High-energy Electron-positron Colliders Research Articles

Luminosity and beam-induced background studies for the Cool Copper Collider

A high-energy electron-positron collider has been widely recognized by the particle physics community to be the next crucial step for detailed studies of the Higgs boson and other fundamental particles and processes. Several proposals for such colliders, either linear or circular, are currently under evaluation. Any such collider will be required to reach high lumimosities, in order to collect enough data at a reasonable time scale, while at the same time coping with high rates of background particles produced from beam-beam interactions during the collisions. In this paper, we analyze the luminosity and beam-beam interaction characteristics of the Cool Copper Collider (C3) and perform a comparison with other linear collider proposals. We conclude that C3 can reach the same or higher collision rates as the other proposals, without having to cope with higher beam-induced background fluxes. Thus, C3 emerges as an attractive option for a future electron-positron collider, benefiting from the collective advancements in beam delivery and final focus system technologies developed by other linear collider initiatives. Published by the American Physical Society 2024

Discriminating Majorana and Dirac heavy neutrinos at lepton colliders

In this paper we investigate how well the nature of heavy neutral leptons can be determined at a future lepton collider, after its potential discovery. Considered in a simplified model are prompt decays of the neutrino in the mass range from 100 GeV to 10 TeV. We study event selection and application of multivariate analyses to determine whether such a newly discovered particle is of the Dirac or Majorana nature. Combining lepton charge and kinematic event variables, we find that the nature of a heavy neutrino, whether it is a Dirac or a Majorana particle, can be determined at 95% C.L. almost in the whole discovery range. We will briefly speculate about other than the studied channels and the robustness of this statement in more general models of heavy neutral leptons, particularly on the complementarity of high-energy electron-positron vs. muon colliders on resolving the flavor structure of heavy neutrinos.

Narrow bandwidth, low-emittance positron beams from a laser-wakefield accelerator

The rapid progress that plasma wakefield accelerators are experiencing is now posing the question as to whether they could be included in the design of the next generation of high-energy electron-positron colliders. However, the typical structure of the accelerating wakefields presents challenging complications for positron acceleration. Despite seminal proof-of-principle experiments and theoretical proposals, experimental research in plasma-based acceleration of positrons is currently limited by the scarcity of positron beams suitable to seed a plasma accelerator. Here, we report on the first experimental demonstration of a laser-driven source of ultra-relativistic positrons with sufficient spectral and spatial quality to be injected in a plasma accelerator. Our results indicate, in agreement with numerical simulations, selection and transport of positron beamlets containing Ne+≥105\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_{e+}\\ge 10^5$$\\end{document} positrons in a 5% bandwidth around 600 MeV, with femtosecond-scale duration and micron-scale normalised emittance. Particle-in-cell simulations show that positron beams of this kind can be guided and accelerated in a laser-driven plasma accelerator, with favourable scalings to further increase overall charge and energy using PW-scale lasers. The results presented here demonstrate the possibility of performing experimental studies of positron acceleration in a laser-driven wakefield accelerator.

Heavy neutral leptons at beam dump experiments of future lepton colliders

A new beam dump experiment that utilizes the beam of future high energy electron-positron colliders could be an excellent avenue to search for dark sector particles due to its unprecedented high energy and intensity. We consider heavy neutral leptons (HNLs) as a specific example to demonstrate the sensitivity of searches for dark sector particles at future electron-positron collider beam dump experiments. This includes the study of the reach at the International Linear Collider (ILC), the Cool Copper Collider (C3), and the Compact Linear Collider (CLIC). We comprehensively examine the HNL production and detector acceptance at these electron beam dump experiments. We show that these experiments will probe regions of HNL parameter space, not yet probed by past experiments, as well as by future approved experiments. Our study also motivates a more detailed analysis of heavy meson productions in high-energy electron-nucleon collisions in thick targets.

Beam loss background with magnet errors and beam–beam effect in CEPC

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center-of-mass energy of 240[Formula: see text]GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. During manufacture and installation, magnets are not perfect and with many kinds of errors. Beam–beam interaction in high-energy electron positron collider is the action of external field force, which changes the momentum of each beam bunch. Thus, beam loss background can be affected by the magnet errors and beam–beam effect. In this paper, the beam loss background with magnet errors and beam–beam effect is simulated in CEPC.

