17637923
A Complete Set of Solutions for Caustic Crossing Binary Microlensing Events
We present a method to analyze binary lens microlensing light curves with one well-sampled fold caustic crossing. In general, the surface of s2 shows extremely complicated behavior over the nine- parameter space that characterizes binary lenses. This makes it difficult to systematically search the space and verify that a given local minimum is a global minimum. We show that for events with well- monitored caustics, the caustic crossing region can be isolated from the rest of the light curve and easily —tted to a —ve-parameter function. Four of these caustic crossing parameters can then be used to con- strain the search in the larger nine-parameter space. This allows a systematic search for all solutions and thus identi—cation of all local minima. We illustrate this technique using the PLANET data for MACHO 98-SMC-1, an excellent and publicly available caustic crossing data set. We show that a very broad range of parameter combinations are compatible with the PLANET data set, demonstrating that observations of binary lens light curves with a sampling of only one caustic crossing do not yield unique solutions. The corollary to this is that the time of the second caustic crossing cannot be reliably predict- ed on the basis of early data including the —rst caustic crossing alone. We investigate the requirements for determination of a unique solution and —nd that occasional observations of the —rst caustic crossing may be sufficient to derive a complete solution. Subject headings: astrometrydark mattergravitational lensing
119493694
H alpha equivalent width variations across the face of a microlensed K giant in the galactic bulge
We present Very Large Telescope FORS1 spectroscopy that temporally resolves the second caustic crossing of the Galactic bulge K giant source of microlensing event EROS 2000-BLG-5, the first time this has been accomplished for several phases of a caustic transit. The similar to1 Angstrom H alpha equivalent width of the source star increases slightly as the center of the star egresses the caustic and then plummets by 30% during the final limb crossing. These changes are not seen in contemporaneous spectra of control stars in the FORS1 slit but are qualitatively consistent with expectations from stellar atmosphere models as the caustic differentially magnifies different portions of the stellar face of the target. Observations such as these in a variety of stellar lines are equivalent to atmospheric tomography and are expected to provide a direct test of stellar models.
16941683
Microlensing Constraints on the Frequency of Jupiter-Mass Companions: Analysis of 5 Years of PLANET Photometry
We analyze 5 years of PLANET photometry of microlensing events toward the Galactic bulge to search for the short-duration deviations from single-lens light curves that are indicative of the presence of planetary companions to the primary microlenses. Using strict event-selection criteria, we construct a well-defined sample of 43 intensively monitored events. We search for planetary perturbations in these events over a densely sampled region of parameter space spanning two decades in mass ratio and projected separation, but find no viable planetary candidates. By combining the detection efficiencies of the events, we find that, at 95% confidence, less than 25% of our primary lenses have companions with mass ratio q = 10-2 and separations in the lensing zone, [0.6-1.6]θE, where θE is the Einstein ring radius. Using a model of the mass, velocity, and spatial distribution of bulge lenses, we infer that the majority of our lenses are likely M dwarfs in the Galactic bulge. We conclude that less than 33% of M dwarfs in the Galactic bulge have companions with mass mp = MJ between 1.5 and 4 AU, and less than 45% have companions with mp = 3MJ between 1 and 7 AU, the first significant limits on planetary companions to M dwarfs. We consider the effects of the finite size of the source stars and changing our detection criterion, but find that these do not alter our conclusions substantially.
2974286
First microlens mass measurement: Planet photometry of EROS BLG-2000-5
We analyze PLANET photometric observations of the caustic-crossing binary lens microlensing event, EROS BLG-2000-5, and find that modeling the observed light curve requires incorporation of the microlens parallax and the binary orbital motion. The projected Einstein radius (E = 3.61 ± 0.11 AU) is derived from the measurement of the microlens parallax, and we are also able to infer the angular Einstein radius (θE = 1.38 ± 0.12 mas) from the finite source effect on the light curve, combined with an estimate of the angular size of the source given by the source position in a color-magnitude diagram. The lens mass, M = 0.612 ± 0.057 M☉, is found by combining these two quantities. This is the first time that parallax effects are detected for a caustic-crossing event and also the first time that the lens mass degeneracy has been completely broken through photometric monitoring alone. The combination of E and θE also allows us to conclude that the lens lies in the near side of the disk, within 2.6 kpc of the Sun, while the radial velocity measurement indicates that the source is a Galactic bulge giant.
55031010
Difference image analysis: extension to a spatially varying photometric scale factor and other considerations
We present a general framework for matching the point-spread function (PSF), photometric scaling and sky background between two images, a subject which is commonly referred to as difference image analysis (DIA). We introduce the new concept of a spatially varying photometric scale factor which will be important for DIA applied to wide-field imaging data in order to adapt to transparency and airmass variations across the field-of-view. Furthermore, we demonstrate how to separately control the degree of spatial variation of each kernel basis function, the photometric scale factor and the differential sky background. We discuss the common choices for kernel basis functions within our framework, and we introduce the mixed-resolution delta basis functions to address the problem of the size of the least-squares problem to be solved when using delta basis functions. We validate and demonstrate our algorithm on simulated and real data. We also describe a number of useful optimizations that may be capitalized on during the construction of the least-squares matrix and which have not been reported previously. We pay special attention to presenting a clear notation for the DIA equations which are set out in a way that will hopefully encourage developers to tackle the implementation of DIA software.
