A new calculation of R_{dAu} has been performed using the 2003 d+Au data and the higher-statistics 2005 p+p data. These nuclear modification factors are compared to calculations using nuclear-modified PDFs and a J/psi breakup cross section is extracted. These values are then used to project the cold nuclear matter effects in Au+Au collisions. Additionally, a more data-driven projection is performed.
The ratio of the $ψ'$ over the $J/ψ$ production cross section in the dielectron channel has been measured in $\sqrt{s}=$ 200 GeV $p+p$ collisions with the PHENIX detector at RHIC. The analysis is based on fitting of the dielectron invariant mass spectra in the area around the $J/ψ$ and $ψ'$ signals in order to extract a ratio $ψ'$ over $J/ψ$ of 0.019$\pm 0.005($stat$)\pm 0.002($sys$)$ and a fractional feed-down contribution to $J/ψ$ from $ψ^\prime$ of $8.6 \pm 2.5 %$.
The large mass of the charm quark, along with the abundance of J/psi mesons observed from proton-proton collisions at PHENIX, allow for new measurements which are sensitive to basic properties of QCD. Two measurements are presented in this document: a transverse single-spin asymmetry (SSA) of J/psi production and the angular distribution for decay leptons in various reference frames. The decay distribution is directly sensitive to the J/psi production mechanism, while the transverse SSA is also sensitive to the distribution of gluons in a transversely polarized proton. Taken together, the two …
The PHENIX experiment has shown that J/psis are suppressed in central Au+Au collisions at a center of mass energy per nucleon-nucleon collision sqrt s(NN) = 200 GeV, and that the suppression is larger at forward than at mid-rapidity. Part of this difference may be explained by cold nuclear matter effects but the most central collisions suggest that regeneration mechanisms could be at play. In 2007, PHENIX collected almost four times more Au+Au collisions at this energy than used for previous published results. Moreover, the addition of a new reaction plane detector allows a much better analysi…
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.
Single electrons from open heavy quarks and di-leptons from J/psi mesons have been studied systematically at RHIC/PHENIX using data from p + p, d + Au and Au + Au collisions at $\sqrt{s_{NN}}$ = 62.4 GeV, 130 GeV and 200 GeV. From the single electron study, the charm quark yield is found to scale with the number of binary collisions. This scaling has recently been confirmed using Au+Au collisions at 62.4 GeV. A new analysis shows that a high p_T suppression of single electrons is observed in Au + Au collisions at 200 GeV. This suppression suggests that heavy quarks lose significant energy in t…
Recent results indicate that the J/psi suppression pattern differs with rapidity showing a larger suppression at forward rapidity. J/psi suppression mechanisms based on energy density (such as color screening, interaction with co-movers, etc.) predict the opposite trend. On the other hand, it is expected that more c\bar{c} pairs should be available to form quarkonia at mid-rapidity via recombination. Some models provide a way to differentiate J/psi production from initially produced c\bar{c} pairs and final state recombination of uncorrelated pairs, via the rapidity and transverse momentum dep…
The PHENIX collaboration efforts towards constraining and understanding quarkonia production mechanisms are outlined. J/psi measurements and feed-down sources studies in p-p collisions at 200 GeV, together with their possible indications on the hadro-production mechanisms, are discussed. J/psi photo-production in ultra-peripheral collisions at 200 GeV is also examined. Finally, a glimpse of the first bottomonia results in minimum bias Au-Au collisions at 200 GeV and their implications are presented.
Three measurements that broaden the scope of the experimental investigation of quarkonia modifications in heavy ion collisions are presented. Although the current statistical precision on the first two measurements does not allow one to draw significant conclusions, J/$ψ$ elliptic flow and high pT suppression results are important proofs of principle measurements, and make the case for higher luminosities at RHIC. Finally, the first measurement of an upper limit on the nuclear modification R_AA of dielectrons in the $Υ$ mass region in Au+Au collisions is presented. The results show a significa…
The measurement of quarkonia production in relativistic heavy ion collisions provides a powerful tool for studying the properties of the hot and dense matter created in these collisions. To be really useful, however, such measurements must cover a wide range of quarkonia states and colliding species. The PHENIX experiment at RHIC has successfully measured J/psi, psi-prime, chi_c and Upsilon production in different colliding systems at various energies. In this talk I will present recent results from the PHENIX collaboration on charmonium production in d+Au, Cu+Au and U+U collisions at 200 GeV/…
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.