Future Circular Collider: Integrated Programme and Feasibility Study

The Future Circular Collider (FCC) Integrated Project foresees, in a first stage, a high-luminosity high-energy electron-positron collider, serving as Higgs, top and electroweak factory, and, in a second stage, an energy frontier hadron collider, with a centre-of-mass energy of at least 100 TeV. This programme well matches the highest priority future requests issued by the 2020 Update of the European Strategy for Particle Physics. In 2021, with the support of the CERN Council, a five-year FCC Feasibility Study was launched. In this article, we present the FCC integrated project and the preparations for the FCC Feasibility Study.

The present and future of four top operators

We study the phenomenology of a strongly-interacting top quark at future hadron and lepton colliders, showing that the characteristic four-top contact operators give rise to the most significant effects. We demonstrate the extraordinary potential of a 100 TeV proton-proton collider to directly test such non-standard interactions in four-top production, a process that we thoroughly analyze in the same-sign dilepton and trilepton channels, and explore in the fully hadronic channel. Furthermore, high-energy electron-positron colliders, such as CLIC or the ILC, are shown to exhibit an indirect yet remarkable sensitivity to four-top operators, since these constitute, via renormalization group evolution, the leading new-physics deformations in top-quark pair production. We investigate the impact of our results on the parameter space of composite Higgs models with a strongly-coupled (right-handed) top quark, finding that four-top probes provide the best sensitivity on the compositeness scale at the future energy frontier. In addition, we investigate mild yet persisting LHC excesses in multilepton plus jets final states, showing that they can be consistently described in the effective field theory of such a new-physics scenario.

Taming of preasymptotic small x evolution within resummation framework

It is well understood that the leading logarithmic approximation for the amplitudes of high energy processes is insufficient and that the next-to-leading logarithmic effects are very large and lead to instability of the solution. The resummation at low x, which includes kinematical constraints and other corrections leads to stable result. Using previously established resummation procedure we study in detail the preasymptotic effects which occur in the solution to the resummed BFKL equation when the energy is not very large. We find that in addition to the well known reduction of the intercept, which governs the energy dependence of the gluon Green’s function, resummation leads to the delay of the onset of its small x growth. Moreover the gluon Green’s function develops a dip or a plateau in wide range of rapidities, which increases for large scales. The preasymptotic region in the gluon Green’s function extends to about 8 units in rapidity for the transverse scales of the order of 30–100 GeV. To visualize the expected behavior of physical processes with two equal hard scales we calculate the cross section of the process gamma ^{*}+gamma ^{*}rightarrow X to be probed at future very high-energy electron-positron colliders. We find that at gamma ^*gamma ^* energies below 100 ; mathrm{{GeV}} the BFKL Pomeron leads to smaller value of the cross section than the Born approximation, and only starts to dominate at energies about 100 ; mathrm{{GeV}}. This pattern is significantly different from the one which we find using LLx approximation. We also analyze the transverse momentum contributions to the cross section for different virtualities of the photons and find that the dominant contributions to the integral over the transverse momenta comes from lower values than the the external scales in the process under consideration.

High-energy high-luminosity e+e− collider using energy-recovery linacs

In this letter we present a novel approach for a high-energy high-luminosity electron-positron collider. Present designs for high-energy electron-positron colliders are either based on two storage rings with 100 km circumference with a maximum CM energy of 365 GeV or two large linear accelerators with a high energy reach but lower luminosity, especially at the lower initial CM energies. A shortcoming of the collider based on storage rings is the high electric power consumption required to compensate for the beam energy losses from the 100 MW of synchrotron radiation power [1]. We propose to use an Energy Recovery Linac (ERL) located in the same-size 100 km tunnel to mitigate this drawback. We show in this letter that using an ERL would allow large reduction of the beam energy losses while providing higher luminosity in this high-energy collider operating at or above 140 GeV center-of-mass energy. Furthermore, our approach allows for extending the CM energy to 500 GeV, which would enable double-Higgs production, and even to 600 GeV for tt‾H production.

Model-independent sensibility studies for the anomalous dipole moments of theντat the CLIC basede+e−andγe−colliders

To improve the theoretical prediction of the anomalous dipole moments of the $\tau$-neutrino, we have carried out a study through the process $\gamma e^- \to \tau \bar\nu_\tau \nu_e$, which represents an excellent and useful option in determination of these anomalous parameters. To study the potential of the process $\gamma e^- \to \tau \bar\nu_\tau \nu_e$, we apply a future high-energy and high-luminosity linear electron-positron collider, such as the CLIC, with $\sqrt{s}=380, 1500, 3000\hspace{0.8mm}GeV$ and ${\cal L}=10, 50, 100, 200, 500, 1000, 1500, 2000, 3000\hspace{0.8mm}fb^{-1}$, and we consider systematic uncertainties of $\delta_{sys}=0, 5, 10\%$. With these elements, we present a comprehensive and detailed sensitivity study on the total cross-section of the process $\gamma e^- \to \tau \bar\nu_\tau \nu_e$, as well as on the dipole moments $\mu_{\nu_\tau}$ and $d_{\nu_\tau}$ at the $95\%$ C.L., showing the feasibility of such process at the CLIC at the $\gamma e^-$ mode with unpolarized and polarized electron beams.

