A. Zabi

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at $ \sqrt {s} = 7\;{\text{TeV}} $ is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.

Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.

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.

This Technical Design Report describes the ongoing developments and plans towards the upgrade of the CMS Level-1 trigger for the High-Luminosity Large Hadron Collider.

The Compact Muon Solenoid (CMS) experiment has implemented a sophisticated two-level online selection system that achieves a rejection factor of nearly 105. During Run II, the LHC will increase its centre-of-mass energy up to 13 TeV and progressively reach an instantaneous luminosity of 2 × 1034 cm−2 s−1. In order to guarantee a successful and ambitious physics programme under this intense environment, the CMS Trigger and Data acquisition (DAQ) system has been upgraded. A novel concept for the L1 calorimeter trigger is introduced: the Time Multiplexed Trigger (TMT) . In this design, nine main processors receive each all of the calorimeter data from an entire event provided by 18 preprocessors. This design is not different from that of the CMS DAQ and HLT systems. The advantage of the TMT architecture is that a global view and full granularity of the calorimeters can be exploited by sophisticated algorithms. The goal is to maintain the current thresholds for calorimeter objects and improve the performance for their selection. The performance of these algorithms will be demonstrated, both in terms of efficiency and rate reduction. The callenging aspects of the pile-up mitigation and firmware design will be presented.

Results from the completed Phase 1 Upgrade of the Compact Muon Solenoid (CMS) Level-1 Calorimeter Trigger are presented. The upgrade was performed in two stages, with the first running in 2015 for proton and heavy ion collisions and the final stage for 2016 data taking. The Level-1 trigger has been fully commissioned and has been used by CMS to collect over 43 fb−1 of data since the start of the Run II of the Large Hadron Collider (LHC). The new trigger has been designed to improve the performance at high luminosity and large number of simultaneous inelastic collisions per crossing (pile-up). For this purpose it uses a novel design, the Time Multiplexed Trigger (TMT), which enables the data from an event to be processed by a single trigger processor at full granularity over several bunch crossings. The TMT design is a modular design based on the μTCA standard. The trigger processors are instrumented with Xilinx Virtex-7 690 FPGAs and 10 Gbps optical links. The TMT architecture is flexible and the number of trigger processors can be expanded according to the physics needs of CMS. Sophisticated and innovative algorithms are now the core of the first decision layer of the experiment. The system has been able to adapt to the outstanding performance of the LHC, which ran with an instantaneous luminosity well above design. The performance of the system for single physics objects are presented along with the optimizations foreseen to maintain the thresholds for the harsher conditions expected during the LHC Run II and Run III periods.

The observation of the associated production of the Higgs boson with two top quarks in proton-proton collisions is one of the highlights of the LHC Run 2. Driven by the theoretical description of the physics processes, the Matrix Element Method (MEM) consists in computing a probability that an event is compatible with the signal hypothesis (ttH) or with one of the background hypotheses. It is a powerful classifying tool requiring high dimensional integral computations. The deployment of our MEM production code on GPU’s platform will be described. What follows will focus on the adaptation of the main components of the computations in OpenCL kernels, namely the Magraph matrix element code generator, VEGAS, and LHAPDF. Finally, the gain obtained on GPU’s platforms compared with classical CPU’s platforms will be assessed.

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 Compact Muon Solenoid (CMS) employs a sophisticated two-level online triggering system that has a rejection factor of up to 105. Since the beginning of Run II of LHC, the conditions that CMS operates in have become increasingly challenging. The centre-of-mass energy is now 13 TeV and the instantaneous luminosity currently peaks at 1.5 ×1034 cm−2s−1. In order to keep low physics thresholds and to trigger efficiently in such conditions, the CMS trigger system has been upgraded. A new trigger architecture, the Time Multiplexed Trigger (TMT) has been introduced which allows the full granularity of the calorimeters to be exploited at the first level of the online trigger. The new trigger has also benefited immensely from technological improvements in hardware. Sophisticated algorithms, developed to fully exploit the advantages provided by the new hardware architecture, have been implemented. The new trigger system started taking physics data in 2016 following a commissioning period in 2015, and since then has performed extremely well. The hardware and firmware developments, electron and photon algorithms together with their performance in challenging 2016 conditions is presented.

