Discriminating scalar and pseudoscalar weak bosons via toponium → γ + boson

The production of Higg's or neutral technipion spin-zero bosons (szb) in toponium decay is examined. Different methods for determining the parity of these bosons are discussed. The decay width Γ(m³S₁ → γ + szb) is very sensitive to the parity of the szb and it is shown how comparing the widths of different toponium states can be used to determine the szb parity. The method is applicable for a szb within 30% of the toponium mass.     

Effect of weak neutral currents in the process e− + p → e− + γ + X

Polarization effects in the inclusive process e^– + p e^– + + X due to the neutral current are studied in the framework of the Weinberg-Salam model. Expressions for the asymmetry parameters and the degree of circular polarization of the photons are obtained in the quark-parton picture. It is shown that measurement of such quantities gives additional information about the quark structure of the hadronic weak neutral current.Paper presented at the scientific session of the nuclear physics branch, USSR Academy of Sciences and the Moscow State University on Electromagnetic and Weak Interactions (Moscow, January 16–20, 1979).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 96–99, January, 1981.     

Probing HZγ and Hγγ anomalous couplings in the process e~+e~-→ Hγ

We propose to measure the HZγ and Hγγ anomalous couplings in the process e+e-→Hγ with the sequential decay of H→bˉb. The discovery potential of observing the anomalous couplings are explored in detail.Our study shows that future electron–positron colliders have great potential to test the HZγ and Hγγ couplings.Conservative bounds on the two anomalous couplings are also derived when no new physics signal is detected on top of the SM backgrounds.     

Search for hadronic decays of a light Higgs boson in the radiative decay Υ→γA0

We search for hadronic decays of a light Higgs boson (A(0)) produced in radiative decays of an Υ(2S) or Υ(3S) meson, Υ→γA(0). The data have been recorded by the BABAR experiment at the Υ(3S) and Υ(2S) center-of-mass energies and include (121.3±1.2)×10(6) Υ(3S) and (98.3±0.9)×10(6) Υ(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Υ(nS)→γA(0))B(A(0)→hadrons) (n=2 or 3) that range from 1×10(-6) for an A(0) mass of 0.3 GeV/c(2) to 8×10(-5) at 7 GeV/c(2).     

Search for the standard model Higgs boson in the H→WW→lνq'q decay channel

We present a search for the standard model Higgs boson (H) in pp collisions at sqrt(s)=1.96 TeV in events containing a charged lepton (?), missing transverse energy, and at least two jets, using 5.4 fb(-1) of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primarily to Higgs bosons produced through the fusion of two gluons or two electroweak bosons, with subsequent decay H→WW→?νq'q, where ? is an electron or muon. The search is also sensitive to contributions from other production channels, such as WH→?νbb. In the absence of a signal, we set limits at the 95% C.L. on the cross section for H production σ(pp→H+X) in these final states. For a mass of M(H)=160 GeV, the limit is a factor of 3.9 larger than the cross section in the standard model and consistent with an a priori expected sensitivity of 5.0.     

Study of conversion decays φ→ηe+e− and η→γe+e− in the experiment with SND detector at VEPP-2M collider

The conversion decays φ→ηe⁺e⁻ and η→γe⁺e⁻ were studied by the SND detector using φ-meson production in e⁺e⁻-annihilation at VEPP-2M collider. The branching ratios of these decays were measured: Br(φ→ηe⁺e⁻)=(1.19±0.19±0.07)×10⁻⁴ and Br(η→γe⁺e⁻)=(5.15±0.62±0.39)×10⁻³. The e⁺e⁻-pair mass spectra and transition form factors were also studied.     

