Measurements of the midrapidity transverse energy distribution, $d\Et/d\eta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV and additionally for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=62.4$ and 130 GeV. The $d\Et/d\eta$ distributions are first compared with the number of nucleon participants $N_{\rm part}$, number of binary collisions $N_{\rm coll}$, and number of constituent-quark participants $N_{qp}$ calculated from a Glauber model based on the nuclear geometry. For Au$+$Au, $\mean{d\Et/d\eta}/N_{\rm part}$ increases with $N_{\rm part}$, while $\mean{d\Et/d\eta}/N_{qp}$ is approximately constant for all three energies. This indicates that the two component ansatz, $dE_{T}/d\eta \propto (1-x) N_{\rm part}/2 + x N_{\rm coll}$, which has been used to represent $E_T$ distributions, is simply a proxy for $N_{qp}$, and that the $N_{\rm coll}$ term does not represent a hard-scattering component in $E_T$ distributions. The $dE_{T}/d\eta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distribution using two models that both reproduce the Au$+$Au data. However, while the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, the additive-quark model does not.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Direct photons have been measured in sqrt(s_NN)=200 GeV d+Au collisions at midrapidity. A wide p_T range is covered by measurements of nearly-real virtual photons (1<p_T<6 GeV/c) and real photons (5<p_T<16 GeV/c). The invariant yield of the direct photons in d+Au collisions over the scaled p+p cross section is consistent with unity. Theoretical calculations assuming standard cold nuclear matter effects describe the data well for the entire p_T range. This indicates that the large enhancement of direct photons observed in Au+Au collisions for 1.0<p_T<2.5 GeV/c is due to a source other than the initial-state nuclear effects.
Direct photon fraction. The direct-photon fractions from the virtual-photon analysis as a function of $p_{T}$ in $p+p$ (MB) [1] collisions. The values in the table are equal to this mean value. The statistical and systematic uncertainties are shown by the bars and bands, respectively. The curves show expectations from a NLO pQCD calculation [17, 18] with different cutoff mass scales: (solid) $\mu$ = 0.5 $p_{T}$ , (dash) $\mu$ = 1.0 $p_{T}$ , and (dash-dot) $\mu$ = 2.0 $p_{T}$.
Direct photon fraction. The direct-photon fractions from the virtual-photon analysis as a function of $p_{T}$ in $d$+Au (MB) [1] collisions. The values in the table are equal to this mean value. The statistical and systematic uncertainties are shown by the bars and bands, respectively. The curves show expectations from a NLO pQCD calculation [17, 18] with different cutoff mass scales: (solid) $\mu$ = 0.5 $p_{T}$ , (dash) $\mu$ = 1.0 $p_{T}$ , and (dash-dot) $\mu$ = 2.0 $p_{T}$.
Direct photon cross section. (a) The invariant cross sections of the direct photon in $p+p$ [3, 4] and $d$+Au collisions. The $p+p$ fit result with the empirical parameterization described in the text is shown as well as NLO pQCD calculations, and the scaled $p+p$ fit is compared with the $d$+Au data. The closed and open symbols show the results from the virtual photon and $\pi_{0}$-tagging methods, respectively. The asterisk symbols show the result from the statistical subtraction method for $d$+Au data, overlapping with the virtual photon result in 3 < $p_{T}$ < 5 GeV/c. The values in the table are equal to this mean value. The bars and bands represent the point-to-point (ptp.) and $p_{T}$-correlated (cor.) uncertainties, respectively. (b) The $p+p$ data over the fit. The uncertainties of the fit due to both point-to-point (ptp.) and pT -correlated uncertainties of the data are summed quadratically, and the sum is shown as dotted lines. The NLO pQCD calculations divided by the fit are also shown.
A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV, and Cu+Cu collisions sqrt(s_NN) = 22.5, 62.4, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for non-dynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon p+p data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. An analysis of Negative Binomial Distribution fits to the multiplicity distributions demonstrates that the heavy ion data exhibit weak clustering properties.
Additional information containing number of events which were used to reconstruct the numvers matching to Figure 1 and 2.
Additional information containing number of events which were used to reconstruct the numvers matching to Figure 1 and 2.
