Electron-positron Linear Collider Research Articles

Total cross section of the process e++e−→Σ0+Σ¯0 in the vicinity of charmonium ψ(3770) including the D -meson loop and three-gluon contributions

For the study of the structure of baryons it is necessary to investigate the production of a baryon pair in e+e− annihilation. The baryon-antibaryon pair production at the electron-positron linear collider makes it possible to investigate in detail the basic structure of the Standard Model. The creation of baryon-antibaryon pairs in electron-positron annihilation provides an increasingly powerful tool at higher c.m. energies. We present phenomenological results for Σ0Σ¯0 production in e+e− interaction at the BESIII and Colliders. In the present work, we investigate a hyperon pair produced in the reaction e+e−→Σ0Σ¯0. We calculate the total cross section of the process e+e−→Σ0Σ¯0 taking into account the contributions of the D-meson loop and three gluon loops as well as the interference of all diagrams to the Born approximation. For these contributions large relative phases are generated with respect to the pure electromagnetic mechanism. For the large momentum transferred region we obtain as a byproduct a fit of the electromagnetic form factor of the Σ hyperon. Published by the American Physical Society 2024

Design Criteria for High-Gradient Radio-Frequency Linacs

This article will review methods used at the SLAC National Accelerator Laboratory and other world accelerator laboratories to design high-gradient normal conducting accelerating structures. A quest for compact radio-frequency linacs fueled decades of studies toward a higher accelerating gradient. A major phenomena limiting the increase of the gradient is vacuum radio-frequency breakdown; therefore, this paper will address the breakdown physics and discuss approaches that reduce the breakdown probability. This discussion will cover both the electrical design and fabrication technology of the accelerating structures to achieve practical operating accelerating gradients in excess of 100 MV/m. Most of the data described here were obtained during the development of 11 GHz linacs for electron–positron linear colliders, so extrapolation of the results to other frequencies should be performed cautiously.

Damping-ring-free electron injector proposal for future linear colliders

The current designs of future electron-positron linear colliders incorporate large and complex damping rings to produce asymmetric beams for beamstrahlung suppression. Here, we present the design of an electron injector capable of delivering flat electron beams with phase-space partition comparable to the electron-beam parameters produced downstream of the damping ring in the proposed International Linear Collider (ILC) design. Our design does not employ a damping ring but is instead based on cross-plane phase-space manipulation techniques. The performance of the proposed configuration, its sensitivity to jitter along with its impact on spin-polarization are investigated. The proposed paradigm could be adapted to other linear collider concepts under consideration and offers a path toward significant cost and complexity reduction.

A design of ILC E-driven positron source

ILC is an electron-positron linear collider based on Superconducting linear accelerator. Linear collider is the only solution to realize high energy electron-positron collision beyond the limit of synchrotron radiation energy loss by ring colliders. Beam current of injector of linear colliders is much larger than that of ring colliders because the beam is not reusable. Providing an enough amount of particles, especially positron is a technical issue. In this article, we present a design of electron driven positron source for ILC. After optimizations, the system design is established with an enough technical margin, e.g. avoiding potential damage on the production target.

Production of Exotic Particles in Electron-Positron Collisions

In this work, the results for cross sections of central exclusive exotic particles production in future linear electron-positron colliders are presented. These results show that the central production of charginos, dilatons, radions, axions and technipions can be measurable for the center-of-mass energies for these colliders. The results presented here, when compared with the production in hadronic colliders, have a smaller cross section, but with the advantage that the electron-positron collision does not have remnants coming from hadronic dissociation.

