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Du, M. L., Guo, Z. H., & Oller, J. A. (2021). Insights into the nature of the P-cs(4459). Phys. Rev. D, 104(11), 114034–14pp.
Abstract: We study the nature of the recently observed Pcs(4459) by the LHCb collaboration by employing three methods based on the elastic effective-range expansion and the resulting size of the effective-range, the saturation of the compositeness relation and width of the resonance, and a direct fit to data involving the channels J/psi Lambda, Xi ' c over line D, and Xi c over line D*. We have also considered the addition of a Castillejo-Dalitz-Dyson (CDD) pole but this scenario can be discarded. Our different analyses clearly indicate the molecular nature of the Pcs(4459) with a clear Xi c over line D* dominant component. In relation with heavy-quark-spin symmetry our results also favor the actual existence of two resonances with J=1/2 (the lighter one) and 3/2 (the heavier one) in the energy region of the Pcs(4459). In the scenario of two-resonance for the Pcs(4459), the inclusion of the Xi ' c over line D channel is required for their mass splitting and it allows one to determine the spin structures of the two resonances.
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Guerrero, M., Olmo, G. J., Rubiera-Garcia, D., & Saez-Chillon Gomez, D. (2021). Shadows and optical appearance of black bounces illuminated by a thin accretion disk. J. Cosmol. Astropart. Phys., 08(8), 036–19pp.
Abstract: We study the light rings and shadows of an uniparametric family of spherically symmetric geometries interpolating between the Schwarzschild solution, a regular black hole, and a traversable wormhole, and dubbed as black bounces, all of them sharing the same critical impact parameter. We consider the ray-tracing method in order to study the impact parameter regions corresponding to the direct, lensed, and photon ring emissions, finding a broadening of all these regions for black bounce solutions as compared to the Schwarzschild one. Using this, we determine the optical appearance of black bounces when illuminated by three standard toy models of optically and geometrically thin accretion disks viewed in face-on orientation.
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Bodeker, D., Kuhnel, F., Oldengott, I. M., & Schwarz, D. J. (2021). Lepton flavor asymmetries and the mass spectrum of primordial black holes. Phys. Rev. D, 103(6), 063506–6pp.
Abstract: We study the influence of lepton flavor asymmetries on the formation and the mass spectrum of primordial black holes. We estimate the detectability of their mergers with LIGO/Virgo and show that the currently published gravitational wave events may actually be described by a primordial black hole spectrum from nonzero asymmetries. We suggest to use gravitational-wave astronomy as a novel tool to probe how lepton flavor asymmetric the Universe has been before the onset of neutrino oscillations.
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Breso-Pla, V., Falkowski, A., & Gonzalez-Alonso, M. (2021). A(FB) in the SMEFT: precision Z physics at the LHC. J. High Energy Phys., 08(8), 021–27pp.
Abstract: We study the forward-backward asymmetry A(FB) in pp -> l(+)l(-) at the Z peak within the Standard Model Effective Field Theory (SMEFT). We find that this observable provides per mille level constraints on the vertex corrections of the Z boson to quarks, which close a flat direction in the electroweak precision SMEFT fit. Moreover, we show that current A(FB) data is precise enough so that its inclusion in the fit improves significantly LEP bounds even in simple New Physics setups. This demonstrates that the LHC can compete with and complement LEP when it comes to precision measurements of the Z boson properties.
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Godbole, R. M., Maharathy, S. P., Mandal, S., Mitra, M., & Sinha, N. (2021). Interference effect in lepton number violating and conserving meson decays for a left-right symmetric model. Phys. Rev. D, 104(9), 095009–22pp.
Abstract: We study the effect of interference on the lepton number violating (LNV) and lepton number conserving (LNC) three-bodymeson decaysM(1)(+)-> l(i) (+) l(j)(+)pi(+/-) that arise in a TeV-scale left-right symmetric model (LRSM) with degenerate or nearly degenerate right-handed (RH) neutrinos. The LRSM contains three RH neutrinos and a RH gauge boson. The RH neutrinos with masses in the range of M-N similar to (MeV-few GeV) can give resonant enhancement in the semileptonic LNV and LNC meson decays. In the case where only one RH neutrino contributes to these decays, the predicted new physics branching ratios of semileptonic LNV and LNC meson decaysM(1)(+)-> l(i)(+) l(j)(+) pi(-) andM(+) 1 -> l(i)(+)l(j)(-) pi(+) are equal. We find that with at least two RH neutrinos contributing to the process, the LNV and LNC decay rates can differ. Depending on the neutrino mixing angles and CP-violating phases, the branching ratios of LNVand LNC decay channelsmediated by the heavy neutrinos can be either enhanced or suppressed, and the ratio of these two rates can differ from unity.
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