Sébastien Viret

The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7 mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 μm is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n+-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 μm for translations in the plane transverse to the beam. A primary vertex resolution of 13 μm in the transverse plane and 71 μm along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 μm is achieved for particles with transverse momentum greater than 1 GeV/c.

The construction and assembly of the two half barrels of the ATLAS central electromagnetic calorimeter and their insertion into the barrel cryostat are described. The results of the qualification tests of the calorimeter before installation in the LHC ATLAS pit are given.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

A new tracking detector is under development for use by the CMS experiment at the High-Luminosity LHC (HL-LHC). A crucial requirement of this upgrade is to provide the ability to reconstruct all charged particle tracks with transverse momentum above 2–3 GeV within 4 μs so they can be used in the Level-1 trigger decision. A concept for an FPGA-based track finder using a fully time-multiplexed architecture is presented, where track candidates are reconstructed using a projective binning algorithm based on the Hough Transform, followed by a combinatorial Kalman Filter. A hardware demonstrator using MP7 processing boards has been assembled to prove the entire system functionality, from the output of the tracker readout boards to the reconstruction of tracks with fitted helix parameters. It successfully operates on one eighth of the tracker solid angle acceptance at a time, processing events taken at 40 MHz, each with up to an average of 200 superimposed proton-proton interactions, whilst satisfying the latency requirement. The demonstrated track-reconstruction system, the chosen architecture, the achievements to date and future options for such a system will be discussed.

The construction of the ATLAS electromagnetic liquid argon calorimeter modules is completed and all the modules are assembled and inserted in the cryostats. During the production period four barrel and three endcap modules were exposed to test beams in order to assess their performance, ascertain the production quality and reproducibility, and to scrutinize the complete energy reconstruction chain from the readout and calibration electronics to the signal and energy reconstruction. It was also possible to check the full Monte Carlo simulation of the calorimeter. The analysis of the uniformity, resolution and extraction of constant term is presented. Typical non-uniformities of 5‰ and typical global constant terms of 6‰ are measured for the barrel and endcap modules.

The software alignment of planar tracking detectors using samples of charged particle trajectories may lead to global detector distortions that affect vertex and momentum resolution. We present an alignment procedure that constrains such distortions by making use of samples of decay vertices reconstructed from two or more trajectories and putting constraints on their invariant mass. We illustrate the method by using a sample of invariant-mass constrained vertices from D0→K−π+ decays to remove a curvature bias in the LHCb spectrometer.

The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type. This paper describes the main measurement results and conclusions that motivated this decision.

Results are presented of a search for particles decaying into final states with significant missing transverse momentum and exactly two identical flavour leptons (e, μ) of opposite charge in $\sqrt{s}=7$ TeV collisions at the Large Hadron Collider. This channel is particularly sensitive to supersymmetric particle cascade decays producing flavour correlated lepton pairs. Flavour uncorrelated backgrounds are subtracted using a sample of opposite flavour lepton pair events. Observation of an excess beyond Standard Model expectations following this subtraction procedure would offer one of the best routes to measuring the masses of supersymmetric particles. In a data sample corresponding to an integrated luminosity of 35 pb−1 no such excess is observed. Model-independent limits are set on the contribution to these final states from supersymmetry and are used to exclude regions of a phenomenological supersymmetric parameter space.

In the years between 2000 and 2002 several pre-series and series modules of the ATLAS EM barrel and end-cap calorimeter were exposed to electron, photon and pion beams. The performance of the calorimeter with respect to its finely segmented first sampling has been studied. The polar angle resolution has been found to be in the range 50–60 (mrad)/E(GeV). The π0 rejection has been measured to be about 3.5 for 90% photon selection efficiency at pT=50GeV/c. e–π separation studies have indicated that a pion fake rate of (0.07–0.5)% can be achieved while maintaining 90% electron identification efficiency for energies up to 40 GeV.

