Past, present, and future roles of long-term experiments in the LTER Network

Author Posting. © American Institute of Biological Sciences, 2012. This article is posted here by permission of American Institute of Biological Sciences for personal use, not for redistribution. The definitive version was published in BioScience 62 (2012): 377-389, doi:10.1525/bio.2012.62.4.9.The US National Science Foundation—funded Long Term Ecological Research (LTER) Network supports a large (around 240) and diverse portfolio of long-term ecological experiments. Collectively, these long-term experiments have (a) provided unique insights into ecological patterns and processes, although such insight often became apparent only after many years of study; (b) influenced management and policy decisions; and (c) evolved into research platforms supporting studies and involving investigators who were not part of the original design. Furthermore, this suite of long-term experiments addresses, at the site level, all of the US National Research Council's Grand Challenges in Environmental Sciences. Despite these contributions, we argue that the scale and scope of global environmental change requires a more-coordinated multisite approach to long-term experiments. Ideally, such an approach would include a network of spatially extensive multifactor experiments, designed in collaboration with ecological modelers that would build on and extend the unique context provided by the LTER Network.2012-10-0

Controlled Radical Polymerization of Vinyl Acetate Mediated by a Bis(imino)pyridine Vanadium Complex

Source type: Prin

Inclusive cross section and double-helicity asymmetry for pi(0) production at midrapidity in p plus p collisions at root s=510 GeV

PHENIX measurements are presented for the cross section and double-helicity asymmetry (A(LL)) in inclusive pi(0) production at midrapidity from p + p collisions at root s = 510 GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum-chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The pi(0)A(LL) results follow an increasingly positive asymmetry trend with p(T) and root s with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on pi(0) and jet A(LL) and suggested a positive contribution of gluon polarization to the spin of the proton Delta G for the gluon momentum fraction range x \u3e 0.05. The data presented here extend to a currently unexplored region, down to x similar to 0.01, and thus provide additional constraints on the value of Delta G

Forward J/psi production in U plus U collisions at root S-NN=193 GeV

The invariant yields, dN/dy, for J/psi production at forward rapidity (1.2 \u3c vertical bar y vertical bar \u3c 2.2) in U + U collisions at root S-NN = 193 GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor R-AA are presented and compared with those from Au + Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U + U and Au + Au collisions within the same centrality class is presented, and used to investigate the role of c (c) over bar coalescence. Two different parametrizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, N-coll, and these were found to give significantly different Ncoll values. Results using N-coll values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the J/psi suppression, relative to binary collision scaling, is similar in U + U and Au + Au for peripheral and midcentral collisions, but that J/psi show less suppression for the most central U + U collisions. The results are consistent with a picture in which, for central collisions, increase in the J/psi yield due to c (c) over bar coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between c (c) over bar coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine N-coll

Measurements of directed, elliptic, and triangular flow in Cu plus Au collisions at root sNN=200 GeV

Measurements of anisotropic flow Fourier coefficients (upsilon(n)) for inclusive charged particles and identified hadrons pi(+/-), K-+/-, p, and (p) over bar produced at midrapidity in Cu + Au collisions at root s(NN) = 200 GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes psi(n), for n = 1, 2, and 3 are studied as a function of transverse momentum p(T) over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. We also compare these Cu + Au results with those in Cu + Cu and Au + Au collisions at the same root s(NN) and find that the upsilon(2) and upsilon(3), as a function of transverse momentum, follow a common scaling with 1/(epsilon N-n(part)1/3)

Measurements of B -\u3e J/psi at forward rapidity in p plus p collisions at root s=510 GeV

We report the first measurement of the fraction of J/psi mesons coming from B-meson decay (F (B -\u3e J/psi)) in p + p collisions at root s = 510 GeV. The measurement is performed using the forward silicon vertex detector and central vertex detector at PHENIX, which provide precise tracking and distance-of-closest-approach determinations, enabling the statistical separation of J=. due to B-meson decays from prompt J/psi. The measured value of F (B -\u3e J/psi) is 8.1% +/- 2.3% (stat) +/- 1.9% (syst) for J/psi with transverse momenta 0 \u3c p(T) \u3c 5 GeV/c and rapidity 1.2 \u3c vertical bar y vertical bar \u3c 2.2. The measured fraction F (B -\u3e J/psi) at PHENIX is compared to values measured by other experiments at higher center of mass energies and to fixed-order-next-toleading- logarithm and color-evaporation-model predictions. The b (b) over bar cross section per unit rapidity [d sigma/dy(pp -\u3e b (b) over bar)] extracted from the obtained F (B -\u3e J/psi) and the PHENIX inclusive J/psi cross section measured at 200 GeV scaled with color-evaporation-model calculations, at the mean B hadron rapidity y = +/- 1.7 in 510 GeV p + p collisions, is 3.63(-1.70)(+1.92) mu b. It is consistent with the fixed-order-next-to leading- logarithm calculations

Nonperturbative-transverse-momentum effects and evolution in dihadron and direct photon-hadron angular correlations in p plus p collisions at root s=510 GeV

Dihadron and isolated direct photon-hadron angular correlations are measured in p + p collisions at root s = 510 GeV. Correlations of charged hadrons of 0.7 \u3c p(T) \u3c 10 GeV/c with pi(0) mesons of 4 \u3c p(T) \u3c 15 GeV/c or isolated direct photons of 7 \u3c p(T) \u3c 15 GeV/c are used to study nonperturbative effects generated by initial-state partonic transverse momentum and final-state transverse momentum from fragmentation. The nonperturbative behavior is characterized by measuring the out-of-plane transverse momentum component p(out) perpendicular to the axis of the trigger particle, which is the high-p(T) direct photon or pi(0). Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (p(T)(trig)). The Gaussian widths and root mean square of p(out) are reported as a function of the interaction hard scale p(T)(trig) to investigate possible transverse-momentum-dependent evolution differences between the pi(0)-h(+/-) and direct photon-h(+/-) correlations and factorization breaking effects. The widths are found to decrease with p(T)(trig) , which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in p + p collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements

Cross section and transverse single-spin asymmetry of muons from open heavy-flavor decays in polarized p plus p collisions at root s=200 GeV

The cross section and transverse single-spin asymmetries of mu(-) and mu(+) from open heavy-flavor decays in polarized p + p collisions at root s = 200 GeV were measured by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at root s = 200 GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity (1.4 \u3c vertical bar y vertical bar \u3c 2.0) over the transverse momentum range of 1.25 \u3c p(T) \u3c 7 GeV/c for the cross section and 1.25 \u3c p(T) \u3c 5 GeV/c for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data

Cross section and longitudinal single-spin asymmetry AL for forward W± → μ±ν production in polarized p+p collisions at √s=510 GeV

We have measured the cross section and single-spin asymmetries from forward W±→μ±ν production in longitudinally polarized p+p collisions at √s=510  GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the W bosons provides a natural flavor separation of the participating partons