共查询到20条相似文献,搜索用时 31 毫秒
1.
《Nuclear Physics B》1988,309(2):221-258
We examine one-loop radiative corrections to e+e−→W+W− in the standard model with one Higgs doublet, concentrating on the effects of very heavy fermions. These disturb the delicate unitarity cancellation between s- and t-channel diagrams, raising the cross section even well below the fermion threshold and giving a clear experimental signature for the heavy sector. 相似文献
2.
《Physics letters. [Part B]》1988,205(4):573-575
The reaction e+e−→γW+W− has been studied at TeV energies as a possible background to Higgs production. Our results differ significantly from previous estimates and show that the ratio signal/background can be kept reasonably large. 相似文献
3.
《Physics letters. [Part B]》1999,456(1):60-67
It has been proposed recently that the scale of quantum gravity (“the string scale”) can be MS∼few TeV with n≥2 extra dimensions of size R≲mm so that, at distances greater than R, Newtonian gravity with MPl∼1018 GeV is reproduced if MPl2∼RnMSn+2. Exchange of virtual gravitons in this theory generates higher-dimensional operators involving SM fields, suppressed by powers of MS. We discuss constraints on this scenario from the contribution of these operators to the processes e+e−→W+W−, ZZ, γγ. We find that LEP2 can place a limit MS≈1 TeV from e+e−→W+W−, ZZ, γγ. 相似文献
4.
The effect of gluon bremsstrahlung in the decays of theW-bosons on the measurement of the reactione + e ?→W + W ?→ hadrons is discussed. From simulation studies we find a substantial fraction of events with high jet multiplicities. At energies of \(\sqrt s = 200\) GeV this leads to probabilities of 25% or higher to misassign a jet to aW-boson when a realistic resolution of a detector is assumed. Some implications on the measurement of the decay and production properties of theW's are discussed. 相似文献
5.
G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》2006,45(2):291-305
The effects of the final state interaction phenomenon known as colour reconnection are investigated at centre-of-mass energies
in the range
≃ 189–209 using the OPAL detector at LEP. Colour reconnection is expected to affect observables based on charged particles
in hadronic decays of . Measurements of inclusive charged particle multiplicities, and of their angular distribution with
respect to the four jet axes of the events, are used to test models of colour reconnection. The data are found to exclude
extreme scenarios of the Sj?strand-Khoze Type I () model and are compatible with other models, both with and without colour
reconnection effects. In the context of the model, the best agreement with data is obtained for a reconnection probability
of 37%. Assuming no colour reconnection, the charged particle multiplicity in hadronically decaying W bosons is measured to
be
=19.38±0.05(stat.)±0.08(syst.).
Arrival of the final proofs: 28 November 2005 相似文献
6.
G. Alexander C. Milsténe W. Hollik 《Zeitschrift fur Physik C Particles and Fields》1991,52(2):283-288
The cross section for direct neutral Higgs production in the reaction
is calculated in theE
CM energy range of 40 to 160 GeV and compared to the corresponding Electro-Weak (EW) process
. Neglecting radiation effects, a signal of the order of 10–4 to 10–3 over the EW can be expected outside theZ
0 region for the Minimal Standard Model Higgs in its decay to a
state. For
\sqrt s - M_Z $$
" align="middle" border="0">
, thes-channel Higgs formation can surpass the Bjorken Bremsstrahlung process and thus may afford at LEP 2 a realistic search method for high mass, say 100 GeV Higgs, given enough luminosity. For a non-Standard Model Higgs, in some cases, significantly higher signals are expected. The effects of initial state radiation and-machine energy resolution are evaluated and the gain in using longitudinal polarized electron beams is discussed.Supported in part by the Israel Ministry for Science and Technology 相似文献
7.
Stefano Moretti 《Zeitschrift fur Physik C Particles and Fields》1997,73(4):653-667
The complete matrix element for e + e? → bb?W+ W? is computed at tree-level within the Minimal Supersymmetric Standard Model. Rates of interest to phenomenological analyses at the Next Linear Collider are given. In particular, we study:
- ? tt? production and decay tt? →(bW +)(b?W ?)
- ? ZH production followed by Z → bb? and H → W + W?
- ? AH production followed by A→ bb? and H → W + W?
- ? hW + W? production followed by h→ bb?.
8.
9.
10.
