We measure shifts of the acoustic scale due to nonlinear growth and redshift distortions to a high precision using a very large volume of high-force-resolution simulations. We compare results from various sets of simulations that differ in their force, volume, and mass resolution. We find a consistency within 1.5 − σ for shift values from different simulations and derive shift α(z) − 1 = (0.300 ± 0.015)%[D(z)/D(0)] 2 using our fiducial set. We find a strong correlation with a non-unity slope between shifts in real space and in redshift space and a weak correlation between the initial redshift and low redshift. Density-field reconstruction not only removes the mean shifts and reduces errors on the mean, but also tightens the correlations. After reconstruction, we recover a slope of near unity for the correlation between the real and redshift space and restore a strong correlation between the initial and the low redshifts. We derive propagators and mode-coupling terms from our N-body simulations and compare with the Zel'dovich approximation and the shifts measured from the χ 2 fitting, respectively. We interpret the propagator and the mode-coupling term of a nonlinear density field in the context of an average and a dispersion of its complex Fourier coefficients relative to those of the linear density field; from these two terms, we derive a signal-to-noise ratio of the acoustic peak measurement. We attempt to improve our reconstruction method by implementing 2LPT and iterative operations, but we obtain little improvement. The Fisher matrix estimates of uncertainty in the acoustic scale is tested using 5000h −3 Gpc 3 of cosmological PM simulations from Takahashi et al. (2009a). At an expected sample variance level of 1%, the agreement between the Fisher matrix estimates based on and the N-body results is better than 10 %. Subject headings: distance scale-large-scale structure of universe -methods: numerical

The baryon acoustic oscillation (BAO) feature in the clustering of matter in the universe serves as a robust standard ruler and hence can be used to map the expansion history of the universe. We use high force resolution simulations to analyze the effects of galaxy bias on the measurements of the BAO signal. We apply a variety of Halo Occupation Distributions (HODs) and produce biased mass tracers to mimic different galaxy populations. We investigate whether galaxy bias changes the nonlinear shifts on the acoustic scale relative to the underlying dark matter distribution presented by Seo et al. For the less biased HOD models (b < 3), we do not detect any shift in the acoustic scale relative to the no-bias case, typically 0.10% ± 0.10%. However, the most biased HOD models (b > 3) show a shift at moderate significance (0.79% ± 0.31% for the most extreme case). We test the one-step reconstruction technique introduced by Eisenstein et al. in the case of realistic galaxy bias and shot noise. The reconstruction scheme increases the correlation between the initial and final (z = 1) density fields, achieving an equivalent level of correlation at nearly twice the wavenumber after reconstruction. Reconstruction reduces the shifts and errors on the shifts. We find that after reconstruction the shifts from the galaxy cases and the dark matter case are consistent with each other and with no shift. The 1σ systematic errors on the distance measurements inferred from our BAO measurements with various HODs after reconstruction are about 0.07%-0.15%.

We introduce a new statistic ω ℓ (r s ) for measuring and analyzing large-scale structure and particularly the baryon acoustic oscillations. ω ℓ (r s ) is a band-filtered, configuration space statistic that is easily implemented and has advantages over the traditional power spectrum and correlation function estimators. Unlike these estimators, ω ℓ (r s ) can localize most of the acoustic information into a single dip at the acoustic scale while also avoiding sensitivity to the poorly constrained large scale power (i.e., the integral constraint) through the use of a localized and compensated filter. It is also sensitive to anisotropic clustering through pair counting and does not require any binning of data. We measure the shift in the acoustic peak due to nonlinear effects using the monopole ω 0 (r s ) derived from subsampled dark matter catalogues as well as from mock galaxy catalogues created via halo occupation distribution (HOD) modeling. All of these are drawn from 44 realizations of 1024 3 particle dark matter simulations in a 1h −1 Gpc box at z=1. We compare these shifts with those obtained from the power spectrum and conclude that the results agree. We therefore expect that distance measurements obtained from ω 0 (r s ) and P (k) will be consistent with each other. We also show that it is possible to extract the same amount of acoustic information by fitting over a finite range using either ω 0 (r s ) or P (k) derived from equal volume surveys. Subject headings: distance scale -cosmological parameters -large-scale structure of universecosmology: theory

Searches for supersymmetry at the Large Hadron Collider (LHC) have significantly constrained the parameter space associated with colored superpartners, whereas the constraints on color-singlet superpartners are considerably less severe. In this study, we investigate the dependence of slepton decay branching fractions on the nature of the lightest supersymmetric particle (LSP). In particular, in the Higgsino-like LSP scenarios, both decay branching fractions of˜ L andν depend strongly on the sign and value of M 1 /M 2 , which has strong implications for the reach of dilepton plus / E T searches for slepton pair production. We extend the experimental results for same flavor, opposite sign dilepton plus / E T searches at the 8 TeV LHC to various LSP scenarios. We find that the LHC bounds on sleptons are strongly enhanced for a non-Bino-like LSP: the 95% C.L. limit for m˜ L extends from 300 GeV for a Bino-like LSP to about 370 GeV for a Wino-like LSP. The bound for˜ L with a Higgsino-like LSP is the strongest (∼ 490 GeV) for M 1 /M 2 ∼ − tan 2 θ W and is the weakest (∼ 220 GeV) for M 1 /M 2 ∼ tan 2 θ W . We also calculate prospective slepton search reaches at the 14 TeV LHC. With 100 fb −1 integrated luminosity, the projected 95% C.L. mass reach for the left-handed slepton varies from 550 (670) GeV for a Bino-like (Winolike) LSP to 900 (390) GeV for a Higgsino-like LSP under the most optimistic (pessimistic) scenario. The reach for the right-handed slepton is about 440 GeV. The corresponding 5σ discovery sensitivity is about 100 GeV smaller. For 300 fb −1 integrated luminosity, the reach is about 50 − 100 GeV higher.

Current searches for the top squark mostly focus on the decay channels of t 1 → tχ 0 1 ort 1 → bχ ± 1 → bW χ 0 1 , leading to tt/bbW W + E T final states for top squark pair production at the LHC. In supersymmetric scenarios with light gauginos other than the neutralino lightest supersymmetric particle (LSP), different decay modes of the top squark could be dominant, which significantly weaken the current top squark search limits at the LHC. Additionally, new decay modes offer alternative discovery channels for top squark searches. In this paper, we study the top squark and bottom squark decay in the Bino-like LSP case with light Wino or Higgsino next-to-LSPs (NLSPs), and identify cases in which additional decay modes become dominant. We also perform a collider analysis for top squark pair production with mixed top squark decay final states oft 1 → tχ 0 2 → thχ 0 1 , t 1 → bχ ± 1 → bW χ 0 1 , leading to the bbbbjj + E T collider signature. The branching fraction for such decay varies between 25% and 50% for a top squark mass larger than 500 GeV with M 2 = M 1 + 150 GeV. At the 14 TeV LHC with 300 fb −1 integrated luminosity, the top squark can be excluded up to about 1040 GeV at the 95% C.L., or be discovered up to 940 GeV at 5σ significance.