The CMS collaboration is building the high-granularity calorimeter (HGCAL) for the endcap regions as part of its planned upgrade for the High-Luminosity LHC (HL-LHC). The calorimeter data will form part of the Level-1 trigger (L1T) of the CMS experiment, reducing the event rate from the nominal 40 MHz down to 750 kHz with a latency of 12.5 microseconds. Among the 6 million readout channel of this 5D imaging calorimeter, 1 million "trigger channels" are read at 40 MHz, presenting a significant challenge in terms of data processing for the back-end trigger primitive system. The amount of data produced scales up to 50 Tb/s, an order of magnitude above what is currently handled at CMS. The HGCAL trigger primitive generation (TPG) system is organized in 2 stages: the first stage receiving the front-end data and organizing them into a Time-Multiplexed fashion before transmitting them to the second processing stage, where the data associated with a 120-degree sector of the HGCAL are used to reconstruct particle associated showers in a full depth 3D view. The system is instrumented with 63 ATCA electronic boards equipped with Xilinx Ultrascale FPGAs and SoC controllers, as well as high-speed optical links (16 Gb/s). We present here the technological challenge of implementing such a system and designing the firmware used in reconstructing 3D clusters. Together with tracking information, which will also be available at L1T, particle-flow reconstruction techniques and other sophisticated machine learning approach can be contemplated. We present here the HGCAL TPG system architecture design and the ongoing developments, prototyping and testing. Outlook towards modern technological approach to large data volume processing will be discussed.

The CMS Electromagnetic Calorimeter (ECAL) provides energy sums to the Level-1 Calorimeter Trigger at a rate of 40 MHz.The processing of these trigger primitives (TPs) is performed by dedicated trigger concentrator cards (TCCs) located in the CMS service cavern.Updates to the functionality of the TCCs were required to respond to the challenging experimental conditions of LHC Run 2, where the center-of-mass of proton-proton collision energy was 13 TeV and the peak instantaneous luminosity of the proton beams reached 2x10 34 cm -2 s -1 .A new algorithm, termed the Cumulative Overflow Killing Engine (COKE), has been developed and implemented via software and firmware updates to the TCCs in order to automatically detect and mask noisy or problematic TPs via configurable thresholds.The autorecovery of the TCCs has also been improved, to manage the Single Event Upsets (SEUs) from the front-end electronics.This allows the detector to trigger efficiently without direct expert intervention, and the thresholds can evolve with evolving LHC conditions.

The CMS Level-1 calorimeter trigger is being upgraded in two stages to maintain performance as the LHC increases pile-up and instantaneous luminosity in its second run. In the first stage, improved algorithms including event-by-event pile-up corrections are used. New algorithms for heavy ion running have also been developed. In the second stage, higher granularity inputs and a time-multiplexed approach allow for improved position and energy resolution. Data processing in both stages of the upgrade is performed with new, Xilinx Virtex-7 based AMC cards.

Après deux ans d’arrêt technique, le grand collisionneur de hadrons du CERN a repris ses opérations en 2015, à une énergie et une intensité bien plus élevées. Les détecteurs géants ATLAS et CMS ont été adaptés à ce nouvel environnement, par l’amélioration de leurs systèmes de détection et de leur capacité à sélectionner en temps réel les collisions les plus intéressantes.L’analyse des données collectées jusqu’à l’été 2016 a déjà fourni des résultats très attendus, sur la compréhension du boson de Higgs et sur la recherche d’une nouvelle physique au-delà du Modèle Standard.

Throughout the year 2011, the Large Hadron Collider (LHC) has operated with an instantaneous luminosity that has risen continually to around 4 × 1033cm−2s−1. With this prodigious high-energy proton collisions rate, efficient triggering on electrons and photons has become a major challenge for the LHC experiments. The Compact Muon Solenoid (CMS) experiment implements a sophisticated two-level online selection system that achieves a rejection factor of nearly 106. The first level (L1) is based on coarse information coming from the calorimeters and the muon detectors while the High-Level Trigger (HLT) combines fine-grain information from all sub-detectors. In this intense hadronic environment, the L1 electron/photon trigger provides a powerful tool to select interesting events. It is based upon information from the Electromagnetic Calorimeter (ECAL), a high-resolution detector comprising 75848 lead tungstate (PbWO4) crystals in a “barrel” and two “endcaps”. The performance as well as the optimization of the electron/photon trigger are presented.

