17433293
Are mergers responsible for universal halo properties
N-body simulations of cold dark matter (CDM) have shown that, in this hierarchical structure formation model, dark matter halo properties, such as the density profile, the phase-space density profile, the distribution of axial ratio, the distribution of spin parameter and the distribution of internal specific angular momentum, follow 'universal' laws or distributions. Here, we study the properties of the first generation of haloes in a hot dark matter (HDM) dominated universe, as an example of halo formation through monolithic collapse. We find all these universalities to be present in this case also. Halo density profiles are very well fit by the Navarro, Frenk & White profile over two orders of magnitude in mass. The concentration parameter depends on mass as c α M 0.2 , reversing the dependence found in a hierarchical CDM universe. However, the concentration-formation time relation is similar in the two cases: earlier forming haloes tend to be more concentrated than their later forming counterparts. Halo formation histories are also characterized by two phases in the HDM case: an early phase of rapid accretion followed by slower growth. Furthermore, there is no significant difference between the HDM and CDM cases concerning the statistics of other halo properties: the phase-space density profile; the velocity anisotropy profile; the distribution of shape parameters; the distribution of spin parameter and the distribution of internal specific angular momentum are all similar in the two cases. Only substructure content differs dramatically. These results indicate that mergers do not play a pivotal role in establishing the universalities, thus contradicting models which explain them as consequences of mergers.
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.
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.
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.
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.
18867535
Clustering of Lyman alpha emitters at z ~ 4.5
We present the clustering properties of 151 Lyα-emitting galaxies at z ≈ 4.5 selected from the Large Area Lyman Alpha (LALA) survey. Our catalog covers an area of 36' × 36' observed with five narrowband filters. We assume that the angular correlation function w(θ) is well represented by a power law Awθ-β with slope β = 0.8, and we find Aw = 6.73 ± 1.80. We then calculate the correlation length r0 of the real-space two-point correlation function ξ(r) = (r/r0)-1.8 from Aw through the Limber transformation, assuming a flat, Λ-dominated universe. Neglecting contamination, we find r0 = 3.20 ± 0.42 h-1 Mpc. Taking into account a possible 28% contamination by randomly distributed sources, we find r0 = 4.61 ± 0.6 h-1 Mpc. We compare these results with the expectations for the clustering of dark matter halos at this redshift in a cold dark matter model, and find that the measured clustering strength can be reproduced if these objects reside in halos with a minimum mass of (1-2) × 1011 h-1 M☉. Our estimated correlation length implies a bias of b ~ 3.7, similar to that of Lyman break galaxies (LBGs) at z ~ 3.8-4.9. However, Lyα emitters are a factor of ~2-16 rarer than LBGs with a similar bias value and implied host halo mass. Therefore, one plausible scenario seems to be that Lyα emitters occupy host halos of roughly the same mass as LBGs, but shine with a relatively low duty cycle of 6%-50%.
209842367
Alignment of the CMS tracker with LHC and cosmic ray data
© CERN 2014 for the benefit of the CMS collaboration, published under the terms of the Creative Commons Attribution 3.0 License by IOP Publishing Ltd and Sissa Medialab srl. Any further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation and DOI.
111339244
Bonded wafer substrates for integrated detector arrays
Bonded wafer substrates that are optimized for integrating high-energy-particle silicon detector arrays with their readout electronics have been fabricated. The detectors are processed in the handle wafer, which is a 300- mu m-thick, high-resistivity, silicon wafer. This wafer is bonded to a primary wafer using a low-temperature process that does not affect the detector material. The support electronics are processed in the remnant of the primary wafer, which is a submicron-thick silicon film formed by a bond-and-etchback procedure. These two materials are isolated from each other by a radiation-hardened dielectric film. The integration process is based on a low-temperature, radiation-hardened VLSI CMOS process that is also shown not to seriously affect the detector material. >
56397085
Measurements of the T2K neutrino beam properties using the INGRID on-axis near detector
Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The normalized event rate is measured with 4% precision.
119093128
The role of the outer boundary condition in accretion disk models: Theory and application
In a previous paper, we find that the outer boundary conditions (OBCs) of an optically thin accretion flow play an important role in determining the structure of the flow. Here in this paper, we further investigate the influence of OBCs on the dynamics and radiation of the accretion how on a more detailed level. Bremsstrahlung and synchrotron radiations amplified by Comptonization are taken into account, and two-temperature plasma assumption is adopted. The three OBCs we adopted are the temperatures of the electrons and ions and the specific angular momentum of the accretion flow at a certain outer boundary. We investigate the individual role of each of the three OBCs on the dynamical structure and the emergent spectrum. We find that when the general parameters such as the mass accretion rate M and the viscous parameter alpha are fixed the peak flux at various bands such as radio, IR, and X-ray can differ by as much as several orders of magnitude under different OBCs in our example. Our results indicate that the OBC is both dynamically and radiatively important and therefore should be regarded as a new "parameter" in accretion disk models. As an illustrative example, we further apply the above results to the compact radio source Sgr A* located at the center of our Galaxy. The advection-dominated accretion flow (ADAF) model has turned out to be a great success in explaining its luminosity and spectrum. However, there exists a discrepancy between the mass accretion rate favored by ADAF models in the literature and that favored by the three-dimensional hydrodynamical simulation, with the former being 10-20 times smaller than the latter. By seriously considering the outer boundary condition of the accretion flow, we find that because of the low specific angular momentum of the accretion gas the accretion in Sgr A* should belong to a new accretion pattern, which is characterized by the possession of a very large sonic radius. This accretion pattern can significantly reduce the discrepancy between the mass accretion rates. We argue that the accretion occurred in some detached binary systems; the core of nearby elliptical galaxies and active galactic nuclei very possibly belongs to this accretion pattern.