Neutral Pion Asymmetries at Intermediate Pseudorapidity in Transversely Polarized p + p Collisions at √ s = 200 GeV

Among the unanswered questions pertaining to nucleon spin physics is the origin of large azimuthal asymmetries (AN ) found in π forward pseudorapidity, η, from high-energy transversely polarized p + p collisions. One possible explanation is offered by twist-3 parton distribution and fragmentation functions. In order to test these and other mechanisms, it is important to study how the asymmetry changes over a range of pion kinematics. The STAR Endcap Electromagnetic Calorimeter (EEMC) is the only RHIC detector with the ability to study AN for π available at intermediate pseudorapidity, 0.8 ≤ η ≤ 2.0. STAR recently published the first measurement of AN for π using data collected in 2006 with collision energy √ STAR collected a high-statistics dataset with transverse beam polarization at √ s = 200 GeV. This offers over a five-fold increase in integrated luminosity relative to the 2006 dataset and a chance to enhance the precision of the previous results. The primary objective of this study is to determine the quality of the data from 2012 and to estimate the final statistical uncertainty.Preliminary results from this study indicate a significant improvement over the 2006 results

A First-Principle Study of Small Neutral and Anionic Silver Halide Clusters

Silver halide is a material that was traditionally used in photographic films. In recent years, there has been a revived interest in using small clusters of silver halides for photocatalytic and photovoltaic applications. We present the results of a theoretical study of neutral and anionic AgnXn (X = F, Cl, and Br, and n = 1-6) clusters. Quantum-mechanical calculations were performed using Density Functional Theory (DFT) in search of the lowest-energy isomers of the neutral and anionic clusters with applied symmetry constraints. The optimal configurations are compared across the series of AgF, AgCl, and AgBr. The variation in binding energies, bond lengths, charge distributions, HOMO-LUMO gaps, and electron affinities will be discussed as a function of cluster size and composition. The study of these clusters allows us to gain a better understanding of the structure and function of these materials in current and future applications

Calibrating the STAR Endcap Calorimiter for 2012 Data and Optimizing the Tower Gains for 2009 Data

The Solenoidal Tracker at RHIC (STAR), based at Brookhaven National Laboratory, uses polarized p+p collisions to investigate sea quark and gluon contributions to the proton spin. The STAR detector’s Endcap Electromagnetic Calorimeter (EEMC) is of particular interest in these experiments because it covers a kinematic region of the detector which is sensitive to gluons carrying a low fraction of the proton momentum, where the gluon spin is almost entirely unconstrained. The EEMC is located in the intermediate pseudorapidity range 1\u3ceta\u3c2, and measures the energy of particles produced in the collisions using a spatially segmented lead-scintillator sampling calorimeter. Each segment, or tower, is energy-calibrated using minimum ionizing particles. Scintillator light is converted to an electric pulse whose height is proportional to the energy deposited in the tower. A gain factor that converts the pulse height to energy deposited in GeV is determined separately for each tower. An independent energy calibration method was used to fine tune the tower gains and attempt to address other potential sources of systematic uncertainty, such as pseudorapidity-dependence in the reconstructed pi0 mass. Calibration of the detector for 2012 data using minimum ionizing particles has been started. Results from the 2009 and 2012 calibrations will be presented

An examination of STAR 2012 π0 data at 0.8 \u3c η \u3c 2.0 with longitudinally polarized p + p collisions at √s = 510 GeV

A recent global analysis of the proton spin has provided evidence for positive gluon polarization Δg(x) for the momentum fraction range of 0.05 \u3c x \u3c 1. The region x \u3c 0.05 remains relatively poorly constrained, and may provide a significant contribution to the spin of the proton. The STAR detector can be used to measure the effects of quark and gluon spins in the proton through the measurement of asymmetries in π0 production for different polarization states. The Relativistic Heavy Ion Collider at Brookhaven National Laboratory is uniquely able to collide polarized protons. Data from the p + p run in 2012 has significantly higher integrated luminosity and at a center of mass energy of 510 GeV, higher than previously analyzed datasets, thus allowing better access to Δg(x) at low x. The STAR endcap electromagnetic calorimeter, or EEMC, is able to detect π0\u27s in the range of pseudorapidity 0.8 \u3c η \u3c 2.0, a region at this energy where Δg(x) for low x can be examined. Preliminary work on 2012 data will be shown

Kitware/vtk-js: v13.11.1

13.11.1 (2020-03-18) Bug Fixes RenderWindowInteractor: Stop animating when RenderWindowInteractor is deleted (c120c7e