LEP measurements of Vcb_{cb} and Vub_{ub}

The magnitude of the CKM matrix element V/sub cb/ has been measured using B/sup 0/ to D*/sup +/l/sup -/ nu decays recorded on the Z/sup 0 / peak using the OPAL, ALEPH and DELPHI detectors at LEP. The D*/sup +/ to D/sup 0/ pi /sup +/ decays were reconstructed both in particular decay modes and via an inclusive technique. The product of V/sub cb/and the decay form factor of the B/sup 0/ to D*/sup +/l /sup -/ nu transition at zero recoil F(1) was measured to be F(1) V /sub cb/=(35.6+or-1.7)*10/sup -3/. V/sub cb/ is obtained by using Heavy Quark Effective Theory calculations for F(1). The semi-leptonic branching ratio BR(b to cl nu ) is also used to extract V/sub cb/. The combined result is V/sub cb/=(40.7+or-1.9)*10/sup -3/. The semi-leptonic branching ratio BR(b to ul nu ) is measured and used to extract the magnitude of V/sub ub/, V/sub ub/=(4.09/sub -0.69//sup +0.59/)*10/sup -3/. (12 refs)

The Thin Gap Chambers database experience in test beam and preparations for ATLAS

Thin gap chambers (TGCs) are used for the muon trigger system in the forward region of the LHC experiment ATLAS. The TGCs are expected to provide a trigger signal within 25 ns of the bunch spacing. An extensive system test of the ATLAS muon spectrometer has been performed in the H8 beam line at the CERN SPS during the last few years. A relational database was used for storing the conditions of the tests as well as the configuration of the system. This database has provided the detector control system with the information needed for configuration of the front end electronics. The database is used to assist the online operation and maintenance. The same database is used to store the non event condition and configuration parameters needed later for the offline reconstruction software. A larger scale of the database has been produced to support the whole TGC system. It integrates all the production, QA tests and assembly information. A 1/12th model of the whole TGC system is currently in use for testing the performance of this database in configuring and tracking the condition of the system. A prototype of the database was first implemented during the H8 test beams. This paper describes the database structure, its interface to other systems and its operational performance.Comment: Proceedings IEEE, Nuclear Science Symposium 2005, Stockholm, Sweeden, May 200

Trigger and Reconstruction for a heavy long lived charged particles with the ATLAS detector

Long lived charged particles are predicted by many models of physics beyond the standard model (SM). The common signature of such models is a heavy long-lived charged particle with velocity smaller than the speed of light, beta<1. This unique signature makes the search for it model independent. This paper presents methods developed as part of the ATLAS trigger and reconstruction chain for identifying slow particles and measuring their mass. The efficacy of these methods is demonstrated using two models that are different in every aspect except for the existence of long lived charged particles; A GMSB model that includes sleptons with a mass of 100 GeV, and R-Hadrons with a mass of 300 GeV produced in a split SUSY model

Trigger Selection Software for Beauty Physics in ATLAS

The unprecedented rate of beauty production at the LHC will yield high statistics for measurements such as CP violation and Bs oscillation and will provide the opportunity to search for and study very rare decays, such as Bâ ï­ï­ .The trigger is a vital component for this work and must select events containing the channels of interest from a huge background in order to reduce the 40 MHz bunch crossing rate down to 100-200 Hz for recording, of which only a part will be assigned to B-physics. Requiring a single or di-muon trigger provides the first stage of the B-trigger selection. Track reconstruction is then performed in the Inner Detector, either using the full detector, at initial luminosity, or within Regions of Interest identified by the first level trigger at higher luminosities. Based on invariant mass, combinations of tracks are selected as likely decay products of the channel of interest and secondary vertex fits are performed. Events are selected based on properties such as fit quality and invariant mass. We present fast vertex reconstruction algorithms suitable for use in the second level trigger and event filter (level three). We discuss the selection software and the flexible trigger strategies that will enable ATLAS to pursue a B-physics programme from the first running at a luminosity of about 1031 cm-2s-1 through to the design luminosity running at 1034 cm-2s-1

