Proceedings of the Second International Workshop on Eta Meson Physics

These are the proceedings of the Second International Workshop on Eta Meson Physics held in May 10-11, 2007, at the resort Peniscola in Spain. The workshop was focused on topics regarding eta and eta' -meson production and decays physics of common interest in the EU EtaMesonNet network.Comment: Each talk is represented by an extended abstract, 108 pages in tota

A pellet tracking system for hadron physics experiments

Frozen microspheres of hydrogen (pellets) are used as targets in the hadron physics experiment WASA (Forschungszentrum Jülich, Germany) [1] and will also be used in the future PANDA experiment at FAIR (GSI, Darmstadt, Germany) [2]. The interaction region is defined by the overlap of the pellet stream and the accelerator beam and has a size of a few millimeters. One would like to know the interaction point more precisely, to have better possibility to reconstruct particle tracks and events. One would also like to suppress background events that do not originate in a pellet, but e.g. may occur in residual gas in the beam pipe. A solution is provided by the presented pellet tracking system, for which a prototype [3] has been developed in Uppsala. The goal is to track individual pellets in order to know their position at the time of an interaction. The design of such a system, simulation techniques and results are presented

Low energy QCD and ChPT studies with KLOE

The KLOE experiment is situated at the φ factory DAΦNE in Frascati. φ radiative decays have been used to investigate the properties of the light scalar mesons f0(980)/a0(980), whose structure is still controversial. Off-peak data allow to investigate γγ interaction with a consequent scalar/pseudoscalar meson production. From the large sample of the η and η' produced in φ → ηγ decay we have studied several η and η' decays relevant to η/η' mixing, η' gluonium content, CP violation searches and tests of ChPT. For the hadronic cross section, the pion form factor in the Mππ invariant mass range (0.592–0.975) GeV has been determined and used in the evaluation of the hadronic contribution to the muon anomaly. The result confirms the 3-σ discrepancy between SM expectation and the measurement of the muon (g − 2) by the E821 experiment at the BNL

Dark currents studies with the Uppsala X-band Spectrometer at XBox test stand at CERN

Vacuum arcs is the phenomenon which limits the performance of normal conducting acceleratorcavities. It closely depends on electron field emission, which is consider a precursor for the creationof a vacuum discharge. These processes are still not fully understood, but we know that theydepend on the physical properties of the surfaces and bulk materials used in the acceleratorstructures. We need to come at these problems with a multidisciplinary approach, comprisingaccelerator, material and surface physics, for both experimental and theoretical analysis.The field emission current emitted during operation of the RF cavity is typically refer to as thedark current. Behavior of the dark current can give useful information about changes inside thestructure during conditioning and thus into the physics of the vacuum arcs. The Uppsala groupuses a magnetic spectrometer to look at the changes, both spatially on the screen and by measuringthe energy spectrum of the escaping electrons during conditioning of CLIC X-band structuresin dedicated high-power RF test stand at CERN. The spectrometer was originally designedto measure the electrons from the breakdown events with much higher intensities than the darkcurrent signals. In this paper we present the attempt to measure the dark current with the samesetup

Dark currents studies with the Uppsala X-band Spectrometer at XBox test stand at CERN

Vacuum arcs is the phenomenon which limits the performance of normal conducting acceleratorcavities. It closely depends on electron field emission, which is consider a precursor for the creationof a vacuum discharge. These processes are still not fully understood, but we know that theydepend on the physical properties of the surfaces and bulk materials used in the acceleratorstructures. We need to come at these problems with a multidisciplinary approach, comprisingaccelerator, material and surface physics, for both experimental and theoretical analysis.The field emission current emitted during operation of the RF cavity is typically refer to as thedark current. Behavior of the dark current can give useful information about changes inside thestructure during conditioning and thus into the physics of the vacuum arcs. The Uppsala groupuses a magnetic spectrometer to look at the changes, both spatially on the screen and by measuringthe energy spectrum of the escaping electrons during conditioning of CLIC X-band structuresin dedicated high-power RF test stand at CERN. The spectrometer was originally designedto measure the electrons from the breakdown events with much higher intensities than the darkcurrent signals. In this paper we present the attempt to measure the dark current with the samesetup

Spectrometers for RF breakdown studies for CLIC

A e+e- collider of several TeV energy will be needed for the precision studies of any new physics discovered atthe LHC collider at CERN.  One promising candidate is CLIC, a linear collider which is based on a two-beam acceleration scheme that efficiently solves the problem of power distribution to the acceleration structures. The phenomenon that currently prevents achieving highaccelerating gradients in high energy accelerators such asthe CLIC is the electrical breakdown at very high electrical field.The ongoing experimental work within the CLIC collaboration is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the discharges. In order to validate the feasibility of accelerating structures and observe the characteristics of the vacuum discharges and their eroding effects on the structure two dedicated spectrometers are now commissioned at the high-power test-stands at CERN. First, the so called Flashbox has opened up a possibility for non-invasive studies of  the emitted breakdown currents during two-beam acceleration experiments. It gives an unique possibility to measure the energy of electrons and ions in combination withthe arrival time spectra and to put that in context with accelerated beam, which is not possible at any of the other existing test-stands.The second instrument, a spectrometer for detection of the dark and breakdown currents, is operated at one of the 12 GHz stand-alone test-stands at CERN.  Built for high repetition rate operation it can measure the spatial and energy distributions of the electrons emitted from the acceleration structure during a single RF pulse. Two new analysis tools: discharge impedance tracking and tomographic image reconstruction, applied to the data from the spectrometer make possible for the first time to obtain the location of the breakdown inside the structure both in the transversal and longitudinal direction thus giving a more complete picture of the vacuum breakdown phenomenon