1 / 19

26 th CAST Collaboration Meeting

26 th CAST Collaboration Meeting. 2004 γ -Ray Calorimeter results Juan Collar David Miller Joaquin Vieira. A few reminders about the calorimeter operation and data processing Residual energy spectra and search for anomalous events above background The CAST sensitivity to HE axions.

elke
Download Presentation

26 th CAST Collaboration Meeting

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 26th CAST Collaboration Meeting 2004 γ-Ray Calorimeter results Juan Collar David Miller Joaquin Vieira D. W. Miller

  2. A few reminders about the calorimeter operation and data processing Residual energy spectra and search for anomalous events above background The CAST sensitivity to HE axions Extra topics of interest Muon rate, diurnal variation, galactic coord. maps Outline D. W. Miller

  3. Reminders: 2004 Calorimeter Commissioning • Calorimeter Installation: 18 February, 2004 • First Solar Tracking Run: 10 June, 2004 • Extra magnetic shielding installation: 31 July, 2004 • Neutron absorber installation: 15 September, 2004 • Last solar tracking run: 14 November, 2004 D. W. Miller

  4. Reminders: Calorimeter Design and Properties • Large inorganic scintillating crystal (CdWO4) selected for low intrinsic BCKG, g efficiency and PSD • Ø45mm x 50 mm, 0.6 kg • Low-background photomultiplier tube (PMT) • <0.02 Bq 210Pb/kg inner Pb shield • Plastic scintillator as a 4π active muon veto • Borated thermal neutron absorber • Sub-200 keV threshold • 200 MeV dynamic range • Radon displacement D. W. Miller

  5. Front View ~4p Plastic Muon Veto Pb shielding Muon veto PMT Ultra-low bckg Pb Radon disp & Borated thermal n absorber Gammas (from magnet bore) CWO Crystal Light guide Low-BCKG PMT Characteristic pulse large CWO (good PSD,radiopure, efficient) shielded electronics ~16ms rate~4 Hz Brass support tube Side View

  6. HE calorimeter: look for axion-like emissions from solar nuclear transitions(*) MicroMegas X-ray Detector (transparent above few hundred keV) X-ray Telescope adjustable platform for alignment Chicago calorimeter Magnet Platform (*)First direct search of this type D. W. Miller

  7. Pulse shape discrimination D. W. Miller

  8. Details for this data set D. W. Miller

  9. Energy Spectrum • Without position normalized background data • Apparent agreement, butsystematic effect due to the pointing position of the magnet, as in TPC • With position normalization • Error bars increase by factor x2 • Systematic effect of position is removed D. W. Miller

  10. Data processing and results D. W. Miller

  11. Residual spectraDifference between signal (solar tracking) and background Low energy 0.3 – 3 MeV Mid energy 3 – 10 MeV High energy 10 – 50 MeV 3 energy regions to allow for different binning based on detector resolution D. W. Miller

  12. Look for evidence buried in data 95% CL peak Best fit (signal) Best fit (bckg) • Signal: mono-energetic peaks below 10 MeV • Width determined by measured detector resolution • Obtain 95% CL (2σ) for allowed anomalous events at each energy • Above 10 MeV the functional form used becomes more complex (effect of photonuclear reactions) • Dedicated search for specific energy, including escape peaks in fit, yields better sensitivitythansimple gaussian and full-E efficiency (a first-order approach). Best fit (sig+bckg) Example illustrated here is emission at 5.5 MeV (p + d  He + a ….. a ) G. Raffelt and L. Stodolsky, Phys. Lett. B119, 323 (1982). D. W. Miller

  13. From counts to photons • Use the 95% CL allowed counts at each energy and convolve with • Detector efficiency (ε) • livetime (t) D. W. Miller

  14. From photons to axions • Combine: • 95% CL allowed photon flux:Φγ • conversion probability:Pa→γ • helioseismology upper limit on axion flux:Φa • Obtain limit on axion-photon coupling Schlattl, Weiss & Raffelt (hep-ph/9807476): Φa < 0.2 L Assuming maximum allowed Φagives the maximum CAST sensitivity possible D. W. Miller

  15. CAST Limits on HE axions Self-consistent (*) improved limits possible for several energies of interest, e.g. 5.5 MeV(*)i.e., its validity does not depend on an axion luminosity in excess of what is allowed by the properties of the Sun, or the limits on gaγγ from other CAST detectors D. W. Miller

  16. A few extras • Calorimeter information on muon rate variation • Diurnal and position • Galactic coordinate mappings • Calorimeter pointing map • CAST 2004 pointing map for sunrise and sunset detectors D. W. Miller

  17. Diurnal trigger & veto rates • Diurnal variation • 2.5% for trigger rate (after cuts) • 3% muon veto trigger • Diurnal veto rate variation related to veto position dependence • Position normalization corrects for this D. W. Miller

  18. CM Pointing map in Galactic coordinates • Pointing map showing only the number of events….not normalized to time spent per position! • Calculated for same data period as final analysis D. W. Miller

  19. CAST Pointing map in Galactic coordinates • Shown are 2004 Slow Control Entries divided into morning / evening D. W. Miller

More Related