44117065
NMSSM in disguise: Discovering singlino dark matter with soft leptons at the LHC
Abstract We suggest an NMSSM scenario, motivated by dark matter constraints, that may disguise itself as a much simpler mSUGRA scenario at the LHC. We show how its non-minimal nature can be revealed, and the bino–singlino mass difference measured, by looking for soft leptons.
118552878
Natural gauge mediation with a bino NLSP at the LHC
Natural models of supersymmetry with a gravitino LSP provide distinctive signatures at the LHC. For a neutralino NLSP, sparticles can decay to two high energy photons plus missing energy. We use the ATLAS diphoton search with 4.8 fb of data to place limits in both the stop-gluino and neutralino-chargino mass planes for this scenario. If the neutralino is heavier than 50 GeV, the lightest stop must be heavier than 580 GeV, the gluino heavier than 1100 GeV and charginos must be heavier than approximately 300-470 GeV. This provides the first nontrivial constraints in natural gauge mediation models with a neutralino NLSP decaying to photons, and implies a fine tuning of at least a few percent in such models.
119232009
Plate fin heat exchanger model with axial conduction and variable properites
Future superconduction radio frequency (SRF) cavities, as part of Project X at Fermilab,will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchanger are an effective option. However, at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numberical model that includes the effects of axial guide design decisions on heat exhanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters.
121688128
Proposed uv-FEL user facility at BNL
Abstract The NSLS at Brookhaven National Laboratory is proposing the construction of a UV-FEL operating in the wavelength range from visible to 750 A. Nanocoulomb electron pulses will be generated at a laser photocathode rf gun at a repetition rate of 10 kHz. The 6 ps pulses will be accelerated to 250 MeV in a superconducting linac. The FEL output will serve four stations with independent wavelength tuning, using two wigglers and two rotating mirror beam switches. Seed radiation for the FEL amplifiers will be provided by conventional tunable lasers, and the final frequency multiplication from the visible or near UV to the VUV will be carried out in the FEL itself. Each FEL will be comprised of an initial wiggler resonant to the seed wavelength, a dispersion section, and a second wiggler resonant to the output wavelength. The facility will provide pump-probe capability, FEL on FEL, and FEL on synchrotron light from an insertion device on the NSLS X-ray ring.
118661436
The Princeton-Pennsylvania 3 GeV Proton Accelerator as a Nuclear Tool
I would like to describe the Princeton-Pennsylvania Accelerator as a tool for nuclear research. Some people tend to think of the PPA as being too high in energy for nuclear research and, therefore, regard it as only an elementary particle research tool. While much of our work has, in fact, been related to the study of mesons, especially K-mesons, and to the study of the invariance principles, such as C, P, T, about 15% of the research has been either purely nuclear, or with strong nuclear overtones. As examples of the purely nuclear, I mention spallation reactions at 3 BeV and the study of the resulting neutron deficient nuclei. On the other side of the valley are the baryon stable, neutron rich, light fragments, 19N and 21O, which have been discovered in confirmation of Garvey’s mass formula. Negative pion scattering by twelve different complex nuclei from Be to Au over the energy range 600-1600 MeV has been used to determine optical model potentials. Neutron total cross sections over the momentum range 500-2800 MeV/c are now being studied for a wide variety of target nuclei, including the Physical Review! An especially beautiful experiment, begun as a missing mass search in the reaction p+d → He3+X° not only studied things of interest to elementary particle physics, the so-called ABC region, but simultaneously, and inadvertently, provided a hadronic probe, the proton, at correlation distances far smaller than, ever achieved before.
122964093
Search for Tachyon Monopoles in Cosmic Rays
We have searched for a particle which combines the properties of a tachyon with those of a magnetic monopole. The tachyon monopole is assumed to exist in cosmic rays striking the earth and to be influenced by the extensive magnetic fringing field of Fermilab's 15-ft. bubble chamber. By hypothesizing that the tachyon monopole will either emit Cherenkov radiation in air or ionize Lexan plastic we set an upper limit of 5 x 10/sup 12/ cm/sup -2/ sec/sup -1/ on their flux.
118813433
A 3 Bev high intensity proton-synchrotron