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Search Results: 1 - 10 of 191398 matches for " D. Sillou "
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A new experiment to search for the invisible decay of the orthopositronium
A. Badertscher,P. Crivelli,W. Fetscher,S. N. Gninenko,J. P. Peigneux,A. Rubbia,D. Sillou
Physics , 2004,
Abstract: We propose an experiment to search for invisible decays of orthopositronium (o-Ps) with a 90% confidence sensitivity in the branching ratio as low as $10^{-8}$. Evidence for this decay mode would unambigously signal new physics: either the existence of extra--dimensions or fractionally charged particles or new light gauge bosons. The experimental approach and the detector components of the proposed experiment are described.
An Improved Limit on Invisible Decays of Positronium
A. Badertscher,P. Crivelli,W. Fetscher,U. Gendotti,S. Gninenko,V. Postoev,A. Rubbia,V. Samoylenko,D. Sillou
Physics , 2006, DOI: 10.1103/PhysRevD.75.032004
Abstract: The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be a strong evid ence for new physics beyond the Standard Model (SM): for example the existence of extra--dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles. Mirror matter could be a relevant dark matter candidate. In this paper the setup and the results of a new experiment are presented. In a collected sample of about $(6.31\pm0.28) \times 10^6$ orthopositronium decay s, no evidence for invisible decays in an energy window [0,80] keV was found and an upper limit on the branching ratio of orthopositronium \invdecay could be set: $\binvdecay<4.2\times 10^{-7}$ (90% C.L.) Our results provide a limit on the photon mirror-photon mixing strength $\epsilon \leq 1.55\times 10^{-7}$ (90% C.L.) and rule out particles lighter than the electron mass with a fraction $Q_x \leq 3.4 \times 10^{-5}$ of the electron charge. Furthermore, upper limits on the branching ratios for the decay of parapositronium $Br(p-Ps\to invisible)\leq 4.3 \times 10^{-7}$ (90% C.L.) and the direct annihilation $Br(e^+e^-\to invisible)\leq 2.1 \times 10^{-8}$ (90% C.L.) could be set.
PWO crystals for CMS electromagnetic calorimeter : studies of the radiation damage kinetics
G. Drobychev,E. Auffray,V. Dormenev,M. Korzhik,P. Lecoq,A. Lopatic,P. Nédélec,J. P. Peigneux,D. Sillou
Physics , 2005,
Abstract: Kinetics of radiation damage of the PWO crystals under irradiation and recovery were studied. Crystals were irradiated with dose corresponding to average one expected in the electromagnetic calorimeter (working dose irradiation). Radiation damage and recovery were monitored through measurements of PWO optical transmission. An approach is proposed which allows evaluating the influence of the PWO crystals properties on the statistical term in the energy resolution of the electromagnetic calorimeter. The analysis also gives important information about the nature of the radiation damage mechanism in scintillation crystals. The method was used during development of technology of the mass production of radiation hard crystals and during development of methods for crystals certification
Search for an exotic three-body decay of orthopositronium
A. Badertscher,P. Crivelli,M. Felcini,S. N. Gninenko,N. A. Goloubev,P. Nedelec,J. P. Peigneux,V. Postoev,A. Rubbia,D. Sillou
Physics , 2002, DOI: 10.1016/S0370-2693(02)02237-2
Abstract: We report on a direct search for a three-body decay of the orthopositronium into a photon and two penetrating particles, o-Ps -> gamma + X1 + X2. The existence of this decay could explain the discrepancy between the measured and the predicted values of the orthopositronium decay rate. From the analysis of the collected data a single candidate event is found, consistent with the expected background. This allows to set an upper limit on the branching ratio < 4.4 \times 10^{-5} (at the 90% confidence level), for the photon energy in the range from 40 keV < E_gamma< 400 keV and for mass values in the kinematical range 0 < mX1+mX2 <900 keV. This result unambiguously excludes the o-Ps -> gamma + X1 + X2 decay mode as the origin of the discrepancy.