Additional information containing number of events which were used to reconstruct the numvers matching to Figure 1 and 2.
All of the experimental data points presented in the original paper are correct and unchanged (including statistical and systematic uncertainties). However, herein we correct a comparison between the experimental data and a theoretical picture, because we discovered a mistake in the code used. All of the most probable sigma_breakup values differ by less than 0.4 mb from those originally presented. However, the one standard deviation uncertainties (that include contributions from both the statistical and systematic uncertainties on the experimental data points) are approximately 30-60% larger than originally reported. We give a table of the new comparison results and corrected versions of Figs. 8-11 of the original paper and we note that no correction is needed for results from the data-driven method in Fig. 13.
J/PSI invariant (1/(2PI*PT))*D2(N)/DPT/DYRAP versus rapidity in D+AU collisions, over 3 bins of rapidity.
J/PSI invariant (1/(2PI*PT))*D2(N)/DPT/DYRAP versus rapidity in D+AU collisions, over 5 bins of rapidity.
J/PSI invariant (1/(2PI*PT))*D2(N)/DPT/DYRAP versus PT at backward rapidity (-2.2<y<-1.2) in D+AU collisions.
We present transverse momentum (p_T) spectra of charged hadrons measured in deuteron-gold and nucleon-gold collisions at \sqrts = 200 GeV for four centrality classes. Nucleon-gold collisions were selected by tagging events in which a spectator nucleon was observed in one of two forward rapidity detectors. The spectra and yields were investigated as a function of the number of binary nucleon-nucleon collisions, \nu, suffered by deuteron nucleons. A comparison of charged particle yields to those in p+p collisions show that the yield per nucleon-nucleon collision saturates with \nu for high momentum particles. We also present the charged hadron to neutral pion ratios as a function of p_T.
<p>Charged hadron spectra for centrality selected d+Au collisions.</p>
<p>Charged hadron spectra for centrality selected d+Au collisions.</p>
<p>Charged hadron spectra for centrality selected d+Au collisions.</p>
Longitudinal density correlations of produced matter in Au+Au collisions at sqrt(s_NN)=200 GeV have been measured from the inclusive charged particle distributions as a function of pseudorapidity window sizes. The extracted \alpha \xi parameter, related to the susceptibility of the density fluctuations in the long wavelength limit, exhibits a non-monotonic behavior as a function of the number of participant nucleons, N_part. A local maximum is seen at N_part ~ 90, with corresponding energy density based on the Bjorken picture of \epsilon_Bj \tau ~ 2.4 GeV/(fm^2 c) with a transverse area size of 60 fm^2. This behavior may suggest a critical phase boundary based on the Ginzburg-Landau framework.
Weighted mean of corrected NBD $k$, $<k_c>$ as a function of pseudorapidity window size. The dominant sources systematic correlate with dead maps (corr.sys.(dead)) and two-track seperation cuts (corr.sys.(fake)). The total systematic error (uncorr.sys.) is the quadratic sum over all errors.
Weighted mean of corrected NBD $k$, $<k_c>$ as a function of pseudorapidity window size. The dominant sources systematic correlate with dead maps (corr.sys.(dead)) and two-track seperation cuts (corr.sys.(fake)). The total systematic error (uncorr.sys.) is the quadratic sum over all errors.
Fit results based on $k(\delta_{\eta})$=$1/{{2\alpha\xi}/{\delta_{\eta}}}$ ($\xi << \delta_{\eta}$).
Inclusive transverse momentum spectra of eta mesons in the range p_T~2-12 GeV/c have been measured at mid-rapidity (|\eta| < 0,35) by the PHENIX experiment at RHIC in p+p, d+Au and Au+Au collisions at sqrt(s_NN) = 200 GeV. The eta mesons are reconstructed through their eta--> \gamma\gamma channel for the three colliding systems as well as through the eta-->pi^0 pi+ pi- decay mode in p+p and d+Au collisions. The nuclear modification factor in d+Au collisions, R_dAu(p_T~1.0-1.1, suggests at most only modest p_T broadening (Cronin enhancement). In central Au+Au reactions, the eta yields are significantly suppressed, with R_AuAu(pT)~0.2. The ratio of eta to pi^0 yields is approximately constant as a function of p_T for the three colliding systems in agreement with the high-p_T world average of R_eta/pi^0 \approx 0.5 in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range of center-of-mass energies [sqrt(s_NN)~3-1800 GeV] as well as, for high scaled momentum x_p, in e+e- annihilations at sqrt(s)=91.2 GeV. These results are consistent with a scenario where high-p_T eta production in nuclear collisions at RHIC is largely unaffected by initial-state effects, but where light-quark mesons (pi^0:eta) are equally suppressed due to final-state interactions of the parent partons in the dense medium produced in Au+Au reactions.
