No Arabic abstract
Highlights of recent results from the STAR collaboration focusing on hard probes of the initial and final state are presented. New results at forward rapidities in d+Au collisions at low $x$ are utilized to study the possible onset of saturation effects at RHIC energies. New reference measurements, $Upsilon$ production, nuclear-$k_T$ via di-jets in d+Au collisions, and jet quantities in p+p collisions will be discussed. Final state nuclear modifications of $J/psi$ and identified hadrons in heavy-ion collisions will be presented. In addition to di(multi)-hadron and direct $gamma$-hadron correlations, new results from full-jet reconstruction in Au+Au collisions will be discussed with respect to the p+p reference measurements. These measurements can be used to put further constraints on the underlying mechanisms of partonic energy loss in heavy-ion collisions at RHIC.
We report selected results from STAR collaboration at RHIC, focusing on jet-hadron and jet-like correlations, quarkonium suppression and collectivity, di-electron spectrum in both p+p and Au+Au, and higher moments of net-protons as well as azimuthal anisotropy from RHIC Beam Energy Scan program.
The NA60 experiment is a fixed-target experiment at the CERN SPS. It has measured the dimuon yield in Indium--Indium collisions with an In beam of 158 AGeV/c and in p-A collisions with a proton beam of 400 and 158 AGeV/c. The results allow to address three important physics topics, namely the study of the rho spectral function in nuclear collisions, the clarification of the origin of the dimuon excess measured by NA50 in the intermediate mass range, and the J/psi suppression pattern in a collision system different from Pb-Pb. An overview of these results will be given in this paper.
Highlights of news from Brookhaven National Laboratory (BNL) and results from the Relativistic Heavy Ion Collider (RHIC) in the period July 2013-June 2014 are presented. It was a busy year for news, most notably a U. S. Government shutdown for 16 days beginning October 1, 2013 due to the lack of an approved budget for FY2014. Even with this unusual government activity, the $sqrt{s_{NN}}=200$ GeV Au+Au Run14 at RHIC was the best ever with integrated luminosity exceeding the sum of all previous runs. Additionally there was a brief He$^3$+Au run to continue the study of collective flow in small systems which was reinforced by new results presented on identified particle flow in d+Au. The other scientific highlights are also mostly concerned with ``soft (low $p_T$) physics complemented by the first preliminary results of reconstructed jets from hard-scattered partons in Au+Au collisions at RHIC . The measurements of transverse energy ($E_T$) spectra in p-p, d+Au and Au+Au collisions, which demonstrated last year that constituent quarks are the fundamental elements of particle production in all 3 systems, led to the conclusion that the two-component ansatz which has been used to represent $E_T$ distributions as a function of centrality is simply a proxy for the number of constituent quark participants as well as to an explanation of the surprising elliptical flow results from U+U collisions. An extensive discussion of the latest measurements in Au+Au of net-charge and net-proton distributions represented by Cumulants of the distributions and plans for a Beam Energy Scan at RHIC to look for a QCD critical point is presented and compared to the claim implied by a press release during the 2011 ISSP.
Highlights of news from Brookhaven National Laboratory (BNL) and results from the Relativistic Heavy Ion Collider (RHIC) in the period July 2014-June 2015 are presented. The news this year was mostly very positive. The major event at BNL was the startup and dedication of the new NSLS II, the Worlds brightest Synchrotron Light Source. The operation of RHIC was outstanding with a polarized p+p run at $sqrt{s}=200$ GeV with integrated luminosity that exceeded the sum of all previous p+p integrated luminosity at this $sqrt{s}$. For the first time at RHIC asymmetric p+Au and p+Al runs were made but the p+Al run caused damage in the PHENIX forward detectors from quenches that were inadequately shielded for this first p+A run. This was also the 10th anniversary of the 2005 announcement of the Perfect Liquid Quark Gluon Plasma at RHIC and a review is presented of the discoveries leading to this claim. A new result on net-charge fluctuations (with no particle identification) from PHENIX based on previous scans over beam energy to look for a QCD critical point is discussed which combined with Lattice QCD calculations and smaller errors on the higher cumulants than previous measurements led to calculations of the baryon chemical potential and freezeout temperature in agreement with the best accepted analysis from baryon/anti-baryon ratio measurements.
Highlights of news from Brookhaven National Laboratory (BNL) and results from the Relativistic Heavy Ion Collider (RHIC) in the period July 2015-2016 are presented. Transverse single spin asymmetries from polarized p+p collisions are presented for $pi^0$ and jets as a function of Feynman $x_F$. An energy scan to study the $sqrt{s}$ dependence of collectivity and flow for small systems was performed as well as a high luminosity Au$+$Au run. The failure of a quench protection diode resulted in a pause in the run to replace it, but otherwise performance of RHIC was the best ever. Experimental results discussed are an elegant measurement from STAR of the force between anti-protons using HBT correlations, flow in U+U collisions, an improved method of generating constituent quarks by PHENIX and new Number of Quark Participants (NQP) scaling of $E_T$ distributions in p$+$p,d$+$Au and Au$+$Au which worked well. New hard-scattering results as a function of $sqrt{s}$ in Au$+$Au central collisions are presented. Also, measurements of the di-hadron acoplanarity for $pi^0 +h$ and $gamma+h$ in p+p collisions at $sqrt{s}=500$ GeV are presented in terms of the out-of-plane transverse momentum $p_{rm out}$ which differ from the prediction of the TMD framework of parton transverse momentum dynamics.