ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., et al. (2022). Measurements of Higgs boson production cross-sections in the H ->tau(+) tau(-) decay channel in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 08(8), 175–81pp.
Abstract: Measurements of the production cross-sections of the Standard Model (SM) Higgs boson (H) decaying into a pair of tau -leptons are presented. The measurements use data collected with the ATLAS detector from pp collisions produced at the Large Hadron Collider at a centre-of-mass energy of p root s = 13TeV, corresponding to an integrated luminosity of 139 fb-1. Leptonic ( tau -> l upsilon(l)upsilon(tau)) and hadronic ( tau -> hadrons upsilon tau) decays of the tau -lepton are considered. All measurements account for the branching ratio of H -> tau tau and are performed with a requirement |yH| < 2.5, where yH is the true Higgs boson rapidity. The cross-section of the pp -> H -> tau tau process is measured to be 2.94 +/- 0.21(stat)+ 0.37 – 0.32(syst) pb, in agreement with the SM prediction of 3.17 +/- 0.09 pb. Inclusive cross-sections are determined separately for the four dominant production modes: 2.65 +/- 0.41(stat)+ 0.91 – 0.67(syst) pb for gluon-gluon fusion, 0.197 +/- 0.028(stat)+ 0.032 – 0.026(syst) pb for vectorboson fusion, 0.115 +/- 0.058(stat)+ 0.042 – 0.040(syst) pb for vector-boson associated production, and 0.033 +/- 0.031(stat)+ 0.022 – 0.017(syst) pb for top-quark pair associated production. Measurements in exclusive regions of the phase space, using the simplified template cross-section framework, are also performed. All results are in agreement with the SM predictions.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., et al. (2022). Direct constraint on the Higgs-charm coupling from a search for Higgs boson decays into charm quarks with the ATLAS detector. Eur. Phys. J. C, 82(8), 717–42pp.
Abstract: A search for the Higgs boson decaying into a pair of charm quarks is presented. The analysis uses proton- proton collisions to target the production of a Higgs boson in association with a leptonically decaying W or Z boson. The dataset delivered by the LHC at a centre-of-mass energy of root s = 13 TeV and recorded by the ATLAS detector corresponds to an integrated luminosity of 139 fb(-1). Flavour-tagging algorithms are used to identify jets originating from the hadronisation of charm quarks. The analysis method is validated with the simultaneous measurement of WW, WZ and ZZ production, with observed (expected) significances of 2.6 (2.2) standard deviations above the background-only prediction for the (W/Z)Z(-> c (c) over bar) process and 3.8 (4.6) standard deviations for the (W/Z)W(-> cq) process. The (WIZ)H(-> c (c) over bar) search yields an observed (expected) upper limit of 26 (31) times the predicted Standard Model crosssection times branching fraction for a Higgs boson with a mass of 125 GeV, corresponding to an observed (expected) constraint on the charm Yukawa coupling modifier vertical bar k(c)vertical bar < 8.5 (12.4), at the 95% confidence level. A combination with the ATLAS (W/Z)H, H -> b<(b)over bar> analysis is performed, allowing the ratio k(c)/k(b) to be constrained to less than 4.5 at the 95% confidence level, smaller than the ratio of the b- and c-quark masses, and therefore determines the Higgs-charm coupling to be weaker than the Higgs-bottom coupling at the 95% confidence level.
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Coito, L., Faubel, C., Herrero-Garcia, J., Santamaria, A., & Titov, A. (2022). Sterile neutrino portals to Majorana dark matter: effective operators and UV completions. J. High Energy Phys., 08(8), 085–36pp.
Abstract: Stringent constraints on the interactions of dark matter with the Standard Model suggest that dark matter does not take part in gauge interactions. In this regard, the possibility of communicating between the visible and dark sectors via gauge singlets seems rather natural. We consider a framework where the dark matter talks to the Standard Model through its coupling to sterile neutrinos, which generate active neutrino masses. We focus on the case of Majorana dark matter, with its relic abundance set by thermal freeze-out through annihilations into sterile neutrinos. We use an effective field theory approach to study the possible sterile neutrino portals to dark matter. We find that both lepton-number-conserving and lepton-number-violating operators are possible, yielding an interesting connection with the Dirac/Majorana character of active neutrinos. In a second step, we open the different operators and outline the possible renormalisable models. We analyse the phenomenology of the most promising ones, including a particular case in which the Majorana mass of the sterile neutrinos is generated radiatively.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., et al. (2022). Observation of WWW Production in pp Collisions at p=13 TeV with the ATLAS Detector. Phys. Rev. Lett., 129(6), 061803–20pp.
Abstract: This Letter reports the observation of WWW production and a measurement of its cross section using detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from WWW production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive WWW production cross section is measured to be 820 ± 100 (stat) ± 80 (syst) fb, approximately 2.6 standard deviations from the predicted cross section of 511 ± 18 fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy.
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KM3NeT Collaboration(Aiello, S. et al), Alves Garre, S., Calvo, D., Carretero, V., Colomer, M., Gozzini, S. R., et al. (2022). Nanobeacon: A time calibration device for the KM3NeT neutrino telescope. Nucl. Instrum. Methods Phys. Res. A, 1040, 167132–13pp.
Abstract: The KM3NeT Collaboration is currently constructing a multi-site high-energy neutrino telescope in the Mediterranean Sea consisting of matrices of pressure-resistant glass spheres, each holding a set of 31 small-area photomultipliers. The main goals of the telescope are the observation of neutrino sources in the Universe and the measurement of the neutrino oscillation parameters with atmospheric neutrinos. A relative time synchronisation between photomultipliers of the nanosecond order needed to guarantee the required angular resolution of the detector. Due to the large detector volumes to be instrumented by KM3NeT, a cost reduction of the different systems is a priority. To this end, the inexpensive Nanobeacon has been designed and developed by the KM3NeT Collaboration to be used for detector time-calibration studies. At present, more than 600 & nbsp;Nanobeacons have been already produced. The characterisation of the optical pulse and the wavelength emission profile of the devices is critical for the time calibration. The optical pulse rise time has been quantified as less than 3 ns, while the Full Width Half Maximum is less than 6 ns. The wavelength drift, due to a variation of the supply voltage, has also been qualified as lower than 10 nm for the full range of the Nanobeacon. In this paper, more details about the main features of the Nanobeacon design, production and operation, together with the main properties of the light pulse generated are described.
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