| 1. |
- Abt, I, et al.
(författare)
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Measurement of the b(b)over-bar production cross section in 920 GeV fixed-target proton-nucleus collisions
- 2003
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 26:3, s. 345-355
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Tidskriftsartikel (refereegranskat)abstract
- Using the HERA-B detector, the b (b) over bar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b (b) over bar production was tagged via inclusive bottom quark decays into J/psi by exploiting the longitudinal separation of J/psi --> l(+)l(-) decay vertices from the primary proton-nucleus interaction. Both e(+)e(-) and mu(+)mu(-) channels have been reconstructed and the combined analysis yields the cross section sigma(b (b) over bar) = 32(-12)(+14)(stat) (+6)(-7)(sys) nb/nucleon.
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| 2. |
- Abt, I, et al.
(författare)
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Inclusive V-0 production cross sections from 920 GeV fixed target proton-nucleus collisions
- 2003
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 29:2, s. 181-190
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Tidskriftsartikel (refereegranskat)abstract
- Inclusive differential cross sections dsigma(pA)/dx(F) and dsigma(pA)/dp(t)(2) for the production of K-S(0), Lambda, and (&ULambda;) over bar particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to roots = 41.6 GeV in the proton-nucleon system. The ratios of differential cross sections dsigma(pA)(K-S(0))/dsigma(pA)(Lambda) and dsigma(pA)((&ULambda;) over bar)/dsigma(pA) (Lambda) are measured to be 6.2 +/- 0.5 and 0.66 +/- 0.07, respectively, for x(F) approximate to -0.06. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions da,Ald t also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections sigma(pA) on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon sigma(pN) are compared with results obtained at other energies.
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| 3. |
- Nieminen, T. A., et al.
(författare)
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Tailoring particles for optical trapping and micromanipulation: An overview
- 2008
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Ingår i: Piers 2008 Hangzhou: Progress in Electromagnetics Research Symposium, Vols I and Ii, Proceedings. - 9781934142004 ; , s. 864-868
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Konferensbidrag (refereegranskat)abstract
- Optical trapping and micromanipulation has developed from an interesting novelty to a powerful and widely used tool, with the capability to move or trap microscopic live biological specimens and measure forces on the order of piconewtons, typical of forces in microbiological systems. Despite this, the range of particles typically trapped or manipulated is quite small, and it is unusual to see applications involving objects other than biological specimens or homogeneous isotropic microspheres, typically polymer or silica. However, particles can be modified or specially fabricated to expand the possible applications of optical tweezers. For example, while non-absorbing homogeneous isotropic spheres cannot be rotated, optically anisotropic spheres can, and can therefore function as microscopic torque sensors, extending the usual translational micromanipulation and force measurement to rotational manipulation and torque sensing. The development of such particles has led to applications in microscale metrology and biophysics, along with potential deployment of optically-driven micro-machines in lab-on-a-chip devices. We present an overview of our work on the tailoring of microparticles for versatile optical trapping and micromanipulation. This includes approaches based on controlled chemistry - nano-assembly - and optical microfabrication. Beginning with the production of anisotropic vaterite microspheres, we review some. of the applications, and difficulties encountered along the way. Some of these difficulties can be overcome by coating of the vaterite microspheres. We also discuss the use of anti-reflection coating to allow strong trapping of high refractive index particles. The alternative strategy of producing arbitrarily shaped polymer microstructures through two-photon photopolymerization is also discussed. This can be used to produce optically-driven microrotors or structurally anisotropic microspheres to replace vaterites for particular applications.
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| 4. |
- Parkin, S. J., et al.
(författare)
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Highly birefringent vaterite microspheres: production, characterization and applications for optical micromanipulation
- 2009
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Ingår i: Optics Express. - 1094-4087. ; 17:24, s. 21944-21955
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a simple synthesis and characterization of highly birefringent vaterite microspheres, which are composed of 20-30 nm sized nanocrystalls. Scanning electron microscopy shows a quite disordered assembly of nanocrystals within the microspheres. However, using optical tweezers, the effective birefringence of the microspheres was measured to Delta n = 0.06, which compares to Delta n = 0.1 of vaterite single crystals. This suggests a very high orientation of the nanocrystals within the microspheres. A hyperbolic model of the direction of the optical axis throughout the vaterite spherulite best fits the experimental data. Results from polarized light microscopy further confirm the hyperbolic model. (C) 2009 Optical Society of America
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