Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMeasurements of multiparticle correlations in $d$$+$Au collisions at 200, 62.4, 39, and 19.6 GeV and $p$$+$Au collisions at 200 GeV and implications for collective behavior
174
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Recently, multiparticle-correlation measurements of relativistic $p/d/^3$He$+$Au, $p$$+$Pb, and even $p$$+$$p$ collisions have shown surprising collective signatures. Here we present beam-energy-scan measurements of 2-, 4-, and 6-particle angular correlations in $d$$+$Au collisions at $sqrt{s_{_{NN}}}$=200, 62.4, 39, and 19.6 GeV. We also present measurements of 2- and 4-particle angular correlations in $p$$+$Au collisions at $sqrt{s_{_{NN}}}$=200 GeV. We find the 4-particle cumulant to be real-valued for $d$$+$Au collisions at all four energies. We also find that the 4-particle cumulant in $p$$+$Au has the opposite sign as that in $d$$+$Au, indicating that the correlations are geometrical and therefore collective in origin. Further we find that the 6-particle cumulant agrees with the 4-particle cumulant in $d$$+$Au collisions at 200 GeV, which indicates that nonflow effects are subdominant and provides strong evidence of collectivity.
rate research
Read More
We present measurements of the elliptic flow, $v_2$, as a function of transverse momentum ($p_T$), pseudorapidity ($eta$), and centrality in $d$$+$Au collisions at $sqrt{s_{_{NN}}}=$200, 62.4, 39, and 19.6 GeV. The beam-energy scan of $d$$+$Au collisions provides a testing ground for the onset of flow signatures in small collision systems. We measure a nonzero $v_2$ signal at all four collision energies, which, at midrapidity and low $p_T$, is consistent with predictions from viscous hydrodynamic models. Comparisons with calculations from parton transport models (based on the {sc ampt} Monte Carlo generator) show good agreement with the data at midrapidity to forward ($d$-going) rapidities and low $p_T$. At backward (Au-going) rapidities and $p_T>1.5$ GeV/$c$, the data diverges from {sc ampt} calculations of $v_2$ relative to the initial geometry, indicating the possible dominance of nongeometry related correlations, referred to as nonflow. We also present measurements of the charged-particle multiplicity ($dN_{rm ch}/deta$) as a function of $eta$ in central $d$$+$Au collisions at the same energies. We find that in $d$$+$Au collisions at $sqrt{s_{_{NN}}}=$200 GeV the $v_2$ scales with $dN_{rm ch}/deta$ over all $eta$ in the PHENIX acceptance. At $sqrt{s_{_{NN}}}=$62.4, and 39 GeV, $v_2$ scales with $dN_{rm ch}/deta$ at midrapidity and forward rapidity, but falls off at backward rapidity. This departure from the $dN_{rm ch}/deta$ scaling may be a further indication of nonflow effects dominating at backward rapidity.
The PHENIX experiment has measured direct photons at $sqrt{s_{NN}}$ = 200 GeV in $p+p$, $d$+Au and Au+Au collisions. For $p_{T}$ $<$ 4 GeV/$c$, the internal conversion into $e^{+}e^{-}$ pairs has been used to measure the direct photons in Au+Au.
Measurements of the midrapidity transverse energy distribution, $dEt/deta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $sqrt{s_{_{NN}}}=200$ GeV and additionally for Au$+$Au collisions at $sqrt{s_{_{NN}}}=62.4$ and 130 GeV. The $dEt/deta$ 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, $mean{dEt/deta}/N_{rm part}$ increases with $N_{rm part}$, while $mean{dEt/deta}/N_{qp}$ is approximately constant for all three energies. This indicates that the two component ansatz, $dE_{T}/deta propto (1-x) N_{rm part}/2 + x N_{rm coll}$, 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 $dE_{T}/deta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distribution using two models that both reproduce the Au$+$Au data. However, while the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, the additive-quark model does not.
We report on K*0 production at mid-rapidity in Au+Au and Cu+Cu collisions at sqrt{s_{NN}} = 62.4 and 200 GeV collected by the Solenoid Tracker at RHIC (STAR) detector. The K*0 is reconstructed via the hadronic decays K*0 to K+ pi- and bar{K*0} to K-pi+. Transverse momentum, pT, spectra are measured over a range of pT extending from 0.2 GeV/c to 5 GeV/c. The center of mass energy and system size dependence of the rapidity density, dN/dy, and the average transverse momentum, <pT>, are presented. The measured N(K*0)/N(K) and N(phi)/N(K*0) ratios favor the dominance of re-scattering of decay daughters of K*0 over the hadronic regeneration for the K*0 production. In the intermediate pT region (2.0 < pT < 4.0 GeV/c), the elliptic flow parameter, v2, and the nuclear modification factor, RCP, agree with the expectations from the quark coalescence model of particle production.
In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|eta|<$ 1) and associated particles at forward rapidities (2.7 $<|eta|<$ 3.9) in p+p, d+Au and Au+Au collisions at $sqrt{s_{NN}} $= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence of Color Glass Condensate. In Au+Au collisions quark energy loss can be probed at large rapidities, which may be different from gluon energy loss measured at mid-rapidity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