Inelastic cross section measured in p+p at $\sqrt{s}$=200 GeV through $\eta \rightarrow \gamma \gamma$
Inelastic cross section measured in p+p at $\sqrt{s}$=200 GeV through $\eta \rightarrow \pi^{0} \pi^{+} \pi^{-}$
Inelastic cross section measured in d+Au at $\sqrt{s}$=200 GeV through $\eta \rightarrow \gamma \gamma$
The PHENIX experiment at RHIC has measured the invariant cross section for omega-meson production at mid-rapidity in the transverse momentum range 2.5 < p_T < 9.25 GeV/c in p+p and d+Au collisions at sqrt(s_NN) = 200 GeV. Measurements in two decay channels (omega --> pi^0 pi^+ pi^- and omega --> pi^0 gamma) yield consistent results, and the reconstructed omega mass agrees with the accepted value within the p_T range of the measurements. The omega/pi^0 ratio is found to be 0.85 +/- 0.05(stat) +/- 0.09(sys) and 0.94 +/- 0.08(stat) +/- 0.12(sys) in p+p and d+Au collisions respectively, independent of p_T . The nuclear modification factor R_dA is 1.03 +/- 0.12(stat) +/- 0.21(sys) and 0.83 +/- 0.21(stat) +/- 0.17(sys) in minimum bias and central (0-20%) d+Au collisions, respectively.
Invariant cross section of $\omega$ production in $p$+$p$ and $d$+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV measured in $\omega \rightarrow \pi^0\pi^+\pi^-$ and $\omega \rightarrow \pi^0\gamma$ decay channels.
Invariant cross section of $\omega$ production in $p$+$p$ and $d$+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV measured in $\omega \rightarrow \pi^0\pi^+\pi^-$ and $\omega \rightarrow \pi^0\gamma$ decay channels.
Invariant cross section of $\omega$ production in $p$+$p$ and $d$+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV measured in $\omega \rightarrow \pi^0\pi^+\pi^-$ and $\omega \rightarrow \pi^0\gamma$ decay channels.
Measurements of neutral pion production at midrapidity in sqrt(s_NN) = 200 GeV Au+Au collisions as a function of transverse momentum, p_T, collision centrality, and angle with respect to reaction plane are presented. The data represent the final pi^0 results from the PHENIX experiment for the first RHIC Au+Au run at design center-of-mass-energy. They include additional data obtained using the PHENIX Level-2 trigger with more than a factor of three increase in statistics over previously published results for p_T > 6 GeV/c. We evaluate the suppression in the yield of high-p_T pi^0's relative to point-like scaling expectations using the nuclear modification factor R_AA. We present the p_T dependence of R_AA for nine bins in collision centrality. We separately integrate R_AA over larger p_T bins to show more precisely the centrality dependence of the high-p_T suppression. We then evaluate the dependence of the high-p_T suppression on the emission angle \Delta\phi of the pions with respect to event reaction plane for 7 bins in collision centrality. We show that the yields of high-p_T pi^0's vary strongly with \Delta\phi, consistent with prior measurements. We show that this variation persists in the most peripheral bin accessible in this analysis. For the peripheral bins we observe no suppression for neutral pions produced aligned with the reaction plane while the yield of pi^0's produced perpendicular to the reaction plane is suppressed by more than a factor of 2. We analyze the combined centrality and \Delta\phi dependence of the pi^0 suppression in different p_T bins using different possible descriptions of parton energy loss dependence on jet path-length averages to determine whether a single geometric picture can explain the observed suppression pattern.