LHCb is one of the four main experiments of the Large Hadron Collider (LHC) project, which will start at CERN in 2008. The experiment is primarily dedicated to B-Physics and hence requires precise vertex reconstruction. The silicon vertex locator (VELO) has a single hit precision of better than 10μm and is used both off-line and in the trigger. These requirements place strict constraints on its alignment. Additional challenges for the alignment arise from the detector being retracted between each fill of the LHC and from its unique circular disc r/φ strip geometry. This paper describes the track-based software alignment procedure developed for the VELO. The procedure is primarily based on a non-iterative method using a matrix inversion technique. The procedure is demonstrated with simulated events to be fast, robust and to achieve a suitable alignment precision.

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 μm thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to 3 · 1015 neq/cm2. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggest an improved tracker performance over initial expectations.

Abstract The ATLAS detector at the Large Hadron Collider (LHC) at CERN uses a scintillator-iron technique for its hadronic Tile Calorimeter (TileCal). Scintillating light is readout via 9852 photomultiplier tubes (PMTs). Calibration and monitoring of these PMTs are made using a LASER based system. Short light pulses are sent simultaneously into all the TileCal photomultiplier's tubes (PMTs) during ATLAS physics runs, thus providing essential information for ATLAS data quality and monitoring analyses. The experimental setup developed for this purpose is described as well as preliminary results obtained during ATLAS commissioning phase in 2008.

Abstract The Large Hadron Collider at CERN will undergo an upgrade in order to increase its luminosity to 7.5 × 10 34 cm -2 s -1 . The increased luminosity during this High-Luminosity running phase, starting around 2029, means a higher rate of proton-proton interactions, hence a larger ionizing dose and particle fluence for the detectors. The current tracking system of the CMS experiment will be fully replaced in order to cope with the new operating conditions. Prototype planar pixel sensors for the CMS Inner Tracker with square 50 μm × 50 μm and rectangular 100 μm × 25 μm pixels read out by the RD53A chip were characterized in the lab and at the DESY-II testbeam facility in order to identify designs that meet the requirements of CMS during the High-Luminosity running phase. A spatial resolution of approximately 3.4 μm (2 μm) is obtained using the modules with 50 μm × 50 μm (100 μm × 25 μm) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of Φ eq = 5.3 × 10 15 cm -2 , a resolution of 9.4 μm is achieved at a bias voltage of 800 V using a module with 50 μm × 50 μm pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to 2.1 × 10 16 cm -2 . Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper.

LHCb is the dedicated heavy flavour experiment at the Large Hadron Collider at CERN. The partially assembled silicon vertex locator (VELO) of the LHCb experiment has been tested in a beam test. The data from this beam test have been used to determine the performance of the VELO alignment algorithm. The relative alignment of the two silicon sensors in a module and the relative alignment of the modules has been extracted. This alignment is shown to be accurate at a level of approximately 2μm and 0.1mrad for translations and rotations, respectively, in the plane of the sensors. A single hit precision at normal track incidence of about 10μm is obtained for the sensors. The alignment of the system is shown to be stable at better than the 10μm level under air to vacuum pressure changes and mechanical movements of the assembled system.

The response of the ATLAS electromagnetic calorimeter to muons has been studied in this paper. Results on signal over noise ratio, assessment of the detector response uniformity, and position resolution are presented. The possibility to study fine details of the structure of the detector through its response to muons is illustrated on a specific example. Finally, the performance obtained on muons in test-beam is used to estimate the detector uniformity and time alignment precision that will be reachable after the commissioning of the ATLAS detector with cosmic rays.

The time reconstruction performance of the ATLAS electromagnetic calorimeter readout is studied. The contribution of the electronics to the time resolution is estimated to be about 20 ps, thus demonstrating the possibility of achieving a small constant term in the time resolution for particles. The resolution to electromagnetic showers produced by an electron beam is also measured. After correction for the effects due to the calorimeter geometry, a 100 ps constant term is found for a typical cell.

