| 1. |
- Oberstedt, Andreas, et al.
(författare)
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Energy degrader technique for light-charged particle spectroscopy at LOHENGRIN
- 2007
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - Amsterdam : Elsevier. - 0168-9002 .- 1872-9576. ; 570:1, s. 51-54
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Tidskriftsartikel (refereegranskat)abstract
- The recoil mass-separator LOHENGRIN at Institute Laue-Langevin was originally designed for the spectrometry of binary fission fragments. Nevertheless, it was also used in the past for measuring light-charged particles from ternary fission. However, due to the electric field settings the energy distribution of the lightest particles was not completely accessible, which made the determination of mean kinetic energies, widths and, hence, emission yields difficult. In this paper we present an energy degrader technique that allows for the measurement of the entire energy spectrum of even the lightest ternary particles with LOHENGRIN.
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| 2. |
- Oberstedt, Andreas, et al.
(författare)
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Identification of a Shape Isomer in 235U
- 2007
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Ingår i: Physical Review Letters. - : The American Physical Society. - 0031-9007 .- 1079-7114. ; 99:4, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- The shape isomer in 235U has been searched for in a neutron-induced fission experiment on 234U, which was performed at the isomer spectrometer NEPTUNE of the EC-JRC IRMM. A neutron source, with a tunable pulse frequency in the Hz to kHz range and its individually adjustable neutron pulse width in connection with an appropriate detector system turned out to be the ideal instrument to perform an isomer search, when decay half-lives above 100 us are expected. From the delayed fission events observed for two different NEPTUNE settings and at mean incident neutron energies En = 0.95 and 1.27 MeV the isomeric fission half-life could be determined to be T_1/2 = (3.6 ± 1.8) ms. The corresponding cross section was determined to sigma_if = (10 ± 8) ub. With these results an experimental confirmation for the existence of a superdeformed shape isomer in odd-uranium isotopes is given for the first time.
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| 3. |
- Abat, E., et al.
(författare)
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Combined performance studies for electrons at the 2004 ATLAS combined test-beam
- 2010
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Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 5, s. P11006-
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Tidskriftsartikel (refereegranskat)abstract
- In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.
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| 4. |
- Abbasi, R., et al.
(författare)
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Calibration and characterization of the IceCube photomultiplier tube
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 618:1-3, s. 139-152
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Tidskriftsartikel (refereegranskat)abstract
- Over 5000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-in. diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts. (C) 2010 Elsevier B.V. All rights reserved.
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| 5. |
- Abbasi, R., et al.
(författare)
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Search for muon neutrinos from gamma-ray bursts with the IceCube neutrino telescope
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 710:1, s. 346-359
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of searches for high-energy muon neutrinos from 41 gamma-ray bursts (GRBs) in the northern sky with the IceCube detector in its 22 string configuration active in 2007/2008. The searches cover both the prompt and a possible precursor emission as well as a model-independent, wide time window of -1 hr to + 3 hr around each GRB. In contrast to previous searches with a large GRB population, we do not utilize a standard Waxman-Bahcall GRB flux for the prompt emission but calculate individual neutrino spectra for all 41 GRBs from the burst parameters measured by satellites. For all of the three time windows, the best estimate for the number of signal events is zero. Therefore, we place 90% CL upper limits on the fluence from the prompt phase of 3.7 x 10(-3) erg cm(-2) (72 TeV-6.5 PeV) and on the fluence from the precursor phase of 2.3 x 10(-3) erg cm(-2) (2.2-55 TeV), where the quoted energy ranges contain 90% of the expected signal events in the detector. The 90% CL upper limit for the wide time window is 2.7 x 10(-3) erg cm(-2) (3 TeV-2.8 PeV) assuming an E-2 flux.
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| 6. |
- Aleksandrovskii, A. N., et al.
(författare)
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Thermal expansion of single-crystal fullerite C60 at helium temperatures
- 2000
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 26:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of single-crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2–10 K). At temperatures below ~4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with the previous results on polycrystalline materials. A qualitative explanation of the results is proposed.
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| 7. |
- Andersson, Ove, et al.
(författare)
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Reorientational relaxation in C60 following a pressure induced change in the pentagon/hexagon equilibrium ratio
- 1995
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Ingår i: Physics Letters A. - : Elsevier Science B.V.. - 0375-9601 .- 1873-2429. ; 206:3-4, s. 260-264
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Tidskriftsartikel (refereegranskat)abstract
- The orientational structure of C60 depends on pressure and temperature. Pressurization below the glass transition temperature Tg can freeze in non-equilibrium orientational structures. The relaxation of such structures on heating through Tg has been studied through thermal conductivity measurements and the effects observed are explained in a simple model.
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| 8. |
- Lundin, Anders, et al.
