Sandner, S., Escudero, M., & Witte, S. J. (2023). Precision CMB constraints on eV-scale bosons coupled to neutrinos. Eur. Phys. J. C, 83(8), 709–12pp.
Abstract: The cosmic microwave background (CMB) has proven to be an invaluable tool for studying the properties and interactions of neutrinos, providing insight not only into the sum of neutrino masses but also the free streaming nature of neutrinos prior to recombination. The CMB is a particularly powerful probe of new eV-scale bosons interacting with neutrinos, as these particles can thermalizewith neutrinos via the inverse decay process, v (v) over bar -> X, and suppress neutrino free streaming near recombination – even for couplings as small as lambda(v) similar to O(10(-13)). Here, we revisit CMB constraints on such bosons, improving upon a number of approximations previously adopted in the literature and generalizing the constraints to a broader class of models. This includes scenarios in which the boson is either spin-0 or spin-1, the number of interacting neutrinos is either N-int = 1, 2 or 3, and the case in which a primordial abundance of the species is present. We apply these bounds to well-motivatedmodels, such as the singlet majoron model or a light U(1) L-mu- L-t gauge boson, and find that they represent the leading constraints for masses m(X) similar to 1 eV. Finally, we revisit the extent to which neutrinophilic bosons can ameliorate the Hubble tension, and find that recent improvements in the understanding of how such bosons damp neutrino free streaming reduces the previously found success of this proposal.
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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. (2019). Updated measurement of time-dependent CP-violating observables in B-s(0) -> J/psi K+K- decays. Eur. Phys. J. C, 79(8), 706–26pp.
Abstract: The decay-time-dependent CP asymmetry in B0 s. J/. K + K-decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 1.9 fb-1, collected with the LHCb detector at a centre-ofmass energy of 13 TeV in 2015 and 2016. Using a sample of approximately 117 000 signal decays with an invariant K + K-mass in the vicinity of the f( 1020) resonance, the CP-violating phase fs is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B0 s-B0s system, s. The difference of the average B0 s and B0 meson decay widths, s-d, is determined using in addition a sample of B0. J/. K + p-decays. The values obtained are fs =-0.083 +/- 0.041 +/- 0.006 rad, s = 0.077 +/- 0.008 +/- 0.003 ps-1 and s-d = -0.0041 +/- 0.0024 +/- 0.0015 ps-1, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from B0 s. J/. p + p-decays obtained using the same dataset as this analysis, and with previous independent LHCb results.
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Liang, W. H., Xie, J. J., & Oset, E. (2016). f(0)(500), f(0)(980), and a(0)(980) production in the chi(c1) -> eta pi(+)pi(-) reaction. Eur. Phys. J. C, 76(12), 700–7pp.
Abstract: We study the chi(c1) -> eta pi(+)pi(-) decay, paying attention to the production of f(0)(500), f(0)(980), and a(0)(980) from the final state interaction of pairs of mesons that can lead to these three mesons in the final state, which is implemented using the chiral unitary approach. Very clean and strong signals are obtained for the a(0)(980) excitation in the eta pi invariant mass distribution and for the f(0)(500) in the pi(+)pi(-) mass distribution. A smaller, but also clear signal for the f(0)(980) excitation is obtained. The results are contrasted with experimental data and the agreement found is good, providing yet one more test in support of the picture where these resonances are dynamically generated from the meson-meson interaction.
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Hirsch, M., Maselek, R., & Sakurai, K. (2021). Detecting long-lived multi-charged particles in neutrino mass models with MoEDAL. Eur. Phys. J. C, 81(8), 697–19pp.
Abstract: A certain class of neutrino mass models predicts long-lived particles whose electric charge is four or three times larger than that of protons. Such particles, if they are light enough, may be produced at the LHC and detected. We investigate the possibility of observing those long-lived multi-charged particles with the MoEDAL detector, which is sensitive to long-lived particles with low velocities (beta) and a large electric charge (Z) with Theta equivalent to beta /Z less than or similar to 0.15. We demonstrate that multi-charged scalar particles with a large Z give three-fold advantage for MoEDAL; reduction of Theta due to strong interactions with the detector, and enhancement of the photon-fusion process, which not only increases the production cross-section but also lowers the average production velocity, reducing Theta further. To demonstrate the performance of MoEDAL on multi-charged long-lived particles, two concrete neutrino mass models are studied. In the first model, the new physics sector is non-coloured and contains long-lived particles with electric charges 2, 3 and 4. A model-independent study finds MoEDAL can expect more than 1 signal event at the HL-LHC (L=300fb-1) if these particles are lighter than 600, 1100 and 1430 GeV, respectively. These compare with the current ATLAS limits 650, 780 and 920 GeV for L=36fb-1. The second model has a coloured new physics sector, which possesses long-lived particles with electric charges 4/3, 7/3 and 10/3. The corresponding MoEDAL's mass reaches at the HL-LHC are 1400, 1650 and 1800 GeV, respectively, which compare with the current CMS limits 1450, 1480 and 1510 GeV for L=36fb-1. In a model-specific study we explore the parameter space of neutrino mass generation models and identify the regions that can be probed with MoEDAL at the end of Run-3 and the High-Luminosity LHC.
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Donini, A., & Marimon, S. G. (2016). Micro-orbits in a many-brane model and deviations from Newton's 1/r(2) law. Eur. Phys. J. C, 76(12), 696–21pp.
Abstract: We consider a five-dimensional model with geometry M = M-4 x S-1, with compactification radius R. The Standard Model particles are localized on a brane located at y = 0, with identical branes localized at different points in the extra dimension. Objects located on our brane can orbit around objects located on a brane at a distance d = y/R, with an orbit and a period significantly different from the standard Newtonian ones. We study the kinematical properties of the orbits, finding that it is possible to distinguish one motion from the other in a large region of the initial conditions parameter space. This is a warm-up to study if a SM-like mass distribution on one (or more) distant brane(s) may represent a possible dark matter candidate. After using the same technique to the study of orbits of objects lying on the same brane (d = 0), we apply this method to the detection of generic deviations from the inverse-square Newton law. We propose a possible experimental setup to look for departures from Newtonian motion in the micro-world, finding that an order of magnitude improvement on present bounds can be attained at the 95% CL under reasonable assumptions.
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