Showing papers by "T. J. Sumner published in 2005"

The DRIFT-II dark matter detector: Design and commissioning

Abstract: DRIFT-II is a second generation multi-module gaseous dark matter detector. Each module contains two time projection chambers positioned back-to-back inside a stainless steel vacuum vessel containing carbon disulphide gas. This paper describes the DRIFT-II detector modules and the commissioning work performed to date.

Muon-induced neutron production and detection with GEANT4 and FLUKA

Abstract: We report on a comparison study of the Monte Carlo packages GEANT4 and FLUKA for simulating neutron production by muons penetrating deep underground. GEANT4 is found to generate fewer neutrons at muon energies above ∼ 100 GeV , by at most a factor of 2 in some materials, which we attribute mainly to lower neutron production in hadronic cascades. As a practical case study, the muon-induced neutron background expected in a 250 kg liquid-xenon WIMP dark matter detector was calculated and good agreement was found for the recoil event rates. The detailed model of neutron elastic scattering in GEANT4 was also shown to influence the nuclear recoil spectrum observed in the target, which is presently a shortcoming of FLUKA. We conclude that both packages are suited for this type of simulation, although further improvements are desirable in both cases.

The icecube collaboration: contributions to the 29th international cosmic ray conference (icrc 2005), pune, india, aug. 2005

Abstract: The IceCube Collaboration: Contributions to the 29th International Cosmic Ray Conference (ICRC 2005), Pune, India, Aug. 2005

A mission to explore the pioneer anomaly

Abstract: The Pioneer 10 and 11 spacecraft yielded the mostprecise navigation in deep space to date. These spacecrafthad exceptional acceleration sensitivity. However, analysisof their radio-metric tracking data has consistently indi-cated that at heliocentric distances of ∼20–70 astronomi-cal units, the orbit determinations indicated the presenceof asmall, anomalous,Dopplerfrequency drift. The drift isa blue-shift, uniformly changing with a rate of ∼ (5.99 ±0.01) × 10 −9 Hz/s, which can be interpreted as a con-stant sunward acceleration of each particular spacecraftof a P = (8.74±1.33)×10 −10 m/s 2 (Anderson et al. 1998;Turyshev et al. 1999; Anderson et al. 2002a). The natureof this anomaly remains unexplained. This signal has be-come known as the Pioneer anomaly.The inability to explain the anomalous behavior ofthe Pioneers with conventional physics has contributedto growing discussion about its origin. There is now anincreasing number of proposals that attempt to explainthe anomaly outside conventional physics. This progressemphasizes the need for a new experiment to explore thedetected signal. Furthermore, the recent extensive effortsled to the conclusion that only a dedicated experimentcould ultimately determine the nature of the found signal.We discuss the Pioneer anomaly and present the nextsteps towards an understanding of its origin. We specifi-cally focus on the development of a mission to explore thePioneer Anomaly in a dedicated experiment conducted indeep space. This joint European-US mission is motivatedby the desire to better understand the laws of fundamen-tal physics as they affect dynamics in the solar system.The mission could lead to a major discovery in the 21stcentury and, with readily available technologies, it couldbe flown well within the Cosmic Vision time frame.Key words: Fundamental physics, Pioneer anomaly, solarsystem dynamics, deep space navigation, gravitation1. BackgroundThe exploration of the solar system’s frontiers - the regionbetween 25-250 astronomical units (AU) from the Sun -is a most ambitious and exciting technological challenge.The scientific goals for possible deep-space missions arewell-recognized and include studies of the gas and dustdistributions, exploration of the heliopause and the spacebeyond, measurements of the magnetic fields and particlefluxes, studies of the Oort Cloud and Kuiper Belt Objects,encounters with distant bodies, and investigation of thedynamical background of the solar system by studying

A study of the scintillation induced by alpha particles and gamma rays in liquid xenon in an electric field

Abstract: Scintillation produced in liquid xenon by alpha particles and gamma rays has been studied as a function of applied electric field. For back scattered gamma rays with energy of about 200 keV, the number of scintillation photons was found to decrease by 64±2% with increasing field strength. Consequently, the pulse shape discrimination power between alpha particles and gamma rays is found to reduce with increasing field, but remaining non-zero at higher fields.