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 CMS experiment has implemented a sophisticated two-level online selection system that achieves a rejection factor of nearly 10 5 .The first level (L1) is based on coarse information coming from the calorimeters and the muon detectors while the High-Level Trigger combines fine-grain information from all sub-detectors.During Run II, the LHC will increase its centre-ofmass energy up to 13 TeV and progressively reach an instantaneous luminosity of 2×34 cm -2 s -1 .In order to guarantee a successful and ambitious physics programme under this intense environment, the CMS Trigger and Data acquisition system must be consolidated.In particular the L1 calorimeter trigger hardware and architecture will be modified.The goal is to maintain the current thresholds (e.g., for electrons and photons) and improve the performance for the selection of tau leptons.This can only be achieved by designing an updated trigger architecture based on the recent microTCA technology.Racks can be equipped with fast optical links and latest generation FPGAs can be used.Sophisticated object reconstruction algorithms as well as online pile-up corrections can thus be envisaged.The plan to consolidate the CMS trigger system will be presented as well as the recent hardware and firmware developments.Algorithms to select efficiently electrons and photons, will also be presented along with the expected performance.

La comprehension du monde microscopique se poursuit et nous mene peu a peu vers une description precise des forces fondamentales qui regissent les particules elementaires. La decouverte du premier champ scalaire, le champ de Brout-Englert-Higgs en 2012 au CERN, permet d’expliquer comment la matiere s’est organisee des les premiers instants de l’Univers. La caracterisation du champ de Brout-Englert-Higgs est cruciale puisqu’elle conditionne l’existence d’une physique au-dela du Modele Standard. Le LHC et ses experiences poursuivent ces recherches dans le but de caracteriser precisement ces forces fondamentales. Le systeme de declenchement d’une experience de physique des particules est un outil de toute premiere importance puisqu’il permet d’acceder aux donnees pertinentes produites par les detecteurs pour mener a bien ce type de recherche. Bien que hautement technique, les conditions de fonctionnement d’un tel systeme sont etroitement liees au programme de physique qu’une experience souhaite etre en mesure d’accomplir. Ces performances dependent aussi de l’environnement dans lequel ce systeme devra fonctionner comme par exemple un collisionneur de particules de haute intensite tel que le LHC. Les systemes d’acquisition ont ete en mesure d’evoluer avec les technologies disponibles afin d’etre exploitables aupres de detecteurs de particules toujours plus complexes. Cette complexite correspond a une resolution grandissante dans le but de distinguer chaque particule dans une collision. Cette granularite fine d’un detecteur se traduit par un nombre de canaux de lecture gigantesque et donc un volume de donnees considerable a traiter. Il est question dans ce manuscrit d’aborder l’ensemble des aspects de cette problematique depuis la mise en œuvre du systeme a la mesure de ses performances et limitations qui ont conduit a la conception d’un systeme ameliore pour le detecteur CMS. Ce systeme aura permis de collecter les donnees necessaires a la decouverte du boson de Higgs ainsi qu’a l’observation de ses modes de production et de desintegration rares. Aujourd’hui, un tel systeme electronique doit permettre egalement aux physiciens d’explorer des territoires inconnus.

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.

Throughout the year 2011, the Large Hadron Collider (LHC) has operated with an instantaneous luminosity that has risen continually to around 4 × 1033cm−2s−1. With this prodigious high-energy proton collisions rate, efficient triggering on electrons and photons has become a major challenge for the LHC experiments. The Compact Muon Solenoid (CMS) experiment implements a sophisticated two-level online selection system that achieves a rejection factor of nearly 106. The first level (L1) is based on coarse information coming from the calorimeters and the muon detectors while the High-Level Trigger (HLT) combines fine-grain information from all sub-detectors. In this intense hadronic environment, the L1 electron/photon trigger provides a powerful tool to select interesting events. It is based upon information from the Electromagnetic Calorimeter (ECAL), a high-resolution detector comprising 75848 lead tungstate (PbWO4) crystals in a "barrel" and two "endcaps". The performance as well as the optimization of the electron/photon trigger are presented.

The CMS electromagnetic calorimeter (ECAL) has been designed to precisely measure electron and photon energy. It is made of 75848 lead tungstate (PbWO4) crystals and its characteristics have been optimized for the search of the Higgs boson in its two photons decay mode. In view of the high interaction rate at the Large Hadron Collider (LHC), CMS implements a sophisticated online selection system that achieves a rejection factor of nearly 10 6 . In the intense hadronic environment, the ECAL trigger system provides a powerful tool to select interesting physics events which may contain electrons or photons in their final states. Comic ray data recorded by the CMS experiment have been analyzed in order to estimate the ECAL trigger performance in terms of efficiency.

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.

