119013591
Precision muon spectrometry in the L3 experiment at lep
121764664
The DIRC prototype for the WASA experiment at COSY
The implementation of a DIRC (Detector or Internally Reflected Cherenkov light) was planned for the WASA-at-COSY experiment, located at the Forschungszentrum Julich and is a major project for the future PANDA experiment at FAIR. In order to study the components and the behavior of the detector under experimental conditions, a large scale demonstrator made of acrylic glass was built and tested at the external proton beam of the COSY accelerator. The main properties of the components, especially of the newly developed front end electronics and the results of the first tests are presented.
36263241
New optimization methods for converging perturbative series with a field cutoff
We take advantage of the fact that in lambda phi ^4 problems a large field cutoff phi_max makes perturbative series converge toward values exponentially close to the exact values, to make optimal choices of phi_max. For perturbative series terminated at even order, it is in principle possible to adjust phi_max in order to obtain the exact result. For perturbative series terminated at odd order, the error can only be minimized. It is however possible to introduce a mass shift in order to obtain the exact result. We discuss weak and strong coupling methods to determine the unknown parameters. The numerical calculations in this article have been performed with a simple integral with one variable. We give arguments indicating that the qualitative features observed should extend to quantum mechanics and quantum field theory. We found that optimization at even order is more efficient that at odd order. We compare our methods with the linear delta-expansion (LDE) (combined with the principle of minimal sensitivity) which provides an upper envelope of for the accuracy curves of various Pade and Pade-Borel approximants. Our optimization method performs better than the LDE at strong and intermediate coupling, but not at weak coupling where it appears less robust and subject to further improvements. We also show that it is possible to fix the arbitrary parameter appearing in the LDE using the strong coupling expansion, in order to get accuracies comparable to ours.
15702909
The continuum limit of perturbative coefficients calculated with a large field cutoff
Abstract We report MC calculations of perturbative coefficients for lattice scalar field theory in dimensions l, 2 and 3, where the large field contributions are cutoff. This produces converging (instead of asymptotic) perturbative series. We discuss the statistical errors and the lattice effects and sho-kv that accurate calculations are possible even in a crossover region where no approximation works. We show that the field cutoff is also a UV regulator. We point out the relevance for QCD questions discussed by Tomboulis ad Trottier at this conference.
15336878
Hot subdwarfs from the stable Roche lobe overflow channel
Context. Hot subdwarfs are core-helium-burning stars with extremely thin envelopes. We discuss the formation and evolution of hot subdwarfs formed through the stable Roche lobe overflow (RLOF) channel of intermediate-mass binaries, although their formation channels are various. Aims. In this study, we concentrate on the formation and evolution of hot subdwarfs binaries through the stable RLOF channel of intermediate-mass binaries. We aim at setting out the properties of hot subdwarfs and their progenitors, so that we can understand the formation and evolution of hot subdwarfs. Methods. Employing Eggleton's stellar evolution code, we have computed conservative and nonconservative population I binary evolution sequences. The initial mass of the primary ranges from 2.2 to 6.3 M(circle dot), spaced by approximately 0.1 in log M, the initial mass ratio q(i) = M(1)/M(2) is between 1.1 and 4.5, and the Roche lobe overflow begins at the main sequence, the Hertzsprung gap and the first giant branch. In nonconservative binary evolution, we assume that 50 percent of the mass lost from the primary leaves the system, carrying away the specific angular momentum of the primary, and the remaining mass is accreted on to the secondary during the RLOF. Also, we have studied the distributions of the mass and orbital periods of hot subdwarfs using the population synthesis approach. Results. We have obtained the ranges of the initial parameters of progenitor binaries and the properties of hot subdwarfs through the stable RLOF channel of intermediate-mass binaries, e. g. mass, envelope mass and age of hot subdwarfs. We have found that hot subdwarfs could be formed through stable Roche lobe overflow at the main sequence and Hertzsprung gap. We have also found that some subdwarf B or OB stars have anomalously high mass (similar to 1 M(circle dot)) with a thick envelope (similar to 0.07 M(circle dot)-similar to 0.16) in our models. By comparing our theoretical results with observations on the hot subdwarfs in open clusters, we suggest that more hot subdwarfs in binary systems might be found in open clusters in the future.
122970197
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha(s)
Multijet production rates in neutral current deep inelastic scattering (DIS) have been measured in the range of exchanged boson virtualities 10<Q2<5000 GeV2. The data were taken at the ep collider HERA with centre-of-mass energy using the ZEUS detector and correspond to an integrated luminosity of 82.2 pb-1. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential multijet cross sections are presented as functions of jet transverse energy , pseudorapidity and Q2 with and . Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant αs(MZ), determined from the ratio of the trijet to dijet cross sections, is .
