Single Production of Charged Top-Pions at High Energy Linear e+e- Colliders

The dominant decay modes of charged top-pions (π±t ) are tb or ~b. We consider the single production ofcharged top-pions in association with a top quark via e+ e- annihilation and calculate the production cross section of theprocesses e+ e- → t-bπ+ (tb-π-) at the leading order. We find that it can reach 1.2 fb with reasonable parameter values.The charged top-pions may be detected via the channel tbπ± in the future high energy e+ e- colliders.     

Discriminating the HTM and MLRSM models in collider studies via doubly charged Higgs boson pair production and the subsequent leptonic decays

We present a case study for the doubly charged Higgs boson H~(±±) pair production in e~+e~-and pp colliders with their subsequent decays to four charged leptons.We consider the Higgs Triplet Model(HTM),which is not restricted by the custodial symmetry,and the Minimal Left-Right Symmetric Model(MLRSM).These models include scalar triplets with different complexities of scalar potentials and,because of experimental restrictions,completely different scales of non-standard triplet vacuum expectation values.In both models,a doubly charged Higgs boson H~(±±) can acquire a mass of hundreds of gigaelectronvolts,which can be probed at the HL-LHC,future e~+e~-,and hadron colliders.We take into account a comprehensive set of constraints on the parameters of both models coming from neutrino oscillations,LHC,e~+e~-,and low-energy lepton flavor violating data and assume the same mass of H~(±±).Our finding is that the H~(±±) pair production in lepton and hadron colliders is comparable in both models,though more pronounced in the MLRSM.We show that the decay branching ratios can be different within both models,leading to distinguishable four-lepton signals,and that the strongest are 4μ events yielded by the MLRSM.Typically,we find that the MLRSM signals are one order of magnitude larger those in the HTM.For example,the pp→ 4μMLRSM signal for 1 TeV H~(±±) mass results in a clearly detectable significance of S■11 for the HL-LHC and S■290 for the FCC-hh.Finally,we provide quantitative predictions for the dilepton invariant mass distributions and lepton separations,which help to identify non-standard signals.     

New physics and two boosted W-jets plus missing energy

We show that the signature of two boosted W-jets plus substantial missing energy is very promising for probing heavy charged resonances(X~±) through the process of pp→X~+X~-→W~+W~-X~0 X~0,where X~0 denotes the dark matter candidate.The hadronic decay mode of the W boson is considered to maximize the number of signal events.When the mass split between X~± and X~0 is large,the jet-substructure technique must be utilized to analyze the boosted W-jet.Here,we consider the process of chargino pair production at the LHC,i.e.,pp→χ_1~+χ_1~-→W~+W~-χ_1~0χ_1~0,and demonstrate that the proposed signature is able to cover more parameter space of m_(χ_1~±) and m_(χ_1~0),than the conventional signature of multiple leptons plus missing energy.More importantly,the signature of interest is not sensitive to the spin of heavy resonances.     

Pair Production of the Doubly Charged Leptons via Electroweak Vector Boson Fusion at the Large Hadron Collider

Pair production of the doubly charged leptons X±± via vector boson fusion （γγ, Zγ and WW） at the large hadron collider is studied. Our numerical results show that the cross section via Zγ fusion is very small. For the center-of-mass energy √s= 14 TeV and Mx = 200 650 GeV, the values of the cross sections σγγ and σww are in the ranges of 5.2 fb-0.04 fb and 20.2 fb 1.2 fb, respectively.     

Exclusive Ω_(ccc)~(++)Ω_(ccc)~(--) Production from Z~0/r~* Decays

Based on the quark model the cross section for the e~+e~-→ Z~0/r~*→Ω_(ccc)~(++)Ω_(ccc)~(--) exclusive process is investigated at the tree level. Compared with the Z~0→Ω~-Ω~+ decay, our result shows that the Z~0 boson favors decaying into charmed baryon pairs. The results are also compared with the calculation of inclusively charmed baryon production.     

Hidden-charm Pentaquark Production at e~+e~- Colliders

We study one possible production mechanism for the hidden-charm pentaquark via a color-octet cc pair fragmentation in e~+e~-collision.The pentaquark production at B factory energy is dominated by e~+e~-→ccg→P_c+X,while at Z~0pole energy,there are several partonic processes playing significant role.Our results show that it is possible to search for the direct pentaquark production signal at e~+e~-colliders,which is important to understand the properties of pentaquark.     

