Why care about (θ13,δ)(\theta_{13},\delta) degeneracy at future neutrino experiments

The presence of several clone solutions in the simultaneous measurement of ($\theta_{13},\delta$) has been widely discussed in literature. Here, after a pedagogical introduction on why these clones arise, we discuss how the clones location in the ($\theta_{13},\delta$) plane change as a function of the physical input pair ($\bar\theta_{13},\bar\delta$). We compare the clone flow of a set of possible future neutrino experiments: the CERN SuperBeam, BetaBeam and Neutrino Factory proposals. We show that the combination of these specific BetaBeam and SuperBeam could not help in solving the degeneracies. The combination of one of them with the Neutrino Factory Golden and Silver channel can, instead, be used to solve completely the eightfold degeneracy.Comment: 7 pages, 12 figures. Talk given at the XXXIXth Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 21-28 Mar 200

Sum rules for asymptotic form factors in e+e−−>W+W−e^+ e^- -> W^+ W^- scattering

At very large energies and in $SU(2)_L\otimes U(1)_Y$ gauge theories, the trilinear gauge boson vertices relevant for $e^+e^- \to W^+W^-$ scattering are related in a simple way to the gauge boson self-energies. We derive these relations, both from the requirement of perturbative unitarity and from the Ward Identities of the theory. Our discussion shows that, in general, it is never possible to neglect vector boson self-energies when computing the form factors which parametrize the $e^+ e^- \to W^+ W^-$ helicity amplitudes. The exclusion of the self-energy contributions would lead to estimates of the effects wrong by orders of magnitudes. We propose a simple way of including the self-energy contributions in an appropriate definition of the form factors.Comment: 16 pages, latex file, 2 eps figures, need epsfig.st

Higgs portal dark matter and neutrino mass and mixing with a doubly charged scalar

We consider an extension of the Standard Model involving two new scalar particles around the TeV scale: a singlet neutral scalar $\phi$, to be eventually identified as the Dark Matter candidate, plus a doubly charged $SU(2)_L$ singlet scalar, $S^{++}$, that can be the source for the non-vanishing neutrino masses and mixings. Assuming an unbroken $Z_2$ symmetry in the scalar sector, under which only the additional neutral scalar $\phi$ is odd, we write the most general (renormalizable) scalar potential. The model may be regarded as a possible extension of the conventional Higgs portal Dark Matter scenario which also accounts for neutrino mass and mixing. This framework cannot completely explain the observed positron excess. However a softening of the discrepancy observed in conventional Higgs portal framework can be obtained, especially when the scale of new physics responsible for generating neutrino masses and lepton number violating processes is around 2 TeV.Comment: 16 pages, 4 figure

Thermal and Magnetic Quantum Discord in Heisenberg models

We investigate how the quantum correlations (quantum discord) of a two-qubit one dimensional XYZ Heisenberg chain in thermal equilibrium depends on the temperature (T) of the bath and also on an external magnetic field B. We show that the behavior of the thermal quantum discord (QD) differs in many unexpected ways from the thermal entanglement. For example, we show situations where QD increases with T when entanglement decreases, cases where QD increases with T even in regions with zero entanglement, and that QD signals a quantum phase transition even at finite T. We also show that by properly tuning B or the interaction between the qubits we get non-zero QD for any T and we present a new effect not seen for entanglement, the regrowth of thermal QD.Comment: 4 pages, 5 figures, RevTex, double column; v2: published versio

Revisiting the production of ALPs at B-factories

In this paper, the production of Axion-Like Particles (ALPs) at B-factories via the process e+e− → γa is revisited. To this purpose, the relevant cross-section is computed via an effective Lagrangian with simultaneous ALP couplings to b-quarks and photons. The interplay between resonant and non-resonant contributions is shown to be relevant for experiments operating at s=mϒ(nS), with n = 1, 2, 3, while the non-resonant one dominates at ϒ(4S). These effects imply that the experimental searches performed at different quarkonia resonances are sensitive to complementary combinations of ALP couplings. To illustrate these results, constraints from existing BaBar and Belle data on ALPs decaying into invisible final states are derived, and the prospects for the Belle-II experiment are discussedThe authors acknowledge F. Anulli, D. Becirevic, S. Fajfer, A. Guerrera, C. Hearty, S.J.D. King, T. Ferben, S. Lacaprara, M. Margoni, F. Mescia, M. Passera and P. Paradisi for very useful exchanges. This project has received support by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement N◦ 674896 (ITN Elusives) and 690575 (RISE InvisiblePlus) and by the exchange of researchers project “The flavor of the invisible universe” funded by the Italian Ministry of Foreign Affairs and International Cooperation (MAECI). L.M. acknowledges partial financial support by the Spanish MINECO through the “Ram´on y Cajal” programme (RYC-2015-17173), by the Spanish “Agencia Estatal de Investigaci´on” (AEI) and the EU “Fondo Europeo de Desarrollo Regional” (FEDER) through the project FPA2016-78645-P, and through the Centro de excelencia Severo Ochoa Program under grant SEV-2016-0597. L.M. thanks the Physics and Astronomy Department ‘G.Galilei’ of the Universit`a degli Studi di Padova for hospitality during the development of this projec