(författare)
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Compressibility and Structure of C70
- 1995
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 30:8, s. 469-474
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Tidskriftsartikel (refereegranskat)abstract
- The compressibility of C70 has been investigated by means of direct piston and cylinder measurements in the temperature range 150 to 365 K and up to 1 GPa. At 296 and 343 K we find a very rapid change of volume with pressure below 0.15 GPa. We tentatively interpret this as a continuous molecular reorientation with pressure, probably resulting in a transformation from a mixture of face-centred cubic (f.c.c.) and rhombohedral (r.h.) phases to mainly pure r.h. phase. At 365 K as well as at 236 K and below we see no anomalies indicating any structural or rotational anomalies in the pressure range investigated. The zero-pressure bulk modulus decreases with increasing temperature, from 13.1 GPa at 185 K to 7.9 GPa at 365 K. Our volumetric measurements confirm a recently proposed phase diagram for C70.
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| 9. |
- Lundin, Anders, et al.
(författare)
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Compressibility of C61D2 up to 1 GPa in the temperature range 175 - 345 K
- 1996
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Ingår i: Carbon. - : Elsevier Science Ltd.. - 0008-6223 .- 1873-3891. ; 34:9, s. 1119-1121
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the bulk modulus K for C61D2 up to 1 GPa in the temperature range 175–343 K. For face-centered cubic C61D2 above 290 K, we find an anomalously low value for K below about 0.15 GPa, possibly indicating pressure-induced changes in the structure. The (extrapolated) zero-p bulk modulus K(0) decreases with increasing T from 6.7 GPa at 175 K to 5.2 GPa at 343 K. A comparison with hypothetical expanded f.c.c. C60 with the same lattice constant shows that K(0) values are similar, indicating that the main intermolecular interactions are still between molecular bellies, not the sidegroups.
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| 10. |
- Nagel, Peter, et al.
(författare)
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C60 one- and two-dimensional polymers, dimers, and hard fullerite: Thermal expansion, anharmonicity, and kinetics of depolymerization
- 1999
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 60:24, s. 16920-16927
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Tidskriftsartikel (refereegranskat)abstract
- We report on high-resolution thermal expansion measurements of high-temperature-pressure treated C60 [one-dimensional (1D) and (2D) polymers and “hard fullerite”], as well as of C60 dimers and single crystal monomer C60 between 10 and 500 K. Polymerization drastically reduces the thermal expansivity from the values of monomeric C60 due to the stronger and less anharmonic covalent bonds between molecules. The expansivity of the “hard” material approaches that of diamond. The large and irreversible volume change upon depolymerization between 400 and 500 K makes it possible to study the kinetics of depolymerization, which is described excellently by a simple activated process, with activation energies of 1.9±0.1 eV (1D and 2D polymers) and 1.75±0.05 eV (dimer). Although the activation energies are very similar for the different polymers, the depolymerization rates differ by up to four orders of magnitude at a given temperature, being fastest for the dimers. Preliminary kinetic data of C70 polymers are presented as well.
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| 11. |
- Persson, Per-Axel, et al.
(författare)
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NMR and Raman characterization of pressure polymerized C-60
- 1996
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 258:5-6, s. 540-546
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Tidskriftsartikel (refereegranskat)abstract
- Bulk C60 has been treated at 1.1 GPa and 550–585 K, producing a dense insoluble material which on heating to above 600 K reverts to normal C60. Raman and IR studies on modified material show a large number of new lines, and the Raman pentagon pinch mode shifts from 1469 to 1458 cm−1 as on photopolymerization. MAS NMR shows one broadened line at the original C60 shift 144 ppm and a small peak at about 77 ppm due to the bridging carbons. None of the new resonances observed for C60 polymerized by other methods were observed. The results verify previously suggested polymeric structures where the fullerence cages are connected by four-membered rings.
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| 12. |
- Persson, Per-Axel, et al.
(författare)
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The physical properties of high-pressure polymerized C60
- 1997
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Ingår i: Journal of Physics and Chemistry of Solids, volume 58, issue 11. - : Elsevier B.V.. ; 58:11, s. 1881-1885
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Konferensbidrag (refereegranskat)abstract
- We have studied the structural, thermophysical, and spectroscopic properties of polymeric C60 obtained by high pressure treatment at pressures and temperatures near 1 GPa and 600 K. We present here a brief overview of our results for the structural and thermophysical properties and a more detailed report on recent results obtained by Raman spectroscopy on both thin films, polycrystalline, and single crystal material. The results presented include a comparison between Raman results for photopolymerized and pressure polymerized thin films and a preliminary estimate of the binding energy of polymeric C60.
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| 13. |
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| 14. |
- Sing, M., et al.
