A search for the pair production of heavy spin-1/2 or spin-3/2 resonances (t$^*$) in proton-proton collisions at $\sqrt{s}$ = 13 TeV is presented. Data collected with the CMS detector at the CERN LHC from 2016 to 2018 corresponding to an integrated luminosity of 138 fb$^{-1}$ are used. The analysis targets benchmark signal scenarios where one t$^*$ decays into a top quark (t) and a photon ($γ$), and the other into a t quark and a gluon (g), i.e., pp $\to$ t$^*\bar{\mathrm{t}}^*$$\to$ tt$γ$g. All-hadronic final states from the t pair decay chain are selected using jet substructure techniques. The signal is probed as a function of the t$^*$ candidate mass, which is reconstructed using the photon and a top quark candidate jet. No significant deviation from the background-only hypothesis is found. Observed (expected) upper limits on the signal cross section at 95% confidence level are set, excluding masses of spin-1/2 t$^*$ particles below 930 (930) GeV and spin-3/2 t$^*$ particles below 1330 (1390) GeV. This analysis marks the first search for heavy resonances in the $\mathrm{t\bar{t}}γ$g channel. Exploiting the high-energy photon to reduce the backgrounds, this search achieves sensitivity competitive with pp $\to$ t$^*\mathrm{\bar{t}}^*$ $\to$ $\mathrm{t\bar{t}}γ$g searches for spin-1/2 t$^*$ despite the small expected t$^*$ $\to$ t$γ$ branching fraction.
The background-only prefit $p_{T}^{\gamma}$ distributions in SR is shown. Statistical and systematic uncertainties in the expected background yields depicted by the hatched band. Additionally, the simulated signal distributions for spin-1/2 and spin-3/2 t* with mass of 900 GeV are overlaid for comparison, with both samples normalized to a cross section of 10 fb. The last bin includes the overflow.
The background-only prefit $p_{T}^{j_{1}}$ distributions in SR is shown. Statistical and systematic uncertainties in the expected background yields depicted by the hatched band. Additionally, the simulated signal distributions for spin-1/2 and spin-3/2 t* with mass of 900 GeV are overlaid for comparison, with both samples normalized to a cross section of 10 fb. The last bin includes the overflow.
The background-only prefit $p_{T}^{\gamma}$ distributions in VR1 is shown. Statistical and systematic uncertainties in the expected background yields depicted by the hatched band. Additionally, the simulated signal distributions for spin-1/2 and spin-3/2 t* with mass of 900 GeV are overlaid for comparison, with both samples normalized to a cross section of 10 fb. The last bin includes the overflow.
High-energy partons lose energy while propagating through the hot, strongly interacting medium produced in ultrarelativistic nucleus-nucleus collisions, leading to a suppression of particle production at high transverse momentum ($p_\mathrm{T}$). The dependence of this energy loss on the size of the colliding nuclear system has yet to be firmly established experimentally. This Letter presents a systematic study of charged-particle suppression across four different nucleus-nucleus collision systems using nuclear modification factors ($R_\mathrm{AA}$) measured by the CMS Collaboration at the CERN LHC. Previous CMS measurements of $R_\mathrm{AA}$ in oxygen-oxygen, xenon-xenon, and lead-lead collisions are recast with identical $p_\mathrm{T}$ intervals and are complemented by the first measurement of the charged-particle $R_\mathrm{AA}$ in neon-neon collisions at $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV. The neon-neon data correspond to an integrated luminosity of 0.76 nb$^{-1}$. The $R_\mathrm{AA}$ in all collision systems examined show similar qualitative trends, but have a magnitude which is ordered with the nucleon number A. The $R_\mathrm{AA}$ feature a downward slope at low $p_\mathrm{T}$, a local minimum at around 5$-$7 GeV, and an upward slope with increasing $p_\mathrm{T}$. The $R_\mathrm{AA}$ are also compared in terms of A$^{1/3}$, which is proportional to the nuclear radius. Models including only initial-state nuclear effects fail to reproduce the observed trends, whereas energy loss models reproduce the trends in the region $p_\mathrm{T}$$\gt$ 9.6 GeV.
Charged-particle transverse momentum spectrum in NeNe collisions.
Charged-particle nuclear modification factor in NeNe collisions.
Charged-particle nuclear modification factor in OO collisions.
