The production of single top quarks and top antiquarks via the $t$-channel exchange of a virtual $W$ boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The full Run 2 data sample recorded with the ATLAS detector in the years 2015-2018 is used, corresponding to an integrated luminosity of 140 fb$^{-1}$. The absolute and normalised production cross-sections are measured differentially as a function of the transverse momentum and absolute rapidity of the top quark and top antiquark. In addition, the ratio of top quark to top antiquark production cross-sections is measured. The measured distributions are compared with next-to-leading-order quantum chromodynamics predictions obtained with different combinations of matrix-element generators, parton-shower programs and proton parton distribution functions, as well as to next-to-next-to-leading-order calculations. Overall, good agreement is observed between the measurements and the theoretical predictions. For most measured distributions, the sensitivity to differences between the predictions is limited by the systematic uncertainties in the measurement. The measured differential distributions are also interpreted in an effective field theory approach to constrain the Wilson-Coefficient $C_{Qq}^{3,1}$ associated with a four-quark operator. The interpretation accounts for the effect of the selection efficiency, which is altered significantly by non-zero contributions from $C_{Qq}^{3,1}$.
------- Overview of the HEPData record ------- Event selection on detector level: one charged lepton with $p_\text{T}(\ell) > 28$ GeV two jets with $p_\text{T}(j) > 30$ GeV and $|\eta(j)|<4\text{.}5$ one b-tag (DL1r, 60% WP) $E_\text{T}^{miss} > 30$ GeV $m_\text{T}(W) > 50$ GeV $p_\text{T}(\ell) > 40$ GeV $\cdot\frac{|\Delta\Phi(j_1,\ell)|}{\pi}$ $m(\ell b) < 160$ GeV ------- The criteria above define the $\ell^{\pm}$ selection ------- $D_{nn}\geq0\text{.}93$ ------- The criteria above define the signal regions $\ell^{\pm}$ SRs ------- Data/MC comparisons: <ul> <li> $\ell^+$ selection (<a href="167734?version=1&table=Figure%202a">Figure 2a</a> ) <li> $\ell^-$ selection (<a href="167734?version=1&table=Figure%202b">Figure 2b</a> ) Variables in the $\ell^{\pm}$ SRs: <li> $p_T(\ell^+\nu b)$ (<a href="167734?version=1&table=Figure%203a">Figure 3a</a> ) <li> $p_T(\ell^-\nu b)$ (<a href="167734?version=1&table=Figure%203b">Figure 3b</a> ) <li> $|y(\ell^+\nu b)|$ (<a href="167734?version=1&table=Figure%203c">Figure 3c</a> ) <li> $|y(\ell^-\nu b)|$ (<a href="167734?version=1&table=Figure%203d">Figure 3d</a> ) Yields in the $\ell^{\pm}$ SRs: <a href="167734?version=1&table=Table%203">Table 3</a> Uncertainy breakdown into categories: Absolute cross sections: <li> $p_T(t)$ (<a href="167734?version=1&table=Figure%204a">Figure 4a</a> ) <li> $p_T(t)$ (<a href="167734?version=1&table=Table%206">Table 6</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Figure%204b">Figure 4b</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Table%207">Table 7</a> ) <li> $|y(t)|$ (<a href="167734?version=1&table=Figure%204c">Figure 4c</a> ) <li> $|y(t)|$ (<a href="167734?version=1&table=Table%208">Table 8</a> ) <li> $|y(\bar{t})|$ (<a href="167734?version=1&table=Figure%204d">Figure 4d</a> ) <li> $|y(\bar{t})|$ (<a href="167734?version=1&table=Table%209">Table 9</a> ) <li> $p_T(t \text{ or }\bar{t})$ (<a href="167734?version=1&table=Figure%204e">Figure 4e</a> ) <li> $p_T(t \text{ or }\bar{t})$ (<a href="167734?version=1&table=Table%2010">Table 10</a> ) <li> $|y(t \text{ or }\bar{t})|$ (<a href="167734?version=1&table=Figure%204f">Figure 4f</a> ) <li> $|y(t \text{ or }\bar{t})|$ (<a