73625238
1318 new variable stars in a 0.25 square degree region of the Galactic plane
We conducted a deep photometric survey of a 0.5 ◦ × 0.5 ◦ area of the Galactic plane using the WFI instrument on the 2.2-m ESO telescope on La Silla, Chile. The dataset comprises a total of 267 R-band images, 204 from a 16 day observation run in 2005, supplemented by 63 images from a six week period in 2002. Our reduction employed the new numerical kernel difference image analysis method as implemented in the pysis3 code and resulted in more than 500 000 lightcurves of stars down to a magnitude limit of R ∼ 24.5. A search for variable stars resulted in the detection of 1318 variables of different types. 1011 of these are eclipsing or contact binary stars. A number of the contact binaries have low mass-ratios and several of the detached binaries appear to have low-mass components. Three candidate contact binaries have periods at the known cut off including two with periods lower than any previously published. Also identified are 3 possible pre-main sequence detached eclipsing binaries.
121849522
The design and calibration of precision drift chambers for use in a gluonium search experiment at the CERN ISR
We describe the design, construction and calibration of a set of high precision drift chambers. The precise coordinate (σ ∼ 120 μm) is determined by drift time measurement, with the orthogonal coordinate given by the charge division method (σ∼1.2 mm). The chambers have been calibrated using a well-defined laser beam. Their use within a gluonium search experiment at the CERN ISR is also described.
116427383
Photodetector timing research at Fermilab
Author(s): Ramberg, E; Ronzhin, A; Albrow, M; Los, S; Pranko, A; Malik, S; Zatserklyaniy, A | Abstract: We describe here the outlines of research undertaken by Fermilab into timing characteristics of photodetectors. We describe our experimental method and give benchtop results on the timing resolution of micro-channel plate photomultipliers (MCP-PMT) and silicon photomultipliers (SiPM). In addition, we describe results of various configurations of these detectors, along with quartz radiators, in particle test beams at Fermilab. Results for timing of scintillator light using the DRS4 high speed digitizer are also presented.
120843344
FP420: An R&D proposal to investigate the feasibility of installing proton tagging detectors in the 420-m region at LHC
The physics potential of forward proton tagging in the 420m region at the LHC has only been fully appreciated within the last few years. By detecting protons that have lost less than 1% of their longitudinal momentum, a rich QCD, electroweak, Higgs and BSM program becomes accessible, with the potential to make measurements which are unique at LHC, and difficult even at a future linear collider. By tagging both outgoing protons at 420m in the process pp → p + X + p, the LHC is effectively turned into a glue-glue collider. Initially, this will open up a rich, high-rate diffractive and QCD physics menu, allowing the study of the off-diagonal un-integrated gluon densities of the proton, rapidity gap survival (and therefore underlying event), and providing a source of almost pure gluon jets. In the few-fb-1 luminosity range, a new field of high-energy photon physics opens up, giving access to precision studies of the quartic gauge couplings, anomalous W or Z pair production and, at higher luminosities, supersymmetric particle pair production in an extremely clean environment. As the delivered luminosity reaches 10?s of fb-1, the double-tagged ?central exclusive? production process becomes a tool to search for new physics, delivering signal to background ratios greater than unity for Standard Model (SM) Higgs production, more than an order of magnitude larger for certain supersymmetric (MSSM) scenarios. It can provide a clear determination of the Higgs quantum numbers and excellent mass resolution, which may be necessary to resolve a nearly degenerate Higgs sector. It also offers a unique probe (at least until a linear collider) of the CP structure of the Higgs sector, through azimuthal asymmetry measurements of the tagged protons or detailed analysis of the missing mass lineshape. In addition to Higgs physics, 420m proton tagging provides an opportunity to investigate the entire strong interaction sector of physics within and beyond the Standard Model, from the production of heavy hadron resonances to gluinonia and radions. In pA collisions, the precision study of ultra-peripheral heavy ion collisions will be possible. The 15m drift spaces around 420m from the ATLAS and CMS interaction points offer a physics opportunity that is not exploited in the current LHC physics programme. Protons that lose between 10-3 and 10-2 of their initial momenta emerge from the beams in these regions, which we propose to instrument in the FP420 project. In doing so, we will access a broad range of low-x hard QCD processes, and the central mass range of 115 GeV and upwards which is required for Higgs and discovery physics. This region is at present enclosed in a 'connection cryostat' which maintains a series of superconducting bus-bars, and the beam pipes themselves, at a temperature of 1.7K. A prerequisite for the FP420 project is to assess the feasibility of replacing the 420m interconnection cryostat to facilitate access to the beam pipes and therefore allow proton tagging detectors to be installed. Our intention is to initiate an R&D project based at CERN in collaboration with the UK Cockcroft Institute for Accelerator Science, with the AT/CRI group, the TS/LEA group and with the institutes named on this proposal to provide a feasibility study and conceptual design for the instrumentation of the 420m region. The first opportunity to install such detectors would be the planned LHC shutdown in autumn 2008. Such a physics program cannot be carried out with short runs at high-beta optics, (and consequently low luminosity), but will need the high statistics provided by standard, high luminosity running. The UK groups on this proposal have been awarded 100k pounds of ?seed-corn? money in FY 05 / 06 to support initial design studies. We would like to ask the LHCC to take note of this LOI and its physics goals, and endorse the proposed R&D program.
122957735
Central exclusive production issue: Introduction
I give a brief introduction to central exclusive production in hadron–hadron collisions, the subject of this special issue of the International Journal of Modern Physics A.
120358369
The spectrum of protons produced in pp collisions at 31 GeV total energy
Data are reported on the distributions in longitudinal and transverse momentum of protons produced in the range 0.5 < x < 1.0 (x = Feynman variable) and 0.2 < pT2 < 1.8 (GeV/c)2 in proton-proton collisions at 31 GeV c.m. energy at the CERN ISR. The invariant inelastic cross section shows a peak at high longitudinal momenta. The shape of this peak suggests substantial production of states with masses up to at least 7 GeV.