Search

Run 3 of the Large Hadron Collider (LHC) of the data-taking period poses unprecedented challenges to the computing models used in the high-energy physics experiments of the LHC accelerator. Only in the LHCb experiment, the luminosity has increased by a factor of five. Recent results show that deep learning solutions techniques can significantly improve the performance of the cluster reconstruction in calorimeters when high occupancy is expected. In this paper, we will review selected results of the LHC experiments and, in particular, focus on the investigated convolutional (CNN) and graph neural network (GNN) solutions for planar, LHCb-inspired calorimeters with hybrid granularities. We will also show how the most recent developments in the new experiment-independent simulation framework – Gaussino – can be used to produce training datasets for these models. [ABSTRACT FROM AUTHOR]

A design is presented of a laboratory experiment that could test the suitability of relativistic gravity for propulsion of spacecraft to relativistic speeds. An exact time-dependent solution of Einstein’s gravitational field equation confirms that even the weak field of a mass moving at relativistic speeds could serve as a driver to accelerate a much lighter payload from rest to a good fraction of the speed of light. The time-dependent field of ultrarelativistic particles in a collider ring is calculated. An experiment is proposed as the first test of the predictions of general relativity in the ultrarelativistic limit by measuring the repulsive gravitational field of bunches of protons in the Large Hadron Collider (LHC). The estimated ‘antigravity beam’ signal strength at a resonant detector of each proton bunch is 3 nm/s2 for 2 ns during each revolution of the LHC. This experiment can be performed off-line, without interfering with the normal operations of the LHC. [ABSTRACT FROM AUTHOR]

The experimental requirements in near future accelerators (e.g. High Luminosity-LHC) has stimulated intense interest in development of detectors with high precision timing capabilities. With this as a goal, a new detection concept called PICOSEC, which is based to a “two-stage” MicroMegas detector coupled to a Cherenkov radiator equipped with a photocathode has been developed. Results obtained with this new detector yield a time resolution of 24 ps for 150 GeV muons and 76 ps for single photoelectrons. In this paper we will report on the performance of the PICOSEC in test beams, as well as simulation studies and modelling of its timing characteristics. [ABSTRACT FROM AUTHOR]

The first LHC measurement on ultra-peripheral heavy-ion collisions was carried out with the ALICE experiment. In this paper, ALICE results on exclusive J/ψ studies in Pb-Pb collisions at [formula], in the rapidity region -3.6 < y < -2.6, are given. The coherent J/ψ cross section was found to be dσcohJ/ψ/dy = 1.00 ± 0.18 (stat)+0.24-0.26 (syst) mb. These studies favour theoretical models that include strong modifications to the nuclear gluon density, also known as nuclear gluon shadowing. [ABSTRACT FROM AUTHOR]

The Electromagnetic Calorimeter of the CMS experiment at the LHC includes about 76000 lead tungstate (PbWO4) scintillating crystals. The detector properties must be continuously monitored in order to ensure the extreme stability and precision required. This leads to a very large volume of non-event data to be accessed continuously by shifters, experts, automatic monitoring tasks, detector configuration for trigger and data acquisition systems and offline data reconstruction programs. This paper describes the measurements taken by the Detector Control System, the calibrations, the data handling strategy and the workflow as well as the architecture of the configuration and conditions databases and the web interface to access the data. An overview is given on the experience with detector commissioning, which have allowed a system test in realistic run conditions. [ABSTRACT FROM AUTHOR]

This is my contribution to the commemoration of my great friend Giuseppe ('Beppe') Nardulli who left us in June 2008. [ABSTRACT FROM AUTHOR]

This paper addresses the control optimization of a 4.5 K refrigerator used in the cryogenic system of the Large Hadron Collider (LHC) at CERN. First, the compressor station with the cold-box have been modeled and simulated under PROCOS (Process and Control Simulator), a simulation environment developed at CERN. Next, an appropriate parameter identification has been performed on the simulator to obtain a simplified model of the system in order to design an Internal Model Control (IMC) enhancing the regulation of the high pressure. Finally, a floating high pressure control is proposed using a cascade control to reduce operational costs. [ABSTRACT FROM AUTHOR]

