The PHENIX experiment at the Relativistic Heavy Ion Collider has measured 2nd and 3rd order Fourier coefficients of the azimuthal distributions of direct photons emitted at midrapidity in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV for various collision centralities. Combining two different analysis techniques, results were obtained in the transverse momentum range of $0.4
Direct photon $v_2$ and $v_3$ at midrapidity ($|\eta|$ < 0.35), for different centralities, measured with the conversion method. The event plane was determined with the reaction plane detector (1 < $|\eta|$ < 2.8).
Direct photon $v_2$ and $v_3$ at midrapidity ($|\eta|$ < 0.35), for different centralities, measured with the calorimeter method. The event plane was determined with the reaction plane detector (1 < $|\eta|$ < 2.8).
We report on the inclusive production cross sections of J/$\psi$, $\psi$(2S), $\Upsilon$(1S), $\Upsilon$(2S) and $\Upsilon$(3S), measured at forward rapidity with the ALICE detector in pp collisions at a center-of-mass energy $\sqrt{s}=8$ TeV. The analysis is based on data collected at the LHC and corresponds to an integrated luminosity of 1.28 pb$^{-1}$. Quarkonia are reconstructed in the dimuon-decay channel. The differential production cross sections are measured as a function of the transverse momentum $p_{\rm T}$ and rapidity $y$, over the $p_{\rm T}$ ranges $0
Differential production cross sections of J/$\psi$ as a function of $p_{\rm T}$.
Differential production cross sections of J/$\psi$ as a function of rapidity.
integrated production cross section of J/$\psi$.
We report on the first measurement of an excess in the yield of J/$\psi$ at very low transverse momentum ($p_{\rm T}< 0.3$ GeV/$c$) in peripheral hadronic Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/$\psi$ in the rapidity range $2.5
J/$\psi$ nuclear modification factor $R_{\rm AA}$ as a function of the mean number of participant nucleons $\langle N_{\rm{part}}\rangle$, the first error is statistical, the second error is systematic uncorrelated in $p_{\rm T}$ and centrality, the third error is systematic correlated in $p_{\rm T}$ but not in centrality, the fourth error is systematic correlated in centrality but not in $p_{\rm T}$ and the fifth error is systematic correlated in $p_{\rm T}$ and centrality.
J/$\psi$ nuclear modification factor $R_{\rm AA}$ as a function of the mean number of participant nucleons $\langle N_{\rm{part}}\rangle$, the first error is statistical, the second error is systematic uncorrelated in $p_{\rm T}$ and centrality, the third error is systematic correlated in $p_{\rm T}$ but not in centrality, the fourth error is systematic correlated in centrality but not in $p_{\rm T}$ and the fifth error is systematic correlated in $p_{\rm T}$ and centrality.
J/$\psi$ nuclear modification factor $R_{\rm AA}$ as a function of the mean number of participant nucleons $\langle N_{\rm{part}}\rangle$, the first error is statistical, the second error is systematic uncorrelated in $p_{\rm T}$ and centrality, the third error is systematic correlated in $p_{\rm T}$ but not in centrality, the fourth error is systematic correlated in centrality but not in $p_{\rm T}$ and the fifth error is systematic correlated in $p_{\rm T}$ and centrality.
The pseudorapidity ($\eta$) and transverse-momentum ($p_{\rm T}$) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy $\sqrt{s}$ = 13 TeV. The pseudorapidity distribution in $|\eta|<$ 1.8 is reported for inelastic events and for events with at least one charged particle in $|\eta|<$ 1. The pseudorapidity density of charged particles produced in the pseudorapidity region $|\eta|<$ 0.5 is 5.31 $\pm$ 0.18 and 6.46 $\pm$ 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 $<$ $p_{\rm T}$ $<$ 20 GeV/c and $|\eta|<$ 0.8 for events with at least one charged particle in $|\eta|<$ 1. The correlation between transverse momentum and particle multiplicity is also investigated by studying the evolution of the spectra with event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators.
Average pseudorapidity density of charged particles as a function of eta produced in pp collisions at sqrt(s) = 13 TeV. The results are shown in the normalisation classes INEL and INEL>0. The uncertainties are the quadratic sum of statistical and systematic contributions.
Invariant charged-particle yield as a function of pT normalised to INEL>0 events.
Ratio of transverse-momentum spectra in INEL>0 events at $\sqrt{s}$ = 13 and 7 TeV.
Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of 19.5 inverse femtobarns, collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from ttW or ttZ decays. The ttW cross section is measured to be 382 +117 -102 fb with a significance of 4.8 standard deviations from the background-only hypothesis. The ttZ cross section is measured to be 242 +65 -55 fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the ttW and ttZ cross sections.
Expected yields after the final fit, compared to the observed data for OS t$\bar{\mathrm{t}}$Z final states. Here ``hf'' and ``lf'' stand for heavy and light flavors, respectively.
Expected yields after the final fit, compared to the observed data for SS t$\bar{\mathrm{t}}$W final states. The multiboson process includes WWW, WWZ, and W$^{\pm}$W$^{\pm}$; t$\mathrm{\bar{t}}$+X includes t$\mathrm{\bar{t}}\gamma$, t$\mathrm{\bar{t}}\gamma^{*}$, and t$\bar{\mathrm{t}}$WW.
Expected yields after the final fit, compared to the observed data for 3$\ell$ t$\bar{\mathrm{t}}$W and three and 4$\ell$ t$\bar{\mathrm{t}}$Z final states. The 4$\ell$ ``Z-veto'' channel has exactly one lepton pair consistent with a Z boson decay; the ``Z'' channel has two. The multiboson process includes WWW and WWZ; t$\mathrm{\bar{t}}$+X includes t$\mathrm{\bar{t}}\gamma$, t$\mathrm{\bar{t}}\gamma^{*}$, and t$\bar{\mathrm{t}}$WW.
Production cross-sections of prompt charm mesons are measured with the first data from $pp$ collisions at the LHC at a centre-of-mass energy of $13\,\mathrm{TeV}$. The data sample corresponds to an integrated luminosity of $4.98 \pm 0.19\,\mathrm{pb}^{-1}$ collected by the LHCb experiment. The production cross-sections of $D^{0}$, $D^{+}$, $D_{s}^{+}$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{\mathrm{T}}$, and rapidity, $y$, and cover the range $0 < p_{\mathrm{T}} < 15\,\mathrm{GeV}/c$ and $2.0 < y < 4.5$. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of $1 < p_{\mathrm{T}} < 8\,\mathrm{GeV}/c$ are found to be \begin{equation} \sigma(pp \to D^{0} X) = 2072 \pm 2 \pm 124\,\mu\mathrm{b}\\ \sigma(pp \to D^{+} X) = 834 \pm 2 \pm \phantom{1}78\,\mu\mathrm{b}\\ \sigma(pp \to D_{s}^{+} X) = 353 \pm 9 \pm \phantom{1}76\,\mu\mathrm{b}\\ \sigma(pp \to D^{*+} X) = 784 \pm 4 \pm \phantom{1}87\,\mu\mathrm{b} \end{equation} where the uncertainties are due to statistical and systematic uncertainties, respectively.
Differential production cross-sections for prompt $D^{0} + \bar{D}^{0}$ mesons in bins of $(p_{\mathrm{T}}, y)$. The first uncertainty is statistical, and the second is the total systematic.
Differential production cross-sections for prompt $D^{+} + D^{-}$ mesons in bins of $(p_{\mathrm{T}}, y)$. The first uncertainty is statistical, and the second is the total systematic.
Differential production cross-sections for prompt $D_{s}^{+} + D_{s}^{-}$ mesons in bins of $(p_{\mathrm{T}}, y)$. The first uncertainty is statistical, and the second is the total systematic.
PHENIX measurements are presented for the cross section and double-helicity asymmetry ($A_{LL}$) in inclusive $\pi^0$ production at midrapidity from $p$$+$$p$ collisions at $\sqrt{s}=510$~GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum-chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The $\pi^{0}A_{LL}$ results follow an increasingly positive asymmetry trend with $p_T$ and $\sqrt{s}$ with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on $\pi^0$ and jet $A_{LL}$, and suggested a positive contribution of gluon polarization to the spin of the proton $\Delta G$ for the gluon momentum fraction range $x>0.05$. The data presented here extend to a currently unexplored region, down to $x\sim0.01$, and thus provide additional constraints on the value of $\Delta G$. The results confirm the evidence for nonzero $\Delta G$ using a different production channel in a complementary kinematic region.
The neutral pion production cross section at midrapidity in $p$ + $p$ collisions at $\sqrt{s}$ = 510 GeV as a function of $p_T$ and NLO pQCD calculations for theory scales $\mu = p_T/2$ (dotted line), $p_T$ (solid line) and 2$p_T$ (dashed line), with $\mu$ representing equal factorization, renormalization, and fragmentation scales.
