51 research outputs found
Studying Structure of Electroweak Corrections
Several different effects in electroweak quantum corrections are explored
separately through the latest data on the weak-boson masses. The leading-log
approximation, the improved-Born approximation and the non-decoupling top-quark
effects are studied without depending on the recent CDF data of , and the
results are given in a form independent of the Higgs mass. On the other hand,
the bosonic- and the non-decoupling Higgs effects are examined by fully taking
account of those CDF data. It is emphasized that future precision measurements
of and are considerably significant not only for further studies of
the electroweak theory at higher confidence level but also for new physics
searches beyond it.Comment: 18 page
Decoupling theorem in top productions/decays revisited : To what extent can we understand it visually?
I revisit here the decoupling theorem in top-quark productions/decays, which states that the angular distribution of any final-particle produced in those processes does not depend on any possible nonstandard top-quark decay interactions at their leading order when certain conditions are satisfied. Toward a simple, intuitive and visual understanding of this theorem, I will study to what extent we could explain why such a theorem holds without relying on any specific/detailed calculations
Non-trivial Test of Electroweak Quantum Effects
Based on recent -mass measurements, the electroweak theory is tested at
non-trivial quantum correction level, i.e., beyond the Born approximation with
instead of . We can conclude that some non-Born type
corrections must exist at more than 92 % confidence level, and the
non-decoupling top-quark corrections are required at 97 % confidence level.Comment: 7 page
Studying possible CP-violating Higgs couplings through top-quark pair productions at muon colliders
We study possible anomalous CP-violating Higgs couplings to mu mu-bar and t
t-bar fully model-independent way through top-quark pair productions at muon
colliders. Assuming additional non-standard neutral Higgs bosons, whose
couplings with top-quark and muon are expressed in the most general covariant
form, we carry out analyses of effects which they are expected to produce via
CP-violating asymmetries and also the optimal-observable (OO) procedure under
longitudinal and transverse muon polarizations. We find the measurement of the
asymmetry for longitudinal beam polarization could be useful to catch some
signal of CP violation, and an OO analysis might also be useful if we could
reduce the number of unknown parameters with a help of other experiments and if
the size of the parameters is at least O(1) ~ O(10).Comment: Final version (to appear in JHEP
Top-quark pair productions and CP-violating Higgs interactions at muon colliders
We study CP-violation effects from possible non-standard Higgs interactions in beyond-the-standard-model physics through top-quark pair productions at μμ⁻ colliders. We calculate two CP-violating asymmetries for longitudinal and transverse beam polarizations, and study their dependence on √s and mH, the additional Higgs mass. Judging from their computed absolute values, we conclude that there are more chances to find non-standard effects in analyses using AL, the longitudinal asymmetry, than in those using AT, the transverse asymmetry
Addendum to: Search for anomalous top-gluon couplings at LHC revisited
In our latest paper "Search for anomalous top-gluon couplings at LHC
revisited" in Eur. Phys. J. C65 (2010), 127-135 (arXiv:0910.3049 [hep-ph]), we
studied possible effects of nonstandard top-gluon couplings through the
chromoelectric and chromomagnetic moments of the top quark using the total
cross section of ppbar/pp --> ttbar X at Tevatron/LHC. There we pointed out
that LHC data could give a stronger constraint on those two parameters, which
would be hard to obtain from Tevatron data alone. We show here the first CMS
measurement of this cross section actually makes it possible.Comment: 5 pages, 1 figure, LaTeX2e, Final version (to appear in Eur. Phys. C
Decoupling of Anomalous Top-Quark-Decay Vertices in Angular Distribution of Secondary Particles
Angular distribution of a secondary particle from top-quark decays is studied
in a simple and general manner, paying careful attention to how relevant the
top-quark production mechanism is. The conditions that lead to the distribution
free from any possible anomalous top-quark decay interactions are specified. It
is discussed how important the approximations adopted in earlier papers are.Comment: 9 pages, Latex, Final version (to appear in Phys.Lett. B
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