Generation of 1.5 Million Beam Loss Threshold Values

CERN's Large Hadron Collider will store an unprecedented amount of energy in its circulating beams. Beamloss monitoring (BLM) is, therefore, critical for machine protection. It must protect against the consequences (equipment damage, quenches of superconducting magnets) of excessive beam loss. About 4000 monitors will be installed at critical loss locations. Each monitor has 384 beam abort thresholds associated; for 12 integrated loss durations ($40\mu$s to 83 s) and 32 energies (450GeV to 7 TeV). Depending on monitor location, the thresholds vary by orders of magnitude. For simplification, the monitors are grouped in 'families'. Monitors of one family protect similar magnets against equivalent loss scenarios. Therefore, they are given the same thresholds. The start-up calibration of the BLM system is required to be within a factor of five in accuracy; and the final accuracy should be a factor of two. Simulations (backed-up by control measurements) determine the relation between the BLM signal, the deposited energy and the critical energy deposition for damage or quench (temperature of the coil). The paper presents the strategy of determining 1.5 million threshold values

Operational Experience with a LHC Collimator Prototype in the CERN SPS

A full-scale prototype of the Large Hadron Collider (LHC) collimator was installed in 2004 in the CERN Super Proton Synchrotron (SPS) and has been extensively used for beam tests, for control tests and also LHC simulation benchmarking during four years of operation. This operational experience has been extremely valuable in view of the final LHC implementation as well as for estimating the LHC operational scenarios, most notably to establish procedures for the beam-based alignment of the collimators with respect to the circulating beam. These studies were made possible by installing in the SPS a first prototype of the LHC beam loss monitoring system. The operational experience gained at the SPS and the lessons learnt for the LHC operation are presented

Testing Beam-Induced Quench Levels of LHC Superconducting Magnets

In the years 2009-2013 the Large Hadron Collider (LHC) has been operated with the top beam energies of 3.5 TeV and 4 TeV per proton (from 2012) instead of the nominal 7 TeV. The currents in the superconducting magnets were reduced accordingly. To date only seventeen beam-induced quenches have occurred; eight of them during specially designed quench tests, the others during injection. There has not been a single beam- induced quench during normal collider operation with stored beam. The conditions, however, are expected to become much more challenging after the long LHC shutdown. The magnets will be operating at near nominal currents, and in the presence of high energy and high intensity beams with a stored energy of up to 362 MJ per beam. In this paper we summarize our efforts to understand the quench levels of LHC superconducting magnets. We describe beam-loss events and dedicated experiments with beam, as well as the simulation methods used to reproduce the observable signals. The simulated energy deposition in the coils is compared to the quench levels predicted by electro-thermal models, thus allowing to validate and improve the models which are used to set beam-dump thresholds on beam-loss monitors for Run 2.Comment: 19 page

Investigations of the LHC Emittance Blow-Up During the 2012 Proton Run

About 30 % of the potential luminosity performance is lost through the different phases of the LHC cycle, mainly due to transverse emittance blow-up. Measuring the emittance growth is a difficult task with high intensity beams and changing energies. Improvements of the LHC transverse profile instrumentation helped to study various effects. A breakdown of the growth through the different phases of the LHC cycle is given as well as a comparison with the data from the LHC experiments for transverse beam size. In 2012 a number of possible sources and remedies have been studied. Among these are intra beam scattering, 50 Hz noise and the effect of the transverse damper gain. The results of the investigations are summarized in this paper. Requirements for transverse profile instrumentation for post LHC long shutdown operation to finally tackle the emittance growth are given as well

Higgs Boson Theory and Phenomenology

Precision electroweak data presently favors a weakly-coupled Higgs sector as the mechanism responsible for electroweak symmetry breaking. Low-energy supersymmetry provides a natural framework for weakly-coupled elementary scalars. In this review, we summarize the theoretical properties of the Standard Model (SM) Higgs boson and the Higgs sector of the minimal supersymmetric extension of the Standard Model (MSSM). We then survey the phenomenology of the SM and MSSM Higgs bosons at the Tevatron, LHC and a future e+e- linear collider. We focus on the Higgs discovery potential of present and future colliders and stress the importance of precision measurements of Higgs boson properties.Comment: 90 pages, 31 figures. Revised version. To be published in Progress in Particle and Nuclear Physics. This paper with higher resolution figures can be found at http://scipp.ucsc.edu/~haber/higgsreview/higgsrev.p