The Minimal Supersymmetry Standard Model contains several hundreds of D- and F-flat directions that are lifted by soft susy breaking terms as well as non-renormalizable terms. In a recent paper we find that only two of these directions, LLe and udd can accommodate inflation. The model predicts more than 103 e-foldings with an inflationary scale of Hinf ∼ 1 GeV, provides a tilted spectrum compatible with WMAP3, and a negligible tensor perturbation. The reheating temperature could be as low as Trh ∼ 1 TeV. The model is stable under radiative as well as supergravity corrections, although a significant finetunning has to be imposed on the ratio of two parameters of the model. The RGE equations allow us to relate the model parameters with slepton and gaugino masses explorable in the LHC, while the neutralino in this model could well be within reach of present dark matter searches in the laboratory. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Compact Muon Solenoid (CMS) is a multi-purpose detector for LHC. The electromagnetic calorimeter (ECAL) contains 75848 lead tungstate crystals allowing a very accurate energy measurement of electrons and photons in the GeV – TeV energy range. More than two thirds of the ECAL Barrel has been already assembled. In this paper an updated analysis on the optical and scintillation properties of about 50000 crystals and an overview on the construction status of the calorimeter are presented. Furthermore, the use of crystal production measurements for the calorimeter precalibration is discussed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Beam Loss Monitoring (BLM) system of the Large Hadron Collider protects the machine from beam induced damage by measuring the absorbed dose rates of beam losses, and by triggering beam dump if the rates increase above the allowed threshold limits. Although the detection time scales are optimized for multi-turn losses, information on fast losses can be recovered from the loss data. In this paper, methods in using the BLM system in diffraction studies are discussed. [ABSTRACT FROM AUTHOR]

Dark Matter is a hypothetical particle proposed to explain the missing matter expected from the cosmological observation. The motivation of Dark Matter is overwhelming however as it is mainly deduced from its gravitational interaction, for it does little to pinpoint what Dark Matter really is. In WIMPs Miracle, weakly interactive massive particle being the Dark Matter candidate is correctly producing the current thermal relic density at weak scale, implying the possibility of producing and detecting it in Large Hadron Collider. Assuming WIMPs being the maverick particle within collider, it is expected to be pair produced in association with a Standard Model particle. The presence of the WIMPs pair is inferred from the Missing Transverse Energy (MET) which is the vector sum of the imbalance in the transverse momentum plane recoils a Standard Model Particle. The collider is able to produce light mass Dark Matter which the traditional detection fail to detect due to the small momentum transfer involved in the interaction; on the other hand, the traditional detection is robust in detecting a higher Dark matter masses but the collider is suered from the parton distribution function suppression. Topologically the processes are similar to the scattering processes in the direct detection thus complementary to the traditional Dark Matter detection. The collider searches are strongly motivated as the results are usually translated to the annihilation and scattering rates at more traditional Dark Matter-oriented experiments, thus a concordance approach is adapted. An overview of Dark Matter searches at the Large Hadron Collider will be covered in this paper. [ABSTRACT FROM AUTHOR]

In the framework of the LHC Injector Upgrade program, a new normal conducting linac (Linac4) operating at the frequency of 352MHz has been recently commissioned to the final energy of 160 MeV. Linac4 will be connected to the LHC injector chain in 2020 and it is expected to provide a 40 mA, 400 µs H- beam for charge-exchange injection into the Proton Synchrotron Booster. The Linac4 pre-injector includes a 45 keV, 2MHz RF-driven, cesiated H- source, a magnetic Low Energy Beam Transport and a 3 MeV Radio Frequency Quadrupole. Currently the pre-injector is limited to beam currents of 30 mA. A campaign of beam measurements at 45 keV under controlled variation of the system parameters has been performed during 2017 to improve the understanding of pre-injector dynamics and to devise a method to overcome the present limitation. This paper reports the results of the measurements and preliminary conclusions on the dependence of current and emittance on the relevant parameters. [ABSTRACT FROM AUTHOR]

This paper presents results on the search for dark matter with the ATLAS experiment at the Large Hadron Collider. The studies discussed involve searches for events with a single (mono) jet or photon plus missing transverse energy interpreted with effective field theory as well as searches for light gravitinos and lepton-jets. No evidence for dark matter production has been found and the results have been translated into exclusion limits on physics beyond the Standard Model for several different scenarios. In particular, ATLAS bounds on weakly interacting massive particles are seen to be both complementary and quite competitive to those from direct detection experiments. [ABSTRACT FROM AUTHOR]