Quarkonia (J/psi, psi', chi_C, Upsilon) production provides a sensitive probe of gluon distributions and their modification in nuclei; and is a leading probe of the hot-dense (deconfined) matter created in high-energy collisions of heavy ions. We will discuss the physics of quarkonia production in the context of recent p+p measurements at PHENIX. We next discuss Cold-Nuclear Matter (CNM) effects as seen in our measurements in $d+Au$ collisions - both for intrinsic physics such as gluon saturation and final-state dissociation, and as a baseline for studies in nucleus-nucleus collisions. Then we…
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.
Recent results from the PHENIX experiment at RHIC are presented. In this second part of the overview we discuss new results on direct photon production at low p_T in Au+Au collisions and a systematic study of J/psi production in various systems. Finally we summarize new results on the modification of jets in the medium.
We present a new analysis of J/psi production yields in deuteron-gold collisions at sqrt(s_NN) = 200 GeV using data taken by the PHENIX experiment in 2003 and previously published in [S.S. Adler et al., Phys. Rev. Lett 96, 012304 (2006)]. The high statistics proton-proton J/psi data taken in 2005 is used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors R_dAu. A suppression of J/psi in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial state …
This contribution presents the latest results on heavy quarkonia (j/psi and upsilon) production in d+A and A+A collisions at RHIC at a center of mass energy per nucleon-nucleon collision sqrt(s_NN) = 200 GeV, measured by the PHENIX experiment, as well as their implications in terms of understanding cold nuclear matter effects and the possible formation of a quark gluon plasma in central $\auau$ collisions.}
First results are presented from J/Psi -> ee and J/Psi -> μμmeasurements by the PHENIX experiment at RHIC. These results are from a preliminary analysis of dielectrons from AuAu and pp data and dimuons from pp data measured in the RHIC run 2. A total cross section for J/Psi production in sqrt{s} = 200 GeV pp collisions of 3.8 \pm 0.6 (stat) \pm 1.3 (sys) microbarns is found. The J/Psi -> ee yield is presented versus number of binary collisions.
The PHENIX experiment has measured single electron spectra at RHIC in proton-proton (p-p), deuteron-gold (d-Au), and gold-gold (Au-Au) collisions at an available energy per nucleon-nucleon pair of sqrt{s_NN} = 200 GeV. Contributions from photonic sources, i.e. Dalitz decays of light mesons and photon conversions, are subtracted from the inclusive spectra. The remaining non-photonic single electron spectra are dominated by semileptonic decays of particles carrying heavy flavor. Implications of these systematic measurements for heavy flavor production in cold and hot nuclear systems are discusse…
The PHENIX experiment at RHIC has measured single electron spectra in proton-proton, deuteron-gold and gold-gold collisions at sqrt(s_NN)=200 GeV. The photonic contribution (photon conversions and Daltiz decays) is subtracted from the inclusive spectra resulting in non-photonic electron spectra. The principal source of non-photonic electrons is the semi-leptonic decay of charm and bottom mesons. The implications for heavy flavor production in hot and cold nuclear systems are discussed.