Neutral pion invariant yields as a function of $p_T$ measured in minimum bias and 9 centrality classes in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
Neutral pion invariant yields as a function of $p_T$ measured in minimum bias and 9 centrality classes in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
Neutral pion invariant yields as a function of $p_T$ measured in minimum bias and 9 centrality classes in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
We present azimuthal angle correlations of intermediate transverse momentum (1-4 GeV/c) hadrons from {dijets} in Cu+Cu and Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is broadened, non-Gaussian, and peaked away from \Delta\phi=\pi in central and semi-central collisions in all the systems. The broadening and peak location are found to depend upon the number of participants in the collision, but not on the collision energy or beam nuclei. These results are consistent with sound or shock wave models, but pose challenges to Cherenkov gluon radiation models.
The measured correlation $C(\Delta\phi)$ and the dijet correlation $J(\Delta\phi)$ in central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
Dijet correlations in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV.
Dijet correlations in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV.
The dependence of transverse momentum spectra of neutral pions and eta mesons with p_T <16 GeV/c and p_T < 12 GeV/c, respectively, on the centrality of the collision has been measured at mid-rapidity by the PHENIX experiment at RHIC in d+Au collisions at sqrt(s_(NN)) = 200 GeV. The measured yields are compared to those in p + p collisions at the same sqrt(s_(NN)) scaled by the number of underlying nucleon-nucleon collisions in d+Au. At all centralities the yield ratios show no suppression, in contrast to the strong suppression seen for central Au+Au collisions at RHIC. Only a weak p_T and centrality dependence can be observed.
Invariant yields at mid-rapidity for $\pi^0$ and $\eta$ in $d$+Au collisions as a function of $p_T$ for different centrality selections.
Invariant yields at mid-rapidity for $\pi^0$ and $\eta$ in $d$+Au collisions as a function of $p_T$ for different centrality selections.
Invariant yields at mid-rapidity for $\pi^0$ and $\eta$ in $d$+Au collisions as a function of $p_T$ for different centrality selections.
Muon production at forward rapidity (1.5 < |\eta| < 1.8) has been measured by the PHENIX experiment over the transverse momentum range 1 < p_T \le 3 GeV/c in sqrt(s) = 200 GeV p+p collisions at the Relativistic Heavy Ion Collider. After statistically subtracting contributions from light hadron decays an excess remains which is attributed to the semileptonic decays of hadrons carrying heavy flavor, i.e. charm quarks or, at high p_T, bottom quarks. The resulting muon spectrum from heavy flavor decays is compared to PYTHIA and a next-to-leading order perturbative QCD calculation. PYTHIA is used to determine the charm quark spectrum that would produce the observed muon excess. The corresponding differential cross section for charm quark production at forward rapidity is determined to be d\sigmac c^bar)/dy|_(y=1.6)=0.243 +/- 0.013 (stat.) +/- 0.105 (data syst.) ^(+0.049(-0.087) (PYTHIA syst.) mb.
Differential charm cross section at forward rapidity of 1.6 An additional +0.049 -0.087 systematic uncertainty associated with the PYTHIA normalization is not included in the values given.
Cross sections for mid-rapidity production of direct photons in p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are reported for 3 < p_T < 16 GeV/c. Next-to-leading order (NLO) perturbative QCD (pQCD) describes the data well for p_T > 5 GeV/c, where the uncertainties of the measurement and theory are comparable. We also report on the effect of requiring the photons to be isolated from parton jet energy. The observed fraction of isolated photons is well described by pQCD for p_T > 7 GeV/c.
Direct photon spectra with NLO pQCD calculations for three theory scales, $\mu$ and a comparison to the NLO pQCD calculations for $\mu$ = $p_T$.
Ratio of isolated direct photons to all direct photons from the $\pi^0$-tagging method.
Ratio of isolated direct photons to all direct photons from the $\pi^0$-tagging method.
Emission source functions are extracted from correlation functions constructed from charged pions produced at mid-rapidity in Au+Au collisions at sqrt(s_NN)=200 GeV. The source parameters extracted from these functions at low k_T, give first indications of a long tail for the pion emission source. The source extension cannot be explained solely by simple kinematic considerations. The possible role of a halo of secondary pions from resonance emissions is explored.
Correlation function, C(q) for $\pi^+\pi^+$ and $\pi^-\pi^-$ pairs.
