R. Eusebi

Beam test results of the radiation tolerance study of chemical vapour deposition (CVD) diamond against different particle species and energies is presented. We also present beam test results on the independence of signal size on incident particle rate in charged particle detectors based on un-irradiated and irradiated poly-crystalline CVD diamond over a range of particle fluxes from 2 kHz/cm2 to 10 MHz/cm2. The pulse height of the sensors was measured with readout electronics with a peaking time of 6 ns. In addition functionality of poly-crystalline CVD diamond 3D devices was demonstrated in beam tests and 3D diamond detectors are shown to be a promising technology for applications in future high luminosity experiments.

This paper studies the pair production of the doubly charged Higgs boson of the left-right symmetric models using multilepton final state in the vector boson fusion (VBF)-like processes. The study is performed in the framework consistent with the model's correction to the standard model $\rho_{EW}$ parameter. VBF topological cuts, number of leptons in the final state and $p_T$ cuts on the leptons are found to be effective in suppressing the background. Significant mass reach can be achieved for exclusion/discovery of the doubly charge Higgs boson for the upcoming LHC run with a luminosity of $\mathcal{O}(10^3)$ fb$^{-1}$.

With the commissioning of the LHC in 2010 and upgrades expected in 2015, ATLAS and CMS are planning to upgrade their innermost tracking layers with radiation hard technologies. Chemical Vapor Deposition diamond has been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of BaBar, Belle, CDF and all LHC experiments. This material is now being considered as a sensor material for use very close to the interaction region where the most extreme radiation conditions exist. Recently the RD42 collaboration constructed, irradiated and tested polycrystalline and single-crystal chemical vapor deposition diamond sensors to the highest fluences expected at the super-LHC. We present beam test results of chemical vapor deposition diamond up to fluences of 1.8×1016 protons/cm2 illustrating that both polycrystalline and single-crystal chemical vapor deposition diamonds follow a single damage curve. We also present beam test results of irradiated complete diamond pixel modules.

We investigate models of a heavy neutral gauge boson Z' which could explain anomalies in B meson decays reported by the LHCb experiment. In these models, the Z' boson couples mostly to third generation fermions. We show that bottom quarks arising from gluon splitting can fuse into Z' as an essential production mechanism at the LHC, thereby allowing to probe these models. The study is performed within a generic framework for explaining the B anomalies that can be accommodated in well motivated models. The flavor violating b s coupling associated with Z' in such models produces lower bound on the production cross-section which gives rise to a cross-section range for such scenarios for the LHC to probe. Results are presented in Z' -> $\mu \mu$ decays with at least one bottom-tagged jet in its final state. Some parts of the model parameter space become constrained by the existing dimuon-resonance searches by the ATLAS and CMS collaborations. However, the requirement of one or two additional bottom-tagged jets in the final state would allow for probing a larger region of the parameter space of the models at the ongoing LHC program.

The Collider Detector at Fermilab (CDF) pursues a broad physics program at Fermilab's Tevatron collider. Between Run II commissioning in early 2001 and the end of operations in September 2011, the Tevatron delivered 12 fb-1 of integrated luminosity of p-pbar collisions at sqrt(s)=1.96 TeV. Many physics analyses undertaken by CDF require heavy flavor tagging with large charged particle tracking acceptance. To realize these goals, in 2001 CDF installed eight layers of silicon microstrip detectors around its interaction region. These detectors were designed for 2--5 years of operation, radiation doses up to 2 Mrad (0.02 Gy), and were expected to be replaced in 2004. The sensors were not replaced, and the Tevatron run was extended for several years beyond its design, exposing the sensors and electronics to much higher radiation doses than anticipated. In this paper we describe the operational challenges encountered over the past 10 years of running the CDF silicon detectors, the preventive measures undertaken, and the improvements made along the way to ensure their optimal performance for collecting high quality physics data. In addition, we describe the quantities and methods used to monitor radiation damage in the sensors for optimal performance and summarize the detector performance quantities important to CDF's physics program, including vertex resolution, heavy flavor tagging, and silicon vertex trigger performance.

