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The e-e- running mode is one of the interesting physics options at the International Linear Collider (ILC). The luminosity for e-e- collisions is reduced by the beam-beam effects. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are different compared to the e+e- collisions. In this paper, the dependence of these observables with the offset for different beam sizes has been analyzed to optimize performances for the e-e- mode, taking into account the requirements of the beam-beam deflection based intra-train feedback system. A first study of the implications for the final focus and extraction line optics is also presented for the cases of the 20 mrad and 2 mrad ILC base line crossing angle geometries.
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We present results from luminosity, energy and polarization studies at a future Linear Collider. We compare e+e- and e-e- modes of operation and consider both NLC and TESLA beam parameter specifications at a center-of-mass energy of 500 GeV. Realistic colliding beam distributions are used, which include dynamic effects of the beam transport from the Damping Rings to the Interaction Point. Beam-beam deflections scans and their impact for beam-based feedbacks are considered. A transverse kink instability is studied, including its impact on determining the luminosity-weighted center-of-mass energy. Polarimetry in the extraction line from the IP is presented, including results on beam distributions at the Compton IP and at the Compton detector.
The international Future Circular Collider (FCC) study aims at a design of $pp$, $e^+e^-$, $ep$ colliders to be built in a new 100 km tunnel in the Geneva region. The $e^+e^-$ collider (FCC-ee) has a centre of mass energy range between 90 (Z-pole) and 375 GeV (tt_bar). To reach such unprecedented energies and luminosities, the design of the interaction region is crucial. The crab-waist collision scheme has been chosen for the design and it will be compatible with all beam energies. In this paper we will describe the machine detector interface layout including the solenoid compensation scheme. We will describe how this layout fulfills all the requirements set by the parameters table and by the physical constraints. We will summarize the studies of the impact of the synchrotron radiation, the analysis of trapped modes and of the backgrounds induced by single beam and luminosity effects giving an estimate of the losses in the interaction region and in the detector.
A beam optics scheme has been designed for the Future Circular Collider-e+e- (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme [1] with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So-called tapering of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) [2] as closely as possible. Sufficient transverse/longitudinal dynamic aperture (DA) has been obtained, including major dynamical effects, to assure an adequate beam lifetime in the presence of beamstrahlung and top-up injection. In particular, a momentum acceptance larger than +/-2% has been obtained, which is better than the momentum acceptance of typical collider rings by about a factor of 2. The effects of the detector solenoids including their compensation elements are taken into account as well as synchrotron radiation in all magnets. The optics presented in this paper is a step toward a full conceptual design for the collider. A number of issues have been identified for further study.
The 1-loop effects of the MSSM at the ILC are investigated through numerical analysis. We studied the higgs production processes $e^-e^+rightarrow Zh$ and $e^-e^+rightarrow ubar{ u}h$ at the ILC. It is found that the magnitude of the MSSM contribution through the 1-loop effects is sizable enough to be detected. In the study, three sets of the MSSM parameters are proposed, which are consistent with the observed higgs mass, the muon $g$-$2$, the dark matter abundance and the decay branching ratios of $B$ mesons. In the $e^-e^+rightarrow Zh$ process, the 1-loop effects of the MSSM are visible and the distinction of the parameter sets is partially possible. For the study of $e^-e^+rightarrow ubar{ u}h$, we used the equivalent $it W$-boson approximation in the evaluation of the 1-loop cross section. While the 1-loop effect of the MSSM is visible, the distinction of the parameter sets might not be possible in this process under the value of realistic luminosity at the ILC.
By using the GRACE-Loop system, we calculate the full $mathcal{O}(alpha)$ electroweak radiative corrections to the process $e^+e^- rightarrow e^+e^- gamma$, which is important for future investigations at the International Linear Collider (ILC). With the GRACE-Loop system, the calculations are checked numerically by three consistency tests: ultraviolet finiteness, infrared finiteness, and gauge-parameter independence. The results show good numerical stability when quadruple precision is used. In the phenomenological results, we find that the electroweak corrections to the total cross section range from $sim -4%$ to $sim -21%$ when $sqrt{s}$ varies from $250$ GeV to $1$ TeV. The corrections also significantly affect the differential cross sections, which are a function of the invariant masses and angles and the final-particle energies. Such corrections will play an important role for the high-precision program at the ILC.
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