108773563
The silicon microstrip tracker for CMS
The CMS silicon strip tracker involves about 70 m2 of instrumented silicon, with approximately 18500 microstrip detectors read out by 5 × 106 electronics channels. It has to satisfy a set of stringent requirements imposed by the environment and by the physics expected at the LHC: low cell occupancy and good resolution, radiation hardness aided by adequate cooling, low mass combined with high stability. These conditions have been incorporated in a highly modular design of the detector modules and their support structures, chosen to facilitate construction and to allow for easy assembly and maintenance.
5742840
Crystallization in the Thin and Ultrathin Films of Poly(ethylene-vinyl acetate) and Linear Low-Density Polyethylene
The crystallization of poly(ethylene−vinyl acetate) and linear low-density polyethylene (LLDPE) films spun-cast from the polymer/toluene solutions with as-cast thickness from 460 to 10 nm was studied. The lamellar thickness was measured using small-angle X-ray scattering (SAXS) and found to increase from 14 to 21 nm for films thinner than 100 nm. The morphology of LLDPE measured by scanning probe microscopy (SPM) showed an edge-on lamellae for the films thicker than 30 nm and flat-on lamellae for the films thinner than 15 nm. A pseudo-“shish-kebab” tiny crystal structure was observed in between the larger lamellae. Crystallinity was confirmed using attenuated total reflectance−Fourier transformed infrared spectroscopy (ATR-FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The shear modulation force microscopy technique (SMFM) was used to measure the melting point, Tm, which was found to decrease for films thinner than 100 nm. The rate of decrease was a function of the annealing pr...
10177650
Clarification of the three-body decay of 12C (12.71 MeV).
Using beta decays of a clean source of 12N produced at the IGISOL facility, we have measured the breakup of the 12C (12.71 MeV) state into three alpha particles with a segmented particle detector setup. The high quality of the data permits solving the question of the breakup mechanism of the 12.71 MeV state, a longstanding problem in few-body nuclear physics. Among existing models, a modified sequential model fits the data best, but systematic deviations indicate that a three-body description is needed.
120316681
Experimental results of the betatron sum resonance
The experimental observations of motion near the betatron sum resonance, /spl nusub x/+2/spl nusub z/=13, are presented. A fast quadrupole (Panofsky-style ferrite picture-frame magnet with 8 pulsed power supplies) producing a betatron tune shift of the order of 0.03 at rise time of 1 /spl mu/s was used. This quadrupole was used to produce betatron tunes which jumped past and then crossed back through a betatron sum resonance line. The beam response as function of initial betatron amplitudes were recorded turn by turn. The correlated growth of the action variables, J/sub x/ and J/sub z/, was observed. The phase space plots in the resonance frame reveal the features of particle motion near the nonlinear sum resonance region.<<ETX>>
1289258
Energetic electrons associated with magnetic reconnection in the magnetic cloud boundary layer.
Here is reported in situ observation of energetic electrons (∼100-500 keV) associated with magnetic reconnection in the solar wind by the ACE and Wind spacecraft. The properties of this magnetic cloud driving reconnection and the associated energetic electron acceleration problem are discussed. Further analyses indicate that the electric field acceleration and Fermi-type mechanism are two fundamental elements in the electron acceleration processes and the trapping effect of the specific magnetic field configuration maintains the acceleration status that increases the totally gained energy.
22794424
Dipole and spin-dipole resonances in charge-exchange reactions on 12C.