Diamond devices have now become ubiquitous in the LHC experiments, finding applications in beam background monitoring and luminosity measuring systems. This sensor material is now maturing to the point that the large pads in existing diamond detectors are being replaced by highly granular tracking devices, in both pixel and strip configurations, for detector systems that will be used in Run II at the LHC and beyond. The RD42 collaboration has continued to seek out additional diamond manufacturers and quantify the limits of the radiation tolerance of this material. The ATLAS experiment has recently installed, and is now commissioning a fully-fledged pixel tracking detector system based on diamond sensors. Finally, RD42 has recently demonstrated the viability of 3D biased diamond sensors that can be operated at very low voltages with full charge collection. These proceedings describe all of these advances.

K X-ray production cross sections, photopeak energy shifts and I(Kβ)/I(Kα) intensity ratios are measured for 12C projectiles, in the 14–50 MeV bombarding energy range, on several elements (Al, Si, S, Cl, K, Ca, Ti, Cr, Fe and Cu), using high resolution Si(Li) X-ray spectroscopy. A comparison is made with calculated ECPSSR cross-section values corrected by multiple ionization of K, L and M target subshells and electron capture into the partially empty K-shell of the projectile. The main application for these measurements is multielement trace analysis through particle induced X-ray emission.

Particle physics collider experiments at the high energy frontier are being performed in increasingly harsh radiation environments. While designing adequate detectors is a challenge in itself, their safe operation relies on fast, radiation-hard beam condition monitoring (BCM) systems to protect these fragile devices from beam accidents. This paper will present a BCM system based on polycrystalline chemical vapor deposition (pCVD) diamond sensors used at the Collider Detector at Fermilab (CDF) experiment operating at Fermilab's Tevatron proton-antiproton synchrotron. We report our operational experience with this system, including the recently commissioned abort system. The system is currently the largest of its kind at a hadron collider. It is similar to designs being pursued at the CERN Large Hadron Collider (LHC) experiments.

We present a detailed examination of the heavy flavor properties of jets produced at the Fermilab Tevatron collider. The data set, collected with the Collider Detector at Fermilab, consists of events with two or more jets with transverse energy ET>~15GeV and pseudorapidity |η|<~1.5. The heavy flavor content of the data set is enriched by requiring that at least one of the jets (lepton-jet) contains a lepton with a transverse momentum larger than 8GeV/c. Jets containing hadrons with heavy flavor are selected via the identification of secondary vertices. The parton-level cross sections predicted by the HERWIG Monte Carlo generator program are tuned within theoretical and experimental uncertainties to reproduce the secondary-vertex rates in the data. The tuned simulation provides new information on the origin of the discrepancy between the bb¯ cross section measurements at the Tevatron and the next-to-leading order QCD prediction. We also compare the rate of away-jets (jets recoiling against the lepton-jet) containing a soft lepton (pT>~2GeV/c) in the data to that in the tuned simulation. We find that this rate is larger than what is expected for the conventional production and semileptonic decay of pairs of hadrons with heavy flavor.Received 2 December 2003DOI:https://doi.org/10.1103/PhysRevD.69.072004©2004 American Physical Society

In the present study, results towards the development of a 3D diamond sensor are presented. Conductive channels are produced inside the sensor bulk using a femtosecond laser. This electrode geometry allows full charge collection even for low quality diamond sensors. Results from testbeam show that charge is collected by these electrodes. In order to understand the channel growth parameters, with the goal of producing low resistivity channels, the conductive channels produced with a different laser setup are evaluated by Raman spectroscopy.

