Upward Showering Muons in Super-Kamiokande Shantanu Desai /Alec Habig For Super-Kamiokande Collaboration ICRC 5 Pune
Upward Going Muons in Super-K.5 THRU STOP dφ/dloge υ ( 1-13 cm - s -1 sr -1 ).45.4.35.3.5..15.1.5 E υ (GeV) Thrugoing Stopping 1 1 1 1 3 1 4 1 5
Muon Energy loss as a function of Energy Non-Showering muon Showering Muon < de/dx (MeV cm g -1 ) > 1 1 Total Loss Radiative Loss Ionization Loss Average < de/dx > from M.C. E i L E f de/dx = (E i - E f )/L Distribution asymmetric for each muon energies 1 1 1 1 1 3 1 4 1 5 Muon energy (GeV) (Groom et al 3) Reasonably good agreement of Monte-Carlo with PDG Aim of this analysis is only to separate a given muon into showering/non-showering
Corrections to raw PMT charge Muon track d wat PMT Apply following correction for every PMT in Cherenkov Cone q corr = q raw d wat exp(d wat /L atten ) -------------------------- F(θ) where L atten = Water attenuation length, d wat = Distance from PMT to point of projection to µ track F(θ) = PMT acceptance + shadowing Divide the muon track into 5 cm bins. For each bin, calculate average corrected charge and its error as follows: i Q corr N pmt 1 q corr N pmt where N pmt = No of pmts within the given projected distance corresponding to each bin i Qcorr 1 N pmt N pmt 1 q corr q raw
Corrections to raw PMT charge Muon track d wat PMT Apply following correction for every PMT in Cherenkov Cone q corr = q raw d wat exp(d wat /L atten ) -------------------------- F(θ) where L atten = Water attenuation length, d wat = Distance from PMT to point of projection to µ track F(θ) = PMT acceptance + shadowing Divide the muon track into 5 cm bins. For each bin, calculate average corrected charge and its statistical error as follows: i Q corr i Qcorr N pmt 1 1 N pmt N pmt q corr N pmt q corr 1 q raw where N pmt = No of pmts within the given projected distance corresponding to each bin
Corrected Charge Distribution Comparison of ionizing vs showering muon Mean corrected photo-electrons /.5 m 9 8 7 6 5 4 3 1 Muon Energy = GeV Muon Energy = 1 TeV 4 6 8 1 1 14 16 18 Projected Distance Along Track (m) Mean corrected photo-electrons /.5 m 9 8 7 6 5 4 3 1 4 6 8 1 1 14 16 18 Projected Distance Along Track (m) de/dx =.16 MeV/cm de/dx = 8.5 MeV/cm Both simulated muons have same entry point and direction
{ { Variables used for showering/non-showering separation n i3 where and i Q corr Q corr i Qcorr Shape Comparison n3 4 Q corr n3 4 qlq corr i Q corr i Qcorr 1 i Qcorr Q corr ql Absolute Corrected Charge Comparison (Average corrected charge averaged over entire muon length) for a ionizing muon as a function of path-length Difference in average corrected charge of given muon same for ionzing muon
No of events 6 5 4 3 Data M.C. Variables when applied to 1yr upmu NEUT Monte-Carlo χ comparison for data and monte-carlo 1.5 1 1.5.5 3 3.5 log1 (Σ {(de/dx) i - mean} /dof) 18 16 14 Data Monte-Carlo No of events 1 1 8 6 4-4 - 4 6 8 1 [ mean q corr - Q(L) ] comparison for data and monte-carlo
SHOWERING CUT USED χ /DOF >4 and >1. OR χ /DOF >3 and >. OR χ /DOF> and >.5 OR χ /DOF>5 and >.5 OR > 4.5 Total no of showering events = 5575 (out of 3731) in 1 year upmu NEUT Monte-carlo Efficiency = 71 % where, Efficiency = No of events Identified by algorithm --------------------------------------------- No of events with E / X >.85 MeV/cm E = Energy deposited by muon in inner detector X = Length of muon in inner detector