(författare)
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Electronic structure studies of pressure-polymerized C60
- 1999
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Ingår i: Synthetic Metals vol. 103. - : Elsevier B.V.. ; 103:1-3, s. 2454-2455
-
Konferensbidrag (refereegranskat)abstract
- We have investigated the electronic structure of one and two-dimensional C60 polymers with regard to both their low-lying excitations and C 1s excitation spectra by means of electron energy-loss spectroscopy in transmission. We compare the results with those for pristine C60. In general, the spectra for the polymers resemble those for pristine C60 but show a broadening due to both the lowering of the symmetry and the increased intermolecular overlap. This is also reflected by a reduction of the optical gap in comparison with pristine C60.
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| 15. |
- Soldatov, Alexander, et al.
(författare)
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Molecular rotation in C70 at high pressures: a thermal conductivity study
- 1996
-
Ingår i: Journal of Physics and Chemistry of Solids. - : Elsevier Science Ltd. - 0022-3697 .- 1879-2553. ; 57:9, s. 1371-1375
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the thermal conductivity ε and the heat capacity per unit volume varrhocp of highly pure C70 in the temperature interval 100–450 K under pressures up to 1 GPa. Anomalies indicating freezing of uniaxial molecular rotation were observed in λ and varrhocp upon both cooling and increasing pressure. The phase boundary for this transition has an approximate slope dT/dp = 70 K Gpa−1. The temperature and pressure dependence of λ indicate a substantial amount of structural defects in the sample and strong metastability effects.
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| 16. |
- Soldatov, Alexander, et al.
(författare)
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Polymeric fullerenes: from C60 to C70
- 1999
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Ingår i: AIP Conference Proceedings vol. 486. - Melville, NY : American Institute of Physics (AIP). - 1563969009 ; , s. 12-15
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Konferensbidrag (refereegranskat)abstract
- For the first time polymerization of both powder and single crystals of C70 fullerene was established after their subjection to high pressure (1.1 - 2 GPa) at elevated temperature (500 - 580 K). High-resolution capacitance dilatometry, FTIR/Raman spectroscopy and thermal conductivity were employed to characterise the polymeric phase of C70. The results demonstrate drastic changes in the physical properties of C70 on polymerization. We report on a reverse transformation to the monomeric state on heating the polymer to 500 K at ambient pressure. The activation energy of depolymerization was determined to be 1.8(1) eV. We discuss our results in terms of existing structural models for polymerization of C70 and compare the physical properties of C70 and C60 polymers.
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| 17. |
- Soldatov, Alexander, et al.
(författare)
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Transport and vibrational properties of pressure polymerized C60
- 1998
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Ingår i: Molecular Materials (Molecular Crystals and Liquid Crystals, Section C), vol. 11. - Amsterdam : Overseas Publishers Association. ; 11:1-2, s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- The vibrational spectrum of polycrystalline C60 polymerized at 1.1 GPa and 585 K was studied by inelastic neutron scattering. We find drastic changes in the spectrum compared to the vibrational spectrum of pristine C60: the appearance of a new, broad vibrational band at low energies, and splitting and significant changes in the peak positions of various modes. The thermal conductivity lambda of polymerized C60 was measured in the temperature range 150-320 K and was found to increase with a rise in temperature, which reflects strong phonon scattering. A high degree of structural disorder in the crystalline lattice of the polymeric phase is most probably responsible for the glass-like beahviour of lambda(T).
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| 18. |
- Sundqvist, Bertil, et al.
(författare)
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Phase diagram, structure, and disorder in C60 below 300 K and 1 GPa
- 1995
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Ingår i: Solid State Communications. - : Elsevier Science Ltd. - 0038-1098 .- 1879-2766. ; 93:2, s. 109-112
-
Tidskriftsartikel (refereegranskat)abstract
- Earlier structural studies have shown that the pentagon-to-hexagon orientation ratio in the orientationally ordered simple cubic phase of C60 decreases under pressure. From anomalies observed in the compressibility and thermal conductivity of C60 under pressure we have deduced a pressure-temperature phase diagram for this substance in the range below 300 K and 1 GPa (10 kbar). We conclude that C60 forms a new, completely “hexagon” ordered structural phase above about 0.6 GPa at 150 K (1.2 GPa at 300 K), and that the glass transition shifts upwards in T under pressure by 54 K GPa−1. However, above 0.1 GPa, pentagon-to-hexagon orientation relaxation seems to occur on heating at an almost pressure independent temperature near 100 K.
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| 19. |
- Sundqvist, Bertil, et al.
(författare)
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Structural and physical properties of pressure polymerized C60
- 1998
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Ingår i: Carbon, vol. 36 issue 5-6. - : Elsevier B.V.. ; 36:5-6, s. 657-660
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Konferensbidrag (refereegranskat)abstract
- We discuss the structural and dynamic properties of C60 polymerized under low-P, low-T conditions, and suggest that the disordered mixed orthorhombic-tetragonal-rhombohedral phases produced under these conditions arise from nucleation of molecular chains in random directions because of the quasi-free molecular rotation under standard reaction conditions in the fcc phase of C60. Polymerization in He gives results qualitatively different from those obtained in other media.