We present a Beam Condition Monitor system based on polycrystalline chemical vapor deposition diamond sensors. The system is designed for the Collider Detector at Fermilab (CDF) experiment operating at Fermilab's Tevatron proton-antiproton collider. The system currently represents the largest of its kind to be operated at a hadron collider.

We report the results of a study of multi-muon events produced at the Fermilab Tevatron collider and acquired with the CDF II detector using a dedicated dimuon trigger. The production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe of radius 1.5 cm are successfully modeled by known processes which include heavy flavor production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in which at least one muon candidate is produced outside of the beam pipe, in terms of the same understanding of the CDF II detector, trigger, and event reconstruction.

This article describes a new charged-particle track fitting algorithm designed for use in high-speed electronics applications such as hardware-based triggers in high-energy physics experiments. Following a novel technique designed for fast electronics, the positions of the hits on the detector are transformed before being passed to a linearized track parameter fit. This transformation results in fitted track parameters with a very linear dependence on the hit positions. The approach is demonstrated in a representative detector geometry based on the CMS detector at the Large Hadron Collider. The fit is implemented in FPGA chips and optimized for track fitting throughput and obtains excellent track parameter performance. Such an algorithm is potentially useful in any high-speed track-fitting application.

This dissertation reports the results of a search for charged Higgs bosons in the decays of t$\bar{t}$ pairs produced in p$\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV. The search is performed on a data sample recorded by the upgraded Collider Detector at Fermilab and corresponding to an integrated luminosity of 193 pb-1. The search is based on the relative rates of events in the different t$\bar{t}$ decay channels. Results are obtained in the context of different models. In the context of the minimal supersymmetric extension of the Standard Model (MSSM), for which they fully account for radiative and Yukawa coupling corrections, regions in the (mH±, tan (β)) plane are excluded. In the Tauonic Higgs Model in which the charged Higgs is assumed to decay exclusively to $\bar{τ}$, the BR(t → H+b) is constrained to be less than 0.4 at 95% C.L. If no assumption is made on the charged Higgs decay, the BR(t → H+b) is constrained to be less than 0.90 at 95% C.L. No evidence for charged Higgs production is found.

The absolute calibration of an air fluorescence detector (FD) is an important element in correctly determining the energy of detected cosmic rays. The absolute calibration relates the flux of photons of a given wavelength at the detector aperture to the electronic signal recorded by the FD data acquisition system. For the Auger FDs, the primary absolute calibration method uses a diffusive surface which is placed in front of a telescope aperture to uniformly illuminate the telescope field of view with a known light signal. This single-wavelength measurement (375 nm) will be made at intervals of several months until the stability of the telescopes is determined. The relative wavelength dependence of the calibration is determined through independent measurements. The error in absolute calibration at a single wavelength is estimated to be less than 10%. Two other absolute calibration methods are used to provide an independent verification of the primary measurement. The stability of the calibration with time is monitored nightly by a relative calibration system. In this paper we will provide descriptions of the absolute and relative calibration methods used by the Auger air fluorescence observatory. Results from the calibration of the Auger Engineering Array telescopes will also be presented.

The planned upgrade of the LHC to the High-Luminosity-LHC will push the luminosity limits above the original design values. Since the current detectors will not be able to cope with this environment ATLAS and CMS are doing research to find more radiation tolerant technologies for their innermost tracking layers. Chemical Vapour Deposition (CVD) diamond is an excellent candidate for this purpose. Detectors out of this material are already established in the highest irradiation regimes for the beam condition monitors at LHC. The RD42 collaboration is leading an effort to use CVD diamonds also as sensor material for the future tracking detectors. The signal behaviour of highly irradiated diamonds is presented as well as the recent study of the signal dependence on incident particle flux. There is also a recent development towards 3D detectors and especially 3D detectors with a pixel readout based on diamond sensors.

