High-momentum two-particle correlations are a useful tool for studying jet-quenching effects in the quark-gluon plasma. Angular correlations between neutral-pion triggers and charged hadrons with transverse momenta in the range 4--12~GeV/$c$ and 0.5--7~GeV/$c$, respectively, have been measured by the PHENIX experiment in 2014 for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$~GeV. Suppression is observed in the yield of high-momentum jet fragments opposite the trigger particle, which indicates jet suppression stemming from in-medium partonic energy loss, while enhancement is observed for low-momentum particles. The ratio and differences between the yield in Au$+$Au collisions and $p$$+$$p$ collisions, $I_{AA}$ and $\Delta_{AA}$, as a function of the trigger-hadron azimuthal separation, $\Delta\phi$, are measured for the first time at the Relativistic Heavy Ion Collider. These results better quantify how the yield of low-$p_T$ associated hadrons is enhanced at wide angle, which is crucial for studying energy loss as well as medium-response effects.
Per-trigger jet-pair yield as a function of $\Delta\phi$ for selected $\pi^0$ trigger and charged-hadron-associated $p_T$ combinations (${{p_{T,\pi^0}} \otimes p_{T,h}}$) in Au$+$Au collisions. Systematic uncertainties for background subtraction and global scale uncertainties are given.
Integrated away-side $I_{AA}$ as a function of $p_T^h$. Systematic uncertainties for background subtraction and global scale uncertainties are given.
Differential away-side a function of Deltaphi 0%-20% collisions. Systematic uncertainties for background subtraction and global scale uncertainties are given.
A search for a new charged particle X with mass between 0.3 and 2.0 TeV decaying to a W boson and a photon is presented, using proton-proton collision data at a center-of-mass energy of 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb$^{-1}$. Particle X has electric charge $\pm$ 1 and is assumed to have spin 0. The search is performed using the electron and muon decays of the W boson. No significant excess above the predicted background is observed. The upper limit at 95% confidence level on the product of the production cross section of the X and its branching fraction to a W boson and a photon is found to be 94 (137) fb for a 0.3 TeV resonance and 0.75 (0.81) fb for a 2.0 TeV resonance, for an X width-to-mass ratio of 0.01% (5%). This search presents the most stringent constraints to date on the existence of such resonances across the probed mass range. A statistical combination with an earlier study based on the hadronic decay mode of the W boson is also performed, and the upper limit at 95% confidence level for a 2.0 TeV resonance is reduced to 0.50 (0.63) fb for an X width-to-mass ratio of 0.01% (5%).
The red, blue, and orange curves are the product of detector acceptance and analysis selections efficiency for different particle mass assumptions---300, 1000, and 2000 GeV, respectively---to pass sequential requirements, for the electron channel.
The red, blue, and orange curves are the product of detector acceptance and analysis selections efficiency for different particle mass assumptions---300, 1000, and 2000 GeV, respectively---to pass sequential requirements, for the muon channel.
The product of detector acceptance and analysis selection efficiency in the electron channel as functions of the particle X mass. Three analysis requirements are applied consecutively: event reconstruction, HLT, and final signal selection. The product of detector acceptance and analysis selection efficiencies are shown at each stage in red, blue, and orange, respectively.
Measurements at $\sqrt{s}$ = 13.6 TeV of the opposite-sign W boson pair production cross section in proton-proton collisions are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of 34.8 fb$^{-1}$. Events are selected by requiring one electron and one muon of opposite charge. A maximum likelihood fit is performed on signal- and background-enriched data categories defined by the flavour and charge of the leptons, the number of jets, and number of jets originating from b quarks. An inclusive W$^+$W$^-$ production cross section of 125.7 $\pm$ 5.6 pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event. For first time in proton-proton collisions, WW events with at least two reconstructed jets are studied and compared with recent theoretical predictions.
Summary of inclusive cross section.
Summary of inclusive cross section.
Relative systematic uncertainties in the total cross section measurement.
Entanglement is an intrinsic property of quantum mechanics and is predicted to be exhibited in the particles produced at the Large Hadron Collider. A measurement of the extent of entanglement in top quark-antiquark ($\mathrm{t\bar{t}}$) events produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed with the data recorded by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 36.3 fb$^{-1}$. The events are selected based on the presence of two leptons with opposite charges and high transverse momentum. An entanglement-sensitive observable $D$ is derived from the top quark spin-dependent parts of the $\mathrm{t\bar{t}}$ production density matrix and measured in the region of the $\mathrm{t\bar{t}}$ production threshold. Values of $D$$\lt$$-$1/3 are evidence of entanglement and $D$ is observed (expected) to be $-$0.480 $^{+0.026}_{-0.029}$$(-$0.467 $^{+0.026}_{-0.029})$ at the parton level. With an observed significance of 5.1 standard deviations with respect to the non-entangled hypothesis, this provides observation of quantum mechanical entanglement within $\mathrm{t\bar{t}}$ pairs in this phase space. This measurement provides a new probe of quantum mechanics at the highest energies ever produced.