Kinematic corrections and reconstruction methods for neutral Higgs boson decay to bb¯ in 2HDM type I at future lepton colliders

In this paper, an approach for neutral Higgs bosons search is described based on 2HDM type-I at electron-positron linear colliders operating at $ \sqrt{s}=1$ TeV. The beam is assumed to be unpolarized and fast detector simulation is included. The signal process produces a fully hadronic final state through $ e^{+}e^{-}\rightarrow AH\rightarrow b\bar{b}b\bar{b} $ where both CP-even and CP-odd Higgs bosons ($H$ and $A$) are assumed to decay to a pair of $b$-jets. Several benchmark scenarios are introduced as the baseline for the analysis taking $ m_{H/A}$ in the range 150--300 GeV. In order to avoid Higgs boson conversion $A \to ZH$, Higgs boson masses are chosen with $m_A-m_H < m_Z$. It is shown that with a proper kinematic correction applied on final state $b$-jet four momenta, true combinations of $b$-jets can be found for simultaneous reconstruction of both Higgs bosons through $b\bar{b}$ invariant mass calculation. Results show that observable signals can be achieved with statistical significance exceeding $5\sigma$ well before the target integrated luminosity of 8 $ab^{-1}$.

Light-by-light scattering and spacetime noncommutativity

The aim of this article is to explore a potential usability of a photon-photon self-interaction from the noncommutative quantum electrodynamics (NCQED) in the case of light-by-light scattering ($\gamma\gamma\to\gamma\gamma$) in ultraperipheral Pb+Pb collisions, a reaction measured recently by ATLAS and planned for future experiments in hadron-hadron colliders. We compute the total cross section from both, the full one-loop standard model (SM) and the tree-level NCQED amplitudes, in the equivalent photon approximation with impact parameters, for various noncommutative scales, $\rm\Lambda_{NC}$, and incoming nuclear spin-energy combinations. We find that NCQED contribution to the cross section has considerable increase at diphoton invariant mass range higher than $\rm\Lambda_{NC}$, while the SM contribution is strongly suppressed in such region. Our results show that the current ATLAS $\rm\sqrt{s_{NN}} = 5.02$ TeV experiment can only probe $\rm\Lambda_{NC}<100$ GeV region. On the other hand, future hadron-hadron collider proposals could have the potential to extend to $\rm\Lambda_{NC}\lesssim 300$ GeV region, making the performance of $\rm Pb+Pb(\gamma\gamma)\to Pb+Pb\gamma\gamma$ scattering on testing space-time noncommutativity close to that of the previously proposed photon-photon mode of linear electron-positron collider.

Particle physics at accelerators in the United States and Asia

Particle physics experiments in the United States and Asia have greatly contributed to the understanding of elementary particles and their interactions. With the recent discovery of the Higgs boson at CERN, interest in the development of next-generation colliders has been rekindled. A linear electron-positron collider in Japan and a circular collider in China have been proposed for precision studies of the Higgs boson. In addition to the Higgs programme, new accelerator-based long-baseline neutrino mega-facilities are being built in the United States and Japan. Here, we outline the present status of key particle physics programmes at accelerators and future plans in the United States and Asia that largely complement approaches being explored in the European Strategy for Particle Physics Update. We encourage the pursuit of this global approach, reaching beyond regional boundaries for optimized development and operations of major accelerator facilities worldwide, to ensure active and productive future of the field.

QED and electroweak radiative corrections to polarized Bhabha scattering

Complete one-loop electroweak radiative corrections to polarized Bhabha scattering are presented. Numerical results are shown for the conditions of future circular and linear electron-positron colliders with polarized beams. A new Monte Carlo event generator for simulation of Bhabha scattering is created. Higher order QED collinear radiation factors are evaluated in the next-to-leading logarithmic approximation.

