recent results in k2k experiment shimpei yamamoto (kyoto univ.) 10 th icepp symposium @hakuba...
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RECENT RESULTS IN K2K RECENT RESULTS IN K2K EXPERIMENTEXPERIMENT
RECENT RESULTS IN K2K RECENT RESULTS IN K2K EXPERIMENTEXPERIMENT
Shimpei YAMAMOTO (Kyoto Univ.)10th ICEPP Symposium @Hakuba
16-FEB-2004
Shimpei YAMAMOTO (Kyoto Univ.)10th ICEPP Symposium @Hakuba
16-FEB-2004
10th ICEPP Symposium @Hakuba 2
• JAPAN: High Energy Accelerator Research Organization (KEK)Institute for Cosmic Ray Research (ICRR), University of
TokyoKobe University / Kyoto University Niigata University / Okayama University Tokyo University of Science / Tohoku University
• KOREA: Chonnam National UniversityDongshin University / Korea UniversitySeoul National University
• U.S.A.: Boston University / University of California, IrvineUniversity of Hawaii, ManoaMassachusetts Institute of TechnologyState University of New York at Stony BrookUniversity of Washington at Seattle
• POLAND: Warsaw University / Solton Institute
Since 2002• JAPAN: Hiroshima University, Osaka University• CANADA: TRIUMF / University of British Columbia• EUROPE: Rome / Saclay / Barcelona / Valencia / Geneva • RUSSIA: INR-Moscow
K2K collaborationK2K collaborationK2K collaborationK2K collaboration
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OutlineOutlineOutlineOutline
K2K & neutrino oscillationRecent status & results
– →x oscillation analysis– e appearance– New near detector “SciBar”
ProspectsSummary
K2K & neutrino oscillationRecent status & results
– →x oscillation analysis– e appearance– New near detector “SciBar”
ProspectsSummary
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K2K LBL K2K LBL oscillation exp. oscillation exp.K2K LBL K2K LBL oscillation exp. oscillation exp.
KEKSK
1kt
SciFi
MRD
LG(K2K-I)SciBar(K2K-II)
Near DetectorsNear Detectors
<E>=1.3GeVL=250km (fixed)
98%
Super-Kamiokande(SK)Super-Kamiokande(SK)
50kt water cherenkovdetector(22.5kt fid. vol.)
12GeV-PS@KEK12GeV-PS@KEK beamlinebeamline
Beam monitorBeam monitor
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Neutrino Oscillation in K2KNeutrino Oscillation in K2KNeutrino Oscillation in K2KNeutrino Oscillation in K2Koscillation prob.:oscillation prob.:
[GeV]
[km]][eV27.1sin2sin1)( 222
E
LmP
232 103,250 eVmkmL Aiming resultsAiming results::
–Reduction of Reduction of events events–Distortion of Distortion of spectrum spectrum–ee appearance appearance
osci. parameters (sinosci. parameters (sin2222θθ,,ΔΔmm22))
–Near to far extrapolationNear to far extrapolation–Rate & spectrum shape @SKRate & spectrum shape @SK
null oscillationnull oscillationw/ oscillationw/ oscillation
E(GeV)
E(GeV)
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Neutrino BeamlineNeutrino BeamlineNeutrino BeamlineNeutrino Beamline
pp+Al +Al
++ e++e (1.3%) +(0.5%)
double hormdouble horm: high eff. of : high eff. of collection collectionPion monitorPion monitor: near/far flux ratio: near/far flux ratioMuon monitorMuon monitor: beam intensity & direction: beam intensity & direction
•FFast extraction every 2.2secast extraction every 2.2sec•BBeam spill 1.1useam spill 1.1us
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Near Detectors (ND)Near Detectors (ND)Near Detectors (ND)Near Detectors (ND) fiducialfiducial1kt Water Cherenkov detector (KT) 25 ton same type as SK1kt Water Cherenkov detector (KT) 25 ton same type as SKScintillation Fiber tracker (SciFi) 6 ton detect protons Scintillation Fiber tracker (SciFi) 6 ton detect protons QE/nQEQE/nQEMuon Range Detector (MRD) ~700 ton (Fe) Muon Range Detector (MRD) ~700 ton (Fe) beam beam monitormonitorLead Glass calorimeter (LG) detect electrons Lead Glass calorimeter (LG) detect electrons from SciFifrom SciFi K2K-IK2K-I
