3,302 research outputs found
Next-to-Leading Order NMSSM Decays with CP-odd Higgs Bosons and Stops
We compute the full next-to-leading order supersymmetric (SUSY) electroweak
(EW) and SUSY-QCD corrections to the decays of CP-odd NMSSM Higgs bosons into
stop pairs. In our numerical analysis we also present the decay of the heavier
stop into the lighter stop and an NMSSM CP-odd Higgs boson. Both the EW and the
SUSY-QCD corrections are found to be significant and have to be taken into
account for a proper prediction of the decay widths.Comment: 28 pages, 10 figure
Dynamic response of a flexible space beam
Dynamic response of a candidate flexible beam for a space experiment on control of flexible structures is investigated. Studies of natural frequencies reveal a beam length in which torsion and bending frequencies virtually coincide. Eccentric tip mass causes small shifts in natural frequencies but introduces coupled torsional/bending mode shapes. Transient response studies indicate significant effects on tip responses of low damping and first bending mode excitation at higher frequencies. Steady state response suggest displacement and acceleration measurements could be made up to 5 to 12 Hz for the actuator forces/torques assumed
Physics at CERN's Antiproton Decelerator
The Antiproton Decelerator of CERN began operation in 1999 to serve
experiments for studies of CPT invariance by precision laser and microwave
spectroscopy of antihydrogen () and antiprotonic helium
(). The first 12 years of operation saw cold
synthesized by overlapping clouds of positrons () and antiprotons
() confined in magnetic Penning traps. Cold was also
produced in collisions between Rydberg positronium atoms and .
Ground-state was later trapped for up to s in a
magnetic bottle trap, and microwave transitions excited between its hyperfine
levels. In the atom, UV transitions were measured to a
precision of (2.3-5) by sub-Doppler two-photon laser
spectroscopy. From this the antiproton-to-electron mass ratio was determined as
1836.1526736(23), which agrees with the p value. Microwave
spectroscopy of yielded a measurement of the
magnetic moment with a precision of 0.3%. More recently the magnetic moment of
a single confined in a Penning trap was measured with a higher
precision, as in nuclear
magnetons. Other measurements include the energy loss of 1-100 keV
traversing conductor and insulator targets; the cross sections of <10 keV
ionizing gas targets; and the cross sections of 5-MeV
annihilating on target foils via nuclear collisions. The biological
effectiveness of beams destroying cancer cells was measured as a
possible method for radiological therapy. New experiments under preparation
attempt to measure the gravitational acceleration of or
synthesize \obar{\rm H}^+.Comment: To be published in Progress in Particle and Nuclear Physic
Laser cooling of new atomic and molecular species with ultrafast pulses
We propose a new laser cooling method for atomic species whose level
structure makes traditional laser cooling difficult. For instance, laser
cooling of hydrogen requires single-frequency vacuum-ultraviolet light, while
multielectron atoms need single-frequency light at many widely separated
frequencies. These restrictions can be eased by laser cooling on two-photon
transitions with ultrafast pulse trains. Laser cooling of hydrogen,
antihydrogen, and many other species appears feasible, and extension of the
technique to molecules may be possible.Comment: revision of quant-ph/0306099, submitted to PR
Organostibonsäureester. II [1]: Darstellung und Eigenschaften von Methanstibonsäureestern. Struktur von Di-μ-methoxy-bis[dibromo-methoxy-methyl-antimon(V)]
Dimere alkoxyverbrückte Verbindungen des Typs [CHSbX(OR)(μ-OR)] (X = Cl, Br; R = CH, CH) können durch Oxidation von CHSb(OR) mit Br oder S0Cl in CHCl unterhalb -60°C als lichtempfindliche kristalline Feststoffe erhalten werden. Die Struktur der Verbindung [CHSbBr(OCH)(μ-OCH)] konnte mittels Röntgenstrukturanalyse bestimmt werden. Umsetzungen mit Natriumalkoholaten in den entsprechenden Alkoholen bei 0°C führen zu dimeren Tetraalkoxymethylstiboranen. Austauschreaktionen von Tetramethoxymethylstiboran mit Ethanol ergeben das Ethoxyderivat und mit Diolen symmetrische spirocyclische Methanstibonsäureester.Dimeric alkoxy-bridged compounds of the type [CHSbX(OR)(μ-OR)] (X = Cl, Br; R = CH, CH) are prepared by oxidation of CHSb(OR) with Br or S0Cl in CHCl below -60°C as light sensitive erystals. The structure of [CHSbBr(OCH)(μ-OCH)] was determined by X-Ray analysis. By reaction with sodium alkoxides in the corresponding alcohol at 0°C dimeric tetraalkoxymethylstiboranes are obtained. Exchange reactions of tetramethoxymethylstiborane with ethanol give the ethoxy derivative and with diols symmetrie spirocyclic esters of methanestibonic acid
Vanishing Fe 3d orbital moments in single-crystalline magnetite
We show detailed magnetic absorption spectroscopy results of an in situ
cleaved high quality single crystal of magnetite. In addition the experimental
setup was carefully optimized to reduce drift, self absorption, and offset
phenomena as far as possible. In strong contradiction to recently published
data, our observed orbital moments are nearly vanishing and the spin moments
