1 / 15

The Many Uses of Upward-going Muons in Super-K

The Many Uses of Upward-going Muons in Super-K. Muons traveling up into Super-K from high-energy n m reactions in the rock below provide a high-energy insight into many different problems. Alec Habig, Univ. of Minnesota Duluth for the Super-K Collaboration. Upward-going m. SK. SK. m. m.

alisa
Download Presentation

The Many Uses of Upward-going Muons in Super-K

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. The Many Uses of Upward-going Muons in Super-K Muons traveling up into Super-K from high-energy nm reactions in the rock below provide a high-energy insight into many different problems. Alec Habig, Univ. of Minnesota Duluth for the Super-K Collaboration

  2. Upward-going m SK SK m m Stop-m Through-m nm nm • High energy nm can interact in rock some distance away and still produce a m seen by detector • Higher energy particles, more range, more effective volume! • Increasing target mass at high E offsets falling nm spectra • Down-going entering cosmic ray muons restrict this technique to upward-going entering muons Alec Habig

  3. Up-m’s in Super-K • For “SK-I” • 4/96 to 7/01 • 1678 live-days up-thru (1657 up-stop) • More than other SK analyses, this one is insensitive to poor detector conditions • For >7m path (>1.6 GeV): • 1878 thru-m • 456 stop-m Alec Habig

  4. Atmospheric nm Thru-m data Stop-m data No-osc MC (best norm.) Osc. MC • Up-m flux is presented as a function of cosq and thus baseline • cosq=-1 (Up) have L~10,000 km • cosq=0 (Horizontal) have L~500 km • Lower E, longer L n’s oscillate more • The data match the oscillated MC far better than the non-oscillated MC • sin22q=1.0, Dm2=2.7x10-3 Alec Habig

  5. Energy Lever Arm • For nm seen as up-m: • Typical En ~ 10 GeV for stop-m,~ 100 GeV for thru-m • Compare to contained event energies ~ GeV • From the soft atmospheric n spectrum. A harder n spectrum would produce a larger fraction of high energy parent n • Disadvantage – for any single event, the parent n energy is known only to be larger than the observed m energy Alec Habig

  6. nm, nt Oscillation • Even with comparatively small statistics and lousy energy resolution, the observation of nm disappearance at higher energies further refines the oscillation fit • Left – 90% C.L. contours with and without up-m data • Best fit (physical region)*: • sin22q = 1.0 • Dm2 = 2.5x10-3 90% C.L. FC,PC Alone With up-m *(absolute best fit slightly unphysical at sin22q=1.03) Alec Habig

  7. nm to nsterile? • High energy n experience matter effects which suppress oscillations to sterile n • Matter effects not seen in up-m or high-energy PC data • Reduction in neutral current interactions also not seen • constrains ns component of nm disappearance oscillations • Pure nm-ns disfavored • ns fraction < 20% at 90% c.l. Alec Habig

  8. Unusual Models • Alternative ways to make nm disappear without invoking standard nm,nt flavor oscillations include • Lorentz invariance violation • Neutrino decay, decoherence • Fits using all available SK n data (FC+PC+NC+multiring+ up-m, 190 d.o.f.) strongly constrains many such models • Hard for a model to get a good fit over 5 orders of magnitude in energy and 4 in baseline • Long t nm decay and nm decoherence disfavored but not eliminated Alec Habig

  9. Galactic Atmospherics? • Cosmic rays interact with interstellar medium as well as our atmosphere • Would also produce n • ISM most dense at low galactic latitudes • Do we see excess n in the galactic plane? • A search for these n does not see this weak signal Alec Habig

  10. Astrophysical n • A hard n spectrum: more likely a n signal will be seen as up-m • n space-time coincidences with GRBs not seen at any energy in SK • AGNs or other astrophysical sources would produce point sources of high-energy n • All sky searches for such point-sources are negative • Unbinned searches for unusual clustering of up-m also negative Alec Habig

  11. Pick a Source, Any Source • To test your favorite model of n production at some high energy astrophysical source: • Up-m near sources counted, a sampling shown here • Expected count from atm.n background calculated • No excess seen, flux limits computed Alec Habig

  12. WIMP Detection • WIMPs could be seen indirectly via their annihilation products (eventually nm) if they are captured in a gravitational well • WIMPs of larger mass would produce a tighter n beam • Differently sized angular windows allow searches to be optimized for different mass WIMPs Alec Habig

  13. WIMP Results • The Sun, Earth, and Galactic center are potential WIMP traps • No excess of n are seen in any angular cone about them • Upper limit of WIMP-induced n calculated • Varies as a function of possible WIMP mass • Lower limits for higher masses are due to the better S/N in smaller angular search windows Alec Habig

  14. Probing for WIMPs • Most model dependence in indirect searches lies in the cross-section • Most conservative limits are taken for other uncertainties • Direct-detection experiments also do not know cross-sections • Comparisons can be made between direct and indirect searches • Both spin-dependent (left) and spin-independent (right) WIMP-nucleon interactions can be probed (a la Kamionkowski, Ullio, et al) Alec Habig

  15. Summary • The high-energy end of the nm spectrum observed by Super-K is seen as up-going m • The extra lever arm in energy contributes to oscillation parameter estimation out of proportion to the small statistics and poor energy resolution of the sample • The high parent n energies allow probes of unusual areas of physics and astrophysics • Nothing unexpected seen, unfortunately The presenter gratefully acknowledges support for this poster from the National Science Foundation via its RUI grant #0098579, and from The Research Corporation’s Cottrell College Science Award Alec Habig

More Related