The high instantaneous luminosities expected following the upgrade of the Large Hadron Collider (LHC) to the High-Luminosity LHC (HL-LHC) pose major experimental challenges for the CMS experiment.A central component to allow efficient operation under these conditions is the reconstruction of charged particle trajectories and their inclusion in the hardwarebased trigger system.There are many challenges involved in achieving this: a large input data rate of about 20-40 Tb/s; processing a new batch of input data every 25 ns, each consisting of about 15,000 precise position measurements and rough transverse momentum measurements of particles ("stubs"); performing the pattern recognition on these stubs to find the trajectories; and producing the list of trajectory parameters within 4 µs.This paper describes a proposed solution to this problem, specifically, it presents a novel approach to pattern recognition and charged particle trajectory reconstruction using an all-FPGA solution.The results of an end-to-end demonstrator system, based on Xilinx Virtex-7 FPGAs, that meets timing and performance requirements are presented along with a further improved, optimized version of the algorithm together with its corresponding expected performance.

This paper presents the characterization of the new Associative Memory chip (version 7) designed and fabricated in 28 nm CMOS. The design aims at: enhancing links from/to FPGAs; increasing bandwidth thanks to full custom LVDS transceivers; and reducing power consumption and silicon area by means of new memory cells designed with full-custom approach. The design was submitted in December 2016; the prototypes were fabricated and packaged in a 17 × 17 Ball Grid Array (BGA) standalone package. Prototype characterization confirms the chip functionality. The final chip will be assembled in a System In Package (SiP) together with a bare FPGA die.

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is $99.95\pm0.05\,\%$, while the intrinsic spatial resolutions are $4.80\pm0.25\,\mu \mathrm{m}$ and $7.99\pm0.21\,\mu \mathrm{m}$ along the $100\,\mu \mathrm{m}$ and $150\,\mu \mathrm{m}$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

The high luminosity upgrade of the Large Hadron Collider, foreseen for 2026, necessitates the replacement of the CMS experiment’s silicon tracker. The innermost layer of the new pixel detector will be exposed to severe radiation, corresponding to a 1 MeV neutron equivalent fluence of up to $$\Phi _{eq} = 2 \times 10^{16}$$ cm $$^{-2}$$ , and an ionising dose of $${\approx } 5$$ MGy after an integrated luminosity of 3000 fb $$^{-1}$$ . Thin, planar silicon sensors are good candidates for this application, since the degradation of the signal produced by traversing particles is less severe than for thicker devices. In this paper, the results obtained from the characterisation of 100 and 200 $$\upmu $$ m thick p-bulk pad diodes and strip sensors irradiated up to fluences of $$\Phi _{eq} = 1.3 \times 10^{16}$$ cm $$^{-2}$$ are shown.

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.

We discuss the latest simulation results of rare semileptonic and leptonic decays of B-mesons and Λb-baryon at the ATLAS LHC detector.

A Real-Time demonstrator based on the ATCA Pulsar-IIB custom board and on the Pattern Recognition Mezzanine (PRM) board has been developed as a flexible platform to test and characterize low-latency algorithms for track reconstruction and L1 Trigger generation in future High Energy Physics experiments.The demonstrator has been extensively used to test and characterize the Track-Trigger algorithms and architecture based on the use of the Associative Memory ASICs and of the PRM cards.The flexibility of the demonstrator makes it suitable to explore other solutions fully based on a high-performance FPGA device.

The Concentrator Integrated Circuit (CIC) ASIC is a front-end chip for both Pixel-Strip (PS) and Strip-Strip (2S) modules of the future Phase-II CMS Outer Tracker upgrade at the HighLuminosity LHC (HL-LHC). It collects the digital data coming from eight upstream front-end chips (either MPAs or CBCs, depending on the module type), formats the signal in data packets containing the trigger information from eight bunch crossings and the raw data from events passing the first trigger level, and finally transmits them to the LpGBT unit. The design and its implementation in a 65 nm CMOS technology of the first prototype that integrates all functionalities for system level operation are presented in this contribution.