Novel laser-plasma TeV electron-positron linear colliders

TeV center-of-mass energy electron-positron linear colliders comprising seamlessly staged capillary laser-plasma accelerators are presented. A moderate intensity laser pulse coupled with the single electromagnetic hybrid mode in a gas-filled capillary can generate plasma waves in the linear regime, where laser wakefields can accelerate equally focused electron and positron beams. In multiple stage capillary accelerators, a particle beam with respect to the laser wakefield can undergo consecutive acceleration up to TeV energies, associated with continuous transverse focusing in a beam size down to a nanometer level, being capable of a promising electron-positron linear collider with very high luminosities of the order of 10[Formula: see text] cm[Formula: see text]s[Formula: see text]. The transverse and longitudinal beam dynamics of beam particles in plasma wakefields with the effects of radiation reaction and multiple Coulomb scattering are investigated numerically to estimate the luminosities in beam-beam collisions with the effects of beamstrahlung radiation and bunch disruption.

Top-quark physics at the CLIC electron-positron linear collider

The Compact Linear Collider (CLIC) is a proposed future high-luminosity linear electron-positron collider operating at three energy stages, with nominal centre-of-mass energies sqrt{s} = 380 GeV, 1.5 TeV, and 3 TeV. Its aim is to explore the energy frontier, providing sensitivity to physics beyond the Standard Model (BSM) and precision measurements of Standard Model processes with an emphasis on Higgs boson and top-quark physics. The opportunities for top-quark physics at CLIC are discussed in this paper. The initial stage of operation focuses on top-quark pair production measurements, as well as the search for rare flavour-changing neutral current (FCNC) top-quark decays. It also includes a top-quark pair production threshold scan around 350 GeV which provides a precise measurement of the top-quark mass in a well-defined theoretical framework. At the higher-energy stages, studies are made of top-quark pairs produced in association with other particles. A study of t̄tH production including the extraction of the top Yukawa coupling is presented as well as a study of vector boson fusion (VBF) production, which gives direct access to high-energy electroweak interactions. Operation above 1 TeV leads to more highly collimated jet environments where dedicated methods are used to analyse the jet constituents. These techniques enable studies of the top-quark pair production, and hence the sensitivity to BSM physics, to be extended to higher energies. This paper also includes phenomenological interpretations that may be performed using the results from the extensive top-quark physics programme at CLIC.

Acid-Free Electropolishing of Srf Nb Cavities

The International Linear Collider (ILC) is a 200–500 GeV center-of-mass linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency accelerating technology.[1] The ILC will be used to gain a deeper understanding of the forces of energy and matter by colliding beams of electrons and positrons at nearly the speed of light. To achieve this goal ~16,000 RF superconducting cavities operating within two linear accelerators at near absolute zero are needed.[2] These SRF cavities are fabricated from pure Nb, which has an extremely low surface resistance at 2 Kelvin. To take full advantage of the Nb superconducting properties, the inner surface must be polished to a microscale roughness, and cleaned to be free of impurities that could degrade performance. The DOE seeks commercially viable, fabrication technologies for SRF cavities, specifically new or improved electropolishing technologies that do not use hydrofluoric acid. Current methods use high viscosity electrolytes containing hydrofluoric acid, which is not conducive to low-cost, high volume manufacturing and is potentially harmful to workers. Faraday is developing an electropolishing process for niobium SRF cavities, based on a new and evolving paradigm of non-viscous salt solution processing, enabled by a pulse reverse electric field as high-throughput vertical Acid-Free Final Electropolishing. The use of a low viscosity, near-neutral aqueous salt-based electrolyte enables a vertical cavity orientation, with no required rotation, which is conducive to high throughput manufacturing and industrialization. Furthermore, the use of this electrolyte combined with the pulse reverse or bipolar electric field changes the electropolishing mechanism by which material is removed and the surface profile reduced. Based on our limited understanding to date; [3] we have speculated that the process works via oxide film formation controlled during a designed anodic pulse, followed by an off time to remove heat and waste byproducts, followed by a cathodic pulse that removes the oxide film from the surface. This cycle is repeated many times per second, effectively removing niobium. The waveform design is such that the niobium is preferentially removed from the peaks on the surface, thus smoothing the surface. In addition, we will also discuss recent results from our development of high-throughput vertical acid-free final electropolishing process for SRF cavities and button cell cavity studies. The button cell cavity was designed and built by Cornell for their own cavity finishing process optimization using the conventional sulfuric acid HF approach. This tool enables rapid analysis of the effect of the electrofinishing applied parameter on the finish produced as a function of anode to cathode gap and active area ratio position of the button, orientation, gravity, electrofinishing conditions, and flow rate. Acknowledgements: Funding for this work is gratefully acknowledged from DOE SBIR Grant Number DE-SC0011235. [1] http://home.web.cern.ch/about/updates/2013/06/international-linear-collider-ready-construction[2] http://www.linearcollider.org/ILC/What-is-the-ILC/The-project[3] M. Inman et al “Electropolishing of Passive Materials in HF-Free Low Viscosity Aqueous Electrolytes, J. Electrochem. Soc., 160 (9) E94-E98 (2013).