We study quantitatively the reactions \(e^ + e^ - \to W^ + e\bar \nu _e \) ,e R ? e + and the rare decay \(Z^0 \to W^ \pm l^ \mp \mathop {\nu _e }\limits^{( - )} \) forl=e, μ and τ, as a test for anomalous γW + W ? andZ 0 W + W ? structure. If κ denotes the anomalous magnetic moment of theW-boson and ω its anomalous coupling to theZ 0, values of |ω|>2.5 and |κ|>1.5 can be ruled out at LEP and SLC rather easily. This will put constraints on composite model building. 相似文献
11.
12.
《Physics letters. [Part B]》1988,213(1):95-102
Standard model predictions for W pair production at e+e− colliders are compared to those of an effective lagrangian where the electroweak symmetry breaking occurs via a strong dynamics implying new spin-1 states. Both the differential cross section and the longitudinal asymmetry are evaluated at LEP II (√s=190 GeV) and at SLC (√s=600 GeV) energies. These quantities appear to be sensitive to specific ranges of the parameter space, with distinctive experimental signatures. 相似文献
13.
J. del Peso L. Labarga F. Barreiro 《Zeitschrift fur Physik C Particles and Fields》1989,43(2):287-300
We calculate heavy (M H 2 /s) and light (M L 2 /s) jet masses up toO(α s 2 ) in perturbative Quantum Chromodynamics (QCD). The sensitivity of these quantities to radiative corrections, quark masses, fragmentation effects as well as their infrared stability properties, are investigated and compared to those exhibited by other jet measures. A comparison with recent Mark II data is also presented. 相似文献
14.
M. Ciuchini E. Franco E. Gabrielli 《Zeitschrift fur Physik C Particles and Fields》1990,47(4):577-581
We calculate numerically the cross section for the process \(e^ + e^ - \to ve^ + Q_d \bar Q_u \) using the Weizsäcker-Williams approximation for the virtual photon. This process is a possible background for the detection of an “intermediate” Higgs via its decay into \(Q\bar Q\) pairs. The comparison with the signal allows us to conclude that actually it is not a problem for the Higgs search at high energye + e ? colliders. 相似文献
15.
The question of whether constraints on the anomalous parameters of WWγ and WWZ three-boson interactions can be deduced from an analysis of data on the reaction e + e ? → W ? e + ν that are expected to come from a future $\sqrt s = 500 - GeVe^ + e^ - $ linear collider of integrated luminosity of L=50, 100, or 500 fb? is discussed. An analysis of relevant differential distributionns reveals that, in contrast to pair W-boson production, the reaction mentioned immediately above is highly sensitive to the parameter λ Z and that the resulting constraints can be viewed as those that supplement the constraints that follow from data on e + e ?→W + W ?. For the experiment being discussed, two possible implementations of a detector are considered that correspond to the kinematical regions |cos $\left| {\cos \theta _{e^ + } } \right| \leqslant \cos 7^\circ $ and $\left| {\cos \theta _{e^ + } } \right| \leqslant \cos 1.5^\circ $ . It is indicated that the region of small positron-scattering angles is of importance for improving the sensitivity of the process. In setting constraints on the anomalous parameters, the SEWS scenario for anomalous boson coupling constants, where interactions responsible for electroweak-symmetry breaking are strongly coupled, is examined along with the case of the most general parametrization of the WWγ(Z) three-boson vertices. 相似文献
16.
We present a multiplicity distribution which is a solution to the stochastic branching equation proposed by Giovannini. This solution is more commonly known as generalized multiplicities distribution (GMD) and has already been successfully applied to bothpp andp
collisions. It assumes that shapes and energy dependence of distributions are basically determined by hard parton scattering and subsequent branching. We apply GMD to the recente
+
e
– data by Tasso Collaboration. 相似文献
17.
《Physics letters. A》1998,243(4):215-222
The features of the low-lying spectrum and the complete set of quantum numbers of each of the low-lying states of a (e+e+e−e−) system have been deduced based on symmetry. 相似文献
18.
《Physics letters. [Part B]》1988,211(4):485-488
Higgsino production in e+e− reactions is considered in the simplest model where the higgsino is the lightest supersymmetric particle. The supersymmetric version of the Wilczek mechanism seems to be the best way to detect higgsinos and photinos in the LEP energy range. 相似文献
19.
20.
We present a new class of observables which distinguish events containing two or three hadron jets from those containing a larger number. These observables, which essentially measure the coplanary of events, are calculable in QCD perturbation theory. Their use should allow the mechanism of decay to be determined. 相似文献