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Anderson, P. R., Siahmazgi, S. G., Clark, R. D., & Fabbri, A. (2020). Method to compute the stress-energy tensor for a quantized scalar field when a black hole forms from the collapse of a null shell. Phys. Rev. D, 102(12), 125035–26pp.
Abstract: A method is given to compute the stress-energy tensor for a massless minimally coupled scalar field in a spacetime where a black hole forms from the collapse of a spherically symmetric null shell in four dimensions. Part of the method involves matching the modes for the in vacuum state to a complete set of modes in Schwarzschild spacetime. The other part involves subtracting from the unrenormalized expression for the stress-energy tensor when the field is in the in vacuum state, the corresponding expression when the field is in the Unruh state and adding to this the renormalized stress-energy tensor for the field in the Unruh state. The method is shown to work in the two-dimensional case where the results are known.
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de Azcarraga, J. A. (2022). The new Spanish educational legislation: why public education will not improve. Rev. Esp. Pedagog., 80(281), 111–129.
Abstract: This paper provides some reasons that explain, in the view of the author, why the present eagerness of the Spanish Educational Authorities to reform all levels of education, from primary school to the universities, will not improve the quality of the Spanish educational system.
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Pavao, R., Gubler, P., Fernandez-Soler, P., Nieves, J., Oka, M., & Takahashi, T. T. (2021). The negative-parity spin-1/2 A baryon spectrum from lattice QCD and effective theory. Phys. Lett. B, 820, 136473–8pp.
Abstract: The spectrum of the negative-parity spin-1/2 Lambda baryons is studied using lattice QCD and hadronic effective theory in a unitarized coupled-channel framework. A direct comparison between the two approaches is possible by considering the hadronic effective theory in a finite volume and with hadron masses and mesonic decay constants that correspond to the situation studied on the lattice. Comparing the energy level spectrum and SU(3) flavor decompositions of the individual states, it is found that the lowest two states extracted from lattice QCD can be associated with one of the two Lambda(1405)-poles and the Lambda(1670) resonance. The quark mass dependences of these two lattice QCD levels are in good agreement with their effective theory counterparts. However, as current lattice QCD studies still rely on three-quark operators to generate the physical states, clear signals corresponding to the meson-baryon scattering states, that appear in the finite volume effective theory calculation, are not yet seen.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2018). Search for pair and single production of vectorlike quarks in final states with at least one Z boson decaying into a pair of electrons or muons in pp collision data collected with the ATLAS detector at root s=13 TeV. Phys. Rev. D, 98(11), 112010–53pp.
Abstract: A search for vectorlike quarks is presented, which targets their decay into a Z boson and a third-generation Standard Model quark. In the case of a vectorlike quark T (B) with charge +2/3e (-1/3e), the decay searched for is T -> Zt (B -> Zb). Data for this analysis were taken during 2015 and 2016 with the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 36.1 fb(-1) of pp collisions at root s = 13 TeV. The final state used is characterized by the presence of b-tagged jets, as well as a Z boson with high transverse momentum, which is reconstructed from a pair of opposite-sign same-flavor leptons. Pair and single production of vectorlike quarks are both taken into account and are each searched for using optimized dileptonic exclusive and trileptonic inclusive event selections. In these selections, the high scalar sum of jet transverse momenta, the presence of high-transverse-momentum large-radius jets, as well as-in the case of the single-production selections-the presence of forward jets are used. No significant excess over the background-only hypothesis is found and exclusion limits at 95% confidence level allow masses of vectorlike quarks of m(T) > 1030 GeV (m(T) > 1210 GeV) and m(B) > 1010 GeV (m(B) > 1140 GeV) in the singlet (doublet) model. In the case of 100% branching ratio for T -> Zt (B -> Zb), the limits are m(T) > 1340 GeV (m(B) > 1220 GeV). Limits at 95% confidence level are also set on the coupling to Standard Model quarks for given vectorlike quark masses.
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Carames, T. F., Fontoura, C. E., Krein, G., Vijande, J., & Valcarce, A. (2018). Charmed baryons in nuclear matter. Phys. Rev. D, 98(11), 114019–9pp.
Abstract: We study the temperature and baryon density dependence of the masses of the lightest charmed baryons Lambda(c), Sigma(c) and Sigma(c)*. We also look at the effects of the temperature and baryon density on the binding energies of the Lambda N-c and Lambda(c)Lambda(c) systems. Baryon masses and baryon-baryon interactions are evaluated within a chiral constituent quark model. Medium effects are incorporated in those parameters of the model related to the dynamical breaking of chiral symmetry, which are the masses of the constituent quarks, the sigma and pi meson masses, and quark-meson couplings. We find that while the in-medium Lambda(c) mass decreases monotonically with temperature, those of Sigma(c) and Sigma(c)* have a nonmonotonic dependence. These features can be understood in terms of a simple group theory analysis regarding the one-gluon exchange interaction in those hadrons. The in-medium Lambda N-c and Lambda(c)Lambda(c) interactions are governed by a delicate balance involving a stronger attraction due to the decrease of the sigma meson mass, suppression of coupled-channel effects and lower thresholds, leading to shallow bound states with binding energies of a few MeV. The Lambda(c) baryon could possibly be bound to a large nucleus, in qualitative agreement with results based on relativistic mean field models or QCD sum rules. Ongoing experiments at RHIC or LHCb or the planned ones at FAIR and J-PARC may take advantage of the present results.
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