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.     

Production of the neutral top-pion πt0 in association with a high-pw jet al the LHC

In the framework of the topcolor-assisted technicolor (TC2) model, we study the production of the neutral top-pion πt0 in association with a high-pT jet al the LHC, which proceeds via the partonic processes gg→πt0g, gq→πt0q, qq→πt0g, gb(b)→πt0b(b), and bb→πt0g. We find that it is very challenging to detect the neutral top-pion πt0 via the process pp→πt0 +jet-t-X→tt +jet + X, while the possible signatures of πt0 might be detected via the process pp→πt0 +jet+X→(tc+tc)+jet+X at the LHC.     

Production of Neutral Top-Pion Associated with a Gauge Boson at LHC

In this paper, we study the production of the neutral top-pion (Π⁰_t) associated with a gauge boson at the LHC, i.e. pp→Π⁰_tV(V=g,W,Z,γ). The cross section of pp→Π⁰_tg is at the level of 10² pb in the most parameter space. Such a process with the flavor-changing decay mode Π⁰_t→ tc might provide viable signatures to detect Π⁰_t at the LHC. The cross sections of other processes pp→Π⁰_tW(Z,γ) are too small to detect Π⁰_t, which open a window to distinguish the Higgs boson in the SM or MSSM from Π⁰_t.     

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.     

A Proposal on the Search for the Hybrid with I^G（J^PC）=1^—（1—＋）in the Process J／ψ→ρωππ at Upgraded BEPC／BES

We give the moment expressions for the boson resonances X with spin-parity JXPXC=0 ,1- ,1 and 2 posibly produced in the process J/ψ→ρX,X→b1(1235)π,b1→ωπ in terms of the generalized moment analysis method .The resonance with JXPXC=1- can e distingguished from other resonances by means of these moments exceptfor some rather special cases.The suggestion that the search for the hybrid with IG(JPC)=1-(1- ) can be performed in the decay channl J/ψ→ρωππat upgraded BEPC/BES is presented.     

Neutral Higgs Boson Pair Production in Standard Model with the Fourth Generation Quarks at LHC

We investigated the neutral Higgs boson pair production at the CERN Large Hadron Collider (LHC) in the SM with four families. We found that the gluon-gluon fusion mode is the most dominant one in producing neutral Higgs boson pair at the LHC, and it can be used to probe the trilinear Higgs coupling. If the heavy quarks of the fourth generation really exist within the SM, they can manifest their effect on the cross section of the Higgs pair production process at the LHC. Our numerical results show that there will be 2×10⁴ neutral Higgs boson pair production events per year if the next generation heavy quarks really exist, while there will be only 2×10³ events produced per year if there are only three families in the SM.     

Production of Charged Higgs Bosons from Left-Right Twin Higgs Model at TeV Energy e-γ Colliders

The left-right twin Higgs (LRTH) model predicts the existence of three additional Higgs bosons: one neutral Higgs ø⁰ and a pair of charged Higgs bosons ø^±. In this paper, we study two pair production processes of these new particles at the next generation eγ colliders, i.e., e^-γ → e^-ø⁺ø^-, ande^-γ→ ν_Rø^-ø⁰. We find that the production cross section of the process e^-γ →e^-ø⁺ø^- are at the level of several tens fb, the production cross section of the process e^-γ→ν_Rø^-ø⁰ can reach 0.35 fb with the reasonable parameter values. As long as the charged Higgs bosons are not too heavy, we conclude that these processes might be used to test for the left-right twin Higgs model in future high-energy linear collider experiments.     

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.     

Formalism of Helicity Coupling Amplitudes for J/ψ→π+π-π0

The formalisms of helicity coupling amplitudes for J/ψ→π^＋π^-π^0 are presented. A detailed discussion is also given on the barrier factor, Breit Wigner, and density matrix. A Monte Carlo simulation of J/ψ→ρ（770）π→π^＋π^-π^0 is carried out. The results show that the p（770） resonance is well reproduced compared with experimental data.     

