24 research outputs found
Vacuum Topology of the Two Higgs Doublet Model
We perform a systematic study of generic accidental Higgs-family and CP
symmetries that could occur in the two-Higgs-doublet-model potential, based on
a Majorana scalar-field formalism which realizes a subgroup of GL(8,C). We
derive the general conditions of convexity and stability of the scalar
potential and present analytical solutions for two non-zero neutral vacuum
expectation values of the Higgs doublets for a typical set of six symmetries,
in terms of the gauge-invariant parameters of the theory. By means of a
homotopy-group analysis, we identify the topological defects associated with
the spontaneous symmetry breaking of each symmetry, as well as the massless
Goldstone bosons emerging from the breaking of the continuous symmetries. We
find the existence of domain walls from the breaking of Z_2, CP1 and CP2
discrete symmetries, vortices in models with broken U(1)_PQ and CP3 symmetries
and a global monopole in the SO(3)_HF-broken model. The spatial profile of the
topological defect solutions is studied in detail, as functions of the
potential parameters of the two-Higgs doublet model. The application of our
Majorana scalar-field formalism in studying more general scalar potentials that
are not constrained by the U(1)_Y hypercharge symmetry is discussed. In
particular, the same formalism may be used to properly identify seven
additional symmetries that may take place in a U(1)_Y-invariant scalar
potential.Comment: 89 pages, 13 tables and 12 figures (version as to appear in JHEP
First data with the ATLAS Level-1 Calorimeter Trigger
The ATLAS Level-1 Calorimeter Trigger is one of the main elements of the first stage of event selection for the ATLAS experiment at the LHC. The input stage consists of a mixed analogue/digital component taking trigger sums from the ATLAS calorimeters. The trigger logic is performed in a digital, pipelined system with several stages of processing, largely based on FPGAs, which perform programmable algorithms in parallel with a fixed latency to process about 300 Gbyte/s of input data. The real-time output consists of counts of different types of physics objects, and energy sums. The final system consists of over 300 custom-built VME modules, of several different types. The installation at ATLAS of these modules, and the necessary infrastructure, was completed at the end of 2007. The system has since undergone intensive testing, both in standalone mode, and in conjunction with the whole of the ATLAS detector in combined running. The final steps of commissioning, and experience with running the full-scale system are presented. Results of integration tests performed with the upstream calorimeters, and downstream trigger and data-flow systems, are shown, along with an analysis of the performance of the calorimeter trigger in full ATLAS data-taking. This includes trigger operation during the cosmic muon runs from before LHC start-up, and a first look at LHC proton beam data
A first level calorimeter trigger for LHC experiments. Design studies, and beam tests of a first prototype trigger system
Cancer-Preventive Selenocompounds Induce a Specific Redox Modification of Cysteine-Rich Regions in Ca2+- Dependent Isoenzymes of Protein Kinase C
Use of an FPGA to identify Electromagnetic Clusters and Isolated Hadrons in the ATLAS Level-1 Calorimeter Trigger
ATLAS level-1 calorimeter trigger: subsystem tests of a Jet/Energy-sum Processor module
The ATLAS Level-1 Calorimeter Trigger consists of a Preprocessor, a Cluster Processor (CP), and a Jet/Energy-sum Processor (JEP). The CP and JEP receive digitised trigger-tower data from the Preprocessor and produce trigger multiplicities and total and missing energy for the final trigger decision. The trigger will also provide region-of-interest (RoI) information for the Level-2 trigger and intermediate results of the data acquisition (DAQ) system for monitoring and diagnostics by using readout driver modules (ROD). The Jet/Energy-sum Processor identifies and localises jets, and sums total and missing transverse energy information from the trigger data. The Jet/Energy Module (JEM) is the main module of the Jet/Energy-sum Processor. The JEM prototype is designed to be functionally identical to the final production module for ATLAS, and have the full number of channels. Three JEM prototypes have been built and successfully tested. Various test vector patterns were used to test the energy summation and the jet algorithms. Data communication between adjacent Jet/Energy Modules and all other relevant modules of the Jet/Energy-sum Processor has been tested. Recent test results using the Jet/Energy Module prototypes are discussed
The Atlas Level-1 Calormeter Trigger Architecture
The architecture of the ATLAS Level-1 Calorimeter Trigger system (L1Calo) is presented. Common approaches have been adopted for data distribution, result merging, readout, and slow control across the three different subsystems. A significant amount of common hardware is utilized, yielding substantial savings in cost, spares, and development effort. A custom, high-density backplane has been developed with data paths suitable for both the em/tt cluster processor (CP) and jet/energy-summation processor (JEP) subsystems. Common modules also provide interfaces to VME, CANbus and the LHC Timing, Trigger and Control system (TTC). A common data merger module (CMM) uses FPGAs with multiple configurations for summing electron/photon and tau/hadron cluster multiplicities, jet multiplicities, or total and missing transverse energy. The CMM performs both crate- and system-level merging. A common, FPGA-based readout driver (ROD) is used by all of the subsystems to send input, intermediate and output data to the data acquisition system (DAQ), and region-of-interest (RoI) data to the level-2 triggers. Extensive use of FPGAs throughout the system makes the trigger flexible and upgradeable, and several architectural choices have been made to reduce the number of inter-crate links and make the hardware more robust