Post on 21-Aug-2020
Precision Measurement of
Γ (Ke2)/Γ (Kµ2) Ratio
Using
Stopped Positive Kaons
at J-PARC
S. Shimizu
Osaka university
for the TREK collaboration
July 28, 2011
S. Shimizu (suguru@phys.sci.osaka-u.ac.jp) PANIC2011, MIT, July 28, 2011
OUTLINE
� Lepton Flavor Universality Test in K+ �l+ ν (Kl2)
� Physics motivation
� Experimental method
� Detector
� Monte Carlo simulation
� Sensitivity
� Schedule
� Summary
S. Shimizu (suguru@phys.sci.osaka-u.ac.jp) PANIC2011, MIT, July 28, 2011
Lepton universality in Kl2 and ππππl2 decays .
Standard Model:
� By forming ratio of the Γ(Ke2) to the Γ(Kµ2),
hadronic form factors are cancelled out and
the RKSM is highly precise.
� Strong helicity suppression of the electronic
channel enhances sensitivity to effects
beyond the SM.
Uncertainty is ∆RK/RK ~ 0.05%
Helicity suppression
due to V−A structure
Radiative correction
due to the Internal
bremss. part of the
K�lνγ process
RKSM= ( 2.477±0.001)x 10−5
RπSM= (12.352±0.001)x 10−5
K+
s
u
W
-
e+
νe
,µ+
,νµ
PL99(2007)231801
Kl2 decays beyond the SM
Contribution from MSSM
A charged Higgs-mediated SUSY LFV contribution, can
be strongly enhanced by emitting a τ neutrino.
Using
∆13=5x10−4, tanβ=40, MH=500GeV/c2
RKLFV=RK
SM(1±0.013)
PRD74(2005)11701
K+
s
u
H+
(Higgs)
∆13
~
-
ν
(Slepton)
(Sneutrino)
~
e+
ντ
B~
(Bino)
0
10
20
30
40
50
60
70
80
90
100 200 300 400 500 600 700 800 9001000
MH (GeV/c
2)
tan
βblack:red :blue :
∆=1 x10-4
∆=5 x10-4
∆=1 x10-3
allowed
excluded
Kl2 decays beyond the SM
Contribution from MSSM
A charged Higgs-mediated SUSY LFV contribution, can
be strongly enhanced by emitting a τ neutrino.
Using
∆13=5x10−4, tanβ=40, MH=500GeV/c2
RKLFV=RK
SM(1±0.013)
Important!
PRD74(2005)11701
K+
s
u
H+
(Higgs)
∆13
~
-
ν
(Slepton)
(Sneutrino)
~
e+
ντ
B~
(Bino)
0
10
20
30
40
50
60
70
80
90
100 200 300 400 500 600 700 800 9001000
MH (GeV/c
2)
tan
βblack:red :blue :
∆=1 x10-4
∆=5 x10-4
∆=1 x10-3
allowed
excluded
Kl2 decays beyond the SM
Contribution from MSSM
A charged Higgs-mediated SUSY LFV contribution, can
be strongly enhanced by emitting a τ neutrino.
Using
∆13=5x10−4, tanβ=40, MH=500GeV/c2
RKLFV=RK
SM(1±0.013)
Important!
Analogous SUSY effect in
π decay is suppressed by
a factor (mπ/MK)4.
PRD74(2005)11701
K+
s
u
H+
(Higgs)
∆13
~
-
ν
(Slepton)
(Sneutrino)
~
e+
ντ
B~
(Bino)
0
10
20
30
40
50
60
70
80
90
100 200 300 400 500 600 700 800 9001000
MH (GeV/c
2)
tan
βblack:red :blue :
∆=1 x10-4
∆=5 x10-4
∆=1 x10-3
allowed
excluded
Experimental status
Previous experiment (in-flight K method)
� KLOE
RK=(2.493±0.025±0.019)x10−5
� NA62
RK=(2.487±0.011±0.007)x10−5
� Error weighted average
RK=(2.488±0.012)x10−5
∆RK/RK=0.5%
Deviation from the SM at 0.9σ level.
Eur.Phys.J.C64(2009)627
Strong motivation to perform the RK exp. with an accuracy of
∆RK/RK=0.2% at J-PARC comes to our mind.
arXiv:hepex1008.1219
2.4
2.42
2.44
2.46
2.48
2.5
2.52
2.54
2.56
2.58
2.6
2007 2008 2009 2010 2011 2012 2013
Year
RK
(x
10-5
)
PDG
KLOE
NA62Avr.
SM
Experimental setup (upgrade of the E246 system)
� Stopped K+ decay
� K1.1BR beamline will be used.
