Operating the ATLAS data-flow system with the first LHC collisions

LHC and the dark matter search: A review

Collisions of the Large Hadron Collider (LHC) were collected by ATLAS end of 2009 at a centre of mass energy of 900 GeV and are now being collected at √s = 7 TeV. This paper gives an overview of the performance of the ATLAS high level trigger for the selection of electrons, photons, taus, jets and missing transverse energy. Comparisons of the selection variables based on the calorimeter and tracking information calculated by the different trigger levels and the offline reconstruction are shown. This has been an important step in the commissioning of these triggers to ensure their correct functioning and the results from the first data are very encouraging. Furthermore, examples of comparisons between data and Monte Carlo simulations of some of the selection variables are presented. At the end a brief outlook will be given on the steps to be taken to fully commission these triggers with 7 TeV collision data.

ALICE (A Large Ion Collider Experiment) is a heavy-ion detector studying the physics of strongly interacting matter and the quarkgluon plasma at the CERN LHC (Large Hadron Collider). During the second long shut-down of the LHC, the ALICE detector was upgraded to cope with an interaction rate of 50 kHz in Pb-Pb collisions, producing in the online computing system (O2) a sustained input throughput of 3.5 TB/s. In the past years, the O2/FLP project built the new data-acquisition system capable of handling this load. It consists of 200 readout nodes, collecting the data transferred from over 8000 detector links to PCs memory by dedicated PCI boards. The readout software manages the hardware and software memory buffers used for DMA and inter-process communication. It initiates the data flow, performs on-the-fly consistency checks, formats the data, reports performance, and finally pushes the data to the local processing pipeline. The output is then sent by the data distribution software over 100Gb/s links to a dedicated event processing farm. The readout software modular design allowed to address the manifold needs faced during the prototyping, installation and commissioning phases, which proved essential from the lab tests to physics production, like file replay and recording, or online multi-threaded LZ4 compression. We will describe the hardware and software implementation of the O2 readout system, and review the challenges met during the commissioning and first months of operation with LHC collisions in 2022.

While the hunt for new states beyond the standard model (SM) goes on for various well motivated theories, the leptoquarks are among the most appealing scenarios at recent times due to a series of tensions observed in B-meson decays. We consider SU(2) singlet and triplet scalar leptoquarks separately, which contribute to charged and neutral current B-meson decays. Focusing on the single production of these two scalar leptoquarks, we perform a PYTHIA-based simulation considering all the dominant SM backgrounds at the current and future setups of the Large Hadron Collider (LHC). The mono-b-jet + not !!{p_T} finalstate gives the strongest signal for the singlet leptoquark at the 30 TeV LHC or Future Circular Collider (FCC), with a possibility of 5sigma signal significance with gtrsim 1000 fb^{-1} of integrated luminosity, for the chosen benchmark scenarios. The finalstate consisting of a c-jet and two tau -jets provides highest reach for the singlet leptoquark, probing an {mathcal {O}}(10^{-1}) value of the Yukawa-type couplings for up to 3.0 TeV leptoquark mass. For the triplet leptoquark, topology is the most optimistic signature at the LHC, probing leptoquark couplings to fermions at {mathcal {O}}(10^{-1}) value for the leptoquark mass range up to 4.0 TeV. The invariant mass edge distribution is found to be instrumental in determination of the leptoquark mass scale at the LHC. We also perform the analysis at the proposed multi-TeV muon collider, where an {mathcal {O}}(10^{-1}) leptoquark Yukawa coupling can be probed for a 5.0 TeV leptoquark mass.

In this paper we present a detailed analysis of the contribution of the Light-by-Light (LbL), Durham and double diffractive processes for the diphoton production in ultraperipheral PbPb collisions at the Large Hadron Collider (LHC), High-Energy LHC (HE-LHC) and Future Circular Collider (FCC). The acceptance of the central and forward LHC detectors is taken into account and predictions for the invariant mass, rapidity, transverse momentum and acoplanarity distributions are presented. Our results indicate that the contribution of the Durham process is negligible and that the double diffractive process can be strongly suppressed by the exclusivity cuts, which will allow to perform a precise analysis of the LbL scattering, as well the search of beyond Standard Model physics in this final state.

