Physics possibilities at a linear collider

We review some recent studies about the parameter determination of top quarks,W bosons, Higgs bosons, supersymmetric particles and in the ADD model of extra dimensions at a linear collider.     

Physics at the linear collider

The physics at the plannede ⁺ e ^- colliders is discussed around three main topics corresponding to different manifestations of symmetry breaking:W physics in the no Higgs scenario, studies of the properties of the Higgs and precision tests of SUSY. A comparison with the LHC is made for all these cases. The γγ mode of the linear collider will also be reviewed.     

Heavy quark production at a photon linear collider

Heavy quark production at future Compton colliders is investigated. The impact of polarization has been studied. Perturbative QCD corrections to the effective cross section are calculated and found to be at the level of 40% for ae ⁺ e ^? collider of 500 GeV and a top quark mass of 150 GeV. The η _t resonance structure is incorporated.     

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.      

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.      

Cross sections for multi-particle final states at a linear collider

In this paper total cross sections for signals and backgrounds of top- and Higgs-production channels in e ⁺ e^- collisions at a future linear collider are presented. All channels considered are characterized by the emergence of six-particle final states. The calculation takes into account the full set of tree-level amplitudes in each process. Two multi-purpose parton level generators, HELAC/PHEGAS and AMEGIC + + , are used, and their results are found to be in perfect agreement.Received: 26 November 2003, Revised: 15 January 2004, Published online: 3 March 2004     

Physics prospects at a linear e + e − collider

The talk described the prospects of studying standard model parameters as well as scenarios beyond the standard model, like the minimal supersymmetric standard model, theories with extra dimensions and theories with extra neutral gauge bosons, at a future linear e ⁺ e ⁻ collider.     

One-loop electroweak factorizable correctionsfor the Higgsstrahlung at a linear collider

We present standard model predictions for the four-fermion reaction being one of the best detection channels of a low-mass Higgs boson produced through the Higgsstrahlung mechanism at a linear collider. We include leading virtual and real QED corrections due to initial state radiation and a modification of the Higgs- Yukawa coupling, caused by the running of the b-quark mass, for . The complete electroweak corrections to Z-Higgs production and to the Z-boson decay width, as well as the remaining QCD and EW corrections to the Higgs decay width, as can be calculated with the program HDECAY, are taken into account in the double-pole approximation. Received: 17 March 2005, Revised: 30 March 2005, Published online: 30 August 2005 Work supported in part by the Polish State Committee for Scientific Research in years 2004-2006 as a research grant, by the European Community's Human Potential Program under contracts HPRN-CT-2000-00149 Physics at Colliders and CT-2002-00311 EURIDICE, and by DFG under Contract SFB/TR 9-03.     

Studying trilinear gauge couplings at linear collider energies

We investigate the sensitivity of the semileptonic processes , , on the non-standard trilinear gauge couplings, using the optimal observables method at Linear Collider energies. Our study is based on the four-fermion generator ERATO. Taking into account all possible correlations between the different trilinear gauge coupling parameters, we show that they can be measured with an accuracy of to for typical Linear Collider energies and luminosities. Received: 9 April 1997 / Revised version: 18 June 1997     

Particle flow calorimetry at the international linear collider

One of the most important requirements for a detector at the ILC is good jet energy resolution. It is widely believed that the particle flow approach to calorimetry is the key to achieving the goal of 0.3/√E(GeV). This paper describes the current performance of the PandoraPFA particle flow algorithm. For 45 GeV jets in the Tesla TDR detector concept, the ILC jet energy resolution goal is reached. At higher energies the jet energy resolution becomes worse and can be described by the empirical expression: σ _E /E ≈ 0.265/√E(GeV) + 1.2 × 10⁻⁴ E(GeV).      

Signals of spontaneous R parity breaking at LEP and at a linear collider

We study the production of neutralinos and charginos at LEP and at a linear collider in the case of spontaneously broken R-parity. We first investigate the constraints on the single neutralino and chargino production from the LEP 1 experiments, and then we consider the production at LEP 2 and at a linear collider. We concentrate on the supersymmetric model, where the spontaneous R-parity breaking is inevitable and is associated with the breaking of the LR-symmetry. Received: 26 February 1998 / Published online: 9 April 1998     

MSSM Higgs bosons at a future linear collider. Heavy quark production at HERA

The European Physical Journal C - We study the potential of the future e + e - linear collider operated at a center-of-mass energy of 500 to 1000 GeV for the measurement of the neutral Higgs boson...     

Probing universal extra dimension at the international linear collider

We consider the UED scenario and study the detectability of the first KK electron-positron pair at the ILC. A few hundred GeV KK electron decays into a nearly degenerate KK photon, which carries away missing energy, and the standard electron. The mass splitting between the KK electron and KK photon is controlled by the bulk-and brane-induced radiative corrections. We look for the signal event e ⁺ e ⁻ + large missing energy for √s = 1 TeV and observe that with a few hundred fb⁻¹ luminosity the signal can be deciphered from the standard model background. We briefly outline how the UED signals may be distinguished from the supersymmetric signals. This talk is based on a work the author did with Paramita Dey, Anirban Kundu and Amitava Raychaudhuri [1].     

Associated stop-Higgs production at a linear collider and extraction of stop parameters

We calculate stop-stop-Higgs production at a linear collider. Combining the measurements from the pair production of the lightest stop and that of the mass of the Higgs, we show how, in a scenario where only the lightest stop and the lightest Higgs are accessible, one could extract the mass of the heavier stop and infer some useful information on the supersymmetric parameters. Received: 19 November 1998 / Published online: 18 June 1999     

Heavy neutrino mixing and single production at linear collider

We study the single production of heavy neutrinos via the processes e⁻e⁺ → νN and e⁻γ → W⁻N at future linear colliders. As a base of our considerations we take a wide class of models, both with vanishing and non-vanishing left-handed Majorana neutrino mass matrix m_L. We perform a model independent analyses of the existing experimental data and find connections between the characteristic of heavy neutrinos (masses, mixings, CP eigenvalues) and the m_L parameters. We show that with the present experimental constraints heavy neutrino masses almost up to the collision energy can be tested in the future experiments.