arXiv subjects

D. Smith

Publications and source records attributed to D. Smith.

At least 73 records · Page 4Linked to original sources

arXiv2012

Herschel-ATLAS: towards a sample of ~1000 strongly-lensed galaxies

While the selection of strongly lensed galaxies with 500μm flux density S_500>100 mJy has proven to be rather straightforward (Negrello et al. 2010), for many applications it is important to analyze samples larger than the ones obtained when confining ourselves to such a bright limit. Moreover, only by probing to fainter flux densities is possible to exploit strong lensing to investigate the bulk of the high-z star-forming galaxy population. We describe HALOS (the Herschel-ATLAS Lensed Objects Selection), a method for efficiently selecting fainter candidate strongly lensed galaxies, reaching a surface density of ~1.5-2 deg^-2, i.e. a factor of about 4 to 6 higher than that at the 100 mJy flux limit. HALOS will allow the selection of up to ~1000 candidate strongly lensed galaxies (with amplifications μ>2) over the full H-ATLAS survey area. Applying HALOS to the H-ATLAS Science Demonstration Phase field (~14.4 deg^2) we find 31 candidate strongly lensed galaxies, whose candidate lenses are identified in the VIKING near-infrared catalog. Using the available information on candidate sources and candidate lenses we tentatively estimate a ~72% purity of the sample. The redshift distribution of the candidate lensed sources is close to that reported for most previous surveys for lensed galaxies, while that of candidate lenses extends to substantially higher redshifts than found in the other surveys. The counts of candidate strongly lensed galaxies are also in good agreement with model predictions (Lapi et al. 2011). Even though a key ingredient of the method is the deep near-infrared VIKING photometry, we show that H-ATLAS data alone allow the selection of a similarly deep sample of candidate strongly lensed galaxies with an efficiency close to 50%; a slightly lower surface density (~1.45 deg^-2) can be reached with a ~70% efficiency.

astro-ph.CO↗

arXiv2011

Search for the Rare Decays KL->pi0pi0mu+mu- and KL->pi0pi0X0->pi0pi0mu+mu-

The KTeV E799 experiment has conducted a search for the rare decays KL->pi0pi0mu+mu- and KL->pi0pi0X0->pi0pi0mu+mu-, where the X0 is a possible new neutral boson that was reported by the HyperCP experiment with a mass of (214.3 pm 0.5) MeV/c^{2}. We find no evidence for either decay. We obtain upper limits of Br(KL->pi0pi0X0->pi0pi0mu+mu-) < 1.0 x 10^{-10} and Br(KL->pi0pi0mu+mu-) < 9.2 x 10^{-11} at the 90% confidence level. This result rules out the pseudoscalar X0 as an explanation of the HyperCP result under the scenario that the \bar{d}sX0 coupling is completely real.

hep-ex↗

arXiv2011

Observation of H2O in a strongly lensed Herschel-ATLAS source at z=2.3

The Herschel survey, H-ATLAS, with its large areal coverage, has recently discovered a number of bright, strongly lensed high-z submillimeter galaxies. The strong magnification makes it possible to study molecular species other than CO, which are otherwise difficult to observe in high-z galaxies. Among the lensed galaxies already identified by H-ATLAS, the source J090302.9-014127B (SDP.17b) at z = 2.305 is remarkable due to its excitation conditions and a tentative detection of the H2O 202-111 emission line (Lupu et al. 2010). We report observations of this line in SDP.17b using the IRAM interferometer equipped with its new 277- 371GHz receivers. The H2O line is detected at a redshift of z = 2.3049+/-0.0006, with a flux of 7.8+/-0.5 Jy km s-1 and a FWHM of 250+/-60 km s-1. The new flux is 2.4 times weaker than the previous tentative detection, although both remain marginally consistent within 1.6-sigma. The intrinsic line luminosity and ratio of H2O(202-111)/CO8-7 seem comparable with those of the nearby starburst/enshrouded-AGN Mrk 231, suggesting that SDP.17b could also host a luminous AGN. The detection of a strong H2O 202-111 line in SDP.17b implies an efficient excitation mechanism of the water levels that must occur in very dense and warm interstellar gas.

