Future Circular Hadron Collider Research Articles

Performance of 3D trench silicon pixel sensors irradiated up to [formula omitted]

Tracking particles at extreme fluences requires the accurate measurement of the charged particle timing at the pixel level in order to cope with the increased occupancy of HL-LHC experiments. Maintaining this precision throughout the operational life of the detector is crucial. This work demonstrates that the 55×55μm2 wide 150μm thick 3D trench-type pixels, developed by the TimeSPOT Collaboration, maintain the performance of non-irradiated sensors even after exposure to fluences as high as 1⋅10171MeVneqcm−2. The preliminary results of a beam test characterization using minimum ionizing particles at the SPS North area beam facility reveal that the charge collection and the time resolution of the irradiated sensors are comparable to those of non-irradiated ones, by increasing the operational bias voltage. A minor reduction in detection efficiency, approximately 4%, is observed post-irradiation. Currently, 3D trench-type pixels are among the fastest pixel detectors available for tracking charged particles and hold significant promise for future tracking system upgrades. This preliminary evaluation suggests their suitability for use in even harsher radiation environments than High Luminosity Large Hadron Collider (HL-LHC) such as future experiments at the Future Circular Hadron Collider (FCC-hh).

A simulated search for the singlet vector-like bottom quark decaying into tW at high energy pp colliders

In a framework of simplified model, we perform a simulated search for the singlet vector-like bottom quark B decaying into tW with t hadronic decay and W leptonic decay at the 14 TeV high-luminosity LHC (HL-LHC), 27 TeV high energy LHC (HE-LHC) and 100 TeV Future Circular Hadron Collider (FCC-hh). In this work, we focus on the case that the B only couples with the third generation quarks of the Standard Model. We make a detailed detector simulations of the signal and backgrounds and obtain the 2sigma exclusion limit and 5sigma discovery prospects. Our results show that the upcoming HL-LHC can exclude (discover) the m_B to 2100 (1900) GeV for a typical coupling strength g^{*}=0.2. For the HE-LHC (FCC-hh), this exclusion capability on the B quark mass can be expanded to more than 3000 (5000) GeV.

Single vector-like quark X production in the tW channel at high energy pp colliders

Vector-like quarks (VLQs) are color-triplet spin-1/2 fermions whose left- and right-handed chiral components have the same transformation properties under the weak-isospin SU(2) gauge group. The X vector-like particle with a charge of |Q|=+5/3 exists in the (X,T) doublet or (X,T,B) triplet states. Based on a simplified model, we investigate the prospect of discovering the doublet right-handed X via the single production of X followed by X→tW at the 14 TeV High Luminosity LHC (HL-LHC), 27 TeV High Energy LHC (HE-LHC), and 100 TeV hadron-hadron Future Circular Hadron Collider (FCC-hh). We perform a detailed detector simulation, and find that the excluding and discovering capabilities on the X quark are enhanced obviously with the increase of collision energy. Assuming the system uncertainty is 30% of the number of the background events, the excluding capabilities are given as follows: (1) the HL-LHC can exclude the correlated regions of the mixing constant sin⁡θR∈[0.082,0.2] and the X quark mass mX ∈ [1000 GeV, 1680 GeV] with L=3 ab−1; (2) the HE-LHC can exclude the correlated regions of sin⁡θR∈[0.067,0.2] and mX ∈ [1000 GeV, 2230 GeV] with L=15 ab−1; (3) the FCC-hh can exclude the correlated regions of sin⁡θR∈[0.078,0.2] and mX ∈ [1000 GeV, 2560 GeV] with L=30 ab−1.

Field quality and surface resistance studies of a superconducting REBa2Cu3O7−x —Cu hybrid coating for the FCC beam screen

To ensure beam stability in the future circular collider study of the European Organization for Nuclear Research, RE(=Y, Gd, Eu)Ba2Cu3O 7−x high-temperature superconductor was proposed as a low-surface impedance coating for its beam screen. Unfortunately, persistent currents in the superconductor will degrade the magnetic field homogeneity inside the beam chamber, endangering the stability of the beam trajectory. To counteract this effect, we have explored the possibility of using a highly conductive hybrid coating made of Cu and REBa2Cu3O 7−x . This decreases the surface impedance when compared to that of pure copper, while maintaining high magnetic field quality inside the beam screen chamber. This work formulates guidelines for hybrid coating geometries to comply with the field quality criterion of a circular accelerator during operation with dipole magnets by means of finite elements numerical analysis. We produced hybrid coating samples with compliant geometries via photolithography. Scanning Hall microscopy and radio-frequency characterization have given the first experimental confirmation that these hybrid coatings offer high field quality and present a surface resistance lower than that of copper for the beam screen of the future circular hadron collider. The excellent agreement shown between experimental results and simulations validates that the numerical analysis performed throughout this work can be used as a prediction tool for future proposed geometries.

