3,774 research outputs found
LEP measurements of V and V
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)
Reconstruction And Identification Of Heavy Long-Lived Particles At The ATLAS Detector At The LHC
Long-lived charged particles are predicted by many models of physics beyond the Standard Model (SM). At the LHC, the common signature would be a heavy long-lived charged particle with velocity smaller than the speed of light, <1. This paper presents methods we developed for identifying slow particles and measuring their mass using the ATLAS muon spectrometer. The efficacy of these methods is demonstrated using two different models
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
Design, prototyping and testing of the detector control system for the ATLAS endcap muon trigger
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
Measuring Lepton Flavour Violation at LHC with Long-Lived Slepton in the Coannihilation Region
When the mass difference between the lightest slepton, the NLSP, and the
lightest neutralino, the LSP, is smaller than the tau mass, the lifetime of the
lightest slepton increases in many orders of magnitude with respect to typical
lifetimes of other supersymmetric particles. These small mass differences are
possible in the MSSM and, for instance, they correspond to the coannihilation
region of the CMSSM for M_{1/2} \gsim 700 GeV. In a general gravity-mediated
MSSM, where the lightest supersymmetric particle is the neutralino, the
lifetime of the lightest slepton is inversely proportional to the square of the
intergenerational mixing in the slepton mass matrices. Such a long-lived
slepton would produce a distinctive signature at LHC and a measurement of its
lifetime would be relatively simple. Therefore, the long-lived slepton scenario
offers an excellent opportunity to study lepton flavour violation at ATLAS and
CMS detectors in the LHC and an improvement of the leptonic mass insertion
bounds by more than five orders of magnitude would be possible.Comment: 20 pages, 5 figures, 4 table
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
- …