CERN Linear Collider Research Articles

Doubly charged Higgs from e–γ scattering in the 3-3-1 Model

We studied the production and signatures of doubly charged Higgs bosons in the process $\gamma e^- \rightarrow H^{--}E^+$, where $E^+$ is a heavy lepton, at the $e^-e^+$ International Linear Collider (ILC) and CERN Linear Collider (CLIC). The intermediate photons are given by the Weizs$\ddot{a}$cker-Williams and laser backscattering distributions. We found that significant signatures are obtained by bremsstrahlung and backward Comptom scattering of laser. A clear signal can be obtained for doubly charged Higgs bosons, doubly charged gauge bosons and heavy leptons.

Probing doubly charged Higgs bosons ine+e−colliders at the ILC and the CLIC in a 3-3-1 model

The $\mathrm{SU}(3{)}_{L}\ensuremath{\bigotimes}\mathrm{U}(1{)}_{N}$ electroweak model predicts new Higgs bosons beyond the one of the standard model. In this work we investigate the signature and production of doubly charged Higgs bosons in the ${e}^{\ensuremath{-}}{e}^{+}$ International Linear Collider and in the CERN Linear Collider. We compute the branching ratios for the doubly charged gauge bosons of the model.

Doubly charged Higgs through photon-photon collisions in 3-3-1 models

We study the production and signatures of doubly charged Higgs bosons (DCHBs) in the process $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\leftrightarrow}{H}^{--}{H}^{++}$ at the ${e}^{\ensuremath{-}}{e}^{+}$ International Linear Collider and CERN Linear Collider, where the intermediate photons are given by the Weizs\"acker-Willians and laser backscattering distributions.

3D detectors—state of the art

3D detectors, with electrodes penetrating through the silicon substrate were fabricated, and characteristics such as speed, radiation hardness and edge sensitivity were studied. The signal shape was observed using a fast, low-noise transimpedance amplifier. The rise time of the signal obtained for a minimum ionizing particle was faster than 3 ns at room temperature. This is in agreement with earlier calculations of 3D sensors that showed the charge collection time to be between 1 and 2 ns. Similar tests were performed on detectors after exposure to proton beams with doses ( 1.8 × 10 15 24 GeV protons / cm 2 ) equivalent to those expected after 10 years at the innermost layers of the ATLAS experiment at the large hadron collider (LHC). Edge sensitivity was measured at the advanced light source at Lawrence Berkeley Laboratory, using an X-ray micro-beam. The detectors were measured to be efficient up to less than 10 μ m from their physical edges. Results presented in this paper confirm the suitability of this design for possible future LHC upgrades, where the integrated fluence is expected to increase by a factor of 10. Moreover, their speed characteristics have placed them as potential candidates for the CERN linear collider (CLIC) where the bunch-crossing separation can be as short as 1.2 ns.

Photocathodes tested in the dc gun of the CERN photoemission laboratory

In the framework of the CERN linear collider project (CLIC) the CLIC test facility (CTF) uses a laser driven photocathode in an rf gun as an electron source. Photocathode properties are measured in the photoemission laboratory, which contains a preparation chamber and a dc electron gun, followed by a beam measurement line. Cathodes are illuminated by a nanosecond UV YAG laser. The present note concerns the present installation and summarises different photocathode tests on metallic as well as alkali cathodes. Those used in the rf gun of the CTF are particularly emphasized.

Present status and future of the CERN linear collider test facility (CTF)

The CLIC test facility (CTF) consists of an rf gun equipped with a laser driven photocathode and operated at 3 GHz. The rf and the picosecond laser pulse are synchronised with a timing jitter of less than 1 ps. The 4.5 MeV/ c electron beam at the gun exit is accelerated to 60 MeV/ c and then passes a prototype CLIC structure which generates 30 GHz power. A train of eight bunches with 333 ps intervals is used for high power generation. Results and improvements to and extensions of the CTF are described.

Nonperturbative fragmentation of the top quark.

By the use of a simple phenomenological string model, the energy lost by the top quark through nonperturbative fragmentation effects before its weak decay is computed. This energy lost is in first approximation proportional to the rate between the decay time and the hadronization time of the top as measured in the center-of-mass frame of the top and its color partner. Precise computations of the energy lost by the top in terms of its mass when produced in colliders such as the Fermilab Tevatron, CERN Large Hadron Collider, Superconducting Super Collider, and CERN Linear Collider are presented. As expected, this effect decreases quickly with the top mass but it could be relevant for a top mass below 100 GeV.

Use of a FEL as a buncher for a TBA scheme

The CERN linear collider (CLIC) [W. Schnell, Proc. Workshop on Physics of Linear Colliders, Capri, 1988, eds. l. Palumbo, S. Tazzari and V.G. Vaccaro (1989) p. 345] is a two-beam-accelerator (TBA) scheme in which the driving beam consists of an intense 3 to 5 GeV electron beam bunched at 30 GHz. One possible way to produce this drive beam is to start with a low-energy (or order 10 MeV), high-current (about 5 kA) beam from an induction linac. In passing through a wiggler, this beam is bunched at 30 GHz into micropulses, each with about 10 12 electrons. To construct the format required for the CLIC drive beam, the bunched beam is subsequently chopped at 350 MHz. It is then accelerated to 3 to 5 GeV in an rf linac driven by conventional, low-frequency klystrons. Rf power is extracted at the bunch frequency of 30 GHz and fed into high-gradient structures to accelerate electron or positron beams to TeV energies. The drive beam is repeatedly reaccelerated in 350 MHz superconducting cavities. This study examines the design trade-offs of the proposed “front end” of the CLIC TBA, the linear induction accelerator and FEL. We examine the relevant figure of merit, the efficiency of bunching, as a function of beam energy, current, and emittance, and we consider the effects of wiggler errors, energy spread and slew, and beam misalignment.

A proposal to use a plasma lens to achieve a 12 nm spot at the end of CLIC

We review the use of a wake field plasma lens as the final focusing element at the interaction point of the CERN linear collider (CLIC) scheme. Taking longitudinal and transverse aberrations into account we propose a set of parameters to achieve the design specification of 12 nm spot radius.

Beam-polarization phenomena in high-energy e+e- collider physics.

We consider the possible effects of a nontrivial initial-beam polarization in high-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider physics. Specifically, we address initial-beam-polarized production of possible new scalars and fermions. For definiteness, we take scalar leptons and scalar quarks as our typical new scalars and we take supersymmetric gauge-Higgs fermions as our typical fermions. In this way, we arrive at formulas which can be applied to any scalar and any fermion pair produced in lowest order in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}A$, ${Z}^{0}\ensuremath{\rightarrow}X$. We have in mind that our formulas will be used first at the SLAC Linear Collider (SLC) and the CERN collider LEP. Thus, we illustrate them in the SLC-LEP-type energy regime. Applications to the TeV Linear Collider and CERN Linear Collider are immediate and will be taken up elsewhere.