The Collider Detector at Fermilab (CDF) Run II silicon detector is currently the largest operating silicon detector in High Energy Physics. Its 750,000 channels, spread over 6 m2 of p-on-n silicon sensors, and allow precision tracking of charged particles and vertexing at the 50μm level. The CDF Run II silicon detector is fundamental for all branches of the CDF physics program. It played a critical role in the discovery of Bs mixing and is used extensively for the current Higgs boson searches at the forefront of the energy frontier. Over the last 6 years, the detector efficiency has remained stable above 95% after the Run II commissioning period. While originally designed to withstanding up to 3fb-1 of data, the CDF II silicon detector will have to last to the end of Run II where 5–8fb-1 of data are expected to be delivered. This letter presents the observed effects of infrastructure aging and the solutions implemented to prevent them, followed by the assessment on radiation damage and expected performance to the end of the Tevatron Run II program. The radiation aging of such a large scale system is particular relevant for future silicon detectors in hadronic colliders as LHC.

During the past years the CDF and D0 detectors have collected large amounts of data obtaining a relatively pure sample of pair-produced top quarks and a well understood sample containing singly-produced top quarks. These samples have been used for the precise measurement of the top quark properties, and have set stringent limits on new physics in the top sample. This reports presents the latest results from the CDF and D0 collaborations on the search for new physics within the top sample using an integrated data sample of up to 3.6 fb-1.

The Auger Observatory will be the largest air shower array ever built. This array of water Cherenkov pools offers the unique advantage of a large acceptance at very low zenith angle. Auger is therefore very well suited for study- ing horizontal air showers and in particular neutrino induced showers. In this short lecture the main characteristics of the acceptance will be given as well as the means by which neu- trino induced showers can be disentangled from the large hadronic horizontal shower background. We will also present recent results on the possible detection of tau lepton induced shower from charge current interaction in the ground sur- rounding the Auger array.

3D pixel technology has been used successfully in the past with silicon detectors for tracking applications.Recently, a first prototype of the same 3D technology has been produced on a chemical vapour deposited single-crystal diamond sensor.This device has been subsequently tested in a beam test at CERN's SPS accelerator in a beam of 120 GeV protons.Details on the production and results of testbeam data are presented.

The basic detector unit of the Auger Observatory ground array is a water tank of 12,000 liter capacity, used as a Cerenkov detector. This contribution describes the construc- tion of the polyethylene rotomolded tanks, the procedure for treating the water prior to filling the tanks as well as water quality control.Finally, the installation of the tanks and their components is described.

utility and industrial boilers to cost-effectively control emissions and provide operational and performance benefits.

The measurement of any physical quantity at CMS includes the estimation of a systematic error propagated from the uncertainties on the jet energy calibration. For some physical quantities the main systematic error results from this propagation. This talk will present the main uncertainties sources considered on the jet energy calibration, the effect these have on some particular analyses, and a novel way of handling uncertainties recently deployed at CMS to reduce the dependence on these uncertainties.

The European Physical Journal C—Particles and Fields—publishes scientific manuscripts of relevance to the scientific community following careful and strict peer reviewing and, whenever appropriate and necessary, through discussion with the authors, so as to optimise scientific content and style of presentation prior to publication. In some cases significant disagreement between authors and referees (and/or editors) of the journal cannot be resolved despite all efforts and best of intentions. While the journal—notwithstanding any appeals—retains the right to reject such manuscripts, the editors of this journal may decide, in cases deemed of exceptional interest and potential significance for the field, to accept the manuscript for publication, to amend it by “comments” of the editor(s) in charge and, if appropriate, by a “reply” of the authors of the commented manuscript. The present comment is on “Study of multi-muon events produced in $p\bar{p}$ interactions at $\sqrt{s}=1.96$ TeV” by T. Aaltonen et al. (the CDF Collaboration, Eur. Phys. J. C, 2010, doi: 10.1140/epjc/s10052-010-1336-0 ).

