In this letter, measurements of the shared momentum fraction ($z_{\rm{g}}$) and the groomed jet radius ($R_{\rm{g}}$), as defined in the SoftDrop algorihm, are reported in \pp collisions at $\sqrt{s} = 200$ GeV collected by the STAR experiment. These substructure observables are differentially measured for jets of varying resolution parameters from $R = 0.2 - 0.6$ in the transverse momentum range $15 < p_{\rm{T, jet}} < 60$ GeV$/c$. These studies show that, in the $p_{\rm{T, jet}}$ range accessible at $\sqrt{s} = 200$ GeV and with increasing jet resolution parameter and jet transverse momentum, the $z_{\rm{g}}$ distribution asymptotically converges to the DGLAP splitting kernel for a quark radiating a gluon. The groomed jet radius measurements reflect a momentum-dependent narrowing of the jet structure for jets of a given resolution parameter, i.e., the larger the $p_{\rm{T, jet}}$, the narrower the first splitting. For the first time, these fully corrected measurements are compared to Monte Carlo generators with leading order QCD matrix elements and leading log in the parton shower, and to state-of-the-art theoretical calculations at next-to-leading-log accuracy. We observe that PYTHIA 6 with parameters tuned to reproduce RHIC measurements is able to quantitatively describe data, whereas PYTHIA 8 and HERWIG 7, tuned to reproduce LHC data, are unable to provide a simultaneous description of both $z_{\rm{g}}$ and $R_{\rm{g}}$, resulting in opportunities for fine parameter tuning of these models for \pp collisions at RHIC energies. We also find that the theoretical calculations without non-perturbative corrections are able to qualitatively describe the trend in data for jets of large resolution parameters at high $p_{\rm{T, jet}}$, but fail at small jet resolution parameters and low jet transverse momenta.
The data points and the error bars represent the mean $p_{\rm{T, jet}}^{\rm{det}}$ and the width (RMS) for a given $p_{\rm{T, jet}}^{\rm{part}}$ selection $R = 0.4$.
The data points and the error bars represent the mean $p_{\rm{T, jet}}^{\rm{det}}$ and the width (RMS) for a given $p_{\rm{T, jet}}^{\rm{part}}$ selection $R = 0.2$.
The data points and the error bars represent the mean $p_{\rm{T, jet}}^{\rm{det}}$ and the width (RMS) for a given $p_{\rm{T, jet}}^{\rm{part}}$ selection $R = 0.6$.
Measurements of the cross section for production of massive dihadrons by 800-GeV protons incident on a tungsten target are presented. These are compared with measurements taken at lower and higher s and with perturbative-QCD predictions. Scaling and A-dependence behaviors observed at lower energies are confirmed, and good agreement with QCD is obtained. Model dependences of earlier measurements are discussed.
No description provided.
Triple differential cross section. Note that the errors plotted in the original figure are 2 time too large. The numbers given here are correct.
The yields of the 1S and the sum of the 2S and 3S Υ resonances have been measured for 800-GeV protons incident on targets of H2, C, Ca, Fe, and W. A significant nuclear dependence is seen in the yield per nucleon which, within errors, is the same for the Υ(1S) and Υ(2S+3D) states. A large decrease in the relative yield from heavy nuclei is found for the range xF<0. Significant nuclear dependence is also observed in the pt distribution. Differential cross sections for the Υ(1S) for H2 are presented over the ranges 0.24≤pt≤3.4 GeV/c and -0.15≤xF≤0.5.
Mass dependence as a function of feynman X for UPSI(1S) production.
Mass dependence as a function of feynman X for UPSI(2S/3S) production.
Mass dependence as a function of transverse momentum for UPSI(1S) production.
The yield of J/ψ and ψ’ vector-meson states has been measured for 800-GeV protons incident on deuterium, carbon, calcium, iron, and tungsten targets. A depletion of the yield per nucleon from heavy nuclei is observed for both J/ψ and ψ’ production. This depletion exhibits a strong dependence on xF and pt. Within experimental errors the depletion is the same for the J/ψ and the ψ’.
Ratio of heavy nucleus to deuterium yields. A is the mass number of the target nucleus.
Ratio of heavy nucleus to deuterium yeilds. A is the mass number of the target nucleus.
Ratio of heavy nucleus to deuterium yeilds. A is the mass number of the target nucleus.
A precise measurement of the atomic-mass dependence of dimuon production induced by 800-GeV protons is reported. Over 450 000 muon pairs with dimuon mass M≥4 GeV were recorded from targets of H2, C, Ca, Fe, and W. The ratio of dimuon yield per nucleon for nuclei versus H2, R=YA/Y2H, is sensitive to modifications of the antiquark sea in nuclei. No nuclear dependence of this ratio is observed over the range of target-quark momentum fraction 0.1
High Mass trigger data.
Intermediate Mass trigger data.
Low Mass trigger data.
Absolute cross sections as functions of kinematic variables are presented for the production of muon pairs from 800 GeV proton bombardment of H2. Drell-Yan (continuum) dimuons were recorded in the mass regions 4.5≤Mμ+μ−≤9 GeV and Mμ+μ−≥11 GeV, with an x-Feynman range -0.1≤xF≤0.75. This range corresponds to smaller masses and larger values of xF than previous 800 GeV Drell-Yan data. Cross sections for the Υ(1S) resonance are also given versus the transverse momentum and xF.
No description provided.
No description provided.
No description provided.
