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Proceedings of RIKEN BNL Research Center Workshop: Multi-Hadron and Nonlocal Matrix Elements in Lattice QCD (Volume 120)
Nonperturbative QCD calculations of hadronic matrix elements are needed to understand the structure of the matter in our universe and to search for physics beyond the Standard Model. Numerical lattice gauge theory is uniquely suited for this task and has reached a remarkable level of precision. However, the types of observables that are accessible in a straightforward way are limited because lattice calculations are performed with imaginary time. Traditionally, lattice QCD determinations of hadronic matrix elements have been restricted to situations with at most one stable hadron in the initial and final states, and with a single insertion of a local current. This situation has been changing recently thanks to theoretical breakthroughs and pioneering numerical studies of new observables. At this workshop, the latest developments concerning multi-hadron systems and nonlocal matrix elements in lattice QCD were discussed: • Liischer's quantization condition relates the energy spectrum of two interacting particles in a finite volume to the scattering phase shifts. At this workshop, generalizations of Liischer's quantization condition to three-particle systems, and to two-particle systems with long-range QED interactions were presented. • Advanced numerical lattice QCD studies of hadronic resonances using the Liischer method were shown, including coupled-channel scattering and near-threshold resonances. • The Lellouch-Liischer formula relates two-hadron matrix elements computed in a finite volume to the infinite-volume matrix elements. This workshop included presentations of the latest numerical lattice QCD calculations ofthe nonleptonic weak decay K ® tl tl, as well as new theoretical results extending the Lellouch-Liischer formula to general multichannel 1 ® 2 transition matrix elements. • Novel methods allowing the direct calculation of parton distribution functions in lattice QCD were discussed, and a one-loop calculation of the lattice-to-continuum matching required for these methods was presented. • Lattice QCD calculations of nonlocal matrix elements relevant for rare kaon decays and for the Kl-Ks mass difference were shown. The inclusion of QED corrections in weak decays was discussed. Results from a new method for computing the hadronic light-by-light contribution to the muon anomalous magnetic moment were shown. • • Calculations of the binding energies and magnetic moments of light nuclei directly from lattice QCD were presented. The theoretical foundations of a potential-based method for studying multihadron interactions on the lattice were discussed, and an application of this method to charmed tetraquarks was shown.
Proceedings of RIKEN BNL Research Center Workshop: Theory and Modeling for the Beam Energy Scan: From Exploration to Discovery (Volume 121)
The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has concluded phase I of its Beam Energy Scan (BES) program. The goal of the RHIC BES program is to explore the phase diagram of strongly interacting matter at high baryonic densities and search for the QCD critical point by performing systematic scans at lower beam energies. Results from the RHIC BES I program are intriguing. There indeed seem to be several signals suggesting a softening of the equation of state, which may result from a first-order transition, as well as possible indications of a critical point. In light of these intriguing results, several accelerator and detector upgrades have been planned to conduct the phase II of the RHIC BES during the period 2017-2020. The goal of the RHIC BES II is discovery of the QCD critical point by performing high luminosity scans within the interesting beam energy range revealed through explorations at RHIC BES I. Past experience has proven that even qualitative understanding of the physics encoded within the RHIC experimental data requires substantial theoretical input based on QCD calculations as well as detailed, quantitative modeling of the medium created at the RHIC. However, the coordinated theoretical and modeling efforts necessary for comprehensive understanding of the RHIC BES data is presently lacking. The purpose of this workshop was to gather a small group of expert theorists, phenomenologists and experimentalists to identify the necessary theoretical and modeling developments required for RHIC BES, to delineate a clear path towards extracting concrete physics utilizing the RHIC BES data, and to kick-start collaborations among theorists, phenomenologists and experimentalists to ensure that the necessary theoretical and modeling developments can be achieved before the start of the RHIC BES II experimental program.
