Paul Sommers Fermilab PAC Nov 12, 2009 Auger Science South and North
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Transcript of Paul Sommers Fermilab PAC Nov 12, 2009 Auger Science South and North
Paul SommersFermilab PACNov 12, 2009Auger ScienceSouth and North
*Sommers FNALResults from Auger South have already settled some fundamental issues and made clear what is now needed To identify the sources of UHE cosmic raysTo uncover the acceleration processTo establish the particle typesTo test hadronic interaction properties at extreme energies
The key is a systematic study of the trans-GZK particles
Auger North targets this high energy frontier by increasing the aperture of the Auger Observatory by a factor of eight at trans-GZK energies
*Exposure (Auger South, so far)Now nearly ten times the AGASA exposure.
Sommers FNALHiRes @ 10 EeVHiRes @ 100 EeV2 years of full aperture
Spectrum with clear ankle and GZK suppression Anisotropy of arrival directions above 55 EeV Limit on photon flux at 10 EeV using surface detector Limit on photon flux at 3 EeV using fluorescence detector Limit on Earth-skimming tau neutrinos New limit on all flavors of neutrinos using near-horizontal showers Statistical analysis of Xmax values for energies up to 30 EeV
*The Auger Observatory in the Southern Hemisphere Now fully deployed in Argentina
1600 water Cherenkov stations24 fluorescence telescopes (30x30)Sommers FNAL60 km
*The Auger Energy SpectrumReady for publication this month (PLB)SD + FDSommers FNAL
*Five-parameter fit: index, breakpoint, index, critical energy, normalizationSommers FNALThe Auger Energy SpectrumReady for publication this month (PLB)
*Comparison with modelsSommers LodzAnisotropyThe Auger Energy SpectrumReady for publication this month (PLB)
*The Auger Sky above 55 EeV27 events as of November 2007Science 318 (2007), 939 Astroparticle Physics 29 (2008), 188 58 events now (with Swift-BAT AGN density map)Simulated data sets based on isotropy (I) and Swift-BAT model (II) compared to data (black line/point).Sommers FNALLog(Likelihood)
*Shower Depths of Maximum XmaxReady for publication this month (PRL)These suggest high cross section and high multiplicity at high energy.Heavy nuclei? Or protons interacting differently than expected?Information lacking for the (anisotropic) trans-GZK energy regime!(Crucial for calculation of the diffuse cosmogenic neutrino flux)Sommers LodzAnisotropyAnisotropy
*Trans-GZK composition is simplerLight and intermediate nuclei photodisintegrate rapidly.
Only protons and/or heavy nuclei survive more than 20 Mpc distances.
Cosmic magnetic fields should make highly charged nuclei almost isotropic.Sommers Lodz
*Far greater exposure is needed to Identify the class of sources via anisotropy Measure the spectra of bright sources or source regions Determine the particle type(s) above 55 EeV If protons, measure interaction properties above 250 TeV (CM) Determine the diffuse cosmogenic intensity of neutrinos and photons Detect cosmogenic neutrinos and photonsSommers LodzAuger North is designed to have seven times the aperture for trans-GZK cosmic rays. Auger South and North together will have eight times the collecting power of the present Observatory.
*The Ascent of ExposureLogarithmic ScaleLinear ScaleLinsleysx105 LinsleysSommers LodzTA
*Auger exposure to tau NeutrinosNeutrinos can be identified as young showers at very great atmospheric slant depth (either upward or downward).The Auger UHE Neutrino Observatory*Sommers FNAL
*Limit on Tau NeutrinosPhysical Review Letters 100 (2008), 211101Sommers LodzDepends on source spectral index, Emax, and evolution; also on the particle types!
*The UHE Gamma Ray Astronomical WindowPhoton showers penetrate deeper than hadronic showers. They can be recognized individually with hybrid measurements. A photon component can be measured statistically by the surface array.Photon attenuation length exceeds 10 Mpc for E > 2 EeVSommers FNAL
*UHE Photon Limits(strongly constrain top-down scenarios)Sommers FNALAstroparticle Physics 31 (2009), 399 Astroparticle Physics 29 (2008), 243 Astroparticle Physics 27 (2007), 155
*Enhancements at Auger SouthHEAT: High Elevation Auger Telescopes AMIGA: Auger Muon and Infill Ground Array
AERA: Auger Engineering Radio ArraySommers FNAL
*SummaryDeployment is complete for the Auger Observatory in ArgentinaImportant science results:
There IS a suppression of the energy spectrumTrans-GZK arrival directions correlate with local structureEnergy loss (e.g. GZK) is confirmed above 55 EeV (The spectral steepening is not just due to sources running out of steam)There ARE detectable UHE sources within the GZK sphereIntriguing trend in Xmax distributions for energies up to 30 EeVNew Auger limits on diffuse neutrinosNew Auger limits on diffuse photons (ruling out generic top-down models)
Auger North targets the key energy regime above 55 EeVExploit the anisotropy (200 events/year instead of just 25/year)Exploit the simplified composition (only protons and/or heavy nuclei)
Goals:Identify the astrophysical class of sourcesStudy the spectra of the brightest sources or regions individuallyStudy cosmic magnetic fields by spectrometryConstrain hadronic interactions at CM energy > 250 TeVComplementary approach to cosmogenic (GZK) neutrinos and photons: Determine the diffuse fluxes by measuring the trans-GZK cosmicray spectrum and composition, and identifying the type ofastrophysical sources (their evolution) Detect the cosmogenic neutrino and photon fluxes directly(This can test theories for modified neutrino interaction cross sections)Sommers FNAL