href="167734?version=1&table=Table%2011">Table 11</a> ) Normalised cross sections: <li> $p_T(t)$ (<a href="167734?version=1&table=Figure%205a">Figure 5a</a> ) <li> $p_T(t)$ (<a href="167734?version=1&table=Table%2012">Table 12</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Figure%205b">Figure 5b</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Table%2013">Table 13</a> ) <li> $|y(t)|$ (<a href="167734?version=1&table=Figure%205c">Figure 5c</a> ) <li> $|y(t)|$ (<a href="167734?version=1&table=Table%2014">Table 14</a> ) <li> $|y(\bar{t})|$ (<a href="167734?version=1&table=Figure%205d">Figure 5d</a> ) <li> $|y(\bar{t})|$ (<a href="167734?version=1&table=Table%2015">Table 15</a> ) Parton-level cross-sections with full breakdown of uncertainties and theoretical predictions: Absolute cross sections: <li> $p_T(t)$ (<a href="167734?version=1&table=Figure%206a">Figure 6a</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Figure%206b">Figure 6b</a> ) <li> $|y(t)|$ (<a href="167734?version=1&table=Figure%206c">Figure 6c</a> ) <li> $|y(\bar{t})|$ (<a href="167734?version=1&table=Figure%206d">Figure 6d</a> ) <li> $p_T(t \text{ or }\bar{t})$ (<a href="167734?version=1&table=Figure%206e">Figure 6e</a> ) <li> $|y(t \text{ or }\bar{t})|$ (<a href="167734?version=1&table=Figure%206f">Figure 6f</a> ) Normalised cross sections: <li> $p_T(t)$ (<a href="167734?version=1&table=Figure%207a">Figure 7a</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Figure%207b">Figure 7b</a> ) <li> $|y(t)|$ (<a href="167734?version=1&table=Figure%207c">Figure 7c</a> ) <li> $|y(\bar{t})|$ (<a href="167734?version=1&table=Figure%207d">Figure 7d</a> ) $\chi^2$ probabilities for the theoretical predictions: <li> $p_T$ distributions (<a href="167734?version=1&table=Table%204">Table 4</a> ) <li> $|y|$ distributions (<a href="167734?version=1&table=Table%205">Table 5</a> ) Selection efficiencies of the MC EFT signal samples: <li> $p_T(t)$ (<a href="167734?version=1&table=Figure%2014a">Figure 14a</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Figure%2014b">Figure 14b</a> ) Best fits for cross-section dependence on $C_{Qq}^{3,1}$: <a href="167734?version=1&table=Table%2022">Table 22</a> Migration matrices: <li> $p_T(t)$ (<a href="167734?version=1&table=Figure%2016a">Figure 3a</a> ) <li> $p_T(\bar{t})$ (<a href="167734?version=1&table=Figure%2016b">Figure 3b</a> ) <li> $|y(t)|$ (<a href="167734?version=1&table=Figure%2016c">Figure 3c</a> ) <li> $|y(\bar{t})|$ (<a href="167734?version=1&table=Figure%2016d">Figure 3d</a> ) Additional material (in order of entries): Unscaled event yields in both SRs: <li> (<a href="167734?version=1&table=Event%20yields%20%24%5Cell%5E%2B%24%20SR%20no%20SFs"> $\ell^+$ SR </a> ) <li> (<a href="167734?version=1&table=Event%20yields%20%24%5Cell%5E-%24%20SR%20no%20SFs"> $\ell^-$ SR </a> ) Statistical covariance matrices for all measurements: Absolute cross sections: <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24p_%5Ctext%7BT%7D(t)%24%20absolute"> $p_T(t)$ </a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24p_%5Ctext%7BT%7D(%5Cbar%7Bt%7D)%24%20absolute"> $p_T(\bar{t})$</a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24%7Cy(t)%7C%24%20absolute"> $|y(t)|$</a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24%7Cy(%5Cbar%7Bt%7D)%7C%24%20absolute"> $|y(\bar{t})|$</a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24p_%5Ctext%7BT%7D(t%20%5C%2C%20%5Ctext%7Bor%7D%5C%2C%20%20%5Cbar%7Bt%7D)%24"> $p_T(t \text{ or }\bar{t})$</a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24%7Cy(t%20%5C%2C%20%5Ctext%7Bor%7D%5C%2C%20%20%5Cbar%7Bt%7D)%7C%24"> $|y(t \text{ or }\bar{t})|$</a> ) Normalised cross sections: <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24p_%5Ctext%7BT%7D(t)%24%20normalised"> $p_T(t)$ </a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24p_%5Ctext%7BT%7D(%5Cbar%7Bt%7D)%24%20normalised" > $p_T(\bar{t})$ </a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24%7Cy(t)%7C%24%20normalised"> $|y(t)|$ </a> ) <li> (<a href="167734?version=1&table=Statistical%20covariance%20%24%7Cy(%5Cbar%7Bt%7D)%7C%24%20normalised"> $|y(\bar{t})|$ </a> ) Statistical cross-correlation between variables: Absolute cross sections: <li> (<a href="167734?version=1&table=Cross%20correlation%20%24tq%24%20absolute"> $tq$ </a> ) <li> (<a href="167734?version=1&table=Cross%20correlation%20%24%5Cbar%7Bt%7Dq%24%20absolute"> $\bar{t}q$</a> ) Normalised cross sections: <li> (<a href="167734?version=1&table=Cross%20correlation%20%24tq%24%20normalised"> $tq$ </a> ) <li> (<a href="167734?version=1&table=Cross%20correlation%20%24%5Cbar%7Bt%7Dq%24%20normalised"> $\bar{t}q$ </a> ) Full covariance matrices for all measurements: Absolute cross sections: <li> (<a href="167734?version=1&table=Covariance%20%24p_%5Ctext%7BT%7D(t)%24%20absolute"> $p_T(t)$ </a> ) <li> (<a href="167734?version=1&table=Covariance%20%24p_%5Ctext%7BT%7D(%5Cbar%7Bt%7D)%24%20absolute"> $p_T(\bar{t})$</a> ) <li> (<a href="167734?version=1&table=Covariance%20%24%7Cy(t)%7C%24%20absolute"> $|y(t)|$</a> ) <li> (<a href="167734?version=1&table=Covariance%20%24%7Cy(%5Cbar%7Bt%7D)%7C%24%20absolute"> $|y(\bar{t})|$</a> ) <li> (<a href="167734?version=1&table=Covariance%20%24p_%5Ctext%7BT%7D(t%20%5C%2C%20%5Ctext%7Bor%7D%5C%2C%20%20%5Cbar%7Bt%7D)%24"> $p_T(t \text{ or }\bar{t})$</a> ) <li> (<a href="167734?version=1&table=Covariance%20%24%7Cy(t%20%5C%2C%20%5Ctext%7Bor%7D%5C%2C%20%20%5Cbar%7Bt%7D)%7C%24"> $|y(t \text{ or }\bar{t})|$</a> ) Normalised cross sections: <li> (<a href="167734?version=1&table=Covariance%20%24p_%5Ctext%7BT%7D(t)%24%20normalised"> $p_T(t)$ </a> ) <li> (<a href="167734?version=1&table=Covariance%20%24p_%5Ctext%7BT%7D(%5Cbar%7Bt%7D)%24%20normalised"> $p_T(\bar{t})$ </a> ) <li> (<a href="167734?version=1&table=Covariance%20%24%7Cy(t)%7C%24%20normalised"> $|y(t)|$ </a> ) <li> (<a href="167734?version=1&table=Covariance%20%24%7Cy(%5Cbar%7Bt%7D)%7C%24%20normalised"> $|y(\bar{t})|$ </a> ) Statistical uncertainty on systematic uncertainties evaluated with the bootstrap method: Absolute cross sections: <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24p_%5Ctext%7BT%7D(t)%24%20absolute"> $p_T(t)$ </a> ) <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24p_%5Ctext%7BT%7D(%5Cbar%7Bt%7D)%24%20absolute"> $p_T(\bar{t})$</a> ) <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24%7Cy(t)%7C%24%20absolute"> $|y(t)|$</a> ) <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24%7Cy(%5Cbar%7Bt%7D)%7C%24%20absolute"> $|y(\bar{t})|$</a> ) Normalised cross sections: <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24p_%5Ctext%7BT%7D(t)%24%20normalised"> $p_T(t)$ </a> ) <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24p_%5Ctext%7BT%7D(%5Cbar%7Bt%7D)%24%20normalised"> $p_T(\bar{t})$ </a> ) <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24%7Cy(t)%7C%24%20normalised"> $|y(t)|$ </a> ) <li> (<a href="167734?version=1&table=Bootstrap%20systematics%20%24%7Cy(%5Cbar%7Bt%7D)%7C%24%20normalised"> $|y(\bar{t})|$ </a> )
Post-fit agreement between data and the expected distributions in events containing a positively charged lepton. The experimental, background-related and MC statistical uncertainties are incorporated in the uncertainty bands. The region $D_{nn} > 0.93$ is excluded from the fit.
