26,786 research outputs found
A light complex scalar for the electron and muon anomalous magnetic moments
The anomalous magnetic moments of the electron and the muon are interesting
observables, since they can be measured with great precision and their values
can be computed with excellent accuracy within the Standard Model (SM). The
current experimental measurement of this quantities show a deviation of a few
standard deviations with respect to the SM prediction, which may be a hint of
new physics. The fact that the electron and the muon masses differ by two
orders of magnitude and the deviations have opposite signs makes it difficult
to find a common origin of these anomalies. In this work we introduce a complex
singlet scalar charged under a Peccei-Quinn-like (PQ) global symmetry together
with the electron transforming chirally under the same symmetry. In this
realization, the CP-odd scalar couples to electron only, while the CP-even part
can couple to muons and electrons simultaneously. In addition, the CP-odd
scalar can naturally be much lighter than the CP-even scalar, as a
pseudo-Goldstone boson of the PQ-like symmetry, leading to an explanation of
the suppression of the electron anomalous magnetic moment with respect to the
SM prediction due to the CP-odd Higgs effect dominance, as well as an
enhancement of the muon one induced by the CP-even component.Comment: 31 pages, 3 figures and 3 tables. v2: version matched to JHE
Microcausality of spin-induced noncommutative theories
In this brief report, the microcausility of quantum field theory on
spin-induced noncom- mutative spacetime is discussed. It is found that for
spacelike seperation the microcausality is not obeyed by the theory generally.
It means that Lorentz covariance can not guaran- tee microcausality in quantum
field thoery. We also give some comments about quantum field thoeries on such
noncommutative spacetime and the relations between noncommutative spacetime and
causality.Comment: 9 pages, no figur
The k-junction motif in RNA structure
The k-junction is a structural motif in RNA comprising a three-way helical junction based upon kink turn (k-turn) architecture. A computer program written to examine relative helical orientation identified the three-way junction of the Arabidopsis TPP riboswitch as an elaborated k-turn. The Escherichia coli TPP riboswitch contains a related k-junction, and analysis of >11 000 sequences shows that the structure is common to these riboswitches. The k-junction exhibits all the key features of an N1-class k-turn, including the standard cross-strand hydrogen bonds. The third helix of the junction is coaxially aligned with the C (canonical) helix, while the k-turn loop forms the turn into the NC (non-canonical) helix. Analysis of ligand binding by ITC and global folding by gel electrophoresis demonstrates the importance of the k-turn nucleotides. Clearly the basic elements of k-turn structure are structurally well suited to generate a three-way helical junction, retaining all the key features and interactions of the k-turn
Sensitivity analysis and experimental design of a stiff signal transduction pathway model
Sensitivity analysis is normally used to analyze how sensitive a system is with respect to the change of parameters or initial conditions and is perhaps best known in systems biology via the formalism of metabolic control analysis [1, 2]. The nuclear factor B (NF-B) signalling pathway is an important cellular signalling pathway, of which protein phosphorylation is a major factor controlling the activation of further downstream events. The NF-κB proteins regulate numerous genes that play important roles in inter- and intra-cellular signalling, cellular stress responses, cell growth, survival, and apoptosis. As such, its specificity and its role in the temporal control of gene expression are of crucial physiological interest
A Light Higgs at the LHC and the B-Anomalies
After the Higgs discovery, the LHC has been looking for new resonances,
decaying into pairs of Standard Model (SM) particles. Recently, the CMS
experiment observed an excess in the di-photon channel, with a di-photon
invariant mass of about 96~GeV. This mass range is similar to the one of an
excess observed in the search for the associated production of Higgs bosons
with the neutral gauge boson at LEP, with the Higgs bosons decaying to
bottom quark pairs. On the other hand, the LHCb experiment observed a
discrepancy with respect to the SM expectations of the ratio of the decay of
-mesons to -mesons and a pair of leptons, . This observation provides a hint of the
violation of lepton-flavor universality in the charged lepton sector and may be
explained by the existence of a vector boson originating form a symmetry and heavy quarks that mix with the left-handed down quarks.
Since the coupling to heavy quarks could lead to sizable Higgs di-photon rates
in the gluon fusion channel, in this article we propose a common origin of
these anomalies identifying a Higgs associated with the breakdown of the
symmetry and at the same time responsible to the quark
mixing, with the one observed at the LHC. We also discuss the constraints on
the identification of the same Higgs with the one associated with the bottom
quark pair excess observed at LEP.Comment: 34 pages, 5 figures, 3 tables. v2: 1 figure added, motivation
clarified, version matched to JHE
The unified Skyrmion profiles and Static Properties of Nucleons
An unified approximated solution for symmetric Skyrmions was proposed for the
SU(2) Skyrme model for baryon numbers up to 8,which take the hybrid form of a
kink-like solution and that given by the instanton method. The Skyrmion
profiles are examined by computing lowest soliton energy as well as the static
properties of nucleons within the framework of collective quantization, with a
good agreement with the exact numeric results. The comparisons with the
previous computations as well as the experimental data are also given.Comment: 6 pages, 3 figures, 3 tables, Created by LaTex Syste
Relaxed 2-D Principal Component Analysis by Norm for Face Recognition
A relaxed two dimensional principal component analysis (R2DPCA) approach is
proposed for face recognition. Different to the 2DPCA, 2DPCA- and G2DPCA,
the R2DPCA utilizes the label information (if known) of training samples to
calculate a relaxation vector and presents a weight to each subset of training
data. A new relaxed scatter matrix is defined and the computed projection axes
are able to increase the accuracy of face recognition. The optimal -norms
are selected in a reasonable range. Numerical experiments on practical face
databased indicate that the R2DPCA has high generalization ability and can
achieve a higher recognition rate than state-of-the-art methods.Comment: 19 pages, 11 figure
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