15315
Results from the CDMS 5-Tower Operation
Astrophysical observations strongly suggest that non-luminous, nonbaryonic components, so called 'Dark Matter', may constitute most of the matter in the Universe. The Cryogenic Dark Matter Search (CDMS) experiment is designed to detect Dark Matter interaction events through nuclear recoils from elastic scattering. The detector is capable of reading out both phonon and ionization energy of an interaction in Ge or Si crystals. We present results from the CDMS five-tower detector arrays. The data were collected in the period between October 2006 and July 2007 (with an effective exposure of 121.3 kg-days). No WIMP signal was observed. The results, when combined with previous CDMS Soudan data, set a 90% confidence level upper bound on the WIMP-nucleon cross section of 4.6 x 10{sup -44} cm{sup 2} at 60 Gev/c{sup 2} WIMP mass.
18442902
Tracking Performance of the Scintillating Fiber Detector in the K2K Experiment
The K2K long-baseline neutrino oscillation experiment uses a Scintillating Fiber Detector (SciFi) to reconstruct charged particles produced in neutrino interactions in the near detector. We describe the track reconstruction algorithm and the performance of the SciFi after 3 years of operation.
118941632
Search for periodic modulations of the solar neutrino flux in Super-Kamiokande-I
A search for periodic modulations of the solar neutrino flux was performed using the Super-Kamiokande-I data taken from May 31st, 1996 to July 15th, 2001. The detector's capability of measuring the exact time of events, combined with a relatively high yield of solar neutrino events, allows a search for short-time variations in the observed flux. We employed the Lomb test to look for periodic modulations of the observed solar neutrino flux. The obtained periodogram is consistent with statistical fluctuation and no significant periodicity was found.
12327360
Search for chameleon particles using a photon-regeneration technique.
We report the first results from the GammeV search for chameleon particles, which may be created via photon-photon interactions within a strong magnetic field. Chameleons are hypothesized scalar fields that could explain the dark energy problem. We implement a novel technique to create and trap the reflective particles within a jar and to detect them later via their afterglow as they slowly convert back into photons. These measurements provide the first experimental constraints on the couplings of chameleons to photons.
119668802
A study of short-time periodic variation of the 8 B solar neutrino flux at Super-Kamiokande
Super-Kamiokande(SK) is a real-time detector capable of measuring the exact time of solar neutrino events. This, combined with a relatively high yield of these events of roughly 15 per day, allows a search for short-time variations in the observed flux. Using all 1496 days of SK-I’s solar data, we looked for periodic variations of the observed solar neutrino flux, and found no significant periodicity. The Lomb test was used to find possible periodicities in the measured fluxes of 10 day long samples.
125983626
Photon asymmetry and neutral current effect in bremsstrahlung
119005540
Halo Structures of Gravitational Lens Galaxies
We explore the halo structure of four gravitational lenses with well-observed, thin Einstein rings. We find that the gravitational potentials are well described by ellipsoidal density distributions in the sense that the best-fit nonellipsoidal models have parameters consistent with their ellipsoidal counterparts. We find upper limits on the standard parameters for the deviation from an ellipse of |a_3/a_0|<0.023, 0.019, 0.037, and 0.035, and |a_4/a_0|<0.034, 0.041, 0.051, and 0.064 for SDSS J0924+0219, HE0435-1223, B1938+666, and PG1115+080, respectively. We find that the lens galaxies are at the centers of their dark matter halos, and obtain upper limits for the offset of each center of mass from the center of light of |Delta x|<0.004, 0.005, 0.009, and 0.005 arcsec, corresponding to 22, 29, 70, and 23 pc. These limits also exclude the possibility of any significant lopsidednessof the dark matter halos and set an upper limit of f_sat<sqrt(N)% on the mass fraction of massive substructures inside the Einstein ring if they are divided over N satellites. We also explore the properties of galaxies as substructures in groups for the lens PG1115+080, finding evidence for dark matter halos associated with the galaxies but no evidence for a clear distinction between satellite and central galaxies.
118419164
Beyond the Linear-Order Relativistic Effect in Galaxy Clustering: Second-Order Gauge-Invariant Formalism
We present the second-order general relativistic description of the observed galaxy number density in a cosmological framework. The observed galaxy number density is affected by the volume and the source effects, both of which arise due to the mismatch between physical and observationally inferred quantities such as the redshift, the angular position, the volume, and the luminosity of the observed galaxies. These effects are computed to the second order in metric perturbations without choosing a gauge condition or adopting any restrictions on vector and tensor perturbations, extending the previous linear-order calculations. Paying particular attention to the second-order gauge transformation, we explicitly isolate unphysical gauge modes and construct second-order gauge-invariant variables. Moreover, by constructing second-order tetrads in the observer's rest frame, we clarify the relation between the physical and the parametrized photon wavevectors. Our second-order relativistic description will provide an essential tool for going beyond the power spectrum in the era of precision measurements of galaxy clustering. We discuss potential applications and extensions of the second-order relativistic description of galaxy clustering.
