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1.
The colour reconnection effects were intensively studied with LEP2 data and are a dominant sources of systematic uncertainty in the W boson mass in e+e? annihilation at LEP2 and one of a dominant sources of systematic uncertainty in the top quark mass determination at hadronic colliders. With the discovery of Higgs boson, a new arena for the effects studies opened up. The effects are discussed within the existent different models and what future tests may come with a future FCC-ee.  相似文献   

2.
We study the three body lepton flavor violating (LFV) decays μ ?e ? e + e ?, \(\tau^{-} \to l_{i}^{-} l_{j}^{+} l_{j}^{-}\) and the semileptonic decay τμφ in the flavor changing neutral current (FCNC) mediated Z boson model. We also calculate the branching ratios for LFV leptonic B decays, B d,s μe, B d,s τe, B d,s τμ and the conversion of muon to electron in Ti nucleus. The new physics parameter space is constrained by using the experimental limits on μ ?e ? e + e ? and τ ?μ ? μ + μ ?. We find that the branching ratios for τeee and τμφ processes could be as large as \({\sim}{\mathcal{O}}(10^{-8})\) and \(\mathrm{Br}(B_{d,s} \to \tau \mu,~ \tau e) \sim {\mathcal{O}}(10^{-10})\). For other LFV B decays the branching ratios are found to be too small to be observed in the near future.  相似文献   

3.
The branching ratios and differential distributions for the four-leptonic decays \({B^ - } \to {\mu ^ + }{\mu ^ - }{\bar v_e}{e^ - }\), \({B^ - } \to {e^ + }{e^ - }{\bar v_\mu }{\mu ^ - }\), and \({B^ - } \to {\mu ^ + }{\bar v_\mu }{\mu ^ - }{\mu ^ - }\) are calculated within the Standard Model. The branching ratios for the rare decays Bd,se+e?μ+μ? and Bd,sμ+μ?μ+μ? are estimated. Methods for testing the lepton universality in rare multileptonic decays of charged and neutral B mesons are proposed.  相似文献   

4.
The decay of mesons K +π ? l + l+ and D +K ? l + l+ (l, l′ = e, μ) involving a change of lepton number ΔL = 2 is considered in a supersymmetric extension of the standard model in which R-parity is not conserved due to trilinear Yukawa interactions. The obtained estimates for the probabilities of these decays are significantly lower than the direct experimental upper limits.  相似文献   

5.
Based on the data for the transitions π0, η, η′ → γγ*(Q2) and reactions of the e+e? annihilations e+e?ρ0, ω, ? and e+e?hadrons at 1<E e+e? <3.7 GeV, we determine the light-quark components of the photon wave function \(\gamma * (Q^2 ) \to q\bar q(q = u,d,s)\) for the region 0 ? Q2 ? 1 (GeV/c)2.  相似文献   

6.
Recent results on B-hadron physics in ATLAS are reviewed. A new measurement of CP-violating parameters in B s J/ψφ decay is performed on full Run 1 statistics. Branching fraction BR(B s → μ+μ?) = (0.9 ?0.8 +1.1 )×10?9 is measured, below the Standard Model (SM) prediction.  相似文献   

7.
The most general form of an effective two-doublet Higgs potential whose parameters are complex-valued and whose CP invariance is violated explicitly in the minimal supersymmetric model caused by Higgs boson interaction with third-generation squarks is considered. Higgs boson states are obtained and their masses are calculated, along with the decay widths of the lightest Higgs boson and the cross section for its production, in the case of substantial mixing between the CP-even states h and H and the CP-odd state A.  相似文献   

8.
Mixing of K 0 and B 0 mesons is studied in the scope of the minimum supersymmetry model (MSSM) with a type II Yukawa sector and explicit violation of CP invariance in the Higgs potential. The mixing parameters Δm LS and ? are calculated in the limit of the low-energy four-fermion approximation with a charged Higgs boson exchange. It is shown that supersymmetric effects are very small for K 0 mesons and may be quite significant for B s 0 and B d 0 mesons, which imposes constraints on the MSSM parameter space.  相似文献   

9.
The potential of experiments at e + e ? colliders to search for a signal of a new pseudoscalar Higgs boson and to study its CP properties is analyzed. A new Higgs boson coupling to the b quark and τ lepton, which is parameterized in a model-independent way as m b /v(a + iγ5 b), is chosen to be an indicator of its CP nature. We study the e + e ? → τ+τ?vv, e + e ?b \(\bar b\)vv, and e + e ?e + e ? b \(\bar b\) processes highly sensitive to anomalous Higgs boson couplings due to the dominant contributions from the vector boson fusion processes W*W* → H and Z*Z* → H in the central region. It is shown that the study of polarization of particles in the final state could help to separate the contributions from the scalar and pseudoscalar Higgs bosons. For instance, the consideration of the cascade decays of τ leptons in the e + e ? → τ+τ?vv process allows one to determine reliably the CP state of the Higgs boson as well as the value and the sign of the b parameter. As a result of our analysis, we develop a search strategy for a signal of a new pseudoscalar Higgs boson in future experiments at linear e + e ? colliders, which will allow one to understand the CP nature of the Higgs boson and set the bounds on its couplings to fermions.  相似文献   