Single Production of Top Quark via e-γ Collision in Left-Right Twin Higgs Model

In the context of the left-right twin Higgs (LRTH) model, we fist study single production of the standard model (SM) top quark via e^-γ collisions. We find that the corrections of the LRTH model to the cross section of the process e^-γ→ν_ebt might be observed only for f≤750 GeV and the heavy top quark mass scale M≥500 GeV in future high energy linear e⁺e^- collider (LC) experiment with the center-of-mass (CM) energy s^½=500 GeV and a yearly integrated luminosity of £=100 fb^-1. We also consider single production of the heavy top quark T via e^-γ collisions. Our numerical results show that the possible signals of the heavy top quark T might be observed via the decay channel T→φ⁺b→tbb in future LC experiment with s^½=3 TeV and £=500 fb^-1.     

A Study on Radiative Dileptonic Decays B0(Bs)→γ l+l-

We study the rare radiative dileptonic decays B⁰(B_s)→γ l⁺l^- (l=e,μ) in the standard model. By using the B meson wave function constrained by non-leptonic decays, the branching ratios turn out to be of the order of 10^-9 for B_s→γ μ⁺μ^-, γe⁺e^-, and 10^-10 for B⁰→γμ⁺μ^-, γe⁺e^-. Based on the study, these decays are accessible at the near future LHC-b experiment, which are useful to determine the B(B_s) wave function.     

Charged Top-Pion Production at Hadron Colliders

We studied the charged top-pion in the topcolor assisted technicolor model (TC2). If the charged top-pions are heavy, m_πt >m_t+m_b, they will decay mainly via the channel π⁺_t → t \bar{b}. We also calculated the production ofcharged top-pion at the Tevatron and LHC. The cross section can reach to 100 fb at the Tevatron and dozens of pb at the LHC depending on the mass of the top-pion.     

Process e^-у→ e^-H in Littlest Higgs Model

In the context of the littlest Higgs （LH） model, we estimate the production cross section of the process e^-у→ e^-H in the future high-energy linear e^＋e^- collider （ILC） with the center-of-mass （CM） energy √S = 500 GeV. Our numerical results show that the contributions of the LH model Co this process are very small in most of the parameter space allowed by the electroweak precision measurement data, and are very diffcult to be detected in the future ILC experiments.     

Study on Charged Top-Pion Decay Processes

In the framework of top-color assisted technicolor (TC2) theory, we study the four decay processes of charged top-pion, i.e., Π⁺_t→ t\bar{b}, Π⁺_t→ c\bar{b}, Π⁺_t→ W⁺γ, Π⁺_t→ W⁺Z⁰. The decay branching ratio of these modes are calculated. The results show that the main decay channels of charged top-pion are the tree level modes: Π⁺_t → t\bar{b} and Π⁺_t → c\bar{b}. Light Π⁺_t is easier to be detected than heavy one at future coliders. So, the study provides us with some useful informations to search for charged top-pion.     

ON THE REACTION MECHANISM AND THE SELECTION RULE IN THE DOUBLE CHARGE EXCHANGE REACTION OF PIONS ON NUCLEI (DCX)-A STUDY OF THE CONNECTION BETWEEN THE 2β-DECAY AND DCX ON jP=O+ NUCLEI

It is shown that in the pion induced double charge exchange reaction on J^p=O⁺→O⁺ nuclei,there exists a possible new reaction mechanism π⁺(Δ⁰,Δ⁺⁺)π^- or π⁺(Δ^-,Δ⁺)π^- in so-called single step process,while that old speculative mechanism π⁺(N,Δ)π^- or π⁺(N,Δ)π^- is firbidden by a well-known selection rule which has been indicated in the theory of the nuclear 2β-decay.     