Expected and observed values for the entanglement proxy D in the parton-level phase space of $m(\mathrm{t\bar{t}}) < 400$ and $\beta_z(\mathrm{t\bar{t}}) < 0.9$ when including contributions from the ground state of toponium, $\eta_{\mathrm{t}}$. The first uncertainty is the statistical uncertainty whereas the second uncertainty is the systematic uncertainty.
Expected and observed values for the entanglement proxy D in the parton-level phase space of $m(\mathrm{t\bar{t}}) < 400$ and $\beta_z(\mathrm{t\bar{t}}) < 0.9$ when excluding contributions from the ground state of toponium, $\eta_{\mathrm{t}}$. The first uncertainty is the statistical uncertainty whereas the second uncertainty is the systematic uncertainty.
Expected values from various Monte Carlo predictions for the entanglement proxy D in the parton-level phase space of $m(\mathrm{t\bar{t}}) < 400$ and $\beta_z(\mathrm{t\bar{t}}) < 0.9$ both when excluding and including contributions from the ground state of toponium, $\eta_{\mathrm{t}}$. The first uncertainty is the Monte Carlo statistical uncertainty whereas the second uncertainty is the systematic uncertainty which includes PDF and scale uncertainties.
Weakly interacting massive particles (WIMPs) may interact with a virtual pion that is exchanged between nucleons. This interaction channel is important to consider in models where the spin-independent isoscalar channel is suppressed. Using data from the first science run of the LUX-ZEPLIN dark matter experiment, containing 60 live days of data in a 5.5~tonne fiducial mass of liquid xenon, we report the results on a search for WIMP-pion interactions. We observe no significant excess and set an upper limit of $1.5\times10^{-46}$~cm$^2$ at a 90% confidence level for a WIMP mass of 33~GeV/c$^2$ for this interaction.
WIMP-Pion interaction cross section at the 90% CL
The azimuthal correlation angle, $\Delta\phi$, between the scattered lepton and the leading jet in deep inelastic $e^{\pm}p$ scattering at HERA has been studied using data collected with the ZEUS detector at a centre-of-mass energy of $\sqrt{s} = 318 \;\mathrm{GeV}$, corresponding to an integrated luminosity of $326 \;\mathrm{pb}^{-1}$. A measurement of jet cross sections in the laboratory frame was made in a fiducial region corresponding to photon virtuality $10 \;\mathrm{GeV}^2 < Q^2 < 350 \;\mathrm{GeV}^2$, inelasticity $0.04 < y < 0.7$, outgoing lepton energy $E_e > 10 \;\mathrm{GeV}$, lepton polar angle $140^\circ < \theta_e < 180^\circ$, jet transverse momentum $2.5 \;\mathrm{GeV} < p_\mathrm{T,jet} < 30 \;\mathrm{GeV}$, and jet pseudorapidity $-1.5 < \eta_\mathrm{jet} < 1.8$. Jets were reconstructed using the $k_\mathrm{T}$ algorithm with the radius parameter $R = 1$. The leading jet in an event is defined as the jet that carries the highest $p_\mathrm{T,jet}$. Differential cross sections, $d\sigma/d\Delta\phi$, were measured as a function of the azimuthal correlation angle in various ranges of leading-jet transverse momentum, photon virtuality and jet multiplicity. Perturbative calculations at $\mathcal{O}(\alpha_{s}^2)$ accuracy successfully describe the data within the fiducial region, although a lower level of agreement is observed near $\Delta\phi \rightarrow \pi$ for events with high jet multiplicity, due to limitations of the perturbative approach in describing soft phenomena in QCD. The data are equally well described by Monte Carlo predictions that supplement leading-order matrix elements with parton showering.
<b>Note: in the paper, uncertainties are given in relative terms. The HEPData table contains absolute numbers. The original data file, containing relative uncertainties as in the paper, is available via the 'Resources' button above.</b> Inclusive measurement of the differential cross sections, $d\sigma/d\Delta\phi$, as obtained from the data, ARIADNE MC simulations, and perturbative calculations at $\mathcal{O}(\alpha_{s})$ and $\mathcal{O}(\alpha_{s}^{2})$ accuracy. The effect of initial- and final-state radiation has been corrected in data, based on a simulation study performed in the RAPGAP framework. The quantities $\delta_\mathrm{stat}$ and $\delta_\mathrm{syst}$ represent the statistical and systematic uncertainties relative to the central value, respectively. The uncertainty in the luminosity measurement ($1.9\%$) is not included in these values. The quantities $\delta(\mathcal{O}(\alpha_{s}^{k}))$ represent the combined uncertainty of the scale dependence in the calculation and the model dependence in the hadronisation correction in the $\mathcal{O}(\alpha_{s}^{k})$ calculations.
<b>Note: in the paper, uncertainties are given in relative terms. The HEPData table contains absolute numbers. The original data file, containing relative uncertainties as in the paper, is available via the 'Resources' button above.</b> Differential cross sections, $d\sigma/d\Delta\phi$, in the $p_{T,jet}^{lead}$ region of $2.5 \;\mathrm{GeV} < p_{T,jet}^{lead} < 7 \;\mathrm{GeV}$ for $N_{jet} \geq 1$, as obtained from the data, ARIADNE MC simulations, and perturbative calculations at $\mathcal{O}(\alpha_{s})$ and $\mathcal{O}(\alpha_{s}^{2})$ accuracy. Other details are as in the caption to Table 1.