10.
In this paper, we have proposed S U(2) non-Abelian electromagnetism gauge theory. In the theory, photon has self-interaction and interaction between them, which can explain photon entanglement phenomenon in quantum information. Otherwise, we find there are three kinds photons γ +, γ ? and γ 0, they have electric charge + e γ , ? e γ and 0, respectively, these prediction are accordance with some experiment results.  相似文献   

11.
The contribution of the charged Higgs boson to the production of a tb pair in pp collisions at LHC is investigated. It is shown that, due to H±-boson exchange, the total yield of tb pairs is modified significantly for small and large values of tan β. At small values of tan β, the production of right-handed t quarks is also expected, however, in contrast to what occurs in the case of only W±-boson exchange, generating left-handed t quarks exclusively. This fact provides the possibility of separating the H± and W± contributions by investigating the angular distributions of products originating from top-quark decay. A detailed simulation of signal and relevant background processes is performed.  相似文献   

12.
A numerical value for the running electromagnetic-coupling constant in the \(\overline {MS} \) scheme is calculated at a low-energy normalization scale equal to the τ-lepton mass Mτ. This low-energy boundary value is used for running the electromagnetic coupling to larger scales, where high-precision experimental measurements can be performed. Particular scales of interest are the b-quark mass for studying ?-resonance physics and the Z-boson mass M Z for high-precision tests of the Standard Model and for the determination of the Higgs boson mass from radiative corrections. A numerical value of the running electromagnetic-coupling constant at M Z in the on-shell renormalization scheme is also given.  相似文献   

13.
The probability of W-boson decay into a lepton and a neutrino, \(W^ \pm \to \ell ^ \pm \bar \nu _\ell \), in a strong electromagnetic field is calculated. On the basis of the method for deriving exact solutions to relativistic wave equations for charged particles, an exact analytic expression is obtained for the partial decay width \(\Gamma () = \Gamma (W^ + \to \ell ^ + \bar \upsilon _\ell )\) at an arbitrary value of the external-field-strength parameter \( = eM_W^{ - 3} \sqrt { - (F_{\mu \upsilon } q^\upsilon )^2 } \). It is found that, in the region of comparatively weak fields (??1), field-induced corrections to the standard decay width of theW boson in a vacuum are about a few percent. As the external-field-strength parameter is increased, the partial width with respect to W-boson decay through the channel in question, Γ(?), first decreases, the absolute minimum of Γmin=0.926Γ(0) being reached at ?=0.6116. A further increase in the external-field strength leads to a monotonic growth of the decay width of the W boson. In superstrong fields (??1), the partial width with respect to W boson decay is greater than the corresponding partial width \(\Gamma ^{(0)} (W^ \pm \to \ell ^ \pm \bar \upsilon _\ell )\) in a vacuum by a factor of a few tens.  相似文献   

14.
We present a new study of quasi-elastic W and Z scattering processes in high-energy \(e^+e^-\) collisions, based on and extrapolating the low-energy effective theory which extends the standard model with a \(125\;\text {GeV}\) Higgs boson. We parameterize deviations in the low-energy range in terms of the dimension-eight operators that arise in the effective theory. Smoothly extending this to higher energy, we study a set of simplified models of new physics in W / Z scattering, (1) a structureless extrapolation of the effective theory, and (2) scalar and tensor resonance multiplets. The high-energy asymptotics of all models is regulated by a universal unitarization procedure. This enables us to provide benchmark scenarios which can be meaningfully evaluated off shell and in exclusive event samples, and to determine the sensitivity of an \(e^+e^-\) collider to the model parameters. We analyze the longitudinal vector-boson scattering modes, where we optimize the cuts for the fiducial cross section for different collider scenarios. Here, we choose energy stages of 1.0, 1.4 and 3 TeV, as motivated by the extendability of the ILC project and the staging scenario of the CLIC project.  相似文献   

15.
F2 color centers with a superhigh concentration (5000-cm–1 absorption coefficient at 450 nm) were formed by high-density electron beams in a layer of LiF crystals of micrometer thickness. The F2-centers excited by high-power nanosecond wide-band optical pulses (the “soft” pumping regime) efficiently amplified the laser radiation and showed high stability under these conditions. A low stability of F2-centers to laser radiation (the “hard” excitation regime) is explained by the dissociation of (F 2 + , F) pairs induced by two-step ionization of F2-centers: (2hν > 4.5 eV) → F2 → (F2)* → F 2 + + e; F + eF; F 2 + + F → 3F.  相似文献   