LHCb is one of the four main experiments of the LHC project, which will start at CERN in 2007. It will be primarily dedicated to B-Physics analysis. This requires precise vertex reconstruction. This is the role of the Vertex Detector (VELO), which has to fulfill very tight requirements, and this in turn places strict constraints on its alignment. This paper describes the main alignment procedure chosen for the VELO, concentrating particularly on the software alignment.

Abstract For the Phase II upgrade at HL-LHC, CMS needs a new Outer Tracker detector able to cope with reduced material budget, increased radiation tolerance and higher pile-up conditions with respect to LHC. The main feature of the Outer Tracker will be its inclusion at the first level of the CMS trigger system with data readout at 40 MHz. Two types of modules, Pixel-Strip and Strip-Strip will equip the Outer Tracker. Each module consists of a superposition of two silicon layers, able to detect charged particles, and an innovative readout electronics, allowing a significant data rate reduction. The Concentrator Integrated Circuit (CIC) is a 65 nm CMOS radiation tolerant front-end ASIC for both modules. It is considered a fundamental element of the future detector front-end chain due to its role in aggregating and compressing data from 8 front-end ASICs on each module. It reduces the data throughput by an order of magnitude. Two first version of the CIC were previously developed and tested. This paper will present the pre-production version, called CIC2.1, together with the functional and wafer test results.

This paper presents a novel hardware architecture based on Associative Memory technology for sequence alignment. The Associative Memory chip (AMchip) architecture employs a huge amount of parallelization to perform real time combinatorial pattern matching. It can be used to perform very fast searches over a large database using hamming weight as a similarity metric. In the presented hardware platform the AMchip communicates with a Xilinx Zynq ARM CPU + FPGA through high-speed (2.4~Gbps) serial links enabling seamless integration between the software and the hardware acceleration. The result shows that low score sections of a database sequence are eliminated rapidly using this architecture which in turn leads to significant speed up. The outcome of a preliminary study on a selected reference protein database shows that all the matches between query and database sequences found by NCBI-BLAST can be successfully found also by the Associative Memory based algorithm.

Abstract The Concentrator Integrated Circuit (CIC) ASIC is a front-end chip for both Pixel-Strip (PS) and Strip-Strip (2S) modules of the future Phase-II CMS Outer Tracker upgrade at the High-Luminosity LHC (HL-LHC). This data aggregator, designed in 65 nm CMOS technology, will be a key element of the tracker front-end chain. A first prototype, CIC1, was tested successfully in early 2019 and was followed by the development of a final radiation tolerant version of the chip: the CIC2. CIC2 design, implementation, and complete test results, are presented.

LHCb is the dedicated b-physics experiment of the LHC. Its vertex detector, the VErtex LOcator (VELO), will operate in a harsh radiation environment with limited access due to its proximity to the LHC beam. To ensure the long term operation and performance, every module was required to pass a set of quality assurance tests. These were specifically developed for the VELO modules to take into account their operational environment and assembly steps. Each VELO module was rigorously inspected, tested and thermally cycled in the Glasgow module burn-in procedures. This paper provides details of the burn-in procedures and summarises the main results that were found. Some of the major results presented in this paper are: the full characterisation of the leakage currents; identification of bad channels; and signal to noise measurements. A few minor problems were identified through visual inspections of the modules and the feedback into the production process proved critical. As a result of the electrical and thermal tests, one module out of the 45 that were tested was rejected due to its thermal performance. Studies are also reported, based on individual modules, characterising the front end read out chip pulse shape.

The Compact Muon Solenoid (CMS) experiment plans to replace its strip tracker system with a completely new Outer Tracker system to cope with the higher luminosity, compared to Run 2 operation, provided by the HL-LHC.This CMS Phase-2 Outer Tracker will be build up from two types of modules both consisting out of two parallel silicon sensors separated by a few millimetres.To read out the two types of modules four Outer Tracker specific custom chips are required.This proceeding introduces the module concept, goes into more detail on the data path, discusses the test system (OT-µDTC) designed for testing prototypes based on these ASICs and gives examples of test results obtained with this test system.

