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Leading-order Feynman diagrams of the highest cross section Higgs production processes at CLIC: Higgsstrahlung (left) and WW-fusion (right).
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![Figure 3: Schematic layout of the CLIC accelerator [9].](publication/343743281/figure/fig2/AS:926247790080000@1597846090025/Schematic-layout-of-the-CLIC-accelerator-9_Q320.jpg)
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Context 1
... processes dominate the Higgs boson production at e + e − collisions, see Fig. 11. For centre-of-mass energies up to about 450 GeV, the Higgs-strahlung process, Higgs boson production together with Z boson, dominates, see Fig. 5. Measurement of the Higgs boson production in the WW-fusion process becomes increasingly important at higher energy stages, however already at the initial ILC and CLIC stages it is helpful ...
Citations
... In the same way that LEP and SLAC were important to test various SM predictions, the CLIC hopes to collect more stringent electroweak precision measurements and signals of new physics for a period of 27 years in three different but complementary stages [75]. Moreover, based on a novel acceleration system, CLIC plans to progressively reach energies of up to √ s = 3 TeV and an integrated luminosity of 5 ab −1 [76][77][78][79] in a sequence of stages. For the first stage of the CLIC operation, beams are expected to be delivered at an energy of √ s = 380 GeV and a luminosity of 1 ab −1 . ...
We derive the discovery potential of a leptophilic $$Z^\prime $$ Z ′ , and a $$Z^\prime $$ Z ′ rising from a $$SU(3)_C \times SU(3)_L \times U(1)_N$$ S U ( 3 ) C × S U ( 3 ) L × U ( 1 ) N symmetry at the Compact Linear Collider (CLIC), which is planned to host $$e^+e^-$$ e + e - collisions with 3 TeV center-of-mass energy. We perform an optimized selection cut strategy on the transverse momentum, pseudorapidity, and invariant mass of the dileptons in order to enhance the collider sensitivity. We find that CLIC can potentially reach a $$5\sigma $$ 5 σ signal of a $$1-5$$ 1 - 5 TeV leptophilic $$Z^\prime $$ Z ′ with less than 1 fb $$^{-1}$$ - 1 of integrated luminosity in the most favorable cases. As for the $$Z^\prime $$ Z ′ belonging to a 3-3-1 symmetry, CLIC will offer a complementary probe with the potential to impose $$M_{Z^\prime } > 3$$ M Z ′ > 3 TeV with $${\mathcal {L}}=2$$ L = 2 fb $$^{-1}$$ - 1 .
... In the same way that LEP and SLAC were important to test various SM predictions, the CLIC hopes to collect more stringent electroweak precision measurements and signals of new physics for a period of 27 years in three different but complementary stages [69]. Moreover, based on a novel acceleration system, CLIC plans to progressively reach energies of up to √ s = 3 TeV and an integrated luminosity of 5 ab −1 [70][71][72][73] in a sequence of stages. For the first stage of the CLIC operation, beams are expected to be delivered at an energy of √ s = 380 GeV and a luminosity of 1 ab −1 . ...
We derive the discovery potential of a leptophilic Z', and a Z' rising from a $SU(3) \times SU(3)_L \times U(1)_N$ symmetry at the Compact Linear Collider (CLIC), which is planned to host $e^+e^-$ collisions with 3 TeV center-of-mass energy. We perform an optimized selection cut strategy on the transverse momentum, pseudorapidity, and invariant mass of the dileptons in order to enhance the collider sensitivity. We find that CLIC can potentially reach a $5\sigma$ signal of a $1-3$~TeV leptophilic Z' with less than $1fb^{-1}$ of integrated luminosity. As for the Z' belonging to a 3-3-1 symmetry, CLIC will offer a complementary probe with the potential to impose $M_{Z^\prime} > 3$~TeV with $\mathcal{L}=2fb^{-1}$.
... We now discuss the collider analysis that helps us in extracting the signal from background processes at future linear e + e − colliders [56][57][58]. The single-Higgs production mechanisms we study are Z + − h, with = {e, µ, τ }, and ZBF, targeting a semi-inclusive search of those decays of the Higgs boson that do not yield final-state charged leptons 3 to avoid redundancies in the reconstruction of the two-lepton system. ...
A bstract
We study standard electroweak/Higgs processes at the high-energy lepton colliders ILC and CLIC. We identify a subset of three operators in the SMEFT that give leading contributions to these processes at high energies. We then perform a ‘high-energy fit’ including these operators. Our final bounds surpass existing LEP bounds and HL-LHC projections by orders of magnitude. Furthermore, we find that these colliders can probe scales up to tens of TeV, corresponding to the highest scales explored in electroweak/Higgs physics.
