J. M. Landgraf

An overview of the STAR DAQ system

Abstract We describe the STAR Data Acquisition System. STAR is one of four experiments commissioned at the Relativistic Heavy Ion Collider (RHIC) at BNL in 1999 and 2000. DAQ combines custom VME-based receiver electronics with off-the-shelf computers in a parallel architecture interconnected with a Myrinet network. Events of size 80 MB are processed at input rates up to 100 Hz . Events are reduced to 10 MB by zero suppression performed in hardware using custom-designed ASICs. A Level 3 Trigger reconstructs tracks in real time and provides a physics-based filter to further reduce the sustained output data rate to ∼30 MB / s . Built events are sent via Gigabit Ethernet to the RHIC Computing Facility and stored to tape using HPSS.

The STAR level-3 trigger system

Abstract The STAR Level-3 trigger issues a trigger decision upon a complete online reconstruction of Au+Au collisions at relativistic heavy ion collider energies. Central interactions are processed up to a rate of 50 s −1 including a simple analysis of physics observables. The setup of the processor farm and the event reconstruction as well as experiences and the proposed trigger algorithms are described.

The proposed level-3 trigger system for STAR

The level-3 trigger system of the STAR experiment will in the final stage consist of a farm of 24 ALPHA/Linux processors, interconnected by SCI (Scalable Coherent Interface). The system will perform online tracking of N/sub track//spl ges/8000 tracks per event (N/sub point//spl les/45 per track). The track data will be transferred to a global level-3 CPU (expected data transfer rate /spl sime/48 MB/s), performing online event analysis tasks (e.g. invariant mass reconstruction) with a design trigger input rate of R=100 Hz (R=20 Hz for a prototype system).

First measurement of A N at s = 200 GeV in polarized proton–proton elastic scattering at RHIC

We report on the first measurement of the single spin analyzing power (A_N) at sqrt(s)=200GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). Data points were measured in the four momentum transfer t range 0.01 < |t| < 0.03 (GeV/c)^2. Our result, averaged over the whole t-interval is about one standard deviation above the calculation, which uses interference between electromagnetic spin-flip amplitude and hadronic non-flip amplitude, the source of A_N. The difference could be explained by an additional contribution of a hadronic spin-flip amplitude to A_N.

The implementation of the STAR data-acquisition system using a Myrinet Network

We present results from the first year of operation of the STAR data-acquisition (DAQ) system using a Myrinet Network. STAR is one of four experiments to have been commissioned at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory during 1999 and 2000. The DAQ system is fully integrated with a Level 3 Trigger. The combined system currently consists of 33 Myrinet Nodes, which run in a mixed environment of MVME processors running VxWorksj DEC Alpha workstations running Linux, and SUN Solaris machines. The network will eventually contain up to 150 nodes for the expected final size of the L3 processor farm. Myrinet is a switched high-speed low-latency network produced by Myricom and available for PCI and PMC on a wide variety of platforms. The STAR DAQ system uses the Myrinet Network for messaging, L3 processing, and event building. After the events are built, they are sent via gigabit ethernet to the RHIC computing facility and stored to tape using HPSS. The combined DAQ/L3 system processes 160-MB events at 100 Hz, compresses each event to 20 MB, and performs tracking on the events to implement a physics-based filter to reduce the data storage rate to 20 MB/s.

The First Measurement of the Elastic pp‐scattering Spin Parameters at s = 200 GeV

Elastic scattering of polarized protons in the range of very small momentum transferred was studied for the first time at s = 200 GeV in the experiment pp2pp at RHIC. This article presents the single spin asymmetry AN and the double spin asymmetries ANN and ASS measured in this experiment.

First measurement of AN at in polarized proton–proton elastic scattering at RHIC

We report on the first measurement of the single spin analyzing power (A_N) at sqrt(s)=200GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). Data points were measured in the four momentum transfer t range 0.01 < |t| < 0.03 (GeV/c)^2. Our result, averaged over the whole t-interval is about one standard deviation above the calculation, which uses interference between electromagnetic spin-flip amplitude and hadronic non-flip amplitude, the source of A_N. The difference could be explained by an additional contribution of a hadronic spin-flip amplitude to A_N.

First measurement of AN at s=200GeV in polarized proton–proton elastic scattering at RHIC

We report on the first measurement of the single spin analyzing power (A_N) at sqrt(s)=200GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). Data points were measured in the four momentum transfer t range 0.01 < |t| < 0.03 (GeV/c)^2. Our result, averaged over the whole t-interval is about one standard deviation above the calculation, which uses interference between electromagnetic spin-flip amplitude and hadronic non-flip amplitude, the source of A_N. The difference could be explained by an additional contribution of a hadronic spin-flip amplitude to A_N.