119268605
An incremental approach to unravel the neutrino mass hierarchy and CP violation with a long-baseline superbeam for large θ13
A bstractRecent data from long-baseline neutrino oscillation experiments have provided new information on θ13, hinting that $ 0.0{1}\mathop{ < }\limits_{ \sim } {\text{si}}{{\text{n}}^{{2}}} $$ {2}{\theta_{{{13}}}}\mathop{ < }\limits_{ \sim } 0.{1} $ at 2 σ confidence level. In the near future, further confirmation of this result with high significance will have a crucial impact on the optimization of the future long-baseline neutrino oscillation experiments designed to probe the neutrino mass ordering and leptonic CP violation. In this context, we expound in detail the physics reach of an experimental setup where neutrinos produced in a conventional wide-band beam facility at CERN are observed in a proposed Giant Liquid Argon detector at the Pyhasalmi mine, at a distance of 2290 km. Due to the strong matter effects and the high detection efficiency at both the first and second oscillation maxima, this particular setup would have unprecedented sensitivity to the neutrino mass ordering and leptonic CP violation in the light of the emerging hints of large θ13. With a 10 to 20 kt ‘pilot’ detector and just a few years of neutrino beam running, the neutrino mass hierarchy could be determined, irrespective of the true values of δCP and the mass hierarchy, at 3 σ (5 σ) confidence level if sin2 2θ13(true) = 0.05 (0.1). With the same exposure, we start to have 3 σ sensitivity to CP violation if sin2 2θ13(true) > 0.05, in particular testing maximally CP-violating scenarios at a high confidence level. After optimizing the neutrino and anti-neutrino running fractions, we study the performance of the setup as a function of the exposure, identifying three milestones to have roughly 30%, 50% and 70% coverage in δC P (true) for 3 σ CP violation discovery. For comparison, we also study the CERN to Slanic baseline of 1540 km. This work nicely demonstrates that an incremental program, staged in terms of the exposure, can achieve the desired physics goals within a realistically feasible timescale, and produce significant new results at each stage.
118633851
Long-baseline super-beam experiments in Europe within LAGUNA
We explore the physics reach of several possible configurations for a Super-Beam experiment in Europe, focusing on the possibilities of discovering θ13, CP violation in the leptonic sector and the ordering of neutrino mass eigenstates. We consider the three different detector technologies: Water Cerenkov, Liquid Argon and Liquid Scintillator, and seven possible sites in Europe which would be able to host such a detector underground. The distances to these sites from CERN, where the beam would be originated, go from 130 km to 2300 km. The neutrino flux is optimized in each case as to match the first oscillation peak for each of the baselines under consideration. We also study the impact of several experimental factors in the performance of each detector technology.
118464873
A Comparative Study of Long-Baseline Superbeams within LAGUNA for large $\theta_{13}$
The Daya Bay and RENO experiments have recently observed a non-zero $\theta_{13}$ at more than $5\sigma$ CL. This has important consequences for future neutrino oscillation experiments. We analyze these within the LAGUNA design study which considers seven possible locations for a European neutrino observatory for proton decay, neutrino, and astroparticle physics. The megaton-scale detector would be an ideal target for a CERN-based neutrino beam with baselines ranging from 130 km to 2300 km. We perform a detailed study to assess the physics reach of the three detector options - a 440 kton water \v{C}erenkov, a 100 kton liquid argon and a 50 kton liquid scintillator detector - at each of the possible locations, taking into account the recent measurement of $\theta_{13}$. We study the impact of the beam properties and detector performances on the sensitivity to CP-violation and the mass hierarchy. We find that a liquid argon or water \v{C}erenkov detector can make a $3\sigma$ discovery of CP violation for $60%-70%$ of the parameter space for any of the baselines under consideration, although the results for the liquid argon detector placed at 130 km are slightly worse and only $40%-50%$ is achieved in this case. The performance of the liquid scintillator detector is affected by its level of neutral-current background at all baselines. A $3\sigma$ determination of the mass hierarchy is possible for all values of $\delta$, for the values of $\theta_{13}$ favoured at $3\sigma$ by Daya Bay and RENO, for almost all setups with $L\gtrsim 650$ km.