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| 20. |
- Wågberg, Thomas, et al.
(författare)
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2D polymerization and doping of fullerenes under pressure
- 2000
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Ingår i: High Pressure Research vol. 18. - : Gordon & Breach. ; 18:1-6, s. 139-143
-
Konferensbidrag (refereegranskat)abstract
- Tetragonal polymeric C60 has been studied by Raman spectroscopy and other methods. Attempts have been made to transform samples from the tetragonal to the orthorhom-bic phase and vice versa. The results suggest that the transformation is direct with no intermediate stage with free molecules. Tetragonal C60 has also been intercalated by potassium metal.
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| 21. |
- Bundzik, Daniel
(författare)
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Aspects of the Duality between Supersymmetric Yang-Mills Theory and String Theory
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with three topics related to the Ads/CFT correspondence. In Paper I, solutions describing the geometry of fractional D1-branes of Type IIB string theory are presented. The running coupling constant is computed on the gauge theory side. Paper II uses the idea that the anomalous dimension of a gauge theory operator can be interpreted as an eigenvalue of a spin chain Hamiltonian. The general Leigh-Strassler deformation is rewritten in terms of a spin-one spin chain and the integrability properties of the corresponding Hamiltonian are studied. In paper III a non-commutative multiplication law, a star product, is defined. From this star product the general Leigh-Strassler deformation is obtained, and it is shown that the deformation only results in prefactors to the amplitudes of the undeformed theory.
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| 22. |
- Aaltonen, T., et al.
(författare)
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Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode
- 2010
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061802-
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Tidskriftsartikel (refereegranskat)abstract
- We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W+W-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb(-1) of p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162-166 GeV at the 95% C.L.
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| 23. |
- Aaltonen, T., et al.
(författare)
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Combined Tevatron upper limit on gg -> H -> W+W- and constraints on the Higgs boson mass in fourth-generation fermion models
- 2010
-
Ingår i: Physical Review D. - 1550-7998. ; 82, s. 011102-
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Tidskriftsartikel (refereegranskat)abstract
- We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg -> H -> W+W- in p (p) over bar collisions at the Fermilab Tevatron Collider at root s = 1.96 TeV. With 4.8 fb(-1) of integrated luminosity analyzed at CDF and 5.4 fb(-1) at D0, the 95% confidence level upper limit on sigma(gg -> H) x B(H -> W+W-) is 1.75 pb at m(H) = 120 GeV, 0.38 pb at m(H) = 165 GeV, and 0.83 pb at m(H) = 200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.
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| 24. |
- Abazov, M, et al.
(författare)
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A novel method for modeling the recoil in W boson events at hadron colliders
- 2009
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 609:2-3, s. 250-262
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Tidskriftsartikel (refereegranskat)abstract
- We present a new method for modeling the hadronic recoil in W -> lv events produced at hadron colliders. The recoil is chosen from a library of recoils in Z -> ll data events and overlaid on a simulated W -> lv event. Implementation of this method requires that the data recoil library describe the proper-ties of the measured recoil as a function of the true, rather than the measured, transverse momentum of the boson. We address this issue using a multidimensional Bayesian unfolding technique. We estimate the statistical and systematic uncertainties from this method for the W boson mass and width measurements assuming 1 fb(-1) of data from the Fermilab Tevatron. The uncertainties are found to be small and comparable to those of a more traditional parameterized recoil model. For the highprecision measurements that will be possible with data from Run 11 of the Fermilab Tevatron and from the CERN LHC, the method presented in this paper may be advantageous, since it does not require an understanding of the measured recoil from first principles.
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| 25. |
- Abazov, M, et al.
(författare)
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Combination of t(t)over-bar cross section measurements and constraints on the mass of the top quark and its decays into charged Higgs bosons
- 2009
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 80, s. 071102-
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Tidskriftsartikel (refereegranskat)abstract
- We combine measurements of the top quark pair production cross section in p (p) over bar collisions in the l + jets, ll, and tau l final states ( where l is an electron or muon) at a center of mass energy of root s = 1.96 TeV in 1 fb(-1) of data collected with the D0 detector. For a top quark mass of 170 GeV/c(2), we obtain sigma(t (t) over bar) = 8.18(-0.87)(+0.98) pb in agreement with the theoretical prediction. Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined t (t) over bar cross section, consistent with the world average of the top quark mass. In addition, the ratios of t (t) over bar cross sections in different final states are used to set upper limits on the branching fractions B(t -> H(+)b -> tau(+) vb) and B(t -> H(+)b -> c (s) over barb) as a function of the charged Higgs boson mass.
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