Mar,1999 – Jul,2001Mar,1999 – Jul,2001 SKI (11146PMTs)SKI (11146PMTs) || SK accidentSK accident ||K2K-IIK2K-II Dec,2002 –Dec,2002 – SKII (~5200PMTs)SKII (~5200PMTs) LG removedLG removed SciBar (Oct,2003 -)SciBar (Oct,2003 -)
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Delivered protons on targetDelivered protons on targetDelivered protons on targetDelivered protons on target
5~6x105~6x101212
((protons per pulseprotons per pulse))
10/7
12/21
6/23
12/23‘99 ‘00 ‘01 ‘02 ‘03
K2K-IIK2K-I
9.5x109.5x101919 POT POT(8.4x10(8.4x101919 for analysis) for analysis)
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K2K event selection in SKK2K event selection in SKK2K event selection in SKK2K event selection in SK
Tspill TSK
GPS
TSpill: Abs. time of spill startTSK: Abs. time of SK eventTOF: 0.83ms (KEK to Kamioka)
sec3.1TOF2.0 SpillSK TTT
No Decay-e
HE Trig.
FC: fully contained (No activity in Outer Detector) FV: 22.5kt Fiducial VolumeExpected atm. BG
~2x10-3 within 1.5s.
1.5s
500sec
5sec
FCFV
72 events
Jun.’99 – Apr.’036.4 x 1019 proton on target
K2K-I + part of K2K-II
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K2K events in SKK2K events in SKK2K events in SKK2K events in SK
Jun.1999~Apr.2003Jun.1999~Apr.2003
K2K-IK2K-I((56 events56 events))
K2K-IIK2K-II((+16 events+16 events))
→→XX oscillation oscillation analysis (K2K-I)analysis (K2K-I)→→XX oscillation oscillation analysis (K2K-I)analysis (K2K-I)
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Analysis flowAnalysis flowAnalysis flowAnalysis flow
–NNSKSK : Number of FCFV events : Number of FCFV events–SSSKSK(E(E
recrec)) : : EErec rec distribution (shape) of 1Rdistribution (shape) of 1R
•Num. of events & Observed Num. of events & Observed ((pp,,)) distributions distributions •Neutrino FluxNeutrino Flux•Fit Fit spectrum & interaction model spectrum & interaction model
– ffnearnear(E(E) (8 bins)) (8 bins)– nQE/QE rationQE/QE ratio– Error matrix (to include correlation)Error matrix (to include correlation)
Near to Far extrapolation: Near to Far extrapolation: RRFNFN(E(E))
Near siteNear site
Prediction @far sitePrediction @far site
Use Maximum Likelihood Fit in Use Maximum Likelihood Fit in (sin(sin2222, , mm22))
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Reconstruction of EReconstruction of EReconstruction of EReconstruction of E
cos
2/E
2
PEm
mEm
n
n
rec
proton
p
•Use single-ring Use single-ring -like FCFV (1R-like FCFV (1R) events) events
•Assume Assume QE int.QE int. and and reconstruct Ereconstruct E
( ~50% of K2K 1R events are CCQE)
E rec. @SK:E rec. @SK:
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interaction (~1GeV)interaction (~1GeV) interaction (~1GeV)interaction (~1GeV)Charged current quasi-elastic scat, (CCQE)Charged current quasi-elastic scat, (CCQE)
pion productions (nonQE)pion productions (nonQE)
p: muon momentum
: muon angle
proton
p
nucleon
p
※ ※ EE can be reconstructed can be reconstructed from from PP and and ..
1kt : single ring 1kt : single ring -like FCFV-like FCFVSciFi: QE-like 2trackSciFi: QE-like 2track single track (proton invisible)single track (proton invisible)
1kt : single/multi ring FCFV1kt : single/multi ring FCFVSciFi: nonQE-like 2trackSciFi: nonQE-like 2track
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• 1KT : P<1.5GeV/c, 4 acceptance– 1-ring -like(1R) fully contained
in Fid.25ton(FC) : 22,476ev.• SciFi : P>1GeV/c, <60deg.
