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.
The mean from the NBD fit as a function of $N_{part}$ for 200 GeV Au+Au collisions over the range 0.2 < $p_T$ < 2.0 GeV/$c$.
The mean from the NBD fit as a function of $N_{part}$ for 62.4 GeV Au+Au collisions over the range 0.2 < $p_T$ < 2.0 GeV/$c$.
PHENIX has measured the centrality dependence of charged hadron p_T spectra from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction of the contribution from hard scattering to high p_T hadron production. For central collisions the yield at high p_T is shown to be suppressed compared to binary nucleon-nucleon collision scaling of p+p data. This suppression is monotonically increasing with centrality, but most of the change occurs below 30% centrality, i.e. for collisions with less than about 140 participating nucleons. The observed p_T and centrality dependence is consistent with the particle production predicted by models including hard scattering and subsequent energy loss of the scattered partons in the dense matter created in the collisions.
The ratio $p/h$ represents the proton plus anti-proton yield relative to the total charged hadron multiplicity. This shows the $p_T$ dependence of $p/h$ for minimum bias events.
Differential elliptic flow (v_2) for phi mesons and (anti)deuterons (d^bar)d is measured for Au+Au collisions at sqrt(s_NN) = 200 GeV. The v_2 for phi mesons follows the trend of lighter pi^+/- and K^+/- mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The v_2 values for (d^bar)d suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of v_2 per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.
$v_2$ vs $KE_T$ for several identified particle species obtained in mid-central Au+Au collisions, and ${v_2}/{n_q}$ vs ${KE_T}/{n_q}$ for the same particle species.
$v_2$ vs $KE_T$ for several identified particle species obtained in mid-central Au+Au collisions, and ${v_2}/{n_q}$ vs ${KE_T}/{n_q}$ for the same particle species.
$v_2$ vs $KE_T$ for several identified particle species obtained in mid-central Au+Au collisions, and ${v_2}/{n_q}$ vs ${KE_T}/{n_q}$ for the same particle species.
The production of low mass e+e- pairs for m_{e+e-} < 300 MeV/c^2 and 1 < p_T <5 GeV/c is measured in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. Enhanced yield above hadronic sources is observed. Treating the excess as internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of direct photon yield over p+p is exponential in transverse momentum, with inverse slope T = 221 +/- 19 (stat) +/- 19 (syst) MeV. Hydrodynamical models with initial temperatures ranging from 300--600 MeV at times of ~ 0.6 - 0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at ~ 170 MeV.
The fraction of the direct photon component as a function of $p_T$.
We report on charged hadron production in deuteron-gold reactions at sqrt(s_NN) = 200 GeV. Our measurements in the deuteron-direction cover 1.4 < eta < 2.2, referred to as forward rapidity, and in the gold-direction -2.0 < eta < -1.4, referred to as backward rapidity, and a transverse momentum range p_T = 0.5-4.0 GeV/c. We compare the relative yields for different deuteron-gold collision centrality classes. We observe a suppression relative to binary collision scaling at forward rapidity, sensitive to low momentum fraction (x) partons in the gold nucleus, and an enhancement at backward rapidity, sensitive to high momentum fraction partons in the gold nucleus.
$R_{cp}$ as a function of $\eta$ for 1.5 < $p_T$ < 4.0 GeV/$c$ for different centrality classes. Systematic uncertainties which are point-to-point uncorrelated (sys-uncorr) and correlated (sys-corr) are shown.
Bose-Einstein correlations of charged kaons are measured for Au+Au collisions at sqrt(s_NN) = 200 GeV and are compared to charged pion probes, which have a larger hadronic scattering cross section. Three dimensional Gaussian source radii are extracted, along with a one-dimensional kaon emission source function. The centrality dependences of the three Gaussian radii are well described by a single linear function if N_part^1/3 with zero intercept. Imaging analysis shows a deviation from a Gaussian tail at r >~ 10 fm, although the bulk emission at lower radius is well-described by a Gaussian. The presence of a non-Gaussian tail in the kaon source reaffirms that the particle emission region in a heavy ion collision is extended, and that similar measurements with pions are not solely due to the decay of long-lived resonances.