The Three-Pion Decays of the a1(1260)

We investigate the decay of a₁⁺ (1260)→π⁺π⁺π^- with the assumption that the a₁(1260) is dynamically generated from the coupled channel ρπ and KK^* interactions. In addition to the tree level diagrams that proceed via a₁⁺ (1260)→ρ⁰π⁺→π⁺π⁺π^-, we take into account also the final state interactions of ππ→ππ and KK→ππ. We calculate the invariant π⁺π^- mass distribution and also the total decay width of a₁⁺ (1260)→π⁺π⁺π^- as a function of the mass of a₁(1260). The calculated total decay width of a₁(1260) is significantly different from other model calculations and tied to the dynamical nature of the a₁(1260) resonance. The future experimental observations could test of model calculations and would provide vary valuable information on the relevance of the ρπ component in the a₁(1260) wave function.     

Study on the Effects of the Light CP-odd Higgs via the Leptonic Decays of Pseudoscalar Mesons

To explain the anomalously large decay rate of Σ⁺→p+μ⁺μ^-, it was proposed that a new mechanism where a light CP-odd pseudoscalar boson of m_A1⁰=214.3 MeV makes a crucial contribution. Later, some authors have studied the transition π⁰→ e⁺e^- and r → γA₁⁰ in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of Σ⁺→ p+μ⁺μ^- because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions π⁰→ e⁺e^-;η(η')→ μ⁺μ^-; η_c→ μ⁺μ^-; η_b→τ⁺τ^- within the same framework. It is noted that for π⁰→ e⁺e^-, the standard model (SM) prediction is smaller than the data, whereas the experimental central value of η→μ⁺μ^- is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of A₁⁰ may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would check if we can obtain a universal mass for A₁⁰ which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible to have such a mass with the same coupling |gl|. Therefore we conclude that the phenomenology does not favor such a light A₁⁰, even though a small window is still open.     

A search for charged Higgs bosons at tristan

We searched for pair production of charged Higgs bosons via e⁺e⁻ annihilation, using data (23.3 pb⁻) collected by the TOPAZ detector in the energy range . We observed no evidence for charged Higgs pair production and extended the excluded region in the M_H^±---BR (hadron) plane. The 95% CL lower mass limit is the most stringent for BR (hadron) = 0.6, giving m_H^±<22 GeV.     

Probing the Stau－Stau－Higgs Couplings in the MSSM at NLC

In the minimal supersymmetric standard model (MSSM) with CP violating phases, this paper discusses the production of the lJghtest neutral Higgs boson in association with tau sleptons at future high-energy e^ e^- linear colliders. In parameter space of the constrained MSSM, the production cross section of e^ e^→h^0T1 T1^- can be very substantial at high energies. This process would provide a production mechanism for probing couplings of neutral Higgs bosoas to tau sleptons as well as some soft supersymmetric breaking parameters at next linear colliders.     

Effects of a Family Non-universal Z' Boson in \bar{B}_d→μ+μ- and B- →π-μ+μ-,ρ-μ+μ- Decays

Motivated by the recently updated experimental measurement on \bar{B}_d→μ⁺μ^- and B^-→π^-μ⁺μ^- decays by CDF and Belle collaborations, we revisit these
decays, as well as B^-→ρ^-μ⁺μ^- decay, within the Standard Model, and evaluate the effects of a family non-universal Z' boson. Under the constraint from {\cal B}(B^-→π^-μ⁺μ^-), we find the ranges of the Z' couplings S^LR_μμ< -5.2×10^-2 or D^LR_μμ < -8.1× 10^-2 are excluded. Within the allowed Z' parameters spaces, comparing with the SM predictions, we find that {\cal B}(\bar{B}_d→ μ⁺μ^-, {\cal B}(B^-→ π^-μ⁺μ^-), and {\cal B}(B^-→ρ^-μ⁺μ^-) could be enhanced by a factor about
226%, 245%, and 254%, respectively, byZ' contributions. However, they are hardly to be reduced. Furthermore, the zero crossing in the normalized forward-backward asymmetry spectrum of B^- →ρ^-μ⁺μ^- decay at low dimuon mass always exists.