For the High-Luminosity Large Hadron Collider era, the trigger and data acquisition system of the Compact Muon Solenoid experiment will be entirely replaced. Novel design choices have been explored, including ATCA prototyping platforms with SoC controllers and newly available interconnect technologies with serial optical links with data rates up to 28 Gb/s. Trigger data analysis will be performed through sophisticated algorithms, including widespread use of Machine Learning, in large FPGAs, such as the Xilinx Ultrascale family. The system will process over 60 Tb/s of detector data with an event rate of 750 kHz. The system design and prototyping are described and examples of trigger algorithms reviewed.

Many physics topics to be studied by the D0 experiment during Run II of the Fermilab Tevatron ppbar collider give rise to final states containing b--flavored particles. Examples include Higgs searches, top quark production and decay studies, and full reconstruction of B decays. The sensitivity to such modes has been significantly enhanced by the installation of a silicon based vertex detector as part of the DO detector upgrade for Run II. Interesting events must be identified initially in 100-200 microseconds to be available for later study. This paper describes custom electronics used in the DO trigger system to provide the real--time identification of events having tracks consistent with the decay of b--flavored particles.

Latest results of CMS searches for a Higgs boson produced in association with top quarks in final states with tau leptons are reported.This contribution will specifically focus on technical aspects related to the Matrix Element Method implementation and on its impact on the sensitivity of the analysis.The analysis presented here uses proton-proton collision data collected at center-ofmass energies of 13 TeV during the Run II of the LHC collected by the CMS experiment in 2016.An excess has been observed with respect to the background-only hypothesis in the multilepton final states: 3.2σ observed significance (2.8σ expected).

The CMS experiment implements a sophisticated two-level triggering system composed of the Level-1, instrumented by custom-design hardware boards, and the software High Level Trigger. In 2017, the LHC delivered proton-proton collisions at a centre-of-mass energy of 13 TeV with a peak instantaneous luminosity larger than 2×1034 cm−2s−1, more than twice the peak luminosity reached during Run I and far larger than the design value. The CMS Level-1 calorimeter trigger was upgraded during the long shutdown 1 between 2013 and 2015, to improve its performance at high luminosity and large number of simultaneous inelastic collisions per crossing (pile-up). All the electronic boards have been replaced, tested and commissioned with data. Smarter, more sophisticated, and innovative algorithms are now the core of the first decision layer of CMS: the upgraded trigger system implements dynamic clustering techniques, pile-up subtraction and isolation requirements for electrons and tau leptons. In addition, the new global trigger is capable of computing complex variables such as those involving the invariant mass of trigger objects. The trigger selections used for a wide variety of physics signals during Run II are presented, ranging from simple single-object selections to more sophisticated algorithms combining different objects and applying analysis-level reconstruction and selection. The design and operation of the Phase I calorimeter trigger will be reviewed. The technological choices made influenced the path towards the Phase II upgrade system necessary for the LHC run at a center-of mass energy of 14 TeV with luminosity of 5−7×1034 cm−2s−1, corresponding to 140-200 pile-up events. The addition of the tracker information at Level-1 and the enhanced calorimeter granularity will be used to maintain the trigger object thresholds at a similar level as the present system.

Many physics topics to be studied by the D0 experiment during Run II of the Fermilab Tevatron ppbar collider give rise to final states containing b--flavored particles. Examples include Higgs searches, top quark production and decay studies, and full reconstruction of B decays. The sensitivity to such modes has been significantly enhanced by the installation of a silicon based vertex detector as part of the DO detector upgrade for Run II. Interesting events must be identified initially in 100-200 microseconds to be available for later study. This paper describes custom electronics used in the DO trigger system to provide the real--time identification of events having tracks consistent with the decay of b--flavored particles.

The D0 experiment, located at the Fermilab National Accelerator Laboratory in the US, is used to study proton-anti-proton collisions at a center of mass energy of 1.96 TeV. The experiment's data acquisition system is based on a sophisticated trigger system used to select potentially interesting events. The Level 2 Silicon Track Trigger (L2STT) is part of the trigger system that provides precise reconstruction of charged particle tracks allowing the selection of events that contain the decays of long lived particles. For example, such particles appear in the decay of the Higgs boson into a pair of bottom quarks. The design of the L2STT preprocessor has greatly benefited from recent advances in electronics technology. The preprocessor has been recently installed and will be used to further optimize the triggering strategy of the experiment. Leptoquarks would mediate hypothetical new interactions between the quarks and leptons of the Standard Model. The existence of such particles would be evidence for physics beyond that model. In this thesis, a direct search for leptoquarks is performed in the jets and missing transverse energy final state. For this analysis, a trigger had to be developed along with a tool to precisely determine its efficiency. An analysis of events exhibiting the acoplanar jets topology was performed on a data sample corresponding to an integrated luminosity of 85 pb-1. This analysis has resulted in the determination of an exclusion region on the possible masses of leptoquarks ranging from 85 GeV/c2 to 109 GeV/c2 at the 95% confidence level.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Alexandre Zabi, CMS ECAL group; Test beam results on the performance of the CMS electromagnetic calorimeter. AIP Conf. Proc. 27 October 2006; 867 (1): 350–357. https://doi.org/10.1063/1.2396972 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