Exploring the potential of FCC-hh to search for particles from B mesons

The Future Circular hadron Collider (FCC-hh) is a proposed successor of the Large Hadron Collider (LHC). FCC-hh would push both the energy and intensity frontiers of searches for new physics particles. In particular, due to higher energy and luminosity than at the LHC, at FCC-hh there would be produced around ≃ 30 times larger amount of B mesons and ≃ 120 times of W bosons, which then may decay into feebly interacting particles. In this paper we demonstrate the potential of FCC-hh by studying its sensitivity to heavy neutral leptons (HNLs) with masses mN< mB. We consider various locations of a displaced decay volume embedded in the planned infrastructure of FCC-hh. We demonstrate that FCC-hh may substantially improve the reach of the parameter space of HNLs as compared to the searches proposed at the LHC.

Potential impedance reduction by REBCO-coated conductors as beam screen coating for the Future Circular Hadron Collider

The Future Circular Collider study creates a conceptual design for a post-LHC particle accelerator using 16 T superconducting dipoles to achieve collision energies of up to 100 TeV in a 90 km circumference ring. A copper-coated beam screen, similar to that used in the LHC, is planned. However, the undertaken research indicates that copper at the high working temperature of 50 K has a strong influence on the accelerator's performance, particularly at injection energy. In this work, we relate the experimentally determined properties of REBCO-coated conductors with their potential performance in the FCC-hh beam screen. Specifically, we use a round pipe approximation to demonstrate that a beam screen coated with a combination of REBCO and copper can have a much lower resistive wall impedance than one using only copper. The reduction is substantial (several orders of magnitude), and is observed in both the longitudinal and transverse wall impedance. Such a reduction has important effects on beam stability, operating costs, potential reduction in beam screen size, and lowering the stringent specifications of the 16 T magnets required for the Future Circular Hadron Collider.

Considerations on combined-function optics for high-energy storage rings and colliders

In a recent paper, the proposal of using combined-function optics for the arcs of the Future Circular hadron Collider (FCC–hh) was presented and discussed in detail. In this paper, further considerations are presented on the same topic, reflecting the progress made since the previous publication. The studies presented here focus mainly on two aspects. Firstly, the layout of the combined-function periodic cell is optimised with the goal of fixing the number of main magnets. Secondly, possible layouts of the dispersion suppressor in the framework of this novel proposal for the optics of the arcs of the FCC hadron collider.

Single vectorlike top quark production in the tZ channel at high energy pp colliders

In a simplified model including a singlet vectorlike top quark $T$ with charge $|\mathrm{Q}|=2/3$, we investigate the single production of $T$ decaying into $tZ$ at the 14 TeV LHC, 27 TeV high energy LHC (HE-LHC), and 100 TeV hadron-hadron Future Circular Hadron Collider (FCC-hh). In the four flavor scheme, we make detailed detector simulations and the background analysis. We find that the excluding and discovering capability is enhanced obviously with the increase of the collision energy. The model includes only two free parameters, the coupling constant ${g}^{*}$, and top quark partner mass ${m}_{T}$. For the highest integrated luminosity designed, the excluding capability can be given as follows: (1) the LHC can exclude the correlated regions ${g}^{*}\ensuremath{\in}[0.085,0.50]$ with ${m}_{T}\ensuremath{\in}[1000\text{ }\text{ }\mathrm{GeV},1840\text{ }\text{ }\mathrm{GeV}]$ for $\mathcal{L}=3000\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$; (2) the HE-LHC can exclude the correlated regions ${g}^{*}\ensuremath{\in}[0.035,0.50]$ with ${m}_{T}\ensuremath{\in}[1000\text{ }\text{ }\mathrm{GeV},2610\text{ }\text{ }\mathrm{GeV}]$ for $\mathcal{L}=15\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$; (3) the FCC-hh can exclude the correlated regions ${g}^{*}\ensuremath{\in}[0.005,0.50]$ with ${m}_{T}\ensuremath{\in}[1000\text{ }\text{ }\mathrm{GeV},4270\text{ }\text{ }\mathrm{GeV}]$ for $\mathcal{L}=30\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$. Besides, we find that the excluding and discovering regions will be reduced if the narrow width approximation limit is considered.

