arXiv subjects

S. Edwards

Publications and source records attributed to S. Edwards.

60 records · Page 4Linked to original sources

arXiv2010

Cold Nuclear Matter Effects on J/psi Yields as a Function of Rapidity and Nuclear Geometry in Deuteron-Gold Collisions at sqrt(s_NN) = 200 GeV

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 calculations where the nuclear modification is linear or exponential in the density weighted longitudinal thickness are difficult to reconcile with the forward rapidity data.

nucl-ex↗

arXiv2010

Transverse momentum dependence of eta meson suppression in Au+Au collisions at sqrt(s_NN) = 200 GeV

New measurements by the PHENIX experiment at RHIC for eta production at midrapidity as a function of transverse momentum (p_T) and collision centrality in sqrt(s_NN) = 200 GeV Au+Au and p+p collisions are presented. They indicate nuclear modification factors (R_AA) that are similar both in magnitude and trend to those found in earlier pi^0 measurements. Linear fits to R_AA in the 5--20 GeV/c p_T region show that the slope is consistent with zero within two standard deviations at all centralities although a slow rise cannot be excluded. Having different statistical and systematic uncertainties the pi^0 and eta measurements are complementary at high p_T; thus, along with the extended p_T range of these data they can provide additional constraints for theoretical modeling and the extraction of transport properties.

nucl-ex↗

arXiv2010

Elliptic and hexadecapole flow of charged hadrons in Au+Au collisions at sqrt(s_NN) = 200 GeV

Differential measurements of the elliptic (v_2) and hexadecapole (v_4) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum (p_T) and collision centrality or the number of participant nucleons (N_part) for Au+Au collisions at sqrt(s_NN)=200 GeV. The v_{2,4} measurements at pseudorapidity |η|<=0.35 obtained with four separate reaction plane detectors positioned in the range 1.0<|η|<3.9 show good agreement, indicating the absence of significant η-dependent nonflow perturbations. Sizable values for v_4(p_T) are observed with a ratio v_4(p_T,N_part)/v_2^2(p_T,N_part)~0.8 for 50 200 this ratio increases up to 1.7 in the most central collisions.

nucl-ex↗

arXiv2010

Trends in Yield and Azimuthal Shape Modification in Dihadron Correlations in Relativistic Heavy Ion Collisions

Fast parton probes produced by hard scattering and embedded within collisions of large nuclei have shown that partons suffer large energy loss and that the produced medium may respond collectively to the lost energy. We present measurements of neutral pion trigger particles at transverse momenta p^t_T = 4-12 GeV/c and associated charged hadrons (p^a_T = 0.5-7 GeV/c) as a function of relative azimuthal angle Delta Phi at midrapidity in Au+Au and p+p collisions at sqrt(s_NN) = 200 GeV. These data lead to two major observations. First, the relative angular distribution of low momentum hadrons, whose shape modification has been interpreted as a medium response to parton energy loss, is found to be modified only for p^t_T < 7 GeV/c. At higher p^t_T, the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured p^a_T. This observation presents a quantitative challenge to medium response scenarios. Second, the associated yield of hadrons opposite to the trigger particle in Au+Au relative to that in p+p (I_AA) is found to be suppressed at large momentum (IAA ~ 0.35-0.5), but less than the single particle nuclear modification factor (R_AA ~0.2).

nucl-ex↗

arXiv2009

't Hooft-Polyakov monopoles in lattice SU(N)+adjoint Higgs theory

We investigate twisted C-periodic boundary conditions in SU(N) gauge field theory with an adjoint Higgs field. We show that with a suitable twist for even N one can impose a non-zero magnetic charge relative to residual U(1) gauge groups in the broken phase, thereby creating a 't Hooft-Polyakov magnetic monopole. This makes it possible to use lattice Monte-Carlo simulations to study the properties of these monopoles in the quantum theory.

hep-lat↗

arXiv2003

He I 10830 as a Probe of Winds in Accreting Young Stars

He I 10830 profiles acquired with Keck's NIRSPEC for 6 young low mass stars with high disk accretion rates (AS 353A, DG Tau, DL Tau, DR Tau, HL Tau and SVS 13) provide new insight into accretion-driven winds. In 4 stars the profiles have the signature of resonance scattering, and possess a deep and broad blueshifted absorption that penetrates more than 50% into the 1 micron continuum over a continuous range of velocities from near the stellar rest velocity to the terminal velocity of the wind, unlike inner wind signatures seen in other spectral features. This deep and broad absorption provides the first observational tracer of the acceleration region of the inner wind and suggests that this acceleration region is situated such that it occults a significant portion of the stellar disk. The remaining 2 stars also have blue absorption extending below the continuum although here the profiles are dominated by emission, requiring an additional source of helium excitation beyond resonant scattering. This is likely the same process that produces the emission profiles seen at He I 5876.

astro-ph↗