Search

We introduce a numerical package FORward Experiment SEnsitivity Estimator, or FORESEE, that can be used to simulate the expected sensitivity reach of experiments placed in the far-forward direction from the proton-proton interaction point. The simulations can be performed for $14$ TeV collision energy characteristic for the LHC, as well as for larger energies: $27$ and $100$ TeV. In the package, a comprehensive list of validated forward spectra of various SM species is also provided. The capabilities of FORESEE are illustrated for the popular dark photon and dark Higgs boson models, as well as for the search for light up-philic scalars. For the dark photon portal, we also comment on the complementarity between such searches and dark matter direct detection bounds. Additionally, for the first time, we discuss the prospects for the LLP searches in the proposed future hadron colliders: High-Energy LHC (HE-LHC), Super proton-proton Collider (SppC), and Future Circular Collider (FCC-hh)., 11 pages, 3 figures, FORESEE code available at https://github.com/KlingFelix/FORESEE

In this paper, we study the electroproduction of open heavy flavor $D$ and $B$ mesons in the kinematics of future $ep$ colliders, such as the Electron Ion Collider (EIC), the Large Hadron electron Collider (LHeC), and the Future Circular Collider (FCC-he). We study in detail the dependence of the cross sections on multiplicity of coproduced hadrons, in view of its possible sensitivity to contributions from multi-Pomeron contributions, and discuss different observables which might be used for its study. According to our theoretical expectations, in $ep$ collisions the multi-Pomeron contributions are small in the EIC kinematics, although they might be sizable at LHeC and FCC-he. We also provide theoretical predictions for the production cross sections of heavy mesons in the kinematics of all the above-mentioned $ep$ colliders.

In response to recommendations in the 2013 update of the European Strategy for Particle Physics, a conceptual design effort for an energy upgrade of the Large Hadron Collider (LHC) at CERN, the so-called high-energy LHC (HE-LHC), was launched as part of the Future Circular Collider study. The HE-LHC machine, which is meant to use 16 T magnet technologies in the existing LHC tunnel, would provide proton collisions at a center-of-mass energy of 27 TeV ($\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}\mathrm{LHC}$) with a total stored energy of 1.34 GJ ($\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}\mathrm{LHC}$) per beam. By adapting the LHC collimation system, a first layout of the HE-LHC's betatron cleaning insertion was conceived, with the requirement to sustain---for at least 10 seconds---the impact of about 1.86 MW, corresponding to a beam lifetime of 12 minutes, without inducing any magnet quench nor any damage to other accelerator components. In this article, we evaluate the power deposition on the collimation insertion for proton beam operation in the HE-LHC machine at top energy, by means of particle tracking and interaction calculations. The beam loss effects on the warm elements as well as on the superconducting dispersion suppressor magnets are assessed through a three-step simulation approach. In particular, for the proposed future high-energy LHC, we demonstrate the necessity of adding local collimators in the dispersion suppressor, and we uncover the harmful consequences of a potential removal of the beam line ``dogleg'' in the collimation insertion.

In this work, we study the future probes of the complex singlet extension to the standard model (cxSM). This model is possible to realize a strongly first-order electroweak phase transition. The cxSM naturally provides the dark matter candidate, with or without an exact ${\mathbb{Z}}_{2}$ symmetry in the scalar sector. The benchmark models which can realize the strongly first-order electroweak phase transition are selected and passed to the current observational constraints to the dark matter candidates, including the relic densities and the direct detection limits set by the latest XENON1T results. We then calculate the one-loop corrections to the SM-like Higgs boson decays and the precision electroweak parameters due to the cxSM scalar sector. We perform a global fit to the benchmark models and study the extent to which they can be probed by the future high-energy ${e}^{+}{e}^{\ensuremath{-}}$ colliders, such as Circular Electron Positron Collider and Future Circular Collider. Besides, the gravitational wave signals generated by the benchmark models are also evaluated. We further find that the future gravitational wave detector, such as LISA, is complementary in probing the benchmark models that are beyond the sensitivity of the future precision tests at the ${e}^{+}{e}^{\ensuremath{-}}$ colliders.

We investigate the sensitivity of future searches for the top-Higgs boson Flavour Changing Neutral Current (FCNC) couplings $tqh$~($q= u, c$) at the proposed High Energy Large Hadron Collider~(HE-LHC) and Future Circular Collider in hadron-hadron mode (FCC-hh). We perform a full simulation for two processes in the $h\to \gamma\gamma$ decay channel (where $h$ is the discovered Higgs state): single top quark FCNC production in association with the Higgs boson (plus a jet) and top quark pair production with FCNC decays $t\to qh$. All the relevant backgrounds are considered in a cut based analysis to obtain the limits on the Branching Ratios (BRs) of $t\to uh$ and $t\to ch$. It is shown that, at the HE-LHC with an integrated luminosity of 15 ab$^{-1}$ and at the FCC-hh with an integrated luminosity of 30 ab$^{-1}$, {{the BR($t\to uh$) (BR($t\to ch$)) can be probed, respectively, to $7.0~(8.5)\times 10^{-5}$ and $2.3~(3.0) \times 10^{-5}$ at the 95\% Confidence Level (CL) (assuming a 10\% systematic uncertainty on the background), which is almost two orders of magnitude better than the current 13 TeV LHC experimental results.

