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For C3, some 2000 accelerator modules must be 5D positioned, within 10 µm transversal, on a 2.3 km long straight line, for both linacs. In the Rasnik alignment system, light from a point-like monochromatic source falls on a zone lens, forming a Fraunhofer diffraction pattern on an image pixel sensor. The alignment of three objects can be obtained by analyzing the position of the diffraction pattern on the sensor. The alignment of a large number of objects can be realized by fixing a stick on each object, carrying all three Rasnik components. With this leap frog geometry, all sticks are mutually coupled, forming a multipoint alignment system. The system should operate in ambient air, in vacuum, and in liquid nitrogen. Due to the heat dissipation of these components, bubbles are formed, causing an error in the measured alignment when crossing the optical path. Various methods of beam shielding are presented. With the Quarter Cryo Module (QCM), essential studies will be carried out, enabling the realization of C3. The QCM will be equipped with four Rasnik chains, measuring alignment parameters with redundancy. In addition, the bubble-induced vibrations of the accelerator components can be registered accurately.

The Gossip detector, being a GridPix TPC equipped with a thin layer of gas, is a promising alternative for Si tracking detectors. In addition, GridPix would be an interesting way to read out the gaseous phase volume of bi-phase Liquid Xe cryostats of v-less double beta decay and rare event (i.e. WIMP) search experiments.

A bstract This paper presents a measurement of the double-differential cross section for the Drell-Yan Z/γ ∗ → ℓ + ℓ − and photon-induced γγ → ℓ + ℓ − processes where ℓ is an electron or muon. The measurement is performed for invariant masses of the lepton pairs, m ℓℓ , between 116 GeV and 1500 GeV using a sample of 20 . 3 fb −1 of pp collisions data at centre-of-mass energy of s = 8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented double differentially in invariant mass and absolute dilepton rapidity as well as in invariant mass and absolute pseudorapidity separation of the lepton pair. The single-differential cross section as a function of m ℓℓ is also reported. The electron and muon channel measurements are combined and a total experimental precision of better than 1% is achieved at low m ℓℓ . A comparison to next-to-next-to-leading order perturbative QCD predictions using several recent parton distribution functions and including next-to-leading order electroweak effects indicates the potential of the data to constrain parton distribution functions. In particular, a large impact of the data on the photon PDF is demonstrated.

A bstract A search for the exclusive decays of the Higgs and Z bosons to a ϕ or ρ meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of up to 35 . 6 fb −1 collected at s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. These decays have been suggested as a probe of the Higgs boson couplings to light quarks. No significant excess of events is observed above the background, as expected from the Standard Model. Upper limits at 95% confidence level were obtained on the branching fractions of the Higgs boson decays to ϕ γ and ρ γ of 4 . 8 × 10 −4 and 8 . 8 × 10 −4 , respectively. The corresponding 95% confidence level upper limits for the Z boson decays are 0 . 9 × 10 −6 and 25 × 10 −6 for ϕ γ and ρ γ, respectively.

For C 3 , some 2000 accelerator modules must be 5D positioned, within 10 µm transversal, on a 2.3 km long straight line, for both linacs. In the Rasnik alignment system, light from a point-like monochromatic source falls on a zone lens, forming a Fraunhofer diffraction pattern on an image pixel sensor. The alignment of three objects can be obtained by analyzing the position of the diffraction pattern on the sensor. The alignment of a large number of objects can be realized by fixing a stick on each object, carrying all three Rasnik components. With this leap frog geometry, all sticks are mutually coupled, forming a multipoint alignment system. The system should operate in ambient air, in vacuum, and in liquid nitrogen. Due to the heat dissipation of these components, bubbles are formed, causing an error in the measured alignment when crossing the optical path. Various methods of beam shielding are presented. With the Quarter Cryo Module (QCM), essential studies will be carried out, enabling the realization of C 3 . The QCM will be equipped with four Rasnik chains, measuring alignment parameters with redundancy. In addition, the bubble-induced vibrations of the accelerator components can be registered accurately.

The industrial production of monolithic GridPix pixel chips for the digital readout of primary electrons in a TPC is under study at IZM-Fraunhofer, Berlin. With future low-cost chips, new applications are foreseen in TPCs for bi-phase Ar/Xe dark matter experiments, and for v-less double beta decay experiments.

We have developed the gaseous GridPix detector quad made from four Timepix3 chips. To provide the required charge amplification a Micromegas-like grid has been deposited on the chip surface by MEMS technology. The grid holes are precisely aligned to the chip pixels and have a pitch of 55 μm while the high time resolution of 1.56 ns of the Timepix3 chip enables the precise reconstruction of each individual primary ionization electron in the detector gas. The chip is coated by a high resistivity protection layer to prevent damage by unavoidable discharges. Using the GridPix technology, the full position of the ionization cloud is measured. As such the ultimate resolution of a gaseous detector is achieved, mainly limited by diffusion. The quad has all services located under the detection surface. Multiple quads can be simply joined together to create a large readout plane of a TPC. In this paper we show details about the construction of the quad and the preliminary results from a recent test beam experiment at the ELSA electron beam facility in Bonn.