Energetic quarks and gluons traversing a hot and dense quark-gluon plasma deposit energy and momentum into the medium before hadronizing to collimated sprays of particles, known as jets. This energy-momentum deposition is expected to produce medium responses, collectively known as jet wakes, with ``diffusion wake'' denoting a depletion of particles in the direction opposite to the propagating jet. These phenomena are studied by comparing dijet-hadron correlations measured in lead-lead (PbPb) and proton-proton (pp) collisions to assess jet-induced modifications of bulk particle production. The analysis uses PbPb and pp data recorded at a nucleon-nucleon center-of-mass energy $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV with the CMS detector at the CERN LHC. By exploring how the dijet-hadron correlation distributions differ for various pseudorapidity separations of the two jets in the dijet, the presence of a jet diffusion wake is firmly established. The wake has a significance greater than 5 standard deviations for charged particles in the transverse momentum range 1 $\lt$$p_\mathrm{T}$$\lt$ 2 GeV. The measurements are compared with various model predictions with and without jet wake effects, providing new insights into quark-gluon plasma properties and the formation of jet-induced wakes.
The difference of the near-side charged-particle yields $\mathrm{R^{asym}}-\mathrm{R^{sym}}$ in the charged-particles transverse momentum range $1 < p^{\mathrm{ch}}_{\mathrm{T}} < 2$ GeV as a function of $\Delta\eta^{\mathrm{ch}, \mathrm{jet}_{1}}$ in pp and $0-30\%$, $30-50\%$, and $50-80\%$ PbPb collisions.
The difference of the near-side charged-particle yields $\mathrm{R^{asym}}-\mathrm{R^{sym}}$ in the charged-particles transverse momentum range $2 < p^{\mathrm{ch}}_{\mathrm{T}} < 4$ GeV as a function of $\Delta\eta^{\mathrm{ch}, \mathrm{jet}_{1}}$ in pp and $0-30\%$, $30-50\%$, and $50-80\%$ PbPb collisions.
Particle yield differences $\mathrm{R^{asym}}-\mathrm{R^{sym}}$ as a function of $\Delta\eta^{\mathrm{ch}, \mathrm{jet}_{1}}$ for central $(0-30\%)$ PbPb collisions. The results correspond to the charged-particle transverse momentum range $1 < p^{\mathrm{ch}}_{\mathrm{T}} < 2$ GeV for $\mathrm{R^{asym}}$ with $\Delta\eta^{\mathrm{jet}_{1}, \mathrm{jet}_{2}} \in (0.5, 1.0)$, $\Delta\eta^{\mathrm{jet}_{1}, \mathrm{jet}_{2}} \in (1.0, 1.5)$, and $\Delta\eta^{\mathrm{jet}_{1}, \mathrm{jet}_{2}} \in (1.5, 2.0)$. The result for $2 < p^{\mathrm{ch}}_{\mathrm{T}} < 4$ GeV corresponds to $\mathrm{R^{asym}}$ with $\Delta\eta^{\mathrm{jet}_{1}, \mathrm{jet}_{2}} \in (1.0, 1.5)$.
A search is performed for a new resonance X decaying into either a pair of Higgs bosons (HH) or into a Higgs boson and a new scalar boson Y (HY), using proton-proton collision data collected at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. This study performs a comprehensive exploitation of the bbZZ events, encompassing the following decay topologies. One H candidate is identified through its decay into a bottom quark-antiquark pair, while the other H or the Y candidate is selected through its decay into a pair of Z bosons. One Z boson is required to decay leptonically and the other, to decay into a pair of quarks or neutrinos. Events of interest are categorized based on the Lorentz boosts of the hadronically decaying H and Z bosons. Machine-learning-based discriminants, together with the reconstructed resonance mass, are employed across the different categories to separate signal from backgrounds, and their corresponding distributions are included in a simultaneous fit. No significant deviations from the standard model predictions are observed. Upper limits at the 95% confidence level are set on the HH and HY production cross sections. For resonant HH production, the upper limit on the cross section of pp $\to$ HH production is 1 pb for a high-mass resonance. For HY production, the upper limit on the cross section of the process pp $\to$ X $\to$ bbZZ is approximately 5 fb for a high-mass resonance. This is comparable to the sensitivity achieved in other analyses, which focus on H decays to $γγ$ or $ττ$ and Y decays into a pair of bottom quarks or massive vector bosons.
Pre-fit distributions of $\Delta R(\ell,\ell)$ in the SR qq0M, combining the electron and muon channel and using all three data-taking years. The hatched bands represent the total systematic uncertainties in the backgrounds. The last bin includes overflow.
