Abreu, L. M., Song, J., Brandao, P. C. S., & Oset, E. (2024). A note on the tensor and vector exchange contributions to K (K)over-bar → K (K)over-bar, D(D)over-bar → D(D)over-bar and π+π- → π+π- reactions. Eur. Phys. J. A, 60(3), 76–10pp.
Abstract: In this note we study the tensor and vector exchange contributions to the elastic reactions involving the pseudoscalars mesons pi(+) pi(-), K+ K- and D+D-. In the case of the tensor-exchange contributions we assume that an intermediate tensor f(2)(1270) is dynamically generated from the interaction of two virtual rho mesons, with the use of a pole approximation. The calculation of the two-loop amplitude is facilitated since the triangle loops can be factorized and computed separately. The results show very small contributions coming from the tensor-exchange mechanisms when compared with those from the vector-exchange processes. We compare our results for pi pi and K (K) over bar scattering with those obtained in other works where the f2(1270) is considered as an ordinary q (q) over bar meson. Our picture provides a smaller contribution but of similar order of magnitude for pion scattering and stabilizes the results in the case of K (K) over bar, allowing us to make estimates for D (D) over bar scattering.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2018). Measurement of differential cross sections and W+/W- cross-section ratios for W boson production in association with jets at root s=8 TeV with the ATLAS detector. J. High Energy Phys., 05(5), 077–60pp.
Abstract: This paper presents a measurement of the W boson production cross section and the W+/W- cross-section ratio, both in association with jets, in proton-proton collisions at root s = 8 TeV with the ATLAS experiment at the Large Hadron Collider. The measurement is performed in final states containing one electron and missing transverse momentum using data corresponding to an integrated luminosity of 20.2 fb(-1). Differential cross sections for events with at least one or two jets are presented for a range of observables, including jet transverse momenta and rapidities, the scalar sum of transverse momenta of the visible particles and the missing transverse momentum in the event, and the transverse momentum of the W boson. For a subset of the observables, the differential cross sections of positively and negatively charged W bosons are measured separately. In the cross-section ratio of W+/W- the dominant systematic uncertainties cancel out, improving the measurement precision by up to a factor of nine. The observables and ratios selected for this paper provide valuable input for the up quark, down quark, and gluon parton distribution functions of the proton.
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Chen, P., Centelles Chulia, S., Ding, G. J., Srivastava, R., & Valle, J. W. F. (2018). Neutrino predictions from generalized CP symmetries of charged leptons. J. High Energy Phys., 07(7), 077–26pp.
Abstract: We study the implications of generalized CP transformations acting on the mass matrices of charged leptons in a model-independent way. Generalized e – mu, e – tau and μ- tau symmetries are considered in detail. In all cases the physical parameters of the lepton mixing matrix, three mixing angles and three CP phases can be expressed in terms of a restricted set of independent “theory parameters” that characterize a given choice of CP transformation. This leads to implications for neutrino oscillations as well as neutrinoless double beta decay experiments.
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Gisbert, H., Miralles, V., & Ruiz Vidal, J. (2022). Electric dipole moments from colour-octet scalars. J. High Energy Phys., 04(4), 077–25pp.
Abstract: We present the contributions to electric dipole moments (EDMs) induced by the Yukawa couplings of an additional electroweak doublet of colour-octet scalars. The full set of one-loop diagrams and the enhanced higher-order effects from Barr-Zee diagrams are computed for the quark (chromo-)EDM, along with the two-loop contributions to the Weinberg operator. Using the stringent experimental upper limits on the neutron EDM, constraints on the parameter space of the Manohar-Wise model are derived.
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Figueroa, D. G., Florio, A., Opferkuch, T., & Stefanek, B. (2023). Lattice simulations of non-minimally coupled scalar fields in the Jordan frame. SciPost Phys., 15(3), 077–28pp.
Abstract: The presence of scalar fields with non-minimal gravitational interactions of the form & xi;|& phi;|2R may have important implications for the physics of the early universe. We propose a procedure to solve the dynamics of non-minimally coupled scalar fields directly in the Jordan frame, where the non-minimal couplings are maintained explicitly. Our algorithm can be applied to lattice simulations that include minimally coupled fields and an arbitrary number of non-minimally coupled scalars, with the expansion of the universe sourced by all fields present. This includes situations when the dynamics become fully inhomogeneous, fully non-linear (due to e.g. backreaction or mode rescattering effects), and/or when the expansion of the universe is dominated by non-minimally coupled species. As an example, we study geometric preheating with a non-minimally coupled scalar spectator field when the inflaton oscillates following the end of inflation.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Evidence for the charge asymmetry in pp → t(t)over-bar production at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 08(8), 077–89pp.