PHENIX has measured the dielectron continuum in sqrt(s_(NN))=200 GeV Au+Au and p+p collisions. In minimum bias Au+Au collisions the dielectron yield in the mass range between 150 and 750 MeV/c^2 is enhanced by a factor of 3.4 +/- 0.2(stat.) +/- 1.3(syst.) +/- 0.7(model) compared to the expectation from our model of hadron decays that well reproduces the mass spectrum in p+p collisions. The integrated yield increases faster with the centrality of the collisions than the number of participating nucleons, suggesting emission from scattering processes in the dense medium. The continuum yield betwe…
Understanding the detailed production and hadronization mechanisms for heavy quarkonia and their modification in a nuclear environment presents one of the major challenges in QCD. Calculations including nuclear-modified parton distribution functions (nPDFs) and fitting of break-up cross sections (sigma_breakup) as parameters have been successful at describing many features of J/psi modification in proton(deuteron)-nucleus collisions. In this paper, we extend these calculations to explore different geometric dependencies of the modification and confront them with new experimental results from t…
The production of deuterons and antideuterons in the transverse momentum range 1.1 < p_T < 4.3 GeV/c at mid-rapidity in Au + Au collisions at sqrt(s_NN)=200 GeV has been studied by the PHENIX experiment at RHIC. A coalescence analysis comparing the deuteron and antideuteron spectra with those of protons and antiprotons, has been performed. The coalescence probability is equal for both deuterons and antideuterons and increases as a function of p_T, which is consistent with an expanding collision zone. Comparing (anti)proton yields p_bar/p = 0.73 +/- 0.01, with (anti)deuteron yields: d_bar/d = 0…
Deuteron-gold collisions provide insights into the nuclear structure function and a valuable baseline for Au+Au collisions. Measurement of the nuclear modification factor, R_{dAu}, in d+Au in the PHENIX central arms for hadrons and photons allows us to disentangle cold nuclear matter effects from the hot medium effects that are important in Au+Au collisions. In addition, the d+Au system can yield important insights into the gluonic structure of the Au nucleus. RHIC experiments have previously measured suppression of forward rapidity particle production relative to p+p scaled by the number of b…
Yields for J/psi production in Cu+Cu collisions at sqrt (s_NN)= 200 GeV have been measured by the PHENIX experiment over the rapidity range |y| < 2.2 at transverse momenta from 0 to beyond 5 GeV/c. The invariant yield is obtained as a function of rapidity, transverse momentum and collision centrality, and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data provide greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, providing a key constraint that is needed for disentangling c…
We study inclusive heavy quarkonium production with definite polarizations in polarized proton-proton collisions using the non-relativistic QCD color-octet mechanism. We present results for rapidity distributions of cross sections and spin asymmetries for the production of J/psi and psi' with specific polarizations in polarized p-p collisions at \sqrt s = 200 GeV and 500 GeV at the RHIC within the PHENIX detector acceptance range.
We update the study of the polarisation of J/psi produced in proton-proton collisions at RHIC at sqrt(s)=200 GeV using the QCD-based Colour-Singlet Model (CSM), including next-to-leading order partonic matrix elements from gluon and light quark fusion and leading-order contributions from charm-quark initiated processes. To do so, we also evaluate the corresponding cross section differential in P_T which agrees qualitatively with the measurements of PHENIX in the central and forward regions at low P_T -- for instance below 2 GeV --, while emphasising the need for Initial State Radiation (ISR) r…
Heavy quarks are good probes of the hot and dense medium created in relativistic heavy ion collisions since they are mainly generated early in the collision and interact with the medium in all collision stages. In addition, heavy flavor quarkonia production is thought to be uniquely sensitive to the deconfined medium of the Quark Gluon Plasma (QGP) through color screening. Heavy quark production has been studied by the PHENIX experiment at RHIC via measurements of single leptons from semi-leptonic decays, in both the electron channel at mid-rapidity and in the muon channel at forward rapidity.…
Interpreting the J/psi suppression reported in nucleus--nucleus collisions at SPS and RHIC requires the quantitative understanding of cold nuclear matter effects, such as the inelastic rescattering of J/psi states in nuclei or the nuclear modification of parton densities. With respect to our former Glauber analysis, we include in the present work the new PHENIX d--Au measurements, and analyze as well all existing data using the EPS08 nuclear parton densities recently released. The largest suppression reported in the new PHENIX analysis leads in turn to an increase of sigma from 3.5 +/- 0.3 mb …
Heavy quarks (charm and bottom) are good probes of the hot and dense medium created in relativistic heavy ion collisions since they are mainly generated at the beginning of collisions and interact with the media in all collision stages. In addition, heavy flavor quarkonia production is thought to be uniquely sensitive to the deconfined medium of the Quark Gluon Plasma (QGP) through color screening. Heavy quark production has been studied by the PHENIX experiment at RHIC via measurements of single leptons from semi-leptonic decays in both the electron channel at mid-rapidity and in the muon cha…
We have carried out a wide study of Cold Nuclear Matter (CNM) effects on J/Psi production in d+Au, Cu+Cu and Au+Au collisions at sqrt(s_NN)=200 GeV. We have studied the effects of three different gluon-shadowing parametrisations, using the usual simplified kinematics for which the momentum of the gluon recoiling against the J/Psi is neglected as well as an exact kinematics for a 2 -> 2 process, namely g+g -> J/psi+g as expected from LO pQCD. We have shown that the rapidity distribution of the nuclear modification factor R_dAu, and particularly its anti-shadowing peak, is systematically shifted…
First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The yield of J/Psi's measured in the PHENIX experiment via electron-positron decay pairs at mid-rapidity for Au-Au reactions at sqrt(s_NN) = 200 GeV are analyzed as a function of collision centrality. For this analysis we have studied 49.3 million minimum bias Au-Au reactions. We present the J/Psi invariant yield dN/dy for peripheral and mid-central reactions. For the most central collisions where we observe no signal above background, we quote 90% confidence level u…
High energy ultra-peripheral collisions (UPC) of heavy-ions generate strong electromagnetic fields which open the possibility to study gamma-gamma and gamma-nucleus processes in a kinematic regime so far unexplored. We report on preliminary PHENIX results of J/Psi and high-mass e+e- photoproduction at mid-rapidity in coherent electromagnetic Au+Au interactions at sqrt(s_NN) = 200 GeV tagged with forward neutron emission from the Au* dissociation.