� momentum measurement
SC Toroidal spectrometer
� e+,µ+ identification
TOF and Cherenkov
� γ measurement :CsI(Tl)
� µ+ polarimeter
0
f
o
r
w
a
r
d
0
b
a
c
k
w
a
r
d
A = NCW - NCCW
NCW + NCCW COILGAP
IRON POLE
+ STOPPER
e+ COUNTER
TARGET
CsI(Tl)
End View
π
µ
π
0
.
5 1
M
C
r
y
o
s
t
a
t
Iron Pole
L
e
a
d
S
h
i
e
l
d
+
C
2
C
3
C
4
T
O
F2
M
u
o
n
D
e
g
r
a
d
e
r
Muon Stopper
e+
C
o
u
n
t
e
r
T
a
r
g
e
t
F
i
b
e
r
TOF1, Aerogel Cherenkov
D
e
g
r
a
d
e
r
B
0
K+
C
h
e
r
e
n
k
o
v
C
1
C
s
I
(
T
l
)
0 0.5 1.0 m
Side View
µe+
γ
GP Counter
Experimental setup (newly made)
� C1 GEM
� Aerogel Cherenkov
� TOF
� CsI(Tl) readout
0
f
o
r
w
a
r
d
0
b
a
c
k
w
a
r
d
A = NCW - NCCW
NCW + NCCW COILGAP
IRON POLE
+ STOPPER
e+ COUNTER
TARGET
CsI(Tl)
End View
π
µ
π
0
.
5 1
M
C
r
y
o
s
t
a
t
Iron Pole
L
e
a
d
S
h
i
e
l
d
+
C
2
C
3
C
4
T
O
F2
M
u
o
n
D
e
g
r
a
d
e
r
Muon Stopper
e+
C
o
u
n
t
e
r
T
a
r
g
e
t
F
i
b
e
r
TOF1, Aerogel Cherenkov
D
e
g
r
a
d
e
r
B
0
K+
C
h
e
r
e
n
k
o
v
C
1
C
s
I
(
T
l
)
0 0.5 1.0 m
Side View
µe+
γ
GP Counter
Experimental setup (newly made)
� C1 GEM
� Aerogel Cherenkov
� TOF
� CsI(Tl) readout
0
f
o
r
w
a
r
d
0
b
a
c
k
w
a
r
d
A = NCW - NCCW
NCW + NCCW COILGAP
IRON POLE
+ STOPPER
e+ COUNTER
TARGET
CsI(Tl)
End View
π
µ
π
0
.
5 1
M
C
r
y
o
s
t
a
t
Iron Pole
L
e
a
d
S
h
i
e
l
d
+
C
2
C
3
C
4
T
O
F2
M
u
o
n
D
e
g
r
a
d
e
r
Muon Stopper
e+
C
o
u
n
t
e
r
T
a
r
g
e
t
F
i
b
e
r
TOF1, Aerogel Cherenkov
D
e
g
r
a
d
e
r
B
0
K+
C
h
e
r
e
n
k
o
v
C
1
C
s
I
(
T
l
)
0 0.5 1.0 m
Side View
µe+
γ
GP Counter
Experimental setup (newly made)
� C1 GEM
� Aerogel Cherenkov
� TOF
� CsI(Tl) readout
0
f
o
r
w
a
r
d
0
b
a
c
k
w
a
r
d
A = NCW - NCCW
NCW + NCCW COILGAP
IRON POLE
+ STOPPER
e+ COUNTER
TARGET
CsI(Tl)
End View
π
µ
π
0
.
5 1
M
C
r
y
o
s
t
a
t
Iron Pole
L
e
a
d
S
h
i
e
l
d
+
C
2
C
3
C
4
T
O
F2
M
u
o
n
D
e
g
r
a
d
e
r
Muon Stopper
e+
C
o
u
n
t
e
r
T
a
r
g
e
t
F
i
b
e
r
TOF1, Aerogel Cherenkov
D
e
g
r
a
d
e
r
B
0
K+
C
h
e
r
e
n
k
o
v
C
1
C
s
I
(
T
l
)
0 0.5 1.0 m
Side View
µe+
γ
GP Counter
Experimental setup (newly made)
� C1 GEM
� Aerogel Cherenkov
� TOF
� CsI(Tl) readout
0
f
o
r
w
a
r
d
0
b
a
c
k
w
a
r
d
A = NCW - NCCW
NCW + NCCW COILGAP
IRON POLE
+ STOPPER
e+ COUNTER
TARGET
CsI(Tl)
End View
π
µ
π
0
.
