| 1. |
- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 2. |
- Fujita, Y., et al.
(författare)
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Identification of the [202]3/2 deformed band in mirror nuclei Mg-25 and Al-25 and implications for unstable nuclei
- 2006
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Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 194-195
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Tidskriftsartikel (refereegranskat)abstract
- Fifty years after its prediction, the highest-lying [ 2 0 2] 3) 2 orbit among the six Nilsson single-particle orbits originating from the sd shell in prolately deformed nuclei and the rotational band on this orbit were identified. The band members were observed in Al-25 at excitation energies of 6-7.5MeV in a high-resolution Mg-25(He-3,t) charge-exchange reaction at 0 degrees having a strong selectivity for Gamow-Teller transitions. In comparison with the analogous M1 transitions in Mg-25, the J(pi) = 3/+ band-head state and the excited 5/+ and 7/2+ members were clearly assigned.
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| 3. |
- Mathieu, Roland, et al.
(författare)
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Bandwidth-disorder phase diagram of half-doped layered manganites
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:2
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Tidskriftsartikel (refereegranskat)abstract
- Phase diagrams in the plane of rA (the average ionic radius, related to the one-electron bandwidth W) and σ2 (the ionic radius variance, measuring the quenched disorder), or bandwidth-disorder phase diagrams, have been established for perovskite manganites, with a three-dimensional (3D) Mn-O network. Here we establish the intrinsic bandwidth-disorder phase diagram of half-doped layered manganites with a two-dimensional (2D) Mn-O network, examining in detail the parent state of the colossal magnetoresistance phenomenon in crystals without ferromagnetic instability. The consequences of the reduced dimensionality, from 3D to 2D, for the order-disorder phenomena in the charge-orbital sectors are also highlighted.
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| 4. |
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| 5. |
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| 6. |
- Mathieu, Roland, et al.
(författare)
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Coexistence of long-ranged charge and orbital order and spin-glass state in single-layered manganites with weak quenched disorder
- 2007
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 80:3, s. 37001-
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between orbital and spin degrees of freedom in the single crystals of the hole-doped Pr1-xCa1+xMnO4, 0.3 <= x <= 0.7 has been investigated by means of ac-magnetometry and charge transport. We show that in an intermediate underdoped region, with 0.35 <= x < 0.5, the "orbital-master spin-slave" relationship commonly observed in half-doped manganites does not take place. The long-ranged charge-orbital order is not accompanied by an antiferromagnetic transition at low temperatures, but by a frustrated short-ranged magnetic state bringing forth a spin-glass phase. We discuss in detail the nature and origin of this true spin-glass state, which, as in the half-doped manganites with large quenched disorder, is not related to the macroscopic phase separation observed in crystals with minor defects or impurities.
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| 7. |
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| 8. |
- Holmström, Petter, et al.
(författare)
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Intersubband photonic devices by group-III nitrides
- 2007
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Ingår i: Optoelectronic Materials And Devices II. - : SPIE. - 9780819469458 ; , s. N7821-N7821
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Konferensbidrag (refereegranskat)abstract
- The characteristics of intersubband transitions in III-nitride quantum wells are promising for detectors and all-optical switches through a high intrinsic speed (similar to 1 THz), and can also provide a high optical saturation power and a desired small negative chirp parameter in electroabsorption modulators. The high LO-phonon energy allows to improve the operating temperature of THz emitters. Recent achievements and prospects for intersubband III-nitride photonic devices, mainly for lambda=1.55 mu m, are briefly reviewed. Further, means to enhance material quality by achieving crack-free growth of GaN/AlN multiple-quantum-well (MQW) structures, and by employing intersubband transitions in multiple-quantum-disk (MQD) structures incorporated into dislocation free GaN nanocolumns are discussed. We investigate the occurrence of cracks in MBE-grown GaN/AlN MQWs on GaN MOVPE templates with respect to the buffer layer, the number of QWs and the temperature reduction rate after growth. Intersubband absorption in GaN/AlN MQDs in the wavelength range 1.38-1.72 mu m is demonstrated in three samples grown on Si(111).
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