113927606
Ground motion: frequency of occurrence versus amplitude of disturbing transient events
Successful collider operation requires that ground motion not exceed certain tolerances. In this note it is pointed out that on occasion these tolerances are exceeded. The frequency of such events and their amplitudes, measured as a function of time of day, have been measured. An examination of the data leads one to conclude that most events are of cultural (i.e., man-made) origin. 2 references, 20 figures.
112503547
Survey of vibration amplitudes throughout the linac
The magnitude of vibrations of the Linac structure due to on site disturbances, such as cooling towers, pumps, generators, Highway 280 overpass traffic, is of interest. CN-263, for example, discusses tolerances of random (i.e., uncorrelated) quad jitter and suggests that amplitudes should not exceed 0.7 microns rms. This note describes the results of a series of measurements carried out in the summer of 1983. In general, the tolerance is not exceeded, but there appears not to be a good safety factor at low frequencies.
107438884
Ground motion - some relative phase measurements in the PEP tunnel
The spatial as well as the temporal characteristics of ground motion are of interest when one attempts to evaluate orbit distortions resulting from time varying quadrupole displacements. In other words, one needs to know the spatial correlations of quad displacements along the orbits path. A correlation with the betatron wavelength would be, for example, potentially more dangerous than from say purely statistically uncorrelated quad motions. The space versus time relationship of ground motion is, of course, related by the effective velocity of sound in the supporting medium. The medium consists of the ground itself, the tunnel floor and the magnet support structure - the latter two having perhaps transmission line characteristics of their own. The question therefore is: What values of velocity should one use for the various types of disturbances that will be encountered in practice. This note describes the results of a minimal experiment designed to answer two questions:(a) Is it at all possible to measure correlations in an existing tunnel with simple equipment. (b) Are the results consistent with the known geophysical characteristic of the site. The answer to both questions, we believe, is surprisingly, yes.
119519024
Initial Condition for QGP Evolution from NEXUS
We recently proposed a new approach to high energy nuclear scattering, which treats the initial stage of heavy ion collisions in a sophisticated way. We are able to calculate macroscopic quantities like energy density and velocity flow at the end of this initial stage, after the two nuclei having penetrated each other. In other words, we provide the initial conditions for a macroscopic treatment of the second stage of the collision. We address in particular the question of how to incorporate the soft component properly. We find almost perfect"Bjorken scaling": the rapidity coincides with the space-time rapidity, whereas the transverse flow is practically zero. The distribution of the energy density in the transverse plane shows typically a very"bumpy"structure.
125196423
Energy dependence of hadron production in EPOS
119270280
Jets, bulk matter, and their interaction in heavy ion collisions at several TeV
We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The aim is a complete description of particle production at all transverse momentum ($p_{t}$) scales. In this picture, the hard initial scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the $p_{t}$ of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes and flows) and jets. We introduce a criterion based on parton energy loss to decide whether a given string segment contributes to the bulk or leaves the matter to end up as a jet of hadrons. Essentially low $p_{t}$ segments from inside the volume will constitute the bulk, high $p_{t}$ segments (or segments very close to the surface) contribute to the jets. The latter ones appear after the usual flux tube breaking via q-qbar production (Schwinger mechanism). Interesting is the transition region: Intermediate $p_{t}$ segments produced inside the matter close to the surface but having enough energy to escape, are supposed to pick up q-qbar pairs from the thermal matter rather than creating them via the Schwinger mechanism. This represents a communication between jets and the flowing bulk matter (fluid-jet interaction). Also very important is the interaction between jet hadrons and the soft hadrons from the fluid freeze-out. We employ the new picture to investigate Pb-Pb collisions at 2.76 TeV. We discuss the centrality and $p_{t}$ dependence of particle production and long range dihadron correlations at small and large $p_{t}$.