122041721
Production of excited beauty states inZ decays
AbstractA data sample of about 3.0 million hadronicZ decays collected by the ALEPH experiment at LEP in the years 1991 through 1994 is used to make an inclusive selection of B hadron events. In this event sample 4227±140±252B* mesons in the decayB*→Bγ and 1944±108±161B**u,d mesons decaying into a B meson and a charged pion are reconstructed. Here and in the followingB**u,d denotes the eightL=1(bū) and (bd) states and their charge conjugate.For the well establishedB* meson the following quantities are obtained:ΔM=MB*−MB=(45.30±0.35±0.87) MeV/c2 andNB*/(NB+NB*)=(77.1±2.6±7.0)%. The angular distribution of the photons in theB* rest frame is used to measure the relative contribution of longitudinalB* polarization states to beσL/(σL+σT)=(33±6±5)%.In theM(Bπ)−M(B) mass difference resonance structure is observed at (424±4±10) MeV/c2, for which the shape and position is consistent with the expectation forB**u,d states decaying intoB(*)π±. The relative production rate is determined to be
$$\begin{gathered} \frac{{BR(Z \to b \to B_{u,d}^{ * * } )}}{{BR(Z \to b \to B_{u,d} )}} \hfill \\ = [27.9 \pm 1.6(stat) \pm 5.9(syst) {}_{ - 5.6}^{ + 3.9} (model)]\% \hfill \\ \end{gathered} $$
 where the third error reflects the uncertainty due to different production and decay models for the broadB**u,d states.
119085485
Heavy quark tagging with leptons in the ALEPH detector
This paper deals with sustainable development policies in the French South-Eastern Alps region (Digne-les-Bains). It aims to delineate the influence of communication and mediation practices which are used to implement such principles in a largely reluctant area. This approach combines the point of views of two sciences, media and communication on the one hand, geography , on the other hand
120616150
Measurement of the neutral to charged current cross section ratios in neutrino and antineutrino nucleon interactions and determination of the Weinberg angle
AbstractThe cross section ratios of neutral and charged current interactions induced by neutrinos and antineutrinos in iron have been measured in the 200 GeV narrow-band beam at the CERN SPS. We findRv=0.301±0.007 andRv=0.363±0.015 for a hadron energy cut of 10 GeV. The results are in agreement with the standard model of electroweak interactions. In the
$$\overline {MS} $$
 renormalization scheme at the scale of theW boson mass
$$\sin ^2 \hat \theta _W \left( {m_W } \right) = 0.226 \pm 0.012$$
 is obtained, where the error represents the experimental uncertainty. The theoretical uncertainty is estimated to beΔsin2θW=±0.006.
120418219
Search for the Standard Model Higgs boson
Using a data sample corresponding to about 1 233 000 hadronic Z decays collected by the ALEPH experiment at LEP, the reaction has been used to search for the standard model Higgs boson, in association with missing energy when , or with a pair of energetic leptons when . No signal was found and, at the 95% confidence level, mH exceeds 58.4 GeV/c2.
118144238
Measurements of |V(cb)|, form-factors and branching fractions in the decays anti-B0 ---> D*+ lepton- anti-lepton-neutrino and anti-B0 ---> D+ lepton- anti-lepton-neutrino
Two samples of exclusive semileptonic decays, 579 events and 261 events, are selected from approximately 3.9 million hadronic Z decays collected by the ALEPH detector at LEP. From the reconstructed differential decay rate of each sample, the product of the hadronic form factor (ω) at zero recoil of the D(∗)+ meson and the CKM matrix element |Vcb| are measured to be , FD+(1)|Vcb| = (27.8 ± 6.8stat ± 6.5syst) × 10−3. The ratio of the form factors FD+(1) and is measured to be . A value of |Vcb| is extracted from the two samples, using theoretical constraints on the slope and curvature of the hadronic form factors and their normalization at zero recoil, with the result |Vcb| = (34.4 ± 1.6stat ± 2.3syst ± 1.4th) × 10−3. The branching fractions are measured from the two integrated spectra to be %, %.
