The ATLAS level-1 central trigger system
The central part of the ATLAS Level-1 trigger system consists of the central trigger processor (CTP), the local trigger processors (LTPs), the timing, trigger, and control (TTC) system, and the read-out driver busy (ROD/spl I.bar/BUSY) modules. The CTP combines information from calorimeter and muon trigger processors, as well as from other sources, and makes the final Level-1 accept decision (L1A) on the basis of lists of selection criteria, implemented as trigger menus. Timing and trigger signals are fanned out to about 40 LTPs, which inject them into the subdetector TTC partitions. The LTPs also support stand-alone running and can generate all necessary signals from memory. The TTC partitions fan out the timing and trigger signals to the subdetector front-end electronics. The ROD/spl I.bar/BUSY modules receive busy signals from the front-end electronics, and send them to the CTP (via an LTP) to throttle the generation of L1As. An overview of the ATLAS Level-1 central trigger system will be presented, with emphasis on the design and tests of the CTP modules.
Diffractive dijet production in √s = 7 TeV pp collisions at the ATLAS Experiment
A data sample of pp collisions with an integrated luminosity of 6.75 nb\(^{-1}\) was collected using a combination of a minimum bias trigger and a single jet trigger at √s = 7 TeV using the ATLAS detector at the Large Hadron Collider. It is analysed to study diffractive dijet production, i.e. events with a hadronic system containing at least two jets in addition to a large region of pseudorapidity devoid of hadronic activity. The cross section is presented differentially with respect to Δη\(^F\), the largest continuous region of pseudorapidity which extends from the edge of the detector at η = ±4.9 and contains no final state particles above threshold momentum cuts, over the region 0 < Δη\(^F\) < 6.5. It is also presented differentially in the variable ξ\(^±\), which estimates the fractional momentum loss of the proton in single diffractive dissociation (pp → pX) events. Comparing the data distributions with a Monte Carlo model suggest that fluctuations in the hadronisation process allow non-diffractive dijets to look like diffractive events, but that the data cannot be described solely by non-diffractive dijet production. In addition, the monitoring of the electromagnetic and jet efficiencies for the ATLAS Level-1 Calorimeter Trigger is described.
LYAPUNOV-BASED TRANSFER BETWEEN ELLIPTIC KEPLERIAN ORBITS
We present a study of the transfer of satellites between elliptic Keplerian orbits using Lyapunov stability theory specific to this problem. The construction of Lyapunov functions is based on the fact that a non-degenerate Keplerian orbit is uniquely described by its angular momentum and Laplace (- Runge-Lenz) vectors. We suggest a Lyapunov function, which gives a feedback controller such that the target elliptic orbit becomes a locally asymptotically stable periodic orbit in the closed-loop dynamics. We show how to perform a global transfer between two arbitrary elliptic orbits based on the local transfer result. Finally, a second Lyapunov function is presented that works only for circular target orbits.