LHC Impedance Model: Experience with High Intensity Operation in the LHC

The CERN Large Hadron Collider (LHC) is now in luminosity production mode and has been pushing its performance in the past months by increasing the proton beam brightness, the collision energy and the machine availability. As a consequence, collective effects have started to become more and more visible and have effectively slowed down the performance increase of the machine. Among these collective effects, the interaction of brighter LHC bunches with the longitudinal and transverse impedance of the machine has been observed to generate beam induced heating, as well as longitudinal and transverse instabilities since 2010. This contribution reviews the current LHC impedance model obtained from theory, simulations and bench measurements as well as a selection of measured effects with the LHC beam

Validation of energy deposition simulations for proton and heavy ion losses in the CERN Large Hadron Collider

Monte Carlo shower simulations are essential for understanding and predicting the consequences of beam losses in high-energy proton and ion colliders. Shower simulations are routinely used at CERN for estimating the beam-induced energy deposition, radiation damage, and radioactivity in the Large Hadron Collider (LHC). Comparing these shower simulations against beam loss measurements is an important prerequisite for assessing the predictive ability of model calculations. This paper validates fluka simulation predictions of beam loss monitor (BLM) signals against BLM measurements from proton fills at 3.5 and 4 TeV and $^{208}$Pb$^{82+}$ ion fills at 1.38A  TeV. The paper addresses typical loss scenarios and loss mechanisms encountered in LHC operation, including proton collisions with dust particles liberated into the beams, halo impact on collimators in the betatron cleaning insertion, proton-proton collisions in the interaction points, and dispersive losses due to bound-free pair production in heavy ion collisions. Model predictions and measured signals generally match within a few tens of percent, although systematic differences were found to be as high as a factor of 3 for some regions and source terms

Update on Beam Induced RF Heating in the LHC

Since June 2011 the rapid increase of the luminosity performance of the LHC has come at the expense of both increased temperature and pressure of specific, near-beam, LHC equipment. In some cases, this beam induced heating has caused delays while equipment cool-down, beam dumps and even degradation of some devices. This contribution gathers the observations of beam induced heating, attributed to longitudinal beam coupling impedance, their current level of understanding and possible actions planned to be implemented during the 1st LHC Long Shutdown (LS1) in 2013-2014

Top Quark Physics

We review the prospects for studies of the top quark at the LHC.We review the prospects for studies of the top quark at the LHC. Members of the working group who have contributed to this document are: A.Ahmadov, G.Azuelos, U.Baur, A.Belyaev, E.L.Berger, W.Bernreuther, E.E.Boos, M.Bosman, A.Brandenburg, R.Brock, M.Buice, N.Cartiglia, F.Cerutti, A.Cheplakov, L.Chikovani, M.Cobal-Grassmann, G.Corcella, F.del Aguila, T.Djobava, J.Dodd, V.Drollinger, A.Dubak, S.Frixione, D.Froidevaux, B.Gonzalez Pineiro, Y.P.Gouz, D.Green, P.Grenier, S.Heinemeyer, W.Hollik, V.Ilyin, C.Kao, A.Kharchilava, R. Kinnunen, V.V.Kukhtin, S.Kunori, L.La Rotonda, A.Lagatta, M.Lefebvre, K.Maeshima, G.Mahlon, S.Mc Grath, G.Medin, R.Mehdiyev, B.Mele, Z.Metreveli, D.O'Neil, L.H.Orr, D.Pallin, S.Parke, J.Parsons, D.Popovic, L.Reina, E.Richter-Was, T.G.Rizzo, D.Salihagic, M.Sapinski, M.H.Seymour, V.Simak, L.Simic, G.Skoro, S.R.Slabospitsky, J.Smolik, L.Sonnenschein, T.Stelzer, N.Stepanov, Z.Sullivan, T.Tait, I.Vichou, R.Vidal, D.Wackeroth, G.Weiglein, S.Willenbrock, W.W