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NEXT Collaboration(Henriques, C. A. O. et al), Benlloch-Rodriguez, J. M., Carcel, S., Carrion, J. V., Diaz, J., Felkai, R., et al. (2022). Neutral Bremsstrahlung Emission in Xenon Unveiled. Phys. Rev. X, 12(2), 021005–23pp.
Abstract: We present evidence of non-excimer-based secondary scintillation in gaseous xenon, obtained using both the NEXT-White time projection chamber (TPC) and a dedicated setup. Detailed comparison with first-principle calculations allows us to assign this scintillation mechanism to neutral bremsstrahlung (NBrS), a process that is postulated to exist in xenon that has been largely overlooked. For photon emission below 1000 nm, the NBrS yield increases from about 10(-2) photon/e(-) cm(-1) bar(-1) at pressure-reduced electric field values of 50 V cm(-1) bar(-1) to above 3 x 10(-1) photon/e(-) cm(-1) bar(-1) at 500 V cm(-1) bar(-1). Above 1.5 kV cm(-1) bar(-1), values that are typically employed for electroluminescence, it is estimated that NBrS is present with an intensity around 1 photon/e(-) cm(-1) bar(-1), which is about 2 orders of magnitude lower than conventional, excimer-based electroluminescence. Despite being fainter than its excimeric counterpart, our calculations reveal that NBrS causes luminous backgrounds that can interfere, in either gas or liquid phase, with the ability to distinguish and/or to precisely measure low primary-scintillation signals (S1). In particular, we show this to be the case in the "buffer region, where keeping the electric field below the electroluminescence threshold does not suffice to extinguish secondary scintillation. The electric field leakage in this region should be mitigated to avoid intolerable levels of NBrS emission. Furthermore, we show that this new source of light emission opens up a viable path toward obtaining S2 signals for discrimination purposes in future single-phase liquid TPCs for neutrino and dark matter physics, with estimated yields up to 20-50 photons/e(-) cm(-1).
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Karuseichyk, I., Sorelli, G., Walschaers, M., Treps, N., & Gessner, M. (2022). Resolving mutually-coherent point sources of light with arbitrary statistics. Phys. Rev. Res., 4(4), 043010–11pp.
Abstract: We analyze the problem of resolving two mutually coherent point sources with arbitrary quantum statistics, mutual phase, and relative and absolute intensity. We use a sensitivity measure based on the method of moments and compare direct imaging with spatial-mode demultiplexing (SPADE), analytically proving advantage of the latter. We show that the moment-based sensitivity of SPADE saturates the quantum Fisher information for all known cases, even for non-Gaussian states of the sources.
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Lasa-Alonso, J., Olmos-Trigo, J., Devescovi, C., Hernandez, P., Garcia-Etxarri, A., & Molina-Terriza, G. (2023). Resonant helicity mixing of electromagnetic waves propagating through matter. Phys. Rev. Res., 5(2), 023116–8pp.
Abstract: Dual scatterers preserve the helicity of an incident field, whereas antidual scatterers flip it completely. In this setting of linear electromagnetic scattering theory, we provide a completely general proof on the nonexistence of passive antidual scatterers. However, we show that scatterers fulfilling the refractive index matching condition flip the helicity of the fields very efficiently without being in contradiction with the law of energy conservation. Moreover, we find that this condition is paired with the impedance matching condition in several contexts of electromagnetism and, in particular, within Fresnel's and Mie's scattering problems. Finally, we show that indexmatched media induce a resonant helicity mixing on the propagating electromagnetic waves. We reach this conclusion by identifying that the refractive index matching condition leads to the phenomenon of avoided crossing.
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Das, B. et al, & Algora, A. (2024). Broken seniority symmetry in the semimagic proton mid-shell nucleus 95Rh. Phys. Rev. Res., 6(2), L022038–7pp.
Abstract: Lifetime measurements of low-lying excited states in the semimagic ( N = 50) nucleus 95 Rh have been performed by means of the fast -timing technique. The experiment was carried out using gamma -ray detector arrays consisting of LaBr 3 (Ce) scintillators and germanium detectors integrated into the DESPEC experimental setup commissioned for the Facility for Antiproton and Ion Research ( FAIR ) Phase -0, Darmstadt, Germany. The excited states in 95 Rh were populated primarily via the /3 decays of 95 Pd nuclei, produced in the projectile fragmentation of a 850 MeV / nucleon 124 Xe beam impinging on a 4 g / cm 2 9 Be target. The deduced electromagnetic E2 transition strengths for the gamma -ray cascade within the multiplet structure depopulating from the isomeric I pi = 21 / 2 + state are found to exhibit strong deviations from predictions of standard shell model calculations which feature approximately conserved seniority symmetry. In particular, the observation of a strongly suppressed E2 strength for the 13 / 2 + -> 9 / 2 + ground state transition cannot be explained by calculations employing standard interactions. This remarkable result may require revision of the nucleon-nucleon interactions employed in state-of-the-art theoretical model calculations, and might also point to the need for including three-body forces in the Hamiltonian.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for the Dimuon Decay of the Higgs Boson in pp Collisions at root s=13 TeV with the ATLAS Detector. Phys. Rev. Lett., 119(5), 051802–20pp.
Abstract: A search for the dimuon decay of the Higgs boson was performed using data corresponding to an integrated luminosity of 36.1 fb(-1) collected with the ATLAS detector in pp collisions at root s = 13 TeV at the Large Hadron Collider. No significant excess is observed above the expected background. The observed (expected) upper limit on the cross section times branching ratio is 3.0 (3.1) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125 GeV. When combined with the pp collision data at root s = 7 TeV and root s = 8 TeV, the observed (expected) upper limit is 2.8 (2.9) times the Standard Model prediction.
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