Hadronic vs. electromagnetic pulse shape discrimination in CsI(Tl) for high energy physics experiments

Pulse shape discrimination using CsI(Tl) scintillators to perform neutral hadron particle identification is explored with emphasis towards application at high energy electron-positron collider experiments. Through the analysis of the pulse shape differences between scintillation pulses from photon and hadronic energy deposits using neutron and proton data collected at TRIUMF, it is shown that the pulse shape variations observed for hadrons can be modelled using a third scintillation component for CsI(Tl), in addition to the standard fast and slow components. Techniques for computing the hadronic pulse amplitudes and shape variations are developed and it is shown that the intensity of the additional scintillation component can be computed from the ionization energy loss of the interacting particles. These pulse modelling and simulation methods are integrated with GEANT4 simulation libraries and the predicted pulse shape for CsI(Tl) crystals in a 5 × 5 array of 5 × 5 × 30 cm3 crystals is studied for hadronic showers from 0.5 and 1 GeV/c KL0 and neutron particles. Using a crystal level and cluster level approach for photon vs. hadron cluster separation we demonstrate proof-of-concept for neutral hadron detection using CsI(Tl) pulse shape discrimination in high energy electron-positron collider experiments.

Direct searches of Type-III seesaw triplet fermions at high energy e^+e^- collider

The signatures of heavy fermionic isotriplets (Sigma ) are probed through their direct production and subsequent decay at high energy electron–positron colliders. Unlike the case of LHC, the production process has strong dependence on the mixing of Sigma with electron (V_{e}), making the leptonic collider unique to fingerprint the presence of such mixing. We establish that pair production considered at sqrt{s}=2 TeV can be employed to study both the cases of V_e=0 and of V_ene 0 with sim 100 fb^{-1} luminosity, while the single production can probe the latter case with a few inverse femto barn luminosity at sqrt{s}=1 TeV. Exploring the mass reach, both the single and pair productions are capable of probing Sigma of mass close to the kinematic limits through selected channels. Investigating simultaneous limits on the M_Sigma -V_e parameter space, we identify suitable final states and their 3sigma reach on V_e and M_Sigma at 300 (100) fb^{-1} luminosity in the case of pair (single) Sigma production.

Design and standalone characterisation of a capacitively coupled HV-CMOS sensor chip for the CLIC vertex detector

The concept of capacitive coupling between sensors and readout chips is under study for the vertex detector at the proposed high-energy CLIC electron positron collider. The CLICpix Capacitively Coupled Pixel Detector (C3PD) is an active High-Voltage CMOS sensor, designed to be capacitively coupled to the CLICpix2 readout chip. The chip is implemented in a commercial 180 nm HV-CMOS process and contains a matrix of 128×128 square pixels with 25μm pitch. First prototypes have been produced with a standard resistivity of ∼20 Ωcm for the substrate and tested in standalone mode. The results show a rise time of ∼20 ns, charge gain of 190 mV/ke− and ∼40 e− RMS noise for a power consumption of 4.8μW/pixel. The main design aspects, as well as standalone measurement results, are presented.

Overview of the CLIC detector and its physics potential

The CLIC detector and physics study (CLICdp) is an international collaboration that investigates the physics potential of the Compact Linear Collider (CLIC). CLIC is a high-energy electron-positron collider under development, aiming for centre-of-mass energies from a few hundred GeV to 3 TeV. In addition to physics studies based on full Monte Carlo simulations of signal and background processes, CLICdp performs cuttingedge hardware R&D. In this contribution CLICdp will present recent results from physics prospect studies, emphasising Higgs studies. Additionally the new CLIC detector model and the recently updated CLIC baseline staging scenario will be presented.