In the Large Hadron Collider collisions between protons and between lead nuclei will occur in which the impact parameter will be greater than the sum of the radii of the colliding partners, ultra-peripheral collisions (UPC's). A novel detector (the ATLAS Zero Degree Calorimeter, ZDC) has been constructed to selectively trigger on such collisions. It detects extremely forward neutrons that are emitted from the projectile/target by photons via a dipole excitation. Cerenkov light, generated by showers in tungsten plates, is funneled to photomultiplier tubes via quartz fibers. The detector has excellent timing and energy resolution.

The pseudorapidity density of charged particles produced at LHC collisions are predicted by using two complementary production mechanisms with a set of consistent integrated and unintegrated parton distributions. We discuss the limiting fragmentation hypothesis and its possible violation, and we compare our model with other partonic models.

We emphasize the importance of including radiative corrections when extracting physics from colliders such as the Tevatron Run II at Fermilab, the Large Hadron Collider (LHC) at CERN, and a future linear collider (LC). We review both well-tested methods and recent advances for calculating these corrections within the Standard Model of electroweak and strong interactions. We discuss the demands on theory and the prospects for matching or exceeding the anticipated experimental precision.

In December 2009 the ATLAS experiment at the CERN Large Hadron Collider (LHC) recorded the first proton-proton collisions at a centre-of-mass energy of 900 GeV, followed by the unprecedented energy of 7 TeV in March 2010. The Semi-Conductor Tracker (SCT) is a key precision tracking device in ATLAS, made of p-in-n-type silicon micro-strip detectors. The completed SCT has been installed inside the ATLAS experimental hall. After the commissioning phase it was in very good shape for the first LHC collision runs: 99.3% of the SCT strips are operational, noise occupancy and hit efficiency exceed the design specifications, and the alignment is already close enough to the ideal one to allow on-line track reconstruction and invariant mass determination. This paper reviews the current status of the SCT, including results from the latest data-taking periods in 2009 and 2010, and from the detector alignment. The operation of the detector and observed problems are discussed, with emphasis on the performance of the SCT with the LHC in collision mode in comparison with the expected parameters and with the Monte Carlo simulations.

Operating optimization for improved energy consumption of a TAC system affected by nighttime thermal loads of building envelopes

Electrical performance of a silicon micro-strip super-module prototype for the High-Luminosity LHC collider

Review of hydrodynamic tunneling issues in high power particle accelerators

The operation of the CERN Large Hadron Collider (LHC) at nominal beam parameters is expected for the next years (2015). Increased synchrotron-radiation stimulated-desorption and electron-cloud build-up are expected. A deep understanding of the interactions between the proton beams and the beampipe wall is mandatory to control the anticipated beam-induced pressure rise. A Vacuum Pilot Sector (VPS) has been designed to monitor the performance of the vacuum system with time. The VPS is installed along a double LHC room temperature vacuum sector (18 m long, 80 mm inner diameter beam pipes) and includes 8 standard modules, 1.4 m long each. Such modules are equipped with residual gas analysers, Bayard-Alpert gauges, photon and electron flux monitors, etc. The chosen modular approach opens the possibility of studying different configurations and implementing future modifications. This contribution will describe the apparatus, the control system designed to drive measurements and possible applications during the next LHC operational phase.