The [sup 12]C([ital n],[ital p])[sup 12]B reaction was studied using the white neutron source at the Los Alamos Meson Physics Facility/Weapon Neutron Research Center with a continuous incident neutron energy from 60 to 260 MeV. Double differential cross sections were measured in the angular range 11[degree][le][theta][sub lab][le]37[degree]. Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility, we also studied the [sup 12]C([ital p],[ital n])[sup 12]N reaction at [ital E][sub [ital p]]=186 MeV and the [sup 12]C([ital [rvec p]],[ital [rvec n]])[sup 12]N reaction at [ital E][sub [ital [rvec p]]]=160 and 186 MeV. Double differential cross sections were measured between [theta][sub lab]=0[degree] and [theta][sub lab]=50[degree] in 5[degree] steps. Spin observables [ital D][sub [ital N][ital N]], [ital A][sub [ital Y]], and [ital P] were measured at [theta][sub lab]=5[degree],9[degree],13[degree] with [ital E][sub [ital [rvec p]]]=160 MeV and [theta][sub lab]=15[degree],20[degree] with [ital E][sub [ital [rvec p]]]=186 MeV. Angular distributions of differential cross section and spin observables for low-lying transitions in the residual nuclei are compared with disorted-wave impulse approximation (DWIA) calculations. A multipole decomposition analysis was performed to study the giant dipole and giant spin-dipole resonances. The contributions of the quasifree reaction in the giant resonance region was subtracted. The empirical results ofmore » energy distributions for dipole ([Delta][ital L]=1) transition are compared with DWIA calculations using nuclear structure information obtained with a conventional shell model and also with a random phase approximation.« less
121984352
The BES detector
Abstract The Beijing Spectrometer (BES) is a general purpose solenoidal detector at the Beijing Electron Positron Collider (BEPC). It is designed to study exclusive final states in e + e − annihilations at the center of mass energy from 3.0 to 5.6 GeV. This requires large solid angle coverage combined with good charged particle momentum resolution, good particle identification and high photon detection efficiency at low energies. In this paper we describe the construction and the performance of BES detector.
55280473
Cosmic-ray energy spectrum around the knee observed with the Tibet air-shower experiment
The energy spectrum of cosmic rays around the knee measured by Tibet air-shower experiment is summarized and its characteristic features are discussed under two possible scenarios. The result of Tibet experiment measured over wide range of10−10 eV with high statistics provided details of the knee at the energy around 4×10 eV. The study of the chemical composition based on measurements of proton and helium spectra obtained from airshower core detection indicates the dominance of heavy nuclei around the knee. Such feature can be explained either by contribution of nearby sources with source composition dominated by heavy nuclei or by nonlinear effect in diffusive shock acceleration mechanism. 1 Tibet Air-shower array and core detector The Tibet air-shower (AS) experiment is characterized by high altitude of the observation site (4300 m a.s.l., 606 g/cm), which enables us to determine the primary energy less dependent upon the primary mass and models of hadronic interactions in the energy range over PeV because of the observation of the shower size at nearly maximum development irrespective of the primary mass. The second merit of the high altitude is that it is possible to select the shower events of light nuclei origin such as protons and helium through the detection of high-energy secondary particles (electromagnetic component) located at the AS core, because the probability of association of high energy secondaries depends on primary mass by the difference of the interaction cross section in the atmosphere. The study of the primary mass composition is made by simultaneous operation of the AS array and the core detector. The AS array consists of 761 fast timing (FT) counters, surrounded by 28 density (D) counters with 36 900 m coverage as shown schematically in Fig. 1. The AS array is used to measure the energy and arrival direction of each AS. The details of the installation are described in ( Amenomori et al. , 2008a). The primary energy of each event is determined by the shower size Ne, which is calculated by fitting the lateral particle density distribution to the modified NKG structure function. The energy resolution is less than 20% for the knee energy range. The arrival direction of an air shower is determined as follows. The direction cosine of the shower axis is determined using a least square method in which the difference is minimized between the arrival time signals of each FT counter and the expected values on