The status of material development of poly-crystalline chemical vapor deposition (CVD) diamond is presented. We also present beam test results on the independence of signal size on incident particle rate in charged particle detectors based on un-irradiated and irradiated poly-crystalline CVD diamond over a range of particle fluxes from 2 kHz/cm$^2$ to 10 MHz/cm$^2$. The pulse height of the sensors was measured with readout electronics with a peaking time of 6 ns. In addition the first beam test results from 3D detectors made with poly-crystalline CVD diamond are presented. Finally the first analysis of LHC data from the ATLAS Diamond Beam Monitor (DBM) which is based on pixelated poly-crystalline CVD diamond sensors bump-bonded to pixel readout electronics is shown.

The top quark was discovered in 1995 1,2 by the CDF and D0/ collaborations. Its large mass suggest it is strongly associated with the mechanism of electro-weak symmetry breaking, and makes it the fermion with the largest coupling to the standard model (SM)-expected, but not yet found, Higgs boson. These reasons make the top quark potentially sensitive to new physics, which can be revealed through precision measurements of its production and decay properties. This letter reports the results of measurements of top quark properties with up to 2 fb of data. In general most of the analyses presented here were performed by both, the CDF and D0/ collaborations, however a single analysis, the most accurate one of either collaboration, would be presented.

During the past years the CDF and D0 detectors have collected large amounts of data obtaining a relatively pure sample of pair-produced top quarks and a well understood sample containing singly-produced top quarks. These samples have been used for the precise measurement of the top quark properties, and have set stringent limits on new physics in the top sample. This reports presents the latest results from the CDF and D0 collaborations on the search for new physics within the top sample using an integrated data sample of up to 3.6 fb{sup -1}.

The precise measurement of the top quark properties is a stringent test of the Standard Model of Particles and Fields. This reports presents the latest results from the CDF and D0 collaborations with an integrated data sample of up to 2.3/fb.

The precise measurement of the top quark properties is a stringent test of the Standard Model of Particles and Fields. This reports presents the latest results from the CDF and D0 collaborations with an integrated data sample of up to 2.3/fb.

Abstract We present a flexible and scalable approach to address the challenges of charged particle track reconstruction in real-time event filters (Level-1 triggers) in collider physics experiments. The method described here is based on a full-mesh architecture for data distribution and relies on the Associative Memory approach to implement a pattern recognition algorithm that quickly identifies and organizes hits associated to trajectories of particles originating from particle collisions. We describe a successful implementation of a demonstration system composed of several innovative hardware and algorithmic elements. The implementation of a full-size system relies on the assumption that an Associative Memory device with the sufficient pattern density becomes available in the future, either through a dedicated ASIC or a modern FPGA. We demonstrate excellent performance in terms of track reconstruction efficiency, purity, momentum resolution, and processing time measured with data from a simulated LHC-like tracking detector.

Particle physics collider experiments at the high energy frontier are being performed today and in the next decade in increasingly harsh radiation environments. While designing detector systems adequate for these conditions represents a challenge in itself, their safe operation relies heavily on fast, radiation-hard beam condition monitoring (BCM) systems to protect these expensive devices from beam accidents. The talk will present such a BCM system based on polycrystalline chemical vapor deposition (pCVD) diamond sensors designed for the Collider Detector at Fermilab (CDF) experiment operating at Fermilab's Tevatron proton-antiproton synchrotron. We report our operational experience with this system, which was commissioned in the spring of last year. The system currently represents the largest of its kind to be operated at a hadron collider. It is similar to designs being pursued by the next generation of hadron collider experiments at the Large Hadron Collider (LHC).

Particle physics collider experiments at the high energy frontier are being performed in increasingly harsh radiation environments. While designing adequate detectors is a challenge in itself, their safe operation relies on fast, radiation-hard beam condition monitoring (BCM) systems to protect these fragile devices from beam accidents. This paper will present a BCM system based on polycrystalline chemical vapor deposition (pCVD) diamond sensors used at the Collider Detector at Fermilab (CDF) experiment operating at Fermilab's Tevatron proton-antiproton synchrotron. We report our operational experience with this system, including the recently commissioned abort system. The system is currently the largest of its kind at a hadron collider. It is similar to designs being pursued at the CERN Large Hadron Collider (LHC) experiments.