This paper presents recent results on the Higgs boson from the ATLAS experiment at the Large Hadron Collider. The Collaboration reports on measurements of the signal strength, couplings, and spin of the Higgs in several decay channels. We find all measurements to be consistent with Standard Model predictions. The Higgs branching fraction to invisible particles is constrained and no evidence of physics beyond the Standard Model is found. [ABSTRACT FROM AUTHOR]

Fermilab is collaborating with Lawrence Berkeley National Laboratory (LBNL) and Brookhaven National Laboratory (BNL) (US-LARP collaboration) to develop a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade. An important component of this work is the development of materials that are sufficiently radiation resistant for use in critical areas of the upgrade. This paper describes recent progress in characterization of materials, including the baseline CTD101K epoxy, cyanate ester blends, and Matrimid 5292, a bismaleimide-based system. Structural properties of "ten stacks" of cable impregnated with these materials are tested at room and cryogenic temperatures and compared to the baseline CT-101K. Experience with potting 1 and 2 meter long coils with Matrimid 5292 are described. Test results of a single 1-m coil impregnated with Matrimid 5292 are reported and compared to similar coils impregnated with the traditional epoxy. [ABSTRACT FROM AUTHOR]

A prototype Superconducting RF (SRF) cryomodule, comprising multiple compact crab cavities is foreseen to realise a local crab crossing scheme for the "Hi-Lumi LHC", a project launched by CERN to increase the luminosity performance of LHC. A cryomodule with two cavities will be initially installed and tested on the SPS drive accelerator at CERN to evaluate performance with high-intensity proton beams. A series of boundary conditions influence the design of the cryomodule prototype, arising from; the complexity of the cavity design, the requirement for multiple RF couplers, the close proximity to the second LHC beam pipe and the tight space constraints in the SPS and LHC tunnels. As a result, the design of the helium vessel and the cryomodule has become extremely challenging. This paper assesses some of the critical cryogenic and engineering design requirements and describes an optimised cryomodule solution for the evaluation tests on SPS. [ABSTRACT FROM AUTHOR]

The about 1700 interconnections (ICs) between the Large Hadron Collider (LHC) superconducting magnets include thermal shielding at 50-75 K, providing continuity to the thermal shielding of the magnet cryostats to reduce the overall radiation heat loads to the 1.9 K helium bath of the magnets. The IC shield, made of aluminum, is conduction-cooled via a welded bridge to the thermal shield of the adjacent magnets which is actively cooled. TIG welding of these bridges made in the LHC tunnel at installation of the magnets induced a considerable risk of fire hazard due to the proximity of the multi-layer insulation of the magnet shields. A fire incident occurred in one of the machine sectors during machine installation, but fortunately with limited consequences thanks to prompt intervention of the operators. LHC is now undergoing a 2 years technical stop during which all magnet's ICs will have to be opened to consolidate the magnet electrical connections. The IC thermal shields will therefore have to be removed and re-installed after the work is completed. In order to eliminate the risk of fire hazard when re-welding, it has been decided to review the design of the IC shields, by replacing the welded bridges with a mechanical clamping which also preserves its thermal function. An additional advantage of this new solution is the ease in dismantling for maintenance, and eliminating weld-grinding operations at removal needing radioprotection measures because of material activation after long-term operation of the LHC. This paper describes the new design of the IC shields and in particular the theoretical and experimental validation of its thermal performance. Furthermore a status report of the on-going upgrade work in the LHC is given. [ABSTRACT FROM AUTHOR]

In the framework of the R&D program for new superconducting magnets for the Large Hadron Collider accelerator upgrades, CERN is building a new vertical test station to test high field superconducting magnets of unprecedented large size. This facility will allow testing of magnets by vertical insertion in a pressurized liquid helium bath, cooled to a controlled temperature between 4.2 K and 1.9 K. The dimensions of the cryostat will allow testing magnets of up to 2.5 m in length with a maximum diameter of 1.5 m and a mass of 15 tons. To allow for a faster insertion and removal of the magnets and reducing the risk of helium leaks, all cryogenics supply lines are foreseen to remain permanently connected to the cryostat. A specifically designed 100 W heat exchanger is integrated in the cryostat helium vessel for a controlled cooling of the magnet from 4.2 K down to 1.9 K in a 3 m3 helium bath. This paper describes the cryostat and its main functions, focusing on features specifically developed for this project. The status of the construction and the plans for assembly and installation at CERN are also presented. [ABSTRACT FROM AUTHOR]