astro-ph.CO↗

arXiv2011

Herschel-ATLAS: Rapid evolution of dust in galaxies in the last 5 billion years

We present the first direct and unbiased measurement of the evolution of the dust mass function of galaxies over the past 5 billion years of cosmic history using data from the Science Demonstration Phase of the Herschel-ATLAS. The sample consists of galaxies selected at 250μm which have reliable counterparts from SDSS at z < 0.5, and contains 1867 sources. Dust masses are calculated using both a single temperature grey-body model for the spectral energy distribution and also using a model with multiple temperature components. The dust temperature for either model shows no trend with redshift. Splitting the sample into bins of redshift reveals a strong evolution in the dust properties of the most massive galaxies. At z = 0.4 - 0.5, massive galaxies had dust masses about five times larger than in the local Universe. At the same time, the dust-to-stellar mass ratio was about 3-4 times larger, and the optical depth derived from fitting the UV-sub-mm data with an energy balance model was also higher. This increase in the dust content of massive galaxies at high redshift is difficult to explain using standard dust evolution models and requires a rapid gas consumption timescale together with either a more top-heavy IMF, efficient mantle growth, less dust destruction or combinations of all three. This evolution in dust mass is likely to be associated with a change in overall ISM mass, and points to an enhanced supply of fuel for star formation at earlier cosmic epochs.

astro-ph.CO↗

arXiv2011

Measurement of Neutrino-Induced Charged-Current Charged Pion Production Cross Sections on Mineral Oil at E$_ν\sim 1~\textrm{GeV}$

Using a high-statistics, high-purity sample of $ν_μ$-induced charged current, charged pion events in mineral oil (CH$_2$), MiniBooNE reports a collection of interaction cross sections for this process. This includes measurements of the CC$π^+$ cross section as a function of neutrino energy, as well as flux-averaged single- and double-differential cross sections of the energy and direction of both the final-state muon and pion. In addition, each of the single-differential cross sections are extracted as a function of neutrino energy to decouple the shape of the MiniBooNE energy spectrum from the results. In many cases, these cross sections are the first time such quantities have been measured on a nuclear target and in the 1 GeV energy range.

hep-ex↗

arXiv2011

Measurement of $ν_μ$-induced charged-current neutral pion production cross sections on mineral oil at $E_ν\in0.5-2.0$ GeV

Using a custom 3 Čerenkov-ring fitter, we report cross sections for $ν_μ$-induced charged-current single $π^0$ production on mineral oil (\chtwo) from a sample of 5810 candidate events with 57% signal purity over an energy range of $0.5-2.0$GeV. This includes measurements of the absolute total cross section as a function of neutrino energy, and flux-averaged differential cross sections measured in terms of $Q^2$, $μ^-$ kinematics, and $π^0$ kinematics. The sample yields a flux-averaged total cross section of $(9.2\pm0.3_{stat.}\pm1.5_{syst.})\times10^{-39}$cm$^2$/CH$_2$ at mean neutrino energy of 0.965GeV.

hep-ex↗

arXiv2010

Precise Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System

We present precise tests of CP and CPT symmetry based on the full dataset of K to pipi decays collected by the KTeV experiment at Fermi National Accelerator Laboratory during 1996, 1997, and 1999. This dataset contains 16 million K to 2pi0 and 69 million K to pi+pi- decays. We measure the direct CP violation parameter Re(epsilon'/epsilon) = (19.2 pm 2.1)x10-4. We find the KL-KS mass difference Deltam = (5270 pm 12)x10^6 hbar/s and the KS lifetime tauS = (89.62 pm 0.05)x10-12 s. We also measure several parameters that test CPT invariance. We find the difference between the phase of the indirect CP violation parameter, epsilon, and the superweak phase, phi_epsilon - phi_SW = (0.40 pm 0.56) degrees. We measure the difference of the relative phases between the CP violating and CP conserving decay amplitudes for K to pi+pi- (phi+-) and for K to 2pi0 (phi00), Delta phi = (0.30 pm 0.35) degrees. From these phase measurements, we place a limit on the mass difference between K0 and K0bar, DeltaM < 4.8 x 10-19 GeV/c^2 at 95% C.L. These results are consistent with those of other experiments, our own earlier measurements, and CPT symmetry.