Development of a high-efficiency pulsed slow positron beam for measurements with orthopositronium in vacuum
N. Alberola,T. Anthonioz,A. Badertscher,C. Bas,A. S. Belov,P. Crivelli,S. N. Gninenko,N. A. Golubev,M. M. Kirsanov,A. Rubbia,D. Sillou
Physics , 2005, DOI: 10.1016/j.nima.2006.01.025
Abstract: We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum. The new pulsing scheme is based on a double-gap coaxial buncher powered by an RF pulse of appropriate shape. The modulation of the positron velocity in the two gaps is used to adjust their time-of-flight to a target. This pulsing scheme allows to minimize non-linear aberrations in the bunching process and to efficiently compress positron pulses with an initial pulse duration ranging from 300 to 50 ns into bunches of 2.3 to 0.4 ns width, respectively, with a repetition period of 1 mks. The compression ratio achieved is ~100, which is a factor 5 better than has been previously obtained with slow positron beams based on a single buncher. Requirements on the degree, to which the moderated positrons should be mono-energetic and on the precision of the waveform generation are presented. Possible applications of the new pulsed positron beam for measurements of thin films are discussed.
An apparatus to search for mirror dark matter via the invisible decay of orthopositronium in vacuum
A. Badertscher,A. Belov,P. Crivelli,M. Felcini,W. Fetscher,S. N. Gninenko,N. A. Golubev,M. M. Kirsanov,L. L. Kurchaninov,J. P. Peigneux,A. Rubbia,D. Sillou
Physics , 2003, DOI: 10.1142/S0217751X04020105
Abstract: Mirror matter is a possible dark matter candidate. It is predicted to exist if parity is an unbroken symmetry of the vacuum. The existence of the mirror matter, which in addition to gravity is coupled to our world through photon-mirror photon mixing, would result in orthopositronium (o-Ps) to mirror orthopositronium (o-Ps') oscillations. The experimental signature of this effect is the invisible decay of o-Ps in vacuum. This paper describes the design of the new experiment for a search for the o-Ps -> invisible decay in vacuum with a sensitivity in the branching ratio of Br(o-Ps -> invisible)\simeq 10^{-7}, which is an order of magnitude better than the present limit on this decay mode from the Big Bang Nucleosynthesis. The experiment is based on a high-efficiency pulsed slow positron beam, which is also applicable for other experiments with o-Ps, and (with some modifications) for applied studies. Details of the experimental design and of a new pulsing method, as well as preliminary results on requirements for the pulsed beam components are presented. The effects of o-Ps collisions with the cavity walls as well as the influence of external fields on the o-Ps to o-Ps' oscillation probability are also discussed.
Formation Of A Cold Antihydrogen Beam in AEGIS For Gravity Measurements
G. Testera,A. S. Belov,G. Bonomi,I. Boscolo,N. Brambilla,R. S. Brusa,V. M. Byakov,L. Cabaret,C. Canali,C. Carraro,F. Castelli,S. Cialdi,M. de Combarieu,D. Comparat,G. Consolati,N. Djourelov,M. Doser,G. Drobychev,A. Dupasquier,D. Fabris,R. Ferragut,G. Ferrari,A. Fischer,A. Fontana,P. Forget,L. Formaro,M. Lunardon,A. Gervasini,M. G. Giammarchi,S. N. Gninenko,G. Gribakin,R. Heyne,S. D. Hogan,A. Kellerbauer,D. Krasnicky,V. Lagomarsino,G. Manuzio,S. Mariazzi,V. A. Matveev,F. Merkt,S. Moretto,C. Morhard,G. Nebbia,P. Nedelec,M. K. Oberthaler,P. Pari,V. Petracek,M. Prevedelli,I. Y. Al-Qaradawi,F. Quasso,O. Rohne,S. Pesente,A. Rotondi,S. Stapnes,D. Sillou,S. V. Stepanov,H. H. Stroke,G. Tino,A. Vairo,G. Viesti,H. Walters,U. Warring,S. Zavatarelli,A. Zenoni,D. S. Zvezhinskij,for the AEGIS Proto-Collaboration
Physics , 2008, DOI: 10.1063/1.2977857
Abstract: The formation of the antihydrogen beam in the AEGIS experiment through the use of inhomogeneous electric fields is discussed and simulation results including the geometry of the apparatus and realistic hypothesis about the antihydrogen initial conditions are shown. The resulting velocity distribution matches the requirements of the gravity experiment. In particular it is shown that the inhomogeneous electric fields provide radial cooling of the beam during the acceleration.