The LHC cryogenic system radiation tolerant electronics and their associated field instruments have been in nominal conditions since before the commissioning of the first LHC beams in September 2008. This system is made of about 15'000 field instruments (thermometers, pressure sensors, liquid helium level gauges, electrical heaters and position switches), 7'500 electronic cards and 853 electronic crates. Since mid-2008 a software tool has been deployed, this allows an operator to report a problem and then lists the corrective actions. The tool is a great help in detecting recurrent problems that may be tackled by a hardware or software consolidation. The corrective actions range from simple resets, exchange of defective equipment, repair of electrical connectors, etc. However a recurrent problem that heals by itself is present on some channels. This type of fault is extremely difficult to diagnose and it appears as a temporary opening of an electrical circuit; its duration can range from a few minutes to several months. This paper presents the main type of problems encountered during the last four years, their evolution over time, the various hardware or software consolidations that have resulted and whether they have had an impact in the availability of the LHC beam. [ABSTRACT FROM AUTHOR]

In this paper we present some selected results of searchv for new physics effects beyond the Standard Model (SM) involving top quarks, as well as several studies of jet shape and substructure by the ATLAS collaboration. The results are based on data samples recorded with the ATLAS detector from proton-proton collisions at a center-of-mass energy of [formula] TeV at the Large Hadron Collider at CERN. [ABSTRACT FROM AUTHOR]

Hydrodynamics has been established as a good tool to describe many data from relativistic heavyion collisions performed at RHIC and LHC. More recently, it has become clear that it is necessary to use event-by-event hydrodynamics (i.e. describe each collision individually using hydrodynamics), an approach first developed in Brazil. In this paper, I review which data require the use of event-by-event hydrodynamics and what more we may learn on the Quark-Gluon Plasma with this. [ABSTRACT FROM AUTHOR]

Linac4 is a 160 MeV linear accelerator which will inject negative hydrogen ions (H-) into CERN's Proton Synchrotron Booster, a required upgrade to improve the beam brightness in the LHC injector chain. A volume production RF ion source, based on the design of the DESY RF source was implemented, but showed considerable electron dump ablation during operation at 45 keV beam energy. To reduce the electron beam power density in the dump, a magnetized Einzel lens is designed that reduces the beam energy to 10 keV before permanentmagnets dump the electrons on a tungsten surface. Presented in this paper are simulations of the design using IBSimu, the tunable range of parameters depending on the extracted H- and electron current, as well as details of the implementation, the choice of pulsed power converters and the electrode alignment system. In addition, simulations of proton extraction from this source will be shown. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider forward (LHCf) experiment has performed measurements of the neutral particles emitted to the very forward region of proton-proton collisions at LHC. This experiment is designed to explore very forward interaction at very high energy, which is relevant to interpretation of the data from cosmic-ray experiments. LHCf detector is well optimized to measure photons in the multi-TeV energy range, and to reconstruct neutral pions with two photons. It can also measure neutrons. The data acquisitions at 0.9 TeV and 7 TeV were completed in 2010. In this paper, single photon energy spectra obtained at 0.9 TeV and transverse energy spectra of neutral pions obtained at 7 TeV will be presented. The results are compared with expectations by hadronic interaction models used for air-shower simulations. We found none of these models agree with the obtained data in the photon energy spectra, while EPOS shows a good agreement in the transverse energy spectra of neural pions. Impacts on cosmic-ray and QCD physics are also discussed. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider (LHC) cryogenic system comprises eight independent refrigeration and distribution systems that supply the eight 3.3 km long accelerator sectors with cryogenic refrigeration power as well as four refrigeration systems for the needs of the detectors ATLAS and CMS. In order to ensure the highest possible reliability of the installations, it is important to apply a reliability centred approach for the maintenance. Even though large scale cryogenic refrigeration exists since the mid 20th century, very little third party reliability data is available today. CERN has started to collect data with its computer aided maintenance management system (CAMMS) in 2009, when the accelerator has gone into normal operation. This paper presents the reliability observations from the operation and the maintenance side, as well as statistical data collected by the means of the CAMMS system. [ABSTRACT FROM AUTHOR]