Production of Charged Scalars from the Littlest Higgs Model Associated with Top Quark at LHC

The littlest Higgs （LH） model is the most economical one among various little Higgs models, which predicts the existence of the charged scalars Φ^±. In this paper, we study the production of the charged Higgs boson Φ^- with single top quark via the process gb →tΦ^- at the CERN Large Hadron Collider （LHC）. The numerical results show that the production cross section is sma/ler than 0.2 pb in most of the parameters space, it is very difficult to observe the signatures of the charged scalars via the process pp → gb ＋ X → tΦ^- ＋ X at the LHC experiments. However, it can open a window to distinguish the top-pions in the TC2 model or charged Higgs in the MSSM from Φ^±.     

Detection of Charged Higgs Bosons in e~+e~-(γγ)→tφ~- Production at the ILC

In the context of the left-right twin Higgs (LRTH) model,we have studied the charged Higgs bosons production processes e~+e~-(γγ)→tφ~at the International Linear Collider (ILC).It is found that the cross sections of these two processes could reach a few fb with reasonable parameter values.With the yearly integrated luminosity of L=500 fb-1 expected at the ILC,one could collect hundreds up to thousands of charged Higgs events via these two processes.Therefore,our researches in this paper can help us search for charged Higgs bosons,and furthermore,to test the LRTH model.     

Production and constraints for a massive dark photon at electron-positron colliders

Dark sector may couple to the Standard Model via one or more mediator particles.We discuss two types of mediators:the dark photon A’and the dark scalar mediatorΦ.The total cross-sections and various differential distributions of the processes e+e-→qqA’and e+e→qqφ(q=u,d,c,s and b quarks)are discussed.We focus on the study of the invisible due to the cleaner background at future e+e-colliders.It is found that the kinematic distributions of the two-jet system could be used to identify(or exclude)the dark photon and the dark scalar mediator,as well as to distinguish between them.We further study the possibility of a search for dark photons at a future CEPC experiment with s1/2=91.2 GeV and 240 GeV.With CEPC running at s1/2=91.2 GeV,it would be possible to perform a decisive measurement of the dark photon(20 GeV相似文献   

Heavy Charged Leptons from Type-III Seesaw and Pair Production of the Higgs Boson H at the International Linear e＋e- Collider

Type-III seesaw scenario predicts the existence of the heavy charged leptons, which might generate observable signals in future collider experiments. We consider the contributions of these new particles to the process e＋e- →HH. We find that, for the large mixing between the light and heavy leptons, these new particles can indeed generate significant contributions to this process.     

Detection of Charged Higgs Bosons in e+e-(γγ)→tbφ- Production at the ILC

In the context of the left-right twin Higgs (LRTH) model, we have studied the charged Higgs bosons production processes e⁺e^-(γγ)→tbφ^- at the International Linear Collider (ILC). It is found that the cross sections of these two processes could reach a few fb with reasonable parameter values. With the yearly integrated luminosity of L=500 fb^-1 expected at the ILC, one could collect hundreds up to thousands of charged Higgs events via these two processes. Therefore, our researches in this paper can help us search for charged Higgs bosons, and furthermore, to test the LRTH model.     

Single Charged Top-Pion Production at the Next Generation e+e- Colliders

The single charged top-pion production processes e⁺e^-→t\bar{b}Π_t^- and e⁺e^-→ W⁺Π_t^- are studied in the framework of top-color-assisted technicolor (TC2) model. Our studies show that the cross section σ(e⁺e^-→t\bar{b}Π_t^-) reaches the level of tens of fb and σ(e⁺e^-→W⁺Π_t^-) reaches the level of a few fb. With the yearly integrated luminosity of L～500 fb^-1 expected at the planned colliders, one could collect thousands of charged top-pion of events via the process e⁺e^-→t\bar{b}Π_t^- and hundreds of events via the process e⁺e^-→W⁺Π_t^-. The flavor changing decay mode Π_t^-→b\bar{c} is the best channel to detect charged top-pion due to the clean SM background. With a large number of events and the clean background, the charged top-pion should be observable at the planned colliders. Therefore, our studies in this paper can help us to search for charged top-pion, and furthermore, to test the TC2 model.     

