59926691
Quasi-online data processing with the ALEPH event reconstruction facility:one year of total success
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.
122230572
A measurement of the ratio of longitudinal and transverse structure functions in neutrino interactions between 30 and 200 GeV
Abstract A new measurement of the ratio R = σ L / σ T of longitudinal and transverse structure functions in neutrino interactions on iron between 30 and 190 GeV neutrino energy is reported. The result is given as a function of the scale parameter x and the inelasticity ν of the interaction. The average value is R = 0.10 ± 0.07 around ν ≈ 50 GeV and is in accordance with a prediction from the QCD theory.
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Abstract Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented.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.
122204997
First measurement of the quark-to-photon fragmentation function
Earlier measurements at LEP of isolated hard photons in hadronic Z decays, attributed to radiation from primary quark pairs, have been extended in the ALEPH experiment to include hard photon productioninside hadron jets. Events are selected where all particles combine democratically to form hadron jets, one of which contains a photon with a fractional energyz≥0.7. After statistical subtraction of non-prompt photons, the quark-to-photon fragmentation function,D(z), is extracted directly from the measured 2-jet rate. By taking into account the perturbative contributions toD(z) obtained from anO(ααs) QCD calculation, the unknown non-perturbative component ofD(z) is then determined at highz. Provided due account is taken of hadronization effects nearz=1, a good description of the other event topologies is then found.
122188618
Charged particle pair production associated with a lepton pair in Z decays. indication of an excess in the tau channel
In a sample of 200 000 Z decays, events with two leptons and an additional pair of charged particles are studied. The 35 events found show a possible excess in the tau channel compared with the expectation from electroweak processes. The features of the events are consistent with radiation of virtual photons.
120575134
EUROFEL: Europe Tackles Key Issues of Free Electron Lasers
During the last few years Europe has made enormous progress towards free electron laser (FEL)-based research infrastructures. The FLASH facility [1] at DESY in Hamburg, Germany, has been in user operation since the summer of 2005; FERMI@Elettra [2] in Trieste, Italy, is under construction; the European XFEL [3] in Hamburg will start construction in summer 2008; and several other FEL projects are being prepared in France, Germany, Italy, Poland, Sweden, Switzerland and the UK. In addition, a number of dedicated test facilities have become available, including the photo-injector test facility (PITZ) [4] and the cryomodule test bench (CMTB) [5] at DESY, the HoBiCaT facility for testing superconducting cavities [6] at BESSY, Berlin, Germany, the SPARC facility [7] at INFN-LNF in Frascati, Italy, and the ERL Prototype (ERLP) [8] at Daresbury Laboratory, UK. They have been strongly supported by the national stakeholders in order to prepare the design of new FEL sources.
73548820
Microscopic investigation of RF surfaces of 3 GHz niobium accelerator cavities following RF processing
RF processing of superconducting accelerating cavities is achieved through a change in the electron field emission (FE) characteristics of the RF surface. We have examined the RF surfaces of several single-cell 3 GHz cavities, following RF processing, in a scanning electron microscope (SEM). The RF processing sessions included both high peak power (P/spl les/50 kW) pulsed processing, and low power (/spl les/20 W) continuous wave processing. The experimental apparatus also included a thermometer array on the cavity outer wall, allowing temperature maps to characterize the emission before and after RF processing gains. Multiple sites have been located in cavities which showed improvements in cavity behavior due to RF processing. Several SEM-located sites can be correlated with changes in thermometer signals, indicating a direct relationship between the surface site and emission reduction due to RF processing. Information gained from the SEM investigations and thermometry are used to enhance the theoretical model of RF processing.<<ETX>>
46669892
Superconducting RF system upgrade for short bunch operation of CESR
The CESR luminosity upgrade plan calls for shortening bunch length to 1 cm. Such bunch length can be achieved by installing two more superconducting cavities to increase total RF voltage. The RF system upgrade necessary to accommodate this change is discussed.
46912903
CATHODE INSERT DESIGN FOR SC RF GUNS
The cathode inserts in superconducting (SC) RF guns are normal conducting devices attached to a SC RF gun cavity. They enable the photocathode replacement and, at the same time, preserve high quality factor and high fields in the RF guns. However, the insert may also limit the gun performance because of multipacting etc. The experience gathered in early designs at Wuppertal [1], and, more recently at BNL [2] and HZDR [3] is taken into account. We consider the design structure of the cathode insert worked out by BINP for 1 cell prototype of SC HZDR RF gun [4]. The detailed electric, mechanic, and thermal calculations of the initial [4] and the upgraded design are presented in this paper.
55543619
Cryogenic Considerations for CW Operation of TESLA-type Superconducting Cavity Modules for the BESSY FEL ∗
The proposed BESSY FEL uses a CW superconducting driver linac to provide acceleration up to 2.3 GeV. Its design is based on TESLA cavity modules, originally intended for pulsed operation and heat loads of order 1 W/m at 2 K. CW operation increases this load to about 21 W/m for a total heat load of 3 kW. Presented here is an analysis of the cryogenic layout, including two-phase-flow simulations of the superfluid helium which help identify the changes needed for reliable CW operation. A modified “CW” module and helium distribution scheme is proposed.