A muon–ion collider at BNL: The future QCD frontier and path to a new energy frontier of [formula omitted] colliders

We propose the development and construction of a novel muon–ion collider (MuIC) at Brookhaven National Laboratory (BNL) in the USA as an upgrade to succeed the electron–ion collider (EIC) that is scheduled to commence in the early 2030s, by a joint effort of the nuclear and particle physics communities. The BNL facility could accommodate a muon storage beam with an energy up to about 1 TeV with existing magnet technology. When collided with a 275 GeV hadron beam, the MuIC center-of-mass energy of about 1 TeV will extend the kinematic coverage of deep inelastic scattering physics at the EIC (with polarized beams) by more than an order of magnitude in Q2 and x, opening a new QCD frontier to address many fundamental scientific questions in nuclear and particle physics. This coverage is comparable to that of the proposed Large Hadron–Electron Collider (LHeC) at CERN, but with complementary lepton and hadron kinematics, ion species, and beam polarization. Additionally, the development of a MuIC at BNL will focus the worldwide R&D efforts on muon collider technology and serve as a demonstrator toward a future muon–antimuon collider at O(10) TeV energy, which is an attractive option to reach the next high energy frontier in particle physics at an affordable cost and a smaller footprint than a future circular hadron collider. We discuss here the possible design parameters of the MuIC, kinematic coverage, science cases, and detector design considerations including resolution estimates on DIS kinematic variables. A possible road map toward the future MuIC and muon–antimuon colliders is also presented.

Photostimulated desorption performance of the future circular hadron collider beam screen

Synchrotron radiation (SR) originated at superconducting bending magnets is known to be at the origin of several beam detrimental effects related to vacuum instabilities. One of the major challenges in the design of the vacuum beam pipes of high-energy hadron colliders is the SR coping strategy. In the case of the future circular hadron collider (FCC-hh), a Cu-coated beam screen (BS) operating in the range of 40--60 K has been designed with the aim of protecting the superconducting magnet cold bores from direct synchrotron irradiation. In order to experimentally study the FCC-hh BS vacuum and cryogenic performance, two sample prototypes were manufactured and installed in the beam screen test-bench experiment (BESTEX) at the Karlsruhe Research Accelerator (KARA) at the Karlsruhe Institute of Technology (KIT). The emitted SR has a critical energy of 6.2 keV, very similar to the 4.6 keV of FCC-hh. Irradiation at both room (RT) and cryogenic (77 K) temperatures showed a significant reduction of the molecular photostimulated desorption yields ($\ensuremath{\eta}$) of the FCC-hh beam screen compared to those of Cu samples. A first approximation of $\ensuremath{\eta}$ and its evolution with the photon dose accumulated on the FCC-hh BS prototype at 77 K allows to estimate that a machine conditioning period of $\ensuremath{\sim}1.2$ months would be needed to reduce the photostimulated molecular density at the necessary levels to ensure a 100 h beam lifetime at nominal FCC-hh operation.

Investigation of charged Higgs boson in the bottom and top quark decay channel at the FCC-hh

After the recent discovery of a neutral Higgs boson with a mass about 125 GeV, we assess the extend of discovery potential of future circular hadron collider (FCC-hh) for a charged Higgs boson in the bottom and top quark decay channel. The charged Higgs boson can be produced through the pp→h−t+X process with a subsequent decay h−→bt¯ channel. This decay channel is particularly important for studying the charged Higgs boson heavier than the top quark. We consider an extension of the standard model Higgs sector, namely two Higgs doublet model (2HDM), and perform a dedicated signal significance analysis to test this channel for the FCC-hh running at the center of mass energy of 100 TeV and the integrated luminosity of 1 ab−1 (initial), 3 ab−1 (comparison with HL-LHC) and 30 ab−1 (ultimate). We find that an important part of the parameter spaces of two Higgs doublet model is examinable at the FCC-hh.