Post-fit agreement between data and the expected distributions in events containing a negatively charged lepton. The experimental, background-related and MC statistical uncertainties are incorporated in the uncertainty bands. The region $D_{nn} > 0.93$ is excluded from the fit.
Production fraction ratios of B$^+$, B$^0$, and B$^0_\mathrm{s}$ mesons are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV using a special data set recorded in 2018 with high-rate triggers designed to collect an unbiased sample of $10^{10}$ b hadrons with the CMS experiment at the LHC. These data allow the use of the open-charm decays of B mesons (B$_\mathrm{(s)}$$\to$$π$D$_\mathrm{(s)}$) where the D meson decays into fully hadronic final states. Production fraction ratios as functions of B meson transverse momentum ($p_\mathrm{T}$) and rapidity ($y$) are measured using the open-charm decays in the kinematic range of 8 $\lt$$p_\mathrm{T}$$\lt$ 60 GeV and $\lvert y \rvert$$\lt$ 2.25. In addition, the same data are used to measure the relative production fraction ratios with the charmonium decay channels (B$_\mathrm{(s)}$$\to$ X$\,$J/$ψ$ with X indicating a K$^+$, K$^*$(892)$^0$, or $ϕ$(1020) meson) with the J/$ψ$ meson decaying into a pair of muons. By utilizing known branching fractions, precision theoretical calculations, and the open-charm results, the production fraction ratios in the charmonium samples are determined with an absolute normalization for the first time. These results also improve several world-average values of the ratios of branching fractions of B meson decays to charmonium and open-charm states. Finally, we test isospin invariance in B meson production in proton-proton collisions and observe that it holds within the experimental precision.
The invariant mass distribution of $B^+$ candidates, corrected using the $D^0$ meson mass, is shown for $13 < p_{T} < 18$ GeV along with the corresponding fit.
The invariant mass distribution of $B^0$ candidates, corrected using the $D^-$ meson mass, is shown for $18 < p_{T} < 23$ GeV along with the corresponding fit.
The invariant mass distribution of $B_s^{0}$ candidates, corrected using the $D^-_{s}$ meson mass, is shown for $23 < p_{T} < 28$ GeV along with the corresponding fit.
This analysis presents an observation of the photon-fusion production of W boson pairs using the CMS detector at the LHC. The total cross section of the W$^+$W$^-$ production in photon fusion is measured using proton-proton collision data with an integrated luminosity of 138 fb$^{-1}$ collected with the CMS detector in 2016$-$2018 at a center-of-mass energy of $\sqrt{s}$ = 13 TeV. Events are selected in the final state with one isolated electron and one isolated muon, and no additional tracks associated with the electron-muon production vertex. The total and fiducial production cross sections are 643$^{+82}_{-78}$ fb and 3.96$^{+0.53}_{-0.51}$ fb, respectively, in agreement with the standard model predictions of 631 $\pm$ 126 fb and 3.87 $\pm$ 0.77 fb. This agreement enables stringent constraints to be imposed on anomalous quartic gauge couplings within a dimension-8 effective field theory framework.
Normalized simulated $N_{tracks}$ distributions for signal and background processes.
Normalized simulated acoplanarity distributions for signal and background processes. The acoplanarity distribution is shown for events with $N_{tracks}=0$.
Observed and predicted $p_{T}^{e\mu}$ distributions for events with $N_{tracks}=0$, using 2016--2018 data. The distributions are shown after the maximum likelihood fit to the data ('postfit distributions'). The observed data and their associated Poissonian statistical uncertainty are shown with black markers with vertical error bars. The uncertainty band accouts for all sources of background and signal uncertainty, systematic as well as statistical, after the fit. The last bin includes the overflow. The lower panels show the ratio of data to sum of signal and background contributions, before (prefit, open red circles) and after (black full markers) the maximum likelihood fit.
Differential top quark pair production cross sections are measured in the dilepton final states e$^+$e$^-$, $μ^+μ^-$, and e$^\pmμ^\mp$, as a function of kinematic variables of the two-neutrino system: the transverse momentum $p_\mathrm{T}^{νν}$ of the dineutrino system, the minimum distance in azimuthal angle between $\vec{p}_\mathrm{T}^{\,νν}$ and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The measured cross sections are unfolded to the particle level using an unregularized least squares method. Results are compared with predictions by the standard model of particle physics, and found to be in agreement with theoretical calculations as well as Monte Carlo simulations.
