Search

The Large Hadron Collider (LHC) at CERN - the most expensive and complex instrument mankind has ever built to address some of the most fundamental questions of Nature - is colliding proton-on-proton at high energy since November 2009. The full data set delivered by the LHC over the last 4 years has been analyzed by the ATLAS and CMS experiments in their pursuit of the Higgs boson, the particle responsible for generating masses for the basic building blocks of matter. In this article I discuss in detail the building and commissioning of the detector, search strategy and results obtained by the two experiments with special emphasis on ATLAS. [ABSTRACT FROM AUTHOR]

Abstract: Pixel detectors, as the current technology of choice for the innermost vertex detection, have reached a stage at which large detectors have been built for the LHC experiments and a new era of developments, both for hybrid and for monolithic or semi-monolithic pixel detectors is in full swing. This is largely driven by the requirements of the upgrade programme for the superLHC and by other collider experiments which plan to use monolithic pixel detectors for the first time. A review on current pixel detector developments for particle tracking and vertexing is given, comprising hybrid pixel detectors for superLHC with its own challenges in radiation and rate, as well as on monolithic, so-called active pixel detectors, including monolithic active pixels (MAPS) and DEPFET pixels for RHIC and superBelle. [Copyright &y& Elsevier]

For the ALICE experiment at the Large Hadron Collider (LHC) at CERN/Geneva, a high level trigger system (HLT) for online event selection and data compression has been developed and a computing cluster of several hundred dual-processor nodes is being installed. A major system integration test was carried out during the commissioning of the time projection chamber (TPC), where the HLT also provides a monitoring system. All major parts like a small computing cluster, hardware input devices, the online data transportation framework, and the HLT analysis could be tested successfully. A common interface for HLT processing components has been designed to run the components from either the online or offline analysis framework without changes. The interface adapts the component to the needs of the online processing and allows the developer to use the offline framework for easy development, debugging, and benchmarking. Following this approach, results can be compared directly. For the upcoming commissioning of the whole detector, the HLT is currently prepared to run online data analysis for the main detectors, e.g., the inner tracking system (ITS), the TPC, and the transition radiation detector (TRD). The HLT processing capability is indispensable for the photon spectrometer (PHOS), where the online pulse shape analysis reduces the data volume by a factor 20. A common monitoring framework is in place and detector calibration algorithms have been ported to the HLT. The paper describes briefly the architecture of the HLT system. It focuses on typical applications and component development. [ABSTRACT FROM AUTHOR]

The Compact Muon Solenoid (CMS) is a particle physics experiment situated on the Large Hadron Collider (LHC) at CERN, Switzerland. The CMS upgrade (planned for 2025) involves installing a new advanced sensor system within the CMS tracker, the centre of the detector closest to the particle collisions. The increased heat load associated with these sensors has required the design of an enhanced cooling system that exploits the latent heat of 40 bar CO2. In order to minimise interaction with the incident radiation and improve the detector performance, the cooling pipes within this system need to be thin-walled (~100 μm) and strong enough to withstand these pressures. The purpose of this paper is to analyse the microstructure and mechanical properties of thin-walled cooling pipes currently in use in existing detectors to assess their potential for the tracker upgrade. In total, 22 different pipes were examined, which were composed of CuNi, SS316L, and Ti and were coated with Ni, Cu, and Au. The samples were characterised using computer tomography for 3D structural assessment, focused ion beam ring-core milling for microscale residual stress analysis, optical profilometry for surface roughness, optical microscopy for grain size analysis, and energy dispersive X-ray spectroscopy for elemental analysis. Overall, this examination demonstrated that the Ni- and Cu-coated SS316L tubing was optimal due to a combination of low residual stress (20 MPa axial and 5 MPa hoop absolute), low coating roughness (0.4 μm Ra), minimal elemental diffusion, and a small void fraction (1.4%). This result offers a crucial starting point for the ongoing thin-walled pipe selection, development, and pipe-joining research required for the CMS tracker upgrade, as well as the widespread use of CO2 cooling systems in general. [ABSTRACT FROM AUTHOR]

Abstract: For the luminosity upgrade of the LHC, the SLHC, the tracking systems of the LHC experiments need to be replaced and upgraded. A main concern is the extreme radiation hardness requirements, up to 1×1016 cm−2. This paper describes recent results on the radiation hardening technologies developed within the CERN RD50 Collaboration for the LHC upgrade. Silicon detectors have been designed and produced on n- and p-type 4/6in. wafers made by Float Zone, epitaxy and Czochralski technology. Their charge collection efficiency after irradiation with protons, neutron and mixed irradiation has been studied. Novel detector concepts, as 3D detectors, have been designed, produced and studied as well. Radiation induced microscopic disorder has been also investigated in Si detectors with fluences up to 1016 cm−2 and correlated with the performance degradation of irradiated detectors. [ABSTRACT FROM AUTHOR]

Abstract: High resistivity and high oxygen concentration of silicon wafers can be beneficial for the radiation hardness of silicon detectors. Wafers of Magnetic Czochralski silicon (MCz-Si) can be grown with a resistivity of a few and with well-controlled, high oxygen concentration. According to the beam test results presented in this paper, n-type MCz-Si bulk, p-strip readout detectors with can be operated with acceptable signal-to-noise ratio up to the irradiation fluence of 1×1015 cm−2 1-MeV neutron equivalent. The improved radiation hardness compared to that of traditional p-in-n Float Zone silicon (p-in-n FZ-Si) detectors can be explained by better electric field distribution inside MCz-Si detectors. The difference between the distributions is clearly shown by Transient Current Technique (TCT) measurements, presented in this paper. Thus, strip detectors made on n-type MCz-Si are a feasible option for the outer tracker layers of the potential upgrade of the Large Hadron Collider (LHC), the Super-LHC. This corresponds approximately 95% of the total area of silicon detectors in the Super-LHC. [Copyright &y& Elsevier]