This article presents measurements of the $t$-channel single top-quark ($t$) and top-antiquark ($\bar{t}$) total production cross sections $\sigma(tq)$ and $\sigma(\bar{t}q)$, their ratio $R_{t}=\sigma(tq)/\sigma(\bar{t}q)$, and a measurement of the inclusive production cross section $\sigma(tq + \bar{t}q)$ in proton--proton collisions at $\sqrt{s} = 7$ TeV at the LHC. Differential cross sections for the $tq$ and $\bar{t}q$ processes are measured as a function of the transverse momentum and the absolute value of the rapidity of $t$ and $\bar{t}$, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of 4.59 fb$^{-1}$. Selected events contain one charged lepton, large missing transverse momentum, and two or three jets. The cross sections are measured by performing a binned maximum-likelihood fit to the output distributions of neural networks. The resulting measurements are $\sigma(tq)= 46\pm 6\; \mathrm{pb}$, $\sigma(\bar{t}q)= 23 \pm 4\; \mathrm{pb}$, $R_{t}=2.04\pm 0.18$, and $\sigma(tq + \bar{t}q)= 68 \pm 8\; \mathrm{pb}$, consistent with the Standard Model expectation. The uncertainty on the measured cross sections is dominated by systematic uncertainties, while the uncertainty on $R_{t}$ is mainly statistical. Using the ratio of $\sigma(tq + \bar{t}q)$ to its theoretical prediction, and assuming that the top-quark-related CKM matrix elements obey the relation $|V_{tb}|\gg |V_{ts}|, |V_{td}|$, we determine $|V_{tb}|=1.02 \pm 0.07$.
Detailed list of the contribution of each source of uncertainty to the total relative uncertainty on the measured $\dfrac{\mathrm{d}\sigma}{\mathrm{d}|y(t)|}$ distribution given in percent for each bin. The list includes only those uncertainties that contribute with more than $1\%$. The following uncertainties contribute to the total uncertainty with less than $1\%$ to each bin content$:$ JES detector, JES statistical, JES physics modeling, JES mixed detector and modeling, JES close-by jets, JES pileup, JES flavor composition, JES flavor response, jet-vertex fraction, $b/\bar{b}$ acceptance, $E_{\mathrm{T}}^{\mathrm{miss}}$ modeling, $W+$ jets shape variation, $t \bar{t}$ generator, $t \bar{t}$ ISR/FSR, and unfolding. In cases when the uncertainty is report to be "$<1\%$" in the table of the paper the uncertainty is approximated by a value of $0.5\%$.
Detailed list of the contribution of each source of uncertainty to the total relative uncertainty on the measured $\dfrac{1}{\sigma}\dfrac{\mathrm{d}\sigma}{\mathrm{d}|y(\bar t)|}$ distribution given in percent for each bin. The list includes only those uncertainties that contribute with more than $1\%$. Sign switches within one uncertainty are denoted with $\mp$ and $\pm$. The following uncertainties contribute to the total uncertainty with less than $1\%$ to each bin content $:$ JES detector, JES statistical, JES physics modeling, JES mixed detector and modeling, JES close-by jets, JES pileup, JES flavor composition, JES flavor response, b-JES, jet energy resolution, jet-vertex fraction, $b/\bar{b}$ acceptance, $b-$tagging efficiency, $c-$ tagging efficiency, mistag efficiency, $E_{\mathrm{T}}^{\mathrm{miss}}$ modeling, lepton uncertainties, $W+$ jets shape variation, $t \bar{t}$ generator, $t \bar{t}$ ISR/FSR, and unfolding. In cases when the uncertainty is report to be "$<1\%$" in the table of the paper the uncertainty is approximated by a value of $0.5\%$.
The elliptic azimuthal anisotropy coefficient ($v_2$) is measured for charm (D$^0$) and strange (K$_\mathrm{S}^0$, $\Lambda$, $\Xi^-$, and $\Omega^-$) hadrons, using a data sample of pPb collisions collected by the CMS experiment, at a nucleon-nucleon center-of-mass energy $\sqrt{s_{_\mathrm{NN}}} =$ 8.16 TeV. A significant positive $v_2$ signal from long-range azimuthal correlations is observed for all particle species in high-multiplicity pPb collisions. The measurement represents the first observation of possible long-range collectivity for open heavy flavor hadrons in small systems. The results suggest that charm quarks have a smaller $v_2$ than the lighter quarks, probably reflecting a weaker collective behavior. This effect is not seen in the larger PbPb collision system at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV, also presented.
