122100550
Time of flight measurements with hadronic showers
Abstract We have measured the time resolutions which can be obtained in hadronic showers from a scintillation counter hodoscope and a scintillating fibre counter at various shower depths. The hodoscope was made of 100×2×1 cm 3 BICRON 404 scintillators. The fiber counter consisted of four layers of fibers (SCSN-38, 1 mm diameter) embedded in lead with the dimensions 100×20×1 cm 3 . The performance of these counters was compared for two different types of photomultipliers: Hamamatsu R2083 and Philips XP2020.
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.
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.
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.
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.
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.
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
118388048
Simulating the role of stellar rotation in the spectroscopic effects of differential limb magnification
Finite-source effects of gravitationally microlensed stars have been well discussed in the literature, but the role that stellar rotation plays has been neglected. A differential magnification map applied to a differentially Doppler-shifted surface alters the profiles of absorption lines, compromising their ordinarily symmetric nature. Herein, we assess the degree to which this finite-source effect of differential limb magnification (DLM), in combination with stellar rotation, alters spectroscopically derived stellar properties. To achieve this, we simulated a grid of high-magnification microlensing events using synthetic spectra. Our analysis shows that rotation of the source generates differences in the measured equivalent widths of absorption lines supplementary to DLM alone, but only of the order of a few percent. Using the wings of H alpha from the same simulated data, we confirmed the result of Johnson et al. (2010) that DLM alters measurements of effective temperature by < 100 K for dwarf stars, while showing rotation to bear no additional effect.
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.
16391684
A short, nonplanetary, microlensing anomaly: Observations and light-curve analysis of MACHO 99-BLG-47
We analyze PLANET and MACHO observations of MACHO 99-BLG-47, the first nearly normal microlensing event for which high signal-to-noise ratio data reveal a well-covered, short-duration anomaly. This anomaly occurs near the peak of the event. Short-duration anomalies near the peak of otherwise normal events are expected to arise both from extreme-separation (either very close or very wide), roughly equalmass binary lenses and from planetary systems. We show that the lens of MACHO 99-BLG-47 is in fact an extreme-separation binary, not a planetary system, thus demonstrating for the first time that these two important classes of events can be distinguished in practice. However, we find that the wide-binary and closebinary lens solutions fit the data equally well and cannot be distinguished even at D� 2 ¼ 1. This degeneracy is qualitatively much more severe than the one identified for MACHO 98-SMC-1 because the present degeneracy spans two rather than one dimension in the magnification field and does not require significantly different blending fractions. In the Appendix, we explore this result and show that it is related to the symmetry in the lens equation. Subject headings: binaries: general — gravitational lensing — planetary systems
15769177
Limits on Stellar and Planetary Companions in Microlensing Event OGLE-1998-BUL-14
We present the PLANET photometric data set for OGLE-1998-BUL-14, a high-magnification (A(max) similar to 16) event alerted by the OGLE collaboration toward the Galactic bulge in 1998. The PLANET data set consists a total of 461 I-band and 139 V-band points, the majority of which was taken over a 3 month period. The median sampling interval during this period is about 1 hr,and the I sigma scatter over the peak of the event is 1.5%. The excellent data quality and high maximum magnification of this event make it a prime candidate to search for the short-duration, low-amplitude perturbations that are signatures of a planetary companion orbiting the primary lens. The observed light curve for OGLE-1998-BUL-14 is consistent with a single lens (no companion) within photometric uncertainties. We calculate the detection efficiency of the light curve to lensing companions as a function of the mass ratio and angular separation of the two components. We find that companions of mass ratio greater than or equal to 0.01 are ruled out at the 95% significance level for projected separations between 0.4 and 2.4r(E), where r(E) is the Einstein ring radius of the primary lens. Assuming that the primary is a G dwarf with r(E) similar to 3 AU, our detection efficiency for this event is similar to 60% for a companion with the mass and separation of Jupiter and similar to 5% for a companion with the mass and separation of Saturn. Our efficiencies for planets like those around nu And and 14 Her are >75%.