Spin Physics Program at RHIC-PHENIX

Measurement of Longitudinal Spin Asymmetries From $W\rightarrow e$ Boson Decay in Polarized pp Collisions at $\sqrt{s}=500$ GeV at RHIC-PHENIX

We report the measurement of the parity violating single spin asymmetries for inclusive high transverse momentum electrons and positrons in polarized $p+p$ collisions at a center of mass energy of $\sqrt{s}=500$ GeV with the PHENIX detector at RHIC. These electrons are attributed to the decay of $W^\pm$ and $Z^0$ bosons, and measured production cross section is consistent with the expectations. The $W$ production is confirmed for the first time in $p+p$ collisions. Its spin asymmetry in the polarized $p+p$ collisions is a important probe for the quark flavor decomposition of the proton spin.

Recent PHENIX Results on pi+, pi-, and eta Production in polarized pp Collisions at RHIC at sqrt(s) = 200 GeV

Measurements of double helicity asymmetries for inclusive hadron production in polarized proton-proton collisions are sensitive to spin-dependent parton distribution functions, in particular to the gluon distribution function. This study focuses on double helicity asymmetries in eta and charged pion production at mid-rapidity, as well as on the eta cross section and fragmentation functions.

$ϕ$- meson Production at RHIC energies using the PHENIX Detector

Light vector mesons are among the most informative probes to understand the strongly coupled Quark Gluon Plasma created at RHIC. The suppression of light mesons at high transverse momentum, compared to expectations from scaled $p+p$ results, reflects the properties of the strongly interacting matter formed. The $ϕ$-meson is one of the probes whose systematic measurement in $p+p$, $d+Au$ and $Au+Au$ collisions can provide useful information about initial and final state effects on particle production. The mass, width and branching ratio of the $ϕ$-meson decay in the di-kaon and di-electron deca…

Exploring the Proton's Spin at PHENIX

In late 2001 the first polarized proton collisions at the Relativistic Heavy Ion Collider (RHIC) took place. The PHENIX experiment at RHIC has a broad program to investigate the spin structure of the proton. This program will be described, and first results will be presented.

Spin Physics with the PHENIX Detector System

The PHENIX experiment at RHIC has extended its scope to cover spin physics using polarized proton beams. The major goals of the spin physics at RHIC are elucidation of the spin structure of the nucleon and precision tests of the symmetries. Sensitivities of the spin physics measurements with the PHENIX detector system are reviewed.

Measurement of charm and bottom production in p+p collisions at $\sqrt{s}$ = 200 GeV at RHIC-PHENIX

RHIC-PHENIX has observed a large suppression pattern and azimuthal anisotropy of non-photonic electron at mid-rapidity ($\midη\mid<0.35$) in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. To understand these results and the interaction of heavy quarks in the hot and dense medium, experimental determination of production ratio of charm over bottom is one of the most important topics, since the behavior of bottom may differ from charm in the medium. We measured the ratio of charm over bottom and total cross section of bottom via partial reconstruction of D$^0$$\to$e$^+$ K$^-$ $ν_e$ decay in p+p …

The PHENIX Experiment at RHIC

The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented.

First measurement of the omega-meson production at RHIC by PHENIX

The PHENIX experiment at RHIC measured the omega-meson production in the range of pT from 2.5 GeV/c to 9.5 GeV/c in p+p and d+Au collision systems at sqrt{s_{NN}}=200 GeV. We present the consistent results of two independent measurements in decay channels omega-->pi^{0}pi^{+}pi^{-}$ and omega-->pi^{0}gamma. The omega/pi^{0} ratio was found to be 0.90+/-0.06. The Nuclear Modification Factor R_{dA} is 1.3+/-0.2 both in the Minimum Biased and (0%-20%) central event samples. The mass of the omega-meson was measured to be consistent with the PDG value within the errors of the measurement. We also m…

Results from PHENIX on Deuteron and Anti-Deuteron Production in Au+Au Collisions at RHIC

Results from the PHENIX Collaboration on the production of deuterons and anti-deuterons in collisions between gold nuclei at a nucleon-nucleon center-of-mass energy of sqrt(s) = 200 GeV are presented.

The PHENIX Decadal Plan: Crafting the Future of RHIC

After ten years of running, the PHENIX Collaboration is starting to lay out the compelling physics that RHIC, as the most versatile hadron collider in the world, will be well positioned to explore beyond the program planned for upgrades already in progress. As the fields that RHIC set out to investigate have advanced and evolved, new questions and directions have arisen at the frontiers of QCD, and we have exciting opportunities before us to continue to confront the challenges and surprises of strong interactions into the next decade. The latest thoughts of the PHENIX Collaboration on this ong…

Double Longitudinal Spin Asymmetry in Neutral Pion Production in Polarized p+p Collisions at sqrt(s)=200 GeV at PHENIX

A major goal of the RHIC spin program is to measure Δg, the gluon contribution to the proton's spin. Measurements by PHENIX of the double longitudinal spin asymmetry, A_LL, of the neutral pion production at mid-rapidity in polarized proton collisions have been shown to constrain Δg. Results from the 2005 RHIC run, as well as high p_T data from the 2006 RHIC run, are presented. The results disfavor maximal positive and negative values of Δg. A measurement of azimuthally independent double transverse spin asymmetry, A_TT, is also presented.

