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1.
《Physics letters. [Part B]》1987,188(1):159-162
In theories with an extra U(1) gauge boson (Z2) at low energy, W boson pairs may be produced copiously by the process e+e− → Z2 → W+W−, at the Z2 resonance. We calculate the cross section for this process, and find that it could be 1 to 2 orders of magnitude bigger than the conventional nonresonant process e+e− → W+W− via γ, Z and ν exchanges. 相似文献
2.
Measurements of e+e? → e+e? at 2.8 GeV are reported and interpreted in terms of limits for the mass and coupling of a possible scalar boson of the type introduced in recent renormalizable models of weak interactions. In particular, in the Georgi-Glashow scheme of leptons we find that the scalar boson mass must be larger than 10 GeV for an mW = 10 GeV (mW mass of the W-boson) and of 6.5 GeV for mW = 15 GeV. Alternatively its coupling is extremely weak. 相似文献
3.
Using the technique of helicity amplitudes, the electromagnetic process e
+
e
− → μ+μ− is theoretically investigated in the one-photon approximation. The structure of the triplet states of the final (μ+μ−) system is analyzed. It is shown that in the case of unpolarized electron and positron the finalmuons are also unpolarized,
but their spins are strongly correlated. Explicit expressions for the components of the correlation tensor of the final (μ+μ−) system are derived. The formula for the angular correlation at the decays of final muons μ+ and μ−, produced in the process e
+
e
− → μ+μ−, is obtained. It is demonstrated that spin correlations of muons in the process of electron-positron pair annihilation have
the purely quantum character, since one of the incoherence inequalities for the correlation-tensor components is always violated.
The additional contribution of the weak interaction of lepton neutral currents through the virtual Z
0 boson is considered; it is established that, taking into account the weak interaction, the qualitative character of the muon
spin correlations does not change.
The text was submitted by the authors in English. 相似文献
4.
Using the technique of helicity amplitudes, the electromagnetic process e
+
e
− → μ+μ− is theoretically investigated in the one-photon approximation. The structure of the triplet states of the final (μ+μ−) system is analyzed. It is shown that in the case of unpolarized electron and positron the final muons are also unpolarized,
but their spins are strongly correlated. Explicit expressions for the components of the correlation tensor of the final (μ+μ−) system are derived. The formula for the angular correlation at the decays of final muons μ+ and μ−, produced in the process e
+
e
− → μ+μ−, is obtained. It is demonstrated that spin correlations of muons in the process of electron-positron pair annihilation have
the purely quantum character, since one of the incoherence inequalities for the correlation tensor components is always violated.
The additional contribution of the weak interaction of lepton neutral currents through the virtual Z
0 boson is considered; it is established that, taking into account the weak interaction, the qualitative character of the muon
spin correlations does not change. 相似文献
5.
P. A. Éminov K. V. Zhukovskii K. G. Levchenko 《Journal of Experimental and Theoretical Physics》1998,86(6):1083-1089
The probabilities of the associated production of a Higgs boson with a Z boson by a charged lepton in the field of a plane electromagnetic wave of arbitrary intensity and in a constant crossed field
are obtained. The behavior of the cross section of the process as a function of the particle energies and the external field
intensity is investigated for various values of the Higgs boson mass. It is shown that there is a logarithmic increase in
the photoproduction cross section at superhigh energies up to a value significantly exceeding the cross section of the reaction
e
++e
−→Z+H, which is presently regarded as the most probable channel for the production of Higgs bosons.
Zh. éksp. Teor. Fiz. 113, 1979–1990 (June 1998) 相似文献
6.
A. Gay 《The European Physical Journal C - Particles and Fields》2007,49(2):489-497
Understanding the mechanism of electroweak symmetry breaking and the origin of boson and fermion masses is among the most
pressing questions raised in contemporary particle physics. If these issues involve one (several) Higgs boson(s), a precise
measurement of all its (their) properties will be of prime importance. Among those, the Higgs coupling to matter fermions
(the Yukawa coupling). At a linear collider, the process e+e-→tt̄H will allow a direct measurement of the top-Higgs Yukawa coupling. We present a realistic feasibility study of the measurement
in the context of the TESLA collider. Four channels are studied and the analysis is repeated for several Higgs mass values
within the range 120–200 GeV/c
2.
PACS 13.66.Jn; 14.65.Ha; 14.80.Bn 相似文献
7.
