Low and High Energy Limits of Particle Spectra in QCD Jets

Charged particle energy spectra in e+e- annihilation are compared with the analytical predictions from the QCD evolution equation in the Modified Leading Log Approximation. With the nonperturbative initial condition shifted down to threshold as suggested by the Local Parton Hadron Duality picture a good description of the data from the lowest up to highest available energies results. The two essential parameters in this approach are determined from a moment analysis. The sensitivity of the fit to the running of alpha_s and to the number of active flavours (including a light gluino) is demonstrated. For very high energies the theory predicts a scaling behaviour in certain rescaled variables (``zeta-scaling''). The data show an approximate behaviour of this type in the present energy range and come close to the predicted asymptotic scaling function for the small particle energies.Comment: LaTeX2e, 45 pages, 12 figure

Hadron multiplicity as the limit of jet multiplicity at high resolution

Recently exact numerical results from the evolution equation for parton multiplicities in QCD jets have been obtained. A comparison with various approximate results is presented. A good description is obtained not only of the jet multiplicities measured at LEP-1 but also of the hadron multiplicities for $cms$ energies above 1.6 GeV in \epem annihilation. The solution suggests that a final state hadron can be represented by a jet in the limit of small (nonperturbative) $k_\perp$ cut-off $Q_0$. In this description using as adjustable parameters only the QCD scale $\Lambda$ and the cut-off $Q_0$, the coupling $\alpha_s$ can be seen to rise towards large values above unity at low energies.Comment: LaTex, 4 pages, 2 figures, presented at HEP Int. Euroconf. on Quantum Chromodynamics, Montpellier, July 199

Unified QCD Description of Hadron and Jet Multiplicities

The evolution equation for parton multiplicities in quark and gluon jets which takes into account the soft gluon interference is solved numerically using the initial conditions at threshold. If the k_T-cutoff Q_c is lowered towards the hadronic scale Q_0 of a few hundred MeV, the jets are fully resolved into hadrons. Both hadron and jet multiplicities in e+e- annihilation are well described with a common normalization. Evidence is presented within this perturbative approach that the coupling \alpha_s(k_T) rises by an order of magnitude when approaching the low energy region. The ratio of hadron multiplicities in gluon and quark jets is found smaller than in previous approximate solutions of the evolution equation.Comment: LaTeX, 15 pages, 3 figure

Perturbative QCD description of multiparticle correlations in quark and gluon jets

The QCD evolution equations in Modified Leading Log Approximation for the factorial moments of the multiplicity distribution in quark and gluon jets are numerically solved with initial conditions at threshold by fully taking into account the energy conservation law. After applying Local Parton Hadron Duality as hadronization prescription, a consistent quantitative description of available experimental data for factorial cumulants and factorial moments of arbitrary order and for their ratio both in quark and gluon jets and in $e^+e^-$ annihilation is achieved.Comment: LaTeX, 15 pages, 3 figures, typos corrected in the labels and caption of Figure

Perturbative QCD Description of Mean Jet and Particle Multiplicities in e+e- annihilation

A complete numerical solution of the evolution equation for parton multiplicities in quark and gluon jets with initial conditions at threshold is presented. Data on both hadron and jet multiplicities in e+e- annihilation are well described with a common normalization, giving further support to the picture of Local Parton Hadron Duality. Predictions for LEP-II energies are presented. Furthermore we study the sensitivity to the cutoff parameter Q_0 and the scale of alpha_s.Comment: LaTeX, 7 pages, 3 figures, uses espcrc2.sty, to appear in Proc. of XXVII International Symposium on Multiparticle Dynamics, Frascati, Italy, September 1997, Nucl Phys. B (Proc. Suppl.

Increased use of high-flow nasal cannulas after the pandemic in bronchiolitis: a more severe disease or a changed physician's attitude?

After the SARS-CoV-2 pandemic, we noticed a marked increase in high-flow nasal cannula use for bronchiolitis. This study aims to report the percentage of children treated with high-flow nasal cannula (HFNC) in various seasons. The secondary outcomes were admissions for bronchiolitis, virological results, hospital burden, and NICU/PICU need. We conducted a retrospective study in four Italian hospitals, examining the medical records of all infants (< 12 months) hospitalized for bronchiolitis in the last four winter seasons (1 September-31 March 2018-2022). In the 2021-2022 winter season, 66% of admitted children received HFNC versus 23%, 38%, and 35% in the previous 3 years. A total of 876 patients were hospitalized in the study periods. In 2021-2022, 300 infants were hospitalized for bronchiolitis, 22 in 2020-2021, 259 in 2019-2020, and 295 in 2018-2019. The percentage of patients needing intensive care varied from 28.7% to 18%, 22%, and 15% in each of the four considered periods (p < 0.05). Seventy-seven percent of children received oxygen in the 2021-2022 winter; vs 50%, 63%, and 55% (p < 0.01) in the previous 3 years. NIV/CPAP was used in 23%, 9%, 16%, and 12%, respectively. In 2021-2020, 2% of patients were intubated; 0 in 2020-2021, 3% in 2019-2020, and 1% in 2018-2019