Transcript Title

RECENT RESULTS IN K2K
EXPERIMENT
Shimpei YAMAMOTO (Kyoto Univ.)
10th ICEPP Symposium @Hakuba
16-FEB-2004
K2K collaboration
• JAPAN: High Energy Accelerator Research Organization (KEK)
Institute for Cosmic Ray Research (ICRR), University of Tokyo
Kobe University / Kyoto University
Niigata University / Okayama University
Tokyo University of Science / Tohoku University
• KOREA: Chonnam National University
Dongshin University / Korea University
Seoul National University
• U.S.A.: Boston University / University of California, Irvine
University of Hawaii, Manoa
Massachusetts Institute of Technology
State University of New York at Stony Brook
University 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
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Outline
K2K & neutrino oscillation
Recent status & results
– nm→nx oscillation analysis
– ne appearance
– New near detector “SciBar”
Prospects
Summary
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K2K LBL n oscillation exp.
Super-Kamiokande(SK)
LG(K2K-I) SciFi
SciBar(K2K-II)
50kt water cherenkov
detector
(22.5kt fid. vol.)
MRD
nm
<En>=1.3GeV
L=250km (fixed)
98% nm
SK
nm
1kt
Near Detectors
12GeV-PS@KEK
n beamline
Beam monitor
KEK
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Neutrino Oscillation in K2K
oscillation prob.:

L[km] 
2
2

P(n m n m )  1  sin 2 sin1.27m [eV ]
E[GeV] 

2
L  250km, m2  3103 eV 2
E(GeV)
null oscillation
w/ oscillation
Aiming results:
–Reduction of n events
–Distortion of nm spectrum
–ne appearance
 osci. parameters (sin22θ,Δm2)
–Near to far extrapolation
–Rate & spectrum shape @SK
E(GeV)
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Neutrino Beamline
p+Al  p+
 m+ + nm
e++ne (1.3%) +nm (0.5%)
double horm: high eff. of p collection
Pion monitor: near/far flux ratio
Muon monitor: beam intensity & direction
10th ICEPP Symposium @Hakuba
•Fast extraction every 2.2sec
•Beam spill 1.1us
6
Near Detectors (ND)
1kt Water Cherenkov detector (KT)
Scintillation Fiber tracker (SciFi)
Muon Range Detector (MRD)
Lead Glass calorimeter (LG)
fiducial
25 ton same type as SK
6 ton detect protons  QE/nQE
~700 ton (Fe)
n beam monitor
detect electrons from SciFi
K2K-I
Mar,1999 – Jul,2001
SKI (11146PMTs)
|
SK accident
|
K2K-II
Dec,2002 –
SKII (~5200PMTs)
LG removed
SciBar (Oct,2003 -)
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Delivered protons on target
9.5x1019 POT
(8.4x1019 for analysis)
‘99
‘00
‘01
‘02
‘03
12/23
10/7
6/23
12/21
K2K-I
K2K-II
5~6x1012
(protons per pulse)
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K2K event selection in SK
GPS
 0.2  T  TSK  TSpill  TOF 1.3m sec
500msec
HE Trig.
No Decay-e
FCFV
5msec
Tspill
TSK
TSpill: Abs. time of spill start
TSK: Abs. time of SK event
TOF: 0.83ms (KEK to Kamioka)
Jun.’99 – Apr.’03
6.4 x 1019 proton on target
K2K-I + part of K2K-II
72 events
1.5ms
FC: fully contained
(No activity in Outer Detector)
FV: 22.5kt Fiducial Volume
Expected atm. n BG
~2x10-3 within 1.5ms.
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K2K events in SK
Jun.1999~Apr.2003
K2K-I
(56 events)
K2K-II
(+16 events)
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nm→nX oscillation analysis
(K2K-I)
Analysis flow
Near site
•Num. of events & Observed (pm,m) distributions