J/Psi production in p+p collisions at sqrt(s) = 200 GeV has been Measured in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over a rapidity range of -2.2 < y < 2.2 and a transverse momentum range of 0 < pT < 9 GeV/c. The statistics available allow a detailed measurement of both the pT and rapidity distributions and are sufficient to constrain production models. The total cross section times branching ratio determined for J/Psi production is B_{ll} sigma_pp^J/psi = 178 +/- 3(stat) +/- 53(syst) +/- 18(norm) nb.
J/psi production has been measured in proton-proton collisions at sqrt(s)= 200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at RHIC. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) micro barns. The mean transverse momentum is 1.80 +/- 0.23(stat) +/- 0.16(sys) GeV/c.
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/ψproduction 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 parameteri…
The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured J/psi production for rapidities 2.2 < y < 2.2 in Au+Au collisions at sqrt(s_NN) = 200 GeV. The J/psi invariant yield and nuclear modification factor R_AA as a function of centrality, transverse momentum and rapidity are reported. A suppression of J/psi relative to binary collision scaling of proton-proton reaction yields is observed. Models which describe the lower energy J/Psi data at the Super Proton Synchrotron (SPS) invoking only J/psi destruction based on the local medium density would predict a significantly…
We report on leptonic observables by the PHENIX experiment from data taken during Run II at the Relativistic Heavy Ion Collider (RHIC). We show first results on phi -> K+K-, e+e-, low and intermediate mass dielectron continuum, single electrons from charm, and J/psi yields in proton-proton and Au-Au collisions at sqrt{s_{NN}}=200 GeV.
Predictions of J/Psi formation at RHIC via "off-diagonal" combinations of charm and anticharm quarks in a region of color deconfinement are confronted with initial data from the PHENIX collaboration. We find that the measured centrality behavior places significant constraints on the various parameters which control model calculations of J/Psi formation. Within present statistical and systematic uncertainties, one can map out a region of parameter space within which the contribution of formation in a deconfined phase is allowed. As these uncertainties decrease and new data from d-Au interaction…
A parameter-free calculation for J/Psi suppression in pA collisions, based on the dipole description, is confronted with the new data from the PHENIX experiment. Achieving good agreement, we employed this model predicting the contribution of initial state interactions (ISI) to J/Psi suppression in AA collisions. Such a transition from pA to AA is not straightforward, since involves specific effects of double color filtering and boosting of the saturation scale. Relying on this refined ISI contribution, we updated the previous analysis of RHIC data on J/Psi production in Cu-Cu and Au-Au collisi…
The current normalization of the cross section of inclusive high-pT particle production in deuteron-gold collisions measured RHIC relies on Glauber calculations for the inelastic d-Au cross section. These calculations should be corrected for diffraction. Moreover, they miss the Gribov's inelastic shadowing which makes nuclei more transparent (color transparency). The magnitude of this effect rises with energy and it may dramatically affect the normalization of the RHIC data. We evaluate these corrections employing the light-cone dipole formalism and found a rather modest corrections for the cu…
We consider the J/Psi production in proton (deuteron) -- nucleus collisions at high energies. We argue that the production mechanism in this case is different from that in pp collisions due to gluon saturation in the nucleus and formation of the Color Glass Condensate. At forward rapidities (in the proton fragmentation region), the production of J/Psi is increasingly suppressed both as a function of rapidity and centrality. On the other hand, at backward rapidities at RHIC (in the fragmentation region of the nucleus) the coherent effects lead to a modest enhancement of the production cross sec…
The field of Diffraction Dissociation, which is the subject of this workshop, began 50 years ago with the analysis of deuteron stripping in low energy collisions with nuclei. We return to the subject in a modern context- deuteron dissociation in $\sqrt{s_{NN}}= 200$ GeV d-Au collisions recorded during the 2003 RHIC run in the PHENIX experiment. At RHIC energy, d$\to$n+p proceeds predominantly (90%) through Electromagnetic Dissociation and the remaining fraction via the hadronic shadowing described by Glauber. Since the dissociation cross section has a small theoretical error we adopt this proc…