Proceedings of RIKEN BNL Research Center Workshop: Collectivity in Small Colliding Systems with High Multiplicity
The particle angular correlation measurements in small colliding systems, such as p+p, p+Pb, d+Au and 3 He+Au at RHIC and the LHC, have recently attracted significant interest. In particular, high-multiplicity events from such collisions exhibit a very similar pattern of longrapidity-range azimuthal correlations (the "ridge") as in Au+Au and Pb+Pb collisions. In AA collisions it is widely accepted that the ridge reflects various harmonic flow components arising from strong hydrodynamic response to fluctuating initial conditions. Hence, it is natural to ask whether the ridge observed in small colliding systems may also be interpreted as hydrodynamic flow plus fluctuating initial conditions. Although such a hydro-based interpretation can be made to work phenomenologically, it is unclear whether the hydrodynamic gradient expansion approach developed for A+A collisions is applicable in such small systems. Besides, there are alternative proposals in explaining the observation based on initial state effects (e.g. early gluon dynamics in a saturation picture). More recently, multi-particle cumulants measurements (as reported at QM14) have shown strong evidence for collectivity in high multiplicity p+Pb collisions, but the exact physical meaning of these measurements needs to be clarified. This Workshop specifically aimed to have focused discussions on these issues, and hopefully progress will be made in understanding them.
The Study of Advanced Accelerator Physics Research at UCLA Using the ATF at BNL: Vacuum Acceleration by Laser of Free Electrons
An experiment was designed and data were taken to demonstrate that a tightly focused laser on vacuum can accelerate an electron beam in free space. The experiment was proof-of-principle and showed a clear effect for the laser beam off and on. The size of the effect was about 20% and was consistent over 30 laser and beam shots.
Proceedings of RIKEN BNL Research Center Workshop: Jet Observables at the Electron-Ion Collider (Volume 136) [Slides]
As the realization of an Electron Ion Collider (EIC) moves forward, efforts from the nuclear physics community continue to grow. In addition to the ongoing detector R&D efforts, plans for novel analysis topics must be demonstrated to aid in the detector designs, so that we can maximize the physics output of the EIC. This relies on input from both the experimental and theory communities. The aim of this workshop is to gather experts as well as those with a developing interest in the EIC so that theorists and experimentalists with experience measuring jets in a variety of hadronic collision systems can discuss the possible advantages and challenges of making measurements of jets in e+p and for the first time ever jets in e+A collisions at the EIC. In the time since the EIC white paper was written in 2011, there has been a growing recognition that jet observables could be a powerful probe of many of the physics topics which will be addressed by the EIC. Recent years have seen a multitude of both theoretical and experimental papers exploring the utility of jets for topics as diverse as determining the hadronic structure of photons, studying the 3D structure of the nucleon, and characterizing the properties of the matter found in nuclei. The aim of this workshop is to provide a forum for both theorists and experimentalists to discuss the possible advantages and challenges of jet measurements in e+p and e+A collisions at the EIC, learn about the status of necessary simulation tools, consider requirements on detector performance, and propose new ideas for jet observables and measurements. This proceedings report is a compilation of slides from the presentations.
Heat transfer study on the beamline for an electron–ion collider at BNL
This study aims to calculate thermal loads that arise as a consequence of the beamline connecting the cold (2 K) region to the ambient. Heat loads are evaluated by numerical analysis and the findings are supported by analytical calculations. An active heat intercept is proposed to mitigate heat movement to the cold end. Owing to unfavorable length-to-depth ratio and large temperature differences, it is found that radiation becomes a dominant mode of heat transfer. The presence of bellows on the beamline complicates the thermal study which is heavily dependent on geometry. An analytical framework is set up to simplify the coupled conduction–radiation problem and is shown to decrease simulation times by an order of magnitude. The study finds that the total heat moving by conduction to the cold end is around 13 W and via radiation is 1.8 W. Furthermore, the active cooling circuit under present conditions has the ability to intercept between 8 - 12 W of heat.
Development of a technology for the fabrication of Low-Gain Avalanche Diodes at BNL
Low-Gain Avalanche Detectors are gathering interest in the High-Energy Physics community thanks to their fast-timing and radiation-hardness properties. One example of this includes plans to exploit timing detectors for the upgrades of the ATLAS and CMS detectors at the High Luminosity LHC. This new technology has also raised interest for its possible application for photon detection in medical physics, imaging and photon science. The main characteristic of this type of device is a thin and highly-doped layer that provides internal and moderate gain, in the order of 10–20, that enhances the signal amplitude. Furthermore the thin substrate, of only few tens of microns, allows for fast carrier collection. This paper offers here details on the fabrication technology, specifically developed at Brookhaven National Laboratory for the detection of minimum ionizing particles. The static electrical characterization and the gain measurements on prototypes will be also reported.