Electrical Conductivity of Collapsed Multilayer Graphene Tubes  [PDF]
D. Mendoza
World Journal of Nano Science and Engineering (WJNSE) , 2012, DOI: 10.4236/wjnse.2012.22009
Abstract: Synthesis of multilayer graphene on copper wires by a chemical vapor deposition method is reported. After copper etching, the multilayer tube collapses forming stripes of graphitic films, their electrical conductance as a function of temperature indicate a semiconductor-like behavior. Using the multilayer graphene stripes, a cross junction is built and owing to its electrical behavior we propose that a tunneling process exists in the device.
Porous Carbon Grown by Chemical Vapor Deposition on Copper Substrates  [PDF]
D. Mendoza
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.38003
Abstract: Amorphous porous carbon was synthesized by chemical vapor deposition on copper substrates. The average size of the pores is around 1.2 microns with some small pores decorating the big ones. Lamellar samples of this carbonaceous material can be separated from the copper support and may be useful as electrode due to its low electrical resistivity of the order of 0.4 Ωcm.
Application of Enzyme Extracted from Aloe vera Plant in Chemical Pretreatment of Cotton Knitted Textile to Reduce Pollution Load  [PDF]
D. Jothi
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33B007

Nowadays, highly alkaline chemicals like caustic soda, soda ash, silicate, acetic acid and soaping agents are used for scouring to remove the non-cellulosic impurities from the cotton. Using 30 - 40 gm/Kg on weight of the fabric results in destruction of cotton structure. Intensive rinsing and more acid is needed for reutilization of cotton, which enlarges the volume of effluent. Furthermore, these hazards chemicals result in increase in COD, BOD and TDS in waste water. These chemicals also attack the cellulose leading to heavy strength loss and weight loss in the fabric. The net result is low quality control and polluted environment with high usage of energy, time, chemical and water. Aloe vera presents the finest commercial opportunity in various industrial sectors among the various plants. Also, most of the countries are gifted with the unique geographical features that are essential for cultivation of Aloe vera. Yet, none of the country has realized and reaped the full potential of such plants in various industrial applications. The reason is simple: lack of the requisite expertise in extraction of various enzymes present in aloe plant. Fortunately, the technology is now accessible to make use of enzyme in textile application. In this research an attempt has been made to make use of lipase enzyme extracted from aloe plant in textile chemical pre- treatment process. In the present research work, an attempt was made to develop bio scouring of 100% cotton knitted fabric with lipase enzyme extracted from Aloe deberena plant at various concentration (1%, 2% and 3%) at various temperature (40?C, 60?C and 70?C) for a period of 30 minutes, 60 minutes and 90 minutes. The properties of bio scoured fabrics are compared with these of conventional scoured one. Encouraging results in terms of dye uptake, dye levelness, wash fastness, light fastness and rubbing fastness are obtained in case of bio scouring fabric dyed with dark reactive colors. Further, it reduces volume of effluent as well as COD, TDS and pH. It saves a substantial thermal energy 50% and electrical energy 40%. Bio scouring waste water has 40% - 50% less COD and 60% less TDS as compared to conventional scouring waste water.

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