The heavy ion physics approach to global event characterization has led us to instrument the forward region in the PHENIX experiment at RHIC. In heavy ion collisions this coverage yields a measurement of the "spectator" energy and its distribution about the beam direction. This energy flow is the basis of event-by-event determination of the centrality and reaction plane which are key to analyzing particle production in heavy ion collisions. These same tools have also enabled a unique set of measurements on inelastic diffraction with proton, deuteron and gold ion beams in the PHENIX experiment.…
Measuring the rate of muon capture in hydrogen provides one of the most direct ways to study the axial current of the nucleon. The MuCap experiment uses a negative muon beam stopped in a time projection chamber operated with ultra-pure hydrogen gas. Surrounded by a decay electron detector, the lifetime of muons in hydrogen can be measured to determine the singlet capture rate Lambda_s to a final precision of 1%. The capture rate determines the nucleon's pseudoscalar form factor g_p. A first result, g_p = 7.3 +- 1.1, has been published and the final analysis of the full statistics will reduce t…
Charmonium is a prominent probe of the Quark-Gluon Plasma (QGP), expected to be formed in ultrarelativistic heavy-ion (A-A) collisions. It has been predicted that the J/psi(c-cbar) particle is dissolved in the deconfined medium created in A-A systems. However this suppression can be counterbalanced via regeneration of the charm/anti-charm bound state in QGP or via statistical production at the phase boundary. At LHC energies, the latter mechanisms are expected to play a more important role, due to a charm production cross section significantly larger than at lower energies. Measurements obtain…
The transverse momentum spectra of charged particles produced in proton(deuteron)-nucleus and nucleus-nucleus collisions at high energies are analyzed by the Hagedorn thermal model and the standard distribution in terms of multi-component. The experimental data measured in central and peripheral gold-gold (Au-Au) and deuteron-gold ($d$-Au) collisions by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC), as well as in central and peripheral lead-lead (Pb-Pb) and proton-lead ($p$-Pb) collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) are fitted by the t…
Heavy-quark production provides a sensitive probe of the gluon structure of nucleons and its modication in nuclei. It is also a key probe of the hot-dense matter created in heavy-ion collisions. We will discuss the physics issues involved, as seen in quarkonia and open heavy-quark production, starting with those observed in proton-proton collisions. Then cold nuclear matter effects on heavy-quark production including shadowing, gluon saturation, energy loss and absorption will be reviewed in the context of recent proton-nucleus and deuteron-nucleus measurements. Next we survey the most recent …
Hard scattering yields in centrality-selected proton-- and deuteron--nucleus ($p$+A) collisions are generally compared to nucleon--nucleon ($NN$) cross-sections scaled to the appropriate partonic luminosity using geometric models derived from an analysis of minimum bias $p$+A interactions. In general, these models assume that hard process rates and the magnitude of the soft event activity in the underlying $NN$ collisions is uncorrelated. When included, these correlations influence the measured yield in a nominal centrality interval, an effect typically referred to as a "centrality bias". In t…
The PHENIX experiment has measured the dielectron continuum in sqrt{s_NN} = 200 GeV Au+Au collisions. In minimum bias collisions the dielectron yield in the mass range between 150 and 750 MeV/c^2 is enhanced by a factor of 3.4 +/- 0.2(stat.) +/- 1.3(syst.) +/- 0.7(model) compared to the expectation from our model of hadron decays. The integrated yield increases faster with the centrality of the collisions than the number of participating nucleons, suggesting emission from scattering processes in the hot and dense medium. The continuum yield between the masses of the phi and the J/psi mesons is…
The understanding of few-nucleon systems at low energies is essential, e.g. for accurate predictions of element abundances in big-bang and stellar fusion. Novel effective field theories, taking only nucleons, or nucleons and pions as explicit degrees of freedom, provide a systematic approach, permitting an estimate of theoretical uncertainties. Basic constants parameterising the short range physics are derived from only a handful of experimental values. The doublet neutron scattering length a_2 of the deuteron is particularly sensitive to a three-nucleon contact interaction, but experimentally…
