17078771
Phase‐space structure in the local dark matter distribution and its signature in direct detection experiments
We study predictions for dark matter phase-space structure near the Sun based on highresolution simulations of six galaxy halos taken from the Aquarius Project. The local DM density distribution is predicted to be remarkably smooth; the density at the Sun differs from the mean over a best-fit ellipsoidal equidensity contour by less than 15% at the 99.9% confidence level. The local velocity distribution is also very smooth, but it differs systematically from a (multivariate) Gaussian distribution. This is not due to th e presence of individual clumps or streams, but to broad features in the velocity modulus and energy distributions that are stable both in space and time and reflect the detailed assembly histo ry of each halo. These features have a significant impact on the signals predicted for WIMP an d axion searches. For example, WIMP recoil rates can deviate by � 10% from those expected from the best-fit multivariate Gaussian models. The axion spectra in our simulations typically peak at lower frequencies than in the case of multivariate Gaussian velocity distribu tions. Also in this case, the spectra show significant imprints of the formation of the halo. Th is implies that once direct DM detection has become routine, features in the detector sign al will allow us to study the dark matter assembly history of the Milky Way. A new field, “dark ma tter astronomy”, will then emerge.
119516023
Lattice SU(2) gauge-Higgs system in analytic treatment
The phase diagrams of SU(2) gauge-Higgs model with Higgs field of arbitrary length in the fundamental representation in four and five dimension are studied analytically. A method for determining phase transition lines is proposed. All qualitative features of the phase diagram obtained by Monte Carlo simulations are obtained analytically, and the order of phase transitions can be determined definitely.
121466004
Variational-cumulant expansion in lattice gauge theory☆
A variational method in the lagrangian formalism combined with a cumulant expansion of its order-by-order corrections is developed. The technique for dealing with the expansion is presented in a systematic way. As an example, the order parameter Ep ≡ 〈(1/N)trUp〉 for the SU(2) pure gauge Wilson model is evaluated to the 4th order correction in four and five dimensions and is in good agreement with the Monte Carlo results.
119239648
Substructure lensing: Effects of galaxies, globular clusters and satellite streams
Lensing flux-ratio anomalies have been frequently observed and taken as evidence for the presence of abundant dark matter substructures in lensing galaxies, as predicted by the cold dark matter (CDM) model of cosmogony. In previous work, we examined the cusp-caustic relations of the multiple images of background quasars lensed by galaxy-scale dark matter haloes, using a suite of high-resolution N-body simulations (the Aquarius simulations). In this work, we extend our previous calculations to incorporate both the baryonic and diffuse dark components in lensing haloes. We include in each lensing simulation: (1) a satellite galaxy population derived from a semi-analytic model applied to the Aquarius haloes; (2) an empirical Milky Way globular cluster population and (3) satellite streams (diffuse dark component) identified in the simulations. Accounting for these extra components, we confirm our earlier conclusion that the abundance of intrinsic substructures (dark or bright, bound or diffuse) is not sufficient to explain the observed frequency of cusp-caustic violations in the Cosmic Lens All-Sky Survey (CLASS). We conclude that the observed effect could be the result of the small number statistics of CLASS, or intergalactic haloes along the line of sight acting as additional sources of lensing flux anomalies. Another possibility is that this discrepancy signals a failure of the CDM model.
21769631
The population of Milky Way satellites in the LambdaCDM cosmology
We present a model for the satellites of the Milky Way in which galaxy formation is followed using semi-analytic techniques applied to the six high-resolution N-body simulations of galactic halos of the Aquarius project. The model, calculated using the Galform code, incorporates improved treatments of the relevant physics in the LambdaCDM cosmogony, particularly a self-consistent calculation of reionization by UV photons emitted by the forming galaxy population, including the progenitors of the central galaxy. Along the merger tree of each halo, the model calculates gas cooling (by Compton scattering off cosmic microwave background photons, molecular hydrogen and atomic processes), gas heating (from hydrogen photoionization and supernova energy), star formation and evolution. The evolution of the intergalactic medium is followed simultaneously with that of the galaxies. Star formation in the more massive progenitor subhalos is suppressed primarily by supernova feedback, while for smaller subhalos it is suppressed primarily by photoionization due to external and internal sources. The model is constrained to match a wide range of properties of the present day galaxy population as a whole, but at high redshift it requires an escape fraction of UV photons near unity in order completely to reionize the universe by redshift z ~ 8. In the most successful model the local sources photoionize the pre-galactic region completely by z ~ 10. In addition to the luminosity function of Milky Way satellites, the model matches their observed luminosity-metallicity relation, their radial distribution and the inferred values of the mass within 300 pc, which in the models increase slowly but significantly with luminosity. There is a large variation in satellite properties from halo to halo, with the luminosity function, for example, varying by a factor of ~ 2 among the six simulations.
124150385
Variational Treatment with the Third Order Corrections for SU(2) Lattice Gauge Theory
The variational method in Lagrangian formalism in lattice gauge theory in cumulant expansion is discussed. For SU(2) pure gauge Wi1son model to the third order corrections we show that there is no phase transition in four dimensions, but there exists the first order phase transition in five dimensions at βC=0.838 in agreement with the Monte Carlo results. The physical meaning of higher order corrections is discussed.
