Distributions of event-by-event fluctuations of the mean transverse momentum and mean transverse energy near mid-rapidity have been measured in Au+Au collisions at sqrt(s_NN) = 130 GeV at RHIC. By comparing the distributions to what is expected for statistically independent particle emission, the magnitude of non-statistical fluctuations in mean transverse momentum is determined to be consistent with zero. Also, no significant non-random fluctuations in mean transverse energy are observed. By constructing a fluctuation model with two event classes that preserve the mean and variance of the semi-inclusive p_T or e_T spectra, we exclude a region of fluctuations in sqrt(s_NN) = 130 GeV Au+Au collisions.
The $N_{tracks}$ distribution for the $0-10\%$ centrality class (data points) compared to the $N_{mix}$ distribution from the mixed event sample (curve).
The $M_{p_T}$ distributions for four different centrality classes. The curves are the random baseline mixed event distributions.
The residual distribution between the data and mixed event $M_{p_T}$ in units of standard deviations for all centrality classes. The total ${\chi}^2$ and the number of degrees of freedom for the $0-5\%$, $0-10\%$, $10-20\%$, $20-30\%$ centrality classes are 89.0/39, 155.7/40,163.3/47, and 218.4/61, respectively.
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>
We present a measurement of the double longitudinal spin asymmetry in inclusive pi^0 production in polarized proton-proton collisions at sqrt(s)=200 GeV. The data were taken at the Relativistic Heavy Ion Collider with average beam polarizations of 26%. The measurements are the first of a program to study the longitudinal spin structure of the proton, using strongly interacting probes, at collider energies. The asymmetry is presented for transverse momenta 1-5 GeV/c at mid-rapidity, where next-to-leading order perturbative quantum chromodynamic (NLO pQCD) calculations describe the unpolarized cross section well. The observed asymmetry is small and is compared with a NLO pQCD calculation with a range of polarized gluon distributions.
Double spin asymmetry for the raw signal ($\pi^0 + BG$), for the background ($BG$) and for $\pi^0$ background corrected; single spin asymmetry for $\pi^0$ background corrected; for the four $p_T$ bins.
Single spin raw asymmetry normalized by the beam polarization, $\epsilon$/$P$, as a function of azimuthal angle $\phi$, for forward neutron production.
The measured double spin asymmetry $A^{\pi^0}_{LL}$ versus mean $p_T$ of $\pi^0$s in each bin. Not included in the figure/table: the correlated for all points scale systematic uncertainty of 65% (scales values and stat. uncertainties of points by the same factor).
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.
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 $\pi^{\pm}$.
Transverse momentum spectra of charged hadrons with p_T < 8 GeV/c and neutral pions with p_T < 10 GeV/c have 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 up by the number of underlying nucleon-nucleon collisions in d+Au. The yield ratio does not show the suppression observed in central Au+Au collisions at RHIC. Instead, there is a small enhancement in the yield of high momentum particles.
Midrapidity $p_T$ spectra for charged hadrons.
Midrapidity $p_T$ spectra for $\pi^0$.
Nuclear modification factor $R_{dA}$ for $\pi^0$ in the PbGl and PbSc calorimeters in minimum bias $d$+$Au$.
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.
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, $N_{part}$.
Data from Au + Au interactions at sqrt(s_NN) = 130 GeV, obtained with the PHENIX detector at RHIC, are used to investigate local net charge fluctuations among particles produced near mid-rapidity. According to recent suggestions, such fluctuations may carry information from the Quark Gluon Plasma. This analysis shows that the fluctuations are dominated by a stochastic distribution of particles, but are also sensitive to other effects, like global charge conservation and resonance decays.
The normalized variance $v(Q)$as a function of $n_{ch}$.
The normalized variance $v(R)$ as a function of $n_{ch}$.
The normalized variance $v(Q)$ for different centrality classes.
Two-pion correlations in sqrt(s_NN)=130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k_T by the PHENIX experiment at RHIC. The k_T dependent transverse radii are similar to results from heavy ion collisions at sqrt(s_NN) = 4.1, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R_out/R_side) is consistent with unity and independent of k_T.
HBT radii for pion pairs as a function of $k_T$ measured at mid-rapidity for various energies for Au+Au collisions at $\sqrt{s_{NN}}$ = 130 GeV. Values used are from the Longitudinal Co-Moving System (LCMS) frame.
HBT radii for pion pairs as a function of $k_T$ measured at mid-rapidity for various energies for Au+Au collisions at $\sqrt{s_{NN}}$ = 130 GeV. Values used are from the Pair Center-of-Mass System (PCMS) frame.
The top panel shows the measured $R_{side}$ from identical pions for PHENIX. The bottom panel shows the ratio $R_{out}/R_{side}$ as a function of $k_T$. Longitudinal Co-Moving System (LCMS) frame for $\pi^+$
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