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.
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.
26322213
A study of Bose-Einstein correlations ine+e− annihilation at 91 GeV
This paper describes a study of Bose-Einstein correlations made using the ALEPH detector at LEP. The correlations are found to enhance the two particle differential cross section for pairs of identical pions by a factor which can be roughly parametrized byR(Q)=1+λ exp(-Q2σ2), whereQ is the difference in the 3-momenta of the two pions in their centre of mass frame, λ=0.51±0.04±0.11 and σ=3.3±0.2±0.8 GeV−1, which corresponds to a source size of 0.65±0.04±0.16 fm. The large systematic errors on these results reflect their strong dependence on the choice of the reference sample used in the analysis. This problem is believed to occur primarily because of uncertainties in the rates of resonance production and a lack of knowledge about the pion-pion strong interaction. No significant correlations are seen amongst like-charged pion-kaon pairs.
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.
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.
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.
55994461
FIRST CHARACTERIZATION OF A FULLY SUPERCONDUCTING RF PHOTOINJECTOR CAVITY
As a first step towards a high brightness, high average current electron source for the BERLinPro ERL a fully superconducting photo-injector was developed by HZB in collaboration with JLab, DESY and the A. Soltan Institute. This cavity-injector ensemble is made up of a 1.6-cell superconducting cavity with a superconducting lead cathode deposited on the half-cell backwall. A superconducting solenoid is used for emittance compensation. This system, including a diagnostics beamline, has been installed in the HoBiCaT facility to serve as a testbed for beam dynamics studies and to test the combination SRF cavity and superconducting solenoid. This paper summarizes the characterization of the cavity in this configuration including Q measurements, dark current tests and field-stability analyses.
137672120
The 'Q disease' in superconducting niobium RF cavities
Superconducting niobium cavities can achieve quality (Q0) factors of 1010–1011, more than six orders of magnitude higher than conventional copper cavities. However, to maintain this performance at high accelerating gradient (20 MV/m) the radio‐frequency (rf) surface must be damage and dust free. Cavity preparation techniques therefore routinely include a chemical etch or electropolishing. Under certain conditions, these (and other) treatments can contaminate the niobium with hydrogen. Hydrides may then form when the cavity is cooled through 150 K, even if only a few atomic percent hydrogen are present. If hydrides are formed, the cavity quality can degrade substantially (Q disease). A rapid cooldown often inhibits the hydride formation. Other “cures” include degassing cavities at 900 °C to eliminate the hydrogen. A historical review of the Q disease is provided here, with the emphasis being placed on its discovery, symptoms, mechanism, and cures.
121235219
Start to end simulations for the BESSY FEL project
Abstract BESSY plans to construct a FEL multi user facility for the Soft-X-Ray spectral range from 20 eV to 1 keV . Central part of the project is a superconducting linac, based on the TESLA technology but operating in CW mode. A photo injector and a bunch compression scheme is introduced, allowing to reach the required electron beam parameters at the undulators beginning: up to 4 kA peak current ( 1 nC bunch charge), 1.5π mm mrad normalized transverse emittance and an energy spread below 1%. Extensive Start to End (S2E) simulations have been performed, using the programs ASTRA for the injector part, ELEGANT for the linac and bunch compression studies and GENESIS for the FEL process. Results of these simulations are presented and discussed.
46074015
Dark current measurements on a superconducting cavity using a cryogenic current comparator.
This paper presents nondestructive dark current measurements of tera electron volt energy superconducting linear accelerator cavities. The measurements were carried out in an extremely noisy accelerator environment using a low temperature dc superconducting quantum interference device based cryogenic current comparator. The overall current sensitivity under these rough conditions was measured to be 0.2 nA/Hz(1/2), which enables the detection of dark currents of 5 nA.
111052021
SUPERCONDUCTING ACCELERATOR MODULES FOR STORAGE RINGS AND SYNCHROTRONS
We report on the production status of 6 superconducting 500 MHz accelerating modules (2 for Cornell University for upgrading CESR, 2 for the Taiwan Light Source and two for the Canadian Light Source). We focus on the test results on cavities and RF windows. The superconducting 500 MHz cavities fully prepared and assembled at ACCEL reached 12 MV/m accelerating gradient during cold vertical RF test on a regular basis. The assembly of the first module is almost completed. The cold RF test of this first module at Cornell is scheduled for June this year.[1]