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HAWC Collaboration(Alfaro, R. et al), & Coutiño de Leon, S. (2025). Orbital Modulation of Gamma Rays up to 100 TeV from LS 5039. Astrophys. J. Lett., 987(2), L42–10pp.
Abstract: Gamma-ray binaries are luminous in gamma rays, composed of a compact object orbiting a massive companion star. The interaction between these two objects can drive relativistic outflows, either jets or winds, in which particles can be accelerated to energies reaching hundreds of teraelectronvolts (TeV). However, it is still debated where and under which physical conditions particles are accelerated in these objects and ultimately whether protons can be accelerated up to PeV energies. Among the well-known gamma-ray binaries, LS 5039 is a high-mass X-ray binary with an orbital period of 3.9 days that has been observed up to TeV energies by the High Energy Stereoscopic System. We present new observations of LS 5039 obtained with the High Altitude Water Cherenkov (HAWC) observatory. Our data reveal that the gamma-ray spectrum of LS 5039 extends up to 200 TeV with no apparent spectral cutoff. Furthermore, we confirm, with a confidence level of 4.7 sigma, that the emission between 2 and 118 TeV is modulated by the orbital motion of the system, and find a 2.2 sigma hint of variability above 100 TeV. This indicates that these photons are likely produced within or near the binary orbit, where they can undergo absorption by the stellar photons. In a leptonic scenario, the highest energy photons detected by HAWC can be emitted by similar to 200 TeV electrons inverse Compton scattering stellar photons, which would require an extremely efficient acceleration mechanism operating within LS 5039. Alternatively, a hadronic scenario could explain the data through proton-proton or proton-gamma collisions of protons accelerated to petaelectronvolt energies.
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Arroyo-Ureña, M. A., Ibarra, A., Roig, P., & Valencia-Perez, T. (2025). Prospects for detecting the rare heavy Higgs decay H → hγγ through the H→bbγγ channel at the LHC. J. High Energy Phys., 07(7), 106–25pp.
Abstract: We study the decay of a heavy CP-even neutral Higgs into an on-shell Standard Model-like Higgs boson and two photons, H -> h gamma gamma, in the two-Higgs doublet model. We argue that the decay channel H -> h gamma gamma, followed by the decay of the Standard Model Higgs h -> bb, could be observed at the 5 sigma level at the High-Luminosity LHC for masses of the heavy Higgs up to 950 GeV for the type-II, 650 GeV for the Lepton Specific and the Flipped 2HDMs, and 350 GeV for the type-I. We also discuss the possible role of the decay H -> h gamma gamma in discriminating among different types of 2HDMs and in enhancing the total number of events in the final state H -> bb gamma gamma compared to the cascade decay H -> hh followed by h -> gamma gamma h -> bb with identical final state (although with different kinematical distributions).
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Vijande, J., Johansen, J. G., De Brabandere, M., Hellebust, T. P., Herreros, A., Kirisits, C., et al. (2025). Temporal drift in calibration of Ir-192 brachytherapy sources: A multi-center study on dosimetric discrepancies and metrological consistency. Phys. Imag. Radiat. Oncol., 35, 100801–6pp.
Abstract: Background and purpose: High-dose-rate (HDR) brachytherapy relies on accurate and metrologically traceable source strength determination. Recent anecdotal reports and preliminary studies have suggested a possible temporal drift in the reference air kerma rate (RAKR) measured by clinical users compared to manufacturer certificates for 192Ir sources. This study investigates the existence and magnitude of such drift across a large, multicenter European dataset and explores potential underlying causes. Materials and methods: A total of over 1700 RAKR measurements for HDR and PDR brachytherapy sources, collected over two decades from 29 centers in 10 European countries, were analyzed. The ratio of hospital-measured RAKR to manufacturer-certified RAKR was assessed using linear regression and t-tests to evaluate drift. Data were corrected for center-dependent systematics and segmented around key dates corresponding to changes in primary standards. Supplementary analyses included leave-one-out testing and time-segmented trend assessment. Results: A statistically significant drift (+0.15 %/year) was detected for all 192Ir source types after 2018, correlating temporally with updates in the German Physikalisch-Technische Bundesanstalt (PTB) primary standards laboratory. Removing PTB corrections from manufacturer values nearly eliminated the observed drift. No such trend was observed for 60Co sources. Conclusion: The findings reveal a drift in hospital-to-manufacturer Ir-192 RAKR ratios that is temporally correlated with changes in metrology standards, not uniformly implemented across calibration chains. The true cause is however still unknown. The study aimed to investigate that greater transparency and harmonization among all stakeholders are essential to ensure dosimetric accuracy in HDR brachytherapy.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2025). Search for charged Higgs bosons produced in top-quark decays or in association with top quarks and decaying via H± → τ± ντ in 13 TeV pp collisions with the ATLAS detector. Phys. Rev. D, 111(7), 072006–31pp.
Abstract: Charged Higgs bosons produced either in top-quark decays or in association with a top quark, subsequently decaying via H-+/- -> tau(+/-) nu(tau), are searched for in 140 fb(-1) of proton-proton collision data at root s = 13 TeV recorded with the ATLAS detector. Depending on whether the top quark is produced together with the H-+/- decays hadronically or semileptonically, the search targets tau + jets or tau + lepton final states, in both cases with a tau-lepton decaying into a neutrino and hadrons. No significant excess over the Standard Model background expectation is observed. For the mass range of 80 <= m(H)(+/-) <= 3000 GeV, upper limits at 95% confidence level are set on the production cross section of the charged Higgs boson times the branching fraction B(H-+/- -> tau(+/-) nu(tau)) in the range 4.5 pb-0.4 fb. In the mass range 80-160 GeV, assuming the Standard Model cross section for tt production, this corresponds to upper limits between 0.27% and 0.02% on B(t -> bH(+/-)) x B(H-+/- ->tau(+/-) nu(tau)).
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Miro, C., Nebot, M., & Queiroz, D. (2025). Light states in real multi-Higgs models with spontaneous CP violation. Phys. Rev. D, 111(11), L111703–7pp.
Abstract: In models with extended scalar sectors consisting of multiple Higgs doublets that trigger spontaneous electroweak symmetry breaking, it might be expected that the abundance of dimensionful quadratic couplings in the scalar potential could allow for a regime where, apart from the would-be Goldstone bosons and a neutral Higgs-like state, all new scalars have masses much larger than the electroweak scale. In the case of models where CP invariance holds at the Lagrangian level but is broken by the vacuum, we show that such a reasonable expectation does not hold. When perturbativity requirements are placed on the dimensionless quartic couplings, the spectrum of the new scalars includes one charged and two additional neutral states whose masses cannot be much larger than the electroweak scale.
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