110979284
The R&D program for silicon detectors in CMS
Abstract This paper describes the main achievements in the development of radiation resistant silicon detectors to be used in the CMS tracker. After a general description of the basic requirements for the operation of large semiconductor systems in the LHC environment, the issue of radiation resistance is discussed in detail. Advantages and disadvantages of the different technological options are presented for comparison. Laboratory measurements and test beam data are used to check the performance of several series of prototypes fabricated by different companies. The expected performance of the final detector modules are presented together with preliminary test beam results on system prototypes.
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.
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
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>>
119818790
The L3 database system
Abstract The database system developed for the L3 experiment at the CERN large electron-positron (LEP) collider is described. The solution chosen has two components: a FORTRAN package (DBL3) and a system of distributed servers and data (L3DBSM). DBL3 provides basic database functions supplemented by facilities specific to high-energy physics experiments. The L3DBSM system, operational since the start of LEP data taking, has handled efficiently several hundred Mbytes of data over three different systems (VAX/VMS, IBM VM/CMS, Apollo Aegis SR10.x) and at eight different sites.
38323494
Search for the Lepton Flavor Violation Process J/ψ→eμ at BESIII
We search for the lepton-flavor-violating decay of the J/psi into an electron and a muon using (225.3 +/- 2.8) x 10(6) J/psi events collected with the BESIII detector at the BEPCII. Four candidate events are found in the signal region, consistent with background expectations. An upper limit on the branching fraction of B(J/psi -> e mu) <1.6 x 10(-7) (90% C.L.) is obtained.
108935761
A method for calibrating PMTs in T0 system for beam test
In order to study the performance of MRPC, which will be used for the upgrade of the Endcap TOF in BES III, a T0 system is composed of high speed response PMTs H6533 coupling with BC420 plastic scintillators. Because the T0 system should offer a toughly strict timing start, the high precision electronics based on VME system were used to test the SPS (single-photoelectron spectrum) of H6533 PMT. A suitable operation voltage for optimal performance is confirmed by researching the dependence relationship between the PMT gain and energy resolution of SPS (single-photoelectron spectrum). At the end, the timing resolution of this type of T0 system was 41.6 ps in the cosmic ray test and 39.1 ps in the proto beam test.
126290576
Results from the daya bay reactor neutrino experiment
The Daya Bay Reactor Neutrino Experiment was designed to achieve a sensitivity on the value of sin^2 2θ_(13) to better than 0.01 at 90% CL. The experiment consists of eight antineutrino detectors installed underground at different baselines from six nuclear reactors. With data collected with six antineutrino detectors for 55 days, Daya Bay announced the discovery of a non-zero value for sin^2 2θ_(13) with a significance of 5.2 standard deviations in March 2012. The most recent analysis with 139 days of data acquired in a six-detector configuration yields sin^2 2θ_(13) = 0.089 ± 0.010 (stat.) ± 0.005 (syst.), which is the most precise measurement of sin^2 2θ_(13) to date.
119170453
A new model for the Milky Way bar
We use Schwarzschild's orbit-superposition technique to construct self-consistent models of the Galactic bar. Using χ2 minimization, we find that the best-fitting Galactic bar model has a pattern speed Ωp = 60 km s−1 kpc−1, disc mass Md = 1.0 × 1011 M⊙ and bar angle θbar = 20° for an adopted bar mass Mbar = 2 × 1010 M⊙. The model can reproduce not only the three-dimensional and projected density distributions but also velocity and velocity dispersion data from the Bulge Radial Velocity Assay (BRAVA) survey. We also predict the proper motions in the range l = [−12°, 12°], b = [−10°, 10°], which appear to be higher than observations in the longitudinal direction. The model is stable within a time-scale of 0.5 Gyr, but appears to deviate from steady state on longer time-scales. Our model can be further tested by future observations such as those from GAIA.