On the Discovery of the First Galaxy Selected at 350 Microns

Abstract: We report the detection of a 36 σ source selected at 350 μm in the Bootes Deep Field The source, the first short-wavelength submillimeter-selected galaxy (SSG 1), was discovered as part of a blank-field extragalactic survey using the 350 μm-optimized Submillimeter High Angular Resolution Camera (SHARC II) at the Caltech Submillimeter Observatory With multiwavelength photometry from the NOAO Deep Wide-Field Survey (R and I band), FLAMEX (J and Ks), Spitzer (IRAC and MIPS), and the Westerbork 14 GHz deep survey (radio upper limit), we are able to constrain the photometric redshift using different methods, all of which suggest a redshift of ~1 In the absence of long-wavelength submillimeter data, we use SED templates to infer that this source is an ultraluminous infrared galaxy with a dust temperature of 30 ± 5 K, occupying a region of luminosity-temperature space shared by moderate-redshift ISO-selected ULIRGs (rather than high-redshift SCUBA-selected submillimeter galaxies) SHARC II can thus select galaxies with moderately "warm" dust that might be missed in submillimeter surveys at longer wavelengths

A Mission to Explore the Pioneer Anomaly

Abstract: The Pioneer 10 and 11 spacecraft yielded the most precise navigation in deep space to date. These spacecraft had exceptional acceleration sensitivity. However, analysis of their radio-metric tracking data has consistently indicated that at heliocentric distances of $\sim 20-70$ astronomical units, the orbit determinations indicated the presence of a small, anomalous, Doppler frequency drift. The drift is a blue-shift, uniformly changing with a rate of $\sim(5.99 \pm 0.01)\times 10^{-9}$ Hz/s, which can be interpreted as a constant sunward acceleration of each particular spacecraft of $a_P = (8.74 \pm 1.33)\times 10^{-10} {\rm m/s^2}$. This signal has become known as the Pioneer anomaly. The inability to explain the anomalous behavior of the Pioneers with conventional physics has contributed to growing discussion about its origin. There is now an increasing number of proposals that attempt to explain the anomaly outside conventional physics. This progress emphasizes the need for a new experiment to explore the detected signal. Furthermore, the recent extensive efforts led to the conclusion that only a dedicated experiment could ultimately determine the nature of the found signal. We discuss the Pioneer anomaly and present the next steps towards an understanding of its origin. We specifically focus on the development of a mission to explore the Pioneer Anomaly in a dedicated experiment conducted in deep space.

Coherent fourier components in the lisa measurement bandwidth from test mass charging: estimates and suppression

Abstract: The success of LISA is dependent on the precision with which the test masses, the interferometer mirrors, can maintain pure geodesic motion. Their accumulation of charge from cosmic rays and solar wind particles can give rise to spurious Lorentz and Coulomb forces. Coherent Fourier components, which appear due to the time dependence of the amount of charge accrued, are estimated to exceed the acceleration noise target. The general forms of these signals are derived. It is shown that for typical parameter values, coherent signals with significant signal-to-noise ratios can result from Coulomb interactions, while the signal from Lorentz interactions is expected to fall below the instrumental noise target. In this description, the signals' peak magnitudes are shown to increase with decreasing frequency. Hence their impact may be greater for missions that aim to look for gravitational waves at frequencies below the nominal LISA band. It is expected that the accuracy with which these signals can be removed from the data will depend on deviations from the predictable temporal behavior of the parameters on which they are dependent. Methods to substantially decrease these signals for LISA are discussed.

