Session B9: Performance of Operating Detectors

Zero Degree Calorimeter for CMS at the LHC

The Zero Degree Calorimeter (ZDC) for the CMS experiment at the Large Hadron Collider is located between the incoming and outgoing beam lines at a distance of 140 m on each side of the interaction point. It measures primarily neutral particles that go in the direction of the original proton or heavy ion beam. With p-p reactions these are mostly neutrons produced by a charge exchange of the original proton. With heavy ion reactions the ZDC measures mostly spectator neutrons. The number of neutrons provides a measure of the amount of overlap of the interacting heavy ions. Over the last year the ZDC has collected data from p-p reactions at center of mass energies of 0.9, 2.36, and 7.0 TeV and Pb-Pb reactions at center of mass energies per nucleon pair of 2.75 TeV.   

The TPCs of the T2K experiment

The Tokai-to-Kamioka long baseline neutrino experiment (T2K) produces a beam of muon neutrinos in order to make precise measurements of neutrino mixing parameters in the atmospheric sector (${\Delta_m^2}_{23}$, $sin^2(\theta_{23})$) and possibly of $\theta_{13}$. In order to measure oscillation, the initial rate of neutrinos is sampled at the near detector (ND280) complex, which hosts three Time Projection Chambers (TPCs), integral to the reconstruction of neutrino events. The construction, successful operation and performance of these next-generation detectors will be presented.   

Longevity and Performance of the CDF Silicon Detector

In the last two years the integrated luminosity delivered by the Tevatron Collider at Fermilab increased dramatically from 5 to 10 fb$^{-1}$. The CDF Run II Silicon Detector has been long exposed to intense radiation exceeding the original detector design endurance of 3 fb$^{-1}$. It is a major challenge to the detector to keep high operational performance while facing aging effects. Aging effects are a common concern to the community of silicon detectors. Radiation damage effects, including type-inversion of the substrate and increase of the intrinsic noise, are carefully monitored. We present recent results of longevity studies including the evolution of the depletion voltage of sensors, the Signal-to-Noise ratio, and the efficiency as well as a summary of operational experience.   

The Fast Track Trigger upgrade for ATLAS

The Large Hadron Collider will soon operate at a center of mass energy of 14 TeV and at high instantaneous luminosities of the order of 10$^{34}$ and 10$^{35}$ interactions per second, per cm$^2$. The sheer rate of collisions, combined with data processing and storage limitations of approximately 100 per second lead to the enormous challenge of selecting which events will be saved for further processing. The Fast Track Trigger (FTK) is an upgrade to the ATLAS trigger system that will provide nearly a factor of 1000 reduction in the time needed to identify b quarks and tau leptons. This is particularly important because many new TeV-scale physics scenarios, as well as the Higgs boson searches, involve these particles. The efficient reconstruction of these particles at the trigger level will enable us to improve the experiment's sensitivity to these rare physics processes. In this talk, we will describe how the FTK system plans to operate, and how it will enable ATLAS to make smarter trigger decisions earlier in the trigger process. We will also discuss the current hardware design architecture and the challenges that the FTK team will face in the implementation of the system. FTK is an essential upgrade for ATLAS to reach its full potential for discovering new physics processes.   

Alignment of the ATLAS Inner Detector

ATLAS is a one of the four multipurpose experiments that records the products of the LHC proton-proton collisions at the LHC. The ATLAS Inner Detector is a charged particle tracking system built on two different technologies, silicon planar sensors (pixel and microstrips) and drift-tube based detectors, all embedded in a 2 T solenoidal field. The Inner Detector consists of $\sim$ 6000 modules in its Silicon Tracker combined with $\sim$ 350,000 channels in the straw tracker. The position of the devices after construction is known much less accuracy than their intrinsic resolution. A track based alignment procedure has been applied to better determine the absolute position of the sensitive devices. The alignment algorithms is based on minimization of the track-hit residuals and involves solving a linear system with a large number of degrees of freedom. We will present the status and performance of the ATLAS Inner Detector alignment system using the 2010 LHC run at 7 TeV. The alignment is performed combining isolated high pT collision tracks with cosmic ray tracks triggered during the empty LHC bunches. The alignment of the silicon subsystems had been performed at the module level, while the straw-tube tracker has been aligned at the channel level.   

Performance of the CMS Zero Degree Calorimeter's Electromagnetic Section

The crossing angle of the LHC beams at CMS assures the isolation of consecutive collisions and effects the luminosity of the beams. We have measured the crossing angle using the Zero Degree Calorimeter. This was achieved by finding the energy weighted mean position of electromagnetic clusters of energy. For this measurement the electromagnetic section of the ZDC was used. The hadronic section of the ZDC was employed to reject hadronic showers and thereby improve the measurement. In addition, we developed methods for removing events where secondary particles hit the photo-multiplier tubes directly. We will describe the techniques used in these measurements, and the performance of the Zero Degree Calorimeter.