18278613
Search for axionlike particles using a variable-baseline photon-regeneration technique.
We report the first results of the GammeV experiment, a search for milli-eV mass particles with axionlike couplings to two photons. The search is performed using a "light shining through a wall" technique where incident photons oscillate into new weakly interacting particles that are able to pass through the wall and subsequently regenerate back into detectable photons. The oscillation baseline of the apparatus is variable, thus allowing probes of different values of particle mass. We find no excess of events above background and are able to constrain the two-photon couplings of possible new scalar (pseudoscalar) particles to be less than 3.1x10;(-7) GeV-1 (3.5x10;(-7) GeV-1) in the limit of massless particles.
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.
42455013
Results from the Cryogenic Dark Matter Search at Soudan Underground Laboratory
We present results from the Cryogenic Dark Matter Search at Soudan Underground Laboratory for two‐tower arrays of detector. Twelve detectors were operated from March 25 to August 8, 2004, or 74.5 detector live days. Within expected background, no statistically significant indication of a WIMP signal was observed. Based on this null observation and combined with our previous results, we exclude a spin‐averaged WIMP‐nucleon interaction cross section above 1.6 × 10−43 cm2 for Ge detectors, and 3 × 1042 cm2 for Si detectors, for a WIMP mass 60 GeV/c2 with 90%C.L. This result constrains parameter space of minimal supersymmetric standard models (MSSM) and starts to reach the parameter space of a constrained model (CMSSM).
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.
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.
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.
119269198
General Relativistic Description of the Observed Galaxy Power Spectrum: Do We Understand What We Measure?
We extend the general relativistic description of galaxy clustering developed in Yoo, Fitzpatrick, and Zaldarriaga (2009). For the first time we provide a fully general relativistic description of the observed matter power spectrum and the observed galaxy power spectrum with the linear bias ansatz. It is significantly different from the standard Newtonian description on large scales and especially its measurements on large scales can be misinterpreted as the detection of the primordial non-Gaussianity even in the absence thereof. The key difference in the observed galaxy power spectrum arises from the real-space matter fluctuation defined as the matter fluctuation at the hypersurface of the observed redshift. As opposed to the standard description, the shape of the observed galaxy power spectrum evolves in redshift, providing additional cosmological information. While the systematic errors in the standard Newtonian description are negligible in the current galaxy surveys at low redshift, correct general relativistic description is essential for understanding the galaxy power spectrum measurements on large scales in future surveys with redshift depth z ≥ 3. We discuss ways to improve the detection significance in the current galaxy surveys and comment on applications of our general relativistic formalism in future surveys.
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.
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.
119340160
Big bang nucleosynthesis and cosmic microwave background constraints on the time variation of the Higgs vacuum expectation value
We derive constraints on the time variation of the Higgs vacuum expectation value $ $ through the effects on Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB). In the former case, we include the (previously-neglected) effect of the change in the deuteron binding energy, which alters both the $^4$He and deuterium abundances significantly. We find that the current BBN limits on the relative change in \higgs are $-(0.6 - 0.7) \times 10^{-2} / < (1.5 - 2.0) \times 10^{-2}$, where the exact limits depend on the model we choose for the dependence of the deuteron binding energy on \higgs.The limits from the current CMB data are much weaker.
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.