– 1-track -like : 5963ev.– 2-track QE-like (p<25deg.) : 764ev.– 2-track nonQE-like (p>30deg.) : 1288ev.
• PIMON– (p,) distribution ⇒ Neutrino Spectrum (>1GeV)
Fitting Parameters
E: 8 bins, nonQE/QE ratio
Spectrum measurement Spectrum measurement @ND@ND
Spectrum measurement Spectrum measurement @ND@ND
nonQE-likenonQE-like
QE-likeQE-like
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SciFi pSciFi p//SciFi pSciFi p//
1-track
2-trackQE-like
2-tracknQE-like
P
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1kt p1kt p// 1kt p1kt p// pp andand distributions of 1kt 1ring distributions of 1kt 1ring -like FCFV events-like FCFV events
P
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Allowed region (Allowed region (→→XX))Allowed region (Allowed region (→→XX))
Allowed region
Use both Number of events + Spectrum shape(June ’99 – July ’01) (Nov. ’99 – July ’01)
Null oscillation probability: Null oscillation probability: less than 1%less than 1%.. mm22=1.5~3.9 x 10-3 eV=1.5~3.9 x 10-3 eV22, ,
sinsin2222=1(90%CL)=1(90%CL)
68%90%99%
80.1+6.2 -5.4 exp56obs ↔
Normalized by area
reconstructed E
Expectation w/o oscillation
Best FitBest fit point2.8x10-3
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Comparison w/ SK resultComparison w/ SK resultComparison w/ SK resultComparison w/ SK result
90% C.L.90% C.L.
K2KK2K
SKSK
Search for Search for ee appearanceappearance
(K2K-I)(K2K-I)
Search for Search for ee appearanceappearance
(K2K-I)(K2K-I)
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Search for Search for ee appearance appearanceSearch for Search for ee appearance appearanceFully contained – Single ring – e-likeFully contained – Single ring – e-like (ring pattern and opening angle)(ring pattern and opening angle)Visible energy>100MeV – w/o decay electronsVisible energy>100MeV – w/o decay electrons
Ring pattern
Opening angle
To be submitted for publication
data
MC
NC of MC
e MC
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Data reduction summaryData reduction summaryData reduction summaryData reduction summary
DATA SETDATA SET: June’99 – July’01June’99 – July’01 (4.8×10 (4.8×101919POT)POT)
DATA MC beam e MC signal e MC (CC)
sin22e=1 , m2=2.8x10-3eV2
80 28
20
18
18
16
50
2.9
2.6
2.0 w/o decay-e 1 0.35
FCFV 56 0.82 Single ring 32 0.48 PID (e-like) 1 0.42
Evis>100MeV
1 0.41
NC:87% CC1:7% CCm4% CCQE:2%
electron candidate: electron candidate: 1 event (obs.)1 event (obs.) 2.4 events (exp.)2.4 events (exp.)
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Excluded regionExcluded region→→ee))Excluded regionExcluded region→→ee))
sin22e
m2 (
eV2 )
K2K(90%CL)K2K(90%CL)
CHOOZ(90%CL)CHOOZ(90%CL)ee disappearancedisappearance
SK atm.SK atm. allowed (90%CL)allowed (90%CL)
Near Detector UpgradeNear Detector UpgradeNear Detector UpgradeNear Detector Upgrade
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SciBar SciBar detectordetectorSciBar SciBar detectordetector
Spec. & analysis status will be presented by following talkers.
Spec. & analysis status will be presented by following talkers.
Upgrade near detector to explore Upgrade near detector to explore low E regionlow E region(after removal of LG)(after removal of LG)
•Fine segmented scintillator Fine segmented scintillator trackertracker•Scintillator target & fully activeScintillator target & fully active
2003.10.03~2003.10.03~
Working well !!Working well !!