Data and MC simulation yields after the event selection, combined for all data-taking periods and split by channels. The uncertainties on the expected yields include systematic and statistical uncertainties. The relative contribution in percent of each process to the total expected yield of a channel is given in parentheses.
Observed (black markers) and expected distributions of leading lepton $p_{T}$ after event selection. The hatched (grey) areas denote the systematic (total) uncertainties in the expected yields. Events from all data-taking periods and all channels are combined. The lower panel of each plot shows the ratio between observed and expected distributions. The last bin includes all events above the plotted range. The entry Background corresponds to the sum of all the SM predictions.
Observed (black markers) and expected distributions of leading jet $p_{T}$ after event selection. The hatched (grey) areas denote the systematic (total) uncertainties in the expected yields. Events from all data-taking periods and all channels are combined. The lower panel of each plot shows the ratio between observed and expected distributions. The last bin includes all events above the plotted range. The entry Background corresponds to the sum of all the SM predictions.
This paper reports the first measurement of the transverse momentum ($p_{\mathrm{T}}$) spectra of primary charged pions, kaons, (anti)protons, and unidentified particles as a function of the charged-particle flattenicity in pp collisions at $\sqrt{s}=13$ TeV. Flattenicity is a novel event shape observable that is measured in the pseudorapidity intervals covered by the V0 detector, $2.8<\eta<5.1$ and $-3.7<\eta<-1.7$. According to QCD-inspired phenomenological models, it shows sensitivity to multiparton interactions and is less affected by biases toward larger $p_{\mathrm{T}}$ due to local multiplicity fluctuations in the V0 acceptance than multiplicity. The analysis is performed in minimum-bias (MB) as well as in high-multiplicity events up to $p_{\mathrm{T}}=20$ GeV/$c$. The event selection requires at least one charged particle produced in the pseudorapidity interval $|\eta|<1$. The measured $p_{\mathrm{T}}$ distributions, average $p_{\mathrm{T}}$, kaon-to-pion and proton-to-pion particle ratios, presented in this paper, are compared to model calculations using PYTHIA 8 based on color strings and EPOS LHC. The modification of the $p_{\mathrm{T}}$-spectral shapes in low-flattenicity events that have large event activity with respect to those measured in MB events develops a pronounced peak at intermediate $p_{\mathrm{T}}$ ($2<p_{\mathrm{T}}<8$ GeV/$c$), and approaches the vicinity of unity at higher $p_{\mathrm{T}}$. The results are qualitatively described by PYTHIA, and they show different behavior than those measured as a function of charged-particle multiplicity based on the V0M estimator.
Transverse momentum spectrum of $\pi^{+} + \pi^{-}$ measured at midrapidity ($|y|<0.5$) in INEL>0 pp collisions at $\sqrt{s}$ = 13 TeV for different flattenicity event classes selected with the V0M estimator at forward rapidity (top figure, upper panel)
Transverse momentum spectrum of $K^{+} + K^{-}$ measured at midrapidity ($|y|<0.5$) in INEL>0 pp collisions at $\sqrt{s}$ = 13 TeV for different flattenicity event classes selected with the V0M estimator at forward rapidity (top figure, upper panel)
Transverse momentum spectrum of $p + \overline{p}$ measured at midrapidity ($|y|<0.5$) in INEL>0 pp collisions at $\sqrt{s}$ = 13 TeV for different flattenicity event classes selected with the V0M estimator at forward rapidity (top figure, upper panel)
The production yields of antideuterons and antiprotons are measured in pp collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV, as a function of transverse momentum ($p_{\rm T}$) and rapidity ($y$), for the first time rapidity-differentially up to $|y|= 0.7$. The measured spectra are used to study the $p_{\rm T}$ and rapidity dependence of the coalescence parameter $B_2$, which quantifies the coalescence probability of antideuterons. The $p_{\rm T}$ and rapidity dependence of the obtained $B_2$ is extrapolated for $p_{\rm T}> 1.7$ GeV/$c$ and $|y|>0.7$ using the phenomenological antideuteron production model implemented in PYTHIA 8.3 as well as a baryon coalescence afterburner model based on EPOS 3. Such measurements are of interest to the astrophysics community, since they can be used for the calculation of the flux of antinuclei from cosmic rays, in combination with coalescence models.