hep-ex↗

arXiv2010

H-ATLAS: PACS imaging for the Science Demonstration Phase

We describe the reduction of data taken with the PACS instrument on board the Herschel Space Observatory in the Science Demonstration Phase of the Herschel-ATLAS (H-ATLAS) survey, specifically data obtained for a 4x4-deg^2 region using Herschel's fast-scan (60 arcsec/s) parallel mode. We describe in detail a pipeline for data reduction using customised procedures within HIPE from data retrieval to the production of science-quality images. We found that the standard procedure for removing Cosmic-Ray glitches also removed parts of bright sources and so implemented an effective two-stage process to minimise these problems. The pronounced 1/f noise is removed from the timelines using 3.4- and 2.5-arcmin boxcar high-pass filters at 100 and 160-um. Empirical measurements of the point-spread function (PSF) are used to determine the encircled energy fraction as a function of aperture size. For the 100- and 160-um bands, the effective PSFs are ~9 and ~13 arcsec (FWHM), and the 90-per-cent encircled energy radii are 13 and 18 arcsec. Astrometric accuracy is good to ~<2 arcsec. The noise in the final maps is correlated between neighbouring pixels and rather higher than advertised prior to launch. For a pair of cross-scans, the 5-sigma point-source sensitivities are 125-165 mJy for 9-13-arcsec radius apertures at 100-um and 150-240 mJy for 13-18-arcsec radius apertures at 160-um.

astro-ph.IM↗

arXiv2010

First Measurement of the Muon Neutrino Charged Current Quasielastic Double Differential Cross Section

A high-statistics sample of charged-current muon neutrino scattering events collected with the MiniBooNE experiment is analyzed to extract the first measurement of the double differential cross section ($\frac{d^2σ}{dT_μd\cosθ_μ}$) for charged-current quasielastic (CCQE) scattering on carbon. This result features minimal model dependence and provides the most complete information on this process to date. With the assumption of CCQE scattering, the absolute cross section as a function of neutrino energy ($σ[E_ν]$) and the single differential cross section ($\frac{dσ}{dQ^2}$) are extracted to facilitate comparison with previous measurements. These quantities may be used to characterize an effective axial-vector form factor of the nucleon and to improve the modeling of low-energy neutrino interactions on nuclear targets. The results are relevant for experiments searching for neutrino oscillations.

hep-ex↗

arXiv2010

Photomultiplier Tubes in the MiniBooNE Experiment

The detector for the MiniBooNE experiment at the Fermi National Accelerator Laboratory employs 1520 8 inch Hamamatsu models R1408 and R5912 photomultiplier tubes with custom-designed bases. Tests were performed to determine the dark rate, charge and timing resolutions, double-pulsing rate, and desired operating voltage for each tube, so that the tubes could be sorted for optimal placement in the detector. Seven phototubes were tested to find the angular dependence of their response. After the Super-K phototube implosion accident, an analysis was performed to determine the risk of a similar accident with MiniBooNE.

physics.ins-det↗

arXiv2010

The Third US Naval Observatory CCD Astrograph Catalog (UCAC3)

