ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Search for dark matter produced in association with a Higgs boson decaying to tau leptons at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 09(9), 189–53pp.
Abstract: A search for dark matter produced in association with a Higgs boson in final states with two hadronically decaying tau-leptons and missing transverse momentum is presented. The analysis uses 139 fb(-1) of proton-proton collision data at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. No evidence of physics beyond the Standard Model is found. The results are interpreted in terms of a 2HDM+a model featuring two scalar Higgs doublets and a pseudoscalar singlet field. Exclusion limits on the parameters of the model in selected benchmark scenarios are derived at 95% confidence level. Model-independent limits are also set on the visible cross-section for processes beyond the Standard Model producing missing transverse momentum in association with a Higgs boson decaying into tau-leptons.
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Pich, A., Solomonidi, E., & Vale Silva, L. (2023). Final-state interactions in the CP asymmetries of charm-meson two-body decays. Phys. Rev. D, 108, 036026–25pp.
Abstract: Urgent theoretical progress is needed in order to provide an estimate in the Standard Model of the recent measurement by LHCb of direct CP violation in charm-meson two-body decays. Rescattering effects must be taken into account for a meaningful theoretical description of the amplitudes involved in such category of observables, as signaled by the presence of large strong phases. We discuss the computation of the latter effects based on a two-channel coupled dispersion relation, which exploits isospin-zero phase shifts and inelasticity parametrizations of data coming from the rescattering processes ππ→ππ, πK→πK, and ππ→K¯K. The determination of the subtraction constants of the dispersive integrals relies on the leading contributions to the transition amplitudes from the 1/NC counting, where NC is the number of QCD colors. Furthermore, we use the measured values of the branching ratios to help in selecting the nonperturbative inputs in the isospin limit, from which we predict values for the CP asymmetries. We find that the predicted level of CP violation is much below the experimental value.
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Maji, R., Park, W. I., & Shafi, Q. (2023). Gravitational waves from walls bounded by strings in SO(10) model of pseudo-Goldstone dark matter. Phys. Lett. B, 845, 138127–5pp.
Abstract: We explore the gravitational wave spectrum generated by string-wall structures in an SO (10) (Spin(10)) based scenario of pseudo-Goldstone boson dark matter (pGDM) particle. This dark matter candidate is a linear combination of the Standard Model (SM) singlets present in the 126 and 16 dimensional Higgs fields. The Higgs 126-plet vacuum expectation value (VEV) < 126(H)> leaves unbroken the Z(2) subgroup of Z(4), the center of SO (10). Among other things, this yields topologically stable cosmic strings with a string tension μsimilar to < 126(H)>(2). The subsequent (spontaneous) breaking of Z(2) at a significantly lower scale by the 16-plet VEV < 16(H)> leads to the appearance of domain walls bounded by the strings produced earlier. We display the gravitational wave spectrum for G μvalues varying between 10(-15) and 10(-9) (< 126(H)> similar to 10(11) – 10(14) GeV), and < 16(H)> similar to 0.1 – 10(2) TeV range (G denotes Newton's constant.) These predictions can be tested, as we show, by a variety of (proposed) experiments including LISA, ET, CE and others.
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Jeong, K. S., & Park, W. I. (2023). Cosmology with a supersymmetric local B – L model. J. Cosmol. Astropart. Phys., 11(11), 016–34pp.
Abstract: We propose a minimal gauged U(1)(B-L) extension of the minimal supersymmetric Standard Model (MSSM) which resolves the cosmological moduli problem via thermal inflation, and realizes late-time Affleck-Dine leptogensis so as to generate the right amount of baryon asymmetry at the end of thermal inflation. The present relic density of dark matter can be explained by sneutrinos, MSSM neutralinos, axinos, or axions. Cosmic strings from U(1)(B-L) breaking are very thick, and so the expected stochastic gravitational wave background from cosmic string loops has a spectrum different from the one in the conventional Abelian-Higgs model, as would be distinguishable at least at LISA and DECIGO. The characteristic spectrum is due to a flat potential, and may be regarded as a hint of supersymmetry. Combined with the resolution of moduli problem, the expected signal of gravitational waves constrains the U(1)(B-L) breaking scale to be O(10(12-13)) GeV. Interestingly, our model provides a natural possibility for explaining the observed ultra-high-energy cosmic rays thanks to the fact that the core width of strings in our scenario is very large, allowing a large enhancement of particle emissions from the cusps of string loops. Condensation of LHu flat-direction inside of string cores arises inevitably and can also be the main source of the ultra-high-energy cosmic rays accompanied by ultra-high-energy lightest supersymmetric particles.
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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). Search for periodic signals in the dielectron and diphoton invariant mass spectra using 139 fb-1 of pp collisions at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 10(10), 079–51pp.
Abstract: A search for physics beyond the Standard Model inducing periodic signals in the dielectron and diphoton invariant mass spectra is presented using 139 fb(-1) of root s = 13 TeV pp collision data collected by the ATLAS experiment at the LHC. Novel search techniques based on continuous wavelet transforms are used to infer the frequency of periodic signals from the invariant mass spectra and neural network classifiers are used to enhance the sensitivity to periodic resonances. In the absence of a signal, exclusion limits are placed at the 95% confidence level in the two-dimensional parameter space of the clockwork gravity model. Model-independent searches for deviations from the background-only hypothesis are also performed.
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