7,755 research outputs found
Measurement of the tau lepton lifetime with Beta A Beta AR
No full textThe mean lifetime of the tau lepton is measured from the decay length distribution of 3-prong tau decays from e(+) e(-) collisions at the &UUpsilon;(4S) resonance. A data sample of 80.0 fb(-1) collected with the BABAR detector at the PEP-II B Factory is used for this measurement. The measured tau lifetime is: τ(-) = 289.40 ± 0.91 (stat.) ± 0.90 (syst.) fs. All the results are preliminary
Experimental Review on Lepton Universality and Lepton Flavour Violation tests at the B-factories
No full textSince 1999, the B-factories collaborations BABAR and Belle have accumulated
and studied large samples of tau lepton pairs. The experimental results on
Lepton Universality checks and Lepton Flavour Violation searches are reported.Comment: 11 pages, 2 figures, 1 table (To be sumitted to the proceedings of
the Kaon International Conference 2007
Measurement of , , and , by
No full textWe report preliminary measurements of the branching fractions of the decays τ− → K−nπ0 ντ (n = 0, 1, 2, 3) and τ− → π−nπ0 ντ (n = 3, 4), excluding the contributions that proceed through the decay of intermediate K0 and η mesons. The measurements are based on a data sample of 435 million τ pairs produced in e+ e− collisions at and near the Υ (4S) peak and collected with the BABAR detector in 1999-2008. The measured branching fractions are B(τ− → K−ντ ) = (7.174 ±0.033 ±0.213) × 10−3, B(τ− → K−π0 ντ ) = (5.054 ±0.021 ±0.148) × 10−3, B(τ− → K−2π0 ντ ) = (6.151 ± 0.117 ± 0.338) × 10−4, B(τ− → K−3π0 ντ ) = (1.246 ± 0.164 ± 0.238) × 10−4, B(τ− → π−3π0 ντ ) = (1.168 ± 0.006 ± 0.038) × 10−2, B(τ− → π−4π0 ντ ) = (9.020 ± 0.400 ± 0.652) × 10−4, where the first uncertainty is statistical and the second one systematic
Improved determination of with decays
No full textThe HFLAV end 2018 t branching fractions fit results and FLAG 2019 lattice QCD results are used to compute updated |Vus| determinations using recently published radiative corrections for(equation presented)
HFAG 2016 and PDG 2016 tau lepton averages and |Vus| determination from tau data
No full textThe HFAG-Tau sub-group has performed in 2016 two similar global fits on the tau lepton branching fractions measurements. One, unitarity constrained, has been published in the 2016 edition of the Review of Particle Physics [1] and a second one, without the unitarity constraint, is currently preliminary and is expected to be published soon on the HFAG 2016 report [2]. The resulting r branching fractions are used to test the Standard Model lepton universality predictions and to measure the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V-us vertical bar
Results in online data processing with the data acquisition system of the ALEPH TPC
No full textSince August 1989 the ALEPH detector is collecting data on e+e- collisions provided by the LEP storage ring at CERN. Its main tracking detector, a time projection chamber, has about 50,000 channels, each recording 512 samples of incoming ionization. The ALEPH TPC data acquisition system is based on 768 triple width Fastbus modules, named TPDs, and 36 double width Fastbus modules, named TPPs. The TPC DAQ system performance has been satisfactory since the beginning of LEP physics in 1989, throughout more than two years of operation. The task to coordinate, to reliably operate, to monitor and to maintain several hundreds of complex custom hardware devices has been accomplished. In this paper the performance and the implementation of the TPC DAQ system are presented; furthermore, it is shown how online data processing is used to obtain a substantial reduction of the data volume
Process to Process Communication over Fastbus in the Data Acquisition System of the ALEPH TPC
No full textThe data acquisition system of the ALEPH TPC includes a VAX/VMS computer cluster and 36 intelligent Fastbus modules (ALEPH TPPs) running the OS9 multitasking real-time operating system. Dedicated software has been written in order to reliably exchange information over Fastbus between the VAX/VMS cluster and the 36 TPPs to initialize and co-ordinate the microprocessors, and to monitor and debug their operation. The functionality and the performance of this software will be presented together with an overview of the applications that rely on it
Tau physics results from BABAR
No full textSince 1999, the BABAR collaboration has accumulated and studied large samples of tau lepton pairs. The main physics results are reported
Measurement of the B0 to D∗− π+ π+ π− branching fraction by BABAR
No full textThe BaBar collaboration measured the decay branching fraction Br(B0→D∗−π+π−π+)=(7.26±0.11(stat.)±0.31(syst.))×10−3Br(B0→D∗−π+π−π+)=(7.26±0.11(stat.)±0.31(syst.))×10−3 using a sample of (470.9±2.8)×106 BB ̄ ̄ ̄(470.9±2.8)×106 BB ̄ pairs. This measurement will facilitate the measurement of Br(B0→D∗−τ+ντ)Br(B0→D∗−τ+ντ) with τ+→π+π−π+ν ̄ ̄ ̄ττ+→π+π−π+ν ̄τ at hadronic colliders, improving the experimental precision on the normalization branching fraction Br(B0→D∗−π+π−π+)Br(B0→D∗−π+π−π+)
Search for dark photon and long-lived particles at BaBar
No full textThe complete large and clean sample of e+ e- collisions recorded by the BaBar detector at PEPTI at the SLAC National Laboratory was used to search for a photon-like particle with mass and decaying into an e+ e- or μ+ μ- pair, which is proposed in some Dark Matter theory models, and to search for a long-lived particle that decays into an oppositely charged fermion pair, predicted in a number of New Physics models. We do not observe a significant signal and we set 90% confidence level upper limits of several production rates and on the parameters of some proposed New Physics models
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