Single Production of Doubly Charged Higgs Boson via eγ Collision in Higgs Triplet Model

The Higgs triplet model (HTM) predicts the existence of a pair of doubly charged Higgs bosons H^±± . Single production of H^±± via eγcollision at the next generation e⁺e^- International Linear Collider (ILC) and the Large Hadron electron Collider (LHeC) is considered. The numerical results show that the production cross sections are very sensitive to the neutrino oscillation parameters. Their values for the inverted hierarchy mass spectrum are larger than those for the normal hierarchy mass spectrum at these two kinds of collider experiments. With reasonable values of the relevant free parameters, the possible signals of the doubly charged Higgs bosons predicted by the HTM might be detected in future ILC experiments.     

SUSY Virtual Effects on the Production of tq at LEPPI

Virtual effects of supersymmetry on the-flavor changing process at LEPII are calculated in the minimal supersymmetric standard model (MSSM). We analyze the cross section of e⁺e^- → γ, Z⁰ → tq, and find that even for the most distinguishable mode e⁺e^- → γ, Z⁰ → tc, the effect is small compared with the SM expectation.     

Charged Higgs Pair Production in a General Two Higgs Doublet Model at e^＋e^- and μ^＋μ^- Linear Colliders

In this paper, charged Higgs pair production through l^＋l^- → H^＋ H^-, where l = e or μ, is studied within the framework of a general Two Higgs Doublet Model （2HDM）. The analysis is relevant to a future e^＋e^- or μ^＋ μ^- collider operating at center of mass energy of √s = 500 GeV. Two different scenarios of small and large a values are studied. Here a is the parameter, which diagonMizes the neutral CP-even Higgs boson mass matrix. Within the Minimal Supersymmetric Standard Model （MSSM）, cross section of this process is almost the same at e＋ e- and #＋#- colliders. It is shown that at e^＋e^- eolliders within a general 2HDM, cross section is not sensitive to the mass of neutral Higgs bosons, however, it can acquire large values up to several picobarn at μ^＋μ^- colliders with the presence of heavy neutral Higgs bosons. A scan over Higgs boson mass parameter space is performed to analyze the effect of large masses of neutral Higgs bosons involved in the s-channel propagator and thus in the total cross section of this process.     

Top Quark Polarization and Spin Correlation in the Littlest Higgs Model with T-Parity at the ILC

In the framework of the littlest Higgs model with T-parity(LHT),we study the top quark spin correlation and polarization at the International Linear Collider(ILC).We find that the top quark polarization asymmetry δP t and the left-right asymmetry δA LR can respectively reach-35% and-37.5% for s～(1/2)=500 GeV and s～(1/2)=1000 GeV via e+e-collision,which can reach the observable level at the ILC.By contrast,the spin correlation δC is smaller.The correlation behaviors of these observables at the e+e-collision and the γγ collision will be helpful to distinguish different models and test the LHT model at the ILC.     

正负电子湮灭过程的核子激发态N*产生(英文)

目前,正负电子湮灭过程的核子激发态N*产生的实验数据主要来自于粲偶素能区。粲偶素衰变到核子激发态过程类似于其类时电磁形状因子测量过程,正反粲夸克短程湮灭提供了近乎于点源的胶子强子化过程。与γN,eN,πN反应互补,这一新的N*产生源具有同位旋和低自旋筛选的优势。综述了正负电子湮灭过程的核子激发态N*产生的实验情况和相关的唯象进展,同时讨论未来发展的一些新方向,如正负电子湮灭过程的核子激发态N*产物的一些新来源等。Up to now, the N* production from e+e- annihilations has been studied only around charmonium region. Charmonium decays to N*s are analogous to (time-like) EM form factors in that the charm quark annihilation provides a nearly pointlike (ggg) current. Complementary to other sources, such as πN, eN and γN reactions, this new source for N* spectroscopy has a few advantages, such as an isospin filter and a low spin filter. The experimental results on N* from e+e- annihilations and their phenomenological implications are reviewed. Possible new sources on N* production from e+e- annihilations are discussed.     

On the conventional QED interpretation of the GSI ee narrow resonances

A possible mechanism for the GSI e⁺e^- narrow resonances as being due to non-perturbative effects of conventional QED is proposed. An application of the quasi-potential approach discloses a set of new resonances in a system of two charged particles. Numerical calculations agree with data on e⁺e^- and pp narrow resonances. Additional new resonances are predicted for e⁺e^-, pp, e^-e^- systems.     

A POSSIELE SOURCE OF EXCESS OF Z0→e+e-γ EVENTS

The observation of the excess of Z⁰→e⁺e^-γ can be explained by assuming that Z⁰ is radiatively decayed into a new scalar particle P⁰ which is subsequently turned into an e⁺e^- pair. We argue that this assuhption does not conflict with the present experimental results.