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Many scientific disciplines ranging from physics, chemistry and biology to material sciences, geophysics and medical diagnostics need a powerful X-ray source with pulse lengths in the femtosecond range 1-4. This would allow, for example, time-resolved observation of chemical reactions with atomic resolution. Such radiation of extreme intensity, and tunable(More)
Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL(More)
The Photo Injector Test facility at DESY, Zeuthen site (PITZ), is dedicated to develop and optimize high brightness electron sources for short wavelength Free-Electron Lasers (FELs) like FLASH and the European XFEL, both in Hamburg (Germany). Since October 2009 a major upgrade is ongoing with the goal to improve the accelerating components, the photocathode(More)
The four-jet nal state is analyzed to search for hadronic decays of pair-produced heavy particles. The analysis uses the ALEPH data collected at LEP in November 1995 at centre-of-mass energies of 130 and 136 GeV, corresponding to a total integrated luminosity of 5.7 pb ?1. An excess of four-jet events is observed with respect to the standard model(More)
This paper presents the behavior of the TTF2 RF gun with long RF pulses (up to 900 µs), high peak power (up to 3 MW) and high repetition rate (up to 10 Hz). The experiments have been realized at the Photo Injector Test Facility of DESY Zeuthen from January to March 2003, where the RF gun has been tested prior to its installation at DESY Hamburg on the TTF2(More)
A lower limit is set on the B 0 s meson oscillation parameter m s using data collected from 1991 to 1994 by the ALEPH detector. Events with a high transverse momentum lepton and a reconstructed secondary vertex are used. The high transverse momentum leptons are produced mainly by b hadron decays, and the sign of the lepton indicates the(More)
From approximately 3 million hadronic decays of Z bosons recorded with the aleph detector at lep, a sample of 410 32 B 0 ! D + ` ? ` candidates is selected, wherè is either an electron or a muon. The diierential decay rate d?(B 0 ! D + ` ? `)=d! from this sample is tted, yielding a value for the product of the CKM matrix element jV cb j and the(More)
Four-fermion events have been selected in a data sample of 5.8 pb ?1 collected with the aleph detector at centre-of-mass energies of 130 and 136 GeV. The nal states`+`? q q, ` + ` ? ` + ` ? , q q, and`+`? have been examined. Five events are observed in the data, in agreement with the Standard Model predictions of 6:67 0:38 events from four-fermion processes(More)