Transverse momentum spectra of antideuterons measured in pp collisions at centre-of-mass per nucleon-nucleon energy of 13 TeV, as shown in Fig. 1 (right panel). Rapidity interval 0 to 0.1.
Transverse momentum spectra of antideuterons measured in pp collisions at centre-of-mass per nucleon-nucleon energy of 13 TeV, as shown in Fig. 1 (right panel). Rapidity interval 0.1 to 0.2.
Transverse momentum spectra of antideuterons measured in pp collisions at centre-of-mass per nucleon-nucleon energy of 13 TeV, as shown in Fig. 1 (right panel). Rapidity interval 0.2 to 0.3.
Measurements of (anti)deuteron and (anti)$^3$He production in the rapidity range $ |y| < $ 0.5 as a function of the transverse momentum and event multiplicity in Xe$-$Xe collisions at a center-of-mass energy per nucleon$-$nucleon pair of $\sqrt{s_{\rm NN}}$ = 5.44 TeV are presented. The coalescence parameters $B_2$ and $B_3$ are measured as a function of the transverse momentum per nucleon. The ratios between (anti)deuteron and (anti)$^3$He yields and those of (anti)protons and pions are reported as a function of the mean charged-particle multiplicity density, and compared with two implementations of the statistical hadronization model and with coalescence predictions. The elliptic flow of (anti)deuterons is measured for the first time in Xe$-$Xe collisions and shows features similar to those already observed in Pb$-$Pb collisions, i.e., the mass ordering at low transverse momentum and the meson$-$baryon grouping at intermediate transverse momentum. The production of nuclei is particularly sensitive to the chemical freeze-out temperature of the system created in the collision, which is extracted from a grand-canonical-ensemble-based thermal fit, performed for the first time including light nuclei along with light-flavor hadrons in Xe$-$Xe collisions. The extracted chemical freeze-out temperature $T_{\rm chem}$ = (154.2 $\pm$ 1.1) MeV in Xe$-$Xe collisions is similar to that observed in Pb$-$Pb collisions and close to the crossover temperature predicted by lattice quantum chromodynamics calculations.
Transverse momentum spectra of 3He nuclei measured in Xe--Xe collisions at centre-of-mass per nucleon-nucleon energy of 5.44 TeV, as shown in Fig. 3 (right panel).
Transverse momentum spectra of deuterons measured in Xe--Xe collisions at centre-of-mass per nucleon-nucleon energy of 5.44 TeV, as shown in Fig. 3 (left panel). Centrality class 0 to 10 percent.
Transverse momentum spectra of deuterons measured in Xe--Xe collisions at centre-of-mass per nucleon-nucleon energy of 5.44 TeV, as shown in Fig. 3 (left panel). Centrality class 10 to 20 percent.
The polarizations of prompt and non-prompt J$/\psi$ and $\psi$(2S) mesons are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to a total integrated luminosity of 103.3 fb$^{-1}$. Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, $\lambda_\theta$, is measured as a function of the transverse momentum, $p_\mathrm{T}$, of the charmonium states, in the 25-120 and 20-100 GeV ranges for the J$/\psi$ and $\psi$(2S), respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for $p_\mathrm{T}$$\gtrsim$ 25 GeV, the non-prompt J$/\psi$ and $\psi$(2S) are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse polarizations, even for $p_\mathrm{T}$ exceeding 30 times the J$/\psi$ mass, where $\lambda_\theta$ tends to an asymptotic value around 0.3. Taken together with previous measurements, by CMS and LHCb at $\sqrt{s}$ = 7 TeV, the prompt polarizations show a significant variation with $p_\mathrm{T}$, at low $p_\mathrm{T}$.