Correlation function, C(q) for $\pi^+\pi^+$ and $\pi^-\pi^-$ pairs.
Correlation function, C(q) for $\pi^+\pi^+$ and $\pi^-\pi^-$ pairs.
The properties of jets produced in p+p collisions at sqrt(s)=200 GeV are measured using the method of two particle correlations. The trigger particle is a leading particle from a large transverse momentum jet while the associated particle comes from either the same jet or the away-side jet. Analysis of the angular width of the near-side peak in the correlation function determines the jet fragmentation transverse momentum j_T . The extracted value, sqrt(<j_T^2>)= 585 +/- 6(stat) +/- 15(sys) MeV/c, is constant with respect to the trigger particle transverse momentum, and comparable to the previous lower sqrt(s) measurements. The width of the away-side peak is shown to be a convolution of j_T with the fragmentation variable, z, and the partonic transverse momentum, k_T . The <z> is determined through a combined analysis of the measured pi^0 inclusive and associated spectra using jet fragmentation functions measured in e^+e^-. collisions. The final extracted values of k_T are then determined to also be independent of the trigger particle transverse momentum, over the range measured, with value of sqrt(<k_T^2>) = 2.68 +/- 0.07(stat) +/- 0.34(sys) GeV/c.
The $\chi^2(DOF)$ $\sigma_N$ and $\sqrt{<p^2_{out}>}$ values extracted for the correlation function in GeV/$c$.
The $\chi^2(DOF)$ $\sigma_N$ and $\sqrt{<p^2_{out}>}$ values extracted for the correlation function in GeV/$c$.
Measured widths of the near- and away-angle $\pi^0$ - $h^{\pm}$ correlation peaks for various trigger momenta.
We report on two-particle azimuthal angle correlations between charged hadrons at forward/backward (deuteron/gold going direction) rapidity and charged hadrons at mid-rapidity in deuteron-gold (d+Au) and proton-proton (p+p) collisions at sqrt(s_NN) = 200 GeV. Jet structures are observed in the correlations which we quantify in terms of the conditional yield and angular width of away side partners. The kinematic region studied here samples partons in the gold nucleus carrying nucleon momentum fraction x~0.1 to x~0.01. Within this range, we find no x dependence of the jet structure in d+Au collisions.
Azimuthal angle correlation functions. Note that the y-axis is zero-suppressed on the middle and bottom panels. In the additonal resource, the Gaussian widths from the fits and the signal to background ration integrated over $\pi$ - 1 < $\Delta\phi$ < $\pi$ + 1 are shown.
Conditional yields (CY) shown as a function of trigger particle pseudorapitidy for trigger particle $p_T$ from 2.5 to 4.0 and associated particle $p_T$ from 1.0 to 2.5 GeV/$c$. The additional $\pm$0.037 systematic error on the mid-rapidity $p+p$ point is from jet yield extraction. There is a 1% point-by-point systematical error on all points except central arm triggers. There is also a 10% systematic error for all data points due to the determination of associated particle efficiency. For $p + p$ point, forward and backward trigger are combined, so the results are identical.
$I_{dAu}$ vs. $p_T^{assoc}$ for different centrality, $p_T^{trig}$ and $\eta^{trig}$ bins.
PHENIX has measured the centrality dependence of mid-rapidity pion, kaon and proton transverse momentum distributions in d+Au and p+p collisions at sqrt(s_NN) = 200 GeV. The p+p data provide a reference for nuclear effects in d+Au and previously measured Au+Au collisions. Hadron production is enhanced in d+Au, relative to independent nucleon-nucleon scattering, as was observed in lower energy collisions. The nuclear modification factor for (anti) protons is larger than that for pions. The difference increases with centrality, but is not sufficient to account for the abundance of baryon production observed in central Au+Au collisions at RHIC. The centrality dependence in d+Au shows that the nuclear modification factor increases gradually with the number of collisions suffered by each participant nucleon. We also present comparisons with lower energy data as well as with parton recombination and other theoretical models of nuclear effects on particle production.
Mean number of binary collisions, particpating nucleons from the Au nucleus, number of collisions per participating deuteron nucleon, and trigger bias corrections for the $d$+Au centrality bins.
