Status Report of the DPHEP Study Group: Towards a Global Effort for Sustainable Data Preservation in High Energy Physics
Data from high-energy physics (HEP) experiments are collected with significant financial and human effort and are mostly unique. An inter-experimental study group on HEP data preservation and long-term analysis was convened as a panel of the International Committee for Future Accelerators (ICFA). The group was formed by large collider-based experiments and investigated the technical and organisational aspects of HEP data preservation. An intermediate report was released in November 2009 addressing the general issues of data preservation in HEP. This paper includes and extends the intermediate report. It provides an analysis of the research case for data preservation and a detailed description of the various projects at experiment, laboratory and international levels. In addition, the paper provides a concrete proposal for an international organisation in charge of the data management and policies in high-energy physics.

title: Production of excited beauty states inZ decays
abstract: 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.

title: 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.

title: 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.

title: First measurement of the quark-to-photon fragmentation function
abstract: 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.

title: Charged particle pair production associated with a lepton pair in Z decays. indication of an excess in the tau channel
abstract: 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.

title: First Demonstration of Electron Beam Generation and Characterization with an All Superconducting Radio-frequency (SRF) Photoinjector
abstract: In preparation for a high brightness, high average current electron source for the energy recovery linac BERLinPro an all superconducting radio-frequency (SRF) photoinjector is now in operation at Helmholtz-Zentrum Berlin. The aim of this experiment is beam demonstration with a high brightness electron source able to generate short, few ps long pulse length electron bunches from a superconducting (SC) cathode film made of Pb coated on the backplane of a Nb SRF cavity. This paper describes the setup of the experiment, first results from beam measurements and capabilities of the source derived from beam dynamics considerations. In April 2011 the photoinjector generated and accelerated for the first time electron beam. This result marks the highlight of the project running for two years starting with project approval in May 2009.

title: SIMULTANEOUS LONG AND SHORT ELECTRON BUNCHES IN THE BESSY II STORAGE RING
abstract: We present first ideas of a scheme to develop BESSY II into a variable electron pulse length storage ring. The final goal is, to fill BESSY II with short bunches of 1.5 ps length (rms) and long bunches of 15 ps length simultaneously in the presently applied user optics. All insertion devices are operated as usual, i.e. the helical undulators and 7 T-field insertions. Long bunches of 1.5 mA current per bunch, twice the value of the present user optics, are filled in each second bucket. The other buckets can be filled with short bunches of up to 0.8 mA. The lower current value is required to avoid increase in the bunch length and bunch energy spread, predicted by scaling laws. The total current is e.g. limited by the HOM damping capabilities of the sccavities and the machine impedances. This scheme is achievable with recent developments in sc-rf cavity technology driven by requirements of high current cw applications like for the energy recovering linacs (ERLs). These developments seem to make it feasible to install high gradient HOM damped multi-cell cavities in electron storage rings. With an appropriate choice of the cavity resonance frequencies a beating of the effective longitudinal focusing voltage at the stable fixed points can be introduced and leads to different zero current bunch lengths. Basic parameters of this scheme are presented.

title: THE BESSY 2 nd -GENERATION SOFT X-RAY FEL USER FACILITY ∗
abstract: VUV-to-soft-X-ray FEL facilities promise to open fundamentally new frontiers for the synchrotron user community. So-called 2nd generation FELs, which use seeded schemes rather than SASE, an deliver reproducible ultrashort photon pulses in the GW range. BESSY has been designing a high-gain-harmonic-generation (HGHG) based FEL with a 2.3 GeV CW superconducting driver linac that covers photon energies from 24 eV to 1 keV. The design presented here provides full tuneability of photon energy, variable beam polarization and complete synchronization to external lasers—all essential for future femtosecond, time-resolved pump-probe experiments. In addition, CW operation offers the flexibility to tune the repetition rate and pulse pattern to the users’ needs.

title: The nature of field emission from microparticles and the ensuing voltage breakdown
abstract: In recent years there has been much progress in furthering our understanding of the sources of field emission as well as in tracing the stages from field emission to voltage breakdown. These advances come from microscopic studies (scanning electron microscopy, energy dispersive x-ray analysis, Auger spectroscopy) of field emitters located by DC high voltage scans as well as from field emitters found in microwave cavities. Craters, residues and starbursts found at breakdown sites reveal much about the physics of voltage breakdown. Both experiments and computer simulations show the important role played by gases generated by field emission induced heating.

title: Investigation of voltage breakdown caused by microparticles
abstract: Degradation of RF accelerating cavities caused by field emission currently limits the design of future linear accelerators. When field emission is the problem, foreign particles often deserve the blame, but they can be "processed" away if the cavity electric field is high enough to initiate voltage breakdown near the particle site, in which case the troublesome particle vaporizes, leaving behind a crater surrounded by a starburst-shaped feature. Severe cratering, however, erodes cavity surfaces to the point of significantly diminished acceleration capability. Breakdown events producing craters and starbursts. similar to those seen in RF cavities can also be incited by a DC electric field. After intentionally contaminating niobium and copper cathodes with different kinds of micron-sized particles, we used scanning electron microscopes with EDX and AES capabilities to obtain "before" and "after" pictures of particles that vaporized under DC electric fields between 30 and 150 MV/m.