Transverse Spin at PHENIX: Results and Prospects

The Relativistic Heavy Ion Collider (RHIC), as the world's first and only polarized proton collider, offers a unique environment in which to study the spin structure of the proton. In order to study the proton's transverse spin structure, the PHENIX experiment at RHIC took data with transversely polarized beams in 2001-02 and 2005, and it has plans for further running with transverse polarization in 2006 and beyond. Results from early running as well as prospective measurements for the future will be discussed.

Anomalous ϕMeson Suppression in Au+Au Collisions at \sqrt{s_{NN}}=200 GeV Measured by the PHENIX Experiment at RHIC

The PHENIX experiment at RHIC has measured the ϕ-meson production at mid-rapidity in p+p, d+Au, Cu+Cu and Au+Au collisions at \sqrt{s_{NN}}=200 GeV via the K^+K^- decay mode. The transverse momentum spectra of the ϕ-meson and the nuclear modification factor as a function of centrality are reviewed here.

PHENIX plans for RHIC low energy run

PHENIX plans for low energy running are presented. Current detector setting makes it possible to measure dielectron spectra down to sqrt(s_NN)=39GeV, and photon/high pT hadron spectra down to below sub-injection energy (sqrt(s_NN)=5-10GeV). The upgrade of the trigger scheme after the installation of VTX detector will enable PHENIX to fully explore the sub-injection energy regime, starting 2011.

PHENIX Spin Program, Recent Results

Acceleration of polarized protons in the Relativistic Heavy Ion Collider (RHIC) provides a unique tool to study the spin structure of the nucleon. We give a brief overview of the PHENIX program to investigate the unknown gluon and flavor decomposed sea quark polarization in the proton, utilizing polarized proton collisions at RHIC. We report first results from the PHENIX experiment on transverse single-spin asymmetry in pi0 and charged hadron production and longitudinal double-spin asymmetry in pi0 production, at mid-rapidity.

Direct Photon Measurement at RHIC-PHENIX

Results on direct photon measurements from the PHENIX experiment at RHIC are presented. The direct photon yields for $p_T>$6 GeV/$c$ as a function of centrality in Au-Au collisions at $\sqrt{s_{NN}}$=200 GeV are found to be consistent with NLO pQCD calculation scaled by the number of binary collisions. The results suggest that the photons observed are emitted from the initial stage of hard scattering. Comparisons with several theoretical calculations are also presented.

Collectivity in small systems measured with PHENIX at RHIC

In this paper we show azimuthal particle correlations in three different small-system collisions with different intrinsic initial geometries. The simultaneous constraints of $v_2$ and $v_3$ in $p/d/^3$He$+$Au collisions definitively demonstrate that the $v_n$'s are correlated to the initial geometry. In addition, we find that hydrodynamical models which include QGP formation describe simultaneouly the elliptic and triangular flow data in a statistically acceptable manner in all three systems.

Electromagnetic emission from hot medium measured by the PHENIX experiment at RHIC

Electromagnetic radiation has been of interest in heavy ion collisions because they shed light on early stages of the collisions where hadronic probes do not provide direct information since hadronization and hadronic interactions occur later. The latest results on photon measurement from the PHENIX experiment at RHIC reflect thermodynamic properties of the matter produced in the heavy ion collisions. An unexpectedly large positive elliptic flow measured for direct photons can not be explained by any of the current models.

QCD hard scattering results from PHENIX at RHIC

Data on hadron production at high transverse momentum ($p_T>$ 2 GeV/$c$) in p+p, d+Au, and Au+Au collisions at $\sqrt{s_{NN}$ = 200 GeV from the PHENIX experiment at RHIC are reviewed. The single inclusive spectrum of light hadrons produced in central Au+Au reactions shows significant differences compared to p+p and d+Au collisions, and provides interesting information on the properties of the underlying QCD medium present in heavy-ion reactions at collider energies.

A Start-Timing Detector for the Collider Experiment PHENIX at RHIC-BNL

We describe a start-timing detector for the PHENIX experiment at the relativistic heavy-ion collider RHIC. The role of the detector is to detect a nuclear collision, provide precise time information with an accuracy of 50ps, and determine the collision point along the beam direction with a resolution of a few cm. Technical challenges are that the detector must be operational in a wide particle-multiplicity range in a high radiation environment and a strong magnetic field. We present the performance of the prototype and discuss the final design of the detector.

