相关论文: Electron-Positron Production in Ultra-Peripheral H…
The STAR collaboration has observed an excess production of $e^+e^-$ pairs in relativistic heavy ion collisions, over the expectations from hadronic production models. The excess pairs have transverse momenta $p_T < 150\ {\rm MeV}/c$ and…
We present the first data on $e^+e^-$ pair production accompanied by nuclear breakup in ultra-peripheral gold-gold collisions at a center of mass energy of 200 GeV per nucleon pair. The nuclear breakup requirement selects events at small…
Measurements of exclusive $J/\psi$, $\psi(2s)$, and electron-positron ($e^{+}e^{-}$) pair photoproduction in Au$+$Au ultra-peripheral collisions are reported by the STAR experiment at $\sqrt{s_{_\mathrm{NN}}}=200~\rm{GeV}$. We report…
We report measurements for coherent rho^0 production, AuAu->AuAu rho^0, and coherent rho^0 and e^+e^- pair production accompanied by mutual nuclear Coulomb excitation, AuAu->Au*Au* rho^0 and AuAuee, in ultra-peripheral relativistic…
In ultra-peripheral heavy ion collisions (UPCs), the broad energy spectrum of photons enables a variety of physical processes, ranging from lepton pair production to giant dipole resonances (GDRs). In this work, we evaluate production of…
We present recent STAR results on photoproduction in ultra-peripheral relativistic heavy ion collisions. In these collisions the impact parameter of the beam particles is larger than the sum of their nuclear radii, so that they interact via…
We present a measurement of pi^+pi^-pi^+pi^- photonuclear production in ultra-peripheral Au-Au collisions at sqrt(s_{NN}) = 200 GeV from the STAR experiment. The pi^+pi^-pi^+pi^- final states are observed at low transverse momentum and are…
The STAR Collaboration reports on the photoproduction of $\pi^+\pi^-$ pairs in gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair. These pion pairs are produced when a nearly-real photon emitted by one ion scatters from…
The STAR collaboration has observed an excess production of electron-positron pairs which have transverse momenta pperp < 150 MeV/c in peripheral gold-gold and uranium-uranium collisions. ALICE has also reported on an excess of mu mu pairs…
We report on measurements of dielectron ($e^+e^-$) production in Au$+$Au collisions at a center-of-mass energy of 200 GeV per nucleon-nucleon pair using the STAR detector at RHIC. Systematic measurements of the dielectron yield as a…
We report the first observation of coherent rho0 production (AuAu->AuAu rho0) and rho0 production accompanied by mutual nuclear Coulomb excitation (AuAu->Au*Au*rho0),and the observation of coherent e+e- pair production (AuAu->Au*Au*e+e-) in…
We report on the measurement of the Central Exclusive Production of charged particle pairs $h^{+}h^{-}$ ($h = \pi, K, p$) with the STAR detector at RHIC in proton-proton collisions at $\sqrt{s} = 200$ GeV. The charged particle pairs…
The STAR collaboration reports the first observation of exclusive rho^0 photo-production, AuAu->AuAu rho^0, and rho^0 production accompanied by mutual nuclear Coulomb excitation, AuAu->Au*Au*rho^0, in ultra-peripheral heavy-ion collisions.…
The STAR collaboration at RHIC is measuring the production of electron-positron pairs at small impact parameters, larger than but already close to the range, where the ions interact strongly with each other. We calculate the total cross…
We present a summary of recent photoproduction results in ultra peripheral relativistic heavy ions collisions with STAR. These collisions have impact parameters larger then twice the nuclear radius; the nuclei do not physically collide, but…
Recently, significant enhancements of $e^{+} e^{-}$ pair production at very low transverse momentum ($p_{T} < 0.15$ GeV/c) were observed by the STAR collaboration in peripheral hadronic A+A collisions. This excesses can not be described by…
The $\Upsilon(1S+2S+3S)\to e^{+}e^{-}$ cross section is measured at mid-rapidity ($y$) in $p+p$ collisions and in d$+Au$ collisions at center-of-mass energy $\sqrt{s}$ = 200 GeV with the STAR detector at RHIC. In $p+p$, the measured cross…
We report first measurements of $e^{+}e^{-}$ pair production in the mass region 0.4 $<M_{ee}<$ 2.6 GeV/$c^{2}$ at low transverse momentum ($p_T<$ 0.15 GeV/$c$) in non-central Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U$+$U…
In 2010, the STAR Collaboration collected 38 million low-multiplicity triggers for ultra-peripheral collision studies. We present new results involving photonuclear interactions in ultra-peripheral relativistic heavy ion collisions (UPCs),…
We present the measurement of non-photonic electron production at high transverse momentum ($p_T > $ 2.5 GeV/$c$) in $p$ + $p$ collisions at $\sqrt{s}$ = 200 GeV using data recorded during 2005 and 2008 by the STAR experiment at the…