of ascorbic acid. <b>Conclusion</b>: The presence of lipid converts ascorbic acid from inhibiting to promoting acid nitrosation. This may be explained by nitric oxide, formed by ascorbic acid in the aqueous phase, being able to regenerate nitrosating species by reacting with oxygen in the lipid phase