118523006
Modelling the clustering of dark matter haloes in resummed perturbation theories
We address the issue of the cosmological bias between matter and galaxy distributions, looking at dark matter haloes as a first step to characterize galaxy clustering. Starting from the linear density field at high redshift, we follow the centre-of-mass trajectory of the material that will form each halo at late times (protohalo). We adopt a fluid-like description for the evolution of perturbations in the protohalo distribution, which is coupled to the matter density field via gravity. We present analytical solutions for the density and velocity fields, in the context of renormalized perturbation theory. We start from the linear solution, then compute one-loop corrections for the propagator and the power spectrum. Finally, we analytically resum the propagator, and we use a suitable extension of the time-renormalization-group method to resum the power spectrum. For halo masses M < 1014 h−1 M⊙, our results at z= 0 are in good agreement with N-body simulations. Our model is able to predict the halo–matter cross-spectrum with an accuracy of 5 per cent up to k≈ 0.1 h Mpc−1 approaching the requirements of future galaxy redshift surveys.
119245317
Toward a public analysis database for LHC new physics searches using MADANALYSIS 5
We present the implementation, in the MadAnalysis 5 framework, of several ATLAS and CMS searches for supersymmetry in data recorded during the first run of the LHC. We provide extensive details on the validation of our implementations and propose to create a public analysis database within this framework.
91177292
SModelS: a tool for interpreting simplified-model results from the LHC and its application to supersymmetry
We present a general procedure to decompose Beyond the Standard Model (BSM) collider signatures presenting a $$\mathbb {Z}_2$$Z2 symmetry into Simplified Model Spectrum (SMS) topologies. Our method provides a way to cast BSM predictions for the LHC in a model independent framework, which can be directly confronted with the relevant experimental constraints. Our concrete implementation currently focusses on supersymmetry searches with missing energy, for which a large variety of SMS results from ATLAS and CMS are available. As show-case examples we apply our procedure to two scans of the minimal supersymmetric standard model. We discuss how the SMS limits constrain various particle masses and which regions of parameter space remain unchallenged by the current SMS interpretations of the LHC results.
118517610
Effective couplings approach to neutralino dark matter relic density
In this work, we analyze the electroweak loop corrections to the Neutralino dark matter relic density in the framework of effective coupling. In the first part, we comment on the generic features of the corrections and quantitative changes to the predicted relic density. We analyze the correlation between the characteristics of effective couplings to the nature of neutralino. Effective couplings, however, absorb only the most dominant one loop corrections and are not an exact calculation. In the second part, we assess the validity of effective couplings by comparing them to the full one loop calculations in various regions of parameter space.
119466873
The Radio and X-Ray-Luminous Type Ibc Supernova 2003L
We present extensive radio observations of SN 2003L, the most luminous and energetic Type Ibc radio supernova with the exception of SN 1998bw (associated with GRB 980425). Observations from the Very Large Array are well described by fitting a synchrotron self-absorption model to the emission spectrum. This model implies a subrelativistic ejecta velocity, ≈ 0.2c, and a size of r ≈ 4.3 × 1015 cm at t ≈ 10 days. The circumstellar density is suitably fitted with a stellar wind profile, ne ∝ r-2 cm-3 and a constant mass-loss rate of ≈ 7.5 × 10-6 M☉ yr-1. Moreover, the magnetic field follows B ∝ r-1 and the kinetic energy of the radio-bright ejecta is roughly E ≈ 1048 ergs assuming equipartition of energy between relativistic electrons and magnetic fields. Furthermore, we show that free-free absorption does not contribute significantly to the radio spectrum, since it implies ejecta velocities that are inconsistent with size constraints derived from Very Long Baseline Array observations. In conclusion, we find that although SN 2003L has a radio luminosity comparable to that seen in SN 1998bw, it shows no evidence for a significant amount of energy coupled to relativistic ejecta. Using SN 2003L as an example, we comment briefly on the coupling of ejecta velocity and energy in Type Ibc supernovae.
