120352716
Status and perspectives of the CAST experiment
The CERN Axion Solar Telescope (CAST) is currently the most sensitive axion helioscope designed to search for axions produced by the Primakoff process in the solar core. CAST is using a Large Hadron Collider (LHC) test magnet where axions could be converted into X-rays with energies up to 10 keV. During the phase I, the experiment operated with vacuum inside the magnet bores and covered axion masses up to 0.02 eV. In the phase II, the magnet bores were filled with a buffer gas (first 4He and later 3He) at various densities in order to extend the sensitivity to higher axion masses (up to f .18 eV). The phase II data taking was completed in 2011. So far, no evidence of axion signal has been found and CAST set the most restrictive experimental limit on the axion-photon coupling constant over a broad range of axion masses. The latest CAST results with 3He data in the mass range 0.39 eV < ma < 0.64 eV will be presented.
18170820
COOLING SYSTEM FOR THE MERIT HIGH‐POWER TARGET EXPERIMENT
MERIT is a proof‐of‐principle experiment of a target station suitable as source for future muon colliders or neutrino factories. When installed at the CERN (European Organization for Nuclear Research) PS (Proton Synchrotron) complex fast‐extracted high‐intensity proton beams intercepted a free mercury jet inside a normal‐conducting, pulsed 15‐T capture solenoid magnet cooled with liquid nitrogen. Up to 25 MJ of Joule heat was dissipated in the magnet during a pulse. The fully automated, remotely controlled cryogenic system of novel design permitted the transfer of nitrogen by the sole means of differential pressures inside the vessels. This fast cycling system permitted several hundred tests in less than three weeks during the 2007 data taking campaign.
59426907
Cryogenic Loop Heat Pipes for the Cooling of Small Particle Detectors at CERN
The loop heat pipe (LHP) is among the most effective heat transfer elements. Its principle is based on a continuous evaporation/condensation process and its passive nature does not require any mechanical devices such as pumps to circulate the cooling agent. Instead a porous wick structure in the evaporator provides the capillary pumping forces to drive the fluid [1]. Cryogenic LHP are investigated as potential candidates for the cooling of future small‐scale particle detectors and upgrades of existing ones. A large spectrum of cryogenic temperatures can be covered by choosing appropriate working fluids. For high luminosity upgrades of existing experiments installed at the Large Hadron Collider (LHC) (TOTEM) and planned ones (FP420) [2–3] being in the design phase, radiation‐hard solutions are studied with noble gases as working fluids to limit the radiolysis effect on molecules detrimental to the functioning of the LHP. The installation compactness requirement of experiments such as the CAST frame‐store C...
26680612
Search for solar axions by the CERN axion solar telescope with 3He buffer gas: closing the hot dark matter gap.
The CERN Axion Solar Telescope has finished its search for solar axions with (3)He buffer gas, covering the search range 0.64 eV ≲ ma ≲ 1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of gaγ ≲ 3.3 × 10(-10)  GeV(-1) at 95% C.L., with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of gaγ, for example by the currently discussed next generation helioscope International AXion Observatory.
46905524
Latest results and prospects of the CERN Axion Solar Telescope
The CERN Axion Solar Telescope (CAST) experiment searches for axions from the Sun converted into few keV photons via the inverse Primakoff effect in the high magnetic field of a superconducting Large Hadron Collider (LHC) decommissioned test magnet. After results obtained with vacuum in the magnet pipes (phase I of the experiment) as well as with 4He the collaboration is now immersed in the data taking with 3He, to be finished in 2011. The status of the experiment will be presented, including a preliminary exclusion plot of the first 3He data. CAST is currently sensitive to realistic QCD axion models at the sub-eV scale, and with axion-photon couplings down to the ~ 2 × 10−10 GeV−1, compatible with solar life limits. Future plans include revisiting vaccuum and 4He configurations with improved sensitivity, as well as possible additional search for non-standard signals from chamaleons, paraphotons or other WISPs. For the longer term, we study the feasibility of an altogether improved version of the axion helioscope concept, with a jump in sensitivity of about one order of magnitude in gaγ beyond CAST.