We examine the sensitivity of eγ colliders (based on e
+
e
− linear colliders of c.m. energy 500 GeV) to the anomalous couplings of the Higgs to W-boson via the process e
−
γ → νWH. This has the advantage over e
+
e
− collider in being able to dissociate WWH vertex from ZZH. We are able to construct several dynamical variables which may be used to constrain the various couplings in the WWH vertex.
相似文献
8.
Recent results from the LEP collider at CERN are presented: on the identification of e
+
e
− → W
+
W
− and the determination of the W mass and width and limits on its anomalous couplings; the search for the Standard Model and non-minimal Higgs; search for
SUSY and other new particles. Fits to all electroweak data leading to predictions of the Higgs mass within the Standard Model
are presented. 相似文献
9.
M. N. Achasov K. I. Beloborodov A. V. Berdyugin A. G. Bogdanchikov A. V. Bozhenok A. D. Bukin D. A. Bukin T. V. Dimova V. P. Druzhinin V. B. Golubev A. A. Korol S. V. Koshuba E. V. Pakhtusova S. I. Serednyakov Yu. M. Shatunov V. A. Sidorov Z. K. Silagadze A. N. Skrinsky Yu. A. Tikhonov A. V. Vasiljev 《Journal of Experimental and Theoretical Physics》2006,103(3):380-384
The corrected cross section of the e
+
e
− → π+π− process measured in the spherical neutral detector experiment at the VEPP-2M e
+
e
− collider is presented. The update is necessary due to a flaw in the e
+
e
− → π+π− and e
+
e
− → μ+μ− Monte Carlo event generators used previously in data analysis.
The text was submitted by the authors in English. 相似文献
10.
The production of electron-positron pairs by a photon propagating in a thermal bath in both zero and strong (B ≫ 4.41 × 1013 G) magnetic fields has been considered. The mean free path has been calculated for the high-energy photon propagating through
a thermodynamically equilibrium photon gas along the magnetic field lines so that the γ → e
−
e
+ decay is kinematically forbidden. It has been shown that the strong magnetic field suppresses the probability of the γγ′
→ e
−
e
+ process. The analyzed process can be useful for analysis of possible mechanisms of the generation of the e
−
e
+ plasma in the regions of the polar caps of magnetars. 相似文献
11.
The LEP2 data on e
+
e
− → e
+
e
−, μ+μ−, and τ
+
τ
− processes are fitted to estimate possible signals of the Abelian Z′ boson. In the many-parametric fits, four independent parameters must be fitted if the derived already low-energy relations
between the Z′ couplings to the standard-model fermions are taken into consideration. No signals are found for the complete LEP2 data set
for these processes. In the fit of the backward bins, the hint at the 1.25σ C.L. is detected. The Z′ couplings to the vector and axial-vector lepton currents are constrained. Comparisons with the one-parameter fits are performed.
The text was submitted by the authors in English. 相似文献
12.
C. Ruwiedel M. Schumacher N. Wermes 《The European Physical Journal C - Particles and Fields》2007,51(2):385-414
The prospects for the measurement of the tensor structure of the vertex between a standard model Higgs boson and two weak
gauge bosons using the distribution of the azimuthal angles between the two tagging jets in the weak boson fusion channel
are studied in a Monte Carlo analysis using the fast simulation of the ATLAS detector. The decay channels H→τ+τ-→ll+4ν, H→τ+τ-→lh+3ν at mH=120 GeV and H→W+W-→llνν at mH=160 GeV are used in the analysis. For a standard model Higgs boson it is found that purely anomalous couplings are expected
to be excluded at a confidence level corresponding to 2σ or more at mH=120 GeV and more than 5σ at mH=160 GeV from 30 fb-1 of data. With a value of 1 roughly reproducing the standard model cross section for a purely anomalous coupling, the standard
deviation in a measurement of a contribution of a CP even anomalous coupling in addition to the standard model coupling is
estimated to be 0.20 at mH=120 GeV and 0.09 at mH=160 GeV. 相似文献
13.
Karol?Ko?odziej Szymon?Szczypiński 《The European Physical Journal C - Particles and Fields》2009,64(4):645-651
We present results for the lowest order cross sections, calculated with the complete set of standard model Feynman diagrams,
of all possible detection channels of the associated production of the top quark pair and the light Higgs boson, which may
be used for determination of the top–Higgs Yukawa coupling at the future e
+
e
− linear collider. We show that, for typical particle identification cuts, the background contributions are large. In particular,
the QCD background contributions are much bigger than could be expected when taking into account a possibly low virtuality
of exchanged gluons. Moreover, we include the initial state radiation effects and discuss the dependence of the cross sections
on the Higgs boson and top quark masses. 相似文献
14.
