Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · nucl-ex/0510006

Measurement of low mass dielectron continuum in sqrt(s_NN)=200GeV Au+Au collisions with the PHENIX experiment at RHIC

Alberica Toia
View original source ↗Read source document ↗Export metadata ↓

Abstract

Electromagnetic probes are ideally suited to investigate hot and dense matter produced in high energy heavy ion collisions. They do not undergo strong interactions and thus probe the time evolution of the collision. The dielectron continuum is rich in physics. Dalitz decays of light hadrons and direct decays of vector mesons, which might be modified in the medium, and correlated charm decays contribute to the spectrum. Furthermore, exotic states, e.g quasi-particles predicted to exist in the medium only beyond the phase transition, might leave their footprint in the continuum. Although correlated e+e- pairs are rare, the 0.24 nb^-1 collected by PHENIX for Au+Au collisions at sqrt(s_NN)= 200 GeV in 2004 provides a significant sample to investigate the dilepton continuum. The continuum and its resonances are separated from the combinatorial background via an event mixing technique. Mass spectra are presented and compared with the expectations from decays of hadronic sources.

Explore related subjects

nucl-ex

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Alberica Toia. 2005-10-03. Measurement of low mass dielectron continuum in sqrt(s_NN)=200GeV Au+Au collisions with the PHENIX experiment at RHIC. https://doi.org/10.1016/j.nuclphysa.2006.06.128

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

First Measurement of Near-Threshold J/ψ Photoproduction on the Neutron

We report the first measurement of the total and t-differential cross sections for near-threshold J/$ψ$ photoproduction on the neutron, obtained with the CLAS12 detector at the Thomas Jefferson National Accelerator Facility. The measurements, performed using a liquid-deuterium target, also provide the incoherent total and t-differential cross sections on the bound proton, enabling the first direct comparison of near-threshold J/$ψ$ photoproduction on bound protons and neutrons. Interpreted within Vector Meson Dominance, holographic QCD, and GPD-based frameworks, the data allow for the investigation of the gluonic structure of bound nucleons. A comparison with free proton results reveals hints of modifications to the gluon structure of nucleons in the nuclear medium, within the assumptions of the extraction and on the underlying production mechanism. The comparison of bound neutron and bound proton cross sections provides new constraints on the near-threshold J/$ψ$ production mechanism, which is crucial in order to establish J/$ψ$ photoproduction as a probe of the nucleon's gluonic structure.

nucl-ex↗
arXiv2026

Photon-induced $J/ψ$ as a linearly polarized probe of collision geometry in relativistic heavy-ion collisions

In relativistic heavy-ion collisions, the linear polarization of quasi-real photons can correlate the spin orientation of photon-induced vector mesons with the collision geometry. To explore this sensitivity, we present the first measurement of the decay angular distribution of photon-induced $J/ψ$ with respect to the event plane in heavy-ion collisions with hadronic overlap. The analysis uses Ru+Ru and Zr+Zr collisions at a nucleon--nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=200$ GeV recorded by STAR. After correcting for the finite event-plane resolution and subtracting the residual hadronic contribution, we extract a negative second-order modulation, $A_2^{\rm phot} = -0.39 \pm 0.11~(\mathrm{stat.}) \pm 0.04~(\mathrm{sys.})$, for $|y^{ee}|<0.8$, $p_{\mathrm T}^{ee}<0.2~\mathrm{GeV}/c$, and 30--80% centrality. This modulation provides evidence that the $J/ψ$ polarization is correlated with the event plane, as expected for linearly polarized photons. The observed modulation establishes polarized $J/ψ$ photoproduction as a direct probe of the transverse orientation of the initial collision geometry.

nucl-ex↗
arXiv2026

Low-energy collective structure of $^{92,94}$Zr and $^{94}$Mo from ($e,e^{\prime}$) and ($p,p^{\prime}$) scattering I. Experimental results

This is the first of two papers discussing a new signature of quadrupole mixed-symmetry states in the vibrational nuclei $^{92,94}$Zr and $^{94}$Mo based on proton and neutron transition densities derived from the comparison of inelastic electron and proton scattering experiments. Results of the $(e,e^\prime)$ and $(p,p^\prime)$ experiments on these nuclei as well as $(p,p^\prime)$ data for other potential cases $^{96}$Mo and $^{70}$Zn are presented. Spin and parity quantum numbers of excited states are assigned based on angular distributions from the proton scattering data in comparison to calculations employing form factors from the collective model in distorted-wave Born approximation. Possible candidates of one-phonon fully symmetric and mixed-symmetry states as well as members of two-phonon multiplets are identified.

nucl-ex↗