共查询到20条相似文献,搜索用时 140 毫秒
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This review considers important properties of the top-quark. The top-quark decays before hadronization, and the spin information
is directly transferred to the decay products. Therefore the structure of the weak interaction is investigated by measuring
the helicity fractions, f, of the W boson—the top-quark decay product. Other investigations: search for the presence of V+A
interaction, search for exotic top-quark charge — 4/3 and for t[`(t)]t\bar t — resonances—all of them, so far, were not found in the experiments — testifies against of going out of the Standard Model. 相似文献
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Alexei Grinbaum 《Foundations of Physics》2012,42(5):615-631
Fine-tuning arguments are a frequent find in the literature on quantum field theory. They are based on naturalness—an aesthetic
criterion that was given a precise definition in the debates on the Higgs mechanism. We follow the history of such definitions
and of their application at the scale of electroweak symmetry breaking. They give rise to a special interpretation of probability,
which we call Gedankenfrequency. Finally, we show that the argument from naturalness has been extended to comparing different
models of the physics beyond the Standard Model and that naturalness in this case can at best be understood a socio-historic
heuristic. 相似文献
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H. W. Wilschut U. Dammalapati D. J. van der Hoek K. Jungmann W. Kruithof C. J. G. Onderwater B. Santra P. D. Shidling L. Willmann 《Pramana》2010,75(1):163-170
One of the greatest successes of the Standard Model of particle physics is the explanation of time-reversal violation (TRV)
in heavy mesons. It also implies that TRV is immeasurably small in normal nuclear matter. However, unifying models beyond
the Standard Model predict TRV to be within reach of measurement in nuclei and atoms, thus opening an important window to
search for new physics. We will discuss two complementary experiments sensitive to TRV: Correlations in the β-decay of 21Na and the search for an electric dipole moment (EDM) in radium. 相似文献
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E. Benedetto 《International Journal of Theoretical Physics》2009,48(6):1603-1621
Einstein’s gravitational theory gave rise to a new conception of the Universe and Cosmology has been enclosed in the realm
of Science and not only of Philosophy as before the Einstein work. Despite this, the presence of the Big Bang singularity,
flatness and horizon problems led to the statement that Standard Cosmological Model, based on General Relativity and Standard
Model of particle physics, is inadequate to describe the Universe in extreme regimes. Due to this facts, alternative gravitational
theories and alternative approaches to cosmology have been proposed during the years. One of the most fruitful approach has
been that of Projective Relativity and, in this paper, we analyze the developments of this theory. Projective Relativity,
initially proposed by Fantappié and subsequently developed by Arcidiacono, has been recently revisited by prof. Ignazio Licata
and other authors. The cosmological consequences of such extension appear relevant. In the following, we analyze the effects
of the group approach on the metrics and on the dynamics and we will consider its properties in connection with varying speed
of light. 相似文献
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V. P. Neznamov 《Physics of Particles and Nuclei》2012,43(1):36-41
The Standard Model with massive fermions is formulated in the isotopic Foldy-Wouthuysen representation. SU(1) × U(1) — invariance of the theory in this representation is independent of whether fermions possess mass or not, and, consequently,
it is not necessary to introduce interactions between Higgs bosons and fermions. The study discusses a possible relation between
spontaneous breaking of parity in the isotopic Foldy-Wouthuysen representation and the composition of elementary particles
of “dark matter”. 相似文献
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It is well known that the study of flavour physics and CP violation is very important to critically test the Standard Model
and to look for possible signature of new physics beyond it. The observation of CP violation in kaon system in 1964 has ignited
a lot of experimental and theoretical efforts to understand its origin and to look for CP violation effects in other systems
besides the neutral kaons. The two B-factories BABAR and BELLE, along with other experiments, in the last decade or so made studies in flavour physics and CP
violation a very interesting one. In this article we discuss the status and prospectives of the flavour physics associated
with the strange, charm and bottom sectors of the Standard Model. The important results in kaon sector will be briefly discussed.
Recently, mixing in the charm system has been observed, which was being pursued for quite some time without any success. The
smallness of the mixing parameters in the charm system is due to the hierarchical structure of the CKM matrix. Interestingly,
so far we have not found CP violation in the charm system but in the future, with more dedicated experiments at charm threshold,
the situation could change. Many interesting observations have been made in the case of bottom mesons and some of them show
some kind of deviations from that of the Standard Model expectations which are mainly associated with the b → s flavour changing neutral current transitions. It is long believed that the B
s
system could be the harbinger of new physics since it is a system in which both bottom and strange quarks are the constituents.
Recently, D0 and CDF announced their result for the B
s
mixing which is claimed to be the first possible new physics signature in the flavour sector. We plan to touch upon all important
issues pointing out both theoretical and experimental developments and future prospects in this review article. 相似文献
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P. Abreu et al. 《The European Physical Journal C - Particles and Fields》1999,11(3):383-407
The data collected with the DELPHI detector at centre-of-mass energies between 130 and 172 GeV, during LEP operation in 1995
and 1996, have been used to determine the hadronic and leptonic cross-sections and leptonic forward–backward asymmetries.
In addition, the cross-section ratios and forward–backward asymmetries for flavour-tagged samples of light (uds), c and b
quarks have been measured. No significant deviations from the Standard Model expectations are found. The results are interpreted
by performing S-matrix fits to these data and to the data collected previously at the energies near the resonance peak (88-93 GeV). The results are also interpreted in terms of physics beyond the Standard Model: contact interactions,
R-parity violating SUSY particle exchange and of possible Z bosons.
