1 Status of Neutrino Beamline Construction K. Nishikawa IPNS, KEK 2006 . 12 . 4.
New results from K2K Makoto Yoshida (IPNS, KEK) for the K2K collaboration NuFACT02, July 4, 2002...
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Transcript of New results from K2K Makoto Yoshida (IPNS, KEK) for the K2K collaboration NuFACT02, July 4, 2002...
New results from K2KNew results from K2K
Makoto Yoshida (IPNS, KEK)for the K2K collaboration
NuFACT02, July 4, 2002London, UK
K2K CollaborationK2K CollaborationHigh Energy Accelerator Research Organization(KEK)
Institute for Cosmic Ray Research(ICRR), University of TokyoKobe UniversityKyoto UniversityNiigata University
Okayama UniversityTokyo University of Science
Tohoku University
Chonnam National UniversityDongshin University
Korea UniversitySeoul National University
Boston UniversityUniversity of California, IrvineUniversity of Hawaii, Manoa
Massachusetts Institute of TechnologyState University of New York at Stony Brook
University of Washington at Seattle
Warsaw University Soltan Institute for Nuclear Study
• Neutrino beam almost pure (98%) <E>~1.3GeV• Near detectors
Measure flux/spectrum• Far detector Super-Kamiokande (SK) 250 km far from KEK• disappearance and e appearance
K2K long baseline neutrino oscillation experiment
KEK beam line Beam monitor Near detectors
Kamioka•Super-K
250km250km
Neutrino oscillations in K2K
)/27.1(sin)2(sin1)( 222 ELmP
Spectrumdistortion
disappearance
K2K aims to observe• deficit in number of events• distortion of spectrum
after 250 km travel
Fixed to 250 km
prob
abili
ty
E=1.3 GeV
232 103,250 eVmkmL
Super-Kamiokande
39 m
41 m
• 50kton Water Cherenkov detector• 1000m underground• 22.5kton fiducial mass• Inner detector 11146 PMTs(20’’)• Outer detector 1885 PMTs(8’’)• Atmospheric B.G. against K2K ~10-5 events/day in beam spill (1.1s/2.2s)
Neutrino Beam Line @KEK
200m
12GeV PS1.1sec / 2.2sec beam spill6x1012 protons/spill
Pion monitor
p, after Horn
p+Al + Near neutrino detectors
Flux/spectrum
Near to Far flux ratio RFN
Double Horn 250kA x20
Muon Range
Detector
Near neutrino detectors
• 1kton water Cherenkov detector (1KT) same type as SK (25ton fiducial)• Fine Grained Detectors (FGD)
• Scintillation fiber tracker (SciFi) w/ water target (6ton fiducial)CCQE identification
• Lead glass calorimeter (LG) detect electrons from SciFi• Muon range detector (MRD) measure muon momentum
beam monitor (Fe, 330ton fiducial)
K2K Results in 2001
Tspill TSK
GPSsecμ3.1TOF0.2 SpillSK TTΔT
w/o pre-activity
p.e. >200
1.5s
500sec
5sec
T (sec)
Fully Contained eventsin Fiducial Volume (FCFV)
56 events observed 7.38.0
80 expected
in null oscillation case
Probability < 3%
Number of FCFV events (NSK)
What’s new
• Same data set as in last year
• spectrum at near site
• Oscillation analysis (NSK+ Shape)only NSK in last year
• Full error treatment
to include correlation
Far site• Total number events• Spectrum shape
Strategy
Near site• Number of neutrino events• muon distributions of neutrino events Fit for neutrino spectrum & interaction model
Near to Far extrapolationRFN(E)
Event categories for spectrum measurement at near site
1KT: single ring -like FCFV events (1RFGD: single track events
proton
p
proton
p
proton
p
p: muon momentum
: muon angle
FGD: QE-like 2-track events
FGD: nQE-like 2-track events
QE and nQE in SciFi 2track events
nQE-like QE-like
Water Target + Al(20%)Fiducial Mass : 6 tonE ~150MeVEvent Rate ~ 1/1000pulses
Fitting Method
Fitted (p) dist. of 1KT and FGD2=227 for 197 d.o.f. (90 from 1KT, 137 from FGD)
••
••
0- 0.5 GeV
0.5- 0.75GeV
0.75- 1.0GeV
E QE (MC) nQE(MC)
MC templates for neutrino spectrum (E) (8bin)and interaction model (QE/nQE)
Fitted (p) = weighted mean of MC templetes
Measured (p)
1KT distributions with fitted results
Reasonable fitted distribution
FGD distributions with fitted results
1-track
2-trackQE-like
2-tracknQE-like
CCQE (MC)
P
Good agreement for ALL sample
μμμN
2μμNrec
ν cosθpEm
2mEmE
proton
: muon angle
p: muon momentum
Reconstruct neutrino energy assuming CCQE
Use single-ring -like FCFV events (1R)
Neutrino spectrum reconstruction in SK
Oscillation analysisData Sets• For number of events (NSK) June ’99-July ’01
FCFV events (56 events)• For spectrum shape
Nov ’99-July ’011R events (29 events)
Method-1 Maximum Likelihood method
Normalization term
Nexp= 80.1+6.2-5.4
Shape term Constraint term for syst. parameter. (error matrices)
Ltot = Lnorm(f) Lshape(f) Lsyst(f)
Method-2 different treatment of syst. term. Generate many MC samples with syst. parm. changed within error.
Ltot = mean value for the MC samples
Allowed m2 by NSK and Shape only analysis
NSK and shape analysis indicate the same m2 region for sin22=1
Number of Events only
Spectrum Shape only
NSK+Shape
Merged analysis (NSK and Shape) to get allowed region.
K2K Allowed region (Shape+Norm)
1.5~3.9x10-3eV2
for sin22=1 @90%CL
Consistent with atm. resultcf. Atmospheric results m2=(1.6~3.9)x10-3 eV2
for sin22=1.0
Best fit oscillation parameter (sin22 , m2)method-1 method-2
Shape only (1.09, 3.0x10-3eV2) (1.05, 3.2x10-3eV2)NSK +Shape (1.03, 2.8x10-3eV2) (1.05, 2.7x10-3eV2)
Shape and NSK @ Best Fit
Best fit
normalized by area
method 1•NSK prediction =54 (obs 56)•KS test prob.(shape)= 79%
method 2•NSK 82%•shape 93%•NSK+shape 50%
Null oscillation
NSK and Shape are reasonable at best fit point
Null Oscillation Probability method-1 method-2
NSKonly 1.3% 0.7%Shape only 15.7% 14.3%NSK+Shape 0.7% 0.4%
Prob. for null oscillation case is less than 1%
Conclusion• Neutrino spectrum in K2K has been measured by usin
g near detectors• Oscillation analysis with number of events and spectr
um shape on June99 ~July01 data
• Analysis for NSK and for shape indicate consistent m2 region for sin22=1
• Analysis for NSK+Shape gives m2=1.5~3.9x10-3eV2
for sin22=1 @ 90%CL• Null oscillation probability is less than 1%
• Resume data taking this winter and make statistics 2 times more