Updated studies of the luminosity performance of CLIC

As well as contributing to the upgrade of the Large Hadron Collider (LHC),
researchers at the JAI are helping to design its possible replacement. In a new paper, members of the JAI, working with researchers from CERN, have shown how the luminosity performance of the Compact Linear Accelerator (CLIC) could be significantly
higher than its design target.

CLIC is one of the two main European options for a next generation high energy collider. Unlike the LHC, where two beams of protons are collided, CLIC will collide a beam of electrons with a beam of their antimatter cousins, positrons. By colliding these
beams to a centre of mass energy of 380 GeV, CLIC intends to probe the properties of particles like the top quark and the Higgs boson with never before seen levels of precision.

Colliding electrons and positrons does throw up many different technical hurdles to protons. One of the main challenges is that due to their low mass, electrons radiate significant amounts of so called synchrotron radiation when bent around the curved
tunnel of a circular collider. The shear amount of radiation emitted means that high energy circular electron accelerators are inefficient and require a lot of electrical power to run. By accelerating the electron and positron beams along a straight
line measuring 11 km in length, CLIC manages to avoid this problem entirely.

However, unlike in circular colliders where the beams circulate for hours and hours colliding every time they arrive back in the detector, the beams in linear colliders only collide once. In order to reach the same particle collision rate, something known
to physicists as luminosity, CLIC must collide its two beams over a much smaller area than a circular collider. To collide over this area, measuring only a few nanometres across, the beams must be controlled very precisely, correcting for everything
from misalignments in the machine components to the movement of the earth itself.

The new paper, which can be viewed here, the team was able to show how these
imperfections can be corrected for in CLIC. They were able to calculate the achievable luminosity for CLIC with fully realistic tracking simulations of the accelerator. The average expected luminosity they calculated is 2.8×10³⁴cm⁻²s⁻¹,
which is almost twice the nominal luminosity target of CLIC. The lead author of the paper, Dr. Chet Gohil from the university of Oxford, remarked that,

Luminosity estimates for CLIC presented in the past have been relatively conservative. This paper reports detailed and thorough simulations that show almost double the expected luminosity could be achieved!