We study the expected performance of the proposed fundamental neutron physics beamline at the upgraded High Flux Isotope Reactor at Oak Ridge National Laboratory. A curved neutron guide transmits the ...neutrons from the new cold source into a guide hall. A novel feature of the proposed guide is the use of vertical focussing to increase the flux for experiments that require relatively small cross-section beams. We use the simulation code IB to model straight, multi-channel curved, and tapered guides of various m values. Guide performance for the current NPDGamma and proposed abBA experiments is evaluated.
Published measurements of semi-inclusive Λ production in p–Au collisions at the AGS are used to estimate the yields of singly strange hadrons in nucleus–nucleus (A–A) collisions. Results of a ...described extrapolation technique are shown and compared to measurements of K+ production in Si–Al, Si–Au, and Au–Au collisions at the AGS and net Λ production in S–S, S–Ag, Pb–Pb, and inclusive p–A collisions at the SPS. The extrapolations can account for more than 75% of the measured strange particle yields in all of the studied systems except for very central Au+Au collisions at the AGS where RQMD comparisons suggest large re-scattering contributions.
The Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory with an anticipated start-up in early 2006, will provide the most intense pulsed beams of cold ...neutrons in the world. At a projected power of 1.4 MW, the time averaged fluxes and fluences of the SNS will approach those of high flux reactors. One of the flight paths on the cold, coupled moderator will be devoted to fundamental neutron physics. The fundamental neutron physics beamline is anticipated to include two beam-lines; a broad band cold beam, and a monochromatic beam of 0.89 nm neutrons for ultracold neutron (UCN) experiments. The fundamental neutron physics beamline will be operated as a user facility with experiment selection based on a peer reviewed proposal process. An initial program of five experiments in neutron decay, hadronic weak interaction and time reversal symmetry violation have been proposed.
Fundamental neutron physics, combining precision measurements and theory, probes particle physics at short range with reach well beyond the highest energies probed by the LHC. Significant US efforts ...are underway that will probe BSM CP violation with orders of magnitude more sensitivity, provide new data on the Cabibbo anomaly, more precisely measure the neutron lifetime and decay, and explore hadronic parity violation. World-leading results from the US Fundamental Neutron Physics community since the last Long Range Plan, include the world's most precise measurement of the neutron lifetime from UCN\(\tau\), the final results on the beta-asymmetry from UCNA and new results on hadronic parity violation from the NPDGamma and n-\({^3}\)He runs at the FNPB (Fundamental Neutron Physics Beamline), precision measurement of the radiative neutron decay mode and n-\({}^4\)He at NIST. US leadership and discovery potential are ensured by the development of new high-impact experiments including BL3, Nab, LANL nEDM and nEDM@SNS. On the theory side, the last few years have seen results for the neutron EDM from the QCD \(\theta\) term, a factor of two reduction in the uncertainty for inner radiative corrections in beta-decay which impacts CKM unitarity, and progress on {\it ab initio} calculations of nuclear structure for medium-mass and heavy nuclei which can eventually improve the connection between nuclear and nucleon EDMs. In order to maintain this exciting program and capitalize on past investments while also pursuing new ideas and building US leadership in new areas, the Fundamental Neutron Physics community has identified a number of priorities and opportunities for our sub-field covering the time-frame of the last Long Range Plan (LRP) under development. This white paper elaborates on these priorities.
Correlations between p and pbar's at transverse momenta typical of enhanced baryon production in Au+Au collisions are reported. The PHENIX experiment measures same and opposite sign baryon pairs in ...Au+Au collisions at sqrt(s_NN) = 200 GeV. Correlated production of p and p^bar with the trigger particle from the range 2.5 < p_T < 4.0 GeV/c and the associated particle with 1.8 < p_T < 2.5 GeV/c is observed to be nearly independent of the centrality of the collisions. Same sign pairs show no correlation at any centrality. The conditional yield of mesons triggered by baryons (and anti-baryons) and mesons in the same pT range rises with increasing centrality, except for the most central collisions, where baryons show a significantly smaller number of associated mesons. These data are consistent with a picture in which hard scattered partons produce correlated p and p^bar in the p_T region of the baryon excess.
Results from the PHENIX experiment of measurements of high-\(p_{\rm T}\) particle production presented at the Hard Probes 2004 Conference are summarized. This paper focuses on a sub-set of the ...measurements presented at the conference, namely the suppression of \(\pi^0\) production at moderate to high \(p_{\rm T}\) as a function of angle with respect to the collision reaction plane, \(\Delta\phi\), for different collision centralities. The data are presented in the form of nuclear modification factor as a function of angle with respect to the reaction plane, \(R_{AA} (\Delta \phi)\). The data are analyzed using empirical estimates of the medium-induced energy loss obtained from the \(R_{AA} (\Delta \phi)\) values. A geometric analysis is performed with the goal of understanding the simultaneous dependence of RAA on \(\Delta\phi\) and centrality. We find that the centrality and \(\Delta\phi\) dependence of the \(\pi^0\) suppression can be made approximately consistent using an admittedly over-simplistic description of the geometry of the jet propagation in the medium but only if the energy loss is effectively reduced for short parton path lengths in the medium. We find that with a more "canonical" treatment of the quenching geometry, the \(\pi^0\) suppression varies more rapidly with \(\Delta\phi\) than would be expected from the centrality dependence of the suppression.
PHENIX on-line systems Alley, G; Amirikas, R; Arai, Y ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2003, Letnik:
499, Številka:
2
Journal Article
Recenzirano
The PHENIX On-Line system takes signals from the Front End Modules (FEM) on each detector subsystem for the purpose of generating events for physics analysis. Processing of event data begins when the ...Data Collection Modules (DCM) receive data via fiber-optic links from the FEMs. The DCMs format and zero suppress the data and generate data packets. These packets go to the Event Builders (EvB) that assemble the events in final form. The Level-1 trigger (LVL1) generates a decision for each beam crossing and eliminates uninteresting events. The FEMs carry out all detector processing of the data so that it is delivered to the DCMs using a standard format. The FEMs also provide buffering for LVL1 trigger processing and DCM data collection. This is carried out using an architecture that is pipelined and deadtimeless. All of this is controlled by the Master Timing System (MTS) that distributes the RHIC clocks. A Level-2 trigger (LVL2) gives additional discrimination. A description of the components and operation of the PHENIX On-Line system is given and the solution to a number of electronic infrastructure problems are discussed.
We are developing a high-efficiency neutron detector with 1 cm position resolution and coarse energy resolution for use at high-flux neutron source facilities currently proposed or under ...construction. The detector concept integrates a segmented (3)He ionization chamber with the position sensitive, charged particle collection methods of a MicroMegas detector. Neutron absorption on the helium produces protons and tritons that ionize the fill gas. The charge is amplified in the field region around a wire mesh and subsequently detected in current mode by wire strips mounted on a substrate. One module consisting of a high-voltage plate, a field-shaping high-voltage plate, a grid and wire strips defines a detection region. For 100 % efficiency, detector modules are consecutively placed along the beam axis. Analysis over several regions with alternating wire strip orientation provides a two-dimensional beam profile. By using (3)He, a 1/v absorption gas, each axial region captures neutrons of a different energy range, providing an energy-sensitive detection scheme especially useful at continuous beam sources.
PDF