$A_{LL}$ with point-to-point uncertainty $\delta A_{LL}$ vs $p_T$ for $\pi^0$ production at midrapidity in $p$ + $p$ collisions at $\sqrt{s}$ = 510 GeV. Not included in the figure/table are the correlated for all points scale systematic uncertainty of 6.5% (scales both the values and point-to-point uncertainties by the same factor). Correlated relative luminosity (shift) uncertainity of 3.6e-4 (shifts all points by the same value).
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 0.1 $<p_{T}<$ 1.0 $GeV/c$ and $N_{offline}^{trk}<$ 35 bins for pp data at $\sqrt =$ 13 $TeV$. The $p_{T}$ selection applies to both particles in the pair. Only statistical uncertainties are given. The subtracted ZYAM constant is given ($C_{ZYAM}$).
Correlated yield obtained with the ZYAM procedure as a function of $|\Delta\Phi|$, averaged over 2 $<|\Delta\eta|<$ 4 in for 0.1 $<p_{T}<$ 1.0 $GeV/c$ and $N_{offline}^{trk}<$ 35 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 ($C_{ZYAM}$).
Correlated yield obtained with the ZYAM procedure as a function of $|\Delta\Phi|$, averaged over 2 $<|\Delta\eta|<$ 4 in for 1.0 $<p_{T}<$ 2.0 $GeV/c$ and $N_{offline}^{trk}<$ 35 bins for pp data at $\sqrt =$ 13 $TeV$. The $p_{T}$ selection applies to both particles in the pair. Only statistical uncertainties are given. The subtracted ZYAM constant is given ($C_{ZYAM}$).
Jet multiplicity distributions in top quark pair (t t-bar) events are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC using a data set corresponding to an integrated luminosity of 19.7 inverse femtobarns. The measurement is performed in the dilepton decay channels (e+ e-, mu+ mu-, and e+/- mu-/+). The absolute and normalized differential cross sections for t t-bar production are measured as a function of the jet multiplicity in the event for different jet transverse momentum thresholds and the kinematic properties of the leading additional jets. The differential t t-bar b and t t-bar b b-bar cross sections are presented for the first time as a function of the kinematic properties of the leading additional b jets. Furthermore, the fraction of events without additional jets above a threshold is measured as a function of the transverse momenta of the leading additional jets and the scalar sum of the transverse momenta of all additional jets. The data are compared and found to be consistent with predictions from several perturbative quantum chromodynamics event generators and a next-to-leading order calculation.
Absolute differential ttbar cross sections as a function of the jet multiplicity for jets with pt > 30GeV, along with their statistical and systematic uncertainties. The results are presented at the particle level in the visible phase space of the ttbar decay products and the additional jets.
Normalized differential ttbar cross sections as a function of the jet multiplicity for jets with pt > 30GeV, along with their statistical and systematic uncertainties. The results are presented at the particle level in the visible phase space of the ttbar decay products and the additional jets.
Absolute differential ttbar cross sections as a function of the jet multiplicity for jets with pt > 60GeV, along with their statistical and systematic uncertainties. The results are presented at the particle level in the visible phase space of the ttbar decay products and the additional jets.
We present a measurement of b jet transverse momentum (pt) spectra in proton-lead (pPb) collisions using a dataset corresponding to about 35 inverse nanobarns collected with the CMS detector at the LHC. Jets from b quark fragmentation are found by exploiting the long lifetime of hadrons containing a b quark through tagging methods using distributions of the secondary vertex mass and displacement. Extracted cross sections for b jets are scaled by the effective number of nucleon-nucleon collisions and are compared to a reference obtained from PYTHIA simulations of pp collisions. The PYTHIA-based estimate of the nuclear modification factor is found to be 1.22 +/- 0.15 (stat + syst pPb) +/- 0.27 (syst PYTHIA) averaged over all jets with pt between 55 and 400 GeV/c and with abs(eta[lab]) < 2. We also compare this result to predictions from models using perturbative calculations in quantum chromodynamics.
Distributions of the JP tagger discriminator before applying the SSV tagger selection.
Distributions of the JP tagger discriminator after applying the SSV tagger selection.
Distributions of the b-tagging efficiency as a function of the mistag rate of light jets for pp collisions in a PYTHIA simulation.