Abstract: We recall the predictions made ten years ago about a bound state of J(P) = 0(+) in I = 0 of the D*(K) over bar* system, which is manifestly exotic, and we associate it to the X-0(2866) state reported in the recent LHCb experiment. Fine tuning the parameters to reproduce exactly the mass and width of the X-0(2866) state, we report two more states stemming from the same interaction, one with 1(+) and the other with 2(+). For reasons of parity, the 1(+) state cannot be observed in D (K) over bar decay, and we suggest to observe it in the D*(K) over bar spectrum. On the other hand, the 2(+) state can be observed in D (K) over bar decay but the present experiment has too small statistics in the region of its mass to make any claim. We note that measurements of the D*(K) over bar spectrum and of the D (K) over bar with more statistics should bring important information concerning the nature of the X-0(2866) and related ones that could be observed.

Abstract: The integrated fiducial cross-section and unfolded differential jet mass spectrum of high transverse momentum Z -> b (b) over bar decays are measured in Z gamma events in proton-proton collisions at root s = 13 TeV. The data analysed were collected between 2015 and 2016 with the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 36.1 fb(-1). Photons are required to have a transverse momentum p(T) > 175 GeV. The Z -> b (b) over bar decay is reconstructed using a jet with p(T) > 200 GeV, found with the anti-k(t) R = 1.0 jet algorithm, and groomed to remove soft and wide-angle radiation and to mitigate contributions from the underlying event and additional proton-proton collisions. Two different but related measurements are performed using two jet grooming definitions for reconstructing the Z -> b (b) over bar decay: trimming and soft drop. These algorithms differ in their experimental and phenomenological implications regarding jet mass reconstruction and theoretical precision. To identify Zbosons, b-tagged R = 0.2 track-jets matched to the groomed large-R calorimeter jet are used as a proxy for the b-quarks. The signal yield is determined from fits of the data-driven background templates to the different jet mass distributions for the two grooming methods. Integrated fiducial cross-sections and unfolded jet mass spectra for each grooming method are compared with leading-order theoretical predictions. The results are found to be in good agreement with Standard Model expectations within the current statistical and systematic uncertainties.

Abstract: The top anti-top quark production cross-section is measured in the lepton+jets channel using proton-proton collision data at a centre-of-mass energy of root s = 13 TeV collected with the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 139 fb(-1). Events with exactly one charged lepton and four or more jets in the final state, with at least one jet containing b-hadrons, are used to determine the a production cross-section through a profile-likelihood t (t) over bar. The inclusive cross-section is measured to be alpha(inc) = 830 +/- 0.4 (stat.) +/- 36 (syst.) +/- 14 (lumi.) pb with a relative uncertainty of 4.6%. The result is consistent with theoretical calculations at next-to-next-to-leading order in perturbative QCD. The fiducial t (t) over bar cross-section within the experimental acceptance is also measured.