prompt $\mathrm{J}\mspace{-2mu}/\mspace{-2mu}\psi$ $\lambda_\theta$
non prompt $\mathrm{J}\mspace{-2mu}/\mspace{-2mu}\psi$ $\lambda_\theta$
prompt $\psi(2S)$ $\lambda_\theta$
The transverse-momentum ($p_{\rm T}$) spectra and coalescence parameters $B_2$ of (anti)deuterons are measured in pp collisions at $\sqrt{s} = 13$ TeV for the first time in and out of jets. In this measurement, the direction of the leading particle with the highest $p_{\rm T}$ in the event ($p_{\rm T}^{\rm{ lead}} > 5$ GeV/$c$) is used as an approximation for the jet axis. The event is consequently divided into three azimuthal regions and the jet signal is obtained as the difference between the Toward region, that contains jet fragmentation products in addition to the underlying event (UE), and the Transverse region, which is dominated by the UE. The coalescence parameter in the jet is found to be approximately a factor of 10 larger than that in the underlying event. This experimental observation is consistent with the coalescence picture and can be attributed to the smaller average phase-space distance between nucleons inside the jet cone as compared to the underlying event. The results presented in this Letter are compared to predictions from a simple nucleon coalescence model, where the phase space distributions of nucleons are generated using PYTHIA 8 with the Monash 2013 tuning, and to predictions from a deuteron production model based on ordinary nuclear reactions with parametrized energy-dependent cross sections tuned on data. The latter model is implemented in PYTHIA 8.3. Both models reproduce the observed large difference between in-jet and out-of-jet coalescence parameters, although the almost flat trend of the $B^{\rm Jet}_2$ is not reproduced by the models, which instead give a decreasing trend.
Transverse momentum spectra for the transverse azimuthal regions. Events with a leading track with PT>5 GEV at midrapidity are selected. The spectrum is shown in Figure 1 (left panel).
Transverse momentum spectra for the toward azimuthal regions. Events with a leading track with PT>5 GEV at midrapidity are selected. The spectrum is shown in Figure 1 (left panel).
Transverse momentum spectra for the away azimuthal regions. Events with a leading track with PT>5 GEV at midrapidity are selected. The spectrum is shown in Figure 1 (left panel).
The production of K$^*$(892)$^\pm$ meson resonance is measured at midrapidity ($|y|<0.5$) in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV using the ALICE detector at the LHC. The resonance is reconstructed via its hadronic decay channel K$^*$(892)$^\pm \rightarrow \rm{K^0_S \pi^\pm}$. The transverse momentum distributions are obtained for various centrality intervals in the $p_{\rm T}$ range of 0.4-16 GeV/$c$. The reported measurements of integrated yields, mean transverse momenta, and particle yield ratios are consistent with previous ALICE measurements for K$^*$(892)$^0$. The $p_{\rm T}$-integrated yield ratio 2K$^*$(892)$^\pm$/($\rm{K^+ + K^-}$) in central Pb-Pb collisions shows a significant suppression (9.3$\sigma$) relative to pp collisions. Thermal model calculations overpredict the particle yield ratio. Although both simulations consider the hadronic phase, only HRG-PCE accurately represents the measurements, whereas MUSIC+SMASH tends to overpredict them. These observations, along with the kinetic freeze-out temperatures extracted from the yields of light-flavored hadrons using the HRG-PCE model, indicate a finite hadronic phase lifetime, which increases towards central collisions. The $p_{\rm T}$-differential yield ratios 2K$^*$(892)$^\pm$/($\rm{K^+ + K^-}$) and 2K$^*$(892)$^\pm$/($\rm{\pi^+ + \pi^-}$) are suppressed by up to a factor of five at $p_{\rm T}<2$ GeV/$c$ in central Pb-Pb collisions compared to pp collisions at $\sqrt{s} =$ 5.02 TeV. Both particle ratios and are qualitatively consistent with expectations for rescattering effects in the hadronic phase. The nuclear modification factor shows a smooth evolution with centrality and is below unity at $p_{\rm T}>8$ GeV/$c$, consistent with measurements for other light-flavored hadrons. The smallest values are observed in most central collisions, indicating larger energy loss of partons traversing the dense medium.
$p_{\rm T}$-distributions of $\rm{K}^{*}$ (average of particle and anti-particle) meson measured in Pb-Pb collisions at \sqrt{s_{NN}}$ = 5.02 TeV for 0-10\% centrality.
$p_{\rm T}$-distributions of $\rm{K}^{*}$ (average of particle and anti-particle) meson measured in Pb-Pb collisions at \sqrt{s_{NN}}$ = 5.02 TeV for 10-20\% centrality.
$p_{\rm T}$-distributions of $\rm{K}^{*}$ (average of particle and anti-particle) meson measured in Pb-Pb collisions at \sqrt{s_{NN}}$ = 5.02 TeV for 20-40\% centrality.