110023193
Studies of an array of PbF 2 Cherenkov crystals with large-area SiPM readout
The electromagnetic calorimeter for the new muon (g 2) experiment at Fermilab will consist of arrays of PbF2 Cerenkov crystals read out by large-area silicon photo-multiplier (SiPM) sensors. We report here on measurements and simulations using 2.0 { 4.5 GeV electrons with a 28-element prototype array. All data were obtained using fast waveform digitizers to accurately capture signal pulse shapes versus energy, impact position, angle, and crystal wrapping. The SiPMs were gain matched using a laser-based calibration system, which also provided a stabilization procedure that allowed gain correction to a level of 10 4 per hour.
119213308
Tachyon field in loop quantum cosmology: An example of traversable singularity
Loop quantum cosmology (LQC) predicts a nonsingular evolution of the universe through a bounce in the high energy region. But LQC has an ambiguity about the quantization scheme. Recently, the authors in [Phys. Rev. D 77, 124008 (2008)] proposed a new quantization scheme. Similar to others, this new quantization scheme also replaces the big bang singularity with the quantum bounce. More interestingly, it introduces a quantum singularity, which is traversable. We investigate this novel dynamics quantitatively with a tachyon scalar field, which gives us a concrete example. Our result shows that our universe can evolve through the quantum singularity regularly, which is different from the classical big bang singularity. So this singularity is only a weak singularity.
117833563
A Library of Lick/IDS Indices for Binary Stellar Populations
Using EPS we present 13 refined Lick/IDS absorption-line indices for an extensive set of instantaneous-burst binary stellar populations (BSPs) at high resolution (0.3 \AA) of various age and metallicity (1-15Gyr, 0.004-0.03), and 38 indices at intermediate resolution (3 \AA). These indices are obtained by two methods: (1) obtain them by using the empirical fitting functions (FFs method); (2) measure them directly from the synthetic spectra (DC method). Together with our previous paper a database of Lick/IDS spectral absorption-line indices for BSPs at high and intermediate resolutions is provided. This set of indices includes 21 indices of Worthey et al., four Balmer indices defined by Worthey & Ottaviani and 13 indices with the new passband definitions of Trager et al. The full set of synthetic indices and the integrated pseudo-continuum are listed in the Appendix, which is only available online or from our website (this http URL com/), or on request from the first author. Moreover, the ISEDs can be obtained from our website. 
We compare the synthetic Lick/IDS indices obtained by FFs method and those by DC method, and find that the discrepancies are significant: Ca4455 (index 6), Fe4668 (8), Mg_b (13), Fe5709 (17), NaD (19), TiO_1 (20) and TiO_2 (21, except for Z=0.02) in the W94 system, Ca4455^T (6^T), C_2 4668^T (8^T), NaD^T (19^T), TiO_1^T (20^T) and TiO_2^T (21^T, except for Z=0.02) in the T98 system obtained by DC method are less (bluer) than the corresponding ones obtained by FFs method for all metallicities. Ca4227 (index 3), Fe5782 (18),Ca4227^T (3^T) and Fe5782^T (18^T) are greater at Z=0.03 and become to be bluer at Z=0.004, Fe5709^T (17^T) index is less at Z=0.03 and becomes to be redder at Z=0.004 than the corresponding ones obtained by FFs method.
119221579
Observation of Single Top Quark Production at D0
This paper presents the observation of the electroweak production of single top quarks in the D0 detector at the Fermilab Tevatron pp Collider at a center‐of‐mass energy of 1.96 TeV. Events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks are used to measure a cross section for single top‐quark production of σ(pp→tb+X,tqb+X) = 3.94±0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5×10−7, corresponding to a 5.0 standard deviation significance.
123070841
Open Charm Physics at BESIII
An integrated luminosity of 2.9 fb − 1 data had been collected at s = 3.773 GeV by May of 2011 with the BESIII detector at the BEPCII collider, which makes it possible to systematically study the properties of the semileptonic, leptonic and hadronic decays of the charmed mesons. With the data, many high precise measurements including the CKM matrix elements and the form factors, the decay constants, as well as the topics related to hadronic decays such as absolute branching fractions, searches for CP violations and Dalitz plot analyses are being studied at the BESIII. All these analyses are expected to be accomplished in the near future.