the assumed cone with a given direction cosine. This procedure determines the arrival angle with an accuracy smaller than 0.2◦ at energies above 10 eV, which is calibrated by observing the Moon’s shadow ( Amenomori et al., 2000a, 2003). The core detector was designed to detect the high-energy particles at the AS core by converting them into electromagnetic cascade showers (burst) using lead absorber of 160 cm×50 cm in area and 7 cm (in Phase I) or 3.5 cm (in Phase II) in thickness. The burst size under the lead plate was measured by scintillation counters of the same size as the lead plate in area and 2 cm in thickness. Four photodiodes were attached to the each corner of the scintillator whose attenuation length for the scintillation light was calibrated with electron beam. From the 4 photo-diode signals, we can estimate the burst size and the position of the burst center with spatial resolution of 10 cm. One hundred core detectors were used (total area is 80 m ) to detect burst size greater than5×10. The study of the primary mass composition was made through two experimental phases. In the first phase, 6 layers of X-ray films were placed between lead plates with 1 cm depth interval to register the development of shower spots induced by high-energy γ and electrons (hereafter abbreviated as γ-rays) over a few TeV which are incident upon the detector, and detailed analysis on the structure of the high energy core has been made with use of image scanner ( Ozawa et al. , 2004) to obtain proton and helium spectra ( Amenomori et al. , 2006). The energy determination of the individualγ-rays was made by the comparison of the transition curve of the optical density of the shower spots with electromagnetic shower theory. Such procedure of the energy determination using X-ray films was calibrated using 200 GeV electron beam at FNAL ( Hotta et al. , 1980). A bundle of the high energy γ-rays originating from successive nuclear interactions of the primary cosmic rays in the atmosphere is called γ-family, which can be detected by spatial reconstruction of the shower spots registered on X-ray films with angular resolution of 2.5◦. They are reconstructed as groups of parallel tracks with typical lateral spread of at most several cm among uncorrelated single tracks, which are reduced as background. The assignment of a γ f mily to an accompanied AS was made through the positional correlation between the X-ray film and the scintillator, and the correlation between the burst and AS was made by their time stamps. The arrival directions obtained from AS and the reconstruction of the shower spots were also used to uniquely determine the AS candidate. Suchγ-family events are more efficiently generated by light primaries than the case of heavy primaries because of the penetrating nature in the atmosphere. Hence, the AS core detector can select the air showers of light primary origin naturally. The contamination of the events of heavy nuclei origin was estimated using Artificial Neural Network (ANN) based on extensive Monte Carlo simulation of air showers (MC) assuming interaction models and primary models using CORSIKA code. Two interaction models of QGSJET and SIBYLL are used in estimating the efficiency of the γ family generation, and also two mass composition models of proton dominant (PD) and heavy dominant (HD) are used to appreciate the contamination rate of heavy primaries. The efficiency of the family generation for various primary nuclei and its energy dependence is calculated by MC and used for obtaining the primary proton and helium fluxes. For exAstrophys. Space Sci. Trans., 7, 15– 20, 2011 www.astrophys-space-sci-trans.net/7/15/2011/ M. Amenomori et al.: Cosmic-ray energy spectrum with the Tibet air-shower experiment 17 Fig. 1. Air-shower array located at Tibet, Yangbajing (4300 m a.s.l.) ample, the efficiencies by protons at the knee energy 4 PeV in phase I experiment are about 7% and 10% by QGSJET model and SIBYLL model, respectively. ANN is also used in procedures to obtain proton and helium spectra. Phase I experiment selected 177 γ family events with core energy ∑ Eγ >20 TeV and AS sizeNe>2×10. In the second phase experiment, X-ray films were not used and proton+helium (P+He) spectrum was studied without separating them but with higher statistics than that of phase I. The core detector was tuned to decrease the detection threshold energy of the AS core to have several times higher efficiency. The details of the analysis are described in (Amenomori et al. , 2007, 2010). 