6132403
Millimeter Observations of GRB 030329: Continued Evidence for a Two-Component Jet
We present the results of a dedicated campaign on the afterglow of GRB 030329 with the millimeter interferometers of the Owens Valley Radio Observatory (OVRO) and the Berkeley-Illinois-Maryland Association (BIMA), and with the MAMBO-2 bolometer array on the IRAM 30 m telescope. These observations allow us to trace the full evolution of the afterglow of GRB 030329 at frequencies of 100 and 250 GHz for the first time. The millimeter light curves exhibit two main features: a bright, constant flux density portion and a steep power-law decline. The absence of bright, short-lived millimeter emission is used to show that the GRB central engine was not actively injecting energy well after the burst. The millimeter data support a model, advocated by Berger et al., of a two-component jetlike outflow in which a narrow-angle jet is responsible for the high-energy emission and early optical afterglow, and a wide-angle jet carrying most of the energy is powering the radio and late optical afterglow emission.
119017201
A luminous companion to SGR 1806-20
We have obtained infrared spectra of the star suggested to be the counterpart of the soft gamma-ray repeater (SGR) 1806-20. We found strong emission lines similar to those seen in the spectra of the rare luminous blue variables and B(e) stars. A He I absorption line is also seen, from which we infer a spectral type O9-B2. This classification, in combination with the minimum distance of greater than or approximately = 6 kpc inferred from its extinction, makes the star one of the most luminous in the Galaxy. We infer that it is a companion to SGR 1806-20 and suggest that the presence of a companion is somehow related to the SGR phenomenon.
15593768
The mass of a millisecond pulsar
We report on nearly 2 years of timing observations of the low-mass binary millisecond pulsar PSR J1909-3744 with the Caltech-Parkes-Swinburne Recorder II, a new instrument that gives unprecedented timing precision. Daily observations give a weighted rms residual of 74 ns, indicating an extremely low level of systematic error. We have greatly improved on the previous parallax and proper motion measurements of PSR J1909-3744, yielding a distance of 1.14 kpc and transverse velocity of 200 km s-1. The system's orbital eccentricity is just (1.35 ± 12) × 10-7, the smallest yet recorded. Since their discovery, the masses of the rapidly rotating millisecond pulsars have remained a mystery, with the recycling hypothesis arguing for heavy objects, and the accretion-induced collapse of a white dwarf more consistent with neutron stars less than the Chandrashkar limit. Fortuitously, PSR J1909-3744 is an edge-on system, and our data have allowed the measurement of the range and shape of the Shapiro delay to high accuracy, giving the first precise determination of a millisecond pulsar mass to date, mp = 1.438 ± 0.024 M☉. The mass of PSR J1909-3744 is at the upper edge of the range observed in mildly recycled pulsars in double neutron star systems, consistent with the recycling hypothesis. It appears that the production of millisecond pulsars is possible with the accretion of <0.2 M☉.
1819366
A Standard Kinetic Energy Reservoir in Gamma-Ray Burst Afterglows
We present a comprehensive sample of X-ray observations of 41 γ-ray burst (GRB) afterglows, as well as jet opening angles, θj, for a subset with measured jet breaks. We show that there is a significant dispersion in the X-ray fluxes, and hence isotropic X-ray luminosities (LX,iso), normalized to t = 10 hr. However, there is a strong correlation between LX,iso and the beaming fractions, fb ≡ [1 - cos(θj)]. As a result, the true X-ray luminosity of GRB afterglows, LX = fbLX,iso, is approximately constant, with a dispersion of only a factor of 2. Since eEb ∝ LX, the strong clustering of LX directly implies that the adiabatic blast wave kinetic energy in the afterglow phase, Eb, is tightly clustered. The narrow distribution of LX also suggests that p ≈ 2, that inverse Compton emission does not in general dominate the observed X-ray luminosity, and that radiative losses at t < 10 hr are relatively small. Thus, despite the large diversity in the observed properties of GRBs and their afterglows, the energy imparted by the GRB central engine to the relativistic ejecta is approximately constant.