A search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, separately in light-quark and b quark decay modes, identified using jet substructure and advanced b tagging techniques. Results are based on samples of proton-proton collisions collected with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 inverse femtobarns, respectively. The results of the search are combined with those of a similar search in the leptonic decay modes of the Z boson, based on the same data sets. Spin-0 resonances with various widths and with masses in a range between 0.2 and 3.0 TeV are considered. No significant excess is observed either in the individual analyses or the combination. The results are presented in terms of upper limits on the production cross section of such resonances and constitute the most stringent limits to date for a wide range of masses.

The inelastic hadronic cross section in proton-lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of 12.6 +/- 0.4 inverse nanobarns, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton-lead collisions with hadronic activity produced in the pseudorapidity ranges 3<abs(eta)<5 and/or -5<abs(eta)<-3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be sigma[inel,pPb]=2061 +/- 3 (stat) +/- 34 (syst) +/- 72 (lum) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of sigma[inel,pPb] is compatible with that expected from the proton-proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.

We present a system architecture made of a motherboard with a Xilinx Zynq System on Chip (SoC) and a mezzanine board equipped with an Associative Memory chip (AM). The proposed architecture is designed to serve as an accelerator of general purpose algorithms based on pipeline processing and pattern recognition. We present the open source software and firmware developed to fully exploit the available communication channels between the ARM CPU and the FPGA using Direct Memory Access (DMA) technique and the AM using Multi-Gigabit Transceivers (MGT). We report the measured performances and discuss potential applications and future developments. The proposed architecture is compact, portable and provide a large communication bandwidth between components.

The increase of the luminosity in the High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) will require the use of Tracker information in the evaluation of the Level-1 trigger in order to keep the trigger rate acceptable (i.e.: <;1MHz). In order to extract the track information within the latency constraints (<;5μs), a custom real-time system is necessary. We developed a prototype of the main building block of this system, the Pattern Recognition Mezzanine (PRM) that combines custom Associative Memory ASICs with modern FPGA devices. The architecture, functionality and test results of the PRM are described in the present work.

A measurement of the ttbar production cross section at sqrt(s)=13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 inverse femtobarns, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be sigma(ttbar)= 835 +/- 3 (stat) +/- 23 (syst) +/- 23 (lum) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark (m[t]), the value of m[t] is found to be 172.7+2.4-2.7 GeV.

The LHCb Vertex Locator contains 42 silicon sensor modules. Each module has two silicon sensors. A method for determining the relative alignment of the silicon sensors within each module from data is presented. The software implementation details are discussed. Monte-Carlo simulation studies are described that demonstrate an alignment precision of 1.3 micron is obtained in the sensor plane.

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.

The foreseen Phase-2 upgrades at the LHC present very challenging requirements for the front-end readout electronics of the CMS Outer Tracker detector. High data rates in combination with the employment of a novel technique for rejecting locally low transverse momentum particles as well as the strict low power consumption constraints require the implementation of an optimized readout architecture and specific interconnect synchronization schemes for its components. This work focuses on the development and the verification of the Concentrator IC (CIC) ASIC, a 65 nm digital chip featuring high input and output data rates, in the context of the readout chains incorporating all front-end ASICs: namely the Macro Pixel ASIC (MPA), Short Strip ASIC (SSA) for the Pixel-Strip (PS) modules and the CMS Binary Chip (CBC) for Strip-Strip (2S) Modules. The CIC ASIC receives high data rate (320 MHz) digital streams from eight Front-end ASICs via a total of 48 differential lines and transmits them through seven differential lines operating at 320 MHz or 640 MHz, depending on the occupancy of the detector module. A complex system level simulation environment based on the System-Verilog hardware description language and on the Universal Verification Methodology (UVM) platform has been adapted and extended to help the CIC development and verification simulating the complete readout chains from the particle event to the output of the modules. The paper is composed of four sections: the first one describes the pT module concept, the second presents the UVM environment for MPA/SSA ASICs adapted and extended to include the CIC, the third one shows the readout-chain forecasted performances and show some examples of usage of this framework. The last section presents the PS module efficiency as a function of the stub occupancy for different CIC output frequencies.

