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Campanario, F., Czyz, H., Gluza, J., Jelinski, T., Rodrigo, G., Tracz, S., et al. (2019). Standard model radiative corrections in the pion form factor measurements do not explain the a(mu) anomaly. Phys. Rev. D, 100(7), 076004–5pp.
Abstract: In this paper, we address the question of whether the almost four standard deviations difference between theory and experiment for the muon anomalous magnetic moment a(mu) can be explained as a higher-order Standard Model perturbation effect in the pion form factor measurements. This question has, until now, remained open, obscuring the source of discrepancies between the measurements. We calculate the last radiative corrections for the extraction of the pion form factor, which were believed to be potentially substantial enough to explain the data within the Standard Model. We find that the corrections are too small to diminish existing discrepancies in the determination of the pion form factor for different kinematical configurations of low-energy BABAR, BES-III and KLOE experiments. Consequently, they cannot noticeably change the previous predictions for a(mu) and decrease the deviations between theory and direct measurements. To solve the above issues, new data and better understanding of low-energy experimental setups are needed, especially as new direct a(mu) measurements at Fermilab and J-PARC will provide new insights and substantially shrink the experimental error.
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Campanario, F., Kaiser, N., & Zeppenfeld, D. (2014). W gamma production in vector boson fusion at NLO in QCD. Phys. Rev. D, 89(1), 014009–5pp.
Abstract: The next-to-leading order QCD corrections to W-+/-gamma. production in association with two jets via vector boson fusion are calculated, including the leptonic decay of the W with full off-shell effects and spin correlations. The process lends itself to a test of quartic gauge couplings. The next-to-leading order corrections reduce the scale uncertainty significantly and show a nontrivial phase space dependence.
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Campanario, F., Roth, R., & Zeppenfeld, D. (2015). QCD radiation in WH and WZ production and anomalous coupling measurements. Phys. Rev. D, 91(5), 054039–10pp.
Abstract: We study QCD radiation for the WH and WZ production processes at the LHC. We identify the regions sensitive to anomalous couplings, by considering jet observables, computed at next-to-leading-order QCD with the use of the Monte Carlo program VBFNLO. Based on these observations, we propose the use of a dynamical jet veto. The dynamical jet veto avoids the problem of large logarithms depending on the veto scale, hence providing more reliable predictions and simultaneously increasing the sensitivity to anomalous coupling searches, especially in the WZ production process.
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Campanario, F., Kerner, M., Ninh, L. D., & Zeppenfeld, D. (2014). Next-to-leading order QCD corrections to W+W+ and W-W- production in association with two jets. Phys. Rev. D, 89(5), 054009–11pp.
Abstract: We present a study of W+W+ jj and W-W-jj production including leptonic decays in hadron-hadron collisions. The full electroweak and QCD induced contributions and their interferences are calculated at leading order. We find that, for inclusive cuts, the interference effects can be large if the jets are produced with large transverse momentum where, however, the production rate is suppressed. We also discuss the vector-boson-fusion cuts and show the validity of the vector-boson-fusion approximation. The next-to-leading order QCD corrections to the QCD-induced channels are also calculated. Compared to the previous calculation, we allow the intermediate W bosons to be off shell. For on-shell W production, we obtain an excellent agreement with previous results. Our code will be publicly available as part of the parton level Monte Carlo program VBFLNO.
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Campanario, F., Figy, T. M., Platzer, S., Rauch, M., Schichtel, P., & Sjodahl, M. (2018). Stress testing the vector-boson-fusion approximation in multijet final states. Phys. Rev. D, 98(3), 033003–7pp.
Abstract: We consider electroweak Higgs plus three jets production at NLO QCD beyond strict VBF acceptance cuts. We investigate, for the first time, how accurate the VBF approximation is in these regions and within perturbative uncertainties by a detailed comparison of full and approximate calculations. We find that a rapidity gap between the tagging jets guarantees a good approximation, while an invariant mass cut alone is not sufficient, which needs to be confronted with experimental choices. We also find that a significant part of the QCD corrections can be attributed to Higgs-Strahlungs-type topologies.
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Candela, P. M., De Romeri, V., & Papoulias, D. K. (2023). COHERENT production of a dark fermion. Phys. Rev. D, 108(5), 055001–19pp.