Commissioning results of the BNL Alternating Gradient Synchrotron booster AC dipole
Here, an AC dipole has been installed in the AGS booster as part of polarized beam developments for the future Electron Ion Collider (EIC). This will allow preserving helion beam polarization through two intrinsic resonances during acceleration to an energy corresponding to |$Gγ$| = 10.5. AC dipoles can preserve polarization by forcing the beam to undergo large amplitude vertical betatron oscillations. These coherent oscillations cause all particles to sample the strong horizontal fields of quadrupoles, and result in a full spin flip. In preparation for the AC dipole being used for polarized helions, it was first commissioned with polarized protons. The proton extraction energy was raised to allow protons to cross $Gγ$ = 0 + $v_y$ = 4.8087. As an artifact of the experiment using polarized protons, the booster settings for bunch extraction interfered with the coherent oscillations and limited the maximum coherent amplitude. This interference will be well separated in the case of polarized helions. Polarized protons crossed the $Gγ$ = 0 + $v_y$ intrinsic resonance with a full spin flip through use of the AC dipole. Simulations of the resonance crossing using Zgoubi accurately predict the polarization relative to the coherent amplitude.
The BNL Box Cloud Storage Service
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Nuclear Material Characterization Using High-Energy X-rays at BNL Synchrotrons: From Reactor Steels and Molten Salts to Large Hadron Collider Novel Materials
New and improved materials, composites, and super-alloys capable of withstanding the anticipated extreme states of fusion reactors, fission reactors (i.e., high-temperature fast reactors) and multi-MW particle accelerators, with the latter facing similarly extreme states to reactors under energetic protons, are continuously sought. Materials structures like improved reactor steels, super-alloys, and novel composites are continuously being explored to help meet both the challenge of the higher-demand environments and longevity under extreme conditions. Greater fluxes of irradiating species (primarily fast neutrons and energetic protons), extreme temperatures, and aggressively corrosive environments make up the new cocktail of operating conditions these materials must withstand. A challenge in characterizing the effects under intense irradiation, high temperatures, and stresses is the establishment of the link between lattice-induced damage and phase transformation under particle irradiation and macroscopic physical properties, which ultimately determine performance in the real environment. With ever increasing irradiation fluxes, dramatic changes in the material properties are expected to occur stemming from the evolution or development of new microstructures.
Double-sided detector for electron beam alignment and measurement of back-streaming electrons in ExtendedEBIS at BNL
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SynapSense Wireless Environmental Monitoring System of the RHIC and ATLAS Computing Facility at BNL
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Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide
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Halo removal experiments with hollow electron lens in the BNL Relativistic Heavy Ion Collider
A hollow electron beam has been proposed as an active control tool to remove the beam halo from high-energy, high-current hadron or ion machines (such as the High-Luminosity Large Hadron Collider). To study the halo removal rate and assess the effect on the ion beam core, one of the two electron lenses in the Relativistic Heavy Ion Collider was changed from a Gaussian beam profile to a hollow profile. We describe the design and verification of the hollow electron beam parameters as well as the methods to minimize the hollow beam profile distortions, which can result in an ion beam emittance increase. The hollow beam alignment with the ion beam by using a backscattered electron detector has been demonstrated. Furthermore, experiments were carried out to explore the efficiency of the halo removal by scanning the current and inner radius of the hollow electron beam, which is pulsed either every turn or every nth turn. The effects of the hollow electron beam on the ion beam emittance and luminosity were also assessed experimentally by scanning the inner radius of the electron beam.
Broadband high power rf window design for the BNL Electron Ion Collider
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Bulk properties of the system formed in Au + Au collisions at s N N = 14.5 GeV at the BNL STAR detector
We report systematic measurements of bulk properties of the system created in Au+Au collisions at √ S NN = 14.5 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The transverse momentum spectra of π ± , K ± and p(p¯) are studied at mid-rapidity (|y| < 0.1) for nine centrality intervals. The centrality, transverse momentum (p T ), and pseudorapidity (η) 3 dependence of inclusive charged particle elliptic flow (v 2 ), and rapidity-odd charged particles directed flow (v 1 ) results near mid-rapidity are also presented. These measurements are compared with the published results from Au+Au collisions at other energies, and from Pb+Pb collisions at √ S NN =2.76 TeV. The results at √ S NN = 14.5 GeV show similar behavior as established at other energies and fit well in the energy dependence trend. Furthermore, these results are important as the 14.5 GeV energy fills the gap in μ B, which is of the order of 100 MeV, between √ S NN =11.5 and 19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor agreement in general.