119938939
Progress of R&D and production of timing RPCs in Tsinghua University
Abstract Multi-gap resistive plate chamber (MRPC) is a new kind of gas detector. It has good time resolution and high efficiency and has been adopted to construct the full barrel time-of-flight (TOF) detector for the STAR experiment at RHIC. The high rate TOF of CBM is also proposed to be assembled with MRPCs. Tsinghua University is a collaboration member of the two experiments and has made substantial progress on the R&D and production of MRPC. In this paper, we describe the development of low-resistivity glass and high rate MRPC, and the development of 1 m long counter is also described.
121580460
A prototype of a high rating MRPC
Six-gap resistive plate chamber (MRPC) prototypes with semiconductive glass electrodes (bulk resistivity ~ 1010 Ωcm) were studied for suitability in time-of-flight (TOF) applications at high rates. These studies were performed using a continuous electron beam of 800 MeV at IHEP and an X-ray machine. Time resolutions of about 100 ps and efficiencies larger than 90% were obtained for flux densities up to 28 kHz/cm2.
6716887
Three-particle coincidence of the long range pseudorapidity correlation in high energy nucleus-nucleus collisions.
We report the first three-particle coincidence measurement in pseudorapidity (Δη) between a high transverse momentum (p⊥) trigger particle and two lower p⊥ associated particles within azimuth |Δϕ|<0.7 in square root of s(NN)=200 GeV d+Au and Au+Au collisions. Charge ordering properties are exploited to separate the jetlike component and the ridge (long range Δη correlation). The results indicate that the correlation of ridge particles are uniform not only with respect to the trigger particle but also between themselves event by event in our measured Δη. In addition, the production of the ridge appears to be uncorrelated to the presence of the narrow jetlike component.
122051470
Performance of a new LMRPC prototype for the STAR MTD system
A new prototype of a Long-Strip Multi-Gap Resistive Plate Chamber (LMRPC) for the STAR Muon Telescope Detector (MTD) at RHIC has been developed. This prototype has an active area of 52 x 90 cm(2) and consists of six 250 mu m wide gaps. Each detector has 12 strips, read-out at both ends, which are each 3.8 cm wide and 90 cm long with 0.6 cm intervals. In cosmic-ray tests, the efficiency was larger than 95% and the time resolution was similar to 75 ps for the 94% Freon, 5% iso-butane, and 1% SF6 gas mixture. There was good uniformity in the performance across the different strips. The module was also tested in a proton beam at IHEP in Beijing. The efficiency was close to 100% and the best timing resolution achieved was 55 ps for the 90% Freon, 5% iso-butane, and 5% SF6 gas mixture. Trigger scans along and across the strip direction were also performed. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
120854659
Study on the position resolution of resistive plate chamber
A prototype RPC detector with a 2-mm readout strip pitch has been built for research into its position resolution. After determining the optimal threshold and working voltage, the efficiency and position resolution of this prototype RPC detector have been studied carefully. Using cosmic-ray muons with different directions and incident positions, we have obtained less than 0.5-mm average statistical errors of position resolution for two different RPC readout structures: 1- and 1.7-mm readout strip widths. The results show that the RPC can also give high position resolution with very little variation from its traditional structure. This will lead to possible applications of the RPC in medical imaging and other domains.
56430796
Measurements of $D^{0}$ and $D^{*}$ Production in $p$ + $p$ Collisions at $\sqrt{s}$ = 200 GeV
We report measurements of charmed-hadron ($D^{0}$, $D^{*}$) production cross sections at mid-rapidity in $p$ + $p$ collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decays $D^{0}\rightarrow K^{-}\pi^{+}$, $D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+}$ and their charge conjugates, covering the $p_T$ range of 0.6$-$2.0 GeV/$c$ and 2.0$-$6.0 GeV/$c$ for $D^{0}$ and $D^{*+}$, respectively. From this analysis, the charm-pair production cross section at mid-rapidity is $d\sigma/dy|_{y=0}^{c\bar{c}}$ = 170 $\pm$ 45 (stat.) $^{+38}_{-59}$ (sys.) $\mu$b. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum differential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.
119228702
Cosmological evolution of the Fanaroff–Riley type II source population
By combining a model for the evolution of the radio luminosity of an individual source with the radio luminosity function, we perform a multidimensional Monte Carlo simulation to investigate the cosmological evolution of the Fanaroff–Riley type II (FR II) radio galaxy population by generating large artificial samples. The properties of FR II sources are required to evolve with redshift in the artificial samples to fit the observations. Either the maximum jet age or the maximum density of the jet environment or both evolve with redshift. We also study the distribution of FR II source properties as a function of redshift. From currently available data we cannot constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately −2. This power-law slope does not change with redshift out to z = 0.6. We also find the distribution of the pressure in the lobes of FR II sources to evolve with redshift up to z ∼ 1.2.
121188260
Testing the time resolution of the BESIII end-cap TOF detectors
Modules of the end-cap time-of-flight detector (ETOF) for the Beijing spectrometer upgrade (BESIII) using different types of scintillators, BC408, BC404 and EJ204, were tested with an 800 MeV electron beam. Different wrapping materials were also tested to improve the light collection efficiency and time resolution. The enhanced specular reflector (ESR) film was found to be the best wrapping material. A time resolution of better than 80 ps over the full length of the ETOF module was achieved.
18953757
Eternal chaotic inflation is prohibited by the weak gravity conjecture
We investigate whether eternal chaotic inflation can be achieved when the weak gravity conjecture is taken into account. We show that even assisted chaotic inflation with potential λ4 or m22 cannot be eternal. The effective field theory description for the inflaton field breaks down before inflation reaches the eternal regime. We also find that the total number of e-folds is still bounded by the inflationary entropy for the assisted inflation.
121446966
The Muon Filter of the L3 detector
Abstract In this article we describe the outer part (Muon Filter) of the Hadron Calorimeter of the L3 detector. Construction and performance of the brass chambers, which form the sensitive part of the detector, are reviewed. We also report the results from data taken on two beam tests, at CERN.
56215933
PLC and Linux based control system for the CAMD Linac
Louisiana State University Center for Advanced Microstructures and Devices (CAMD) began operations in the fall of 1992. At the time, the facility had separate control systems for the storage ring and Linac. In 1997, CAMD began a control system upgrade project with the goal of producing a single unified control system running on the PC/Linux platform. After completion of the storage ring control system, the Linac control system was designed utilizing AutomationDirect.com PLCs for the real-time components, and PC/Linux for the user interface. The new Linac control system has been completed, and has been operational since July 2002. This paper will discuss the objectives, design, and future upgrade plans for the Linac control system, as well as the experiences with replacing the CGR-MeV VME/OS/9 control system with a PLC/PC/Linux based system.