In the initial years of operation, experiments at the Relativistic Heavy Ion Collider (RHIC) have identified a new form of matter formed in nucleus–nucleus collisions at energy densities more than ...100 times that of a cold atomic nucleus. Measurements and comparison with relativistic hydrodynamic models indicate that the matter thermalizes in an unexpectedly short time, has an energy density at least 15 times larger than needed for color deconfinement, has a temperature about twice the critical temperature predicted by lattice QCD, and appears to exhibit collective motion with ideal hydrodynamic properties–a “perfect liquid” that appears to flow with a near-zero viscosity to entropy ratio–lower than any previously observed fluid and perhaps close to a universal lower bound. However, a fundamental understanding of the medium seen in heavy-ion collisions at RHIC does not yet exist. The most important scientific challenge for the field in the next decade is the
quantitative exploration of the new state of nuclear matter. That will require new data that will, in turn, require enhanced capabilities of the RHIC detectors and accelerator. In this report we discuss the scientific opportunities for an upgraded RHIC facility–RHIC II–in conjunction with improved capabilities of the two large RHIC detectors, PHENIX and STAR. We focus solely on heavy flavor probes. Their production rates are calculable using the well-established techniques of perturbative QCD and their sizable interactions with the hot QCD medium provide unique and sensitive measurements of its crucial properties making them one of the key diagnostic tools available to us.
A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The ...early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the
B
-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau–Charm factories, JLab, the ILC, and beyond. The list of newly found conventional states expanded to include
h
c
(1
P
),
χ
c
2
(2
P
),
, and
η
b
(1
S
). In addition, the unexpected and still-fascinating
X
(3872) has been joined by more than a dozen other charmonium- and bottomonium-like “
XYZ
” states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark–gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of
,
, and
bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrial-strength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark–gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.
We have monitored a newly erupted volcanic island in the Kingdom of Tonga, unofficially known as Hunga Tonga Hunga Ha'apai, by means of relatively frequent high spatial resolution (~50 cm) satellite ...observations. The new ~1.8 km 2(exp) island formed as a tuff cone over the course of a month‐long hydromagmatic eruption in early 2015 in the Tonga‐Kermadec volcanic arc. Such ash‐dominated eruptions usually produce fragile subaerial landscapes that wash away rapidly due to marine erosion, as occurred nearby in 2009. Our measured rates of erosion are ~0.00256 km 3(exp) / year from derived digital topographic models. Preliminary measurements of the topographic expression of the primary tuff cone over ~30 months suggest a lifetime of ~19 years (and potentially up to 42 years). The ability to measure details of a young island's landscape evolution using satellite remote sensing has not previously been possible at these spatial and temporal resolutions.
Cold nuclear matter effects are those effects which modify the production of charmonia in a nuclear target in the absence of a Quark Gluon Plasma. Understanding them is an essential part of any ...attempt to interpret charmonium production in heavy-ion collisions. In 2008 the PHENIX experiment recorded data for J/ψ and ψ′ production in sNN=200 GeVd+Au collisions. The J/ψ data span the rapidity range from −2.2 to +2.35 and, taken together with p+A collision data on charmonium modification from lower collision energies, they shed light on the time scale dependence of cold nuclear matter effects on J/ψ production in p(d)+A collisions. The modification of ψ′ production is observed at mid rapidity, and is found to be much stronger than expected from existing models.
At high fluence rates in animal models, photodynamic therapy (PDT) can photochemically deplete ambient tumor oxygen through the generation of singlet oxygen, causing acute hypoxia and limiting ...treatment effectiveness. We report that standard clinical treatment conditions (1 mg/kg Photofrin, light at 630 nm and 150 mW/cm2), which are highly effective for treating human basal cell carcinomas, significantly diminished tumor oxygen levels during initial light delivery in a majority of carcinomas. Oxygen depletion could be found during at least 40% of the total light dose, but tumors appeared well oxygenated toward the end of treatment. In contrast, initial light delivery at a lower fluence rate of 30 mW/cm2 increased tumor oxygenation in a majority of carcinomas. Laser treatment caused an intensity- and treatment time-dependent increase in tumor temperature. The data suggest that high fluence rate treatment, although effective, may be inefficient.