L'experience D0 se deroule au laboratoire Fermilab situe aux Etats-Unis. Elle etudie les collisions proton-antiproton a une energie dans le centre de masse de 1,96 TeV fournies par l'accelerateur TeVatron. L'acquisition des donnees par le detecteur D0 utilise un systeme de declenchement sophistique permettant de selectionner les collisions presentant un potentiel de physique interessant. Le processeur electronique L2STT permet de declencher sur la presence de particules a longue duree de vie dans l'etat final. C'est par exemple le cas de la desintegration du Higgs en une paire de quarks b. Sa conception beneficie des avancees recentes dans le domaine des hautes technologies. Ce systeme est dorenavant completement installe et permettra tres prochainement une optimisation supplementaire de la strategie de declenchement de l'experience. Les leptoquarks sont des particules responsables d'une interaction hypothetique entre les quarks et les leptons du Modele Standard. La mise en evidence d'une telle particule serait interpretee comme signalant l'existence d'une nouvelle physique. Il s'agit dans ce manuscrit d'une recherche directe dans la topologie a jets et energie transverse manquante. Dans le but de mener a bien cette recherche, une methode de declenchement devrait tout d'abord etre developpee ainsi qu'un outil precis pour determiner son efficacite. L'analyse des evenements presentant la topologie de jets acoplanaires a ete conduite sur un lot de donnees correspondant a une luminosite integree de $85 pb^-1$. Cette analyse a permis d'exclure un domaine de masse pour les leptoquarks allant de $85 GeV/c^2$ a $109 GeV/c^2$ a 95% de niveau de confiance.

We present a measurement of the cross section for $Z$ production times the branching fraction to $\tau$ leptons, $\sigma \cdot$Br$(Z\to \tau^+ \tau^-)$, in $p \bar p$ collisions at $\sqrt{s}=$1.96 TeV in the channel in which one $\tau$ decays into $\mu \nu_{\mu} \nu_{\tau}$, and the other into $\rm {hadrons} + \nu_{\tau}$ or $e \nu_e \nu_{\tau}$. The data sample corresponds to an integrated luminosity of 226 pb$^{-1}$ collected with the D{\O}detector at the Fermilab Tevatron collider. The final sample contains 2008 candidate events with an estimated background of 55%. From this we obtain $\sigma \cdot$Br$(Z \to \tau^+ \tau^-)=237 \pm 15$(stat)$\pm 18$(sys)$ \pm 15$(lum) pb, in agreement with the standard model prediction.

The High-Luminosity LHC will open an unprecedented window on the weak-scale nature of the Universe, providing data to perform high-precision measurements of the Standard Model, as well as searches for new physics beyond the Standard Model.Such precision measurements and searches require information-rich datasets with a statistical power that matches the high luminosity provided by the upgrade of the LHC.Efficiently collecting these datasets will be a challenging task, given the harsh environment of up to 200 proton-proton interactions per LHC bunch crossing.For this purpose, CMS is designing an efficient two-level trigger system: the Level 1 Trigger (L1T), implemented in advanced hardware, and the High Level Trigger (HLT), a streamlined version of the CMS reconstruction software running on a computer farm.The L1T will include tracking information and high-granularity calorimeter information for the first time.The current conceptual system design is expected to take full advantage of FPGA and link technologies over the coming years, providing a high-performance, low-latency computing platform for large throughput and sophisticated data correlation across diverse sources.The envisaged L1T system will closely replicate the full offline object reconstruction, to perform more sophisticated and optimized selection.The higher luminosity, event complexity and input rate of 750 kHz present an unprecedented challenge to the HLT, which aims to achieve a similar efficiency and rejection factor as today, despite the higher pileup, and a purer preselection.The introduction of a heterogenous platform combining CPUs and GPUs is described.The expected performance of the upgraded trigger system is presented.