Due to the widespread installation of Distributed Energy Resources (DER) and Demand Side Management resources (DSM) into Distribution Systems (DS), the usage pattern of the DS has changed remarkably in recent times. As a result, the DS has the potential to lead its network operational parameters, such as bus voltage profiles and line flows, outside of their allowable limits. Therefore, they increase the variability and range of variation of loads in the network. However, the DS generally are not designed for such conditions. Thus, it becomes necessary to reassess and redesign the network capacity. A standard strategy would be to increase the capacity of the network, however, this is costly. A cost-effective strategy could be to improve the management of such a system by improving the determination of its actual capacity. Recent advances in ICT equipment make it appear possible to manage the critical loading conditions instead of increasing capacity of the network. Thus, an energy management system is required to perform that function during critical loading. In this thesis, a framework for controlling a network-oriented autonomous energy management system on the distribution network using network capacity constrained is proposed. The framework is based on a State Estimation (SE) technique, which is able to determine the most probable system state of a network. Practically, the system’s operational parameters may be unobservable due to measurement deficiency, loss of communication etc. In such a situation, the observability analysis needs to be performed on the available measurement data to investigate whether the operational parameters are observable or unobservable. Such an analysis is taken into account in this thesis. The proposed framework is akin to an Optimal Power Flow (OPF) problem, where SE gives a starting point to the simulation layer. The simulation layer supports the optimization under the network constraints. In this framework, the challenging task is to formulate the network constraints. To this end, a linearization based map is generated from the functional relationships between an arbitrary set of control variables and an extensive variety of constrainable operational parameters. This map permits the formulation of linear inequality constraints to build a flexible system to manage the network within existing capacity. The feasibility of the proposed constrained generation is demonstrated using an extensive variety of cost functions from a simple Linear Programming (LP) to non-linear functions like absolute value. The significant feature of this approach is that it is flexible both in terms of constrained parameters and control variables. Along with observability, controllability is another crucial factor regarding capacity constrained state optimization. The controllability analysis would allow the decision to be made of whether or not available control variables allow changing the value of operational parameters to specific values without other influences. With this in mind, a technique to analyze the controllability has been developed in this thesis. In addition, some technical applications either already implemented (e.g. phase balances or back-to-back systems) or expected in the near future (e.g. market mechanism) introduce the interdependencies between control variables within the system. The ability to handle the interdependence will be important elements in future distribution system management. Therefore, an approach for modeling of interdependencies introduced by energy transaction and a back-to-back system is developed. In this approach, all control variables are assumed to be independent and are usually chosen to be nodal parameters describing the interaction of equipment connected, but not an element of the network, is the ability to model interdependencies amongst these nodal variables. This approach can originate in a range of different scenarios. One is phase balancing, another is back-to-back systems between networks or feeder, and another one is energy transactions. Furthermore, this framework also facilitated the future smart applications in market structure, namely price bidding scheme and the peer-to-peer energy transfer platform to transact energy between consumers. The proposed framework is applied to two networks namely, an IEEE 13 bus test system and a 29 bus reference distribution network.

The strangeness production ratios [bar wedge]/∧ and [bar wedge]/K0S are measured by the LHCb detector from 0.3 nb-1 of proton-proton collisions delivered by the Large Hadron Collider (LHC) at CERN with centre-of-mass energy √s = 0.9TeV and 1.8 nb-1 at √s = 7TeV. Both ratios are presented as a function of transverse momentum, pT, and rapidity, y, in the ranges 0.15 < pT < 2.50 GeV/c and 2.0 < y < 4.5. The ratios measured at the two energies are in good agreement in an overlapping region of rapidity loss, Δ y = ybeam - y, and are consistent with previous measurements. A review of the Standard Model is presented with emphasis on the diffculties in its application for predictions of physics at the LHC. Phenomenological models are introduced as the current state of the art for such predictions. Accurate models are required as an essential benchmark for future discoveries of physics beyond the Standard Model. LHCb's results represent a powerful test for these models in the soft QCD regime for processes including hadronisation. The ratio [bar wedge]/∧, measuring the transport of baryon number from the collision into the detector, is smaller in data than predicted, particularly at high rapidity. The ratio [bar wedge]/K0 S, measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected. The LHCb experiment is introduced, with particular focus on its Ring Imaging Cherenkov (RICH) detectors. The development and successful implementation of a method to align those RICH detectors is presented, using proton-proton collision data from the early running period of the Large Hadron Collider, which began in November 2009. The performance of the RICH detectors is investigated with preliminary analysis of the Cherenkov photon yield. The RICH mirror positions are monitored using an automated software control system, which has been running successfully since October 2008.