Pre-fit distributions of HT in the SR qq0M, combining the electron and muon channel and using all three data-taking years. The hatched bands represent the total systematic uncertainties in the backgrounds. The last bin includes overflow.
Pre-fit distributions of $\Delta R(\ell_1,b_1)$ in the SR qq0M, combining the electron and muon channel and using all three data-taking years. The hatched bands represent the total systematic uncertainties in the backgrounds. The last bin includes overflow.
The first measurement of the jet axis decorrelation in events with jets recoiling from an isolated photon is presented for lead-lead (PbPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The jet axis decorrelation is the angular difference ($Δ{j}$) between two definitions of the jet axis. This quantity is expected to be sensitive to the scattering of jet constituents in the quark-gluon plasma (QGP). Events which have a leading isolated photon with transverse momentum 60 $\lt$$p_{\mathrm{T}}^γ$$\lt$ 200 GeV and recoiling jets with 30 $\lt$$p_{\mathrm{T}}^{\text{jet}}$$\lt$ 100 GeV are selected for the analysis. The PbPb result is reported as a function of collision centrality and compared to pp reference data. Jets with $p_{\mathrm{T}}^{\text{jet}}$$\lt$ 60 GeV have consistent $Δ{j}$ shapes for pp and PbPb collisions. However, a narrowing is observed for jets with $p_{\mathrm{T}}^{\text{jet}}$$\gt$ 60 GeV in central PbPb collisions. The results are compared to predictions from the JEWEL, PYQUEN, and HYBRID theoretical models, which include different descriptions of parton energy loss in the QGP.
Photon-tagged jet axis decorrelation in pp and PbPb collisions for jets with $30 < p_T^{jet} < 60$ GeV and $60 < p_T^{jet} < 100$ GeV recoiling from photons with $60 < p_T^{\gamma} < 200$ GeV, normalized per photon. Results are included for PbPb centrality 0-10%, 10-30%, 30-50%, and 50-90%.
Ratios of photon-tagged jet axis decorrelation in pp and PbPb collisions for jets with $30 < p_T^{jet} < 60$ GeV and $60 < p_T^{jet} < 100$ GeV recoiling from photons with $60 < p_T^{\gamma} < 200$ GeV, normalized per photon-jet pair. Results are included for PbPb centrality 0-10%, 10-30%, 30-50%, and 50-90%.
Photon-tagged jet $p_T$ spectrum in pp and PbPb collisions for jets with $30 < p_T^{jet} < 100$ GeV recoiling from photons with $60 < p_T^{\gamma} < 200$ GeV, normalized per photon. Results are included for PbPb centrality 0-10%, 10-30%, 30-50%, and 50-90%.
Event shape variables, constructed from the four-momenta of the final-state objects in an event, are sensitive to the predictions of quantum chromodynamics in multijet production. A measurement of five event shape variables is presented, using proton-proton collision data collected at a centre-of-mass energy of 13 TeV with the CMS detector during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The variables are evaluated using the charged particles inside jets. After correcting for detector effects, their distributions are compared with the results from the predictions from a number of models for multijet production. Overall, there is general agreement between several theoretical predictions and the data.
Normalized unfolded distributions of Complement of transverse thrust($\tau_{\perp}$) for $83<H_{T,2}<109$ GeV
Normalized unfolded distributions of Complement of transverse thrust($\tau_{\perp}$) for $109<H_{T,2}<176$ GeV
Normalized unfolded distributions of Complement of transverse thrust($\tau_{\perp}$) for $176<H_{T,2}<247$ GeV
The azimuthal anisotropy of prompt D$^\pm_\mathrm{s}$ mesons produced in lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV is measured using data obtained with the CMS detector. The dataset corresponds to an integrated luminosity of 0.58 nb$^{-1}$. The azimuthal anisotropy of heavy charmed mesons provides a key constraint on the interactions of charm quarks with the quark-gluon plasma (QGP) medium. These interactions include coalescence mechanisms and parton energy loss in the QGP. The anisotropy is quantified by the second- ($v_2$) and third-order ($v_3$) Fourier coefficients of the azimuthal distribution of the D$^\pm_\mathrm{s}$ mesons. The $v_2$ coefficient is determined in the transverse momentum range 4 $\lt$$p_\mathrm{T}$$\lt$ 40 GeV for three event centrality classes, while the $v_3$ coefficient is measured in the range 4 $\lt$$p_\mathrm{T}$$\lt$ 20 GeV for a single event centrality class. The results for the D$^\pm_\mathrm{s}$ mesons are compared to those previously measured for D$^0$ mesons. The azimuthal anisotropy coefficients for D$^\pm_\mathrm{s}$ and D$^0$ mesons are found to be consistent within the precision of this measurement, suggesting that the strangeness content of the D$^\pm_\mathrm{s}$ meson does not significantly alter its azimuthal distribution within the measured $p_\mathrm{T}$ range.
