123022232
Commissioning of the ATLAS level1 endcap muon trigger system
Abstract The ATLAS level1 endcap muon trigger system at the LHC selects interesting events containing muons with transverse momenta greater than 6 GeV/c from 40 MHz proton–proton collisions. This system consists of 3588 Thin Gap Chambers (TGC) and the total number of readout channels is 3.18×105. The trigger logic is based on the coincidence between 7 layers of TGC. All processes are performed using hardware within the maximum latency of 2.5 μ s for the level1 trigger. To be ready for the first beam collisions scheduled in 2009, we have succeeded in sending trigger signals of cosmic ray muons with the synchronous operation at 40 MHz and fine signal timing alignments. During the single proton beam circulation at the LHC in 2008, we have also confirmed that the timing of the endcap muon trigger for tracks of beam halo muons produced at the collimator was well aligned. We report on the status of the commissioning and results from runs with cosmic ray muons and single beams.
62822934
Precise timing adjustment for the ATLAS level 1 endcap muon trigger system
The ATLAS level-1 endcap muon trigger system consists of about 4000 Thin Gap Chambers (TGC) with 320,000 input electronics channels in order to find level-1 trigger candidates for muons in both endcap regions. Three TGC stations are deployed with about 1m interval with 15m apart from the interaction point in z-direction on each endcap side and the radius of the station (disc form) is about 25m. Usually hit signals are not timely aligned because of different cable length and different time of muon flight. In order to supply reliable level-1 endcap trigger signals, we must adjust timing of hit signals for all the channels with the precision of±2.5ns. In the meantime we have to adjust also the bunch crossing phase used in the TGC system with one from LHC. We need, however, actual bunch crossing signals in order to accomplish this. In this paper we discuss strategies for timing alignment of individual channels with the timing adjustment facility embedded in the TGC electronics system and for the adjustment of the phase shift of the bunch crossing signals.
125122742
J/psi production in Cu+Cu and Au+Au collisions at RHIC-PHENIX
10281433
Evaluation of test structures for the novel n + -in-p pixel and strip sensors for very high radiation environments
Abstract Radiation-tolerant n + -in-p silicon sensors were developed for use in very high radiation environments. Novel n + -in-p silicon strip and pixel sensors and test structures were fabricated, tested and evaluated, in order to understand the designs implemented. The resistance between the n + implants (interstrip resistance), the electric potential of the p-stop, and the punch-through-protection (PTP) onset voltage were measured before and as a function of fluence after irradiation. The technology computer-aided design (TCAD) simulations were used to understand the radiation damage and fluence dependence of the structures. The decrease in the interstrip resistance is a consequence of increased leakage current. The decrease in the electric potential of the p-stop results from a build-up of positive charge in the silicon–silicon oxide interface. The decrease and subsequent increase in the PTP onset voltages results from the interface charge build-up and an increase in acceptor states.
174792146
Development of a time projection chamber using gas electron multipliers ( GEM – TPC )
We developed a prototype time projection chamber using gas electron multipliers (GEM–TPC) for high energy heavy ion collision experiments. To investigate its performance, we conducted a beam test with three kinds of gases (Ar(90%)–CH4(10%), Ar(70%)–C2H6(30%) and CF4). Detection efficiency of 99%, and spatial resolution of 79mm in the pad-row direction and 313mm in the drift direction were achieved. The test results show that the GEM–TPC meets the requirements for high energy heavy ion collision experiments. The configuration and performance of the GEM–TPC are described. r 2006 Elsevier B.V. All rights reserved. PACS: 29.40.Cs; 29.40.Gx; 25.75. q
18734752
Grand-Canonical Simulation of Two-Dimensional Simplicial Gravity
The string susceptibility exponents of dynamically triangulated 2-dimensional surfaces with various topologies, such as a sphere, torus and double-torus, were calculated by the grand-canonical Monte Carlo method. These simulations were made for surfaces coupled to $d$-Ising spins ($d$=0,1,2,3,5). In each simulation the area of surface was constrained to within 1000 to 3000 of triangles, while maintaining the detailed-balance condition. The numerical results show excellent agreement with theoretical predictions as long as $d \leq 2$.