Possibility of distinguishing the contribution of neutral weak currents in e+e− → μ−μ+ experiments with transverse-polarized clashing beams

The process e⁺+e^{– –}+ ⁺ is studied on the basis of several models: the Weinberg- Salam model, the Lee-Prentki-Zumino model, the vector model, the X model, and under the assumption of a V-A structure of the neutral weak currents. Arbitrary polarizations of all the particles are taken into account simultaneously. Polarization effects are analyzed in detail for the case of transverse-polarized clashing beams, and various possibilities for distinguishing the contribution of neutral weak currents are identified. This possibility is very important not only for obtaining information about the structure of these currents but also for experimentally determining the sign of the weak-interaction constant. Calculations show that the neutral weak currents lead to significant polarization effects at attainable energies. These effects are very sensitive to the model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 22–27, April, 1978.The authors thank A. A. Sokolov for interest and a useful discussion.     

The form factors of the decays π− → e−¯veγ and K− → e−¯veγ

In the special type of the quark model we obtain the ratio=h _A/h_V of the axial (h_A) and vector (h_V) form factors for the decays ^– e^– ¯v_e and K^– e^–¯v_e different from unity. The low-energy theorem, relating the electric polarizability of the charged pion with the ratio, is analyzed. It is shown that < 1 corresponds to , calculated by accounting the contribution of the scalar meson(700) into the amplitude of the Compton effect on the pion. In the absence of the(700) contribution we have=1.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday.     

Determination of the CP properties of the Higgs boson from data on tau-lepton-decay products in the process e + e − → τ + τ − ν \bar \nu

The process e ⁺ e ^? → τ ⁺ τ ^? v $ \bar \nu $ , which is highly sensitive to anomalous Hττ interaction, is investigated within a model involving a new pseudoscalar Higgs boson. It is shown that the problem of separating the contributions of the scalar and pseudoscalar states of the Higgs boson can be solved via taking into account the polarizations of final-state particles. The inclusion of cascade tau-lepton decays makes it possible to determine reliably the CP state of the Higgs boson and to pinpoint the magnitude and sign of respective coupling constants.     

Vector boson pair production in e−e− collisions with polarized beams

The W-boson pair production in e⁻e⁻ collisions with polarized beams is investigated. The helicity amplitudes are derived for general couplings and the conditions for a good high-energy behaviour of the cross-section are given. The results are applied to the heavy vector boson production in the context of the left-right symmetric model. The Ward identities and the equivalence theorem are also discussed.     

Possibility of distinguishing the effect of neutral weak currents in e+e− → μ−μ+ experiments with longitudinally polarized clashing beams

The process e⁺e^{– – +} for the case of longitudinal polarization of the initial and final particles is studied on the basis of several models: the Weinberg-Salam model, the Lee-Prentki-Zumino model, the vector model, the X model, and under the assumption of a V-A structure of the neutral weak currents. Polarization effects tn the differential and total cross sections for this process are analyzed in detail, and various possibilities for distinguishing the contribution of neutral weak currents are found. Calculations show that neutral weak currents lead to appreciable polarization effects at attainable energies and that these effects are very sensitive to the model. It is important to note that an experimental study of these effects can yield valuable information on not only the structure of the neutral weak currents but also the sign of the weak-interaction constant.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 31–36, April, 1978.The authors thank A. A. Sokolov for a useful discussion and for interest in this work.     

Zum Zerfallπ→e+ν+γ

The radiative decay of the chargedπ-mesonπ→e+ν+γ is calculated using dispersion relation techniques. It is assumed that the weak interaction producing the decay has a V-A structure. The decay through the vector variant has been reinvestigated and found to be different from the result ofVaks andIoffe. The theoretical prediction of this paper is in agreement with a preliminary experiment recently performed at CERN.     

Search for the standard model Higgs boson in the decay channel H→ZZ→4ℓ in pp collisions at √s=7 TeV

A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110100 GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134-158 GeV, 180-305 GeV, and 340-465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.     

Is there a puzzle in the π0→e + e − decay?

We show the importance of precise experimental cuts in π⁰→e ⁺ e ^? decay measurements. Similar cuts have little effect in η(K _L ⁰ )→μ⁺μ^? decays.