Search results for "The Standard Model"
showing 10 items of 466 documents
Energy-independent new physics in the flavour ratios of high-energy astrophysical neutrinos
2010
We have studied the consequences of breaking the CPT symmetry in the neutrino sector, using the expected high-energy neutrino flux from distant cosmological sources such as active galaxies. For this purpose we have assumed three different hypotheses for the neutrino production model, characterised by the flavour fluxes at production phi(0)(e) : phi(0)(mu) : phi(0)(tau) = 1 : 2 : 0, 0 : 1 : 0, and 1 : 0 : 0, and studied the theoretical and experimental expectations for the muon-neutrino flux at Earth, phi(mu), and for the flavour ratios at Earth, R = phi(mu)/phi(e) and S = phi(tau)/phi(mu). CPT violation (CPTV) has been implemented by adding an energy-independent term to the standard neutrin…
CPasymmetries inBsdecays and spontaneousCPviolation
1999
We study the possible effects of new physics in $\mathrm{CP}$ asymmetries in two-body ${B}_{s}$ decays in left-right models with spontaneous $\mathrm{CP}$ violation. Considering the contributions of new $\mathrm{CP}$ phases to the ${B}_{s}$ mixing as well as to the penguin-dominated decay amplitudes we show that, with the present constraints, large deviations from the standard model predictions in $\mathrm{CP}$ asymmetries are allowed in both cases. The detection of new physics can be achieved by measuring nonzero asymmetries which are predicted to vanish in the standard model or by comparing two measurements which are predicted to be equal in the standard model. In particular, we show that…
Implications of an axino LSP for naturalness
2014
Both the naturalness of the electroweak symmetry breaking and the resolution of the strong CP problem may require a small Higgsino mass $\mu$ generated by a realization of the DFSZ axion model. Assuming the axino is the lightest supersymmetric particle, we study its implications on $\mu$ and the axion scale. Copiously produced light Higgsinos at collider (effectively only neutral NLSP pairs) eventually decay to axinos leaving prompt multi-leptons or displaced vertices which are being looked for at the LHC. We use latest LHC7+8 results to derive current limits on $\mu$ and the axion scale. Various Higgsino-axino phenomenology is illustrated by comparing with a standard case without lightest …
New Physics and Evidence for a Complex CKM
2005
We carefully analyse the present experimental evidence for a complex CKM matrix, even allowing for New Physics contributions to $\epsilon_{K}$, $a_{J/\Psi K_S}$, $\Delta M_{B_{d}}$, $\Delta M_{B_{s}}$, and the $\Delta I=1/2$ piece of $B\to\rho\rho$ and $B\to\rho\pi$. We emphasize the crucial r\^ ole played by the angle $\gamma$ in both providing irrefutable evidence for a complex CKM matrix and placing constraints on the size of NP contributions. It is shown that even if one allows for New Physics a real CKM matrix is excluded at a 99.92% C.L., and the probability for the phase $\gamma$ to be in the interval $[-170^\circ;-10^\circ]\cup [10^\circ;170^\circ]$ is 99.7%.
Rare kaon decays
1997
Abstract More and more sophisticated experiments and continuous progress in the theoretical understanding of rare kaon decays have proven how rich this field of particle physics is. This article summarizes the present situation of the phenomenology and the experiments. Prospects for the future are given and discussed. The decays are ordered from the less rare to the very rare. Recently there has been quite some progress concerning the first category of decays presented here, the radiative decays, and tests of chiral perturbation theory. The CP violating decays discussed next are complementary to the KL → 2π decays and offer additional insight into the mechanism of direct CP violation. Decay…
On the model dependence of fiducial cross-section measurements
2019
Fiducial production cross-section measurements of Standard Model processes, in principle, provide constraints on new physics scenarios via a comparison of the predicted Standard Model cross-section and the observed cross-section. This approach received significant attention in recent years, both from direct constraints on specific models and the interpretation of measurements in the view of effective field theories. A generic problem in the reinterpretation of Standard Model measurements is the corrections application of to data to account for detector effects. These corrections inherently assume the Standard Model to be valid, thus implying a model bias of the final result. In this work, …
Monochromatic neutrino beams
2005
In the last few years spectacular results have been achieved with the demonstration of non vanishing neutrino masses and flavour mixing. The ultimate goal is the understanding of the origin of these properties from new physics. In this road, the last unknown mixing [U-e3] must be determined. If it is proved to be non-zero, the possibility is open for Charge Conjugation-Parity (CP) violation in the lepton sector. This will require precision experiments with a very intense neutrino source. Here a novel method to create a monochromatic neutrino beam, an old dream for neutrino physics, is proposed based on the recent discovery of nuclei that decay fast through electron capture. Such nuclei will…
Seesaw roadmap to neutrino mass and dark matter
2018
We describe the many pathways to generate Majorana and Dirac neutrino mass through generalized dimension-5 operators a la Weinberg. The presence of new scalars beyond the Standard Model Higgs doublet implies new possible field contractions, which are required in the case of Dirac neutrinos. We also notice that, in the Dirac neutrino case, the extra symmetries needed to ensure the Dirac nature of neutrinos can also be made responsible for stability of dark matter.
Charged Kaon CP Violating Asymmetries vs
2007
We present the next-to-leading order full results in Chiral Pertubation Theory for the charged Kaon K → 3 π slope g CP violating asymmetries. We discuss the constraints that a measurement of these asymmetries would impose on the Standard Model results of e K ′ and search for new physics. We also study the kind of information that such measurement can provide on Im G 8 , Im ( e 2 G E ) and higher order weak couplings.
Electric Dipole Moments in Two-Higgs-Doublet Models
2014
Electric dipole moments are extremely sensitive probes for additional sources of CP violation in new physics models. Specifically, they have been argued in the past to exclude new CP-violating phases in two-Higgs-doublet models. Since recently models including such phases have been discussed widely, we revisit the available constraints in the presence of mechanisms which are typically invoked to evade flavour-changing neutral currents. To that aim, we start by assessing the necessary calculations on the hadronic, nuclear and atomic/molecular level, deriving expressions with conservative error estimates. Their phenomenological analysis in the context of two-Higgs-doublet models yields strong…