16668358
EXTENDING RECOVERY OF THE PRIMORDIAL MATTER POWER SPECTRUM
The shape of the primordial matter power spectrum encodes critical information on cosmological parameters. At large scales, in the linear regime, the observable galaxy power spectrum P obs(k) is expected to follow the shape of the linear matter power spectrum P lin(k), but on smaller scales the effects of nonlinearity and galaxy bias make the ratio P obs(k)/P lin(k) scale dependent. We develop a method that can extend the dynamic range of the primordial matter power spectrum recovery, taking full advantage of precision measurements on quasi-linear scales, by incorporating additional constraints on the galaxy halo occupation distribution (HOD) from the projected galaxy correlation function wp (rp ). We devise an analytic model to calculate observable galaxy power spectrum P obs(k) in real space and redshift space, given P lin(k) and HOD parameters, and we demonstrate its accuracy at the few percent level with tests against a suite of populated N-body simulations. Once HOD parameters are determined by fitting wp (rp ) measurements for a given cosmological model, galaxy bias is completely specified, and our analytic model predicts both the shape and normalization of P obs(k). Applying our method to the main galaxy redshift samples from the Sloan Digital Sky Survey (SDSS), we find that the real-space galaxy power spectrum follows the shape of the nonlinear matter power spectrum at the 1%-2% level up to k = 0.2 h Mpc–1 and that current observational uncertainties in HOD parameters leave only few percent uncertainties in our scale-dependent bias predictions up to k = 0.5 h Mpc–1. These uncertainties can be marginalized over in deriving cosmological parameter constraints, and they can be reduced by higher precision wp (rp ) measurements. When we apply our method to the SDSS luminous red galaxy (LRG) samples, we find that the linear bias approximation is accurate to 5% at k ≤ 0.08 h Mpc–1, but the strong scale dependence of LRG bias prevents the use of linear theory at k ≥ 0.08 h Mpc–1. Our HOD model prediction is in good agreement with the recent SDSS LRG power spectrum measurements at all measured scales (k ≤ 0.2 h Mpc–1), naturally explaining the observed shape of P obs(k) in the quasi-linear regime. The phenomenological "Q-model" prescription is a poor description of galaxy bias for the LRG samples, and it can lead to biased cosmological parameter estimates when measurements at k ≥ 0.1 h Mpc–1 are included in the analysis. We quantify the potential bias and constraints on cosmological parameters that arise from applying linear theory and Q-model fitting, and we demonstrate the utility of HOD modeling of high-precision measurements of P obs(k) on quasi-linear scales, which will be obtainable from the final SDSS data set.
51120946
Relativistic effects in galaxy clustering in a parametrized post-Friedmann universe
We explore the signatures of quintessence and modified gravity theories in the relativistic description of galaxy clustering within a parametrized post-Friedmann framework. For this purpose, we develop a calibration method to consistently account for horizon-scale effects in the linear parametrized post-Friedmann perturbations of minimally and nonminimally coupled scalar-tensor theories and test it against the full model-specific fluctuations. We further study the relativistic effects in galaxy clustering for the normal and self-accelerating branches of the Dvali-Gabadadze-Porrati braneworld model as well as for phenomenological modifications of gravity. We quantify the impact of modified gravity and dark energy models on galaxy clustering by computing the velocity-to-matter density ratio F , the velocity contribution R , and the potential contribution P and give an estimate of their detectability in future galaxy surveys. Our results show that, in general, the relativistic correction contains additional information on gravity and dark energy, which needs to be taken into account in consistent horizon-scale tests of departures from ΛCDM using the galaxy-density field.
847496
All-sky analysis of the general relativistic galaxy power spectrum
We perform an all-sky analysis of the general relativistic galaxy power spectrum using the well-developed spherical Fourier decomposition. Spherical Fourier analysis expresses the observed galaxy fluctuation in terms of the spherical harmonics and spherical Bessel functions that are angular and radial eigenfunctions of the Helmholtz equation, providing a natural orthogonal basis for all-sky analysis of the large-scale mode measurements. Accounting for all the relativistic effects in galaxy clustering, we compute the spherical power spectrum and its covariance matrix and compare it to the standard three-dimensional power spectrum to establish a connection. The spherical power spectrum recovers the three-dimensional power spectrum at each wave number k with its angular dependence μk encoded in angular multipole l, and the contributions of the line-of-sight projection to galaxy clustering such as the gravitational lensing effect can be readily accommodated in the spherical Fourier analysis. A complete list of formulas for computing the relativistic spherical galaxy power spectrum is also presented.