The third US Naval Observatory (USNO) CCD Astrograph Catalog, UCAC3 was released at the IAU General Assembly on 2009 August 10. It is the first all-sky release in this series and contains just over 100 million objects, about 95 million of them with proper motions, covering about R = 8 to 16 magnitudes. Current epoch positions are obtained from the observations with the 20 cm aperture USNO Astrograph's "red lens", equipped with a 4k by 4k CCD. Proper motions are derived by combining these observations with over 140 ground- and space-based catalogs, including Hipparcos/Tycho and the AC2000.2, as well as unpublished measures of over 5000 plates from other astrographs. For most of the faint stars in the Southern Hemisphere the Yale/San Juan first epoch plates from the SPM program (YSJ1) form the basis for proper motions. These data are supplemented by all-sky Schmidt plate survey astrometry and photometry obtained from the SuperCOSMOS project, as well as 2MASS near-IR photometry. Major differences of UCAC3 data as compared to UCAC2 include a completely new raw data reduction with improved control over systematic errors in positions, significantly improved photometry, slightly deeper limiting magnitude, coverage of the north pole region, greater completeness by inclusion of double stars and weak detections. This of course leads to a catalog which is not as "clean" as UCAC2 and problem areas are outlined for the user in this paper. The positional accuracy of stars in UCAC3 is about 15 to 100 mas per coordinate, depending on magnitude, while the errors in proper motions range from 1 to 10 mas/yr depending on magnitude and observing history, with a significant improvement over UCAC2 achieved due to the re-reduced SPM data and inclusion of more astrograph plate data unavailable at the time of UCAC2.

astro-ph.IM↗

arXiv2010

Measurement of ν_μand \barν_μinduced neutral current single $π^0$ production cross sections on mineral oil at E_νO(1 GeV)

MiniBooNE reports the first absolute cross sections for neutral current single π^0 production on CH_2 induced by neutrino and antineutrino interactions measured from the largest sets of NC π^0 events collected to date. The principal result consists of differential cross sections measured as functions of π^0 momentum and π^0 angle averaged over the neutrino flux at MiniBooNE. We find total cross sections of (4.76+/-0.05_{stat}+/-0.76_{sys})*10^{-40} cm^2/nucleon at a mean energy of =808 MeV and (1.48+/-0.05_{stat}+/-0.23_{sys})*10^{-40} cm^2/nucleon at a mean energy of =664 MeV for ν_μand \barν_μinduced production, respectively. In addition, we have included measurements of the neutrino and antineutrino total cross sections for incoherent exclusive NC 1π^0 production corrected for the effects of final state interactions to compare to prior results.

hep-ex↗

arXiv2009

A Letter of Intent to Build a MiniBooNE Near Detector: BooNE

There is accumulating evidence for a difference between neutrino and antineutrino oscillations at the $\sim 1$ eV$^2$ scale. The MiniBooNE experiment observes an unexplained excess of electron-like events at low energies in neutrino mode, which may be due, for example, to either a neutral current radiative interaction, sterile neutrino decay, or to neutrino oscillations involving sterile neutrinos and which may be related to the LSND signal. No excess of electron-like events ($-0.5 \pm 7.8 \pm 8.7$), however, is observed so far at low energies in antineutrino mode. Furthermore, global 3+1 and 3+2 sterile neutrino fits to the world neutrino and antineutrino data suggest a difference between neutrinos and antineutrinos with significant ($\sin^22θ_{μμ} \sim 35%$) $\bar ν_μ$ disappearance. In order to test whether the low-energy excess is due to neutrino oscillations and whether there is a difference between $ν_μ$ and $\bar ν_μ$ disappearance, we propose building a second MiniBooNE detector at (or moving the existing MiniBooNE detector to) a distance of $\sim 200$ m from the Booster Neutrino Beam (BNB) production target. With identical detectors at different distances, most of the systematic errors will cancel when taking a ratio of events in the two detectors, as the neutrino flux varies as $1/r^2$ to a calculable approximation. This will allow sensitive tests of oscillations for both $ν_e$ and $\bar ν_e$ appearance and $ν_μ$ and $\bar ν_μ$ disappearance. Furthermore, a comparison between oscillations in neutrino mode and antineutrino mode will allow a sensitive search for CP and CPT violation in the lepton sector at short baseline ($Δm^2 > 0.1$ eV$^2$).