118358517
MODEL-INDEPENDENT DETERMINATION OF CURVATURE PARAMETER USING H(z) AND D-A (z) DATA PAIRS FROM BAO MEASUREMENTS
We present a model-independent determination of the curvature parameter Omega(k) using the Hubble parameter H(z) and the angular diameter distance D-A(z) from recent baryon acoustic oscillation (BAO) measurements. Each H(z) and D-A(z) pair from a BAO measurement can constrain a curvature parameter. The accuracy of the curvature measurement improves with increased redshift of H(z) and D-A(z) data. By using the H(z) and D-A(z) pair derived from a BAO Lyman a forest measurement at z = 2.36, the Omega(k) is confined to be -0.05 +/- 0.06, which is consistent with the curvature of -0.037(-0.042) (+0.044) constrained by the nine year Wilkinson Microwave Anisotropy Probe data only. Considering future BAOmeasurements, at least one order of magnitude improvement of this curvature measurement can be expected.
17819736
Statistical and systematical errors in cosmic microwave background maps
Sky temperature map of the cosmic microwave background (CMB) is one of the premier probes of cosmology. To minimize instrumentally induced systematic errors, CMB anisotropy experiments measure temperature differences across the sky using paires of horn antennas with a fixed separation angle, temperature maps are recovered from temperature differences obtained in sky survey through a map-making procedure. The instrument noise, inhomogeneities of the sky coverage and sky temperature inevitably produce statistical and systematical errors in recovered temperature maps. We show in this paper that observation-dependent noise and systematic temperature distortion contained in released Wilkinson Microwave Anisotropy Probe (WMAP) CMB maps are remarkable. These errors can contribute to large-scale anomalies detected in WMAP maps and distort the angular power spectrum as well. It is needed to remake temperature maps from original WMAP differential data with modified map-making procedure to avoid observation-dependent noise and systematic distortion in recovered maps.
121504005
HXMT: A Chinese High-Energy Astrophysics Mission
The Hard X-ray Modulation Telescope mission HXMT is mainly devoted to performing a hard X-ray all-sky imaging survey with both high sensitivity and high spatial resolution In the energy range of 20 - 250 keV HXMT can perform full-sky hard X-ray survey with angular resolution 5 prime position accuracy 1 prime and sensitivity better than Integral IBIS and Swift BAT HXMT can also make high signal-to-noise ratio pointing observations of scientific hot spot sources with sensitivity sim 3 0 times 10 -7 ph cm -2 s -1 keV -1 3 100keV 10 5 s for detailed temporal and spectral studies HXMT was selected in 2000 as a project under the Major State Basic Research Program of China for its feasibility and technical demonstration study and in October 2005 HXMT entered the full design phase and was listed as a candidate for the first dedicated astronomy satellite around 2010
772564
The Cross-spectra of Cir X−1: Evolution of Time Lags
Earlier work showed that the track in the X-ray hardness-intensity diagram of Cir X-1 corresponds to a Z track in its color-color diagram. In this paper, we study the cross spectrum of Cir X-1 in different regions of the hardness-intensity diagram with RXTE/PCA data. Comparing the light curves of Cir X-1 for the energy band 1.8-5.1 keV to those for 5.1-13.1 keV, we find that Cir X-1 exhibits a hard time lag on the horizontal branch, and a soft time lag on both the normal and the flaring branch. This indicates that Cir X-1 is similar to GX 5-1 and Cyg X-2 on the horizontal branch, but is different from them on the normal branch. We briefly discuss the mechanism of the time lags in the context of Comptonization models. Subject headings: binaries: general — stars: individual (Cir X-1) — X-rays: stars
119110521
LOW-FREQUENCY OSCILLATIONS IN XTE J1550–564
We present the results of a timing analysis of the low-frequency quasi-periodic oscillation (QPO) in the Rossi X-Ray Timing Explorer data of the black hole binary XTE J1550-564 during its 1998 outburst. The QPO frequency is observed to vary on timescales between {approx}100 s and days, correlated with the count rate contribution from the optically thick accretion disk: we studied this correlation and discuss its influence on the QPO width. In all observations, the quality factors ({nu}{sub 0}/FWHM) of the fundamental and second harmonic peaks were observed to be consistent, suggesting that the quasi-periodic nature of the oscillation is due to frequency modulation. In addition to the QPO and its harmonic peaks, a new 1.5{nu} component was detected in the power spectra. This component is broad, with a quality factor of {approx}0.6. From this, we argue that the peak observed at half the QPO frequency, usually referred to as 'sub-harmonic', could be the fundamental frequency, leading to the sequence 1:2:3:4. We also studied the energy dependence of the timing features and conclude that the two continuum components observed in the power spectrum, although both more intense at high energies, show a different dependence on energy. At low energies, the lowest-frequencymore » component dominates, while at high energies the higher-frequency one has a higher fractional rms. An interplay between these two components was also observed as a function of their characteristic frequency. In this source, the transition between the low/hard state and the hard-intermediate state appears to be a smooth process.« less