27307688
New physics in resonant production of Higgs boson pairs.
We advocate a search for an extended scalar sector at the LHC via hh production, where h is the 125 GeV Higgs boson. A resonance feature in the hh invariant mass is a smoking gun of an s-channel heavy Higgs resonance, H. With one h decaying to two photons and the other decaying to b quarks, the resonant signal may be discoverable above the hh continuum background for M(H)<1  TeV. The product of the scalar and top Yukawa couplings can be measured to better than 10%-20% accuracy, and its sign can be inferred from the hh line shape via interference effects.
119298520
The WIMP Forest: Indirect Detection of a Chiral Square
We consider the signals of indirect dark matter detection resulting from a theory of two universal extra dimensions compactified on a chiral square. Aside from the continuum emission, which is a generic prediction of most dark matter candidates, we find a series of prominent annihilation lines (a WIMP forest) that, after convolution with the angular resolution of current experiments, leads to a distinctive (2-bump plus continuum) spectrum, which may be visible in the near future with the Fermi Gamma-Ray Space Telescope (formerly known as GLAST).
119249502
Gamma rays from top-mediated dark matter annihilations
Lines in the energy spectrum of gamma rays are a fascinating experimental signal, which are often considered ''smoking gun" evidence of dark matter annihilation. The current generation of gamma ray observatories are currently closing in on parameter space of great interest in the context of dark matter which is a thermal relic. We consider theories in which the dark matter's primary connection to the Standard Model is via the top quark, realizing strong gamma ray lines consistent with a thermal relic through the forbidden channel mechanism proposed in the Higgs in Space Model. We consider realistic UV-completions of the Higgs in Space and related theories, and show that a rich structure of observable gamma ray lines is consistent with a thermal relic as well as constraints from dark matter searches and the LHC. Particular attention is paid to the one loop contributions to the continuum gamma rays, which can easily swamp the line signals in some cases, and have been largely overlooked in previous literature.
118342809
Gamma ray lines from a universal extra dimension
Indirect Dark Matter searches are based on the observation of secondary particles produced by the annihilation or decay of Dark Matter. Among them, gamma-rays are perhaps the most promising messengers, as they do not suffer deflection or absorption on Galactic scales, so their observation would directly reveal the position and the energy spectrum of the emitting source. Here, we study the detailed gamma-ray energy spectrum of Kaluza-Klein Dark Matter in a theory with 5 Universal Extra Dimensions. We focus in particular on the two body annihilation of Dark Matter particles into a photon and another particle, which produces monochromatic photons, resulting in a line in the energy spectrum of gamma rays. Previous calculations in the context of the five dimensional UED model have computed the line signal from annihilations into ??, but we extend these results to include ?Z and ?H final states. We find that these spectral lines are subdominant compared to the predicted ?? signal, but they would be important as follow-up signals in the event of the observation of the ?? line, in order to distinguish the 5d UED model from other theoretical scenarios.
118596941
Higgs in space
We consider the possibility that the Higgs can be produced in dark matter annihilations, appearing as a line in the spectrum of gamma rays at an energy determined by the masses of the WIMP and the Higgs itself. We argue that this phenomenon occurs generally in models in which the the dark sector has large couplings to the most massive states of the SM and provide a simple example inspired by the Randall-Sundrum vision of dark matter, whose 4d dual corresponds to electroweak symmetry-breaking by strong dynamics which respect global symmetries that guarantee a stable WIMP. The dark matter is a Dirac fermion that couples to a Z' acting as a portal to the Standard Model through its strong coupling to top quarks. Annihilation into light standard model degrees of freedom is suppressed and generates a feeble continuum spectrum of gamma rays. Loops of top quarks mediate annihilation into γZ, γh, and γZ', providing a forest of lines in the spectrum. Such models can be probed by the Fermi/GLAST satellite and ground-based Air Cherenkov telescopes.
3163182
Higgs-Pair Production and Measurement of the Triscalar Coupling at LHC(8,14)
Abstract We simulate the measurement of the triscalar Higgs coupling at LHC ( 8 , 14 ) via pair production of h (125 GeV). We find that the most promising hh final state is b b ¯ γ γ . We account for deviations of the triscalar coupling from its SM value and study the effects of this coupling on the hh cross-section and distributions with cut-based and multivariate methods. Our fit to the hh production matrix element at LHC(14) with 3 ab − 1 yields a 30% uncertainty on this coupling in the SM and a range of 20–60% uncertainties for non-SM values.
121807969
Dark matter search with PICASSO
PICASSO at SNOLAB searches primarily for spin-dependent WIMP interactions on 19F using the superheated droplet technique. This technique is based on the bubble chamber principle, where phase transitions in superheated liquid droplets can be triggered by WIMP induced nuclear recoils. The physics of the detection process allows a highly efficient suppression of backgrounds from cosmic muons, γ- and β-rays. We will discuss qualitatively recent progress in PICASSO and its sensitivity reach for spin-dependent and spin-independent WIMP searches.
9747172
The spectral characteristics of the 2 dFGRS – NVSS galaxies
We have analysed the 2dF spectra of a sample of galaxies common to the 2dF galaxy redshift survey (2dFGRS, Colless 1999) and the NRAO VLA sky survey (NVSS, Condon et al. 1998). Our sample comprises 88 galaxies selected by Sadler et al. (1999) from 30 2dFGRS fields observed in 1998. In this paper we discuss how this and future, much larger, samples of 2dFGRS–NVSS galaxies can be interpreted via analysis of those galaxies with strong narrow emission lines. Using diagnostic line ratio measurements we confirm the majority of the eyeball classifications of Sadler et al. (1999), although many galaxies show evidence of being ‘composite’ galaxies – a mixture of AGN plus starburst components.
119371788
The properties of extragalactic radio sources selected at 20 GHz
We present some first results on the variability, polarization and general properties of radio sources selected at 20 GHz, the highest frequency at which a sensitive radio survey has been carried out over a large area of sky. Sources with flux densities above 100 mJy in the Australia
56011481
The Australia Telescope 20 GHz (AT20G) Survey: analysis of the extragalactic source sample
The Australia Telescope 20 GHz (AT20G) survey is a blind survey of the whole Southern sky at 20 GHz with follow-up observations at 4.8, 8.6 and 20 GHz carried out with the Australia Telescope Compact Array (ATCA) from 2004 to 2008. In this paper we present an analysis of radio spectral properties in total intensity and polarization, sizes, optical identifications and redshifts of the sample of the 5808 extragalactic sources in the survey catalogue of confirmed sources over 6.1 sr in the Southern sky (i.e. the whole Southern sky excluding the strip at Galactic latitude |b| < ). 
 