Beam induced vacuum effects in the future circular hadron collider beam vacuum chamber

EuroCirCol is a conceptual design study of a post-LHC, Future Circular Hadron Collider (FCC-hh) with 50 TeV of beam energy and 100 km long, which aims to expand the current energy and luminosity frontiers. The vacuum chamber of the FCC-hh will have to cope with unprecedented levels of synchrotron radiation power for proton colliders, dealing simultaneously with a tighter magnet aperture. Considering that the high radiation power and photon flux will release larger amounts of gas into the system, the difficulty to meet the vacuum specifications increases substantially compared with the LHC. This paper presents a study on the beam induced vacuum effects for the FCC-hh novel conditions, the different phenomena which, owing to the presence of the beam, have an impact on the accelerator's vacuum level. It is concluded that thanks to the adopted mitigation measures the proposed vacuum system shall be adequate, allowing us to reach $\ensuremath{\le}1\ifmmode\times\else\texttimes\fi{}{10}^{15}\text{ }\text{ }{\mathrm{H}}_{2\text{ }eq}/{\mathrm{m}}^{3}$ with baseline beam parameters within the first months of conditioning.

Design of the future circular hadron collider beam vacuum chamber

The optimized vacuum chamber for a future higher-energy hadron collider minimizes electron cloud build-up, outgassing from synchrotron radiation, and heat leakage to the cold mass of the superconducting magnets, while maximizing pumping efficiency and ensuring mechanical stability during a magnet quench.

Thermodynamic and economic aspects of the Nelium Turbo-Brayton refrigerator development for the FCC-hh

Within the conceptual design study for the Future Circular Hadron Collider (FCC-hh) it was shown, that a large part of the total cryogenic heat load falls into the temperature range between 40 to 60 K. Thus, additional cryogenic refrigerators for this temperature level are specified for each of the 10 foreseen cryoplants. Such a cryogenic system was developed at the TU Dresden and is based on a Brayton cycle working with a neon-helium mixture as refrigerant and using multistage centrifugal compressors. The duty requirements comprise a 6.2 MW total heat load at 40 to 60 K for beam screens and shielding, additional 2.7 MW at 300 to 40 K for the pre-cooling of the helium cycle and a turndown ratio of up to 3.8. The optimisation of the referenced system was performed in order to obtain a high efficiency of the cryogenic cycle and tolerable costs for system components at the same time. An analysis of the mixture composition influence on the components and on the total gas mass was performed. Restrictions for industrially existing hardware were taken into consideration. Updated cycle parameters are subsequently described.

Sensitivity on anomalous neutral triple gauge couplings via ZZ production at FCC-hh

We study the sensitivity of anomalous neutral triple gauge couplings (aNTGC) via pp rightarrow ZZ production in the 4ell channel at 100 TeV center of mass energy of future circular hadron collider, FCC-hh. The analysis including the realistic detector effects is performed in the mode where both Z bosons decay into same-flavor, oppositely charged lepton pairs. The sensitivities to the charge–parity (CP)-conserving couplings C_{{tilde{B}}W} / Lambda ^{4} and CP-violating couplings C_{WW} / Lambda ^{4}, C_{BW} / Lambda ^{4} and C_{BB} / Lambda ^{4} obtained at 95% Confidence Level using the invariant mass distribution of the 4ell system reconstructing the leading and sub-leading Z boson candidates are [-,0.09, ,, +,0.09], [-,0.21, ,, +,0.21], [-,0.26, ,, +,0.26], and [-,0.10, ,, +,0.10] in units of hbox {TeV}^{-4}, respectively.

Commissioning of a beam screen test bench experiment with a future circular hadron collider type synchrotron radiation beam

Coping with synchrotron radiation (SR) that originated at superconducting bending magnets is one of the major challenges in the design of the vacuum beam pipes of hadron colliders. In the case of the Future Circular hadron Collider (FCC-hh), similarly as for the LHC, a beam screen, operating at higher temperatures than the cold mass, has been designed in order to preserve the superconducting magnet cold bores from direct synchrotron irradiation. The quality of the beam screen vacuum can be severely compromised by the absorption of SR into its walls, enhancing the risk for numerous beam detrimental effects to arise. In order to experimentally study such effects and develop strategies for their minimization, a beam screen test bench experiment (BESTEX) has been conceived and installed in the Karlsruhe Research Accelerator storage ring at the Karlsruhe Institute for Technology. The BESTEX has been designed to explore photon stimulated desorption, photon reflectivity, photon heat loads, and photoelectron generation originated on beam screen prototypes under irradiation of the FCC-hh-like SR spectrum. A detailed description of the BESTEX, its commissioning, and its functionality is hereby presented.

