Molina, R., Liu, Z. W., Geng, L. S., & Oset, E. (2024). Correlation function for the a0(980). Eur. Phys. J. C, 84(3), 328–8pp.
Abstract: We have conducted a model independent analysis of the (K+K0) pair correlation function obtained from ultra high energy pp collisions, with the aim of extracting the information encoded in it related to the KK interaction and the coupled channel pi(+)eta. With the present large errors at small relative (K+K0) momenta, we find that the information obtained about the scattering matrix suffers from large uncertainties. Even then, we are able to show that the data imply the existence of the a(0) resonance, a(0)(980), showing as a strong cusp close to the KK threshold. We also mention that the measurement of the pi(+)eta correlation function will be essential in order to constrain more the information on KK dynamics that can be obtained from correlation functions.
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Alves, J. M., Botella, F. J., Miro, C., & Nebot, M. (2023). Spontaneous CP violation and μ-τ symmetry intwo-Higgs-doublet models with flavour conservation. Eur. Phys. J. C, 83(10), 940–12pp.
Abstract: In multi-Higgs-doublet models, requiring simultaneously that (i) CP violation only arises spontaneously, (ii)tree level scalar flavour changing couplings are absent and (iii) the fermion mixing matrix is CP violating, can only be achieved in a very specific manner. A general approach with new clarifying insights on the question is presented. Considering the quark sector, that peculiar possibility is not viable on phenomenological grounds. We show that, considering the lepton sector, it is highly interesting and leads to viable models with mu-tau symmetric PMNS matrices. Phenomenological implications of the models, both for Dirac and Majorana (in a type I seesaw scenario) neutrinos, are analysed.
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Meloni, D., Morisi, S., & Peinado, E. (2012). Predicting leptonic CP violation in the light of the Daya Bay result on theta(13). Eur. Phys. J. C, 72(9), 2160–4pp.
Abstract: In the light of the recent Daya Bay result theta(DB)(13) = 8.8 degrees +/- 0.8 degrees, we reconsider the model presented in Meloni et al. (J. Phys. G 38: 015003, 2011), showing that, when all neutrino oscillation parameters are taken at their best fit values of Schwetz et al. (New J. Phys. 10: 113011, 2008) and where theta(13) = theta(DB)(13), the predicted values of the CP phase are delta approximate to pi/4.
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Mavromatos, N. E., Mitsou, V. A., Sarkar, S., & Vergou, A. (2012). Implications of a stochastic microscopic Finsler cosmology. Eur. Phys. J. C, 72(3), 1956–38pp.
Abstract: Within the context of supersymmetric space-time (D-particle) foam in string/brane-theory, we discuss a Finsler-induced cosmology and its implications for (thermal) dark matter abundances. This constitutes a truly microscopic model of dynamical space-time, where Finsler geometries arise naturally. The D-particle foam model involves point-like brane defects (D-particles), which provide the topologically non-trivial foamy structures of space-time. The D-particles can capture and emit stringy matter and this leads to a recoil of D-particles. It is indicated how one effect of such a recoil of D-particles is a back-reaction on the space-time metric of Finsler type which is stochastic. We show that such a type of stochastic space-time foam can lead to acceptable cosmologies at late epochs of the Universe, due to the non-trivial properties of the supersymmetric (BPS like) D-particle defects, which are such so as not to affect significantly the Hubble expansion. The restrictions placed on the free parameters of the Finsler type metric are obtained from solving the Boltzmann equation in this background for relic abundances of a Lightest Supersymmetric Particle (LSP) dark matter candidate. It is demonstrated that the D-foam acts as a source for particle production in the Boltzmann equation, thereby leading to enhanced thermal LSP relic abundances relative to those in the Standard Lambda CDM cosmology. For D-particle masses of order TeV, such effects may be relevant for dark matter searches at colliders. The latter constraints complement those coming from high-energy gamma-ray astronomy on the induced vacuum refractive index that D-foam models entail. We also comment briefly on the production mechanisms of such TeV-mass stringy defects at colliders, which, in view of the current LHC experimental searches, will impose further constraints on their couplings.
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Mavromatos, N. E., & Papavassiliou, J. (2018). Singular lensing from the scattering on special space-time defects. Eur. Phys. J. C, 78(1), 68–15pp.
Abstract: It is well known that certain special classes of self-gravitating point-like defects, such as global (non gauged) monopoles, give rise to non-asymptotically flat space-times characterized by solid angle deficits, whose size depends on the details of the underlying microscopic models. The scattering of electrically neutral particles on such space-times is described by amplitudes that exhibit resonant behaviour when thescattering and deficit angles coincide. This, in turn, leads to ring-like structures where the cross sections are formally divergent (“singular lensing”). In this work, we revisit this particular phenomenon, with the twofold purpose of placing it in a contemporary and more general context, in view of renewed interest in the theory and general phenomenology of such defects, and, more importantly, of addressing certain subtleties that appear in the particular computation that leads to the aforementioned effect. In particular, by adopting a specific regularization procedure for the formally infinite Legendre series encountered, we manage to ensure the recovery of theMinkowski space-time, and thus the disappearance of the lensing phenomenon, in the nodefect limit, and the validity of the optical theorem for the elastic total cross section. In addition, the singular nature of the phenomenon is confirmed by means of an alternative calculation, which, unlike the original approach, makes no use of the generating function of the Legendre polynomials, but rather exploits the asymptotic properties of the Fresnel integrals.
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