130,633 research outputs found
Distance between quantum field theories as a measure of Lorentz violation
No full textWe study the distance between symmetry-violating quantum field theories and the surface of symmetric theories. We use this notion to quantify how precise Lorentz symmetry is today, according to experimental data. The metric in parameter space is defined a la Zamolodchikov, from the two-point function of the Lagrangian perturbation. The distance is obtained minimizing the length of paths connecting the Lorentz-violating theory to the Lorentz surface. This definition depends on the Lagrangian used to formulate the theory, including total derivatives and the choice of coordinate frame. We eliminate such dependencies minimizing with respect to them. We derive a number of general formulas and evaluate the distance in the CPT-invariant, QED subsectors of the standard model extension and the renormalizable high-energy-Lorentz-violating standard model. We study the properties of the distance and address a number of applications
Probing the g-2 muon anomaly with the Higgs boson at a muon collider
No full textWe point out that heavy new physics contributions in leptonic dipole moments and high-energy cross sections of lepton pairs into Higgs bosons and photons are connected model-independently. In particular, we demonstrate that a muon collider, running at center-of-mass energies of several TeV, can provide a unique test of new physics in the muon through the study of high-energy processes such as . This high-energy test would be of the utmost importance to shed light on the longstanding muon anomaly as it is not affected by the hadronic and experimental uncertainties entering the current low-energy determination of the muon . Furthermore, we show that the current bound on the muon electric dipole moment can be improved by three orders of magnitude, down to
Flavour physics and flavour symmetries after the first LHC phase
No full textBased on flavour symmetries only, there are two ways to give rise to an effective description of flavour physics in the quark sector close to the CKM picture: one is based on U(3) q × U(3) u × U(3) d (or equivalent) and the other on U(2) q × U(2) u × U(2) d (or equivalent). In this context we analyze the current status of flavour physics measurements and we compare their impact, in the specific case of supersymmetry, with the direct searches of new particles at the LHC, present or foreseen. © 2014 The Author(s)
The spectral drop problem
No full textWe consider spectral optimization problems of the form
where is a given subset of the Euclidean space . Here is the first eigenvalue of the Laplace operator with Dirichlet conditions on and Neumann or Robin conditions on . This reminds the classical drop problems, where the first eigenvalue replaces the perimeter functional. We prove an existence result for general shape cost functionals and we show some qualitative properties of the optimal domains
Optimal shapes for general integral functionals
No full textWe consider shape optimization problems for general integral functionals of the calculus of variations, defined on a domain that varies over all subdomains of a given bounded domain of . We show in a rather elementary way the existence of a solution that is in general a quasi open set. Under very mild conditions we show that the optimal domain is actually open and with finite perimeter. Some counterexamples show that in general this does not occur
Local mappings on spaces of differentiable functions
No full textWe study conditions under which a functional admits an integral representation of the form
F(u,B) = \int_B f ( x,D^ku(x) ) dx
$
Singlet-like Higgs bosons at present and future colliders
No full textAbstract: The presence of extra scalar singlets is a feature of several motivated extensions of the Standard Model, and the mixing of such a singlet with the Higgs boson is allowed to be quite large by current experiments. In this paper we perform a thorough phenomeno-logical study of this possibility. We consider both direct and indirect searches, and we quantify the current constraints as well as the prospects for future hadron and lepton machines — from the forthcoming LHC run up to a futuristic 100 TeV proton-proton collider. The direct reaches are obtained extrapolating the current limits with a technique that we discuss and check with various tests. We find a strong complementarity between direct and indirect searches, with the former dominating for lower values of the singlet mass. We also find that the trilinear Higgs coupling can have sizeable deviations from its Standard Model value, a fact for which we provide an analytical understanding. The results are first presented in a general scalar singlet extension of the Standard Model, taking advantage of the very small number of parameters relevant for the phenomenology. Finally, we specify the same analysis to a few most natural models, i.e. the Next-to-Minimal Supersymmetric Standard Model, Twin Higgs and Composite Higgs
A 125 GeV composite Higgs boson versus flavour and electroweak precision tests
No full textA composite Higgs boson of 125 GeV mass, only mildly fine-tuned, requires top partners with a semi-perturbative coupling and a mass not greater than about a TAT. We analyze the strong constraints on such picture arising from flavour and electroweak precision tests in models of partial compositeness. We consider different representations for the composite fermions and compare the case of an anarchic flavour structure to models with a U(3)(3) and U(2)(3) flavour symmetry. Although non trivially, some models emerge that look capable of accommodating a 125 GeV Higgs boson with top partners in an interesting mass range for discovery at the LHC as well as associated flavour signals
Less minimal avour violation
No full textWe consider the approximate U(2)3 avour symmetry exhibited by the quark sector of the Standard Model and all its possible breaking terms appearing in the quark Yukawa couplings. Taking an Effective Field Theory point of view, we determine the current bounds on these parameters, assumed to control the breaking of avour in a generic extension of the Standard Model at a reference scale Λ. In particular, a significant bound from ε'/ε is derived, which is relevant to Minimal Flavour Violation as well. In the upquark sector, the recently observed CP violation in D → π+π-, K+K- decays might be accounted for in this generic framework, consistently with any other constraint. © 2012 SISSA
- …