Bounds on the Electromagnetic Dipole Moments through the Single Top Production at the CLIC

We obtain bounds on the anomalous magnetic and electric dipole moments of thet-quark from a future high-energy and high-luminosity linear electron positron collider, as the CLIC, with polarized and unpolarized electron beams which are powerful tools for determining new physics. We consider the processesγe-→t¯bνe(γis the Compton backscattering photon) ande+e-→e-γ⁎e+→t¯bνee+(γ⁎is the Weizsacker-Williams photon) as they are one of the most important sources of single top quark production. For systematic uncertainties ofδsys=0% (5%),b-tagging efficiency=0.8, center-of-mass energy ofs=3 TeV, and integrated luminosity ofL=2ab-1the futuree+e-collider may put bounds on the electromagnetic dipole momentsa^Vanda^Aof the top quark of the order ofO(10-2–10-1)at the2σ (3σ)level, which are competitive with those recently reported in previous studies at hadron colliders and the ILC.

Study of single top production at high energy electron positron colliders

The effect of single top production on the study of top quark pair production in future high energy electron–positron colliders is evaluated. The rate of the single top quark production process is sizeable throughout a large range of center-of-mass energies and the final state cannot easily be distinguished from the dominant pair production process. We discuss the impact on the top quark mass extraction from a scan through the pair production threshold and the determination of top quark form factors in the continuum. These results advocate for the exploration of the inclusive $$e^+e^-\rightarrow W^+bW^-\bar{b}$$ process, that includes both top quark pair and single top quark production.

能量前沿正负电子对撞机的研究进展

In 2012, the discovery of a particle matching the Higgs boson at CERNs Large Hadron Collider became a very important milestone in high energy physics history. Research and development towards future high-energy electron-positron colliders is actively explored around the world with the purpose of measuring precisely the properties of this unconfirmed Higgs boson and to discover new physics beyond the Standard Model of particle physics. In this paper, we briefly review the history from the past half century of electron-positron colliders at the high-energy frontier, including the first electron-positron collider AdA, as well as the colliders based AdA, such as ACO, VEPP-II, ADONE, and the later colliders SPEAR, DORIS, CESR, TRISTAN etc., and the last and largest electron-positron collider in the world up to now, LEP. Then, the paper reports several proposals for future electron-positron colliders from around the world such as ILC, CLIC TLEP and so on, in particular Chinas entry, the Circular Electron-Positron Collider.

Z′Resonance and AssociatedZhProduction at Future Higgs Boson Factory: ILC and CLIC

We study the prospects of theB-Lmodel with an additionalZ′boson to be a Higgs boson factory at high-energy and high-luminosity linear electron positron colliders, such as the ILC and CLIC, through the Higgs-strahlung processe+e-→(Z,Z′)→Zh, including both the resonant and the nonresonant effects. We evaluate the total cross section ofZhand we calculate the total number of events for integrated luminosities of 500–2000 fb−1and center of mass energies between 500 and 3000 GeV. We find that the total number of expectedZhevents can reach 106, which is a very optimistic scenario and it would be possible to perform precision measurements for bothZ′and Higgs boson in future high-energye+e-colliders experiments.

Laser-driven generation of high-quality ultra-relativistic positron beams

An ultra-relativistic electron beam propagating through a high-Z solid triggers an electromagnetic cascade, whereby a large number of high-energy photons and electron–positron pairs are produced mainly via the bremsstrahlung and Bethe–Heitler processes, respectively. These mechanisms are routinely used to generate positron beams in conventional accelerators such as the electron–positron collider (LEP). Here we show that the application of similar physical mechanisms to a laser-driven electron source allows for the generation of high-quality positron beams in a much more compact and cheaper configuration. We anticipate that the application of these results to the next generation of lasers might open the pathway for the realization of an all-optical high-energy electron–positron collider.

Strong Higgs interactions at a linear collider

We study the impact of Higgs precision measurements at a high-energy and high-luminosity linear electron positron collider, such as CLIC or the ILC, on the parameter space of a strongly interacting Higgs boson. Some combination of anomalous couplings are already tightly constrained by current fits to electroweak observables. However, even small deviations in the cross sections of single and double Higgs production, or the mere detection of a triple Higgs final state, can help establish whether it is a composite state and whether or not it emerges as a pseudo-Nambu-Goldstone boson from an underlying broken symmetry. We obtain an estimate of the ILC and CLIC sensitivities on the anomalous Higgs couplings from a study of WW scattering and hh production which can be translated into a sensitivity on the compositeness scale 4\pi f, or equivalently on the degree of compositeness \xi=v^2/f^2. We summarize the current experimental constraints, from electroweak data and direct resonance searches, and the expected reach of the LHC and CLIC on \xi and on the scale of the new resonances.