2 Experimental results The energy spectrum of all particles was obtained as shown in Fig. 2 together with other data (Cited data: Grigorov (Grigorov et al. , 1971), JACEE (Asakimori et al. , 1998), KASCADE (Antoni et al., 2005), BASJE (Ogio et al. , 2004), CASA (Fowler et al. , 2001), Akeno (Nagano et al. , 1984), Akeno array1 and Akeno array20 ( Nagano et al. , 1992)). The uncertainty of the absolute intensity due to the interaction models used in the analysis is shown by QGSJET and SIBYLL (10% difference at most). The uncertainty due to the assumed primary mass composition is also shown by HD and PD. Although the composition is fairly different between HD and PD models at energies above 10 eV, the difference of the absolute intensity is 20% at most between the two models and it decreases with increasing primary energy. Note that the shapes of the spectra from different models are almost the same and the position of the knee is clearly found at the energy around 4 PeV. From the second phase experiment of AS core observation, the energy spectrum of P+He was obtained with high statistics and in good agreement with phase I as shown in Fig. 3, in which QGSJET model was used for the analysis. Use of 10 2 10 3 10 4 10 4 10 5 10 6 10 7 10 8 10 9 E 2 .5 d J /d E [ G e V 1 .5 m − 2 s e c − 1 s r − 1 ] Primary Energy [GeV/particle] Grigorov JACEE KASCADE-QGS KASCADE-SIB BASJE2004 CASA/MIA Akeno Akeno array1 Akeno array20 Tibet3-QGSJET+HD Tibet3-QGSJET+PD Tibet3-SIBYLL+HD Fig. 2. All particle spectrum obtained by Tibet 3 array. The results from three models of QGSJET+HD, QGSJET+PD, and SIBYLL+HD used in the analysis are shown. SIBYLL model results in about 30% lower intensity than that of the QGSJET analysis There is a problem of discrepancy between Tibet and KASCADE data as shown in Fig. 3, e.g., the flux of the light nuclei by KADCADE is higher than Tibet by more than factor 2. However, if SIBYLL model is used in the analysis of KASCADE, the difference between two data is much reduced. This fact does not necessarily mean that SIBYLL model is more preferable to explain the data at this energy range. KASCADE reported that QGSJET model explains high energy data better than SIBYLL, on the other hand, SIBYLL model is better at lower energies. This problem is related to the interaction model dependence of MC calculations and also to the different experimental methods used in two experiments. Tibet experiment observes high energy part of the air showers, namely, the most forward region of the center of momentum system (CMS) of interacting particles, while KASCADE experiment observes Ne−Nμ correlation, in which muon component is sensitive to the central region of the CMS. The model dependence in forward region www.astrophys-space-sci-trans.net/7/15/2011/ Astrophys. Space Sci. Trans., 7, 15– 20, 2011 18 M. Amenomori et al.: Cosmic-ray energy spectrum with the Tibet air-shower experiment 10 1 10 2 10 3 10 4 10 5 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 
110051084
CHINESE STAR-TOF MRPC PRODUCTION AND QA TESTING
Multi-gap resistive plate camber (MRPC) has been demonstrated to have good time resolution (less than 100 ps), high detection efficiency (higher than 95%) and will be used to construct a full barrel time-of-flight (TOF) detector for the STAR experiment at RHIC. The cylindrical TOF covers a total area of approximately 64 m2 and about 4000 MRPC modules will be produced. Tsinghua University and University of Science and Technology of China (USTC) are responsible for the STAR MRPC production. In this paper we will describe the Tsinghua and USTC MRPC production facilities. Our MRPC manufacture procedures, detector assembly and testing results are also presented.
124790807
ILC 3.2 km damping ring design based on the FODO cell
We report on a new design for an ILC 3.2 km damping ring, with 2 arcs based on the FODO cell and 2 straight sections that are nearly the same as the newest version of the 6.4 km ring DCO4. This new lattice requires fewer magnets and a lower RF voltage, and has a better dynamic aperture than DCO4 while maintaining flexibility in regard to the momentum compaction factor. So far, this design is the only one satisfying all the requirements for a 3.2 km ring. The work on the lattice design and the dynamic aperture study is presented in detail.
118183165
Topological quantization of self-dual Chern-Simons vortices on Riemann surfaces
The self-duality equations of Chern-Simons Higgs theory in a background curved spacetime are studied by making use of the U(1) gauge potential decomposition theory and $\phi$-mapping method. The special form of the gauge potential decomposition is obtained directly from the first of the self-duality equations. Using this decomposition, a rigorous proof of magnetic flux quantization in background curved spacetime is given and the unit magnetic flux in curved spacetime is also found . Furthermore, the precise self-dual vortex equation with topological term is obtained, in which the topological term has always been ignored.