recent results in k2k experiment shimpei yamamoto (kyoto univ.) 10 th icepp symposium @hakuba...

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


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


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


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)


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


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 -)


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)


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


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)


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))


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:


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


• 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


SciFi pSciFi p//SciFi pSciFi p//

1-track

2-trackQE-like

2-tracknQE-like

P


1kt p1kt p// 1kt p1kt p// pp andand distributions of 1kt 1ring distributions of 1kt 1ring -like FCFV events-like FCFV events

P


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


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)


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


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.)


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


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 !!


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 !


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


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)


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


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


ee candidate event candidate eventee candidate event candidate event


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 …


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

recent results in k2k experiment shimpei yamamoto (kyoto univ.) 10 th icepp symposium @hakuba...

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