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Long-range beam-beam effects in the Tevatron  [PDF]
V. Shiltsev,A. Valishev
Physics , 2014, DOI: 10.5170/CERN-2014-004.101
Abstract: Long-range beam-beam effects occurred in the Tevatron at all stages (injection, ramp, squeeze, and collisions) and affected both proton and antiproton beams. They resulted in beam losses and emittance blow-ups, which occurred in remarkable bunch-to-bunch dependent patterns. On the way to record-high luminosities of the collider, many issues related to the long-range beam-beam interactions have been addressed. Below we present a short overview of the long-range beam-beam effects in the Tevatron. (For a detailed discussion on the beam-beam effects in the Tevatron please see reviews in Refs. [1-3] and references therein).
Long-range beam-beam experiments in the relativistic heavy ion collider  [PDF]
R. Calaga,W. Fischer,N. Milas,G. Robert-Demolaize
Physics , 2014, DOI: 10.5170/CERN-2014-004.141
Abstract: Long-range beam-beam effects are a potential limit to the LHC performance with the nominal design parameters, and certain upgrade scenarios under discussion. To mitigate long-range effects, current carrying wires parallel to the beam were proposed and space is reserved in the LHC for such wires. Two current carrying wires were installed in RHIC to study the effect of strong long-range beam-beam effects in a collider, as well as test the compensation of a single long-range interaction. The experimental data were used to benchmark simulations. We summarize this work.
Summary of the Working Group on 'Single particle effects: parasitic long-range beam-beam interactions'  [PDF]
V. Shiltsev,E. Métral
Physics , 2014, DOI: 10.5170/CERN-2014-004.253
Abstract: There were three presentations given at the session "Single particle effects: parasitic long-range beam-beam interactions" [1, 2, 3] which were followed by discussions. Below we summarize major findings and discussions.
Beam-beam effects in the high-pile-up tests of the LHC  [PDF]
G. Trad
Physics , 2014, DOI: 10.5170/CERN-2014-004.75
Abstract: Investigating the beam-beam limit in the LHC is of great importance, since identifying its source is crucial for the luminosity optimization scenario. Several experiments were carried out to search for this limit and check whether it is dominated by the head-on (HO) or the long-range (LR) interactions. In this paper only the HO collision effects will be considered, tracking the evolution of the maximum tune shift achieved during the dedicated machine developments and the special high pile-up fills.
Simulations of beam-beam and beam-wire interactions in RHIC  [PDF]
Hyung J. Kim,Tanaji Sen,Natalia P. Abreu,Wolfram Fischer
Physics , 2009, DOI: 10.1103/PhysRevSTAB.12.031001
Abstract: The beam-beam interaction is one of the dominant sources of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and strong localized long-range beam-beam effects are experimentally investigated in the RHIC collider. Tune shift, beam transfer function, and beam loss rate are measured in dedicated experiments. In this paper, we report on simulations to study the effect of beam-wire interactions based on diffusive apertures, beam loss rates, and beam transfer function using a parallelized weak-strong beam simulation code (bbsimc). The simulation results are compared with measurements performed in RHIC during 2007 and 2008.
Analysis of long-range studies in the lhc - Comparison with the model  [PDF]
D. Kaltchev,W. Herr
Physics , 2014, DOI: 10.5170/CERN-2014-004.93
Abstract: We find that the observed dependencies (scaling) of long-range beam-beam effects on the beam separation and intensity are consistent with the simple assumption that, all other parameters being the same, the quantity preserved during different set-ups is the first-order smear as a function of amplitude.
Beam-beam-induced orbit effects at LHC  [PDF]
M. Schaumann,R. Alemany Fernandez
Physics , 2014, DOI: 10.5170/CERN-2014-004.231
Abstract: For high bunch intensities the long-range beam-beam interactions are strong enough to provoke effects on the orbit. As a consequence the closed orbit changes. The closed orbit of an unperturbed machine with respect to a machine where the beam-beam force becomes more and more important has been studied and the results are presented in this paper.
Observations of beam-beam effects at the LHC  [PDF]
G. Papotti,X. Buffat,W. Herr,R. Giachino,T. Pieloni
Physics , 2014,
Abstract: This paper introduces a list of observations related to the beam-beam interaction that were collected over the first years of LHC proton physics operation (2010-12). Beam-beam related effects not only have been extensively observed and recorded, but have also shaped the operation of the LHC for high-intensity proton running in a number of ways: the construction of the filling scheme, the choice of luminosity levelling techniques, measures to mitigate instabilities, and the choice of settings for improving performance (e.g. to reduce losses), among others.
Long-range angular correlations at the LHC with ALICE  [PDF]
Leonardo Milano
Physics , 2014, DOI: 10.1016/j.nuclphysa.2014.07.046
Abstract: The observation of long-range correlations on the near and away side -the double ridge- in high-multiplicity p-Pb collisions at sqrt(s_NN) = 5.02 TeV and its similarity to Pb-Pb collisions remains one of the open questions from the p-Pb run at the Large Hadron Collider (LHC). It has been attributed to mechanisms that involve initial-state effects, such as gluon saturation and colour connections forming along the longitudinal direction, and final-state effects, such as parton-induced interactions and collective effects developing in a high-density system possibly formed in these collisions. In order to understand the nature of this double- ridge structure the two-particle correlation analysis has been extended to identified particles. The observed mass dependence in p-Pb resembles the pattern observed in Pb-Pb collisions and is compatible with expectations from hydrodynamics. The subtraction of the long-range structures allows the study of the hadron production belonging to the fragmentation of jets originating from low momentum-transfer scatterings (minijets).
Beam-beam simulation code BBSIM for particle accelerators  [PDF]
Hyung J. Kim,Tanaji Sen
Physics , 2011, DOI: 10.1016/j.nima.2011.03.059
Abstract: A highly efficient, fully parallelized, six-dimensional tracking model for simulating interactions of colliding hadron beams in high energy ring colliders and simulating schemes for mitigating their effects is described. The model uses the weak-strong approximation for calculating the head-on interactions when the test beam has lower intensity than the other beam, a look-up table for the efficient calculation of long-range beam-beam forces, and a self-consistent Poisson solver when both beams have comparable intensities. A performance test of the model in a parallel environment is presented. The code is used to calculate beam emittance and beam loss in the Tevatron at Fermilab and compared with measurements. We also present results from the studies of two schemes proposed to compensate the beam-beam interactions: a) the compensation of long-range interactions in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven and the Large Hadron Collider (LHC) at CERN with a current-carrying wire, b) the use of a low energy electron beam to compensate the head-on interactions in RHIC.
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