Global analysis has been performed within the next-to-leading order in Quantum Chromodynamics (QCD) to determine polarized parton distributions with new experimental data in spin asymmetries. The new data set includes JLab, HERMES, and COMPASS measurements on spin asymmetry A_1 for the neutron and deuteron in lepton scattering. Our new analysis also utilizes the double-spin asymmetry for pi^0 production in polarized pp collisions, A_{LL}^{pi^0}, measured by the PHENIX collaboration. Because of these new data, uncertainties of the polarized PDFs are reduced. In particular, the JLab, HERMES, and…
Results from the PHENIX experiment at RHIC in p-p and Au+Au collisions are reviewed from the perspective of measurements in p-p collisions at the CERN-ISR which serve as a basis for many of the techniques used. Issues such as J/Psi suppression and hydrodynamical flow in A+A collisions require data from LHC-Ions for an improved understanding. Suppression of high pT particles in Au+Au collisions, first observed at RHIC, also has unresolved mysteries such as the equality of the suppression of inclusive pi0 (from light quarks and gluons) and direct-single electrons (from the decay of heavy quarks)…
We report on the potentialities offered by a fixed-target experiment at the LHC using the proton and ion LHC beams (AFTER@LHC project) regarding the study of J/psi exclusive-photoproduction in pA and AA collisions. The foreseen usage of polarised targets (hydrogen, deuteron, helium) gives access to measurements of the Single-Transverse-Spin Asymmetries of this exclusive process, therefore allowing one to access the helicity-flip Generalised Parton Distribution (GPD) Eg. We detail the expected yields of photoproduced J/psi in proton-hydrogen and lead-hydrogen collisions and discuss the statisti…
PHENIX has measured the e^+e^- pair continuum in sqrt(s_NN)=200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e^+e^- yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate mass region, between the masses of the phi and the J/psi meson, the yield is consistent with expectations from correlated c^bar-c production, though other mechanisms are not ruled out. In the low mass region (below the phi) the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, …
We present measurements of J/psi yields in d+Au collisions at sqrt(s_NN) = 200 GeV recorded by the PHENIX experiment and compare with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/psi rapidity (-2.2 < y < 2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. To remove model dependent systematic uncertainties we also compare the data to a simple geometric model. We find that calc…
Heavy quarkonia are observed to be suppressed in relativistic heavy ion collisions relative to their production in p+p collisions scaled by the number of binary collisions. In order to determine if this suppression is related to color screening of these states in the produced medium, one needs to account for other nuclear modifications including those in cold nuclear matter. In this paper, we present new measurements from the PHENIX 2007 data set of J/psi yields at forward rapidity (1.2<|y|<2.2) in Au+Au collisions at sqrt(s_NN)=200 GeV. The data confirm the earlier finding that the suppressio…
We collected the experimental data of transverse momentum spectra of identified particles produced in proton-proton ($p$-$p$), deuteron-gold ($d$-Au or $d$-$A$), gold-gold (Au-Au or $A$-$A$), proton-lead ($p$-Pb or $p$-$A$), and lead-lead (Pb-Pb or $A$-$A$) collisions measured by the ALICE, CMS, LHCb, NA49, NA61/SHINE, PHENIX, and STAR collaborations at different center-of mass energies. The multisource thermal model at the quark level or the participant quark model is used to describe the experimental data. The free parameters, the effective temperature $T$, entropy index-related $n$, and rev…
We study the effect of nuclear matter in Upsilon production in dAu collisions at RHIC and pPb collisions at the LHC. We find that the nuclear modification factor, R^Upsilon_dAu, measured at RHIC is not satisfactorily reproduced by the conventional effects used in the literature, namely the modification of the gluon distribution in bound nucleons and an --effective-- survival probability for a bound state to escape the nucleus. In particular, we argue that this probability should be close to 1 as opposed to the J/psi case. We note that, at backward rapidities, the unexpected suppression of R^Up…