We analyse the possibilities for the study of inclusive diffraction offered by future electron--proton/nucleus colliders in the TeV regime, the Large Hadron-electron Collider as an upgrade of the HL-LHC and the Future Circular Collider in electron-hadron mode. Compared to $ep$ collisions at HERA, we find an extension of the available kinematic range in $x$ by a factor of order $20$ and of the maximum $Q^2$ by a factor of order $100$ for LHeC, while the FCC version would extend the coverage by a further order of magnitude both in $x$ and $Q^2$. This translates into a range of available momentum fraction of the diffractive exchange with respect to the hadron ($\xi$), down to $10^{-4}-10^{-5}$ for a wide range of the momentum fraction of the parton with respect to the diffractive exchange ($\beta$). Using the same framework and methodology employed in previous studies at HERA, considering only the experimental uncertainties and not those stemming from the functional form of the initial conditions or other ones of theoretical origin, and under very conservative assumptions for the luminosities and systematic errors, we find an improvement in the extraction of diffractive parton densities from fits to reduced cross sections for inclusive coherent diffraction in $ep$ by about an order of magnitude. For $eA$, we also perform the simulations for the Electron Ion Collider. We find that an extraction of the currently unmeasured nuclear diffractive parton densities is possible with similar accuracy to that in $ep$., Comment: 24 pages, 16 figures

The design of a compact crab cavity using Nb/Cu technology is presented. The cavity shape is based on a ridged waveguide resonator with wide-open apertures to provide access to the inner surface of the cavity and facilitate coating. It also provides natural damping for higher-order modes (HOMs) and comparatively low longitudinal and transverse impedances. A first prototype is being fabricated, originally within the HL-LHC framework and now for the Future Circular Collider study. The optimized shape is characterized and compared with respect to peak surface field balance, multipolar momentum components, and longitudinal and transverse impedances. Further investigations include the identification of multipacting barriers, the frequency sensitivity to pressure fluctuations in the helium bath, the radio frequency (rf) design of a fundamental mode coupler, and considerations of HOM damping. Along these topics, several methods have been established serving a wider range of applications, in particular, for the rf loss evaluation, the postprocessing of multipacting simulations, and a detailed error analysis of the pressure sensitivity simulations.

The search for the light Higgsino in the minimal supersymmetric standard model is a crucial test of the naturalness criteria in supersymmetry. On the other hand, the direct production of light Higgsinos is also known as one of the most challenging supersymmetry searches at the LHC. The lack of visible leptons due to the compressed spectrum and their small production rates limit their discovery potential in both monojet plus ET events and weak boson fusion (WBF) production. The signal-to-background ratio prediction is usually within the background systematic uncertainties at the LHC. Without color exchange between the beams, e−p colliders are well known to exhibit WBF. Therefore, we search for light Higgsinos at two future e−p colliders at CERN: the Large Hadron electron Collider (LHeC) and the Future Circular Collider in hadron-electron mode (FCC-eh). The light Higgsinos will be produced in pairs through weak boson fusion with controlled background at these colliders. We find that a 95/145 GeV Higgsino can be reached at the 2σ level at the future LHeC/FCC-eh with a luminosity of 3 ab−1, respectively.

We calculate the production of prompt and thermal photons from $\text{Pb}+\text{Pb}$ collisions at $5.02A$ TeV at the Large Hadron Collider (LHC) and at $39A$ TeV at the proposed Future Circular Collider (FCC) facility. The photon spectra and anisotropic flow at these energies are compared with the results obtained from $2.76A$ TeV $\text{Pb}+\text{Pb}$ collisions at the LHC for three different centrality bins. The prompt photons originating from initial hard scatterings are found to increase by a factor of 1.5 to 2 at $5.02A$ TeV in the ${p}_{T}$ region 2 to 15 GeV and the enhancement is found to be about 5 to 15 times at FCC energies compared with $2.76A$ TeV in the same ${p}_{T}$ region. The evolution of the quark-gluon plasma (QGP) formed in $\text{Pb}+\text{Pb}$ collisions at LHC and FCC energies are studied by using a hydrodynamical model and the ${p}_{T}$ spectra and elliptic flow of thermal photons are calculated using state-of-the-art photon rates. The relative enhancement in the production of thermal photons is found to be more compared with prompt photons at FCC than at the LHC energies. Although the production of direct (prompt + thermal) photons is found to enhance significantly with increase in beam energy, the photon elliptic flow increases only marginally and does not show strong sensitivity to the collision energy.

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.

In this paper we investigate the exotic charmonium production in $\ensuremath{\gamma}\ensuremath{\gamma}$ interactions present in proton-proton, proton-nucleus, and nucleus-nucleus collisions at the CERN Large Hadron Collider energies as well as for the proposed energies of the Future Circular Collider. Our results demonstrate that the experimental study of these processes is feasible and can be used to constrain the theoretical decay widths and shed some light on the configuration of the considered multiquark states.

The use of resonant depolarization has been suggested for precise beam energy measurements (better than 100 keV) in the $e^{+}e^{-}$ Future Circular Collider (FCC-$e^{+}e^{-}$) for Z and WW physics at 45 and 80 GeV beam energy respectively. Longitudinal beam polarization would benefit the Z peak physics program; however it is not essential and therefore it will be not investigated here. In this paper the possibility of self-polarized leptons is considered. Preliminary results of simulations in presence of quadrupole misalignments and beam position monitors (BPMs) errors for a simplified FCC-$e^{+}e^{-}$ ring are presented.

The hadron collider studied in the Future Circular Collider (FCC) project could operate with protons and lead ions in similar operation modes as the LHC. In this paper the potential performances in lead-lead, proton-lead and proton-proton collisions are investigated. Based on average lattice parameters, the strengths of intra-beam scattering and radiation damping are evaluated and their effect on the beam and luminosity evolution is presented. Estimates for the integrated luminosity per fill and per run are given, depending on the turnaround time. Moreover, the beam-beam tune shift and bound free pair production losses in heavy-ion operation are addressed.