Anomalies in B-meson decays reported by the LHC experiment suggest a violation of lepton universality. This could be explained by introducing a heavy neutral gauge boson Z' that selectively couples to third generation quarks and second generation leptons. While the performance of experimental searches for such models is good for large Z' masses, the low-mass region sensitivity is aversely affected by large SM background (mostly Drell-Yan). In this study, we present a novel approach searching for a Z' decaying to muons in association with at least two jets at least one of which is bottom-tagged. We demonstrate that regions of model parameter space can be probed that current inclusive analyses are insensitive to.

Several years ago, the College of Engineering at Texas A&M University moved from a model of admitting all freshmen directly into their first-choice engineering program to a common first-year model.Students now take a common set of mathematics, science and engineering courses in their freshman year before transitioning to a specific engineering major.This change has helped with providing a consistent experience across all engineering majors, enabled the college to support individual student needs to help with their retention, and given freshmen students an opportunity to explore all engineering majors in order to help them make an informed choice.Very soon after this change, the College identified two curricular changes that would help improve the quality of education and student retention.First, a more rigorous process was put in place to ensure that students were placed into the most appropriate first course in mathematics.Second, changes were made to the lecture/laboratory content of the first two theoretical engineering physics courses in order to make the concepts more "real."Specifically, the labs were changed from one hour to two hours with the second hour devoted to an interactive lecture that ties theoretical physics concepts to real-world engineering applications.The actual laboratory portion of the course was also modified to take advantage of a new state-of-the-art, hands-on test and measurement learning system developed by faculty in the Department of Physics.This paper focuses on the redevelopment of the second engineering physics course on electricity and magnetism and describes the new laboratories and lectures in detail.While this effort is an ongoing work in progress, preliminary lessons-learned and future work are discussed.

We present the results of a search for charged Higgs in the decay products of [Formula: see text] at the CDF II detector at the Tevatron. The search is based on the cross section measurements of [Formula: see text] production in three exclusive decay channels: dilepton, lepton + jets and lepton + hadronic tau. Assuming the charged Higgs decays only via [Formula: see text], and [Formula: see text], and [Formula: see text], limits in the MSSM (m Higgs , tan (β)) plane are obtained at tree level. A model-independent analysis is introduced in which the results are independent of Higgs branching ratios. This analysis results in BR ( t → Hb )&lt;0.7 at 95%CL for 80 GeV &lt;m Higgs &lt;150 GeV .

Three months of data taken by the Engineering Array Surface Detector of the Pierre Auger Observatory have been analyzed with the aim of setting a procedure for the study of showers at E_0 ~ 10^18 eV. We present the results, concerning: (i) the selection procedure and the check of its efficiency; (ii) the event rate and its stability; (iii) the characteristics of such events (i.e., angular direction, energy estimator S(1000), rise time vs core distance, correlation with pressure) showing their consistency with the expectations. The performances of the whole Surface Detector of the Auger Observatory are discussed.

The detectors of the surface array of the Pierre Auger Observatory are water Cherenkov tanks. The signals from each tank are read out using three photomultipliers. The energy of the primary particle is inferred from signal densities and requires good linearity of the PMTs and a large dynamic range. The absolute time of arrival of the shower front at each tank is obtained from the Global Positioning System (GPS) with a resolution of about 10 ns, ensuring an accurate primary angular reconstruction. Additionally, it is intended to use the rise time and shape of the signals to constrain the nature of the primary particle: this sets further requirements on the signal processing. In this paper, the main features of the signal processing associated with the surface detector will be presented and its performance will be discussed in the context of the extraction of shower parameters.