Fundamental physics with the laser astrometric test of relativity

Abstract: The Laser Astrometric Test of Relativity (LATOR) is an experiment designed to test the metric nature of gravitation—a fundamental postulate of the Einstein’s general theory of relativity. The key element of LATOR is a geometric redundancy provided by the long-baseline optical interferometry and interplanetary laser ranging. By using a combination of independent time-series of gravitational deflection of light in the immediate proximity to the Sun, along with measurements of the Shapiro time delay on interplanetary scales (to a precision respectively better than 0.1 picoradians and 1 cm), LATOR will significantly improve our knowledge of relativistic gravity and cosmology. The primary mission objective is i) to measure the key post-Newtonian Eddington parameter γ with accuracy of a part in 109. $\frac{1}{2}(1-\gamma)$ is a direct measure for presence of a new interaction in gravitational theory, and, in its search, LATOR goes a factor 30,000 beyond the present best result, Cassini’s 2003 test. Other mission objectives include: ii) first measurement of gravity’s non-linear effects on light to ∼0.01% accuracy; including both the traditional Eddington β parameter and also the spatial metric’s 2nd order potential contribution (never measured before); iii) direct measurement of the solar quadrupole moment J2 (currently unavailable) to accuracy of a part in 200 of its expected size of ≃ 10 − 7; iv) direct measurement of the “frame-dragging” effect on light due to the Sun’s rotational gravitomagnetic field, to 0.1% accuracy. LATOR’s primary measurement pushes to unprecedented accuracy the search for cosmologically relevant scalar-tensor theories of gravity by looking for a remnant scalar field in today’s solar system. We discuss the science objectives of the mission, its technology, mission and optical designs, as well as expected performance of this experiment. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could discover a violation or extension of general relativity and/or reveal the presence of an additional long range interaction in the physical law. There are no analogs to LATOR; it is unique and is a natural culmination of solar system gravity experiments.

On the discovery of the first 350 micron-selected galaxy

Abstract: We report the detection of a 3.6sigma 350micron-selected source in the Bootes Deep Field. The source, the first Short-wavelength Submillimeter-selected Galaxy (SSG 1), was discovered as part of a blank field extragalactic survey using the 350micron-optimised Submillimeter High Angular Resolution Camera (SHARC II) at the Caltech Submillimeter Observatory. With multiwavelength photometry from NOAO-NDWFS (R and I band), FLAMEX (J and K_s), Spitzer (IRAC and MIPS) and the Westerbork 1.4GHz Deep Survey (radio upper limit), we are able to constrain the photometric redshift using different methods, all of which suggest a redshift of close to 1. In the absence of long-wavelength submillimeter data we use SED templates to infer that this source is an ultraluminous infrared galaxy (ULIRG) with a dust temperature of 30+/-5 K, occupying a region of luminosity-temperature space shared by modarate redshift ISO-selected ULIRGs (rather than high redshift SCUBA-selected SMGs). SHARC II can thus select SMGs with moderately "warm'' dust that might be missed in submillimeter surveys at longer wavelengths.

Multi-messenger studies with amanda/icecube: observations and strategies

Abstract: Four years of AMANDA-II data have been searched for neutrinos from point sources. No statistically significant excess of events has been detected, neither integrated in the years 2000 to 2003, nor in the searches for occasional signals. An interesting coincidence of neutrinos with gamma-ray flares emerges when inspecting the time of the events detected from the direction of the Blazar 1ES1959+650. The exceptional character of the gamma-ray observation provides a strong motivation for consolidating similar search strategies with AMANDA and its successor IceCube, as well as for multidisciplinary investigations of this and other gamma-ray sources. We report the outcomes of the most recent survey of the northern sky to search for neutrino point sources with AMANDA-II. We also discuss possible viable collaborations between the gamma-ray and the high energy neutrino observatories.

First limits on nuclear recoil events from the ZEPLIN I galactic dark

Abstract: We report first results from the ZEPLIN I dark matter detector, based on measurement of scintillation pulse shapes in a liquid xenon target of 3.2 kg fiducial mass. Neutron calibration shows nuclear recoil pulses to have a time constant ≅ 0.5 that of gamma and beta background events. The detector is located in the 2800 mwe depth UK Boulby Mine, and is surrounded by a liquid scintillator Compton veto and passive lead shielding. Three runs totaling 293 kg d fiducial exposure yielded data consistent with a single population of background pulses, with no significant low energy population of shorter pulses. From the 90% confidence limit on the latter a limit is derived on the spin-independent WIMP-nucleon cross-section versus particle mass with a minimum at 1.1 × 10−6 pb.

Resolving IRAS 09111–1007 at 350 µm: a different path to ULIRG formation?