Measured $C_2$($q_{inv}$) and restored $C_2$($q_{inv}$) from imaged $S(r)$, compared with angle-averaged Gaussian $C_2$($q_{inv}$) for charged kaon pairs measured for 0.3 < $k_T$ < 0.9 GeV/$c$ at 0-30% central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
Measured $C_2$($q_{inv}$) and restored $C_2$($q_{inv}$) from imaged $S(r)$, compared with angle-averaged Gaussian $C_2$($q_{inv}$) for charged kaon pairs measured for 0.3 < $k_T$ < 0.9 GeV/$c$ at 0-30% central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
Measured $C_2$($q_{inv}$) and restored $C_2$($q_{inv}$) from imaged $S(r)$, compared with angle-averaged Gaussian $C_2$($q_{inv}$) for charged kaon pairs measured for 0.3 < $k_T$ < 0.9 GeV/$c$ at 0-30% central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.
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.
$k_T$ dependence of extracted spheroidal source parameters for pion source functions (a) $R_T$ , (b) $a$, and (c) $\lambda$ for most central collisions & perhipheral collisions.
$k_T$ dependence of extracted spheroidal source parameters for pion source functions (a) $R_T$ , (b) $a$, and (c) $\lambda$ for most central collisions & perhipheral collisions.
A three-dimensional (3D) correlation function obtained from mid-rapidity, low pT pion pairs in central Au+Au collisions at sqrt(s_NN)=200 GeV is studied. The extracted model-independent source function indicates a long range tail in the directions of the pion pair transverse momentum (out) and the beam (long). Model comparisons to these distensions indicate a proper breakup time \tau_0 ~ 9 fm/c and a mean proper emission duration \Delta\tau ~ 2 fm/c, leading to sizable emission time differences (<|\Delta \tau_LCM |> ~ 12 fm/c), partly due to resonance decays. They also suggest an outside-in 'burning' of the emission source reminiscent of many hydrodynamical models.
Source function comparison between Therminator calculation and image for $S(r_x)$ in PCMS.
Source function comparison between Therminator calculation and image for $S(r_x)$ in PCMS.
Two particle correlations between identified meson and baryon trigger particles with 2.5 < p_T < 4.0 GeV/c and lower p_T charged hadrons have been measured at midrapidity by the PHENIX experiment at RHIC in p+p, d+Au and Au+Au collisions at sqrt(s_NN) = 200 GeV. The probability of finding a hadron near in azimuthal angle to the trigger particle is almost identical for leading mesons and baryons for non-central Au+Au. The yield for both trigger baryons and mesons is significantly higher in Au+Au than in p+p and d+Au, except for trigger baryons in central collisions. The baryon excess is likely to arise predominantly from hard scattering processes.
$p_T$ spectra of the near side associated charged hadrons corrected to the full jet yield for meson triggers at 2.5 < $p_T$ < 4.0 GeV/$c$ and $|\eta|$ < 0.35 for six centralities in Au+Au and $d$+Au collisions.
$p_T$ spectra of the near side associated charged hadrons corrected to the full jet yield for meson triggers at 2.5 < $p_T$ < 4.0 GeV/$c$ and $|\eta|$ < 0.35 for six centralities in Au+Au and $d$+Au collisions.
Azimuthal angle \Delta\phi correlations are presented for charged hadrons from dijets for 0.4 < p_T < 10 GeV/c in Au+Au collisions at sqrt(s_NN) = 200 GeV. With increasing p_T, the away-side distribution evolves from a broad to a concave shape, then to a convex shape. Comparisons to p+p data suggest that the away-side can be divided into a partially suppressed 'head' region centered at Delta\phi ~ \pi, and an enhanced 'shoulder' region centered at Delta\phi ~ \pi +/- 1.1. The p_T spectrum for the 'head' region softens toward central collisions, consistent with the onset of jet quenching. The spectral slope for the 'shoulder' region is independent of centrality and trigger p_T, which offers constraints on energy transport mechanisms and suggests that the 'shoulder' region contains the medium response to energetic jets.
$I_{AA}$ versus $p_T^B$ for four trigger $p_T$ bins in HR+SR ($|\Delta\phi - \pi|$ < $\pi/2$) and HR ($|\Delta\phi - \pi|$ < $\pi/6$).