Transverse momentum in GeV/$c$ for $\pi^{\pm}$.
Transverse momentum in GeV/$c$ for $\pi^{\pm}$.
We present an improved measurement of the double helicity asymmetry for pi^0 production in polarized proton-proton scattering at sqrt(s) = 200 GeV employing the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The improvements to our previous measurement come from two main factors: Inclusion of a new data set from the 2004 RHIC run with higher beam polarizations than the earlier run and a recalibration of the beam polarization measurements, which resulted in reduced uncertainties and increased beam polarizations. The results are compared to a Next to Leading Order (NLO) perturbative Quantum Chromodynamics (pQCD) calculation with a range of polarized gluon distributions.
Run-3+Run-4 combined results on $A^{\pi^0}_{LL}$ versus mean $p_T$ in each bin. Not included in the figure/table: the correlated for all points scale systematic uncertainty of 18% (scales both the values and stat. uncertainties by the same factor).
Inclusive transverse momentum spectra of eta mesons have been measured within p_T = 2-10 GeV/c at mid-rapidity by the PHENIX experiment in Au+Au collisions at sqrt(s_NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au+Au, d+Au and p+p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality and p_T dependence of the suppression is common, within errors, for eta and pi^0. The ratio of eta to pi^0 spectra at high p_T amounts to 0.40 < R_eta/pi^0 < 0.48 for the three systems in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e^+e^- collisions.
Invariant $\eta$ yields as a function of transverse momentum for 3 centralities and MB Au+Au at $\sqrt{s_{NN}}$ = 200 GeV.
Invariant $\eta$ yields as a function of transverse momentum for 3 centralities and MB Au+Au at $\sqrt{s_{NN}}$ = 200 GeV.
Nuclear modification factors for $\eta$ in Au+Au centralities.
The PHENIX experiment has measured mid-rapidity transverse momentum spectra (0.4 < p_T < 5.0 GeV/c) of electrons as a function of centrality in Au+Au collisions at sqrt(s_NN)=200 GeV. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of pi^0 and eta mesons, were removed. The resulting non-photonic electron spectra are primarily due to the semi-leptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to non-photonic electrons in p+p collisions. A significant suppression of electrons at high p_T is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.
Inclusive and non photonic electrons invariant yield versus PT, for minimum bias reactions.
Non photonic electrons invariant yield versus PT for different ranges of centrality.
Nuclear modification factor as a function of PT, for 0-10% central reactions Note that the systematic error given is related to the the uncertainties in the p+p measurements.An additional systematic error, symmetrical on the + and - side, related to the uncertainties in the Au+Au measurement, is given in the second column. Another, PT-independant, 13%systematic error due to the uncertainty on the overlap function and the Pi0 yield normalization is to add.
Dihadron correlations at high transverse momentum in d+Au collisions at sqrt(s_NN) = 200 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). From these correlations we extract several structural characteristics of jets; the root-mean-squared (RMS) transverse momentum of fragmenting hadrons with respect to the jet sqrt(<j_T^2>), the mean sine-squared angle between the scattered partons <sin^2(phi_jj)>, and the number of particles produced within the dijet that are associated with a high-p_T particle (dN/dx_E distributions). We observe that the fragmentation characteristics of jets in d+Au collisions are very similar to those in p+p collisions and that there is also little dependence on the centrality of the d+Au collision. This is consistent with the nuclear medium having little influence on the fragmentation process. Furthermore, there is no statistically significant increase in the value of <sin^2(phi_jj)> from p+p to d+Au collisions. This constrains the amount of multiple scattering that partons undergo in the cold nuclear medium before and after a hard-collision.
Measured $\gamma\gamma$ invariant mass distribution for 6 < $p_T$ < 7 GeV/$c$ in central $d$+Au collisions.
The comparison of near-side yield, near-side width, far-side yield, and far-side width as a function of $p_T$ of charged hadrons. These are obtained for $\pi^{\pm}$ - $h^{\pm}$ correlation from PYTHIA, with a trigger pion of 6 - 10 GeV/$c$.