LBNL-55639 A Step Towards A Computing Grid For The LHC Experiments: ATLAS Data Challenge 1 R. Sturrock University of Melbourne, AUSTRALIA R. Bischof, B. Epp, V. M. Ghete, D. Kuhn Institute for Experimental Physics, University of Innsbruck, AUSTRIA A.G. Mello Universidade Federal do Rio de Janeiro, COPPE/EE/IF, Rio de Janeiro, BRAZIL B. Caron Centre for Subatomic Research, University of Alberta and TRIUMF, Vancouver, CANADA M.C. Vetterli Department of Physics, Simon Fraser University, Burnaby, CANADA G. Karapetian Laboratoire de Physique Nucleaire, Universite’ de Montre’al, CANADA K. Martens Department of Physics, University of Toronto, CANADA A. Agarwal, P. Poffenberger, R.A. McPhersona, R.J. Sobiea Department of Physics and Astronomy, University of Victoria, CANADA S. Armstrong, N. Benekos, V. Boisvert, M. Boonekampb,, S. Brandt, P. Casado, M. Elsing, F. Gianotti, L. Goossens, M. Grote, J.B. Hansen, K. Mair, A. Nairz, C. Padilla, A. Poppleton, G. Poulard, E. Richter-Wasc, S. Rosati, T. Schoerner-Sadeniusd, T. Wengler CERN G.F. Xu Institute of High Energy Physics, Chinese Academy of Sciences, CHINA J.L. Ping Nanjing University, CHINA J. Chudoba, J. Kosina, M. Lokajicek, J. Svec Institute of Physics, Academy of Sciences of the Czech Republic, Praha , CZECH REPUBLIC P. Tas Charles University in Prague S. Armstrong, N. Benekos, V. Boisvert, M. Boonekampb,, S. Brandt, P. Casado, M. Elsing, F. Gianotti, L. Goossens, M. Grote, J.B. Hansen, K. Mair, A. Nairz, C. Padilla, A. Poppleton, G. Poulard, E. Richter-Wasc, S. Rosati, T. Schoerner-Sadeniusd, T. Wengler CERN G.F. Xu Institute of High Energy Physics, Chinese Academy of Sciences, CHINA J.L. Ping Nanjing University, CHINA J. Chudoba, J. Kosina, M. Lokajicek, J. Svec Institute of Physics, Academy of Sciences of the Czech Republic, Praha , CZECH REPUBLIC P. Tas Charles University in Prague, Faculty of Mathematics and Physics, IPNP, Praha, CZECH REPUBLIC J. R. Hansen, E. Lytken, J. L. Nielsen, A. Wa”a”na”nen Niels Bohr Institutet for Astronomi, Fysik og Geofysik, Copenhagen, DENMARK S. Tapprogge Helsinki Institute of Physics, Helsinki, FINLAND D. Calvet Universite’ Blaise Pascal de Clermont-Ferrand, FRANCE S. Albrand, J. Collot, J. Fulachier, F. Ledroit-Guillon, F. Ohlsson-Malek, S. Viret, M. Wielerse LPSC, CNRS-IN2P3, Universite’ Joseph Fourier, Grenoble, FRANCE a Now at the Institute of Particle Physics of Canada b Now at CEA-Saclay c Now at Crakow d Now at Hamburg e At TRIUMF until 01/02/03 K. Bernardet, S. Corre’ard, A. Rozanov, J-B. de Vivie de Regie CPPM, CNRS-IN2P3, Universite’ de la Me’dite’ranne’e, Marseille, FRANCE C. Arnault, C. Bourdarios, J. Hrivnac, M.Lechowski, G. Parrour, A. Perus, D. Rousseau, A. Schaffer, G. Unal LAL-Orsay, CNRS-IN2P3, Universite’ Paris XI, Orsay, FRANCE F. Derue LPNHEP, CNRS-IN2P3, Universite’ Paris 6/7, Jussieu, Paris, FRANCE L. Chevalier, S. Hassani, J-F. Laporte, R. Nicolaidou, D. Pomare‘de, M. Virchaux CEA/DAPNIA, Saclay, FRANCE N. Nesvadba Rheinische Friedrich-Wilhelms Universita”t, Bonn, GERMANY Sergei Baranov Universita”t Freiburg, GERMANY A. Putzer Kirchhoff -Institut fu”r Physik, Universita”t Heidelberg, GERMANY A. Khonich Universita”t Mannheim, GERMANY G. Duckeck , P. Schieferdecker LMU Mu”nchen, GERMANY A. Kiryunin, J. Schieck MPI fu”r Physik, Mu”nchen, GERMANY Th. Lagouri Nuclear Physics Laboratory, Aristotle University of Thessaloniki, GREECE E. Duchovni, L. Levinson, D. Schrager, Weizmann Institute of Science, ISRAEL G. Negrif CNAF, Bologna, ITALY H. Bilokon, L. Spogli LNF, Frascati, ITALY D. Barberis, F. Parodi Universita‘ di Genova e INFN, ITALY G. Cataldi, E. Gorini, M. Primavera, S. Spagnolo Universita‘ di Lecce e INFN, This work was supported in part by the Director, Office of Energy Research, Division of High Energy Physics of the U.S. Department of Energy under Contract DE-AC03-76SF00098

