118390499
Beam–beam simulation code BBSIM for particle accelerators
A highly efficient, fully parallelized, six-dimensional tracking model for simulating interactions of colliding hadron beams in high energy ring colliders and simulating schemes for mitigating their effects is described. The model uses the weak-strong approximation for calculating the head-on interactions when the test beam has lower intensity than the other beam, a look-up table for the efficient calculation of long-range beam-beam forces, and a self-consistent Poisson solver when both beams have comparable intensities. A performance test of the model in a parallel environment is presented. The code is used to calculate beam emittance and beam loss in the Tevatron at Fermilab and compared with measurements. They also present results from the studies of stwo schemes proposed to compensate the beam-beam interactions: (a) the compensation of long-range interactions in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven and the Large Hadron Collider (LHC) at CERN with a current carrying wire, (b) the use of a low energy electron beam to compensate the head-on interactions in RHIC.
118724306
Simulations of beam-beam and beam-wire interactions in RHIC
The beam-beam interaction is one of the dominant sources of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and strong localized long-range beam-beam effects are experimentally investigated in the RHIC collider. Tune shift, beam transfer function, and beam loss rate are measured in dedicated experiments. In this paper, they report on simulations to study the effect of beam-wire interactions based on diffusive apertures, beam loss rates, and beam transfer function using a parallelized weak-strong beam simulation code (BBSIMC). The simulation results are compared with measurements performed in RHIC during 2007 and 2008.
15169434
Optimizing Large Data Transfers over 100Gbps Wide Area Networks
The Advanced Networking Initiative (ANI) project from the Energy Services Network provides a 100 Gbps test bed, which offers the opportunity for evaluating applications and middleware used by scientific experiments. This test bed is a prototype of a 100 Gbps wide-area network backbone, which links several Department of Energy (DOE) national laboratories, universities and other research institutions. These scientific experiments involve movement of large datasets for collaborations among researchers at different sites and thus require advanced infrastructure for supporting large and fast data transfers. A 100 Gbps network test bed is a key component of the ANI project and is used for DOE's science research programs. This work presents results towards obtaining maximum throughput in large data transfers by optimizing and fine-tuning scientific applications and middleware to use this advanced infrastructure efficiently. A detailed performance evaluation is discussed measuring both applications, from High Energy Physics (HEP) and from data transfer middleware (GridFTP, Globus Online, Storage Resource Management, XrootD and Squid) at 100 Gbps speeds and 53 ms of latency. Results show that up to 97% efficiency of such high bandwidth high latency network is possible, achieving 80-90 Gbps in most test cases with a peak transfer rate of 100 Gbps.
118648616
Heavy Flavor Physics Through e-Science
Heavy flavor physics is an important element in understanding the nature of particle physics. Accurate knowledge of the properties of heavy flavor physics plays an essential role for the determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. An asymmetric-energy e + e B factory KEKB and its experiment Belle is under way. It will be upgraded to Super Belle in a few years, and the size of the B meson sample will be dramatically increased. Also, the data size of Tevatron experiments (CDF, D0) are on the order of Peta Byte (PB). Therefore, we need to use a new concept of e-Science in this area. This concept implies studying a huge size of data from heavy flavor physics anytime and anywhere even if we are not on-site in accelerator laboratories. The components of this concept include data production, data processing, and data analysis. We apply this concept to the current CDF experiment at Tevatron. We will expand this concept to Super Belle and large hadron collider (LHC) experiments, which will achieve an accuracy of measurements in the next decades.
44296603
Radiatively generated maximal mixing scenario for the Higgs boson mass and the least fine-tuned minimal supersymmetric standard model.
We argue that given the experimental constraints on the Higgs boson mass the least fine-tuned parameter space of the minimal supersymmetric standard model is with negative top-squark masses squared at the grand unification scale. While the top-squark mass squared is typically driven to positive values at the weak scale, the contribution to the Higgs boson mass squared parameter from the running can be arbitrarily small, which reduces the fine-tuning of electroweak symmetry breaking. At the same time the top-squark mixing is necessarily enhanced and the maximal mixing scenario for the Higgs boson mass can be generated radiatively even when starting with negligible mixing at the unification scale. This highly alleviates constraints on possible models for supersymmetry breaking in which fine-tuning is absent.
121615298
Measurement of the refractive index of the LAB-based liquid scintillator and acrylic at RENO
In this paper, we describe the first measurement of the refractive index of the linear alkyl benzene (LAB)-based liquid scintillator and acrylic used at the Reactor Experiment for Neutrino Oscillation (RENO). The refractive index of a material is an important optical property and the prism spectrometer is the most common device for measuring the refractive index. Using the minimum deviation technique, which requires an exact measurement of the apex angle, we determined the refractive indices at six different wavelengths and then fitted them. We also compared the refractive index of the LAB-based liquid scintillator with the refractive indices of other liquid scintillator solvents commonly used in reactor neutrino experiments.
365928
Mediation of supersymmetry breaking in gauge messenger models
We study gauge mediation of supersymmetry breaking in SU(5) supersymmetric grand unified theory with gauge fields as messengers. The generated soft supersymmetry breaking parameters lead to close to maximal mixing scenario for the Higgs mass and highly reduce the fine tuning of electroweak symmetry breaking. All gaugino, squark and slepton masses are determined by one parameter – the supersymmetry breaking scale. The characteristic features are: negative and non-universal squark and slepton masses squared at the unification scale, non-universal gaugino masses, and sizable soft-trilinear couplings. In this scenario, all soft supersymmetry breaking parameters at the unification scale can be smaller than 400 GeV and all the superpartners can be lighter than 400 GeV and still satisfy all the limits from direct searches for superpartners and also the limit on the Higgs mass. The lightest supersymmetric particle is gravitino or a sizable mixture of bino, wino and higgsino. We also consider a possible contributions from additional messengers in vector-like representations, and a contribution from gravity mediation, which is estimated to be comparable.