Balbinot, R., & Fabbri, A. (2023). Quantum energy momentum tensor and equal time correlations in a Reissner-Nordström black hole. Phys. Rev. D, 108, 045004–9pp.
Abstract: We consider a Reissner-Nordström black hole formed by the collapse of a charged null shell. The renormalized expectation values of the energy-momentum tensor operator for a massless scalar field propagating in the two-dimensional section of this spacetime are given. We then analyze the across-the-horizon correlations of the related energy density operator for free-falling observers to reveal the correlations between the Hawking particles and their interior partners.
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Pompa, F., Schwetz, T., & Zhu, J. Y. (2023). Impact of nuclear matrix element calculations for current and future neutrinoless double beta decay searches. J. High Energy Phys., 06(6), 104–29pp.
Abstract: Nuclear matrix elements (NME) are a crucial input for the interpretation of neutrinoless double beta decay data. We consider a representative set of recent NME calculations from different methods and investigate the impact on the present bound on the effective Majorana mass m(& beta;& beta;) by performing a combined analysis of the available data as well as on the sensitivity reach of future projects. A crucial role is played by the recently discovered short-range contribution to the NME, induced by light Majorana neutrino masses. Depending on the NME model and the relative sign of the long- and short-range contributions, the current 3 & sigma; bound can change between m(& beta;& beta;)< 40 meV and 600 meV. The sign-uncertainty may either boost the sensitivity of next-generation experiments beyond the region for m(& beta;& beta;) predicted for inverted mass ordering or prevent even advanced setups to reach this region. Furthermore, we study the possibility to distinguish between different NME calculations by assuming a positive signal and by combining measurements from different isotopes. Such a discrimination will be impossible if the relative sign of the long- and short-range contribution remains unknown, but can become feasible if m(& beta;& beta;) & GSIM; 40 meV and if the relative sign is known to be positive. Sensitivities will be dominated by the advanced Ge-76 and Xe-136 setups assumed here, but NME model-discrimination improves if data from a third isotope is added, e.g., from Te-130 or Mo-100.
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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). Comparison of inclusive and photon-tagged jet suppression in 5.02 TeV Pb+Pb collisions with ATLAS. Phys. Lett. B, 846, 138154–27pp.
Abstract: Parton energy loss in the quark-gluon plasma (QGP) is studied with a measurement of photon-tagged jet production in 1.7 nb-1 of Pb+Pb data and 260 pb-1 of pp data, both at root sNN = 5.02 TeV, with the ATLAS detector. The process pp -> gamma +jet+X and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum (pT) above 50 GeV and reported as a function of jet pT. This selection results in a sample of jets with a steeply falling pT distribution that are mostly initiated by the showering of quarks. The pp and Pb+Pb measurements are used to report the nuclear modification factor, RAA, and the fractional energy loss, Sloss, for photon-tagged jets. In addition, the results are compared with the analogous ones for inclusive jets, which have a significantly smaller quark-initiated fraction. The RAA and Sloss values are found to be significantly different between those for photon-tagged jets and inclusive jets, demonstrating that energy loss in the QGP is sensitive to the colour-charge of the initiating parton. The results are also compared with a variety of theoretical models of colour-charge-dependent energy loss.
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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 excited tau-leptons and leptoquarks in the final state with tau-leptons and jets in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 06(6), 199–46pp.
Abstract: A search is reported for excited tau-leptons and leptoquarks in events with two hadronically decaying tau-leptons and two or more jets. The search uses proton-proton (pp) collision data at root s = 13 TeV recorded by the ATLAS experiment during the Run 2 of the Large Hadron Collider in 2015-2018. The total integrated luminosity is 139 fb(-1). The excited tau-lepton is assumed to be produced and to decay via a four-fermion contact interaction into an ordinary tau-lepton and a quark-antiquark pair. The leptoquarks are assumed to be produced in pairs via the strong interaction, and each leptoquark is assumed to couple to a charm or lighter quark and a tau-lepton. No excess over the background prediction is observed. Excited tau-leptons with masses below 2.8 TeV are excluded at 95% CL in scenarios with the contact interaction scale Lambda set to 10 TeV. At the extreme limit of model validity where Lambda is set equal to the excited tau-lepton mass, excited tau-leptons with masses below 4.6 TeV are excluded. Leptoquarks with masses below 1.3 TeV are excluded at 95% CL if their branching ratio to a charm quark and a tau-lepton equals 1. The analysis does not exploit flavour-tagging in the signal region.
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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). Observation of the B+ → Jψη'K+ decay. J. High Energy Phys., 08(8), 174–27pp.
Abstract: The B+ -> J psi eta'K+ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13TeV, corresponding to a total integrated luminosity of 9 fb(-1). The branching fraction of this decay is measured relative to the known branching fraction of the B+ -> psi(2S)K+ decay and found to be B(B+ -> J psi eta'K+)/B(B+ -> psi(2S)K+) = (4.91 +/- 0.47 +/- 0.29 +/- 0.07) x 10(-2), where the first uncertainty is statistical, the second is systematic and the third is related to external branching fractions. A first look at the J/psi eta' mass distribution is performed and no signal of intermediate resonances is observed.
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