The CMS Outer Tracker at HL-LHC will have to cope with pileup of 300 events per bunch crossing and a trigger rate of up to 1 MHz.The front-end electronics readout chain consists of readout ASICs connected to a data concentrator ASIC featuring zero-suppression.This contribution presents the methodology and the analysis work for the buffer sizing and exception handling featuring a robust data readout synchronization, with an event loss probability lower than 0.1 % at the highest pileup condition and a power density lower than 100 mW/cm 2 .

Cette these est consacree a l'etude des desintegrations radiatives des mesons B dans le detecteur ATLAS du LHC. Les desintegrations radiatives sont une famille des desintegrations rares, transitions impliquant des changements de saveurs par courants neutres (processus b, >s gamma par exemple), interdits a l'ordre le plus bas dans le Modele Standard. Ces processus interviennent par le biais de diagrammes du second ordre (diagrammes pingouin et boite), et sont donc particulierement sensibles aux contributions de nouvelles particules telles que les bosons de Higgs charges ou les particules supersymetriques. Le but de l'etude est de montrer qu'il sera possible de selectionner en ligne les desintegrations radiatives dans ATLAS. Pour ce faire, le traitement des photons de basse energie par le calorimetre electromagnetique d'ATLAS (ECal) est etudie precisement. Le travail presente ici montre que le ECal sera en mesure de traiter ce type de particules. Cette propriete est largement utilisee dans la partie suivante, au cours de laquelle est developpee une strategie de selection des desintegrations radiatives. La methode proposee s'appuie en effet sur la recherche d'une zone de basse energie dans le ECal des le niveau 1 du processus de selection, et sur l'identification precise du photon des le niveau 2. Une grande partie de la strategie presentee concerne egalement le detecteur interne, en particulier au niveau 2 du declenchement. Les resultats obtenus montrent qu'il sera possible de selectionner a court terme une quantite importante de signal, et ce en respectant les contraintes imposees par le trigger d'ATLAS.

This paper gives an overview of the latest performance studies of LHCb, ATLAS, and CMS in rare-B sector. Flavour Changing Neutral Currents involves b→d or b→s transitions occurring only from loop-level in the Standard Model. They consequently provide an excellent probe of effects of New Physics. Within the Standard Model, these decays are sensitive to the CKM matrix elements |Vts| and |Vtd|. Some of these channels, like B→K*γ, have already been measured at B-factories. However, due to a very large bb¯ production, the LHC will play a leading role in rare B-decays studies. Very promising sectors, like B→K*μμ or B→ρμμ, will be extensively studied at LHC. Other rare channels, like B→μμ or Bs→ϕγ, could be observed for the first time at the LHC.

