14412863
First Results From The Taiwanese-American Occultation Survey (TAOS)
Results from the first 2 years of data from the Taiwanese-American Occultation Survey (TAOS) are presented. Stars have been monitored photometrically at 4 or 5 Hz to search for occultations by small (~3 km) Kuiper Belt objects (KBOs). No statistically significant events were found, allowing us to present an upper bound to the size distribution of KBOs with diameters 0.5 km < D < 28 km.
120203589
Electromagnetic calorimeter with thin gap wire chambers
In this paper we report about the experimental results obtained in a beam test of a gas sampling EM calorimeter. The module consists of 20 thin gap (30 mm) multiwire chambers as active elements, interleaved with brass absorber plates of 12 mm thickness or 0.84 radiation length. The KEK electron beam was tuned to energies of 0.5, 1.0, 2.0, 3.0, 4.0 GeV. The construction and performances of the chamber, the assembling of the module, the experimental setup and data acquisition system are briefly described. The energy resolution of the module is found to be 25%√E (E in GeV). In the range of measured energies, good linearity of the energy response is obtained. The longitudinal development of EM shower, the relation between energy resolution and thickness of the absorber as well as the high voltage of the chamber are studied. The effect of incident position of the beam on the performance of the module is also given.
43173006
The TAOS Project: Statistical Analysis of Multi-Telescope Time Series Data
The Taiwanese-American Occultation Survey (TAOS) monitors fields of up to ~1000 stars at 5 Hz simultaneously with four small telescopes to detect occultation events from small (~1 km) Kuiper Belt Objects (KBOs). The survey presents a number of challenges, in particular the fact that the occultation events we are searching for are extremely rare and are typically manifested as slight flux drops for only one or two consecutive time series measurements. We have developed a statistical analysis technique to search the multi-telescope data set for simultaneous flux drops which provides a robust false-positive rejection and calculation of event significance. In this article, we describe in detail this statistical technique and its application to the TAOS data set.
12981394
A Close Binary Star Resolved from Occultation by 87 Sylvia
The star BD +29 1748 was resolved to be a close binary from its occultation by the asteroid 87 Sylvia on 2006 December 18 UT. Four telescopes were used to observe this event at two sites separated by some 80 km. Two flux drops were observed at one site, whereas only one flux drop was detected at the other. From the long-term variation of Sylvia, we inferred the probable shape of the shadow during the occultation, and this in turn constrains the binary parameters: the two components of BD +29 1748 have a projected separation of 0:097-0:140 on the sky with a position angle 104°-110°. The asteroid was clearly resolved, with a size scale ranging from 130 to 290 km as projected onto the occultation direction, consistent with the size dimensions 385 × 265 × 230 km, mea- sured by direct adaptive optics imaging. No occultation was detected for either of the two known moonlets of 87 Sylvia.
37988677
Development of Measurement and Transverse Feedback System at HLS
In order to cure and damp coupled bunch (CB) instabilities caused by the high order modes (HOMs) of the RF cavity and the resistive wall impedance of the Ring vacuum chamber. HOMs are ineluctable during the operation of the accelerator. An observer system characterized by bunch by bunch measurement of transverse β oscillation and longitudinal synchrotron phase oscillation has been constructed and commissioned at Hefei Light Source (HLS) [1, 2]. A transverse bunch-by-bunch feedback system is under construction. The design and development of the observe systems, as well as diagnostics results of machine instabilities are presented in this paper.
55082285
GRB 071112C: A Case Study of Different Mechanisms in X-ray and Optical Temporal Evolution
We present a study on GRB 071112C X-ray and optical light curves. In these two wavelength ranges, we have found different temporal properties. The R-band light curve showed an initial rise followed by a single power-law decay, while the X-ray light curve was described by a single power-law decay plus a flare-like feature. Our analysis shows that the observed temporal evolution cannot be described by the external shock model in which the X-ray and optical emission are produced by the same emission mechanism. No significant color changes in multi-band light curves and a reasonable value of the initial Lorentz factor ({Gamma}{sub 0} = 275 {+-} 20) in a uniform interstellar medium support the afterglow onset scenario as the correct interpretation for the early R band rise. The result suggests that the optical flux is dominated by afterglow. Our further investigations show that the X-ray flux could be created by an additional feature related to energy injection and X-ray afterglow. Different theoretical interpretations indicate the additional feature in X-ray can be explained by either late internal dissipation or local inverse-Compton scattering in the external shock.