hep-ex↗

arXiv2009

First Measurement of $ν_μ$ and $ν_e$ Events in an Off-Axis Horn-Focused Neutrino Beam

We report the first observation of off-axis neutrino interactions in the MiniBooNE detector from the NuMI beamline at Fermilab. The MiniBooNE detector is located 745 m from the NuMI production target, at 110 mrad angle ($6.3^{\circ}$) with respect to the NuMI beam axis. Samples of charged current quasi-elastic $ν_μ$ and $ν_e$ interactions are analyzed and found to be in agreement with expectation. This provides a direct verification of the expected pion and kaon contributions to the neutrino flux and validates the modeling of the NuMI off-axis beam.

hep-ex↗

arXiv2009

Scintillator counters with WLS fiber/MPPC readout for the side muon range detector (SMRD)of the T2K experiment

The T2K neutrino experiment at J-PARC uses a set of near detectors to measure the properties of an unoscillated neutrino beam and neutrino interaction cross-sections. One of the sub-detectors of the near-detector complex, the side muon range detector (SMRD), is described in the paper. The detector is designed to help measure the neutrino energy spectrum, to identify background and to calibrate the other detectors. The active elements of the SMRD consist of 0.7 cm thick extruded scintillator slabs inserted into air gaps of the UA1 magnet yokes. The readout of each scintillator slab is provided through a single WLS fiber embedded into a serpentine shaped groove. Two Hamamatsu multi-pixel avalanche photodiodes (MPPC's) are coupled to both ends of the WLS fiber. This design allows us to achieve a high MIP detection efficiency of greater than 99%. A light yield of 25-50 p.e./MIP, a time resolution of about 1 ns and a spatial resolution along the slab better than 10 cm were obtained for the SMRD counters.

physics.ins-det↗

arXiv2009

Measurement of the ν_μcharged current π^+ to quasi-elastic cross section ratio on mineral oil in a 0.8 GeV neutrino beam

Using high statistics samples of charged current $ν_μ$ interactions, MiniBooNE reports a measurement of the single charged pion production to quasi-elastic cross section ratio on mineral oil (CH$_2$), both with and without corrections for hadron re-interactions in the target nucleus. The result is provided as a function of neutrino energy in the range 0.4 GeV $< E_ν<$ 2.4 GeV with 11% precision in the region of highest statistics. The results are consistent with previous measurements and the prediction from historical neutrino calculations.

hep-ex↗

arXiv2009

Random planar graphs and the London street network

In this paper we analyse the street network of London both in its primary and dual representation. To understand its properties, we consider three idealised models based on a grid, a static random planar graph and a growing random planar graph. Comparing the models and the street network, we find that the streets of London form a self-organising system whose growth is characterised by a strict interaction between the metrical and informational space. In particular, a principle of least effort appears to create a balance between the physical and the mental effort required to navigate the city.

physics.data-an↗

arXiv2008

Search for the Rare Decay K_{L}\toπ^{0}π^{0}γ

The KTeV E799 experiment has conducted a search for the rare decay $K_{L}\toπ^{0}π^{0}γ$ via the topology $K_{L}\toπ^{0}π^{0}_Dγ$ (where $π^0_D\toγe^+e^-$). Due to Bose statistics of the $π^0$ pair and the real nature of the photon, the $K_{L}\toπ^{0}π^{0}γ$ decay is restricted to proceed at lowest order by the CP conserving direct emission (DE) of an E2 electric quadrupole photon. The rate of this decay is interesting theoretically since chiral perturbation theory predicts that this process vanishes at level $O(p^4)$. Therefore, this mode probes chiral perturbation theory at $O(p^6)$. In this paper we report a determination of an upper limit of $2.43\times 10^{-7}$ (90% CL) for $K_{L}\toπ^{0}π^{0}γ$. This is approximately a factor of 20 lower than previous results.

hep-ex↗