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ProspectsProspectsProspectsProspects
•K2K-II is running stablyK2K-II is running stably━ flux in low energy region by SciBarflux in low energy region by SciBar━SciFI SciFI flux measurement using PID flux measurement using PID━Improvement of Near/Far extrapolation (Harp)Improvement of Near/Far extrapolation (Harp)━K2K events in SK-II K2K events in SK-II
New results of oscillation analysis come soon !New results of oscillation analysis come soon !
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SummarySummarySummarySummary• K2K-I data has been analyzed so far:K2K-I data has been analyzed so far:
– →→xx oscillation analysis oscillation analysisNull oscillation prob: less than 1%Null oscillation prob: less than 1%mm22=1.5~3.9 x 10=1.5~3.9 x 10-3-3 eV eV22
@sin@sin2222=1(90%CL) (consistent w/ atm. =1(90%CL) (consistent w/ atm. ))– ee appearance search appearance search
1 1 e e candidate (consistent with BG)candidate (consistent with BG)• K2K-II running stablyK2K-II running stably
– New near detector SciBarNew near detector SciBar– Low energy neutrino flux @NDLow energy neutrino flux @ND– K2K events in SK-IIK2K events in SK-II– New results of oscillation analysis will New results of oscillation analysis will
come sooncome soon
• K2K-I data has been analyzed so far:K2K-I data has been analyzed so far:– →→xx oscillation analysis oscillation analysis
Null oscillation prob: less than 1%Null oscillation prob: less than 1%mm22=1.5~3.9 x 10=1.5~3.9 x 10-3-3 eV eV22
@sin@sin2222=1(90%CL) (consistent w/ atm. =1(90%CL) (consistent w/ atm. ))– ee appearance search appearance search
1 1 e e candidate (consistent with BG)candidate (consistent with BG)• K2K-II running stablyK2K-II running stably
– New near detector SciBarNew near detector SciBar– Low energy neutrino flux @NDLow energy neutrino flux @ND– K2K events in SK-IIK2K events in SK-II– New results of oscillation analysis will New results of oscillation analysis will
come sooncome soon
supplementssupplementssupplementssupplements
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Pion monitorPion monitorPion monitorPion monitor
Measure Momentum / Angle Dist. of π’s Just after Horn/Target
+Well known π Decay Kinematics +Well Defined Decay Volume Geometry
⇒Predict νμ Energy Spectrum at Near Site Far Site νμ Flux Ratio (Far/Near) as a Function of Neutrino Energy
Ring Image Gas Cherenkov Detector (Index of Refraction is Changeable)
To Avoid Severe Proton Beam Background,νμ Energy Information above 1GeV is Available(β of 12GeV Proton ~ β of 2GeV π)
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Muon monitorMuon monitorMuon monitorMuon monitor
Behind beam dumpsensitive to initially high energy (>5.5GeV)Provide fast (spill-by-spill) monitoring of
Intensity targeting/horn stabilityProfile beam direction
Segmented Ionization Chamber
Silicon Pad Detector Array
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Stability of Stability of spectrum @ND spectrum @NDStability of Stability of spectrum @ND spectrum @NDNeutrino spectrum measurement by the Pion monitorEnergy and angle of muons produced in the CC interactions by MRD
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ee candidate event candidate eventee candidate event candidate event
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Method of Method of flux fitting (ND) flux fitting (ND)Method of Method of flux fitting (ND) flux fitting (ND)
2=227 for 197 d.o.f. (90 from 1kt, 137 from FGD)for fitted (p) dist. of 1KT and FGD (124 data points)
0 ~0.5 GeV
0.5 ~0.75GeV
0.75 ~1.0GeV
E QE(MC) non-QE(MC)
neutrino spectrum (E) and interaction model (QE/non-QE ratio).
Fit the parameters.
Measured (p)
7bins•••
•••
8bins
p
p
Prepare MC templates
(E) , QE/non-QE ratio …
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Contribution of sys. errors on Contribution of sys. errors on spectrumspectrum
Contribution of sys. errors on Contribution of sys. errors on spectrumspectrum
Total
Spec. nQE/QE Spec.+nQE/QE
F/N SK SK Escale