434 research outputs found
CP violation and the CKM matrix
Our knowledge of quark-flavor physics and CP violation increased tremendously
over the past five years. It is confirmed that the Standard Model correctly
describes the dominant parts of the observed CP-violating and flavor-changing
phenomena. Not only does CP violation provide some of the most precise
constraints on the flavor sector, but several measurements performed at the
B-factories achieved much better precision than had been expected. We review
the present status of the Cabibbo-Kobayashi-Maskawa matrix and CP violation,
recollect the relevant experimental and theoretical inputs, display the results
from the global CKM fit, and discuss their implications for the Standard Model
and some of its extensions.Comment: 61 pages, 11 figures; review article to be published in Ann. Rev. of
Nucl. and Part. Scienc
Flavour Physics and CP Violation in the Standard Model and Beyond
We present the invited lectures given at the Third IDPASC School which took
place in Santiago de Compostela in January 2013. The students attending the
school had very different backgrounds, some of them were doing their Ph.D. in
experimental particle physics, others in theory. As a result, and in order to
make the lectures useful for most of the students, we focused on basic topics
of broad interest, avoiding the more technical aspects of Flavour Physics and
CP Violation. We make a brief review of the Standard Model, paying special
attention to the generation of fermion masses and mixing, as well as to CP
violation. We describe some of the simplest extensions of the SM, emphasising
novel flavour aspects which arise in their framework.Comment: Invited talk at the Third IDPASC School 2013, January 21st - February
2nd 2013, Santiago de Compostela, Galiza, Spain; 36 pages, 8 figures, 2
tables; version with few misprints correcte
Universality of Strength of Yukawa Couplings, Quark Singlets and Strength of CP Violation
We analyse the strength of CP violation in an extension of the standard model
with an extra vector-like singlet quark, in the framework of the
hypothesis of universality of strength of Yukawa couplings connecting standard
quarks. We show that the correct pattern of quark masses and mixing can be
obtained, including the observed strength of CP violation.Comment: 9 pages, no figure
Geometrical CP violation in multi-Higgs models
We introduce several methods to obtain calculable phases with geometrical
values that are independent of arbitrary parameters in the scalar potential.
These phases depend on the number of scalars and on the order of the discrete
non-Abelian group considered. Using these methods we present new geometrical CP
violation candidates with vacuum expectation values that must violate CP (the
transformation that would make them CP conserving is not a symmetry of the
potential). We also extend to non-renormalisable potentials the proof that more
than two scalars are needed to obtain these geometrical CP violation
candidates.Comment: 8 pages, 2 figures. v2: table added, accepted by JHE
Triple Higgs coupling in the most general 2HDM at SM-like scenario
We consider the triple Higgs coupling for h(125) Higgs boson within the most general 2HDM. At moderate values of parameters of model, allowing by modern data, noticeable deviation of this coupling from its SM value is improbable. This deviation can be sizable only if some measurable parameters of the model are exotic
Bilateral versus ipsilesional cortico-subcortical activity patterns in stroke show hemispheric dependence
Background Understanding of interhemispheric interactions in stroke patients during motor control is an important clinical neuroscience quest that may provide important clues for neurorehabilitation. In stroke patients, bilateral overactivation in both hemispheres has been interpreted as a poor prognostic indicator of functional recovery. In contrast, ipsilesional patterns have been linked with better motor outcomes. Aim We investigated the pathophysiology of hemispheric interactions during limb movement without and with contralateral restraint, to mimic the effects of constraint-induced movement therapy. We used neuroimaging to probe brain activity with such a movement-dependent interhemispheric modulation paradigm. Methods We used an fMRI block design during which the plegic/paretic upper limb was recruited/mobilized to perform unilateral arm elevation, as a function of presence versus absence of contralateral limb restriction ( n = 20, with balanced left/right lesion sites). Results Analysis of 10 right-hemispheric stroke participants yielded bilateral sensorimotor cortex activation in all movement phases in contrast with the unilateral dominance seen in the 10 left-hemispheric stroke participants. Superimposition of contralateral restriction led to a prominent shift from activation to deactivation response patterns, in particular in cortical and basal ganglia motor areas in right-hemispheric stroke. Left-hemispheric stroke was in general characterized by reduced activation patterns, even in the absence of restriction, which induced additional cortical silencing. Conclusion The observed hemispheric-dependent activation/deactivation shifts are novel and these pathophysiological observations suggest short-term neuroplasticity that may be useful for hemisphere-tailored neurorehabilitation.info:eu-repo/semantics/publishedVersio
Two-Higgs Leptonic Minimal Flavour Violation
We construct extensions of the Standard Model with two Higgs doublets, where
there are flavour changing neutral currents both in the quark and leptonic
sectors, with their strength fixed by the fermion mixing matrices and
. These models are an extension to the leptonic sector of the class
of models previously considered by Branco, Grimus and Lavoura, for the quark
sector. We consider both the cases of Dirac and Majorana neutrinos and identify
the minimal discrete symmetry required in order to implement the models in a
natural way.Comment: 25 pages. No figure
CP properties of symmetry-constrained two-Higgs-doublet models
The two-Higgs-doublet model can be constrained by imposing Higgs-family
symmetries and/or generalized CP symmetries. It is known that there are only
six independent classes of such symmetry-constrained models. We study the CP
properties of all cases in the bilinear formalism. An exact symmetry implies CP
conservation. We show that soft breaking of the symmetry can lead to
spontaneous CP violation (CPV) in three of the classes.Comment: 14 pages, 2 tables, revised version adapted to the journal
publicatio
An upper bound on the Kaon B-parameter and Re(epsilon_K)
New precise data in B physics and theoretical developments in K physics lead
us to reconsider the weak K^0-\bar{K}^0 transition from a large-N_c viewpoint,
N_c being the number of colors. In this framework, we infer an upper limit on
\hat{B}_K and the Kaon indirect CP violation.Comment: 11 pages, 4 figures. V2 : Minor corrections, final version accepted
for publication in JHE
- …