Event-by-event fluctuations of the average transverse momentum of produced particles near mid-rapidity have been measured by the PHENIX Collaboration in sqrt(s_NN)=200 GeV Au+Au and p+p collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the transverse momentum window over which the average is calculated. Both the centrality and p_T dependence can be well reproduced by a simulation of random particle production with the addition of contributions from hard scattering processes.
Comparisons between the data and mixed event $M_{p_T}$ distributions for the representative 0-5% centrality classes. Also given are the residuals between the data and mixed events in units of standard deviations of the data points form the mixed event points.
Comparisons between the data and mixed event $M_{p_T}$ distributions for the representative 30-35% centrality classes. Also given are the residuals between the data and mixed events in units of standard deviations of the data points form the mixed event points.
$F_{p_T}$ (in percent, 0.2 GeV/$c$ < $p_T$ < 2.0 GeV/$c$) as a function of centrality, which is expressed in terms of the number of participants in the collision, $N_{part}$.
Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.
The measured cross sections for the individual samples divided into years and the overall average value.
Identified mid-rapidity particle spectra of $\pi^{\pm}$, $K^{\pm}$, and $p(\bar{p})$ from 200 GeV p+p and d+Au collisions are reported. A time-of-flight detector based on multi-gap resistive plate chamber technology is used for particle identification. The particle-species dependence of the Cronin effect is observed to be significantly smaller than that at lower energies. The ratio of the nuclear modification factor ($R_{dAu}$) between protons $(p+\bar{p})$ and charged hadrons ($h$) in the transverse momentum range $1.2<{p_{T}}<3.0$ GeV/c is measured to be $1.19\pm0.05$(stat)$\pm0.03$(syst) in minimum-bias collisions and shows little centrality dependence. The yield ratio of $(p+\bar{p})/h$ in minimum-bias d+Au collisions is found to be a factor of 2 lower than that in Au+Au collisions, indicating that the Cronin effect alone is not enough to account for the relative baryon enhancement observed in heavy ion collisions at RHIC.
The invariant yields of $\pi^{\pm}$, $K^{\pm}$, p and their anti-particles as a function of $p_{T}$ from d+Au and NSD p+p events at 200 GeV. The rapidity range was -0.5 $<$ y $<$ 0.0 with the direction of the outgoing Au ions as negative rapidity. Errors are statistical.
The invariant yields of $\pi^{\pm}$, $K^{\pm}$, p and their anti-particles as a function of $p_{T}$ from d+Au and NSD p+p events at 200 GeV. The rapidity range was -0.5 $<$ y $<$ 0.0 with the direction of the outgoing Au ions as negative rapidity. Errors are statistical.
The invariant yields of $\pi^{\pm}$, $K^{\pm}$, p and their anti-particles as a function of $p_{T}$ from d+Au and NSD p+p events at 200 GeV. The rapidity range was -0.5 $<$ y $<$ 0.0 with the direction of the outgoing Au ions as negative rapidity. Errors are statistical.
Cross-section and angular distributions for hadronic and lepton-pair final states in e+e- collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The measurements are used to determine the electromagnetic coupling constant alphaem at LEP2 energies. In addition, the results are used together with OPAL measurements at 91-183 GeV within the S-matrix formalism to determine the gamma-Z interference term and to make an almost model-independent measurement of the Z mass. Limits on extensions to the Standard Model described by effective four-fermion contact interactions or the addition of a heavy Z boson are also presented.
CM energy values.
Measured cross section for QUARK QUARKBAR (HADRON) production. The data are corrected to no interference between initial and final state radiation.
Measured cross section for MU+ MU- production. The data are corrected to no interference between initial and final state radiation.
We present the first large-acceptance measurement of event-wise mean transverse momentum mean p_t fluctuations for Au-Au collisions at nucleon-nucleon center-of-momentum collision energy sqrt{s_{NN}} = 130 GeV. The observed non-statistical mean p_t fluctuations substantially exceed in magnitude fluctuations expected from the finite number of particles produced in a typical collision. The r.m.s. fractional width excess of the event-wise mean p_t distribution is 13.7 +/- 0.1(stat) +/- 1.3(syst)% relative to a statistical reference, for the 15% most-central collisions and for charged hadrons within pseudorapidity range |eta|<1, 2pi azimuth and 0.15 < p_t < 2 GeV/c. The width excess varies smoothly but non-monotonically with collision centrality, and does not display rapid changes with centrality which might indicate the presence of critical fluctuations. The reported mean p_t fluctuation excess is qualitatively larger than those observed at lower energies and differs markedly from theoretical expectations. Contributions to mean p_t mean fluctuations from semi-hard parton scattering in the initial state and dissipation in the bulk colored medium are discussed.
Event frequency distribution on $\sqrt{n}(\langle p_t\rangle - \hat{p}_t)/\sigma\hat{p}_t$ for 80% of primary charged hadrons in $|\eta|$ < 1 for 183k central events
Difference in upper panel between data and gamma reference
Centrality dependences of the measured charge independent (CI) and charge dependent (CD) difference factors $\Delta\sigma_{p_t:n}$ plus the corresponding values extrapolated to 100% tracking efficiency. Statistical errors $\pm$ 0.5 MeV/c; systematic errors are $\pm$ 9%. Difference factors extrapolated to 100% tracking efficiency and no secondary particle contamination. Uncertainties are $\pm$ 12%.