Future Prospects of Gamma–Gamma Collider

Gamma–gamma colliders based on backward Compton scattering have been discussed mainly as an option for high energy electron–positron linear colliders, aiming to play a complementary role in energy frontier physics. The flexibility of gamma-ray beam by the Compton scheme, however, allows us to apply them to physics in a wide energy range, from MeV to TeV. In this paper, we review the future prospects of gamma–gamma colliders including recent discussions about Higgs boson factories and mid- and low-energy colliders as well as the option for electron–positron linear colliders.

Plasma wakefield linear colliders-opportunities and challenges.

A linear electron-positron collider operating at TeV-scale energies will provide high precision measurements and allow, for example, precision studies of the Higgs boson as well as searches for physics beyond the standard model. A future linear collider should produce collisions at high energy, with high luminosity and with a good wall plug to beam power transfer efficiency. The luminosity per power consumed is a key metric that can be used to compare linear collider concepts. The plasma wakefield accelerator has demonstrated high-gradient, high-efficiency acceleration of an electron beam and is therefore a promising technology for a future linear collider. We will go through the opportunities of using plasma wakefield acceleration technology for a collider, as well as a few of the collider-specific challenges that must be addressed in order for a high-energy, high luminosity-per-power plasma wakefield collider to become a reality. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Bounds on dipole moments of tau-neutrino from single photon searches in SU(4)L × U(1)X model at CLIC and ILC energies

We investigate the dipole moments of the tau-neutrino at high-energy and high luminosity at linear electron–positron colliders, such as CLIC or ILC through the analysis of the reaction [Formula: see text] in the framework of the [Formula: see text] model. The limits on dipole moment were obtained for integrated luminosity of [Formula: see text] and mass ranging from 0.25 to 1.0 TeV. The estimated limits for the tau-neutrino magnetic and electric dipole moments at 95% of confidence level are [Formula: see text] and [Formula: see text] improved by 2–3 orders of magnitude compared to L3 and complement previous studies on the dipole moments.

Theory Challenges at Future Lepton Colliders

High energy, high luminosity, future lepton colliders, circular or linear, may possibly give us hint about fundamental laws of Nature governing at very short distances and very short time intervals, the same which have brought our Universe to live. Currently considered projects are on one hand linear electron-positron colliders, which offer higher energy and lower beam intensities and on the other hand circular electron-positron colliders, limited in energy but offering tremendous interaction rates. On the far future horizon, muon circular colliders are the only viable projects which can explore $>10$TeV teritory of the lepton colliders. Experiments in all these future colliders will require theoretical calculations, mainly of Standard Model processes (including QED), at the precision level one or even two orders better than available today. After briefly characterization of theory puzzles in the fundamental interactions we shall overview main challenges in the precision calculations of the Standard Model effects, which have to be removed from data, in order to reveal traces of new unexpected phenomena.