The Pierre Auger Observatory is designed to elucidate the origin and nature of Ultra High Energy Cosmic Rays using a hybrid detection technique. A first run of data taking with a prototype version of both detectors (the so called Engineering Array) took place in 2001-2002, allowing the Collaboration to evaluate the performance of the two detector systems and to approach an analysis strategy. In this contribution, after a brief description of the system, we will report some results on the behavior of the Fluorescence Detector (FD) Prototype. Performance studies, such as measurements of noise, sensitivity and duty cycle, will be presented. We will illustrate a preliminary analysis of selected air showers. This analysis is performed using exclusively the information from the FD, and includes reconstruction of the shower geometry and of the longitudinal profile

The Engineering Array of the Auger Observatory has been running successfully since 2001 and inclined showers have been recorded from the start. We have analysed the events with zenith angle > 70 0 recorded between May and November 2002. The different algorithms developed to analyze these showers are also discussed. An preliminary discussion of a reconstructed event having 20 detectors hit is presented. Inclined showers will be detected by the full Auger Observatory and they will allow significant enhancement of the array aperture. High energy events will be seen as spectacular events with 30 or 40 tanks triggered and they will provide alternative information on muon content in air showers.

The surface detector (SD) array of the southern Pierre Auger Observatory will consist of a triangular grid of 1600 water Cherenkov tanks with 1.5 km spacing. For zenith angles less than 60deg the primary energy can be estimated from the signal S(1000) at a distance of about 1000m from the shower axis, solely on basis of SD data. A suitable lateral distribution function (LDF) S(r) is fitted to the signals recorded by the water tanks and used to quantify S(1000). Therefore, knowledge of the LDF is a fundamental requirement for determining the energy of the primary particle. The Engineering Array (EA), a prototype facility consisting of 32 tanks, has taken data continuously since late 2001. On the basis of selected experimental data and Monte Carlo simulations various preliminary LDFs are examined.

The Pierre Auger Southern Observatory in Argentina has begun taking data as it is being developed up to a final enclosed area of 3000 square kilometres. A key aspect of the project is to provide information on the origin of the highest energy cosmic rays through understanding the arrival directions of those particles. To avoid claims of a spurious anisotropy detection because trials have not been properly accounted, the Auger Collaboration has agreed 'a priori' to the analysis prescription presented here. It specifies the following: 1. The accumulation time for the (future) data set to be analyzed. 2. The anisotropy 'targets', each assigned a chance probability level. 3. The analysis procedure for each trial. A positive result will be claimed for any target search only if its chance probability is less than its assigned level. The levels are chosen so that the total chance probability for one or more positive results is 0.001. Exploratory searches beyond this prescription will be encouraged, but the Auger Collaboration will not assign any confidence level to anisotropies that may be discovered that way. Any such discovery would identify a good target for a prescription to be used with a subsequent Auger data set.

The expected sensitivity of the water Cerenkov detector array of the southern Auger Observatory site is de- scribed by calculations of the energy and zenith angle depen- dent aperture function (A(E, ) km 2 sr). The calculations are based, whenever possible, on the forms of the lateral distribu- tion and shower size attenuation that have been empirically determined from previous giant air shower arrays. The un- certainties arising from the extrapolation to distances beyond 2 km and to extreme zenith angles (horizontal air showers) are discussed. Particular attention is paid to the effect of trig- ger schemes on the acceptance turn-on at the array thresh- old and the energy dependent station multiplicity. Finally the aperture calculations are compared with estimates provided by simple MC calculations.

In order to test the design of the Pierre Auger Observatory, as well as different construction alternatives, a small subset of the full array is being built in Malargue, Argentina, and will be put into operation this year. It will consist of 40 surface detectors, covering an area of 46 km, and 2 fluorescence telescopes with an angle of view of 30◦ x 30◦ each. We present a description of this engineering array and report on the advances achieved so far and on future prospects.