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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). Search for flavour-changing neutral-current interactions of a top quark and a gluon in pp collisions at root s=13 TeV with the ATLAS detector. Eur. Phys. J. C, 82(4), 334–35pp.
Abstract: A search is presented for the production of a single top quark via left-handed flavour-changing neutralcurrent (FCNC) interactions of a top quark, a gluon and an up or charm quark. Two production processes are considered: u + g -> t and c + g -> t. The analysis is based on proton-proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. The data set corresponds to an integrated luminosity of 139 fb(-1). Events with exactly one electron or muon, exactly one b-tagged jet and missing transverse momentum are selected, resembling the decay products of a singly produced top quark. Neural networks based on kinematic variables differentiate between events from the two signal processes and events from background processes. The measured data are consistent with the background-only hypothesis, and limits are set on the production cross-sections of the signal processes: sigma(u + g -> t) x B(t -> Wb) x B(W -> l nu) < 3.0 pb and sigma(c + g -> t) xB(t -> Wb) xB(W -> l nu) < 4.7pb at the 95% confidence level, with B(W -> l nu) = 0.325 being the sum of branching ratios of all three leptonic decay modes of the W boson. Based on the framework of an effective field theory, the cross-section limits are translated into limits on the strengths of the tug and tcg couplings occurring in the theory: vertical bar C-uG(ut)vertical bar Lambda(2) < 0.057 TeV-2 and vertical bar C-uG(ct)vertical bar Lambda(2) < 0.14 TeV-2. These bounds correspond to limits on the branching ratios of FCNC-induced top-quark decays: B(t -> u + g) < 0.61 x 10(-4) and B(t -> c + g) < 3.7 x 10(-4).
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Botella, F. J., Branco, G. C., Rebelo, M. N., Silva-Marcos, J. I., & Bastos, J. F. (2022). Decays of the heavy top and new insights on epsilon(K) in a one-VLQ minimal solution to the CKM unitarity problem. Eur. Phys. J. C, 82(4), 360–16pp.
Abstract: We propose a minimal extension of the Standard Model where an up-type vector-like quark, denoted T, is introduced and provides a simple solution to the CKM unitarity problem. We adopt the Botella-Chau parametrization in order to extract the 4 x 3 quark mixing matrix which contains the three angles of the 3 x 3 CKM matrix plus three new angles denoted theta(14), theta(24), theta(34). It is assumed that the mixing of T with standard quarks is dominated by theta(14). Imposing a recently derived, and much more restrictive, upper-bound on the New Physics contributions to epsilon(K) , we find, in the limit of exact theta(14) dominance where the other extra angles vanish, that epsilon(NP)(K) is too large. However, if one relaxes the exact theta(14) dominance limit, there exists a parameter region, where one may obtain epsilon(NP)(K) in agreement with experiment while maintaining the novel pattern of T decays with the heavy quark decaying predominantly to the light quarks d and u. We also find a reduction in the decay rate of K-L -> pi(0)nu(nu) over bar.
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Camarda, S., Cieri, L., & Ferrera, G. (2022). Fiducial perturbative power corrections within the q(T) subtraction formalism. Eur. Phys. J. C, 82(6), 575–8pp.
Abstract: We consider higher-order QCD corrections to the production of high-mass systems in hadron collisions within the transverse-momentum (q(T)) subtraction formalism. We present amethod to consistently remove the linear power corrections in q(T) which appears when fiducial kinematical cuts are applied on the final state system. We consider explicitly the case of fiducial cross sections for Drell-Yan lepton pair production at the Large Hadron Collider up to next-to-nextto-next-to-leading order (N3LO) in QCD. We have implemented our method within the DYTurbo numerical program and we have obtained perturbative predictions which are in agreement at the permille level with those obtained with local subtraction formalisms up to the next-to-next-toleading order (NNLO). At the N3LO we are able to provide predictions for fiducial cross sections with numerical accuracy at the permille level.
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Capozzi, F., & Petcov, S. T. (2022). Neutrino tomography of the Earth with ORCA detector. Eur. Phys. J. C, 82(5), 461–23pp.
Abstract: Using PREM as a reference model for the Earth density distribution we investigate the sensitivity of ORCA detector to deviations of the Earth (i) outer core (OC) density, (ii) inner core (IC) density, (iii) total core density, and (iv) mantle density, from their respective PREM densities. The analysis is performed by studying the effects of the Earth matter on the oscillations of atmospheric nu(mu), nu(e), (nu) over bar (mu) and (nu) over bar (e). We present results which illustrate the dependence of the ORCA sensitivity to the OC, IC, core and mantle densities on the type of systematic uncertainties used in the analysis, on the value of the atmospheric neutrino mixing angle theta(23), on whether the Earth mass constraint is implemented or not, and on the way it is implemented, and on the type – with normal ordering (NO) or inverted ordering (IO) – of the light neutrino mass spectrum. We show, in particular, that in the “most favorable” NO case of implemented Earth mass constraint, “minimal” systematic errors and sin(2) theta(23) = 0.58, ORCA can determine, e.g., the OC (mantle) density at 3 sigma C.L. after 10 years of operation with an uncertainty of (- 18%)/+ 15% (of (- 6%)/+ 8%). In the “most disfavorable” NO case of “conservative” systematic errors and sin(2) theta(23) = 0.42, the uncertainty on OC (mantle) density reads (- 43%)/+ 39% ((- 17%/+ 20%), while for for sin(2) theta(23) = 0.50 and 0.58 it is noticeably smaller: (- 37)%/+ 30% and (- 30%)/+ 24% ((- 13%)/+ 16% and (- 11%/+ 14%)). We find also that the sensitivity of ORCA to the OC, core and mantle densities is significantly worse for IO neutrino mass spectrum.
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Dai, L. R., Oset, E., & Geng, L. S. (2022). The D-s(+)->pi(+KSKS0)-K-0 reaction and the I=1 partner of the f(0)(1710) state. Eur. Phys. J. C, 82(3), 225–9pp.
Abstract: We have identified the decay modes of the D-s(+)-> pi K+*K+*(-),pi+K*(0)(K) over bar*(0) reactions producing a pion and two vector mesons. The posterior vector-vector interaction generates two resonances that we associate to the f(0)(1710) and the a(0)(1710) recently claimed, and they decay to the observed K+K- or (KSKS0)-K-0 pair, leading to the reactions D-s(+)->pi+K+K-,pi(+KSKS0)-K-0. The results depend on two parameters related to external and internal emission. We determine a narrow region of the parameters consistent with the large N-c limit within uncertainties which gives rise to decay widths in agreement with experiment. With this scenario we make predictions for the branching ratio of the a(0)(1710) contribution to the D-s(+)->pi(K+KS0)-K-0 reaction, finding values within the range of (1.3 +/- 0.4)x10(-3). Comparison of these predictions with coming experimental results on that latter reaction will be most useful to deepen our understanding on the nature of these two resonances.
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