Latest Results from BNL and RHIC--2013

TL;DR

This paper summarizes recent experimental results from RHIC at BNL, highlighting advances in understanding quark-gluon plasma, particle production mechanisms, and detector upgrades, with implications for future high-energy nuclear physics research.

Contribution

It reports new measurements of particle suppression, flow, and constituent quark effects, and discusses detector upgrades like the sPHENIX project for future experiments.

Findings

Observation of fractional $p_T$ spectrum shifts indicating energy loss in quark-gluon plasma.

Detection of elliptic flow in d+Au collisions at RHIC.

Confirmation that constituent quarks are fundamental in particle production across systems.

Abstract

A selection of results from the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) from 2012 to 2013 is presented together with a few newsworthy developments in this period. The move of the g-2 magnet from BNL to Fermilab for the "fifth muon g-2 experiment" inspired a brief discussion of the original g-2 experiments at CERN. Highlights of the past year include a change in the measurement of the suppression of large transverse momentum ($p_T$) particles in the Quark Gluon Plasma to a measure of the fractional shift in the observed $p_T$ spectrum from the expected A+A spectrum for independent collisions as an estimate of the energy loss in the medium. The p+Pb run at LHC in early 2013 spurred new or improved measurements in d+Au at RHIC which included the observation of elliptical flow in d+Au collisions and measurements of transverse energy ($E_T$) spectra in p-p, d+Au and Au+Au collisions at 200 GeV nucleon-nucleon c.m. energy which demonstrated that constituent quarks are the fundamental element of particle production in all 3 systems. Measurements of identified hadrons in d+Au show a huge Cronin effect for protons but no effect for mesons. An important step for the future was the acquisition by BNL of the superconducting solenoid used in the BABAR experiment at SLAC for use in future experiments at RHIC and possibly eRHIC, starting with an upgrade of the PHENIX experiment called sPHENIX.