Abstract: Inclusive and differential measurements of the top-antitop ( t (t) over bar) charge asymmetry A(C)(t (t) over bar) and the leptonic asymmetry A(C)(l (l) over bar) are presented in proton-proton collisions at root s = 13 TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb(-1), combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive t (t) over bar charge asymmetry is measured to be A(C)(t (t) over bar) = 0.0068 +/- 0.0015, which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the t (t) over bar system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Search for the lepton-flavour violating decays B-(s)(0) -> e(+/-) mu(-/+). J. High Energy Phys., 03(3), 078–20pp.
Abstract: A search for the lepton-flavour violating decays B-(s)(0) -> e(+/-)mu(-/+) and B-(s)(0) -> e(+/-)mu(-/+) performed based on a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb(-1), collected with the LHCb experiment at centre-of-mass energies of 7 and 8TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the B-(s)(0) -> e(+/-)mu(-/+) decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate. The results are B(B-s(0) -> e(+/-)mu(-/+)) < 6.3 (5.4) x 10(-9) and B(B-s(0) -> e(+/-)mu(-/+)) < 7.2(6.0) x 10(-9) at 95% (90%) confidence level, respectively. The upper limit on the branching fraction of the B-0 -> e(+/-)mu(-/+) decay is also evaluated, obtaining B(B-0 -> e(+/-)mu(-/+)) < 1.3 (1.0) x 10(-9) at 95% (90%) confidence level. These are the strongest limits on these decays to date.
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Coloma, P., Fernandez-Martinez, E., Gonzalez-Lopez, M., Hernandez-Garcia, J., & Pavlovic, Z. (2021). GeV-scale neutrinos: interactions with mesons and DUNE sensitivity. Eur. Phys. J. C, 81(1), 78–24pp.
Abstract: The simplest extension of the SM to account for the observed neutrino masses and mixings is the addition of at least two singlet fermions (or right-handed neutrinos). If their masses lie at or below the GeV scale, such new fermions would be produced in meson decays. Similarly, provided they are sufficiently heavy, their decay channels may involve mesons in the final state. Although the couplings between mesons and heavy neutrinos have been computed previously, significant discrepancies can be found in the literature. The aim of this paper is to clarify such discrepancies and provide consistent expressions for all relevant effective operators involving mesons with masses up to 2 GeV. Moreover, the effective Lagrangians obtained for both the Dirac and Majorana scenarios are made publicly available as FeynRules models so that fully differential event distributions can be easily simulated. As an application of our setup, we numerically compute the expected sensitivity of the DUNE near detector to these heavy neutral leptons.
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Gonzalez-Iglesias, D., Esperante, D., Gimeno, B., Boronat, M., Blanch, C., Fuster-Martinez, N., et al. (2021). Analytical RF Pulse Heating Analysis for High Gradient Accelerating Structures. IEEE Trans. Nucl. Sci., 68(2), 78–91.
Abstract: The main aim of this work is to present a simple method, based on analytical expressions, for obtaining the temperature increase due to the Joule effect inside the metallic walls of an RF accelerating component. This technique relies on solving the 1-D heat-transfer equation for a thick wall, considering that the heat sources inside the wall are the ohmic losses produced by the RF electromagnetic fields penetrating the metal with finite electrical conductivity. Furthermore, it is discussed how the theoretical expressions of this method can be applied to obtain an approximation to the temperature increase in realistic 3-D RF accelerating structures, taking as an example the cavity of an RF electron photoinjector and a traveling wave linac cavity. These theoretical results have been benchmarked with numerical simulations carried out with commercial finite-element method (FEM) software, finding good agreement among them. Besides, the advantage of the analytical method with respect to the numerical simulations is evidenced. In particular, the model could be very useful during the design and optimization phase of RF accelerating structures, where many different combinations of parameters must be analyzed in order to obtain the proper working point of the device, allowing to save time and speed up the process. However, it must be mentioned that the method described in this article is intended to provide a quick approximation to the temperature increase in the device, which of course is not as accurate as the proper 3-D numerical simulations of the component.
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Nichols, A. L., Dimitriou, P., Algora, A., Fallot, M., Giot, L., Kondev, F. G., et al. (2023). Improving fission-product decay data for reactor applications: part I-decay heat. Eur. Phys. J. A, 59(4), 78–78pp.
Abstract: Effort has been expended to assess the relative merits of undertaking further decay-data measurements of the main fission-product contributors to the decay heat of neutron-irradiated fissionable fuel and related actinides by means of Total Absorption Gamma-ray Spectroscopy (TAGS – sometimes abbreviated to TAS) and Discrete Gamma-ray Spectroscopy (DGS). This review has been carried out following similar work performed under the auspices of OECD/WPEC-Subgroup 25 (2005-2007) and the International Atomic Energy Agency (2009, 2014), and various highly relevant TAGS measurements completed as a consequence of such assessments. We present our recommendations for new decay-data evaluations, along with possible requirements for total absorption and discrete high-resolution gamma-ray spectroscopy studies that cover approximately 120 fission products and various isomeric states.
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