Femtoscopic results in Au+Au and p+p from PHENIX at RHIC

Ultra-relativistic gold-gold and proton-proton collisions are investigated in the experiments of the Relativistic Heavy Ion Collider (RHIC). In the last several years large amount of results were revealed about the matter created in these collisions. The latest PHENIX results for femtoscopy and correlations are reviewed in this paper. Bose-Einstein correlations of charged kaons in 200 GeV Au+Au collisions and of charged pions in 200 GeV p+p collisions are shown. They are both compatible with previous measurements of charged pions in gold-gold collisions, with respect to transverse mass or numb…

Highlights from RHIC Spin Physics Program

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory delivers the world's highest energy polarized proton-proton collisions at a center of mass energy up to 500 GeV and provides a unique opportunity to study the quark and gluon spin structure of the proton and QCD dynamics at high energy scale. RHIC has produced many exiting physics results in recent years. The latest data from RHIC significantly constrain the gluon spin contribution to the proton spin, and the parity violating single spin asymmetry are observed for the first time in W production by both the PHENIX and …

J/psi production at RHIC-PHENIX

The J/psi is considered to be among the most important probes for the deconfined quark gluon plasma (QGP) created by relativistic heavy ion collisions. While the J/psi is thought to dissociate in the QGP by Debye color screening, there are competing effects from cold nuclear matter (CNM), feed-downs from excited charmonia (chi_c and psi') and bottom quarks, and regeneration from uncorrelated charm quarks. Measurements that can provide information to disentangle these effects are presented in this paper.

Performance studies of the PHENIX Hadron Blind Detector at RHIC

Electron pairs or di-leptons in general are unique probes to study the hot and dense matter formed in relativistic heavy ion collisions at RHIC. Particularly, low mass di-leptons are sensitive to chiral symmetry restoration effects and to thermal radiation emitted by the plasma via virtual photons, providing a direct measurement of the quark gluon plasma temperature. But the experimental challenge is the huge combinatorial background created by $e^+e^-$ pairs from copiously produced $π^0$ Dalitz decay and $γ$ conversions. In order to reduce this background, a Hadron Blind Detector was proposed…

Energy and system size dependent heavy flavor measurements at PHENIX at RHIC

Heavy flavor production is an ideal tool to study the properties of the Quark Gluon Plasma (QGP). The heavy flavor production at the Relativistic Heavy Ion Collider (RHIC) has its unique kinematic coverage and different production mechanisms from the Larger Hadron Collider (LHC) measurements. Heavy flavor products created in heavy ion collisions experience the whole evolution of nuclear medium. It's critical to measure both open and closed heavy flavor products in different collision systems to isolate cold/hot nuclear medium effects and initial/final state interactions. We report recent heavy…

Single-Spin Transverse Asymmetry in Neutral Pion and Charged Hadron Production at PHENIX

The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) has measured the single-spin transverse asymmetry ($A_{N}$) for neutral pion and non-identified charged hadron production at $x_{F}\sim 0$ over a transverse momentum range of $\sim$ 0.5 to 5.0 GeV/c from polarized proton-proton interactions at a center of mass energy ($\sqrt{s}$) of 200 GeV. The asymmetries observed are consistent with zero.

Moments of net-charge multiplicity distribution in Au+Au collisions measured by the PHENIX experiment at RHIC

Beam Energy Scan (BES) program at RHIC is important to search for the existence of the critical point in the QCD phase diagram. Lattice QCD have shown that the predictions of the susceptibility of the medium formed in heavy-ion collisions can be sensitive to the various moments (mean ($μ$) =${<x>}$, variance ($σ^2$) = ${<(x-μ)^2>}$, skewness (S) = $\frac{<(x-μ)^3>}{σ^3}$ and kurtosis ($κ$) =$\frac{<(x-μ)^4>}{σ^4} -3$) of conserved quantities like net-baryon number ($Δ$B), net-electric charge ($Δ$Q) and net-strangeness ($Δ$S). Any non-monotonic behavior of the higher moments would confirm the e…

Detail study of the medium created in Au+Au collisions with high $p_T$ probes by the PHENIX experiment at RHIC

Recent results on high $p_T$ identified hadrons in Au+Au collisions from the PHENIX experiment are presented. The $R_{\rm AA}$ for $π^0$ and $η$ are found to be very consistent. The second and fourth order collective flow of $π^0$s have been measured and found that $v_4/v_2^2$ is consistent with the one observed in lower $p_T$ region. Assuming the suppression of the $π^0$ yield at highest $p_T$ arises from energy loss of partons, we found that the energy loss is $L^3$ dependent, where $L$ is the path length of the partons in the medium. The $δp_T/p_T$'s of high $p_T$ hadrons are computed from …