Z. Hioki 《Zeitschrift fur Physik C Particles and Fields》1987,35(1):113-116
I discuss the determination ofW ± boson mass by the total cross-section ofe + e ?→W+W? process and its relation to tests of the electroweak higher order effects. In order to get rid of the confusion in recent theoretical arguments on this subjects, I arrange and clarify how to develop analysis once the corresponding experimental data become available. 相似文献
15.
Detailed results of an experiment, looking for a short-lived neutral particle decaying by ane
+
e
− pair in the decay of the 3.68 MeV (3/2) state in13C, whose decay is predominantly M1, are presented. An upper limit of 7 × 10−5 has been placed on the branching ratio for decay through such a particle with a mass in the range 1.7 to 1.9 MeV/c2. This leads to an upper limit of 10−6 for the coupling of such a particle to nucleons. Such a limit rules out the explanation of thee
+ ande
− peaks recently observed in heavy ion collisions, as due to the decay of a neutral particle. 相似文献
16.
A new jet algorithm based on the k-means clustering for the reconstruction of heavy states from jets
S. Chekanov 《The European Physical Journal C - Particles and Fields》2006,47(3):611-616
A jet algorithm based on the k-means clustering procedure is proposed which can be used for the invariant-mass reconstruction
of heavy states decaying to hadronic jets. The proposed algorithm was tested by reconstructing e+e-→tt̄→6 jets and e+e-→W+W-→4 jets processes at
using a Monte Carlo simulation. It was shown that the algorithm has a reconstruction efficiency similar to traditional jet-finding
algorithms, and leads to 25% and 40% improvement of the top-quark and W mass resolution, respectively, compared to the kT (Durham) algorithm. In addition, it is expected that the peak positions measured with the new algorithm have smaller systematical
uncertainty. 相似文献
17.
We show how a measurement of the process pp→tt̄H0+X at the Large Hadron Collider (LHC) and a measurement of the Higgs boson branching ratios BR(H0→bb̄) and BR(H0→W+W-) at a future linear electron positron collider (ILC) can be combined to extract a value of the top quark Yukawa coupling
in a model-independent way. We find that for masses with 120 GeV/c2<mH<200 GeV/c2 a measurement precision of 15% including systematic uncertainties can be achieved for integrated luminosities of 300 fb-1 at the LHC and 500 fb-1 at the ILC at a centre-of-mass energy of 350 GeV. 相似文献
18.
The main purpose of this work is to study the three weak boson vertex. We give explicit formulae for all polarization amplitudes of the processese + e ? →W + W ? ande + e ? →ZZ, with arbitrary couplings between the various intermediate vector bosons. Using these expressions we discuss possible signatures ofC, P andT violation in the three vector boson coupling, as well as the effects of anomalous magnetic dipole and electric quadrupole moments ofW ±. The amplitudes for the above processes in any SU(2) × U(1) and SU(2)L × SU(2)R × U(1) gauge theory are also given, while the special case of the Weinberg-Salam model is studied in detail. 相似文献
19.
Saurabh D Rindani 《Pramana》1995,45(Z1):263-276
The prospects of experimental detection ofCP violation ate
+
e
− and
colliders are reviewed. After a general discussion on the quantities which can measureCP violation and on the implications of theCPT theorem, various possibilities of measuringCP violation arising outside the standard model are taken up.CP violation in leptonic processes, especially polarization effects ine
+
e
−→l
+
l
− are discussed next.CP violation in
andW
+
W
− production and decay is also described. 相似文献
20.
G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》2006,45(2):307-335
The mass and width of the W boson are measured using e+e– → W+W– events from the data sample collected by the OPAL experiment at LEP at centre-of-mass energies between 170 GeV and 209 GeV.
The mass (mW) and width (ΓW) are determined using direct reconstruction of the kinematics of W+W– →
and W+W– →
events. When combined with previous OPAL measurements using W+W– →
events and the dependence on of the WW production cross-section at threshold, the results are determined to be
where the first error is statistical, the second systematic and the third due to uncertainties in the value of the LEP beam
energy. By measuring in the channel using several different determinations of the direction of jets with differing sensitivities
to soft particles, a limit is also obtained on possible final-state interactions due to colour reconnection effects inW+W– →
events. The consistency of the results for the W mass and width with those inferred from other electroweak parameters provides
an important test of the Standard Model of electroweak interactions.
Arrival of the final proofs: 28 November 2005
This paper is dedicated to the memory of Steve O'Neale 相似文献