Photon production at the interaction point of the ILC

The intense beam-beam effect at the interaction point of the International Linear Collider (ILC) causes large disruption of the beams and the production of photons. These photons, arising dominantly through beamstrahlung emission, are problematic for the machine design as they need to be transported and dumped in a controlled way. In this work, we perform simulations of the beam-beam interaction to predict photon production rates and distributions for the different beam parameters considered at ILC. The results are expressed in terms of a set of cones of excluded power, allowing to define the beam-stay-clear requirements relevant for different cases and contexts. A comparison is also made with theoretical expectations. The suggested photon cone half-opening angles are 0.75 and 0.85 mrad in the horizontal and vertical planes, respectively. These cones cover all machine energies and parameter sets, and include the low power Compton photons

2D-Oide effect

The Oide effect considers the synchrotron radiation in the final focusing quadrupole and it sets a lower limit on the vertical beam size at the Interaction Point, particularly relevant for high energy linear colliders. The theory of the Oide effect was derived considering only the radiation in the focusing plane of the magnet. This article addresses the theoretical calculation of the radiation effect on the beam size consider- ing both focusing and defocusing planes of the quadrupole, refered to as 2D-Oide. The CLIC 3 TeV final quadrupole (QD0) and beam parameters are used to compare the theoretical results from the Oide effect and the 2D-Oide effect with particle tracking in PLACET. The 2D-oide demonstrates to be important as it increases by 17% the contribution to the beam size. Further insight into the aberrations induced by the synchrotron radiation opens the possibility to partially correct the 2D-Oide effect with octupole mag

Experimental Implications for a Linear Collider of the SUSY Dark Matter Scenario

This paper presents the detection issues for the lightest slepton \tilde{\tau}_1 at a future e^+e^- TeV collider given the dark matter constraints set on the SUSY mass spectrum by the WMAP results. It intends to illustrate the importance of an optimal detection of energetic electrons in the very forward region for an efficient rejection of the \gamma\gamma background. The TESLA parameters have been used in the case of head-on collisions and in the case of a 10, mrad half crossing angle.Comment: 24 pages, 13 figures, Work presented at the International Conference on Linear Colliders (LCWS04), 19-23 April 2004, Le Carre des Sciences, Paris, Franc

Particle tracking in the ILC extraction lines with DIMAD and BDSIM

The study of beam transport is of central importance to the design and performance assessment of modern particle accelerators. In this paper, we benchmark two contemporary codes, DIMAD and BDSIM, the latter being a relatively new tracking code built within the framework of GEANT4. We consider both the 20 mrad and 2 mrad extraction lines of the 500 GeV International Linear Collider (ILC) and we perform particle tracking studies of heavily disrupted post-collision electron beams. We find that the two codes give an almost equivalent description of the beam transport

Benchmarking of Tracking Codes (BDSIM/DIMAD) using the ILC Extraction Lines

The study of beam transport is of central importance to the design and performance assessment of modern particle accelerators. In this work, we benchmark two contemporary codes - DIMAD and BDSIM, the latter being a relatively new tracking code built within the framework of GEANT4. We consider both the 20 mrad and 2 mrad extraction lines of the International Linear Collider (ILC) and we perform tracking studies of heavily disrupted post-collision electron beams. We find that the two codes mostly give an equivalent description of the beam transport.Comment: Contribution to the Tenth European Particle Accelerator Conference `"EPAC'06'', Edinburgh, United-Kingdom, 26-30 June 200

Fast Luminosity Monitoring using Diamond Sensors for Super Flavour Factories

MOPME004 - ISBN 978-3-95450-122-9International audienceSuper flavour factories aim to reach very high luminosities thanks to a new concept whereby the ultra-low emittance beams collide with a large crossing angle. Fast luminosity measurements are needed as input to luminosity optimization and feedback in the presence of dynamic imperfections. The required small relative precision can be reached exploiting the very large cross section of the radiative Bhabha process at zero photon scattering angle. The instrumental technique selected to sustain the large particle fluxes is based on diamond sensors to be positioned viamoveable stages immediately outside the beam pipe, at locations chosen to minimize the contamination from other particle loss mechanisms

Study of time-dependent corrections in the ATF2 beam-line

International audienceGoals of ATF2 will be to provide beams with a few tens of nanometers and stability at the nanometer level. To achieve this, ground motion should be measured and the effects of element displacement on the beam at the Interaction Point (IP) should be well understood. Feedback systems should also be simulated with a gound motion generator which includes spatial coherence for effects to be computed realistically

Optical configurations with variable β* at different IP locations in ATF2

During ATF2 commissioning, it will be important to focus the beam to a proper waist at IP locations both upstream and downstream of the nominal one, where different beam size monitors will be placed with typical resolutions larger than that of the Shintake monitor at the nominal IP. In this note, a method to obtain optical configurations with variable β* at these different IP locations is described, enabling to match the measurement resolutions of these monitors with the linear beam size at the waist, while attempting to retain the overall features of the local chromaticity correction in the final focus optics. During commissioning, it is expected that one will gradually reduce β* after measurements at these different locations

The Impact of BeamCal Performance at Different ILC Beam Parameters and Crossing Angles on \tilde{tau} searches

The ILC accelerator parameters and detector concepts are still under discussion in the world-wide community. As will be shown, the performance of the BeamCal, the calorimeter in the very forward area of the ILC detector, is very sensitive to the beam parameter and crossing angle choices. We propose here BeamCal designs for a small (0 or 2 mrad) and large (20 mrad) crossing angles and report about the veto performance study done. As illustration, the influence of several proposed beam parameter sets and crossing-angles on the signal to background ratio in the stau search is estimated for a particular realization of the super-symmetric model.Comment: Talk given by V. Drugakov at the Linear Collider Workshop "LCWS06'', 9-13 March 2006, I.I.Sc Bangalore, Indi

Backscattering of secondary particles into the ILC detectors from beam losses along the extraction line

online : http://cern.ch/AccelConf/p07/PAPERS/THPMN009.PDFInternational audienceAt the International Linear Collider (ILC) the beams will be focused to extremely small spot sizes in order to achieve the desired luminosity. After the collision the beams must be brought to the dump with minimal losses. In spite of all the attention put into the design of the extraction line, the loss of some disrupted beam particles, beamstrahlung or synchrotron radiation photons is unavoidable. These losses will generate low-energy secondary particles, such as photons, electrons and neutron, a fraction of which can be back-scattered towards the Interaction Point (IP) and generate backgrounds into the detector. In this paper we present an evaluation of such backgrounds, using the BDSIM [1] and Mokka [2] simulations. The event reconstruction in the detector is made with the MarlinReco package from the Marlin tool [3]