Azimuthal anisotropies of muons from charm and bottom hadron decays are measured in Pb+Pb collisions at √sNN=5.02TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in ...2015 and 2018 with integrated luminosities of 0.5nb−1 and 1.4nb−1, respectively. The kinematic selection for heavy-flavor muons requires transverse momentum 4 < pT < 30GeV and pseudorapidity |η| < 2.0. The dominant sources of muons in this pT range are semi-leptonic decays of charm and bottom hadrons. These heavy-flavor muons are separated from light-hadron decay muons and punch-through hadrons using the momentum imbalance between the measurements in the tracking detector and in the muon spectrometers. Azimuthal anisotropies, quantified by flow coefficients, are measured via the event-plane method for inclusive heavy-flavor muons as a function of the muon pTand in intervals of Pb+Pb collision centrality. Heavy-flavor muons are separated into contributions from charm and bottom hadron decays using the muon transverse impact parameter with respect to the event primary vertex. Non-zero elliptic (v2) and triangular (v3) flow coefficients are extracted for charm and bottom muons, with the charm muon coefficients larger than those for bottom muons for all Pb+Pb collision centralities. The results indicate substantial modification to the charm and bottom quark angular distributions through interactions in the quark-gluon plasma produced in these Pb+Pb collisions, with smaller modifications for the bottom quarks as expected theoretically due to their larger mass.
We present herein new results from Belle on the $\tau^- \rightarrow \pi^-
\nu_{\rm \tau} \ell^+ \ell^- $ branching fraction and from BABAR on the $\tau^-
\rightarrow K^- (0,1,2,3) \pi^0 \nu_{\rm ...\tau}$, $\tau^- \rightarrow \pi^-
(3,4) \pi^0 \nu_{\rm \tau}$ and $\tau^- \rightarrow K^- K^0_{\rm S} \nu_{\rm
\tau}$ branching fractions. From the $K^- K^0_{\rm S}$ mass spectrum we
determine the spectral function. The improved branching fraction measurements
of the $\tau^- \rightarrow K^- (0,1,2,3) \pi^0 \nu_{\rm \tau}$ decays are used
to determine $|V_{\rm us}|$ from $\tau^- \rightarrow X_{\rm s}^- \nu_{\rm
\tau}$ inclusive decays.
A search for a narrow scalar resonance decaying into an opposite-sign muon pair produced in events with and without b-tagged jets is presented in this paper. The search uses 36.1 fb−1 of s√=13 TeV ...proton-proton collision data recorded by the ATLAS experiment at the LHC. No significant excess of events above the expected Standard Model background is observed in the investigated mass range of 0.2 to 1.0 TeV. The observed upper limits at 95% confidence level on the cross section times branching ratio for b-quark associated production and gluon-gluon fusion are between 1.9 and 41 fb and 1.6 and 44 fb respectively, which is consistent with expectations.
A measurement of the associated production of a top-quark pair (t¯t) with a vector boson (W, Z) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented, using 36.1 fb−1 of ...integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. Events are selected in channels with two same- or opposite-sign leptons (electrons or muons), three leptons or four leptons, and each channel is further divided into multiple regions to maximize the sensitivity of the measurement. The t¯tZ and t¯tW production cross sections are simultaneously measured using a combined fit to all regions. The best-fit values of the production cross sections are σt¯tZ ¼ 0.95 0.08stat 0.10syst pb and σt¯tW ¼ 0.87 0.13stat 0.14syst pb in agreement with the Standard Model predictions. The measurement of the t¯tZ cross section is used to set constraints on effective field theory operators which modify the t¯tZ vertex.
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