Ds meson v2 in PbPb collisions at 5.02 TeV as a function of pT in different centralities.
Ds meson v3 in PbPb collisions at 5.02 TeV as a function of pT in the 10-30% centrality interval.
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.
In scattering experiments, high-virtuality partons, i.e., quarks and gluons, initiate a series of additional parton emissions to create collimated sprays of particles known as jets. This paper presents a measurement of the Lund jet plane (LJP) of high-energy jets produced in lead-lead (PbPb) collisions and compares the results to data for proton-proton (pp) collisions. The LJP is formed by iteratively declustering the constituents of a jet into consecutive emissions and recording the relative transverse momentum ($k_\mathrm{T}$) and angle of the resulting emission with respect to its emitter. The angular distributions of two different $k_\mathrm{T}$ slices of the LJP are investigated for jets with radius parameter of 0.4 and transverse momentum in the range 200$-$1000 GeV. The PbPb (pp) data were recorded by the CMS experiment in 2018 (2017) and correspond to an integrated luminosity of 1.7 nb$^{-1}$ (301 pb$^{-1}$) at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measurement was designed to test whether the earliest jet emissions are produced before the formation of the quark-gluon plasma (QGP) in PbPb collisions. Within the experimental uncertainties, no significant difference is observed between the angular distribution of high-$k_\mathrm{T}$ emissions in \pp and PbPb collisions, which is consistent with these emissions occurring early in the jet evolution, before substantial interaction with the QGP.
The unfolded highest kT distribution in pp collisions for kT bin 10-20 GeV. Normalised to number of jets and by bin width.
The unfolded highest kT distribution in pp collisions for kT bin 20-40 GeV. Normalised to number of jets and by bin width.
The unfolded ratio of highest kT distribution in pp and PbPb collisions for kT bin 10-20 GeV. Normalised to number of jets and by bin width.
Three structures, X(6600), X(6900), and X(7100), have emerged from the J$/ψ\,$J$/ψ$ (J$/ψ$\to$μ^+μ^-$) mass spectrum. These are candidates of all-charm tetraquarks, an exotic form of hadronic matter. A clearer picture of these states is obtained using proton-proton collision data collected by the CMS detector that corresponds to 315 fb$^{-1}$, which yields 3.6 times more J$/ψ\,$J$/ψ$ pairs than previous studies by CMS. All three structures, and their mutual interference, have statistical significances above five standard deviations. The presence of interference implies that the structures have common quantum numbers. Their squared masses align linearly with a resonance index and have natural widths that systematically decrease as the index increases. These features are consistent with radial excitations of tetraquarks composed of two aligned spin-1 diquarks without orbital excitation, and disfavor other interpretations. The J$/ψ\,$$ψ$(2S) $\to$$μ^+μ^-μ^+μ^-$ decay mode is also explored and the X(6900) and X(7100) states are found with significances exceeding 8 and 4 standard deviations, respectively.
Measured masses and widths of the three X states from the fits to the $\mathrm{J}/\psi\mathrm{J}/\psi$ mass spectrum from the Run 2+3 data sets. The amplitudes (phases) of the X(6600) and X(7100) relative to the X(6900) state are r1 = 1.790 ± 0.737 (phi1 = 1.693 ± 0.660 rad) and r3 = 0.429 ± 0.267 (phi3 = -0.388 ± 0.410 rad), respectively.
Measured masses and widths of the three X states from the fits to the $\mathrm{J}/\psi \psi(2S)$ mass spectrum from the Run 2+3 data sets.The amplitudes (phases) of the X(7100) relative to the X(6900) state are r = 0.692 ± 0.225 (phi1 = -1.486 ± 0.970 rad).
The $\mathrm{J}/\psi\mathrm{J}/\psi$ invariant-mass spectrum covering the full range of the fit: 6.175 - 15.0 GeV.
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