Overview and Electronics Needs of ATLAS and CMS High Luminosity Upgrades

The LHC will begin collisions in Spring 2009, and build up to nominal luminosity (1.0 × 10^34 cm^?2 s^?1 over the next few years. This will be followed by a continuos programme of im- provements leading eventually to a ten-fold increase above nom- inal with the super-LHC (sLHC). Within a few years of opera- tion, the LHC experiments should discover or rule out a Stan- dard Model (SM) Higgs, and could find supersymmetric parti- cles if they exist below about 1.5 TeV mass. Several other dis- coveries are possible. However detailed knowledge of any new particles will be needed to understand exactly what the physics behind them is. Large data sets will be needed for this; these will also allow the mass limits for discovery of new particles to be increased. Upgrades to the general purpose experiments ATLAS and CMS will be needed to deliver these large data sets with good performance. This paper presents some of the physics goals of the upgrade, LHC machine plans, the schedule, and summarises the changes and challenges for the detectors at the sLHC

Benchmarking the Particle Background in the Large Hadron Collider Experiments

Background benchmarking measurements have been made to check the low-energy processes which will contribute via nuclear reactions to the radiation background in the LHC experiments at CERN. Previously these processes were only evaluated with Monte Carlo simulations, estimated to be reliable within an uncertainty factor of 2.5. Measurements were carried out in an experimental set-up comparable to the shielding of ATLAS, one of the general-purpose experiments at LHC. The absolute yield and spectral measurements of photons and neutrons emanating from the final stages of the hadronic showers were made with a Bi_4Ge_3O_{12} (BGO) detector. The particle transport code FLUKA was used for detailed simulations. Comparison between measurements and simulations show that they agree within 20% and hence the uncertainty factor resulting from the shower processes can be reduced to a factor of 1.2

Rate effects in high-resolution drift chambers

The impact of high counting rates on the spatial resolution of cylindrical drift tubes is investigated in detail and the results are compared with simulations. Electronics effects and space-charge effects are quantitatively analysed. A spatial resolution of $\sigma < 80\,\mu\mathrm{m}$ can be achieved even at rates as high as 1500\,Hz/cm wire length (300\,kHz per wire)

Resolution limits of drift tubes

Measurements of the drift-tube response to charged particle tracks are compared with a complete simulation. The measured resolution of typically 80\,$\mu$m agrees well with the simulation and allows the individual factors limiting the resolution such as diffusion, charge deposit fluctuations, gas gain fluctuations and signal processing to be studied. The results with respect to the dependence of the drift chamber resolution on gas gain, gas pressure and electronics parameters are reported

Front-end electronics for drift tubes in a high-rate environment

A front-end electronics readout for drift tubes in a high-rate environment is presented. This system allows us to encode several pieces of information (leading edge time, trailing edge time, signal charge and piled-up hits from multiple tracks) into a single readout channel that is presented to the TDC. The advantage of active baseline restoration compared to bipolar signal shaping is discussed

Dependence of Drift Tube Performance on the Anode Wire Diameter

Cylindrical pressurized drift tubes with different anode wire diameters wereoperated in a 170~GeV muon test beam. The dependences of spatialresolution, efficiency and streamer probability on the anode wirediameter were measured. The resolution measurements are compared with a simulation

A facility for the test of large area muon chambers at high rates

Operation of large area muon detectors at the future Large Hadron Collider (LHC) will be characterized by large sustained hit rates over the whole area, reaching the range of kHz/\scm. We describe a dedicated test zone built at CERN to test the performance and the aging of the muon chambers currently under development. A radioactive source delivers photons causing the sustained rate of random hits, while a narrow beam of high energy muons is used to directly calibrate the detector performance. A system of remotely controlled lead filters serves to vary the rate of photons over four orders of magnitude, to allow the study of performance as a function of rate

The performance of GridPix detectors

A GridPix detector is a gaseous detector capable of detecting individual single primary electrons from ionizing particles. Such a detector consists of a pixel chip as active anode covered with a thin layer of silicon rich silicon nitride (SiRN) for protection against discharges, an integrated amplification grid (InGrid), applied on top of the chip by wafer post processing techniques, and a cathode plane. The drift region is between the grid and cathode while the gas gain occurs between the chip and the grid. The discharge quenching properties of the SiRN layer have been determined as well as the relation on grid capacitance, grid voltage and gas mixture. Part of the detectors in this report were of the type Gossip, a GridPix detector with a drift gap of ∼1 mm. Using such thin drift layer, one may consider this detector as a replacement for a silicon pixel detector. The performance of three Gossip detectors has been investigated by measurements in a test beam at CERN

The ATLAS SCT grounding and shielding concept and implementation

This paper presents a complete description of Virgo, the French-Italian gravitational wave detector. The detector, built at Cascina, near Pisa (Italy), is a very large Michelson interferometer, with 3 km-long arms. In this paper, following a presentation of the physics requirements, leading to the specifications for the construction of the detector, a detailed description of all its different elements is given. These include civil engineering infrastructures, a huge ultra-high vacuum (UHV) chamber (about 6000 cubic metres), all of the optical components, including high quality mirrors and their seismic isolating suspensions, all of the electronics required to control the interferometer and for signal detection. The expected performances of these different elements are given, leading to an overall sensitivity curve as a function of the incoming gravitational wave frequency. This description represents the detector as built and used in the first data-taking runs. Improvements in different parts have been and continue to be performed, leading to better sensitivities. These will be detailed in a forthcoming paper

Hyperon weak radiative decays in chiral perturbation theory

We investigate the leading-order amplitudes for weak radiative decays of hyperons in chiral perturbation theory. We consistently include contributions from the next-to-leading order weak-interaction Lagrangian. It is shown that due to these terms Hara's theorem is violated. The data for the decays of charged hyperons can be easily accounted for. However, at this order in the chiral expansion, the four amplitudes for the decays of neutral hyperons satisfy relations which are in disagreement with the data. The asymmetry parameters for all the decays can not be accounted for without higher-order terms. We shortly comment on the effect of the 27-plet part of the weak interaction.Comment: 8 pages of REVTeX and using macro-package "feynman.tex" (available at http://xxx.lanl.gov/ftp/hep-ph/papers/macros) for the 2 figure