Gomez Dumm, D., Noguera, S., & Scoccola, N. N. (2023). Charged meson masses under strong magnetic fields: Gauge invariance and Schwinger phases. Phys. Rev. D, 108(1), 016012–29pp.
Abstract: We study the role of the Schwinger phase (SP) that appears in the propagator of a charged particle in the presence of a static and uniform magnetic field (B) over right arrow. We first note that this phase cannot be removed by a gauge transformation; far from this, we show that it plays an important role in the restoration of the symmetries of the system. Next, we analyze the effect of SPs in the one-loop corrections to charged pion and rho meson self-energies. To carry out this analysis we consider first a simple form for the meson-quark interactions, and then we study the pi(+) and rho(-) propagators within the Nambu-Jona-Lasinio model, performing a numerical analysis of the B dependence of meson lowest energy states. For both pi(+) and rho(-) mesons, we compare the numerical results arising from the full calculation-in which SPs are included in the propagators, and meson wave functions correspond to states of definite Landau quantum number-and those obtained within alternative schemes in which SPs are neglected (or somehow eliminated) and meson states are described by plane waves of definite four-momentum.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Search for direct CP violation in charged charmless B → PV decays. Phys. Rev. D, 108(1), 012013–13pp.
Abstract: Measurements of CP asymmetry in charmless B -> PV decays are presented, where P and V denote a pseudoscalar and a vector meson, respectively. Five different B -> PV decays from four final states, B-+/- -> pi(+/-)pi(+) pi(-), B-+/- -> K-+/-pi(+) pi(-), B-+/-->(KK+K-)-K-+/- and B-+/- -> pi(K+K-)-K-+/- are analyzed. The measurements are based on a method that does not require full amplitude analyses, and are performed using proton-proton collision data at a center-of-mass energy of 13 TeV collected by LHCb between 2015 and 2018, corresponding to an integrated luminosity of 5.9 fb(-1). In the pi(+) pi(-) P-wave, in the region dominated by the B-+/- -> rho(770)K-0(+/-) decay, a CP asymmetry of A(CP) = +0.150 +/- 0.019 +/- 0.011 is measured, where the first uncertainty is statistical and the second is systematic. This is the first observation of CP violation in this process. For the other four decay channels, in regions dominated by the B-+/- -> rho(770)(0)pi(+/-), B-+/- -> K(-)*(892)(0) pi(+/-), B-+/- -> K(-)* (892)K-+/- and B-+/- -> (sic)(1020) K-+/- decays, CP asymmetries in the P-wave compatible with zero are measured.
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Gil-Dominguez, F., Alarcon, J. M., & Weiss, C. (2023). Proton charge radius extraction from muon scattering at MUSE using dispersively improved chiral effective field theory. Phys. Rev. D, 108(7), 074026–14pp.
Abstract: The MUSE experiment at Paul Scherrer Institute will perform the first measurement of low-energy muon-proton elastic scattering (muon lab momenta 115-210 MeV) with the aim of determining the proton charge radius. We study the prospects for the proton radius extraction using the theoretical framework of dispersively improved chiral effective field theory (DI.EFT). It connects the proton radii with the finite-Q(2) behavior of the form factors through complex analyticity and enables the use of data up to Q(2) similar to 0.1 GeV2 for radius extraction. We quantify the sensitivity of the μp cross section to the proton charge radius, the theoretical uncertainty of the cross section predictions, and the size of two-photon exchange corrections. We find that the optimal kinematics for radius extraction at MUSE is at momenta 210 MeV and Q(2) similar to 0.05-0.08 GeV2. We compare the performance of electron and muon scattering in the same kinematics. As a by-product, we obtain explicit predictions for the μp and ep cross sections at MUSE as functions of the assumed value of the proton radius.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2023). Pursuit of paired dijet resonances in the Run 2 dataset with ATLAS. Phys. Rev. D, 108(11), 112005–30pp.
Abstract: New particles with large masses that decay into hadronically interacting particles are predicted by many models of physics beyond the Standard Model. A search for a massive resonance that decays into pairs of dijet resonances is performed using 140 fb(-1) of proton-proton collisions at ffiffiffisp root s = 13 TeV recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. Resonances are searched for in the invariant mass of the tetrajet system, and in the average invariant mass of the pair of dijet systems. A data-driven background estimate is obtained by fitting the tetrajet and dijet invariant mass distributions with a four-parameter dijet function and a search for local excesses from resonant production of dijet pairs is performed. No significant excess of events beyond the Standard Model expectation is observed, and upper limits are set on the production cross sections of new physics scenarios.
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Ferreiro, A., Monin, S., & Torrenti, F. (2024). Physical scale adiabatic regularization in cosmological spacetimes. Phys. Rev. D, 109(4), 045015–16pp.