123101518
Studies of quantum chromodynamics with the ALEPH detector
Abstract Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its flavour independence, tests of the SU(3) gauge structure of QCD, study of coherence effects, and measurements of single-particle inclusive distributions and two-particle correlations for many identified baryons and mesons.
36916632
Basic Concepts of Measurements Made on Superconducting RF Cavities
Presented here is an introduction to some of the concepts used in the tests performed on superconducting RF cavities in the SRF group at Cornell. It is intended for the 'novice' to this field and by no means attempts a rigorous derivation. Assumed is some previous exposure to the physics of waveguides and cavities. Explained is the concept of the Quality (Q) of a cavity, the coupling parameters and how these quantities are determined by experiment. Furthermore a short overview of the results obtained for a typical cell is presented.
56307984
FIRST RF TESTS IN THE HOBICAT SUPERCONDUCTING TEST FACILITY AT BESSY
In preparation for the construction of the BESSY-FEL User Facility, BESSY recently completed the installation of the HoBiCaT cryogenic test facility for superconducting RF (SRF) TESLA cavity units [1], including all ancillary devices (helium tank, input coupler, tuner, magnetic shielding). It is designed to house two such units in a configuration similar to that envisaged for the superconducting CW linac of the BESSY FEL. Commissioning of the facility is now complete and the first TTF-III RF coupler and cavity unit has been tested. In particular, the complete production, cleaning and assembly of the cavity unit was carried out by industry. These tests thus serve as a first step at qualifying industrial partners for series production of such systems, which will be essential for the future construction of SRF based light sources.
33237644
STARS - a two-stage high-gain harmonic generation FEL demonstrator
BESSY is proposing a demonstration facility, called STARS, for a two-stage high-gain harmonic generation free electron laser (HGHG FEL). STARS is planned for lasing in the wavelength range 40 to 70 nm, requiring a beam energy of 325 MeV and peak current of 500 A. The facility consists of a normal conducting gun, three superconducting TESLA-type acceleration modules modified for CW operation, a single stage bunch compressor and finally a two-stage HGHG cascaded FEL. This paper describes the faciliy layout and the rationale behind the operation parameters.
15393287
Explosive field emitter processing in superconducting rf cavities
Superconducting niobium radiofrequency cavities for e + e accelerators presently are limited to accelerating gradients of 25 MV/m — far less than their theoretical capability of 50 MV/m. Field emission presents the main impediment to higher gradients. In many cases, in situ high-pulsed-power processing is used to explode emission sites (rf processing), thereby improving the cavity performance. Thermometric and microscopic results summarized here are used to develop a qualitative theory of the events leading up to rf processing. It is demonstrated that the ionization of gases from the emitter is crucial to the initiation of the explosion, similar to past observations made with dc emitters. This fact is underscored by the examination of emitters processed with intentionally administered helium gas in the cavity (helium processing). Numerical simulations of rf processing, including the ionization of gases by the field emission current, illustrate the conditions required for emitter explosion, and they confirm the importance of a plasma during such events. Most importantly, the calculations demonstrate that the positive space charge of the ions enhances the field emission current, and that the production of ions is a self amplifying process. A runaway situation can ensue, which explains the submicrosecond rf processing times observed experimentally. The rapid release of monolayer surface adsorbates at the emission site, in particular, can play a critical role in initiating voltage breakdown.
648097
Adapting TESLA technology for future cw light sources using HoBiCaT.
The HoBiCaT facility has been set up and operated at the Helmholtz-Zentrum-Berlin and BESSY since 2005. Its purpose is testing superconducting cavities in cw mode of operation and it was successfully demonstrated that TESLA pulsed technology can be used for cw mode of operation with only minor changes. Issues that were addressed comprise of elevated dynamic thermal losses in the cavity walls, necessary modifications in the cryogenics and the cavity processing, the optimum choice of operational parameters such as cavity temperature or bandwidth, the characterization of higher order modes in the cavity, and the usability of existing tuners and couplers for cw.