A
bstract
This paper presents a search for a new
Z
′ resonance decaying into a pair of dark quarks which hadronise into dark hadrons before promptly decaying back as Standard Model particles. This ...analysis is based on proton-proton collision data recorded at
s
= 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb
−
1
. After selecting events containing large-radius jets with high track multiplicity, the invariant mass distribution of the two highest-transverse-momentum jets is scanned to look for an excess above a data-driven estimate of the Standard Model multijet background. No significant excess of events is observed and the results are thus used to set 95% confidence-level upper limits on the production cross-section times branching ratio of the
Z
′ to dark quarks as a function of the
Z
′ mass for various dark-quark scenarios.
ATLAS measured the centrality dependence of the dijet yield using 165 nb^{-1} of p+Pb data collected at sqrts_{NN}=8.16 TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, ...is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, R_{CP}, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The R_{CP} shows a scaling with the Bjorken x of the parton originating from the proton, x_{p}, while no such trend is observed as a function of x_{Pb}. This analysis provides unique input to understanding the role of small proton spatial configurations in p+Pb collisions by covering parton momentum fractions from the valence region down to x_{p}∼10^{-3} and x_{Pb}∼4×10^{-4}.
Angular correlations between heavy quarks provide a unique probe of the quark-gluon plasma created in ultrarelativistic heavy-ion collisions. Results are presented of a measurement of the azimuthal ...angle correlations between muons originating from semileptonic decays of heavy quarks produced in 5.02 TeV Pb+Pb and pp collisions at the LHC. The muons are measured with transverse momenta and pseudorapidities satisfying p_{T}^{μ}>4 GeV and |η^{μ}|<2.4, respectively. The distributions of azimuthal angle separation Δϕ for muon pairs having pseudorapidity separation |Δη|>0.8, are measured in different Pb+Pb centrality intervals and compared to the same distribution measured in pp collisions at the same center-of-mass energy. Results are presented separately for muon pairs with opposite-sign charges, same-sign charges, and all pairs. A clear peak is observed in all Δϕ distributions at Δϕ∼π, consistent with the parent heavy-quark pairs being produced via hard-scattering processes. The widths of that peak, characterized using Cauchy-Lorentz fits to the Δϕ distributions, are found to not vary significantly as a function of Pb+Pb collision centrality and are similar for pp and Pb+Pb collisions. This observation will provide important constraints on theoretical descriptions of heavy-quark interactions with the quark-gluon plasma.
Electromiography (EMG) plays a key role in the evaluation of patients with neuromuscular diseases. It can be considered an extension of the neurological examination. So it must be individualized and ...based on differential diagnosis. We have analized data about EMG performed in a period of four months in the Unit of Neurophysiopatology of University of Bari and Foggia. Data collected show that in this period we have received 807 EMG bookings: we have performed 604 exams (75%) of whom 405 exams had pertinence with differential diagnosis (50%), 199 (25%) had no pertinence; 203 patients (25%) did not turn up for the exam. At Neurophysiopathology of Foggia we have received 540 EMG booking: we have performed 504 neurophysiological studies. In the total amount of EMG performed 326 had pertinence (60%), 178 had no pertinence (33%) and 36 patients did not turn up for the exam (7%). Data collected show that physicians, medical practictioners, neurologists and other specialists share similar difficulties to make a correct differential diagnosis in the field of neuromuscular diseases and that EMG can be the most useful test in clarifying the diagnosis only after a correct clinical examination.