Received: 9 February 1999 / Published online: 14 October 1999 相似文献
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D G Hitlin 《Pramana》2006,67(5):743-753
Heavy-flavor physics, in particular B and τ physics results from the B factories, currently provides strong constraints on models of physics beyond the Standard Model. A new generation of colliders,
Super B Factories, with 50 to 100 times the luminosity of existing colliders, can, in a dialog with LHC and ILC, provide unique clarification
of new physics phenomena seen at those machines. 相似文献
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J. Wouters N. Severijns J. Vanhaverbekf W. Vanderpoorten L. Vanneste 《Hyperfine Interactions》1990,59(1-4):59-75
Conclusion Since the first results continuous improvements and further developments of OLNO have been carried out; e.g. the sensitivity
has been increased by the realization of particle detection. On—line nuclear orientation has evolved to a unique technique
to study a broad range of physics topics from very fundamental interactions to applied material science. This has been proven
by the results that already have been obtained. Apart from the well established low temperature NO technique, also the development
of in—beam polarization methods is taking place. At NICOLE fine opportunities exist to work out specific and unique physics
problems. Benefit can be taken of the high production rates at ISOLDE as compared to the other OLNO systems. 相似文献
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Drell–Yan process at LHC, q[`(q)]? Z/g* ? l+l-q\bar {q}\to Z/\gamma ^\ast \to \ell ^+\ell ^-, is one of the benchmarks for confirmation of Standard Model at TeV energy scale. Since the theoretical prediction for the
rate is precise and the final state is clean as well as relatively easy to measure, the process can be studied at the LHC
even at relatively low luminosity. Importantly, the Drell–Yan process is an irreducible background to several searches of
beyond Standard Model physics and hence the rates at LHC energies need to be measured accurately. In the present study, the
methods for measurement of the Drell–Yan mass spectrum and the estimation of the cross-section have been developed for LHC
operation at the centre-of-mass energy of 10 TeV and an integrated luminosity of 100 pb − 1 in the context of CMS experiment. 相似文献
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The recently observed correlation between HiRes stereo cosmic ray events with energies E ∼ 1019 eV and BL Lacertae objects occurs at an angle that strongly suggests that the primary particles are neutral. We analyze whether
this correlation, if not a statistical fluctuation, can be explained within the Standard Model, i.e., assuming only known
particles and interactions. We have not found a plausible process that can account for these correlations. The mechanism that
comes closest—the conversion of protons into neutrons in the IR background of our Galaxy—still underproduces the required
flux of neutral particles by about two orders of magnitude. The situation is different at E ∼ 1020 eV, where the flux of cosmic rays at the Earth may contain up to a few percent of neutrons, indicating their extragalactic
sources.
The text was submitted by the authors in English. 相似文献
14.
No Heading Several works analyzing the new physics contributions from the Left-Right Symmetric Model to the CP violation phenomena in
the neutral B mesons can be found in the literature. These works exhibit interesting and experimentally sensible deviations
from the Standard Model predictions but at the expense of considering a low right scale υR around 1 TeV. However, when we stick to the more conservative estimates for υR, which say that it must be at least 107 GeV, no experimentally sensible deviations from the Standard Model appear for indirect CP violation. This estimate for υR arises when the generation of neutrino masses is considered. In spite of the fact that this scenario is much less interesting
and says nothing new about both the CP violation phenomenon and the structure of the Left-Right Symmetric Model, this possibility
must be taken into account for the sake of completeness and when considering the see-saw mechanism that provides masses to
the neutrino sector.
1 Associate researcher of the Centro Internacional de Física, Ciudad
Universitaria, Bogotá D.C., Colombia. 相似文献
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The latest results obtained from searches for particles and phenomena beyond the Standard Model (new physics) in the D0 experiment
at the Tevatron [Fermi National Accelerator Laboratory (FNAL), USA] on the basis of a statistical sample corresponding to
an accumulated luminosity of 1 to 3 fb−1 in 2008 are considered. 相似文献
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Adrian John Bevan 《Frontiers of Physics》2016,11(1):111401
Tests of discrete symmetry violation have played an important role in understanding the structure of weak interactions in the Standard Model of particle physics. Historically, these measurements have been extensively performed in experiments with large samples of K and B mesons. A high luminosity τ-charm facility presents physicists with the opportunity to comprehensively explore discrete symmetry violation and test the Standard Model using τ leptons, charm mesons, and charmed baryons. This paper discusses several possible measurements for a future τ-charm factory. 相似文献
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A. Ianni 《Progress in Particle and Nuclear Physics》2011,66(2):405-411
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Wulf Fetscher 《Zeitschrift fur Physik C Particles and Fields》1992,56(Z1):S109-S113
Muon decay, after more than fifty years of experimental and theoretical investigations, has been established as a firm basis
for the Standard Model of Electroweak Interactions. The decay products of the muon have been identified, and the Lorentz structure
of the decay interaction has been determined completely from existing experiments in a model-independent way. Together with
the completely anologous leptonic τ decays it continues to be an important and sensitive testing ground for deviations from
the Standard Model. 相似文献
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Over the last ten years interest in the physics of de Sitter space—time has been growing very fast. Besides the supposed existence
of a “de Sitterian period” in inflation theories, the observational evidence of an acceleration of the universe expansion
(interpreted as a positive cosmological constant or a “dark energy” or some form of “quintessence”) has triggered a lot of
attention in the physics community. A specific de Sitterian field called “massless minimally coupled field” (mmc) plays a
fundamental role in inflation models and in the construction of the de Sitterian gravitational field. A covariant quantization
of the mmc field, à la Krein—Gupta—Bleuler was proposed in Class. Quantum. Grav. 17, 1415 (2000). In this talk, we will review this construction and explain the relevance of such a field in the construction
of a massless spin-2 field in de Sitter space—time. 相似文献