<b>Note: in the paper, uncertainties are given in relative terms. The HEPData table contains absolute numbers. The original data file, containing relative uncertainties as in the paper, is available via the 'Resources' button above.</b> Differential cross sections, $d\sigma/d\Delta\phi$, in the $p_{T,jet}^{lead}$ region of $2.5 \;\mathrm{GeV} < p_{T,jet}^{lead} < 7 \;\mathrm{GeV}$ for $N_{jet} \geq 2$, as obtained from the data, ARIADNE MC simulations, and perturbative calculations at $\mathcal{O}(\alpha_{s})$ and $\mathcal{O}(\alpha_{s}^{2})$ accuracy. Other details are as in the caption to Table 1.
This Letter presents the first measurement of event-by-event fluctuations of the net number (difference between the particle and antiparticle multiplicities) of multistrange hadrons $\Xi^-$ and $\overline{\Xi}^+$ and its correlation with the net-kaon number using the data collected by the ALICE Collaboration in pp, p$-$Pb, and Pb$-$Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}=5.02\ \mathrm{TeV}$. The statistical hadronization model with a correlation over three units of rapidity between hadrons having the same and opposite strangeness content successfully describes the results. On the other hand, string-fragmentation models that mainly correlate strange hadrons with opposite strange quark content over a small rapidity range fail to describe the data.
Pearson correlation coefficient between the net-$\Xi$ number and net-K number, $\rho_{\Delta\Xi\Delta\mathrm{K}}$, in pp collisions at $\sqrt{s} = 5.02$ TeV
Pearson correlation coefficient between the net-$\Xi$ number and net-K number, $\rho_{\Delta\Xi\Delta\mathrm{K}}$, in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV
Pearson correlation coefficient between the net-$\Xi$ number and net-K number, $\rho_{\Delta\Xi\Delta\mathrm{K}}$, in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV
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 first measurement of $_{\Lambda}^{3}\mathrm{H}$ and $^3_ {\overline{\Lambda}}\overline{\mathrm{H}}$ differential production with respect to transverse momentum and centrality in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$~TeV is presented. The $_{\Lambda}^{3}\mathrm{H}$ has been reconstructed via its two-charged-body decay channel, i.e., $_{\Lambda}^{3}\mathrm{H} \rightarrow {}^{3}\mathrm{He} + \pi^{-}$. A Blast-Wave model fit of the $p_{\rm T}$-differential spectra of all nuclear species measured by the ALICE collaboration suggests that the $_{\Lambda}^{3}\mathrm{H}$ kinetic freeze-out surface is consistent with that of other nuclei. The ratio between the integrated yields of $_{\Lambda}^{3}\mathrm{H}$ and $^3\mathrm{He}$ is compared to predictions from the statistical hadronisation model and the coalescence model, with the latter being favoured by the presented measurements.
Transverse momentum distributions of (anti)hypertriton in 0-10% V0M centrality class
Transverse momentum distributions of (anti)hypertriton in 10-30% V0M centrality class
Transverse momentum distributions of (anti)hypertriton in 30-50% V0M centrality class
First measurements of hadron(h)$-\Lambda$ azimuthal angular correlations in p$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV using the ALICE detector at the Large Hadron Collider are presented. These correlations are used to separate the production of associated $\Lambda$ baryons into three different kinematic regions, namely those produced in the direction of the trigger particle (near-side), those produced in the opposite direction (away-side), and those whose production is uncorrelated with the jet axis (underlying event). The per-trigger associated $\Lambda$ yields in these regions are extracted, along with the near- and away-side azimuthal peak widths, and the results are studied as a function of associated particle $p_{\rm T}$ and event multiplicity. Comparisons with the DPMJET event generator and previous measurements of the $\phi(1020)$ meson are also made. The final results indicate that strangeness production in the highest multiplicity p$-$Pb collisions is enhanced relative to low multiplicity collisions in both the jet-like regions and the underlying event. The production of $\Lambda$ relative to charged hadrons is also enhanced in the underlying event when compared to the jet-like regions. Additionally, the results hint that strange quark production in the away-side of the jet is modified by soft interactions with the underlying event.
Azimuthal distribution of the per-trigger h-$\Lambda$ yield with trigger transverse momentum between 4 and 8 GeV/c and associated transverse momentum between 1.5 and 2.5 GeV/c for 0-20% multiplicity class p-Pb collisions
Azimuthal distribution of the per-trigger h-$\Lambda$ yield with trigger transverse momentum between 4 and 8 GeV/c and associated transverse momentum between 1.5 and 2.5 GeV/c for 20-50% multiplicity class p-Pb collisions
Azimuthal distribution of the per-trigger h-$\Lambda$ yield with trigger transverse momentum between 4 and 8 GeV/c and associated transverse momentum between 1.5 and 2.5 GeV/c for 50-80% multiplicity class p-Pb collisions
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