The Accelerator Project for Upgrade of LHC (APUL) is a U.S. project participating in and contributing to CERN's Large Hadron Collider (LHC) upgrade program. FermiNational Accelerator Laboratory in collaboration with Brookhaven National Laboratorywas developing sub-systems for the upgrade of the LHC final focus magnet systems. Partof the upgrade called for various lengths of superconducting power transmission linesknown as Superconducting (SC) Links which were up to 100 m long. The SC Linkelectrically connects the current leads in the Distribution Feed Boxes to the interactionregion magnets. The SC Link is an extension of the magnet bus housed within a cryostat.The present concept for the bus consists of 22 power cables, 4 × 13 kA, 2 × 7 kA, 8 × 2.5kA and 8 × 0.6 kA bundled into one bus. Different cable and strand possibilities were considered for the bus design including Rutherford cable. The Rutherford cable bus designpotentially would have required splices at each sharp elbow in the SC Link. The advantage of the round bus design is that splices are only required at each end of the bus duringinstallation at CERN. The round bus is very flexible and is suitable for pulling through thecryostat. Development of the round bus prototype and of 2 splice designs is described in this paper. Magnetic analysis and mechanical test results of the 13 kA cable and splices are presented. [ABSTRACT FROM AUTHOR]

Fermilab is collaborating with Lawrence Berkeley National Laboratory (LBNL) and Brookhaven National Laboratory (BNL) within the US-LHC Accelerator Research Project (US-LARP collaboration) to develop a large-aperture Nb3SN superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade. Several two-layer quadrupole models of the 1-meter and 3.4-meter length with 90 mm apertures have been fabricated and tested by the US-LARP collaboration. High-Jc Nb3SN RRP-54/61 strand was used for nearly all models. Large flux jumps typical for this strand, due to the large sub-element diameter, limited magnet quench performance at temperatures below 2.5-3K. This paper summarizes the fabrication and test by Fermilab of LQM01, a long quadrupole coil test structure (quadrupole mirror) with the first 3.4 m quadrupole coil made of more stable RRP-114/127 strand. The coil and structure are fully instrumented with voltage taps, full bridge strain gauges and strip heaters to monitor preload, thermal properties and quench behavior. Measurements during fabrication are reported, including preload during the yoke welding process. Testing is done at 4.5 K, 1.9 K and a range of intermediate temperatures. The test results include magnet strain and quench performance during training, as well as quench studies of current ramp rate and temperature dependence from 1.9 K to 4.5 K. [ABSTRACT FROM AUTHOR]

Taus, being the heaviest of the leptons, constitute an important tool for searches for new physics at the LHC. Higgs boson couples to mass leading to a significant branching ratio of about 10% for low mass Higgs decaying to tau pairs. Taus become even more important in the minimal supersymmetric extension of the Standard model where the neutral Higgs production is enhanced and the presence of two Higgs doublets results in prediction of additional charged Higgs bosons that may preferentially decay to final states with tau leptons. This paper describes a search for Higgs bosons decaying to di-tau pairs and a search for charged Higgs bosons decaying to taus and neutrinos using about 1 fb-1 of data collected with the CMS detector in 2011. [ABSTRACT FROM AUTHOR]

A Large Ion Collider Experiment (ALICE) is one of the four experiments at the Large Hadron Collider (LHC), and it is dedicated to the study of ultra-relativistic heavy-ion collisions, with the goal of investigating the properties of the high-density state of QCD matter produced in such events. The first Pb-Pb collisions at a centre of mass energy of [formula] TeV per nucleon pair were delivered by LHC in November 2010. In Pb-Pb collisions heavy quarks are regarded as sensitive probes of the interaction dynamics between the parton and the medium produced in such collisions as they are produced on a very short time scale in the initial hard scattering processes and they follow all the evolution of the medium. At the energies available at the LHC charm is produced with large cross section and therefore it is possible to measure its production with good statistical precision. The study of open charm hadrons such as D+, D0, D*+, Ds and Λc in heavy ion collision is of particular interest because it can provide significant insight on the properties of the medium. Proton-proton collision data, that are being recorded at an energy of [formula] TeV since March 2010 provide an essential reference for these studies and allow to test perturbative QCD calculations in an unexplored energy domain. In this paper the analysis of D-meson production, carried out through a study of the hadronic decay channels in Pb-Pb collisions, will be presented in detail. The results for the reconstruction of D0, D+, D*+, and Ds hadrons at central rapidity will be shown along with the first results for the measurement of the D0 and D+ nuclear modification factor and prospects for azimuthal anisotropy studies. [ABSTRACT FROM AUTHOR]