35757948
Search for very light CP-odd Higgs Boson in radiative decays of Upsilon(1S).
We search for a non-SM-like CP-odd Higgs boson (a(1)(0)) decaying to tau(+)tau(-) or mu(+)mu(-) in radiative decays of the Upsilon(1S). No significant signal is found, and upper limits on the product branching ratios are set. Our tau(+)tau(-) results are almost 2 orders of magnitude more stringent than previous upper limits. Our data provide no evidence for a Higgs state with a mass of 214 MeV decaying to mu(+)mu(-), previously proposed as an explanation for 3 Sigma(+)-->pmu(+)mu(-) events observed by the HyperCP experiment. Our results constrain NMSSM models.
118646182
Roadmap for selected key measurements of LHCb
Six of the key physics measurements that will be made by the LHCb experiment, concerning CP asymmetries and rare B decays, are discussed in detail. The "road map" towards the precision measurements is presented, including the use of control channels and other techniques to understand the performance of the detector with the first data from the LHC.
122332228
Alignment of the ATLAS inner detector
In order to reach the track parameter accuracy motivated by the physics goals of the experiment, the ATLAS tracking system needs to determine accurately its almost 700,000 degrees of freedom. The demanded precision for the alignment of the silicon sensors is below 10 μm. The implementation of the track based alignment within the ATLAS software framework unifies different alignment approaches and allows the alignment of all tracking subsystems together. The alignment software relies on the tracking information (track-hit residuals) but also includes the capability to set constraints on the beam-spot and primary vertex as well as the momentum measured by the Muon System or the E/p using the calorimetry information. The alignment chain starts at the trigger level where a stream of high pT isolated tracks is selected online. Also a cosmic ray trigger is enabled while ATLAS is recording collision data, thus a stream of cosmic-ray tracks is recorded exactly with the same detector operating conditions as the normal collision tracks. We will present results of the alignment of the ATLAS tracker using the 2011 collision data. The validation of the alignment is performed using track-hit residuals as well as using more advanced physics observables. The results of the alignment with real data reveals that the attained precision for the alignment parameters is approximately 5 μm.
118594336
Classical stability of the Galileon
A bstractWe consider the classical equations of motion for a single Galileon field with generic parameters in the presence of non-relativistic sources. We introduce the concept of absolute stability of a theory: if one can show that a field at a single point — like infinity for instance — in spacetime is stable, then stability of the field over the rest of spacetime is guaranteed for any positive energy source configuration. The Dvali-Gabadadze-Porrati (DGP) model is stable in this manner, and previous studies of spherically symmetric solutions suggest that certain classes of the single field Galileon (of which the DGP model is a subclass) may have this property as well. We find, however, that when general solutions are considered this is not the case. In fact, when considering generic solutions there are no choices of free parameters in the Galileon theory that will lead to absolute stability except the DGP choice. Our analysis indicates that the DGP model is an exceptional choice among the large class of possible single field Galileon theories. This implies that if general solutions (non-spherically symmetric) exist they may be unstable. Given astrophysical motivation for the Galileon, further investigation into these unstable solutions may prove fruitful.
16702193
First measurement of gamma(D*(+)).
We present the first measurement of the D*(+) width using 9/fb of e(+)e(-) data collected near the Upsilon(4S) resonance by the CLEO II.V detector. Our method uses advanced tracking techniques and a reconstruction method that takes advantage of the small vertical size of the Cornell Electron-positron Storage Ring beam spot to measure the energy release distribution from the D*(+)-->D(0)pi(+) decay. We find gamma(D*(+)) = 96+/-4 (stat)+/-22 (syst) keV. We also measure the energy release in the decay and compute Delta m identical with m(D*(+))-m(D(0)) = 145.412+/-0.002 (stat)+/-0.012 (syst) MeV/c(2).