are quite close to the integer values proposed by theory. This very important
issue supports the half metallic full spin polarized picture of magnetite.Comment: 7 pages, 4 figure
Rydberg excitation of a single trapped ion
We demonstrate excitation of a single trapped cold Ca ion to
Rydberg levels by laser radiation in the vacuum-ultraviolet at 122 nm
wavelength. Observed resonances are identified as 3dD to 51 F, 52 F
and 3dD to 64F. We model the lineshape and our results imply a
large state-dependent coupling to the trapping potential. Rydberg ions are of
great interest for future applications in quantum computing and simulation, in
which large dipolar interactions are combined with the superb experimental
control offered by Paul traps.Comment: 4 pages, 3 figure
Continuous Lyman-alpha generation by four-wave mixing in mercury for laser-cooling of antihydrogen
Cooling antihydrogen atoms is important for future experiments both to test
the fundamental CPT symmetry by high-resolution laser spectroscopy and also to
measure the gravitational acceleration of antimatter. Laser-cooling of
antihydrogen can be done on the strong 1S-2P transition at the wavelength of
Lyman-alpha (121.6nm). A continuous-wave laser at the Lyman-alpha wavelength
based on solid-state fundamental lasers is described. By using a two-photon and
a near one photon resonance a scan across the whole phasematching curve of the
four-wave mixing process is possible. Furthermore the influence of the beam
profile of one fundamental beam on the four-wave mixing process is studied.Comment: 4 pages, 4 figure
Greenhouse gas production in degrading ice-rich permafrost deposits in northeastern Siberia
Permafrost deposits have been a sink for atmospheric carbon for millennia. Thaw-erosional processes, however, can lead to rapid degradation of ice-rich permafrost and the release of substantial amounts of organic carbon (OC). The amount of the OC stored in these deposits and their potential to be microbially decomposed to the greenhouse gases carbon dioxide (CO2) and methane (CH4) depends on climatic and environmental conditions during deposition and the decomposition history before incorporation into the permafrost. Here, we examine potential greenhouse gas production in degrading ice-rich permafrost deposits from three locations in the northeast Siberian Laptev Sea region. The deposits span a period of about 55 kyr from the last glacial period and Holocene interglacial. Samples from all three locations were incubated under aerobic and anaerobic conditions for 134 days at 4 °C. Greenhouse gas production was generally higher in deposits from glacial periods, where 0.2–6.1% of the initially available OC was decomposed to CO2. In contrast, only 0.1–4.0% of initial OC were decomposed in permafrost deposits from the Holocene and the late glacial transition. Within the deposits from the Kargin interstadial period (Marine Isotope Stage 3), local depositional environments, especially soil moisture, also affected the preservation of OC. Sediments deposited under wet conditions contained more labile OC and thus produced more greenhouse gases than sediments deposited under drier conditions. To assess the greenhouse gas production potentials over longer periods, deposits from two locations were incubated for a total of 785 days. However, more than 50% of total CO2 production over 785 days occurred within the first 134 days under aerobic conditions while even 80% were produced over the same period under anaerobic conditions, which emphasizes the non-linearity of the OC decomposition processes. Methanogenesis was generally observed in active layer samples but only sporadically in permafrost samples and was several orders of magnitude smaller than CO2 production
Calculation of electrostatic fields using quasi-Green's functions: application to the hybrid Penning trap.
Penning traps offer unique possibilities for storing, manipulating and investigating charged particles with high sensitivity and accuracy. The widespread applications of Penning traps in physics and chemistry comprise e.g. mass spectrometry, laser spectroscopy, measurements of electronic and nuclear magnetic moments, chemical sample analysis and reaction studies. We have developed a method, based on the Green's function approach, which allows for the analytical calculation of the electrostatic properties of a Penning trap with arbitrary electrodes. The ansatz features an extension of Dirichlet's problem to nontrivial geometries and leads to an analytical solution of the Laplace equation. As an example we discuss the toroidal hybrid Penning trap designed for our planned measurements of the magnetic moment of the (anti)proton. As in the case of cylindrical Penning traps, it is possible to optimize the properties of the electric trapping fields, which is mandatory for high-precision experiments with single charged particles. Of particular interest are the anharmonicity compensation, orthogonality and optimum adjustment of frequency shifts by the continuous SternGerlach effect in a quantum jump spectrometer. The mathematical formalism developed goes beyond the mere design of novel Penning traps and has potential applications in other fields of physics and engineering
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