We present an analysis of 800-GeV proton-induced Drell-Yan production data from isoscalar targets 2H and C, and from W, which has a large neutron excess. The ratio of cross sections per nucleon, R-σW/σIS, is sensitive to the difference between the d¯(x) and u¯(x) structure functions of the proton. We find that R is close to unity in the range 0.04≤x≤0.27, allowing upper limits to be set on the d¯-u¯ asymmetry. Additionally, the shape of the differential cross section m3 d2σ/dxF dm for 2H at xF≊0 shows no evidence of an asymmetric sea in the proton. We examine the implications of these data for various models of the violation of the Gottfried sum rule in deep-inelastic lepton scattering.
Upper limit at the 2sigma statistical error level. Mass of MU+ MU- in GeV.
Jet substructure quantities are measured using jets groomed with the soft-drop grooming procedure in dijet events from 32.9 fb$^{-1}$ of $pp$ collisions collected with the ATLAS detector at $\sqrt{s} = 13$ TeV. These observables are sensitive to a wide range of QCD phenomena. Some observables, such as the jet mass and opening angle between the two subjets which pass the soft-drop condition, can be described by a high-order (resummed) series in the strong coupling constant $\alpha_S$. Other observables, such as the momentum sharing between the two subjets, are nearly independent of $\alpha_S$. These observables can be constructed using all interacting particles or using only charged particles reconstructed in the inner tracking detectors. Track-based versions of these observables are not collinear safe, but are measured more precisely, and universal non-perturbative functions can absorb the collinear singularities. The unfolded data are directly compared with QCD calculations and hadron-level Monte Carlo simulations. The measurements are performed in different pseudorapidity regions, which are then used to extract quark and gluon jet shapes using the predicted quark and gluon fractions in each region. All of the parton shower and analytical calculations provide an excellent description of the data in most regions of phase space.
Data from Fig 6a. The unfolded all-particle $log_{10}(\rho^2)$ distribution for anti-kt R=0.8 jets with $p_T$ > 300 GeV, after the soft drop algorithm is applied for $\beta$ = 0, in data. All uncertainties described in the text are shown on the data. The distributions are normalized to the integrated cross section, $\sigma$(resum), measured in the resummation region, $-3.7 < log_{10}(\rho^2) < -1.7$.
Data from Fig 6b. The unfolded charged-particle $log_{10}(\rho^2)$ distribution for anti-kt R=0.8 jets with $p_T$ > 300 GeV, after the soft drop algorithm is applied for $\beta$ = 0, in data. All uncertainties described in the text are shown on the data. The distributions are normalized to the integrated cross section, $\sigma$(resum), measured in the resummation region, $-3.7 < log_{10}(\rho^2) < -1.7$.
Data from Fig 6c. The unfolded all-particle $log_{10}(\rho^2)$ distribution for anti-kt R=0.8 jets with $p_T$ > 300 GeV, after the soft drop algorithm is applied for $\beta$ = 1, in data. All uncertainties described in the text are shown on the data. The distributions are normalized to the integrated cross section, $\sigma$(resum), measured in the resummation region, $-3.7 < log_{10}(\rho^2) < -1.7$.
A measurement of novel event shapes quantifying the isotropy of collider events is performed in 140 fb$^{-1}$ of proton-proton collisions with $\sqrt s=13$ TeV centre-of-mass energy recorded with the ATLAS detector at CERN's Large Hadron Collider. These event shapes are defined as the Wasserstein distance between collider events and isotropic reference geometries. This distance is evaluated by solving optimal transport problems, using the 'Energy-Mover's Distance'. Isotropic references with cylindrical and circular symmetries are studied, to probe the symmetries of interest at hadron colliders. The novel event-shape observables defined in this way are infrared- and collinear-safe, have improved dynamic range and have greater sensitivity to isotropic radiation patterns than other event shapes. The measured event-shape variables are corrected for detector effects, and presented in inclusive bins of jet multiplicity and the scalar sum of the two leading jets' transverse momenta. The measured distributions are provided as inputs to future Monte Carlo tuning campaigns and other studies probing fundamental properties of QCD and the production of hadronic final states up to the TeV-scale.
IRing2 for HT2>=500 GeV, NJets>=2
IRing2 for HT2>=500 GeV, NJets>=3
IRing2 for HT2>=500 GeV, NJets>=4
$Z$ boson events at the Large Hadron Collider can be selected with high purity and are sensitive to a diverse range of QCD phenomena. As a result, these events are often used to probe the nature of the strong force, improve Monte Carlo event generators, and search for deviations from Standard Model predictions. All previous measurements of $Z$ boson production characterize the event properties using a small number of observables and present the results as differential cross sections in predetermined bins. In this analysis, a machine learning method called OmniFold is used to produce a simultaneous measurement of twenty-four $Z$+jets observables using $139$ fb$^{-1}$ of proton-proton collisions at $\sqrt{s}=13$ TeV collected with the ATLAS detector. Unlike any previous fiducial differential cross-section measurement, this result is presented unbinned as a dataset of particle-level events, allowing for flexible re-use in a variety of contexts and for new observables to be constructed from the twenty-four measured observables.
Differential cross-section in bins of dimuon $p_\text{T}$. The actual measurement is unbinned and available with examples at <a href="https://gitlab.cern.ch/atlas-physics/public/sm-z-jets-omnifold-2024">gitlab.cern.ch/atlas-physics/public/sm-z-jets-omnifold-2024</a>
Differential cross-section in bins of dimuon rapidity. The actual measurement is unbinned and available with examples at <a href="https://gitlab.cern.ch/atlas-physics/public/sm-z-jets-omnifold-2024">gitlab.cern.ch/atlas-physics/public/sm-z-jets-omnifold-2024</a>
Differential cross-section in bins of leading muon $p_\mathrm{T]$. The actual measurement is unbinned and available with examples at <a href="https://gitlab.cern.ch/atlas-physics/public/sm-z-jets-omnifold-2024">gitlab.cern.ch/atlas-physics/public/sm-z-jets-omnifold-2024</a>