Abstract: We have resolved the ultraluminous infrared galaxy (ULIRG) IRAS 09111−1007 with the new 350-μm-optimized Second Generation Submillimeter High Angular Resolution Camera (SHARC II), and present the first submillimetre fluxes and images for the system. IRAS 09111−1007 comprises two interacting luminous infrared galaxies (LIRGs) with a projected nuclear separation of 39 h−171 kpc. The western galaxy is roughly four times more luminous in the submillimetre than its eastern counterpart. It is an extremely bright LIRG with an active galactic nucleus (AGN). The classification of the eastern source is uncertain: it could be a Seyfert 2 galaxy or a LINER. We highlight IRAS 09111−1007 as a system that necessitates further study: a double AGN ULIRG whose molecular gas content differs from that of other widely separated pairs, and whose ULIRG phase might not be explained by current multiple-merger and/or final-stage ULIRG scenarios.

Resolving IRAS 09111-1007 at 350 microns - a different path to ULIRG formation?

Abstract: We have resolved the ultraluminous infrared galaxy (ULIRG), IRAS 09111-1007, with the new 350 micron-optimised Second Generation Submillimeter High Angular Resolution Camera (SHARC II) and present the first submillimetre fluxes and images for the system. IRAS 09111-1007 comprises two interacting luminous infrared galaxies (LIRGs) with a projected nuclear separation of 39 kpc. The Western galaxy is roughly four times more luminous in the submillimetre than its Eastern counterpart. It is an extremely bright LIRG with an AGN. The classification of the Eastern source is uncertain: it could be a Seyfert 2 galaxy or a LINER. We highlight IRAS 09111-1007 as a system that necessitates further study: a double AGN ULIRG whose molecular gas content differs from other widely separated pairs and whose ULIRG phase might not be explained by current multiple merger and/or final stage ULIRG scenarios.

Fundamental Physics with the Laser Astrometric Test Of Relativity

Abstract: The Laser Astrometric Test Of Relativity (LATOR) is a joint European-U.S. Michelson-Morley-type experiment designed to test the pure tensor metric nature of gravitation - a fundamental postulate of Einstein's theory of general relativity. By using a combination of independent time-series of highly accurate gravitational deflection of light in the immediate proximity to the Sun, along with measurements of the Shapiro time delay on interplanetary scales (to a precision respectively better than 0.1 picoradians and 1 cm), LATOR will significantly improve our knowledge of relativistic gravity. The primary mission objective is to i) measure the key post-Newtonian Eddington parameter \gamma with accuracy of a part in 10^9. (1-\gamma) is a direct measure for presence of a new interaction in gravitational theory, and, in its search, LATOR goes a factor 30,000 beyond the present best result, Cassini's 2003 test. The mission will also provide: ii) first measurement of gravity's non-linear effects on light to ~0.01% accuracy; including both the Eddington \beta parameter and also the spatial metric's 2nd order potential contribution (never measured before); iii) direct measurement of the solar quadrupole moment J2 (currently unavailable) to accuracy of a part in 200 of its expected size; iv) direct measurement of the "frame-dragging" effect on light by the Sun's gravitomagnetic field, to 1% accuracy. LATOR's primary measurement pushes to unprecedented accuracy the search for cosmologically relevant scalar-tensor theories of gravity by looking for a remnant scalar field in today's solar system. We discuss the mission design of this proposed experiment.

Neutrino astronomy and cosmic rays at the south pole: latest results from amanda and perspectives for icecube

Abstract: The AMANDA neutrino telescope has been in operation at the South Pole since 1996. The present final array configuration, operational since 2000, consists of 677 photomultiplier tubes arranged in 19 strings, buried at depths between 1500 and 2000 m in the ice. The most recent results on a multi-year search for point sources of neutrinos will be shown. The study of events triggered in coincidence with the surface array SPASE and AMANDA provided a result on cosmic ray composition. Expected improvements from IceCube/IceTop will also be discussed.

Status of Zeplin II and Zeplin III

Abstract: We describe the ZEPLIN II (30-kg) and ZEPLIN III (7-kg) discriminating dark matter detector using two-phase xenon designed for direct detection of cold dark matter in the form of Weakly Interacting Massive Particles. These two detectors are currently being commissioned. Both detector will begin operation in the Boulby Mine, UK in 2005. ZEPLIN II & III are capable of discriminating between nuclear recoils and background events and have a design reach up to two orders of magnitude beyond current limits. These two detectors will also serve as a step in the development program for a next-generation ton-scale detector.