... The cross section is then given by (38), (43), and (A7). The first two energy values are relevant in the context of existing LEP data [52,53], whereas the last two are important for future e − e þ colliders, such as the ILC [42][43][44][45]54]. The following cuts were applied: E γ > 5 GeV and j cos θ γ j < 0.96 [52,53]. ...
... We conclude, therefore, that a sensible lower limit on ffiffiffi β p could be placed if future e − e þ colliders would include measuring this process in their research programs. Let us take the ILC as an example, which targets a total integrated luminosity of 14 ab −1 over its full operation time [54]. For the sake of clarity, let us focus on the initial stage with ffiffi ffi s p ¼ 250 GeV, where an integrated luminosity of ∼500 fb −1 is planned to be attained in the first five years. ...
In this work, we perform a nonlinear extension of the U(1)Y sector of the Standard Model leading to novel quartic effective interactions between the neutral gauge bosons. We study the induced effects through high-energy processes resulting in three photons, namely, Z-boson decay and electron-positron annihilation. Available experimental data on these processes do not yield viable lower bounds on the mass parameter β, but we estimate that the range β≲mZ could be reliably excluded with better statistics in future e−e+ colliders. We also discuss neutral gauge-boson scatterings, contextualizing our findings with recent results on anomalous quartic gauge couplings.
... We now discuss the collider analysis that helps us in extracting the signal from background processes at future linear e + e − colliders [55][56][57]. The single-Higgs production mechanisms we study are Z ( + − ) h, with = {e, µ, τ }, and ZBF, targeting a semi-inclusive search of those decays of the Higgs boson that do not yield final-state charged leptons 3 to avoid redundancies in the reconstruction of the two-lepton system. ...
We study standard electroweak/Higgs processes at the high-energy lepton colliders ILC and CLIC. We identify a subset of three operators in the SMEFT that give leading contributions to these processes at high energies. We then perform a `high-energy fit' including these operators. Our final bounds surpass existing LEP bounds and HL-LHC projections by orders of magnitude. Furthermore, we find that these colliders can probe scales up to tens of TeV, corresponding to the highest scales explored in electroweak/Higgs physics.
... The main interest of this article is investigation of the CP violation in the electron-positron annihilation into a pair of top quarks decaying into W bosons and bottom quarks. Such process is planned to be explored at future electron-positron colliders like International Linear Collider (ILC) [1][2][3] and Compact Linear Collider (CLIC) [4][5][6][7][8]. The ILC will start at the center-of-mass (CM) energy of 250 GeV followed by 500 GeV upgrade [7,9]. ...
... Such process is planned to be explored at future electron-positron colliders like International Linear Collider (ILC) [1][2][3] and Compact Linear Collider (CLIC) [4][5][6][7][8]. The ILC will start at the center-of-mass (CM) energy of 250 GeV followed by 500 GeV upgrade [7,9]. The CLIC promises to be a good candidate for production of the on-mass-shell top quark and studying its properties. ...
... The CLIC promises to be a good candidate for production of the on-mass-shell top quark and studying its properties. At the first construction stage of CLIC, the CM energy is planned to be 380 GeV with expected integrated luminosity of 1 ab −1 , which will include 100 fb −1 collected near the tt production threshold [6,7,10,11]. One can also mention the proposed e + e − Future Circular Collider FCC-ee [12,13], which at the highest energy will be able to determine the top-quark electroweak couplings with a sub-percent precision. ...
Joint energy distribution of the bottom quark and antiquark from decays of the top quark and antiquark produced in the reaction $e^+ e^- \to t \bar{t}$ is studied. Main emphasis is put on $CP$-violation effects in the interaction of the photon and $Z$ boson with the top quarks. Energy asymmetries of $b$ and $\bar{b}$ quarks, which give access to the $CP$-violating terms, are considered. To estimate the magnitude of these asymmetries, the $CP$-violating $\gamma t \bar{t} $ and $Z t \bar{t}$ couplings are calculated in one-loop model with exchange of the Higgs boson. Interaction of this boson with the top quarks is assumed to include scalar and pseudoscalar couplings. Values of these couplings are constrained from the recent CMS analysis. Energy dependence of the asymmetries of $b$ and $\bar{b}$ quarks is calculated up to $\sqrt{s}=1.2$ TeV and some interesting features of their behavior are observed. These observables can be of interest for future studies at electron$-$positron colliders CLIC and ILC.
... An important direction of research is study of properties of the top quark. These properties are planned to be explored precisely on future electron-positron colliders, such as International Linear Collider (ILC) [1] and Compact Linear Collider (CLIC) [2][3][4]. The ILC will start at the center-of-mass energy of 250 GeV followed by 500 GeV upgrade [4,5]. ...