Discovery reach for wino and higgsino dark matter with a disappearing track signature at a 100 TeV pp collider

Within the theory of supersymmetry, the lightest neutralino is a dark matter candidate and is often assumed to be the lightest supersymmetric particle (LSP) as well. If the neutral wino or higgsino is dark matter, the upper limit of the LSP mass is determined by the observed relic density of dark matter. If the LSP is a nearly-pure neutral state of the wino or higgsino, the lightest chargino state is expected to have a significant lifetime due to a tiny mass difference between the LSP and the chargino. This article presents discovery potential of the 100 TeV future circular hadron collider (FCC) for the wino and higgsino dark matter using a disappearing-track signature. The search strategy to extend the discovery reach to the thermal limits of wino/higgsino dark matter is discussed with detailed studies on the background rate and the reference design of the FCC-hadron detector under possible running scenarios of the FCC-hadron machine. A proposal of modifying the detector layout and several ideas to improve the sensitivity further are also discussed.

Probing the effects of dimension-eight operators describing anomalous neutral triple gauge boson interactions at FCC-hh

The effects of dimension-eight operators giving rise to anomalous neutral triple gauge boson interactions of Zγγ and ZγZ vertices in pp→l−l+γ and pp→νν¯γ are investigated at 100 TeV center of mass energy of future circular hadron collider (FCC-hh). The transverse momentum of photon, invariant mass of l−l+γ and angular distribution of charged lepton in the rest frame of l−l+ and Missing Energy Transverse (MET) are considered in the analysis. The realistic detector effects are also included with Delphes simulation. Sensitivity limits obtained at 95% C.L. for CB˜W/Λ4 and CBB/Λ4 couplings are [−0.52;0.52]([−0.40;0.40]) TeV−4, [−0.43;0.43]([−0.33;0.33]) TeV−4 in the dilepton+photon channel and [−0.11;0.11]([−0.084;0.084]) TeV−4, [−0.092;0.092]([−0.072;0.072]) TeV−4 in the MET+photon channel with Lint=1 (3) ab−1, respectively.

Modeling of nonlinear effects due to head-on beam-beam interactions

The beam-beam interaction is one of the most severe limitations on the performance of circular colliders, as it is an unavoidable strong nonlinear effect. As one aspires for greater luminosity in future colliders, one will simultaneously achieve stronger beam-beam interactions. We study the limitations caused by strong incoherent head-on beam-beam interactions, using a new code (cabin) that calculates on a graphics processing unit (GPU), allowing for a detailed description of the long-term particle trajectories in 6D phase space. The evolution of the beam emittance and beam intensity has been monitored to study the impact quantitatively, while frequency map analysis has been performed to understand the impact qualitatively. Results from cabin have shown good quantitative agreement with dedicated experiments in the Large Hadron Collider (LHC). For large beam-beam tune shifts, alternatives to the LHC tunes have been found to improve the beam quality. Schemes devised to cancel beam-beam driven resonances, by use of specific intermediate phase advances between the interaction points, work very well with zero crossing angle, and the accuracy required is achievable. Due to lack of symmetry, these schemes have an almost negligible impact with a significant crossing angle. The hourglass effect has been found to reduce the detrimental effects caused by the chromaticity and vice versa. The optimal level of the hourglass effect has been achieved when ${\ensuremath{\beta}}^{*}=1.5{\ensuremath{\sigma}}_{s}$. The ultimate parameters of the Future Circular Hadron Collider (FCC-hh) seem within reach, in absence of residual odd resonances.

Clues on the Majorana scale from scalar resonances at the LHC

In order to address the observation of the neutrino oscillations and the metastability of the Standard Model (SM), we extend the fermion sector with two right-handed (i.e. sterile) neutrinos, and the scalar sector of the SM with a real scalar, the Hill field. The latter takes the role of a Majoron and generates the Majorana masses for the neutrino sector, such that the particle spectrum features two CP-even scalars h1and h2, and also two heavy, mass degenerate neutrinos. When the h1is identified with the scalar resonance at [Formula: see text] 125 GeV and the condition is imposed that the h1self-coupling and its running vanish at the Planck scale, the scalar mixing and the vacuum expectation value of the Hill field are fixed by the h2mass.The h2can be searched for at the LHC, and it has prospects of being discovered for the target integrated luminosities of the HL-LHC and the Future Circular hadron Collider (FCC-hh) when its mass is on the weak scale. The knowledge of the h2mass and its decay properties can yield an insight into its coupling to the heavy neutrinos, and thus also on the heavy neutrino mass scale. This yields an interesting connection between potentially detectable heavy scalars in high-energy proton collisions and the mass scale of the heavy neutrinos that is testable at the LHC and at future colliders.