122332228
Alignment of the ATLAS inner detector
In order to reach the track parameter accuracy motivated by the physics goals of the experiment, the ATLAS tracking system needs to determine accurately its almost 700,000 degrees of freedom. The demanded precision for the alignment of the silicon sensors is below 10 μm. The implementation of the track based alignment within the ATLAS software framework unifies different alignment approaches and allows the alignment of all tracking subsystems together. The alignment software relies on the tracking information (track-hit residuals) but also includes the capability to set constraints on the beam-spot and primary vertex as well as the momentum measured by the Muon System or the E/p using the calorimetry information. The alignment chain starts at the trigger level where a stream of high pT isolated tracks is selected online. Also a cosmic ray trigger is enabled while ATLAS is recording collision data, thus a stream of cosmic-ray tracks is recorded exactly with the same detector operating conditions as the normal collision tracks. We will present results of the alignment of the ATLAS tracker using the 2011 collision data. The validation of the alignment is performed using track-hit residuals as well as using more advanced physics observables. The results of the alignment with real data reveals that the attained precision for the alignment parameters is approximately 5 μm.
16433217
The afterglows of ultraluminous quasars
Quasars represent a brief phase in the life cycle of most massive galaxies, but the evolutionary connection between central black holes and their host galaxies remains unclear. While quasars are active and shining brighter than the Compton-limit luminosity, their radiation heats the surrounding medium to the Compton temperature, forming Compton spheres extending to the Stromgren radius of Fe26+/He2+. After the quasars shut off, their "afterglow" can be detected through three signatures: (1) an extended X-ray envelope, with a characteristic temperature of ~3 × 107 K, (2) Lyα and Lyβ lines and the K edge of Fe26+, and (3) nebulosity from hydrogen and helium recombination emission lines. We discuss the possibility of detecting these signatures using Chandra, the planned X-Ray Evolving Universe Spectroscopy mission, and ground-based optical telescopes. The luminosity and size of quasar afterglows can be used to constrain the lifetime of quasars.
118458984
Next-to-leading order QCD predictions for the signal of dark matter and photon associated production at the LHC
We study the potential of the LHC to discover the signal of dark matter associated production with a photon induced by a dimension six effective operator, including next-to-leading order QCD corrections. We investigate the main backgrounds from the standard model, i.e. $Z$ boson and a photon associated production with invisible decay of $Z$ boson, and $Z$ boson and a jet production with the jet misidentified as a photon. We find that the ${p}_{T}^{\ensuremath{\gamma}}$ distributions of the backgrounds decrease faster than that of the signal with increasing of the transverse momentum of the photon. The ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$ distributions of the backgrounds are almost flat in the full range of ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$. In contrast, the signal lies mainly in the central region of ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$. These characteristics may help to select the events in experiments. We show that in the parameter space allowed by the relic abundance constraint, which we have calculated at the next-to-leading-order QCD level, the LHC with $\sqrt{S}=7\text{ }\text{ }\mathrm{TeV}$ may discover this signal at the $5\ensuremath{\sigma}$ level after collecting an integrated luminosity of $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. On the other hand, if this signal is not observed at the LHC, we can set a lower limit on the new physics scale at the $3\ensuremath{\sigma}$ level.
122330531
Search for dark matter and large extra dimensions in monojet events in pp collisions at $ \sqrt {s} = {7} $ TeV
A bstractA search has been made for events containing an energetic jet and an imbalance in transverse momentum using a data sample of pp collisions at a center-of-mass energy of 7 TeV. This signature is common to both dark matter and extra dimensions models. The data were collected by the CMS detector at the LHC and correspond to an integrated luminosity of 5.0 fb−1. The number of observed events is consistent with the standard model expectation. Constraints on the dark matter-nucleon scattering cross sections are determined for both spin-independent and spin-dependent interaction models. For the spin-independent model, these are the most constraining limits for a dark matter particle with mass below 3.5 GeV/c2, a region unexplored by direct detection experiments. For the spin-dependent model, these are the most stringent constraints over the 0.1–200 GeV/c2 mass range. The constraints on the Arkani-Hamed, Dimopoulos, and Dvali model parameter MD determined as a function of the number of extra dimensions are also an improvement over the previous results.
119112072
X-ray absorption variability in NGC 4507
We present a complete spectral analysis of an XMM-Newton and Chandra campaign of the obscured AGN in NGC 4507, consisting of six observations spanning a period of six months, ranging from June 2010 to December 2010. We detect strong absorption variability on time scales between 1.5 and 4 months, suggesting that the obscuring material consists of gas clouds at parsec-scale distance. The lack of significant variability on shorter time scales suggests that this event is not due to absorption by broad line region clouds, which was instead found in other studies of similar sources. This shows that a single, universal structure of the absorber (either BLR clouds, or the parsec-scale torus) is not enough to reproduce the observed complexity of the X-ray absorption features of this AGN.