The PHENIX experiment uses semileptonic and leptonic decay channels, respectively, to measure open and closed heavy flavor cross sections across the rapidity range −2.2<y<2.4. High luminosity data ...are now available for p + p, d + Au, Cu + Cu and Au + Au collisions at SNN=200GeV, and for Au + Au collisions at SNN=62GeV. We discuss recent d + Au results for open heavy flavor and J/ψ production, and discuss their implications for the cold nuclear matter contributions to heavy flavor production in heavy ion collisions.
PHENIX has studied
J
/
ψ
production in
s
N
N
=
200
GeV
collisions of
p
+
p
,
d+Au, Au+Au and Cu+Cu collisions. This systematic study was designed to allow the extraction of hot nuclear matter effects ...on
J
/
ψ
production in heavy ion collisions after accounting for the baseline production cross section using
p
+
p
data, and for cold nuclear matter effects using
d+Au data. Cold nuclear matter effects, for example gluon shadowing, are the effects associated with production of
J
/
ψ
from a nuclear target. The large yields obtained in the RHIC 2008 d+Au run provide, for the first time, an opportunity to characterize cold nuclear matter effects at RHIC, and try to isolate hot nuclear matter effects in Au+Au collisions. Low statistics preliminary measurements of excited charmonium yields and
ϒ
(
1
S
+
2
§
+
3
S
)
yields exist so far for
p
+
p
collisions, and there are preliminary results for ϒ production in
d+Au collisions.
Reported here are transverse single-spin asymmetries (AN) in the production of charged hadrons as a function of transverse momentum (pT) and Feynman-x (xF) in polarized p↑ + p, p↑ + Al, and p↑ + Au ...collisions at $\sqrt{^SNN}$ = 200 GeV. The measurements have been performed at forward and backward rapidity (1.4 < |η| < 2.4) over the range of 1.5 GeV /c < pT < 7.0 GeV /c and 0.04 < |xF| < 0.2. A nonzero asymmetry is observed for positively charged hadrons at forward rapidity (xF > 0) in p↑ + p collisions, whereas the p↑ + Al and p↑ + Au results show smaller asymmetries. This finding provides new opportunities to investigate the origin of transverse single-spin asymmetries and a tool to study nuclear effects in p + A collisions.
Polarized proton-proton collisions provide leading-order access to gluons, presenting an opportunity to constrain gluon spin-momentum correlations within transversely polarized protons and enhance ...our understanding of the three-dimensional structure of the proton. Midrapidity open-heavy-flavor production at $\sqrt{s}$ = 200 GeV is dominated by gluon-gluon fusion, providing heightened sensitivity to gluon dynamics relative to other production channels. Transverse single-spin asymmetries of positrons and electrons from heavy-flavor hadron decays are measured at midrapidity using the PHENIX detector at the Relativistic Heavy Ion Collider. These charge-separated measurements are sensitive to gluon correlators that can in principle be related to gluon orbital angular momentum via model calculations. Explicit constraints on gluon correlators are extracted for two separate models, one of which had not been constrained previously.
Presented are the first measurements of the transverse single-spin asymmetries ($A_N$) for neutral pions and eta mesons in $\textit{p}$ + Au and $\textit{p}$ + Al collisions at $\sqrt{s_{NN}}$ = 200 ...GeV in the pseudorapidity range |$\textit{η}$| < 0.35 with the PHENIX detector at the Relativistic Heavy Ion Collider. The asymmetries are consistent with zero, similar to those for midrapidity neutral pions and eta mesons produced in $\textit{p}$ + $\textit{p}$ collisions. These measurements show no evidence of additional effects that could potentially arise from the more complex partonic environment present in proton-nucleus collisions.
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