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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Measurement of the CKM angle gamma in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> K(S)(0)h(+)h(-). J. High Energy Phys., 02(2), 169–36pp.
Abstract: A measurement of CP-violating observables is performed using the decays B-+/- -> DK +/- and B-+/- -> D pi(+/-), where the D meson is reconstructed in one of the self-conjugate three-body final states K-S(0)pi(+)pi(-) and (KSK+K-)-K-0 (commonly denoted K(S)(0)h(+)h(-)). The decays are analysed in bins of the D-decay phase space, leading to a measurement that is independent of the modelling of the D-decay amplitude. The observables are inter- preted in terms of the CKM angle gamma. Using a data sample corresponding to an integrated luminosity of 9 fb(-1) collected in proton-proton collisions at centre-of mass energies of 7, 8, and 13 TeV with the LHCb experiment, gamma is measured to be (68.7(-5.1)(+5.2))degrees. The hadronic parameters r(B)(DK), r(B)(D pi), delta(DK)(B), and delta(D pi)(B), which are the ratios and strong-phase differences of the suppressed and favoured B-+/- decays, are also reported.
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Valdes-Cortez, C., Ballester, F., Vijande, J., Gimenez, V., Gimenez-Alventosa, V., Perez-Calatayud, J., et al. (2020). Depth-dose measurement corrections for the surface electronic brachytherapy beams of an Esteya(R) unit: a Monte Carlo study. Phys. Med. Biol., 65(24), 245026–12pp.
Abstract: Three different correction factors for measurements with the parallel-plate ionization chamber PTW T34013 on the Esteya electronic brachytherapy unit have been investigated. This chamber type is recommended by AAPM TG-253 for depth-dose measurements in the 69.5 kV x-ray beam generated by the Esteya unit. Monte Carlo simulations using the PENELOPE-2018 system were performed to determine the absorbed dose deposited in water and in the chamber sensitive volume at different depths with a Type A uncertainty smaller than 0.1%. Chamber-to-chamber differences have been explored performing measurements using three different chambers. The range of conical applicators available, from 10 to 30 mm in diameter, has been explored. Using a depth-independent global chamber perturbation correction factor without a shift of the effective point of measurement yielded differences between the absorbed dose to water and the corrected absorbed dose in the sensitive volume of the chamber of up to 1% and 0.6% for the 10 mm and 30 mm applicators, respectively. Calculations using a depth-dependent perturbation factor, including or excluding a shift of the effective point of measurement, resulted in depth-dose differences of about +/- 0.5% or less for both applicators. The smallest depth-dose differences were obtained when a shift of the effective point of measurement was implemented, being displaced 0.4 mm towards the center of the sensitive volume of the chamber. The correction factors were obtained with combined uncertainties of 0.4% (k = 2). Uncertainties due to chamber-to-chamber differences are found to be lower than 2%. The results emphasize the relevance of carrying out detailed Monte Carlo studies for each electronic brachytherapy device and ionization chamber used for its dosimetry.
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HAWC Collaboration(Albert, A. et al), & Salesa Greus, F. (2021). A Survey of Active Galaxies at TeV Photon Energies with the HAWC Gamma-Ray Observatory. Astrophys. J., 907(2), 67–18pp.
Abstract: The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory continuously detects TeV photons and particles within its large field of view, accumulating every day a deeper exposure of two-thirds of the sky. We analyzed 1523 days of HAWC live data acquired over four and a half years, in a follow-up analysis of 138 nearby (z < 0.3) active galactic nuclei from the Third Catalog of Hard Fermi-LAT sources culminating within 40 degrees of the zenith at Sierra Negra, the HAWC site. This search for persistent TeV emission used a maximum-likelihood analysis assuming intrinsic power-law spectra attenuated by pair production of gamma-ray photons with the extragalactic background light. HAWC clearly detects persistent emission from Mkn 421 and Mkn 501, the two brightest blazars in the TeV sky, at 65 sigma and 17 sigma level, respectively. Marginal evidence, just above the 3 sigma level, was found for three other known very high-energy emitters: the radio galaxy M87 and the BL Lac objects VER J0521+211 and 1ES 1215+303, the latter two at z similar to 0.1. We find a 4.2 sigma evidence for collective emission from the set of 30 previously reported very high-energy sources, with Mkn 421 and Mkn 501 excluded. Upper limits are presented for the sample under the power-law assumption and in the predefined (0.5-2.0), (2.0-8.0), and (8.0-32.0) TeV energy intervals.
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HAWC Collaboration(Albert, A. et al), & Salesa Greus, F. (2021). Evidence of 200 TeV Photons from HAWC J1825-134. Astrophys. J. Lett., 907(2), L30–9pp.
Abstract: The Earth is bombarded by ultrarelativistic particles, known as cosmic rays (CRs). CRs with energies up to a few PeV (=10(15) eV), the knee in the particle spectrum, are believed to have a Galactic origin. One or more factories of PeV CRs, or PeVatrons, must thus be active within our Galaxy. The direct detection of PeV protons from their sources is not possible since they are deflected in the Galactic magnetic fields. Hundred TeV gamma-rays from decaying pi(0), produced when PeV CRs collide with the ambient gas, can provide the decisive evidence of proton acceleration up to the knee. Here we report the discovery by the High Altitude Water Cerenkov (HAWC) observatory of the gamma-ray source, HAWC J1825-134, whose energy spectrum extends well beyond 200 TeV without a break or cutoff. The source is found to be coincident with a giant molecular cloud. The ambient gas density is as high as 700 protons cm(-3). While the nature of this extreme accelerator remains unclear, CRs accelerated to energies of several PeV colliding with the ambient gas likely produce the observed radiation.
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Pajtler, M. V. et al, & Gadea, A. (2021). Excited states of Y-90,Y-92,Y-94 populated in Zr-90+Pb-208 multinucleon transfer reaction. Phys. Scr., 96(3), 035305–7pp.
Abstract: Multinucleon transfer reactions in Zr-90+Pb-208 have been studied via fragment-gamma coincidences, employing the PRISMA magnetic spectrometer coupled to the CLARA gamma-array. An analysis on Y isotopes has been carried out incorporating spectroscopic as well as reaction mechanism aspects. New gamma transitions have been observed in Y-94, confirming the findings of recent studies where nuclei were produced via fission of uranium, and a comparison with near-by Y-90,Y-92 isotopes populated in the same reaction has been discussed. Experimental cross sections have been extracted and compared with the GRAZING calculations, showing a fair agreement along the neutron pick-up side. The results confirm how multinucleon transfer reactions are a suitable mechanism for the study of neutron-rich nuclei.
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