16.
The effect of Higgs bosons on the anomalous magnetic moment of the muon is considered within the model that is based on the SU(2)L×SU(2)R×U(1)B–L gauge group and which involves a bidoublet and two triplets of Higgs fields (left-right model). For the Yukawa coupling constants and the masses of Higgs bosons, the regions are found where the model leads to agreement with experimental results obtained at the Brookhaven National Laboratory (BNL) for the anomalous magnetic moment of the muon. In order to explore corollaries from the constraints obtained for the parameters of the Higgs sector, the processes e+e?μ+μ?, τ+τ? and μ+μ?μ+μ?, τ+τ? are considered both within the left-right model and within the model involving two Higgs doublets (two-Higgs-doublet model). It is shown that, if the mass of the lightest neutral Higgs boson does indeed lie in the range 3.1–10 GeV, as is inferred from the condition requiring the consistency of the two-Higgs-doublet model with the data of the BNL experiment, this Higgs boson may be observed as a resonance peak at currently operating e+e? colliders (VEPP-4M, CESR, KEKB, PEP-II, and SLC). In order to implement this program, however, it is necessary to reduce considerably the scatter of energy in the e+ and e? beams used, since the decay width of the lightest neutral Higgs boson is extremely small at such mass values. It is demonstrated that, in the case of the left-right model, for which the mass of the lightest neutral Higgs boson is not less than 115 GeV, the resonance peak associated with it may be detected at a muon collider.  相似文献   

17.
O. P. Yushchenko  V. F. Kurshetsov  A. P. Filin  S. A. Akimenko  A. V. Artamonov  A. M. Blik  V. V. Brekhovskikh  V. S. Burtovoy  S. V. Donskov  A. V. Inyakin  A. M. Gorin  G. V. Khaustov  S. A. Kholodenko  V. N. Kolosov  A. S. Konstantinov  V. M. Leontiev  V. A. Lishin  M. V. Medynsky  Yu. V. Mikhailov  V. F. Obraztsov  V. A. Polyakov  A. V. Popov  V. I. Romanovsky  V. I. Rykalin  A. S. Sadovsky  V. D. Samoilenko  V. K. Semenov  O. V. Stenyakin  O. G. Tchikilev  V. A. Uvarov  V. A. Duk  S. N. Filippov  E. N. Guschin  Yu. G. Kudenko  A. A. Khudyakov  V. I. Kravtsov  A. Yu. Polyarush  V. N. Bychkov  G. D. Kekelidze  V. M. Lysan  B. Zh. Zalikhanov 《JETP Letters》2018,107(3):139-142
Recent results from OKA setup concerning form factor studies in Ke3 decay are presented. About 5.25 M events obtained for decays of 17.7 GeV/cK+ are selected for the analysis. The linear and quadratic slopes for the decay form factor f+(t) are measured: λ'+ = 2.95 ± 0.022 ± 0.018 × 10 -2 for the linear slope fit and λ+ = 2.611 ± 0.035 ± 0.028 × 10 -2, λ"+ = 1.91 ± 0.19 ± 0.14 × 10 -3 for the quadratic one. The scalar and tensor contributions are compatible with zero. Several alternative parametrizations are tried: the Pole fit parameter is found to be M V = 891 ± 3 MeV; the parameter of the dispersive parametrization is measured to be Λ+ = 2.458 ± 0.018 × 10-2.  相似文献   

18.
We investigate effects of CP symmetry violation in the decay of a scalar particle X (the Higgs boson) into two off-mass-shell Z bosons both decaying into a fermion–antifermion pair, \(X \to {Z_1}*{Z_2}* \to {f_1}{\bar f_1}{f_2}{\bar f_2}\). The most general form of the amplitude of the transition XZ1*Z2*, wherein the boson X may not have definite CP parity, is considered. The applicability limits of the narrow-Z-width approximation used in obtaining differential widths of the decay under consideration are determined. Various observables connected with the structure of the amplitude of the decay XZ1*Z2* are studied. These observables are analyzed in the Standard Model as well as in models conceding indefinite CP parity of the Higgs boson. An experimental measurement of angular and invariant mass distributions of the decay \(X \to {Z_1}*{Z_2}* \to {f_1}{\bar f_1}{f_2}{\bar f_2}\) at the LHC can give information about the CP properties of the Higgs boson and its interaction with the Z boson.  相似文献   

19.
The fundamentals of the theory of the electronic structure of impurity clusters and the results of numerical calculations for the iron-, lanthanum-, and actinium-group ions in Me+n: [L]k clusters are presented. The effects of the interionic distance and ligands in the Me+n: [L]k clusters on the electronic structure of the nl N and nlN?1nl′ configurations of the 3d, 4f, and 5f ions are considered. The correspondence between the optical and x-ray spectra of different impurity crystals is also analyzed.  相似文献   

20.
Recent experiment by A1 Collaboration at Mainz, namely identification of Λ 4H hyperfragment from primary Λ 9Li hypernucleus produced in reaction (e, eK +), stirred renewed interest in baryonic decay of hypernuclei. The important role of s ?1 s Λ excitation in p-shell hypernuclei as well as the existence of selection rules connected with [f] (Young diagram) was noted earlier within Translational Invariant Shell Model (TISM). The particular conditions of the present experiment (reaction is not selective and produces highly excited states) dictate extension of the simplest TISM: expansion of the harmonic oscillator basis space and compression of multiplets (to only (λμ) for L and [f] for S, T). Such modified TISM explains abundance production of Λ 4H hyperfragment and predicts production of another Hyper Hydrogen Λ 6H.  相似文献   

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