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31.
M. Daum L. Dubal G.H. Eaton R. Frosch J. McCulloch R.C. Minehart E. Steiner C. Amsler R. Hausammann 《Physics letters. [Part B]》1976,60(4):380-384
We have measured the muon momentum in pion decay at rest using a magnetic spectrometer. From the result, pμ+ = (29.787±0.005) MeV/c, we deduce a squared muon neutrino mass of (0.23±0.54) MeV2/c4. 相似文献
32.
Diyabalanage T Amsler CD McClintock JB Baker BJ 《Journal of the American Chemical Society》2006,128(17):5630-5631
Palmerolide A, a 20-membered macrocyclic polyketide bearing carbamate and vinyl amide functionality, was isolated from the tunicate Synoicum adareanum collected from the vicinity of Palmer Station on the Antarctic Peninsula. Palmerolide A displays potent and selective cytotoxicity toward melanoma (UACC-66 LC50 = 0.018 muM) and appears to operate via inhibition (IC50 = 2 nM) of V-ATPase. 相似文献
33.
Amoretti M Amsler C Bonomi G Bouchta A Bowe PD Carraro C Cesar CL Charlton M Doser M Filippini V Fontana A Fujiwara MC Funakoshi R Genova P Hangst JS Hayano RS Jørgensen LV Lagomarsino V Landua R Lindelöf D Rizzini EL Macrí M Madsen N Manuzio G Montagna P Pruys H Regenfus C Rotondi A Testera G Variola A van der Werf DP;ATHENA Collaboration 《Physical review letters》2003,91(5):055001
Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends critically on parameters such as the plasma density and temperature. We discuss nondestructive measurements, based on a novel, real-time analysis of excited, low-order plasma modes, that provide comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The plasma length, radius, density, and total particle number are obtained. Measurement and control of plasma temperature variations, and the application to antihydrogen production experiments are discussed. 相似文献
34.
P. Weidenauer K. D. Duch M. Heel H. Kalinowsky F. Kayser E. Klempt B. May J. Reifenröther O. Schreiber M. Ziegler D. Bailey S. Barlag J. M. Butler U. Gastaldi R. Landua C. Sabev W. Dahme F. Feld-Dahme U. Schaefer W. R. Wodrich J. C. Bizot B. Delcourt J. Jeanjean H. Nguyen E. G. Auld D. A. Axen K. L. Erdman B. Howard R. Howard B. L. White S. Ahmad M. Comyn G. M. Marshall G. Beer L. P. Robertson M. Botlo C. Laa H. Vonach C. Amsler M. Doser J. Riedlberger U. Straumann P. Truöl ASTERIX Collaboration 《Zeitschrift fur Physik C Particles and Fields》1990,47(3):353-365
We have measured the branching ratios for \(\bar pp\) annihilation at rest intoπ + π ? η andπ + π ? η′ in hydrogen gas in two data samples that have different fractions ofS-wave andP-wave initial states. The branching ratios are derived from a comparison with the topological branching ratio for \(\bar pp\) annihilations into four charged pions of (49±4)% and the branching ratio intoπ + π ? π + π ? π 0 of (18.7±1.6)%. We find a significant reduction of the branching ratios fromP-states for \(\bar pp \to \pi ^ + \pi ^ - \eta \) andπ + π ? η′ in comparison toS-state annihilation. $$\begin{gathered} BR(S - wave \to \pi ^ + \pi ^ - \eta ) = (13.7 \pm 1.46) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta ) = (3.35 \pm 0.84) \cdot 10^{ - 3} \hfill \\ BR(S - wave \to \pi ^ + \pi ^ - \eta ') = (3.46 \pm 0.67) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta ') = (0.61 \pm 0.33) \cdot 10^{ - 3} . \hfill \\ \end{gathered} $$ In a partial wave analysis of theπ + π ? η Dalitz plot we find the following contributions: Phase space, \(a_2^ + (1320)\pi ^ \mp \) ,ηρ0 andf 2(1270)η: $$\begin{gathered} BR(S - wave \to \pi ^ + \pi ^ - \eta PS) = (6.31 \pm 1.22) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta PS) = (0.47 \pm 0.26) \cdot 10^{ - 3} \hfill \\ BR(^1 S_0 \to a_2^ \pm (1320)\pi ^ \mp ) = (2.59 \pm 0.73) \cdot 10^{ - 3} \hfill \\ BR(^3 S_1 \to a_2^ \pm (1320)\pi ^ \mp ) = (1.31 \pm 0.48) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to a_2^ \pm (1320)\pi ^ \mp ) = (1.31 \pm 0.69) \cdot 10^{ - 3} \hfill \\ BR(^3 S_1 \to \rho \eta ) = (3.29 \pm 0.90) \cdot 10^{ - 3} \hfill \\ BR(^1 P_1 \to \rho \eta ) = (0.94 \pm 0.53) \cdot 10^{ - 3} \hfill \\ BR(^1 S_0 \to f_2 (1270)\eta ) = (0.083 \pm 0.086) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to f_2 (1270)\eta ) = (0.64 \pm 0.26) \cdot 10^{ - 3} . \hfill \\ \end{gathered} $$ We find a 2 σ effect for the reaction \(\bar pp \to a_0^ \pm (980)\pi ^ \mp \) , \(a_0^ \pm \to \eta \pi ^ \pm \) , with a branching ratio of (0.13±0.07)·10?3. For η' production we give a branching ratio of \(\bar pp \to \rho \eta '\) of (1.81±0.44)·10?3 from3 S 1. We estmate a contribution of about 0.3·10?3 for ρη' fromP-states. The ratio of ρη and ρη' rpoduction is used to test the validity of the quark line rule. In theπ + π ? π + π ? γ final state we do not observe the reaction \(\bar pp \to \pi ^ + \pi ^ - \omega \) , ω→π + π ? λ and derive an upper limit of 3·10?3 for decay modeω→π + π ? λ. 相似文献
35.