NEUTRINO ENERGY SPECTRA dφ/dloge υ ( 1-13 cm - s -1 sr -1 ).5.45.4.35.3.5..15.1 Showering Non-showering Stopping <E υ > ~ 1 GeV <E υ > ~ 1 GeV <E υ > ~ 1 TeV.5 1 1 1 1 3 1 4 1 5 E υ (GeV)
Event Display of upward showering muon Super-Kamiokande Run 11 Sub 3 Ev 1539 96-7-5:1:46:37 13 dee4 66 Inner: 1877 hits, 19145 pe Outer: 49 hits, 863 pe (in-time) Trigger ID: xb D wall: 169. cm Upward-Going Muon Mode Charge(pe) >6.7 3.3-6.7.-3.3 17.3-. 14.7-17.3 1.-14.7 1.-1. 8.-1. 6.- 8. 4.7-6. 3.3-4.7.- 3.3 1.3-..7-1.3.-.7 <. 16 1 8 4 5 1 15 Times (ns)
Angular Resolution of showering muons 4 Angular resolution of Showering thrumus Shaded region contains 68 % of total area µ true µ fit Angular resolution = 1.5 No of events 35 3 5 15 1 5 1 3 4 5 6 7 8 9 1 Angle between precision fit and truth fit Thrugoing muons : Angular resolution ~ 1 Stopping muons : Angular resolution ~ 1
Zenith-angle distribution of showering muons 1 No Oscillation m =.5 sin Θ =1. 8 No of events 6 4-1 -.9 -.8 -.7 -.6 -.5 -.4 -.3 -. -.1 cosθ Showering muons relatively insenstive to oscillation ==> For this dataset chi-square for null -oscillation should be very good fit
Background Subtraction Applied the showering algorithm to horizontal thrugoing muon with < cos(θ)<.8 Azimuth distribution of all showering muons (1) () (1) 1 3 19.48 / 14 P1 1.7.8869 P 1.78.789 P3 65.17 1.86 No of Events 1 3 1 Number of Events 1 1 Region (1) Φ < 6, Φ > 4 Region () 6 < Φ < 4 1 1 1 5 1 15 5 3 35 Φ (degrees) 1-1 -.1 -.8 -.6 -.4 -...4.6.8 cosθ Fit to thin rock zenith angle distribution: f[cos(θ)] = p1+ exp [p+p3 cos(θ)] N bkgd = 8.63 +1-5 for cos(θ)> -.1 (Asymmetric distribution because of bump near horizon)
Showering Muon Oscillation Results Best-fit (physical region) : χ = 4.68 / 7 dof for ( m, sin θ) = (.14 ev,.9) Best-fit (null oscillation) : χ = 6.51/9 dof 1 9 No of showering muons 8 7 6 5 4 3 1-1 -.9 -.8 -.7 -.6 -.5 -.4 -.3 -. -.1 cosθ Zenith angle comparison at best fit point Null oscillation normalized by livetime
Projections of chi-square distributions for showering muons 1 8 99% C.L. 9% C.L. 68% C.L. 1 8 99% C.L. 9% C.L. 68% C.L. χ - χ min 6 4 χ - χ min 6 4 1-4 1-3 1 - m (ev )..4.6.8 1 1. 1.4 sin θ Null oscillation allowed even at 68 % confidence level as expected for this high energy ν µ with mean energy of ~ 1 TeV
Comparison with all upward thrugoing muons 1 1 8 99% C.L. 9% C.L. 68% C.L. 8 99% C.L. 9% C.L. 68% C.L. χ - χ min 6 4 χ - χ min 6 4 1-4 1-3 1 -..4.6.8 1 1. 1.4 m (ev ) sin θ Best-fit : χ = 7.64 / 7 dof for ( m, sin θ) = (.4 ev,.96) Best-fit at null oscillation : χ = 19.6/9 dof Upward thrugoing muons sensitive to neutrino oscillation
CONCLUSIONS A sample of upward thrugoing muons which lose energy through radiative processes have been identified. Mean energy of parent neutrinos of upward showering muons ~ 1 TeV. 5575 showering muons in 1yr neut Monte-carlo and 39 events in 1679.6 days data Zenith angle distribution of upward showering muons consistent with null oscillations This dataset will now be used for oscillation analysis with all datasets by providing an extra energy bin at highest energies. A variety of astrophysical searches with upward showering muons done. Nothing found. (S. Desai thesis 3. Also A. Habig poster)