 
 
The sample has a flux density limit of 40 mJy. Completeness has been measured as a function of scan region and flux density. Averaging over the whole survey area the follow-up survey is 78 per cent complete above 50 mJy and 93 per cent complete above 100 mJy. 3332 sources with declination δ − 0.5 (S∝να). The fraction of flat-spectrum sources decreases from 81 per cent for S20 GHz > 500 mJy to 60 per cent for S20 GHz < 100 mJy. There is also a clear spectral steepening at higher frequencies with the median α decreasing from −0.16 between 4.8 and 8.6 GHz to −0.28 between 8.6 and 20 GHz. 
 
 
 
Simultaneous observations in polarization are available for all the sources at all the frequencies. 768 sources have a good-quality detection of polarized flux density at 20 GHz; 467 of them were also detected in polarization at 4.8 and/or at 8.6 GHz so that it has been possible to compare the spectral behaviour in total intensity and polarization. We have found that the polarized fraction increases slightly with frequency and decreases with flux density. The spectral indices in total intensity and in polarization are, on average, close to each other, but we also found several sources for which the spectral shape of the polarized emission is substantially different from the spectral shape in total intensity. The correlation between the spectral indices in total intensity and in polarization is weaker for flat-spectrum sources. 
 
 
 
Cross-matches and comparisons have been made with other catalogues at lower radio frequencies, and in the optical, X-ray and γ-ray bands. Redshift estimates are available for 825 sources.
15407740
The Parkes quarter-Jansky flat-spectrum sample. 2. New optical spectra and redshift measurements
We present optical spectra and redshift measurements for 178 flat-spectrum objects from the Parkes quarter-Jansky flat-spectrum sample. These spectra were obtained in order to compile a complete sample of quasars for use in a study of quasar evolution. We present a composite optical spectrum made from the subset of 109 quasars that have flux densities in the range 0.25 Jy < S 2 . 7 G H z < 0.5 Jy, and make a comparison with a composite for radio-quiet QSOs from the Large Bright Quasar Survey. Our large sample of radio-loud quasars allows us to strengthen previous reports that the Lya and CIV emission lines have larger equivalent width in radio-loud quasars than radio-quiet QSOs to greater than the 3σ level. However we see no significant difference in the equivalent widths of CIII] or MgII. We also show that the flux decrements across the Lyman-α line (D A ) measured from these spectra show the same trend with redshift as for optically selected QSOs.