Fully corrected assorted charged pion-hadron conditional pair distributions for $d$+Au collisions centrality 0-80% and $p$+$p$ collisions. The trigger $\pi^{\pm}$s are within 5 < $p_{T,trig}$ < 10 GeV/$c$ and are correlated with hadrons with $p_{T,assoc}$ 0.4-1.0 GeV/$c$, 1.0-2.0 GeV/$c$, 2.0-3.0 GeV/$c$, and 3.0-5.0 GeV/$c$.
The invariant differential cross section for inclusive electron production in $p + p$ collisions at $\sqrt{s} = 200$~GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4 \le p_T \le 5.0$~GeV/$c$ in the central rapidity region ($|\eta| \le 0.35$). The contribution to the inclusive electron spectrum from semileptonic decays of hadrons carrying heavy flavor, {\it i.e.} charm quarks or, at high $p_T$, bottom quarks, is determined via three independent methods. The resulting electron spectrum from heavy flavor decays is compared to recent leading and next-to-leading order perturbative QCD calculations. The total cross section of charm quark-antiquark pair production is determined to be $\sigma_{c\bar{c}} = 0.92 \pm 0.15 {\rm (stat.)} \pm 0.54 {\rm (sys.)}$~mb.
Inclusive electron invariant differential cross section.
Non-photonic electron invariant cross section.
The azimuthal distribution of identified pi^0 and inclusive photons has been measured in sqrt{s_{NN}} = 200 GeV Au+Au collisions with the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). The second harmonic parameter (v_2) was measured to describe the observed anisotropy of the azimuthal distribution. The measured inclusive photon v_2 is consistent with the value expected for the photons from hadron decay and is also consistent with the lack of direct photon signal over the measured p_T range 1-6 GeV/c. An attempt is made to extract v_2 of direct photons.
The measured $v_2$ of $\pi^0$ ($v_2^{\pi^0}$) for 4 centrality selections.
The measured $v_2$ of inclusive photon ($v_2^{inclusive \gamma}$) for 4 centrality selections.
The expected photon $v_2$ from hadronic decay $v_2^{(b.g.)}$ and the subtracted $v_2$ quantity $R v_2^{(inclusive \gamma)}$ - $v_2^{(b.g.)}$.
J/psi production in d+Au and p+p collisions at sqrt(s_NN) = 200 GeV has been measured by the PHENIX experiment at rapidities -2.2 < y < +2.4. The cross sections and nuclear dependence of J/\psi production versus rapidity, transverse momentum, and centrality are obtained and compared to lower energy p+A results and to theoretical models. The observed nuclear dependence in d+Au collisions is found to be modest, suggesting that the absorption in the final state is weak and the shadowing of the gluon distributions is small and consistent with Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-based parameterizations that fit deep-inelastic scattering and Drell-Yan data at lower energies.
J/PSI differential cross section in P+P reactions( times di-lepton branching ratio B=5.9%) as a function of rapidity.
J/PSI nuclear modification factor RDA,as a function of rapidity.
Total cross-section for J/PSI production in P P reactions. The total cross section is estimated using a pythia calculation, normalized to our data. The di-lepton branching ratio used is 5.9%.The systematic error given is due to the fit. The choice of the PDF and model was estimated to have little impact in the value of the total cross section.
The transverse single-spin asymmetries of neutral pions and non-identified charged hadrons have been measured at mid-rapidity in polarized proton-proton collisions at sqrt(s) = 200 GeV. The data cover a transverse momentum (p_T) range 0.5-5.0 GeV/c for charged hadrons and 1.0-5.0 GeV/c for neutral pions, at a Feynman-x (x_F) value of approximately zero. The asymmetries seen in this previously unexplored kinematic region are consistent with zero within statistical errors of a few percent. In addition, the inclusive charged hadron cross section at mid-rapidity from 0.5 < p_T < 7.0 GeV/c is presented and compared to NLO pQCD calculations. Successful description of the unpolarized cross section above ~2 GeV/c using NLO pQCD suggests that pQCD is applicable in the interpretation of the asymmetry results in the relevant kinematic range.
Invariant cross section vs. $p_T$ for the production of charged hadrons at mid-rapidity.
Mid-rapidity neutral pion transverse single-spin asymmetry, $A_N$, vs. transverse momentum.
Mid-rapidity charged hadron transverse single-spin asymmetry, $A_N$, vs. transverse momentum.
Forum