117736333
Results and perspectives of the solar axion search with the CAST experiment
The status of the solar axion search with the CERN Axion Solar Telescope (CAST) will be presented. Recent results obtained by the use of $^3$He as a buffer gas has allowed us to extend our sensitivity to higher axion masses than our previous measurements with $^4$He. With about 1 h of data taking at each of 252 different pressure settings we have scanned the axion mass range 0.39 eV$ \le m_{a} \le $ 0.64 eV. From the absence of an excess of x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g$_{a\gamma} \le 2.3\times 10^{-10}$ GeV$^{-1}$ at 95% C.L., the exact value depending on the pressure setting. CAST published results represent the best experimental limit on the photon couplings to axions and other similar exotic particles dubbed WISPs (Weakly Interacting Slim Particles) in the considered mass range and for the first time the limit enters the region favored by QCD axion models. Preliminary sensitivities for axion masses up to 1.16 eV will also be shown reaching mean upper limits on the axion-photon coupling of g$_{a\gamma} \le 3.5\times 10^{-10}$ GeV$^{-1}$ at 95% C.L. Expected sensibilities for the extension of the CAST program up to 2014 will be presented. Moreover long term options for a new helioscope experiment will be evoked.
13029463
The Infrared Landau Gauge Gluon Propagator from Lattice QCD
The quenched Landau gauge gluon propagator is investigated in lattice QCD with large assimetric lattices, accessing momenta as low as q ∼ 100 MeV or smaller. Our investigation focus on the IR limit of the gluon dressing function, testing the compatibility with recent solutions of the Dyson‐Schwinger equations. In particular, the low energy parameters κ and α(0) are measured.
49472402
Exploring the Infrared Gluon and Ghost Propagators Using Large Asymmetric Lattices
We report on the infrared limit of the quenched lattice Landau gauge gluon propagator computed from large asymmetric lattices. In particular, the compatibility of the pure power law infrared solution (q2)2k of the Dyson-Schwinger equations is investigated and the exponent k is measured. The lattice data favours k ~ 0.52, which would imply a vanishing zero momentum gluon propagator as predicted by the Kugo-Ojima confinement mechanism and the Zwanziger horizon condition. Results for the ghost propagator and for the running coupling constant are shown.
15370402
Minimal 3-3-1 model, lepton mixing and muonium-antimuonium conversion
The recent experimental results on neutrino oscillation and on muonium–antimuonium conversion require extension of the minimal 3-3-1 model. We review the constraints imposed on the model by these measurements and suggest a pattern of leptonic mixing, with charged leptons in a non-diagonal basis, which accounts for the neutrino physics and circumvents the tight muonium–antimuonium bounds on the model. We also illustrate a scenario where this pattern could be realized.
8333713
Infrared gluon propagator from lattice QCD: Results from large asymmetric lattices
The infrared limit of the lattice Landau gauge gluon propagator is studied. We show that the lattice data are compatible with the pure power law (q{sup 2}){sup 2{kappa}} solution of the Dyson-Schwinger equations. Using various lattice volumes, the infinite volume limit for the exponent {kappa} is measured. Although, the results allow {kappa}=0.498-0.525, the lattice data favor {kappa}{approx}0.52, which would imply a vanishing zero momentum gluon propagator.
109963054
Online neural trigger for optimizing data acquisition during particle beam calibration tests with calorimeters
For LHC, the hadronic calorimetry of the ATLAS detector is performed by Tilecal, a scintillating tile calorimeter. For calibration purposes, a fraction of the Tilecal modules is placed in particle beam lines. Despite beam high quality, experimental beam contamination is observed and this masks the actual performance of the calorimeter. For optimizing the calibration task, an online neural particle classifier was developed for Tilecal. Envisaging a neural trigger for incoming particles, a neural process runs integrated to the data acquisition task and performs online training for particle identification. The neural classification performance is evaluated by correlating the neural response to classical methodology, confirming an ability for outsider identification at levels as high as 99.3%.