ALICE (A Large Ion Collider Experiment) is the dedicated heavy-ion experiment at the LHC. In fall 2010, Pb-Pb collisions were recorded at a center-of-mass energy of 2.76 TeV per nucleon pair, about 14 times higher than the energy achieved in A-A collisions at RHIC. The study of the produced hot and dense matter with an unprecedented energy density allows the characterization of the quark-gluon plasma, the deconfined state of quarks and gluons, predicted by QCD. The study of in-medium partonic energy loss allows insights into the density of the medium and the energy-loss mechanisms. This paper presents results based on inclusive spectra as well as two and more-particle correlations of charged particles. These are well suited to assess in-medium effects, ranging from the suppression of particles (RAA) and away-side jets (IAA) at high pT to longrange phenomena attributed to collective effects like the ridge at low pT. The analysis is discussed and the results are presented in the context of earlier RHIC measurements where appropriate. [ABSTRACT FROM AUTHOR]

Analysis techniques in LHCf are presented, in which all techniques are required to have a high resolution and efficiency in order to overcome the severe situation, small lateral aperture and longitudinally short length of the detector. In this paper, methods for reconstructing an energy of electromagnetic shower are discussed following the data flow of measured data and Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

We give a brief description of the purpose of the LHCf experiment, detectors and their performance, and what has been done in the first year experiment. A short summary of results at [formula] is given although the energy is not an 'intrinsic' LHC energy. Since detailed results at [formula] will appear soon elsewhere, here we limit ourselves to giving also a brief account of what will come in that paper. [ABSTRACT FROM AUTHOR]

The ALICE experiment at the CERN's Large Hadron Collider allows the study of charmonium production in both e+e- and μ+μ- decay channels. In this paper, the first results obtained from reconstructing J/ψ mesons in proton-proton interactions at s = 7 TeV are discussed. The present plans for quarkonia analyses are also mentioned. [ABSTRACT FROM AUTHOR]

The superconducting magnets of the Large Hadron Collider (LHC) distributed over eight sectors of 3.3-km long are cooled at 1.9 K in pressurized superfluid helium. During the commissioning campaign of the sectors in 2008, cold standby periods at nominal operating temperature have allowed to measure the overall static heat inleaks reaching the magnet cold masses at 1.9 K by enthalpy balance in steady-state operation. In addition, during electrical powering of the different magnet circuits, helium II calorimetry based on precision thermometry has been implemented to assess with an accuracy of 100 mW/m the additional heat loads due to resistive heating and to detect possible abnormal heat dissipation during powering. This paper describes the method applied to perform these measurements, compares the results with the expected specified values and discusses the impact of the measured values on cryo-plant tuning and operational margins. [ABSTRACT FROM AUTHOR]

The insertion regions located around the four interaction points of the Large Hadron Collider (LHC) are mainly composed of the low-β triplets, the separation dipoles and their respective electrical feed-boxes (DFBX). The low-β triplets are Nb-Ti superconductor quadrupole magnets, which operate at 215 T/m in superfluid helium at a temperature of 1.9 K. The commissioning and the first operation of these components have been performed. The thermo-mechanical behavior of the low-βtriplets and DFBX were studied. Cooling and control systems were tuned to optimize the cryogenic operation of the insertion regions. Hardware commissioning also permitted to test the system response. This paper summarizes the performance results and the lessons learned. [ABSTRACT FROM AUTHOR]

The US LHC Accelerator Research Program (LARP) is a collaboration between four US laboratories (BNL, FNAL, LBNL, and SLAC) aimed at contributing to the commissioning and operation of the LHC and conducting R&D on its luminosity upgrade. Within LARP, the Magnet Program’s main goal is to demonstrate that Nb3Sn superconducting magnets are a viable option for a future upgrade of the LHC Interaction Regions. Over the past four years, LARP has successfully fabricated and tested several R&D magnets: 1) the subscale quadrupole magnet SQ, to perform technology studies with 300 mm long racetrack coils, 2) the technology quadrupole TQ, to investigate support structure behavior with 1 m long cos 2θ coils, and 3) the long racetrack magnet LR, to test 3.6 m long racetrack coils. The next milestone consists in the fabrication and test of the 3.7 m long quadrupole magnet LQ, with the goal of demonstrating that Nb3Sn technology is mature for use in high energy accelerators. After an overview of design features and test result of the LARP magnets fabricated so far, this paper focuses on the status of the fabrication of LQ: we describe the production of the 3.4 m long cos 2θ coils, and the of the qualification support structure. Finally, the status of the development of the next 1 m long model HQ, conceived to explore stress and field limits of Nb3Sn superconducting, magnets, is presented. [ABSTRACT FROM AUTHOR]

