| 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. |
- Donnarumma, I., et al.
(författare)
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Multiwavelength Observations of 3C 454.3. II. The AGILE 2007 December Campaign
- 2009
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Ingår i: Astrophysical Journal Letters. - 2041-8205. ; 707:2, s. 1115-1123
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Tidskriftsartikel (refereegranskat)abstract
- We report on the second Astrorivelatore Gamma a Immagini Leggero (AGILE) multiwavelength campaign of the blazar 3C 454.3 during the first half of 2007 December. This campaign involved AGILE, Spitzer, Swift, Suzaku, the Whole Earth Blazar Telescope (WEBT) consortium, the Rapid Eye Mount (REM), and the Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME) telescopes, offering a broadband coverage that allowed for a simultaneous sampling of the synchrotron and inverse Compton (IC) emissions. The two-week AGILE monitoring was accompanied by radio to optical monitoring by WEBT and REM, and by sparse observations in mid-infrared and soft/ hard X-ray energy bands performed by means of Target of Opportunity observations by Spitzer, Swift, and Suzaku, respectively. The source was detected with an average flux of similar to 250 x 10(-8) photons cm(-2) s(-1) above 100 MeV, typical of its flaring states. The simultaneous optical and gamma-ray monitoring allowed us to study the time lag associated with the variability in the two energy bands, resulting in a possible <= one-day delay of the gamma-ray emission with respect to the optical one. From the simultaneous optical and gamma-ray fast flare detected on December 12, we can constrain the delay between the gamma-ray and optical emissions within 12 hr. Moreover, we obtain three spectral energy distributions (SEDs) with simultaneous data for 2007 December 5, 13, and 15, characterized by the widest multifrequency coverage. We found that a model with an external Compton on seed photons by a standard disk and reprocessed by the broad-line regions does not describe in a satisfactory way the SEDs of 2007 December 5, 13, and 15. An additional contribution, possibly from the hot corona with T = 10(6) K surrounding the jet, is required to account simultaneously for the softness of the synchrotron and the hardness of the IC emissions during those epochs.
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| 3. |
- Pittori, C., et al.
(författare)
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First AGILE catalog of high-confidence gamma-ray sources
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 506:3, s. 1563-1574
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Tidskriftsartikel (refereegranskat)abstract
- We present the first catalog of high-confidence gamma-ray sources detected by the AGILE satellite during observations performed from July 9, 2007 to June 30, 2008. Cataloged sources were detected by merging all the available data over the entire time period. AGILE, launched in April 2007, is an ASI mission devoted to gamma-ray observations in the 30 MeV-50 GeV energy range, with simultaneous X-ray imaging capability in the 18-60 keV band. This catalog is based on Gamma-Ray Imaging Detector (GRID) data for energies greater than 100 MeV. For the first AGILE catalog, we adopted a conservative analysis, with a high-quality event filter optimized to select gamma-ray events within the central zone of the instrument field of view (radius of 40 degrees). This is a significance-limited (4 sigma) catalog, and it is not a complete flux-limited sample due to the non-uniform first-year AGILE sky coverage. The catalog includes 47 sources, 21 of which are associated with confirmed or candidate pulsars, 13 with blazars (7 FSRQ, 4 BL Lacs, 2 unknown type), 2 with HMXRBs, 2 with SNRs, 1 with a colliding-wind binary system, and 8 with unidentified sources.
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| 4. |
- Tavani, M., et al.
(författare)
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Detection of Gamma-Ray Emission from the Eta-Carinae Region
- 2009
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Ingår i: ASTROPHYSICAL JOURNAL LETTERS. - 2041-8205. ; 698:2, s. L142-L146
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of extensive observations by the gamma-ray AGILE satellite of the Galactic region hosting the Carina nebula and the remarkable colliding wind binary Eta Carinae (eta Car) during the period 2007 July-2009 January. We detect a gamma-ray source (1AGL J1043-5931) consistent with the position of eta Car. If 1AGL J1043-5931 is associated with the Car system, our data provide the long sought first detection above 100 MeV of a colliding wind binary. The average gamma-ray flux above 100 MeV and integrated over the preperiastron period 2007 July-2008 October is F(gamma) = (37 +/- 5) x 10(-8) ph cm(-2) s(-1) corresponding to an average gamma-ray luminosity of L(gamma) = 3.4 x 10(34) erg s(-1) for a distance of 2.3 kpc. We also report a two-day gamma-ray flaring episode of 1AGL J1043-5931 on 2008 October 11-13 possibly related to a transient acceleration and radiation episode of the strongly variable shock in the system.
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