Abstract: We develop a new regularization method for the stress -energy tensor and the two -point function of free quantum scalar fields propagating in cosmological spacetimes. We proceed by extending the adiabatic regularization scheme with the introduction of two additional mass scales. By setting them to the order of the physical scale of the studied scenario, we obtain ultraviolet -regularized quantities that do not distort the power spectra amplitude at the infrared scales amplified by the expansion of the Universe. This is not ensured by the standard adiabatic approach. We also show how our proposed subtraction terms can be interpreted as a renormalization of coupling constants in the Einstein equations. We finally illustrate our proposed regularization method in two scenarios of cosmological interest: de Sitter inflation and geometric reheating.
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Leite, J., Sadhukhan, S., & Valle, W. F. (2024). Dynamical scoto-seesaw mechanism with gauged B – L symmetry. Phys. Rev. D, 109(3), 035023–17pp.
Abstract: We propose a dynamical scoto-seesaw mechanism using a gauged B – L symmetry. Dark matter is reconciled with neutrino mass generation, in such a way that the atmospheric scale arises a la seesaw, while the solar scale is scotogenic, arising radiatively from the exchange of “dark” states. This way we “explain” the solar-to-atmospheric scale ratio. The TeV-scale seesaw mediator and the two dark fermions carry different B – L charges. Dark matter stability follows from the residual matter parity that survives B – L breaking. Besides having collider tests, the model implies sizable charged lepton flavor violating (cLFV) phenomena, including Goldstone boson emission processes.
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NA64 Collaboration(Andreev, Y. M. et al), Molina Bueno, L., & Tuzi, M. (2024). Probing light dark matter with positron beams at NA64. Phys. Rev. D, 109(3), L031103–6pp.
Abstract: We present the results of a missing-energy search for light dark matter which has a new interaction with ordinary matter transmitted by a vector boson, called dark photon A'. For the first time, this search is performed with a positron beam by using the significantly enhanced production of A' in the resonant annihilation of positrons with atomic electrons of the target nuclei, followed by the invisible decay of A' into dark matter. No events were found in the signal region with (10.1 +/- 0.1) x 109 positrons on target with 100 GeV energy. This allowed us to set new exclusion limits that, relative to the collected statistics, prove the power of this experimental technique. This measurement is a crucial first step toward a future exploration program with positron beams, whose estimated sensitivity is here presented.
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Molina, R., Xiao, C. W., Liang, W. H., & Oset, E. (2024). Correlation functions for the N*(1535) and the inverse problem. Phys. Rev. D, 109(5), 054002–10pp.
Abstract: The N*(1535) can be dynamically generated in the chiral unitary approach with the coupled channels, K0E+; K+E0; K+A, and eta p. In this work, we evaluate the correlation functions for every channel and face the inverse problem. Assuming the correlation functions to correspond to real measurements, we conduct a fit to the data within a general framework in order to extract the information contained in these correlation functions. The bootstrap method is used to determine the uncertainties of the different observables, and we find that, assuming errors of the same order than in present measurements of correlation functions, one can determine the scattering length and effective range of all channels with a very good accuracy. Most remarkable is the fact that the method predicts the existence of a bound state of isospin 12 nature around the mass of the N*(1535) with an accuracy of 6 MeV. These results should encourage the actual measurement of these correlation functions (only the K+A one is measured so far), which can shed valuable light on the relationship of the N*(1535) state to these coupled channels, a subject of continuous debate.
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Karan, A., Miralles, V., & Pich, A. (2024). Updated global fit of the aligned two-Higgs-doublet model with heavy scalars. Phys. Rev. D, 109(3), 035012–29pp.
Abstract: An updated global fit on the parameter-space of the aligned two-Higgs-doublet model is performed with the help of the open-source package HEPfit, assuming the Standard-Model Higgs to be the lightest scalar. No new sources of CP violation, other than the phase in the Cabibbo-Kobayashi-Maskawa matrix of the Standard Model, are considered. A similar global fit was previously performed by O. Eberhardt et al. [Global fits in the aligned two-Higgs-doublet model, J. High Energy Phys. 05 (2021) 005] with a slightly different set of parameters. Our updated fit incorporates improved analyses of the theoretical constraints required for the perturbative unitarity and boundedness of the scalar potential from below, additional flavor observables and updated data on direct searches for heavy scalars at the LHC, Higgs signal strengths, and electroweak precision observables. Although not included in the main fit, the implications of the CDF measurement of the W +/- mass are also discussed.
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Alexandre, J., Mavromatos, N. E., Mitsou, V. A., & Musumeci, E. (2024). Resummation schemes for high-electric-charge objects leading to improved experimental mass limits. Phys. Rev. D, 109(3), 036026–20pp.
Abstract: High-electric-charge compact objects (HECOs) appear in several theoretical particle physics models beyond the Standard Model, and are actively searched for in current colliders, such as the Large Hadron Collider at CERN. In such searches, mass bounds of these objects have been placed, using Drell-Yan and photon-fusion processes at tree level so far. However, such mass-bound estimates are not reliable, given that, as a result of the large values of the electric charge of the HECO, perturbative quantum electrodynamics calculations break down. In this work, we perform a Dyson-Schwinger resummation scheme (as opposed to lattice strong-coupling approach), which makes the computation of the pertinent HECO-production cross sections reliable, thus allowing us to extract improved mass bounds for such objects from ATLAS and MoEDAL searches.
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