Fermilab is developing Nb3Sn quadrupole magnets for the planned upgrade of interaction regions of the Large Hadron Collider (LHC). Two distinctly different approaches have been employed, one using quadrupole-symmetric and one using dipole-symmetric collar laminations. This paper describes the design features of both collar types, collaring techniques for brittle Nb3Sn coils, and compares the advantages and disadvantages of the two approaches. Results of mechanical analysis for quadrupoles based on dipole-type and quadrupole-type collars are presented. Magnet construction issues and test results are reported. Test results include coil and component strain measurements during construction. Plans for the completion and test of the first dipole-symmetric assembly are described. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider, designed to collide protons and ions at unprecedented center-of-mass energies, will offer new opportunities for the study of the properties of strongly interacting matter at high energy density and temperature. Such complex investigation will be carried out by three experiments, ALICE, explicitly dedicated to this purpose, ATLAS and CMS, through the analysis of several observables. Among them, an important role is expected to be played by heavy-flavor and heavy quarkonium state measurements. The motivations for measuring open and hidden charm and beauty will be provided in this paper, together with a discussion on the expected performances of the experiments, based on the results of Monte Carlo simulations for a selection of physics channels. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider (LHC) will produce heavy ion collisions at the nucleon-nucleon center of mass energy of 5.5 TeV, the highest energy ever available in a controlled environment. This represents an opportunity to study nuclear matter in systems with unprecedented energy densities. Due to the high incident energy, semi-hard and hard processes will be a dominant feature at the LHC. The Compact Muon Solenoid (CMS) heavy-ion program is ideally suited to study the physics of these probes, addressing open questions in the field of Quantum Chromodynamics (QCD). In this paper an overview of the heavy-ion physics capabilities of the CMS detector is presented. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents result of a study on radiation damage and recovery for lead tungstate crystals produced at BTCP and SIC. Correlations were observed between initial light output and initial longitudinal transmittance at 360 nm, between the loss of longitudinal transmittance at 440 nm and the loss of light output, and between radiation damages levels at different dose rates. No correlations, however, were found between crystal’s initial optical properties and radiation hardness. Excellent linearity was observed between the variations of crystal’s light output and its longitudinal transmittance at 440 nm in several cycles of irradiation followed by recovery, indicating these PWO crystals can be monitored in situ at LHC. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Prior to their final preparation before installation in the tunnel, the ∼1800 series superconducting magnets of the LHC machine shall be entirely tested at reception on modular test facilities. The operation 24 hours per day of the cryogenic test facilities is conducted in turn by 3-operator teams, assisted in real time by the use of the Test Bench Priorities Handling System, a process control application enforcing the optimum use of cryogenic utilities and of the “Tasks Tracking System”, a web-based e-traveller application handling 12 parallel 38-task test sequences. This paper describes how such computer-based management systems can be used to optimize operation of concurrent test benches within technical boundary conditions given by the cryogenic capacity, and how they can be used to study the efficiency of the automatic steering of all individual cryogenic sub-systems. Finally, this paper presents the overall performance of the cryomagnet test station for the first complete year of operation at high production rate. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper we consider possible scenarios to upgrade the LHC luminosity beyond 1034 cm-2s-1. By pushing the accelerator parameters to the ultimate performance we can increase to 1.7 1011 the bunch population and eventually reach a peak luminosity of 2.3×1034 cm-2s-1. To go beyond, a considerable improvement of the LHC parameters, such as ß*, beam intensity, bunch length, number of circulating bunches is required. Finally, the upgrade of the injector complex and of the injection energy is another important ingredient to upgrade both peak and integrated luminosity up to an order of magnitude above the nominal value. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The study of Z boson production in association with a single heavy flavor jet (gQ → ZQ(Q = b, c)) can provide interesting insight on the heavy quark content of the proton. In addition, this process represents a background to the search for the Higgs boson, when it is produced together with a b quark and decays in the same final states (bb, τ+τ-, μ+μ-). This paper presents a preliminary investigation of the potential to study the channel Z + b - jet with the Z → μμ at LHC. The expected statistics and purity of the event sample that could be selected in the data are evaluated considering two different methods for the b tagging. The analysis has been performed, first, with a fast simulation of the ATLAS detector, and then, using the full simulation and the complete offline reconstruction algorithms in the official ATLAS software framework. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