Systematic study of high $p_{\rm T}$ hadron production in small collision systems by the PHENIX experiment at RHIC

High $p_{\rm T}$ hadrons in the small systems of $d/^3$He+Au and $p$+Al/Au collisions have been measured at the midrapidity ($|η|<0.35$) as well as at the forward and backward rapidities ($1.2<|η|<2.4$) at $\sqrt{s_{NN}}$=200GeV. A clear system and centrality ordering in the $R_{p/d/{\rm HeA}}$ was observed for midrapidity $π^0$ production. Hadron $R_{\rm cp}$ as a function of rapidity in forward and backward regions show an opposite trend to what HIJING++ predicted. Together with the difference of $R_{\rm cp}$ in $p$+Al/Au collisions, the observation can be understood consistently with the me…

Single spin asymmetry in forward $pA$ collisions: Phenomenology at RHIC

We confront the theoretical result of single spin asymmetry (SSA) $A_N$ in forward $pA$ collisions $p^\uparrow A \to hX$ including the gluon saturation effect with the recent preliminary experimental data from the PHENIX and STAR collaborations at RHIC. While we find overall reasonable agreement with the STAR data, our results indicate that the strong nuclear suppression of the asymmetry $A_N\sim A^{-1/3}$ observed by the PHENIX collaboration cannot be explained within the present understanding of this problem.

In-Medium Modifications of Low-Mass Vector Mesons in PHENIX at RHIC

Measurements at RHIC have established the creation of a Quark Gluon Plasma (QGP) in most central heavy-ion collisions. An important tool to understand properties of the QGP is study of the spectral shapes of low-mass vector mesons (LVM's), $ρ$, $ω$ and $ϕ$, which can be modified in the medium by partial restoration of chiral symmetry. This modification may be accessed directly by measuring low-momentum LVM's via their decays into lepton pairs inside the hot matter. Since leptons are not subject to the strong interaction, they do not rescatter on their way out of the medium. The PHENIX experime…

Recent Heavy Flavor Results Utilizing the FVTX in PHENIX at RHIC

Heavy flavor and quarkona production are important hard probes to test the Quantum Chromodynamics (QCD) and measure the properties of the Quark Gluon Plasma (QGP) created in high energy heavy ion collisions. The new PHENIX mid- and forward-rapidity silicon vertex detectors provide precise Distance of Closest Approach (DCA) determination, allowing charm and bottom yields identification, and improve di-muon mass resolution for charmonia studies. The relative $ψ(2S)$ over $J/ψ$(1S) yields measured in $p$+$p$, $p$+Al and $p$+Au data at $\sqrt{s}=$200 GeV help us to understand final state effects o…

Quarkonia measurement in p+p and d+Au collisions at sqrt(s)=200 GeV by PHENIX Detector

We report new quarkonia measurements necessary to understand production mechanisms and cold nuclear matter effects in the yields observed at RHIC energy. Results obtained in p+p collisions collected during the 2006 RHIC Run include J/psi, Psi' and Upsilon differential cross sections as well as J/psi polarization. Revisited interpretations of the published J/psi nuclear modification factors and statistically improved observations in d+Au collisions taken in the 2008 Run are also discussed in the view of the recent understanding of the initial state effects and breakup cross section.

Neutral Pion Double Longitudinal Spin Asymmetry in Proton-Proton Collisions at sqrt(s)=200 GeV Using the PHENIX Detector

New results from polarized p-p collisions at sqrt(s)=200 GeV of double longitudinal spin asymmetry in pi0 production using the PHENIX detector in the 2005 RHIC run are presented. Both positive and negative maximal gluon polarization scenarios are inconsistent with the data. The data is consistent with small |Δg|, including Δg=0.

Energy dependent forward B $\rightarrow$ $J/ψ$ measurements in p+p collisions at PHENIX

The heavy flavor studies at RHIC help improve the knowledge of the bottom/charm quark production and can test Quantum Chromodynamics (QCD). Compared to the LHC/Tevatron, the RHIC heavy flavor production originates from different partonic sub-processes and has a complementary kinematic coverage. The PHENIX forward rapidity silicon vertex detector (FVTX) provides precise determination of the event vertex, tracking and the Distance of Closest Approach (DCA) of charged tracks. This detector allows direct access to the $B$ meson production via measurements of non-prompt $J/ψ\to μ^{+} + μ^{-}$ withi…

PHENIX实验中最近的$J/ψ$测量

Recent $J/ψ$ measurements at the PHENIX experiment

本文介绍了PHENIX实验在RHIC上对$J/ψ$的最新测量结果，包括前向产额、比值与各向异性，揭示了多部分子相互作用和QGP中重组机制对粲偶素产生的贡献。