... These properties are planned to be explored precisely on future electron-positron colliders, such as International Linear Collider (ILC) [1] and Compact Linear Collider (CLIC) [2][3][4]. The ILC will start at the center-of-mass energy of 250 GeV followed by 500 GeV upgrade [4,5]. The CLIC promises to be a good candidate for production of the on-mass-shell top quark and studying its properties. ...
... The CLIC promises to be a good candidate for production of the on-mass-shell top quark and studying its properties. At the first construction stage of the CLIC, the center-of-mass energy will be 380 GeV with expected integrated luminosity of 1 ab −1 , which will include 100 fb −1 collected near the tt production threshold [3,4,6]. ...
The distributions of the bottom quark in the process $e^+ e^- \to t \, \bar{t} \to b \, W^+ \, \bar{t}$ are considered at the $e^+ e^-$ energy corresponding to the first construction stage of the Compact Linear Collider. The cross sections of $e^+ e^- \to b \ldots$, as functions of the $b$-quark energy and angle with respect to the direction of the electron beam, are derived and calculated. The effects of physics beyond the Standard Model are included via the modified $\gamma t \bar{t}$ and $Z t \bar{t}$ couplings which naturally appear in effective field theories. In addition to the cross sections, the energy and angular asymmetries are calculated. The dependence of these observables on the $e^+ e^-$ energy is calculated, and features of this dependence is investigated.
... As discussed in Ref. 20, from the recent measurement by ATLAS 73 and later by CMS 74 Collaborations of light-by-light scattering in LHC Pb-Pb collisions, 75 one obtains a lower bound for √ β 100 GeV, which, on account of (48), implies monopole masses E 11 TeV; for the monopole solution of Ref. 72, with mass (49), the collider lower limit is E 15 TeV. Taking into account that monopoles are produced in pairs with their antiparticles in collisions, they are beyond reach of any LHC experiment, but may be accessible at future colliders [76][77][78] or cosmic searches. 14 Cosmological consequences of such monopoles, in particular their role in the electroweak phase transition and nucleosynthesis, have been discussed in Ref. 19, where we refer the interested reader for details. ...
In this review, we discuss recent developments in both the theory and the experimental searches of magnetic monopoles in past, current and future colliders and in the Cosmos. The theoretical models include, apart from the standard Grand Unified Theories, extensions of the Standard Model that admit magnetic monopole solutions with finite energy and masses that can be as light as a few TeV. Specifically, we discuss, among other scenarios, modified Cho-Maison monopoles and magnetic monopoles in (string-inspired, higher derivative) Born-Infeld extensions of the hypercharge sector of the Standard Model. We also outline the conditions for which effective field theories describing the interaction of monopoles with photons are valid and can be used for result interpretation in monopole production at colliders. The experimental part of the review focuses on, past and present, cosmic and collider searches, including the latest bounds on monopole masses and magnetic charges by the ATLAS and MoEDAL experiments at the LHC, as well as prospects for future searches.
A theoretical description of photon-pair production in polarized positron-electron annihilation is presented. Complete one-loop electroweak radiative corrections are calculated taking into account the exact dependence on the electron mass. Analytical results are derived with the help of the SANC system. The relevant contributions to the cross section are calculated analytically using the helicity amplitude approach. The cases of unpolarized and longitudinally polarized fermions in the initial state are investigated. Calculations are realized in the Monte Carlo integrator MCSANCee and generator ReneSANCe which allow one the implementation of any experimental cuts used in the analysis of e+e− annihilation data of both low and high energies.
We study the type-II first-order electroweak phase transition and dark matter (DM) phenomenology in both real and complex singlet extensions of SM. In the real singlet extension with a Z2 symmetry, we show that the parameter regions favored by the phase transition suffer from strong constraints from DM direct detection so that only a negligible fraction (fX ∼ 10⁻⁴ − 10⁻⁵) of DM composed of the real singlet scalar can survive the LUX and XENON1T constraints. In the complex singlet S case, we impose a CP symmetry S → S∗ to the scalar potential. The real component of S can mix with SM Higgs boson while the imaginary component becomes a DM candidate due to the protection of the CP symmetry. By taking into account the current experimental constraints of invisible Higgs decays, Higgs signal strength measurements, and dark matter detections, we find that there exists a large parameter space for the type-II electroweak phase transition to occur while explaining all of the dark matter relic density. We identify a subset of parameter space that is promising for future experiments, including the di-Higgs and Higgs signal strength measurements at the HL-LHC and the dark matter direct detection in the XENONnT project.