In recent years it has been realized that the attempt to solve the problem of the huge difference between the gravity scale (MPl) and the electroweak scale can lead to extra dimensions scenarios with sizeable effects at the TeV scale. In this paper the prospects of the search at the LHC experiments for some of these models are reviewed. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

From the LHC start-up in 2007, a new domain of exploration will open up with the operation of the ATLAS and CMS detectors that are now being constructed and assembled. This paper summarizes the status of the construction work in mid-2004. The ATLAS and CMS Collaborations are highly motivated to remain on track for LHC physics starting 2007. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Large Hadron Collider (LHC) will be equipped with about 5000 superconducting corrector magnets of 10 different types, ranging from dipoles through quadrupoles, sextupoles and octupoles to decapoles and dodecapoles. Four wires are used with 2 copper/superconductor ratios. Magnet lengths range from 0.15 m to 1.4 m. However, the magnets are all epoxy-impregnated and wound with enameled monolithic wires. The paper highlights the features that are common in the training of all these different magnets and uses that to give some clues for the possible origin of the training. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A cryogenic system for the test facility of high gradient superconducting quadrupole magnets for Large Hadron Collider (LHC) at CERN has been constructed at KEK. It consists of a vertical double-bath cryostat in He II at an atmospheric pressure, a vacuum pumping system and a pair of refrigerator/liquefiers to maximize the cooling capacity to test 6.3m long magnets. The system has been successfully operated in the first cold test at the 6.3m prototype magnet since March 2001 with a refrigeration power of 55.5W at 1.9K. The design and test results are described in this paper. [ABSTRACT FROM AUTHOR]

The cryostat of a Large Hadron Collider (LHC) Interaction Region (IR) quadrupole magnet consists of all components of the inner triplet except the magnet assembly itself. It serves to support the magnet accurately and reliably within the vacuum vessel, to house all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. It must function reliably during storage, shipping and handling, normal magnet operation, quenches, and seismic excitations, and must be able to be manufactured at low cost. The major components of the cryostat are the vacuum vessel, thermal shield, multi-layer insulation system, cryogenic piping, and suspension system. The overall design of a cryostat for superconducting accelerator magnets requires consideration of fluid flow, proper selection of materials for their thermal and structural performance at both ambient and operating temperature, and knowledge of the environment to which the magnets will be subjected over the course of their expected operating lifetime. This paper describes the current LHC IR inner triplet quadrupole magnet cryostats being designed and manufactured at Fermilab as part of the US-LHC collaboration, and includes discussions on the structural and thermal considerations involved in the development of each of the major systems. [ABSTRACT FROM AUTHOR]

If supersymmetry is realised in nature, the approved LHC and the planned sub-TeV linear collider should unravel some, maybe many, of the features of the sparticle world. We survey in this paper the task of comprehensively identifying, understanding and measuring all the particles predicted by the model. We start to address whether a multi-TeV linear collider such as CLIC whose energy may well exceed all the new particle production thresholds is suited to completing this challenging task. [ABSTRACT FROM AUTHOR]

Single and double diffraction dissociation at the LHC is studied in a factorizable Regge-pole model, dominated by a Pomeron pole exchange in the t channel. While the contribution from secondary reggeon exchanges at the LHC is negligible, they are indispensable to match the lower-energy, ISR and FNAL data. To this end we append to the leading Pomeron exchange an effective reggeon. The main emphasis in our study is on the nucleon resonances in missing masses, that are accounted for by a dual model of the inelastic pP → Mx vertex, similar to the DIS structure function, known from HERA, with a non-linear nucleon, N* trajectory in the direct, MX channel. Regge factorization and its breakdown due to a renormalization factor, tempering the energy rise is discussed. [ABSTRACT FROM AUTHOR]

We briefly discuss some of the developments since the publication of the MMHT14 parton distributions. In particular we explore the impact of recent LHC data for W-; Z and tt production, and perform a preliminary new analysis including these data. In this re-fit (which we tentatively call 'MMHT16') there are few changes of significance in the central values of the PDFs, but some data reduce the uncertainties, mainly in the strange and valence quark distributions. We find that an extended d-ū parametrization only leads to minor changes, with the difference going to zero as x → 0. We comment on the determination of the photon PDF. [ABSTRACT FROM AUTHOR]