A silicon-tungsten electromagnetic calorimeter with integrated electronics for the International Linear Collider

We present an update of the development of an electromagnetic calorimeter for the Silicon Detector concept for a future linear electron-positron collider. Mechanical progress for a full barrel calorimeter that provides a more complete basis for simulation is discussed. Crosstalk problems in the first version of the sensor were found in a first testbeam study, and a second version of the sensor is now beginning testing.

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.

Fluid Flow and Current Distribution during Pulse-Reverse Electropolishing of Niobium Superconducting RF Cavities

The International Linear Collider (ILC) is a 200–500 GeV center-of-mass linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency accelerating technology. This installation will require ~16,000 RF superconducting cavities operating within two linear accelerators at near absolute zero [[1]]. These SRF cavities are fabricated from pure Nb; to take full advantage of the Nb superconducting properties, the inner surface must be polished to a microscale roughness, and cleaned to be free of impurities that could degrade performance. Current methods use high viscosity electrolytes containing hydrofluoric acid, which is not conducive to low-cost, high volume manufacturing and is potentially harmful to workers. Faraday is developing an electropolishing process for niobium SRF cavities, based on a new and evolving paradigm of non-viscous dilute acid processing, enabled by a pulse-reverse electric field. Based on our understanding to date [[2]], we have speculated that the process works via oxide film formation controlled during a designed anodic pulse, followed by an off-time to remove heat and waste byproducts, followed by a cathodic pulse that removes the oxide film from the surface. This cycle is repeated many times per second, effectively removing niobium. The waveform design is such that the niobium is preferentially removed from the peaks on the surface, thus smoothing the surface. This talk will describe two recent efforts undertaken to improve understanding of various factors influencing the uniformity and speed of pulse-reverse electropolishing of niobium SRF cavities. The first is a flow study performed in a transparent plastic model of a single-cell (single-bell) cavity (Figure 1, left), to examine the flow dynamics in the absence and presence of an axisymmetric baffle fixed to the rod counter-electrode within the cavity bell. High-speed photography clearly shows the presence of a slow-moving eddy in the equatorial region of the bell (Figure 1, right), which is appreciably reduced in size when the baffle is present. Furthermore, rapid clearance of electrolysis gases and niobium oxide precipitates from the bell is expected to be strongly dependent on a proper configuration of flow throughout the bell. The second effort to be discussed comprises multiphysics modeling of the actual distribution of material removal in the EP process, as a function of position within the cavity. Modeling of EP of passive materials is complex, as numerous coupled phenomena must be accounted for, including: primary, secondary and tertiary current distributions; multi-phase effects, including fluid flow; and oxide formation/removal at the working surface. The strongest effects appear to be the primary and secondary current distributions, along with the surface oxide dynamics, inclusion of these physics (or semi-empirical approximations thereof) provides a significantly improved match between the model to the experimentally observed distribution of material removal, as compared to simulations incorporating only the primary current distribution. Figure 1 Caption (Left) Photograph of the transparent SRF cavity model, showing flow direction and early dye injection streaming pattern. (Right) High-speed photograph with annotations for bypass and eddy flows observed in a representative flow study test. References [[1]] http://www.linearcollider.org/ILC/What-is-the-ILC/The-project [[2]] M. Inman et al “Electropolishing of Passive Materials in HF-Free Low Viscosity Aqueous Electrolytes, J. Electrochem. Soc., 160 (9) E94-E98 (2013). Figure 1

Mechanism of vacuum breakdown in radio-frequency accelerating structures

It has been investigated whether explosive electron emission may be the initiating mechanism of vacuum breakdown in the accelerating structures of TeV linear electron-positron colliders (Compact Linear Collider). The physical processes involved in a dc vacuum breakdown have been considered, and the relationship between the voltage applied to the diode and the time delay to breakdown has been found. Based on the results obtained, the development of a vacuum breakdown in an rf electric field has been analyzed and the main parameters responsible for the initiation of explosive electron emission have been estimated. The formation of craters on the cathode surface during explosive electron emission has been numerically simulated, and the simulation results are discussed.