The Effect of Controlled Frequency and Amplitude of Vibration on Friction

Abdo, Jamil; Al-Yhmadi, Amer

doi:10.4028/www.scientific.net/ssp.147-149.380

Cited by 25 publications

(83 citation statements)

References 13 publications

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“…This upper limit is O(10 3 − 10 9 ) above the values predicted by those SUSY models used in their analysis and therefore no constraints could be put on the parameter space. Also the Fermi collaboration has recently reported their upper limits for a possible γ-ray annihilation signal from Draco at lower energies [9], given that no significant gamma emission was detected above 100 MeV.…”

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confidence: 99%

Impact of internal bremsstrahlung on the detection ofγrays from neutralinos

et al. 2010

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We present a detailed study of the effect of internal bremsstrahlung photons in the context of the minimal supersymmetric standard models and their impact on γ-ray dark matter annihilation searches. We find that although this effect has to be included for the correct evaluation of fluxes of high energy photons from neutralino annihilation, its contribution is relevant only in models and at energies where the lines contribution is dominant over the secondary photons. Therefore, we find that the most optimistic supersymmetric scenarios for dark matter detection do not change significantly when including the internal bremsstrahlung. As an example, we review the γ-ray dark matter detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC stereoscopic system and the CTA project. Though the flux of high energy photons is enhanced by an order of magnitude in some regions of the parameter space, the expected fluxes are still much below the sensitivity of the instruments. The minimal supersymmetric (SUSY) extension of the standard model (MSSM) provides a natural candidate for dark matter (DM) in the form of a neutral, stable Majorana fermion, the lightest neutralino. At present, large efforts are being carried out to detect this SUSY DM by different methods, see [1] for reviews.In the case of the current imaging atmospheric Cherenkov telescopes (IACTs), the searches are based on the detectability of γ-rays coming from the annihilation of the SUSY DM particles in the halo of galaxies [2]. Neutralinos annihilate at the one loop level into photons through the processes [3] χχ → γγ, χχ → Zγ, with almost monochromatic outgoing photons of energies E γ ∼ m χ E γ ∼ m χ − m 2 Z /4m χ , respectively. Moreover, neutralino annihilation can produce a continuum spectrum of secondary photons from hadronization and decay of the annihilation products, mostly from neutral pion decay, which typically dominates over the number monochromatic γ's in a large portion of the parameter space. IACTs in operation like MAGIC, HESS, VER-ITAS [4] or satellites-based experiments like the Fermi satellite [5] play a very important role in this kind of DM searches. For these experiments, dwarf spheroidal (dSph) galaxies around the Milky Way represent a good alternative target option to e.g. the Galactic Center, already observed in γ-rays but with null DM detection so far [6]. Dsphs are DM dominated systems with inferred very high mass-to-light ratios, and most of them are expected to be free from any other astrophysical source that might contribute to a possible γ-ray signal. Therefore, the detection of γ-rays from them would probably imply a successful DM annihilation detection.

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confidence: 99%

Impact of internal bremsstrahlung on the detection ofγrays from neutralinos

et al. 2010

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“…Spherical harmonics decomposition method has a better performance for signals with smooth energy dependence. In Section IV B we find conservative limits on bb DM annihilation only a factor of a few less constraining than the limits from dwarf spheroidal galaxies [17].…”

Section: B Bin To Bin Fittingmentioning

confidence: 99%

“…The flux of gamma-rays from DM annihilation per steradian at an angle θ from (13), (14), and (15). The profiles are defined in Section III D. upper bound on DM bb annihilation in an NFW profile in comparison with the dwarf spheroidal galaxies limit [17]. The bound is derived by using the NFW annihilation flux in Figure 3 as an upper limit.…”

Section: B Limits On Dm Annihilationmentioning

confidence: 99%

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Spherical harmonics analysis ofFermigamma-ray data and the Galactic dark matter halo

2011

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We argue that the decomposition of gamma-ray maps in spherical harmonics is a sensitive tool to study dark matter (DM) annihilation or decay in the main Galactic halo of the Milky Way. Using the spherical harmonic decomposition in a window excluding the Galactic plane, we show for one year of Fermi data that adding a spherical template (such as a line-of-sight DM annihilation profile) to an astrophysical background significantly reduces χ 2 of the fit to the data. In some energy bins the significance of this DM-like fraction is above three sigma. This can be viewed as a hint of DM annihilation signal, although astrophysical sources cannot be ruled out at this moment. We use the derived DM fraction as a conservative upper limit on DM annihilation signal. In the case of b b annihilation channel the limits are about a factor of two less constraining than the limits from dwarf galaxies. The uncertainty of our method is dominated by systematics related to modeling the astrophysical background. We show that with one year of Fermi data the statistical sensitivity would be sufficient to detect DM annihilation with thermal freeze out cross section for masses below 100 GeV.

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“…Most notably, the Fermi gamma-ray space telescope (Atwood et al 2009) set significant limits on the pair-annihilation rate of dark matter from the non-observation, in gamma rays, of nearby dwarf spheroidal galaxies (Abdo et al 2010a), of clusters of galaxies (Ackermann et al 2010a) and of monochromatic gamma-ray lines (Abdo et al 2010b). Atmospheric Cherenkov telescopes, such as the Very Energetic Radiation Imaging Telescope Array System (VERITAS), the High Energy Stereoscopic System (H.E.S.S.)…”

Section: 32mentioning

confidence: 99%

The impact of recent advances in laboratory astrophysics on our understanding of the cosmos

et al. 2012

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Abstract. An emerging theme in modern astrophysics is the connection between astronomical observations and the underlying physical phenomena that drive our cosmos. Both the mechanisms responsible for the observed astrophysical phenomena and the tools used to probe such phenomena -the radiation and particle spectra we observe -have their roots in atomic, molecular, condensed matter, plasma, nuclear and particle physics. Chemistry is implicitly included in both molecular and condensed matter physics. This connection is the theme of the present report, which provides a broad, though non-exhaustive, overview of progress in our understanding of the cosmos resulting from recent theoretical and experimental advances in what is commonly called laboratory astrophysics. This work, carried out by a diverse community of laboratory astrophysicists, is increasingly important as astrophysics transitions into an era of precise measurement and high fidelity modeling.

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The Effect of Controlled Frequency and Amplitude of Vibration on Friction

Cited by 25 publications

References 13 publications

Impact of internal bremsstrahlung on the detection ofγrays from neutralinos

Impact of internal bremsstrahlung on the detection ofγrays from neutralinos

Spherical harmonics analysis ofFermigamma-ray data and the Galactic dark matter halo

The impact of recent advances in laboratory astrophysics on our understanding of the cosmos

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