36.
Amoretti M Amsler C Bonomi G Bowe PD Canali C Carraro C Cesar CL Charlton M Ejsing AM Fontana A Fujiwara MC Funakoshi R Genova P Hangst JS Hayano RS Jørgensen LV Kellerbauer A Lagomarsino V Lodi Rizzini E Macrì M Madsen N Manuzio G Mitchard D Montagna P Posada LG Pruys H Regenfus C Rotondi A Telle HH Testera G Van der Werf DP Variola A Venturelli L Yamazaki Y Zurlo N;ATHENA Collaboration 《Physical review letters》2006,97(21):213401
Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n = 11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration. 相似文献
37.
P. Weidenauer K. D. Duch H. Kalinowsky E. Klempt B. May J. Reifenröther C. Straßburger U. Gastaldi R. Landua W. Dahme J. C. Bizot B. Delcourt B. L. White C. Amsler M. Doser J. Riedlberger U. Straumann P. Truöl 《Zeitschrift fur Physik C Particles and Fields》1993,59(3):387-398
annihilation at rest into five pions was studied in the ASTERIX spectrometer by stopping antiprotrons from LEAR in a H2 or D2 gas target. In
annihilations in H2 leading to the +–+–0 final state, the invariant mass spectra of two, three, and four pions show no evidence for any new narrow states. In
the difference of the four pion mass spectra recoiling against a – and those recoiling against a + shows a resonance-like structure ( (1480)), confirming a previous analysis with a smaller event sample. The (1480) mass is shown to depend strongly on the momentum of the spectator proton. In H2, we searched for the (1480) in the reaction
(1480), (1480) +–+– to clarify whether the (1480) is identical to the 4-mode of thef
2 (1520). No evidence for this decay mode was found. A prominent resonance in
innihilation into five pions is the meson. We find two quasi-two-body intermediate states:
and
(1235). The mass and width of theb
1 (1235) are determined to be:
相似文献
38.
Flores-Livas JA Amsler M Lenosky TJ Lehtovaara L Botti S Marques MA Goedecker S 《Physical review letters》2012,108(11):117004
A systematic ab initio search for low-enthalpy phases of disilane (Si2H6) at high pressures was performed based on the minima hopping method. We found a novel metallic phase of disilane with Cmcm symmetry, which is enthalpically more favorable than the recently proposed structures of disilane up to 280 GPa, but revealing compositional instability below 190 GPa. The Cmcm phase has a moderate electron-phonon coupling yielding a superconducting transition temperature T(c) of around 20 K at 100 GPa, decreasing to 13 K at 220 GPa. These values are significantly smaller than previously predicted T(c))s for disilane at equivalent pressure. This shows that similar but different crystalline structures of a material can result in dramatically different T(c)'s and stresses the need for a systematic search for a crystalline ground state. 相似文献
39.
We have performed extensive small-angle neutron scattering (SANS) diffraction studies of the vortex lattice in single crystal
YNi2B2C for B‖c. High-resolution SANS, combined with a field-oscillation vortex lattice preparation technique, allows us to separate Bragg
scattered intensities from two orthogonal domains and accurately determine the unit cell angle, β. The data suggest that upon increasing field there is a finite transition width where both low- and high-field distorted
hexagonal vortex lattice phases, mutually rotated by 45°, coexist. The smooth variation of diffracted intensity from each
phase through the transition corresponds to a redistribution of populations between the two types of domains. 相似文献
40.
De S Willand A Amsler M Pochet P Genovese L Goedecker S 《Physical review letters》2011,106(22):225502
Using the minima hopping global geometry optimization method on the density functional potential energy surface we show that the energy landscape of boron clusters is glasslike. Larger boron clusters have many structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found. We thus present a methodology which can make predictions on the feasibility of the synthesis of new nanostructures. 相似文献
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