Trigger and reconstruction for heavy long-lived charged particles with the ATLAS detector

Long lived charged particles are predicted by many models of physics beyond the standard model (SM). The common signature of such models is a heavy long-lived charged particle with velocity smaller than the speed of light, β<1. This unique signature makes the search for it model independent. This paper presents methods we developed as part of the ATLAS trigger and reconstruction chain for identifying slow particles and measuring their mass. The efficacy of these methods is demonstrated using two models that are different in every aspect except for the existence of long lived charged particles; a GMSB model that includes sleptons with a mass of 100 GeV, and R-Hadrons with a mass of 300 GeV produced in a split SUSY model

Probing High Reheating Temperature Scenarios at the LHC with Long-Lived Staus

We investigate the possibility of probing high reheating temperature scenarios at the LHC, in supersymmetric models where the gravitino is the lightest supersymmetric particle, and the stau is the next-to-lightest supersymmetric particle. In such scenarios, the big-bang nucleosynthesis and the gravitino abundance give a severe upper bound on the gluino mass. We find that, if the reheating temperature is \sim 10^8 GeV or higher, the scenarios can be tested at the LHC with an integrated luminosity of O(1 fb^{-1}) at \sqrt{s}=7 TeV in most of the parameter space.Comment: 17 pages, 5 figures, minor modification

The Certification of ATLAS Thin Gap Chambers Produced in Israel and China

Thin gap chambers (TGCs) are used for the muon trigger system in the forward region of the LHC experiment ATLAS. A TGC consists of a plane of closely spaced wires maintained at positive high voltage, sandwiched between resistive grounded cathode planes with an anode wire to cathode plane gap distance smaller than the wire-to-wire spacing. The TGCs are expected to provide a trigger signal within 25 ns of the bunch spacing of the LHC accelerator, with an efficiency exceeding 95%, while exposed to an effective photon and neutron background ranging from 30 to 500 Hz/cm2. About 2,500 out of the 3,600 ATLAS TGCs are being produced at the Weizmann institute in Israel, and in Shandong University in China. Once installed in the ATLAS detector the TGCs will be inaccessible. A vigorous production quality control program is therefore implemented at the production sites. Furthermore, after chamber completion, a thorough program of quality assurance is implemented to ensure the efficient performance of the chambers during more than ten years of operation in the LHC high rate environment. This program consists of a detailed mapping of the detectors response using cosmic rays, as well as checking the chambers behavior using a high rate radiation source. An aging test performed on five chambers in a serial gas connection is presented. Finally the results of the chambers certification tests performed at CERN before the installation in ATLAS are described.Comment: Presented at 2004 IEEE Nuclear Science Symposium 2004, Rome, Oct 200

Implementation and performance of the ATLAS Trigger Muon "Vertical Slice"

The ATLAS (A Toroidal LHC ApparatuS) trigger system is designed to keep high effiency for interesting events while achieving a rejection of low transverse momentum (p_T) physics of about 10^7, thus reaching the ~200Hz data storage capability of the Data Aquisition system. A three levels structure has been implemented for this purpose, as described in this work for the case of the muon trigger system. After describing the implementation, some performance results are presented in terms of final trigger rates, resolutions, efficiencies, background rejection and algorithm latency

A new multi-robot search algorithm using Probabilistic Finite State Machine and Lennard-Jones potential function

Swarm robotics is a decentralized approach to robotic systems. This paper investigates the problem of search and rescue using swarm robots. A multi-robot search algorithm using probabilistic finite state machine and interaction inspired by Lennard-Jones potential function has been proposed. Probabilistic finite state machine has been used to separate the tasks performed and to change coordination rules according to the circumstances and social probabilities. The approach is tested in various scenarios to test flexibility, scalability and robustness. The performance result is promising. Algorithmic complexity comparison with Robotic Darwinian Particle Swarm Optimization and Glowworm Swam Optimization appear favourable