The elliptic flow per constituent quark after correcting back-to-back jet contribution, $v_{2}^{sub}/n_{q}$, for $K^{0}_{S}$ as a function of transverse kinetic energy per constituent quark $KE_{T}/n_{q}$ in pPb collision at 8.16 TeV.
The elliptic flow per constituent quark after correcting back-to-back jet contribution, $v_{2}^{sub}/n_{q}$, for $\Lambda$ as a function of transverse kinetic energy per constituent quark $KE_{T}/n_{q}$ in pPb collision at 8.16 TeV.
The elliptic flow per constituent quark after correcting back-to-back jet contribution, $v_{2}^{sub}/n_{q}$, for $\Xi^{-}$ as a function of transverse kinetic energy per constituent quark $KE_{T}/n_{q}$ in pPb collision at 8.16 TeV.
Measurements of two- and multi-particle angular correlations in pp collisions at sqrt(s) = 5, 7, and 13 TeV are presented as a function of charged-particle multiplicity. The data, corresponding to integrated luminosities of 1.0 inverse picobarn (5 TeV), 6.2 inverse picobarns (7 TeV), and 0.7 inverse picobarns (13 TeV), were collected using the CMS detector at the LHC. The second-order (v[2]) and third-order (v[3]) azimuthal anisotropy harmonics of unidentified charged particles, as well as v[2] of K0 short and Lambda/anti-Lambda particles, are extracted from long-range two-particle correlations as functions of particle multiplicity and transverse momentum. For high-multiplicity pp events, a mass ordering is observed for the v[2] values of charged hadrons (mostly pions), K0 short, and Lambda/anti-Lambda, with lighter particle species exhibiting a stronger azimuthal anisotropy signal below pt of about 2 GeV/c. For 13 TeV data, the v[2] signals are also extracted from four- and six-particle correlations for the first time in pp collisions, with comparable magnitude to those from two-particle correlations. These observations are similar to those seen in pPb and PbPb collisions, and support the interpretation of a collective origin for the observed long-range correlations in high-multiplicity pp collisions.
The elliptic flow, $v_{2}(2, |\Delta\eta| > 2)$, as a function of $p_{T}$ for $\Lambda/\bar{\Lambda}$.
The elliptic flow per constituent quark after correcting for back-to-back jet correlations, $v_{2}^{sub}(2, |\Delta\eta| > 2)/n_{q}$, as a function of transverse kinetic energy per constituent quark $KE_{T}/n_{q}$ for $K^{0}_{S}$.
The elliptic flow per constituent quark after correcting for back-to-back jet correlations, $v_{2}^{sub}(2, |\Delta\eta| > 2)$, as a function of transverse kinetic energy per constituent quark $KE_{T}/n_{q}$ for $\Lambda/\bar{\Lambda}$.
Results on two-particle angular correlations for charged particles produced in pp collisions at a center-of-mass energy of 13 TeV are presented. The data were taken with the CMS detector at the LHC and correspond to an integrated luminosity of about 270 inverse nanobarns. The correlations are studied over a broad range of pseudorapidity (abs(eta) < 2.4) and over the full azimuth (phi) as a function of charged particle multiplicity and transverse momentum (pt). In high-multiplicity events, a long-range (abs(Delta eta) > 2.0), near-side (Delta phi approximately 0) structure emerges in the two-particle Delta eta-Delta phi correlation functions. The magnitude of the correlation exhibits a pronounced maximum in the range 1.0 < pt < 2.0 GeV/c and an approximately linear increase with the charged particle multiplicity, with an overall correlation strength similar to that found in earlier pp data at sqrt(s) = 7 TeV. The present measurement extends the study of near-side long-range correlations up to charged particle multiplicities of N[ch] approximately 180, a region so far unexplored in pp collisions. The observed long-range correlations are compared to those seen in pp, pPb, and PbPb collisions at lower collision energies.
Correlated yield obtained with the ZYAM procedure as a function of $|\Delta\Phi|$, averaged over 2 $<|\Delta\eta|<$ 4 in for 2.0 $<p_{T}<$ 3.0 $GeV/c$ and 90 $<N_{offline}^{trk}<$ 105 bins for pp data at $\sqrt =$ 7 $TeV$. The $p_{T}$ selection applies to both particles in the pair. Only statistical uncertainties are given. The subtracted ZYAM constant is given ($C_{ZYAM}$).
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