120848886
SOME EXPERIMENTAL CONSIDERATIONS OF THE QCD GROUP
For experimental investigation of quantum chromodynamics, the preferred machine question is dominated by such issues as how much luminosity is needed and which machine is practical (to get approved, build fast, run reliably, etc.). It is concluded that pile-up problems for localized E/sub T/ triggers are not serious. For high luminosity QCD studies a philosophy is envisaged which is predominantly calorimetric and ignores the low p/sub t/ activity. It is suggested that consideration be given to the concept of a jet spectrometer for jet fragmentation with momentum measurement. (LEW)
59382161
QCD subgroup on diffractive and forward physics
Over the last few years, there has been a resurgence of interest in small-x or diffractive physics. This has been due to the realization that perturbative QCD techniques may be applicable to what was previously thought of as a non-perturbative problem and to the opening up of new energy regimes at HERA and the Tevatron collider. The goal is to understand the pomeron, and hence the behavior of total cross sections, elastic scattering and diffractive excitation, in terms of the underlying theory, QCD. This paper is divided into experiments of hadron-hadron colliders and electron-proton colliders.
118601539
Quartz Cherenkov counters for fast timing: QUARTIC
We have developed particle detectors based on fused silica (quartz) Cherenkov radi- ators read out with microchannel plate photomultipliers (MCP-PMTs) or silicon photomultipliers (SiPMs) for high precision timing (st 10-15 ps). One application is to measure the times of small angle protons from exclusive reactions, p+ p! p+ X + p, at the Large Hadron Collider, LHC. They may also be used to measure directional particle fluxes close to external or stored beams. The detectors have small areas (cm 2 ), but need to be active very close ( 4 mm) to the intense LHC beam, and so must be radiation hard and nearly edgeless. We present results of tests of detectors with quartz bars inclined at the Cherenkov angle, and with bars in the form of an "L" (with a 90 corner). We also describe a possible design for a fast timing hodoscope with few mm 2 elements.
115609427
VIIth Blois Workshop summary: experimental
The Blois Workshop has become a conference not just restricted to diffractive scattering, but including topics such as searches for SUSY and Higgs, measurements of the top mass and b-decays. I will mention these briefly but will mostly discuss new results (and needed future measurements) in hard diffraction at HERA and the Tevatron.
126196482
ELASTIC SCATTERING OF POSITIVE KAONS ON POLARIZED PROTONS BETWEEN 0.87 AND 2.74 GeV/c. RESULTS AND PHASE-SHIFT ANALYSIS.
Abstract Polarization and differential cross-section data at 16 momenta between 0.86 and 2.74 GeV/ c are presented. (Preliminary data on some of the momenta have been published earlier.) In an energy-independent phase-shift analysis from threshold up to 2.5 GeV/ c , resonant-like as well as non-resonant solutions are found for the P 3 wave. An helicity flip-non-flip decomposition of the partial waves partly supports the indications found in the analyses of other reactions that the pomeron is built up mainly from s -channel helicity non-flip contributions.
82550552
Search for stable particles of charge 1 and mass deuteron mass
In a search for stable massive particles of charge q ⩾ 1 at the CERN ISR (√s = 53 GeV) no new particle in the mass range q × 2.4 GeV < m ≲ 30 GeV has been found among 3.1 × 107 recorded secondaries. At x = 2pL/√s = 0.21 and pT = 0.21 GeV/c the deuteron to π+ ratio is (1.3±0.2) × 10−4 and the antideuteron to π− ratio is (7.6±2.3) × 10−6. for (anti)tritons upper limits of (t/π+) < 5 × 10−7and (t/π−7) < 5 × 10−7 have been obtained.
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.
15669528
Planet II: A Microlensing and Transit Search for Extrasolar Planets
Due to their extremely small luminosity compared to the stars they orbit, planets outside our own Solar System are extraordinarily difficult to detect directly in optical light. Careful photometric monitoring of distant stars, however, can reveal the presence of exoplanets via the microlensing or eclipsing effects they induce. The international PLANET collaboration is performing such monitoring using a cadre of semi-dedicated telescopes around the world. Their results constrain the number of gas giants orbiting 1–7 AU from the most typical stars in the Galaxy. Upgrades in the program are opening regions of “exoplanet discovery space” – toward smaller masses and larger orbital radii – that are inaccessible to the Doppler velocity technique. 1. Looking for Exoplanets through the Lens of Gravity The Doppler velocity technique, which measures the small to and fro motion induced in a parent star by an orbiting planet, has clearly demonstrated that several percent of solar-type stars have planets very unlike those in the Solar System (Marcy, Cochran & Mayor 2000). Known extrasolar planets are plotted with the nine Solar System planets in Figure 1. With the exception of the few bodies orbiting dead stellar cores known as pulsars, exoplanets discovered
119441536
Early estimation of microlensing event magnifications
Gravitational microlensing events with high peak magnifications provide a much-enhanced sensitivity to the detection of planets around the lens star. However, estimates of peak magnification during the early stages of an event by means of χ2 minimization frequently involve an overprediction, making observing campaigns with strategies that rely on these predictions inefficient. I show that a rudimentary Bayesian formulation, incorporating the known statistical characteristics of a detection system, produces much more accurate predictions of peak magnification than χ2 minimization. Implementation of this system will allow efficient follow-up observing programs that focus solely on events that contribute to planetary abundance statistics.
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.
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