•Neutrino Flux
•Fit nm spectrum & interaction model
– fnear(En) (8 bins)
– nQE/QE ratio
– Error matrix (to include correlation)
Near to Far extrapolation: RFN(En)
Prediction @far site
–NSK
: Number of FCFV events
–SSK(Enrec) : Enrec distribution (shape) of 1Rm
Use Maximum Likelihood Fit in (sin22, m2)
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Reconstruction of En
m
nm
m
pm
rec
En 
proton
mn E m  m m / 2
2
mn  E m + Pm cos  m
E rec. @SK:
•Use single-ring m-like FCFV (1Rm) events
•Assume QE int. and reconstruct En
( ~50% of K2K 1Rm events are CCQE)
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n interaction (~1GeV)
Charged current quasi-elastic scat, (CCQE)
m
nm
m
pm
proton
pm : muon momentum
m : muon angle
※ En can be reconstructed
from Pm and m.
1kt : single ring m-like FCFV
SciFi: QE-like 2track
single track (proton invisible)
pion productions (nonQE)
m
nm
pm
1kt : single/multi ring FCFV
SciFi: nonQE-like 2track
m
p
nucleon
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Spectrum measurement @ND
•
•
•
1KT : Pm<1.5GeV/c, 4p acceptance
– 1-ring m-like(1Rm) fully contained
in Fid.25ton(FC) : 22,476ev.
SciFi : Pm>1GeV/c, m<60deg.
– 1-track m-like : 5963ev.
– 2-track QE-like (p<25deg.) : 764ev.
– 2-track nonQE-like (p>30deg.) : 1288ev.
PIMON
– p (p,) distribution
⇒ Neutrino Spectrum (>1GeV)
Fitting Parameters
En : 8 bins, nonQE/QE ratio
QE-like
nonQE-like
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SciFi pm/m
Pm
m
1-track
m
2-track
QE-like
2-track
nQE-like
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1kt pm/m
pm and m distributions of 1kt 1ring m-like FCFV events
m
Pm
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Allowed region (nm→nX)
Use both Number of events + Spectrum shape
(June ’99 – July ’01)
(Nov. ’99 – July ’01)
56obs ↔80.1+6.2
-5.4 exp
Null oscillation probability: less than 1%.
m2=1.5~3.9 x 10-3 eV2, sin22=1(90%CL)
reconstructed En
Allowed region
Normalized by area
Expectation
w/o oscillation
Best fit
point
2.8x10-3
Best Fit
68%
90%
99%
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Comparison w/ SK result
K2K
SK
90% C.L.
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Search for ne appearance
(K2K-I)
Search for ne appearance
Fully contained – Single ring – e-like
(ring pattern and opening angle)
Visible energy>100MeV – w/o decay electrons
data
Ring pattern
ne MC
nm MC
NC of nm MC
Opening angle
To be submitted for publication
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Data reduction summary
DATA SET: June’99 – July’01 (4.8×1019POT)
electron candidate: 1 event (obs.)
2.4 events (exp.)
DAT
A
nm
MC
beam
ne MC
signal
ne MC (CC)
sin22me=1 ,
m2=2.8x10-3eV2
FCFV
56
80
0.82
28
Single ring
32
50
0.48
20
PID (e-like)
1
2.9
0.42
18
Evis>100Me
V
1
2.6
0.41
18
w/o decay-e
1
2.0
0.35
16
NC:87% CC1p:7% CCmp:4% CCQE:2%
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Excluded region (nm→ne)
m2 (eV2)
K2K(90%CL)
SK atm.n
allowed (90%CL)
CHOOZ(90%CL)
ne disappearance
sin22me
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Near Detector Upgrade
SciBar detector
Upgrade near detector to explore low E region
(after removal of LG)
2003.10.03~
•Fine segmented scintillator
tracker
•Scintillator target & fully active
Working well !!
nm
Spec. & analysis status will be presented by
following talkers.
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Prospects
•K2K-II is running stably
━n flux in low energy region by SciBar
━SciFI n flux measurement using PID
━Improvement of Near/Far extrapolation (Harp)
━K2K events in SK-II
New results of oscillation analysis come soon !
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Summary
• K2K-I data has been analyzed so far:
– nm→nx oscillation analysis
Null oscillation prob: less than 1%
m2=1.5~3.9 x 10-3 eV2 @sin22=1(90%CL)
(consistent w/ atm. n)
– ne appearance search
1 ne candidate (consistent with BG)
• K2K-II running stably
– New near detector SciBar
– Low energy neutrino flux @ND
– K2K events in SK-II
– New results of oscillation analysis will come
soon
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supplements
Pion 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
Ring Image Gas Cherenkov Detector
(Index of Refraction is Changeable)
νμ Flux Ratio (Far/Near)
as a Function of Neutrino Energy
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 monitor
Silicon Pad
Detector Array
Segmented
Ionization Chamber
Behind beam dump
sensitive to initially high energy m (>5.5GeV)
Provide fast (spill-by-spill) monitoring of
Intensity  targeting/horn stability
Profile  beam direction
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Stability of n spectrum @ND
Neutrino spectrum measurement by the Pion monitor
Energy and angle of muons produced in the CC interactions by MRD
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ne candidate event
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Method of n flux fitting (ND)
Prepare MC templates
neutrino spectrum f (En)
and n interaction model
(QE/non-QE ratio).
En
QE(MC) non-QE(MC)
Measured (pm , m)
m
m
0
~0.5 GeV
pm
0.5
~0.75GeV
pm
Fit the parameters.
f (En) , QE/non-QE ratio …
c2=227 for 197 d.o.f.
0.75
~1.0GeV
••
• 8bins
••
• 7bins
(90 from 1kt, 137 from FGD)
for fitted (pm , m) dist. of 1KT
and FGD (124 data points)
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Contribution of sys. errors on spectrum
Spec.
nQE/QE
Spec.+nQE/QE
eSK
SK Escale
Total
F/N
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