The lay-out of the photon collider at the international linear collider

One of the interaction regions at the linear colliders should be compatible both with e ⁺ e ⁻ and γγ, γe modes of operation. In this paper, the differences in requirements and possible design solutions are discussed.      

Ultimate parameters of the photon collider at the international linear collider

At linear colliders, the e ⁺ e ⁻ luminosity is limited by beam-collision effects, which determine the required emittances of beams in damping rings (DRs). In γγ collisions at the photon collider, these effects are absent, and so smaller emittances are desirable. In the present damping ring designs, nominal DR parameters correspond to those required for e ⁺ e ⁻ collisions. In this note, I would like to stress once again that as soon as we plan the photon collider mode of ILC operation, the damping ring emittances are dictated by the photon collider requirements — namely, they should be as small as possible. This can be achieved by adding more wigglers to the DRs; the incremental cost is easily justified by a considerable potential improvement of the γγ luminosity. No expert analysis exists as of now, but it seems realistic to obtain a factor five increase of the γγ luminosity compared to the ‘nominal’ DR design.      

New final doublets and power densities for the international linear collider small crossing angle layout

In this paper we use current and proposed final doublet magnet technologies to reoptimise the interaction region of the international linear collider and reduce the power losses. The result is a set of three new final doublet layouts with improved beam transport properties. The effect of localised power deposition and it’s reduction using tungsten liners are considered.      

Software for the international linear collider: Simulation and reconstruction frameworks

Software plays an increasingly important role already in the early stages of a large project like the ILC. In international collaboration a data format for the ILC detector and physics studies has been developed. Building upon this software frameworks are made available which ease the event reconstruction and analysis.      

The road towards the international linear collider: Higgs,top/quantum chromodynamics,loops

The international linear e ⁺ e ⁻ collider (ILC) could go into operation in the second half of the upcoming decade. Experimental analyses and theory calculations for the physics at the ILC are currently performed. We review recent progress, as presented at the LCWS06 in Bangalore, India, in the fields of Higgs boson physics and top/QCD. Also the area of loop calculations, necessary to achieve the required theory precision, is included.      

Fast and precise luminosity measurement at the international linear collider

The detectors of the ILC will feature a calorimeter system in the very forward region. The system comprises mainly two electromagnetic calorimeters: LumiCal, which is dedicated to the measurement of the absolute luminosity with highest precision and BeamCal, which uses the energy deposition from beamstrahlung pairs for a fast luminosity measure and the determination of beam parameters. The FCAL system is designed as a universal system fitting all detector concepts. It was implemented and simulated as a subsystem of the large detector concept [1]. The studies are carried out within the FCAL collaboration. http://www-zeuthen.desy.de/ILC/fcal/EUROTeV-Report-2006-095     

New developments of the R&;D silicon tracking for linear collider on silicon trackers

The status of the R&D activity achieved so far within the SiLC (silicon tracking for the linear collider) collaboration is reported here. It includes the following items: present status of the collaboration, new developments on sensors, on mechanics (new directions for module construction, large support structure, cooling, and alignment and integration issues), new lab test bench results on electronics and sensors. The perspectives over a period of four years are presented with a detailed test beam schedule and the roadmap including the construction of new mechanical prototypes equipped with front end and readout chips in deep sub-micron CMOS technology are discussed. Combined tests with other sub-detectors are finally addressed. This test beam program is inserted in the framework of the EUDET European project. on behalf of the SiLC R&D Collaboration     

The stimulated Breit-Wheeler process as a source of background <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> pairs at the international linear collider

Passage of beamstrahlung photons through the bunch fields at the interaction point of the ILC determines background pair production. The number of background pairs per bunch crossing due to the Breit-Wheeler, Bethe-Heitler and Landau-Lifshitz processes is well-known. However, the Breit-Wheeler process also takes place in and is modified by the bunch fields. A full QED calculation of this stimulated Breit-Wheeler process reveals cross-section resonances due to the virtual particle reaching the mass shell. The one-loop electron self-energy in the bunch field is also calculated and included as a radiative correction. The bunch field is considered to be a constant crossed electromagnetic field with associated bunch field photons. Resonance is found to occur whenever the energy of contributed bunch field photons is equal to the beamstrahlung photon energy. The stimulated Breit-Wheeler cross-section exceeds the ordinary Breit-Wheeler cross-section by several orders of magnitude and a significantly different pair background may result.