Coloma, P., Hernandez, P., Muñoz, V., & Shoemaker, I. M. (2020). New constraints on heavy neutral leptons from Super-Kamiokande data. Eur. Phys. J. C, 80(3), 235–7pp.
Abstract: Heavy neutral leptons are predicted in many extensions of the Standard Model with massive neutrinos. If kinematically accessible, they can be copiously produced from kaon and pion decays in atmospheric showers, and subsequently decay inside large neutrino detectors. We perform a search for these long-lived particles using Super-Kamiokande multi-GeV neutrino data and derive stringent limits on the mixing with electron, muon and tau neutrinos as a function of the long-lived particle mass. We also present the limits on the branching ratio versus lifetime plane, which are helpful in determining the constraints in non-minimal models where the heavy neutral leptons have new interactions with the Standard Model.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Measurement of the eta(c)(1S) production cross-section in p p collisions at root s=13TeV. Eur. Phys. J. C, 80(3), 191–18pp.
Abstract: Using a data sample corresponding to an integrated luminosity of 2.0 fb-1, collected by the LHCb experiment, the production of the.c(1S) state in proton-proton collisions at a centre-of-mass energy of v s = 13 TeVis studied in the rapidity range 2.0 < y < 4.5 and in the transverse momentum range 6.5 < pT < 14.0GeV. The cross-section for prompt production of.c(1S) mesons relative to that of the J/. meson is measured using the p p decay mode and is found to be s.c(1S)/sJ/. = 1.69 +/- 0.15 +/- 0.10 +/- 0.18. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the J/.. p p and.c. p p decays. The prompt.c(1S) production cross-section is determined to be s.c( 1S) = 1.26 +/- 0.11 +/- 0.08 +/- 0.14 μb, where the last uncertainty includes that on the J/. meson cross-section. The ratio of the branching fractions of b-hadron decays to the.c(1S) and J/. states is measured to be Bb..c X /Bb. J/. X = 0.48 +/- 0.03 +/- 0.03 +/- 0.05, where the last uncertainty is due to those on the branching fractions of the J/.. p p and.c. p p decays. The difference between the J/. and.c(1S) masses is also determined to be 113.0 +/- 0.7 +/- 0.1MeV, which is the most precise single measurement of this quantity to date.
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Delhom, A., Lobo, I. P., Olmo, G. J., & Romero, C. (2020). Conformally invariant proper time with general non-metricity. Eur. Phys. J. C, 80(5), 415–11pp.
Abstract: We show that the definition of proper time for Weyl-invariant space-times given by Perlick naturally extends to spaces with arbitrary non-metricity. We then discuss the relation between this generalized proper time and the Ehlers-Pirani-Schild definition of time when there is arbitrary non-metricity. Then we show how this generalized proper time suffers from a second clock effect. Assuming that muons are a device to measure this proper time, we constrain the non-metricity tensor on Earth's surface and then elaborate on the feasibility of such assumption.
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Liang, W. H., & Oset, E. (2020). Testing the origin of the f1(1420) with the Kbar p -> Lambda(Sigma) K Kbar pi reaction. Eur. Phys. J. C, 80(5), 407–8pp.
Abstract: We study the K¯p→YKK¯π reactions with K¯=K¯0,K− and Y=Σ0,Σ+,Λ, in the region of KK¯π invariant masses of 1200−1550 MeV. The strong coupling of the f1(1285) resonance to K∗K¯ makes the mechanism based on K∗ exchange very efficient to produce this resonance observed in the KK¯π invariant mass distribution. In addition, in all the reactions one observes an associated peak at 1420 MeV which comes from the K∗K¯ decay mode of the f1(1285) when the K∗ is placed off shell at higher invariant masses. We claim this to be the reason for the peak of the K∗K¯ distribution seen in the experiments which has been associated to the “f1(1420)” resonance.
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Felea, D., Mamuzic, J., Maselek, R., Mavromatos, N. E., Mitsou, V. A., Pinfold, J. L., et al. (2020). Prospects for discovering supersymmetric long-lived particles with MoEDAL. Eur. Phys. J. C, 80(5), 431–12pp.
Abstract: We present a study on the possibility of searching for long-lived supersymmetric partners with the MoEDAL experiment at the LHC. MoEDAL is sensitive to highly ionising objects such as magnetic monopoles or massive (meta)stable electrically charged particles. We focus on prospects of directly detecting long-lived sleptons in a phenomenologically realistic model which involves an intermediate neutral long-lived particle in the decay chain. This scenario is not yet excluded by the current data from ATLAS or CMS, and is compatible with astrophysical constraints. Using Monte Carlo simulation, we compare the sensitivities of MoEDAL versus ATLAS in scenarios where MoEDAL could provide discovery reach complementary to ATLAS and CMS, thanks to looser selection criteria combined with the virtual absence of background. It is also interesting to point out that, in such scenarios, in which charged staus are the main long-lived candidates, the relevant mass range for MoEDAL is compatible with a potential role of Supersymmetry in providing an explanation for the anomalous events observed by the ANITA detector.
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