The PHENIX experiment at RHIC has measured charged hadron yields at mid-rapidity over a wide range of transverse momentum (0.5 < p_T < 10 GeV/c) in Au+Au collisions at sqrt(s_NN)=200 GeV. The data are compared to pi^zero measurements from the same experiment. For both charged hadrons and neutral pions, the yields per nucleon-nucleon collision are significantly suppressed in central compared to peripheral and nucleon-nucleon collisions. The suppression sets in gradually and increases with increasing centrality of the collisions. Above 4-5 GeV/c in p_T, a constant and almost identical suppression of charged hadrons and pi^zeroes is observed. The p_T spectra are compared to published spectra from Au+Au at sqrt(s_NN)=130 in terms of x_t scaling. Central and peripheral pi^zero as well as peripheral charged spectra exhibit the same x_t scaling as observed in p+p data.
$p_T$ spectra of charged hadrons for minimum bias collisions along with spectra for 9 centrality classes derived from the pseudo-rapidity region $|\eta|$ < 0.18. Stat. stands for statistical error, syst. stands for the systematic errors and occ. stands for occupancy error.
$p_T$ spectra of charged hadrons for minimum bias collisions along with spectra for 9 centrality classes derived from the pseudo-rapidity region $|\eta|$ < 0.18. Stat. stands for statistical error, syst. stands for the systematic errors and occ. stands for occupancy error.
$p_T$ spectra of charged hadrons for minimum bias collisions along with spectra for 9 centrality classes derived from the pseudo-rapidity region $|\eta|$ < 0.18. Stat. stands for statistical error, syst. stands for the systematic errors and occ. stands for occupancy error.
We report on measurements of differential cross sections d sigma/d p_t for prompt charm meson production in p anti-p collisions at s**(1/2) = 1.96 TeV using 5.8 +/- 0.3 pb-1 of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y| \leq 1 in four fully reconstructed decay modes: D0 --> K- pi+, D*+ -> D0 pi+, D+ --> K- pi+ pi+, D+_s--> phi pi+, and their charge conjugates. The measured cross sections are compared to theoretical calculations.
Measured prompt charm production cross sections for ABS(YRAP) < 1. The branching ratios used are (D0:3.81 +- 0.09 PCT), (D+:2.57 +- 0.06 PCT),(D+:9.1 +- 0.6 PCT) and (D/S+:1.8 +- 0.5 PCT).
A study of Z-boson pair production in e+e- annihilation at center-of-mass energies between 190 GeV and 209 GeV is reported. Final states containing only leptons, (l+l-l+l- and l+l-nn), quark and lepton pairs, (qql+l-, qqnn) and only hadrons (qqqq) are considered. In all states with at least one Z boson decaying hadronically, lifetime, lepton and event-shape tags are used to separate bb pairs from qq final state. Limits on anomalous ZZgamma and ZZZ couplings are derived from the measured cross sections and from event kinematics using an optimal observable method. Limits on low scale gravity with large dimensions are derived from the cross sections and their dependence on polar angle.
The NC2 Z0-pair cross sections obtained from fits to the data.
J/psi production has been measured in proton-proton collisions at sqrt(s)= 200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at RHIC. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) micro barns. The mean transverse momentum is 1.80 +/- 0.23(stat) +/- 0.16(sys) GeV/c.
Measured J/PSI distribution in PT for the e+e- channel. The value of B, the branching fraction to either electrons or muons is the average value from PDG : 5.9%.The rapidity range is -0.35<y<0.35. Incertainties are 1-sigma statistical errors on the (signal - background) net yield. There is a 10% overall absolute cross section normalization error in addition to the error given.
Measured J/PSI distribution in PT for the mu+mu- channel. The value of B, the branching fraction to either electrons or muons, is the average value from PDG: 5.9%.The rapidity range is -2.2<y<-1.2. Incertainties are 1-sigma statistical errors on the (signal - background) net yield.There is a 10% overall absolute cross section normalization error in addition to the error given.
J/PSI distribution in rapidity. The data at rapidity = 0 is from the electron arm, the data from the muon arm, corresponding to forward rapidity is divided in two bins.The value of B,the branching fraction to either electrons or muons, is 5.9%, the average value from PDG.Incertainties are 1-sigma statistical errors on the (signal - background) net yield.There is a 10% overall absolute cross section normalization error in addition to the error given.
We present the results of charged particle fluctuations measurements in Au + Au collisions at $\sqrt{s_{NN}}=130$ GeV using the STAR detector. Dynamical fluctuations measurements are presented for inclusive charged particle multiplicities as well as for identified charged pions, kaons, and protons. The net charge dynamical fluctuations are found to be large and negative providing clear evidence that positive and negative charged particle production is correlated within the pseudorapidity range investigated. Correlations are smaller than expected based on model-dependent predictions for a resonance gas or a quark gluon gas which undergoes fast hadronization and freeze-out. Qualitative agreement is found with comparable scaled p+p measurements and a HIJING model calculation based on independent particle collisions, although a small deviation from the 1/N scaling dependence expected from this model is observed.
Dynamical fluctuations, $ν_{+−,dyn}$, measured in $|\eta| ≤ 0.5$ as a function of the collision centrality estimated with the total (uncorrected) multiplicity, M, in $|\eta| < 0.75$. Only statistical errors are listed. Systematic errors estimated at $5\%$.
$\langle N\rangle ν_{+−,dyn}$ measured in $|\eta| ≤ 0.5$ vs M (opened circles) compared to the charge conservation limit (dotted line), resonance gas expectation based on ref.[5](solid line); and HIJING calculation (solid squares). Only statistical errors are listed. Systematic errors estimated at $10\%$.
Fluctuations $ν_{+−,dyn}$ for the $6\%$ most central collisions as a function of the range of integrated pseudorapidities. The expected limit due to charge conservation is shown as a dotted line.
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