Abstract: We consider the possible production of a new MeV-scale fermion at the COHERENT experiment. The new fermion, belonging to a dark sector, can be produced through the up-scattering process of neutrinos off the nuclei and the electrons of the detector material, via the exchange of a light vector or scalar mediator. We perform a detailed statistical analysis of the combined COHERENT CsI and LAr datasets and obtain up-to-date constraints on the couplings and masses of the dark fermion and mediators. We finally briefly comment about the stability of the dark fermion.
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Candia, P., Cottin, G., Mendez, A., & Muñoz, V. (2021). Searching for light long lived neutralinos at Super-Kamiokande. Phys. Rev. D, 104(5), 055024–11pp.
Abstract: Light neutralinos could be copiously produced from the decays of mesons generated in cosmic-ray air showers. These neutralinos can be long-lived particles in the context of R-parity violating (RPV) supersymmetric models, implying that they could be capable of reaching the surface of the earth and decay within the instrumental volume of large neutrino detectors. In this article, we use atmospheric neutrino data from the Super-Kamiokande experiment to derive novel constraints for the RPV couplings involved in the production of long-lived light neutralinos from the decays of charged D-mesons and kaons. Our results highlight the potential of neutrino detectors to search for long-lived particles, by demonstrating that it is possible to explore regions of parameter space that are not yet constrained by any fixed-target nor collider experiments.
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Capozzi, F., Chakraborty, M., Chakraborty, S., & Sen, M. (2022). Supernova fast flavor conversions in 1+1D: Influence of mu-tau neutrinos. Phys. Rev. D, 106(8), 083011–9pp.
Abstract: In the dense supernova environment, neutrinos can undergo fast flavor conversions which depend on the large neutrino-neutrino interaction strength. It has been recently shown that both their presence and outcome can be affected when passing from the commonly used three neutrino species approach to the more general one with six species. Here, we build up on a previous work performed on this topic and perform a numerical simulation of flavor evolution in both space and time, assuming six neutrino species. We find that the results presented in our previous work remain qualitatively the same even for flavor evolution in space and time. This emphasizes the need for going beyond the simplistic approximation with three species when studying fast flavor conversions.
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Capozziello, S., Harko, T., Koivisto, T. S., Lobo, F. S. N., & Olmo, G. J. (2012). Wormholes supported by hybrid metric-Palatini gravity. Phys. Rev. D, 86(12), 127504–5pp.
Abstract: Recently, a modified theory of gravity was presented, which consists of the superposition of the metric Einstein-Hilbert Lagrangian with an f(R) term constructed a la Palatini. The theory possesses extremely interesting features such as predicting the existence of a long-range scalar field, that explains the late-time cosmic acceleration and passes the local tests, even in the presence of a light scalar field. In this brief report, we consider the possibility that wormholes are supported by this hybrid metric-Palatini gravitational theory. We present here the general conditions for wormhole solutions according to the null energy conditions at the throat and find specific examples. In the first solution, we specify the redshift function, the scalar field and choose the potential that simplifies the modified Klein-Gordon equation. This solution is not asymptotically flat and needs to be matched to a vacuum solution. In the second example, by adequately specifying the metric functions and choosing the scalar field, we find an asymptotically flat spacetime.
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Cappiello, L., Cata, O., & D'Ambrosio, G. (2012). Holographic approach to low-energy weak interactions of mesons. Phys. Rev. D, 85(1), 015003–13pp.
Abstract: We apply the double-trace formalism to incorporate nonleptonic weak interactions of mesons into holographic models of the strong interactions. We focus our attention upon Delta S = 1 nonleptonic kaon decays. By working with a Yang-Mills-Chern-Simons 5-dimensional action, we explicitly show how, at low energies, one recovers the Delta S = 1 weak chiral Lagrangian for both the anomalous and nonanomalous sectors. We provide definite predictions for the low-energy coefficients in terms of the AdS metric and argue that the double-trace formalism is a 5-dimensional avatar of the Weak Deformation Model introduced long ago by Ecker et al. As a significant phenomenological application, we reassess the K -> 3 pi decays in the light of the holographic model. Previous models found a fine-tuned cancellation of resonance exchange in these decays, which was both conceptually puzzling and quantitatively in disagreement with experimental results. The holographic model we build is an illustrative counterexample showing that the cancellation encountered in the literature is not generic but a model-dependent statement and that agreement with experiment can be obtained.
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