The observation potential of the $B^0_d \rightarrow K^{*0} \gamma$ and $B^0_s \rightarrow \phi \gamma$ decays with the ATLAS detector at the LHC is described in this paper. Radiative $B$ decays involve $b \rightarrow s$ or $b\rightarrow d$ transitions which occur only at loop-level in the Standard-Model (SM) where they are sensitive to the CKM matrix elements $|V_{ts}|$ and $|V_{td}|$. They come with small branching ratios and provide a probe of indirect new physics effects. This paper shows the feasibility of a radiative $B$ decays trigger in ATLAS. This study is based on a simulation of the ATLAS detector response at $\rm 2\times 10^{33}cm^{-2}s^{-1}$ luminosity. We show that for one year about 10000 $B^0_d\rightarrow K^{*0} \gamma$ and 3300 $B^0_s\rightarrow \phi \gamma$ events can be selected by trigger, and that the signal to background ratio can be improved from $10^{-7}$ before LVL1 to about $10^{-2}$ after LVL2 and event filter. Because the online reconstruction tools were not available, the trigger analysis were emulated using the offline software.

Abstract This paper presents an example of the utilisation of ATLAS calorimeters for B-physics analysis. We show that, using ATLAS electromagnetic calorimeter and the appropriate cuts, a 2.3% 71 reconstruction efficiency could be reached in the η → γγ channel with a background fraction of 24%. This makes possible the extension of ATLAS B-physics programme to interesting channels such as B s 0 → J / ψη , and demonstrates that ATLAS calorimeters are performant for soft-particles measurement.

Depuis mon arrivee au CNRS en 2007, mon activite s'inscrit dans le developpement et l'exploitation des resultats des experiences ATLAS et CMS, deux detecteurs de particules actuellement en fonctionnement au CERN a Geneve. Ils sont installes aupres du grand collisionneur de hadrons (LHC), l'accelerateur de particules le plus puissant jamais construit. ATLAS et CMS sont de complexes assemblages permettant de detecter et de mesurer les proprietes (charge electrique, quantite de mouvement, energie) des particules creees lors de la collision des protons circulant dans le LHC. Chacun de ces gigantesques detecteurs contient environ 100 millions de cellules de detection independantes. Le manuscrit est essentiellement consacre a mes activites au sein de la collaboration CMS que j’ai rejoint en 2010. Je reviens egalement brievement, dans la premiere partie, sur mes travaux au sein des collaborations ATLAS (2007-2010) et LHCb (2005-2007). Depuis 2011 mon travail est essentiellement axe autour de la remise a niveau de cette experience en vue de la montee en puissance du LHC en 2026. Une adaptation du collisionneur et des detecteurs est en effet necessaire pour pouvoir collecter encore 10 fois plus de donnees de collisions: c'est le projet HL-LHC. Les deux parties suivantes sont consacrees a la mise a niveau du futur trajectographe de CMS.

The observation potential of the decays B0s,d → J/ψη with the ATLAS detector at the LHC is described in this paper. At present there exist only upper limits for the branching fractions, but at LHC, a clear signal for the decay mode B0s,d → J/ψη is expected. The branching fraction of this decay mode can thus be measured, and other parameters such as B0s lifetime can be measured as well. The decay mode B0s → J/ψη is analogous to the mode B0s → J/ψφ, which has been studied extensively in view of CP violation measurements. In these two decay modes, the CP asymmetry predicted by the Standard Model is very small, and the observation of a sizeable effect would be a signal of physics beyond the Standard Model. The decay mode J/ψη constitutes thus a cross-check for the mode J/ψφ. Furthermore, the former final state is a CP-eigenstate and no angular analysis is thus needed. The reconstruction of η-mesons at LHC experiments has not been addressed before, and therefore the study presented here can also be regarded as an example of the physics prospects with η-mesons at the LHC.