Development of a GEM-TPC prototype

The use of GEM foils for the amplification stage of a TPC instead of a con- ventional MWPC allows one to bypass the necessity of gating, as the backdrift is suppressed thanks to the asymmetric field configuration. This way, a novel continuously running TPC, which represents one option for the PANDA central tracker, can be realized. A medium sized prototype with a diameter of 300 mm and a length of 600 mm will be tested inside the FOPI spectrometer at GSI using a carbon or lithium beam at intermediate energies (E = 1-3AGeV). This detector test under realistic experimental conditions should allow us to verify the spatial resolution for single tracks and the reconstruction capability for displaced vertexes. A series of physics measurement implying pion beams is scheduled with the FOPI spectrometer together with the GEM-TPC as well.Comment: 5 pages, 4 figures, Proceedings for 11th ICATTP conference in como (italy

Meson Spectroscopy and Search for Spin-Exotic States at COMPASS

This paper presents the results of a partial wave analysis of about 420 000 diffractive dissociation events with four-momentum transfer $t'\in$ [0.1, 1] GeV$^{2}/c^{2}$. The data were recorded at COMPASS during a short pilot run in 2004, using a 190GeV$/c$ negative pion beam on lead targets. Reactions of the type $\pi^{-}N\rightarrow\pi^{-}\pi^{-}\pi^{+}N'$ have been investigated and resonances up to 2.5 GeV$/c^{2}$ have been searched for. In addition to well-known mesons, also a state with spin-exotic quantum numbers $J^{PC} =$ 1$^{−+}$ is observed

Meson production from diffractive pion dissociation at COMPASS

Diffractive dissociation reactions at COMPASS provide clean access to mesons with masses below $\approx$ 2.5GeV$/c^{2}$. This paper presents a partial wave analysis of about 420 000 $\pi^{-}Pb\rightarrow\pi^{-}\pi^{-}\pi^{+}Pb$ events at 190 GeV$/c$ beam momentum and with four-momentum transfer $t'\in$ [0.1, 1] GeV$^{2}/c^{2}$. The well-known $a_{1}$(1260), $a_{2}$(1320) and $\pi_{2}$(1670) mesons are resolved with high quality. Also the less established states $\pi$(1800) and $a_{4}$(2040) are seen. In addition, a resonance in the spin-exotic $J^{PC} =$ 1$^{−+}$ wave is observed. A mass-dependent fit results in a mass and width of 1.660$^{+0.010}_{−0.074}$ and 0.269$^{+0.063}_{−0.085}$ GeV$/c^{2}$, respectively, which is consistent with the disputed hybrid candidate $\pi_{1}$(1600)

Design and testing of long Flexible Printed Circuits for the ATLAS High Granularity Timing Detector demonstrator

The High Granularity Timing Detector for the ATLAS upgrade is under construction to meet the challenges of the HL-LHC. In order to connect a module, the basic detector element, to the surrounding peripheral electronic board, a flexible printed circuit (FPC) is used as an interconnection for data transmission and power distribution. An identical design for all FPCs is required except for their length, depending on the module position on the detector active area. The design and qualification of a preliminary FPC version, manufactured in 13 different lengths (from 28.5 to 73.2$~$cm), are presented

Geiger-mode avalanche photodiodes as photodetectors in Cherenkov astronomy

The progress in the development of Geiger-mode avalanche photodiodes (G-APD) has resulted in devices which show great promise for Imaging Atmospheric Cherenkov Telescopes (IACT). In the course of the First G-APD Camera Test (FACT) project with the purpose to construct a G-APD based camera, their characteristics are analysed and measured in detail. The angle dependence of the photon detection efficiency was measured and found to be flat. The effects of saturation and cross-talk on the reconstruction of the number of detected photons was studied. Since these effects are of a statistical nature, the reconstructed number is limited in its precision. For small numbers of photons, crosstalk is the limiting factor. For photon numbers comparable to or higher than the number of cells of the G-APD, the main limitation is the saturation

The P2 experiment

This article describes the future P2 parity-violating electron scattering facility at the upcoming MESA accelerator in Mainz. The physics program of the facility comprises indirect, high precision search for physics beyond the Standard Model, measurement of the neutron distribution in nuclear physics, single-spin asymmetries stemming from two-photon exchange and a possible future extension to the measurement of hadronic parity violation. The first measurement of the P2 experiment aims for a high precision determination of the weak mixing angle to a precision of 0.14% at a four-momentum transfer of Q^2 = 4.5 10^{-3} GeV^2. The accuracy is comparable to existing measurements at the Z pole. It comprises a sensitive test of the standard model up to a mass scale of 50 TeV, extendable to 70 TeV. This requires a measurement of the parity violating cross section asymmetry -39.94 10^{-9} in the elastic electron-proton scattering with a total accuracy of 0.56 10^-9 (1.4 %) in 10,000 h of 150 \micro A polarized electron beam impinging on a 60 cm liquid H_2 target allowing for an extraction of the weak charge of the proton which is directly connected to the weak mixing angle. Contributions from gamma Z-box graphs become small at the small beam energy of 155 MeV. The size of the asymmetry is the smallest asymmetry ever measured in electron scattering with an unprecedented goal for the accuracy. We report here on the conceptual design of the P2 spectrometer, its Cherenkov detectors, the integrating read-out electronics as well as the ultra-thin, fast tracking detectors. There has been substantial theory work done in preparation of the determination of the weak mixing angle. The further physics program in particle and nuclear physics is described as well.Comment: Invited EPJ A Manuscript, many figures, large file siz