5 1
M
C
r
y
o
s
t
a
t
Iron Pole
L
e
a
d
S
h
i
e
l
d
+
C
2
C
3
C
4
T
O
F2
M
u
o
n
D
e
g
r
a
d
e
r
Muon Stopper
e+
C
o
u
n
t
e
r
T
a
r
g
e
t
F
i
b
e
r
TOF1, Aerogel Cherenkov
D
e
g
r
a
d
e
r
B
0
K+
C
h
e
r
e
n
k
o
v
C
1
C
s
I
(
T
l
)
0 0.5 1.0 m
Side View
µe+
γ
GP Counter
Overview of the measurement
Number of accepted events
RK is basically obtained as,
N(Ke2)= N(Ke2) + N(Ke2γ)
N(Kµ2)= N(Kµ2) + N(Kµ2γ)
Requirement
� Momentum measurement
by the spectrometer
P(e)>Pmax(Ke3)=228MeV/c
� Particle identification by TOF
and Cherenkov
� N(γ) = 0 or 1
Exp.
data
MC
data
0γ 1γ
µ+e+ µ+e+
D0e D1e D0µ D1µ
~
~
~~
~
~
~
~~~
~~~ ~
~
~
e/µµµµ identification
� TOF
Time of flight measurement between TOF1 and TOF2
� e+ trigger counter by aerogel Cherenkov detector.
β(Ke2 e+) ~1
β(Kµ2 µ+) ~ 0.92=1/1.087
Estimated eff.= 99.2 ± 0.2%
PID performance and detector efficiency will be directly
measured by using the experimental data.
⊗ beambeamTarget
n=1.05
Fresnel mirror
A.Toyoda et. al.
Expected spectra obtained by MC
(1) Ke2 with and without external bremss. photon
(2) Kµ2
(3) Radiative Kl2 decays
CsI(Tl)
target
e+external
bremss. γ
IB γ
SD γ
µ+
0
500
1000
1500
2000
2500
100 150 200 250
e+ momentum (MeV/c)
counts
/bin
0
0.05
0.1
0.15
0.2
0.25
0.3
0 2 4 6
target path length (cm)
Bre
mss. pro
b.
1
10
102
103
0 20 40
E γ (MeV)
counts
/bin
1
10
102
103
0 5 10 15 20
θ γ (deg)
counts
/bin
(d) (c)
(b) (a)
Expected spectra obtained by MC
(1) Ke2 with and without external bremss. photon
(2) Kµ2
(3) Radiative Kl2 decays
CsI(Tl)
target
e+external
bremss. γ
IB γ
SD γ
µ+
0
500
1000
1500
2000
2500
3000
3500
100 120 140 160 180 200 220 240 260
µ+ momentum (MeV/c)
co
un
ts/b
in
µ+ momentum and polarization
will be measured.
Expected spectra obtained by MC
(1) Ke2 with and without external bremss. photon
(2) Kµ2
(3) Radiative Kl2 decays
CsI(Tl)
target
e+external
bremss. γ
IB γ
SD γ
µ+
Black: Structure dependent
Red: Internal bremss.
0
50
100
150
200
250
100 150 200 250
e+ momentum (MeV/c)
co
un
ts/b
in
(a)
0
25
50
75
100
125
150
175
200
225
0 50 100 150
θγ (deg)
co
un
ts/b
in(b)
0
10
20
30
40
50
60
0 50 100 150 200 250
Eγ (MeV)
co
un
ts/b
in
(c)
0
20
40
60
80
100
120
140
160
180
0 50 100 150 200 250
Eγ (MeV)
θ γ (
de
g)
(d)
Momentum 800 MeV/c
Momentum bite ±3%
Acceptance 4.5 msr % ∆p/p
K+ intensity 2 ×105 /s
K/π ratio > 2
Beam spot 1.0 ×1.0 cm
(FWHM)
Final focus achromatic
K0.8 ( K1.1-BR)
K1.1
K0
.8
proton
K1.1/ K0.8
(S-type)
K0.8/ K1.1
(C-type)
KLHigh-p
Final Focus
Single stage DC separator
Vertical focuses before and
after the separator
Horizontal focus just after
the second D-magnet
Beamline for K+ extraction
K+
S. Shimizu (suguru@phys.sci.osaka-u.ac.jp) PANIC2011, MIT, July 28, 2011
S. Shimizu (suguru@phys.sci.osaka-u.ac.jp) PANIC2011, MIT, July 28, 2011
Sensitivity estimation of RK
∆RK/RK=0.2%Statistical error
3x1050.07Detector acc.
4x1061.55x 10−5Branching ratio of Ke2
Statistics
3x10110.25Kaon stopping eff.
1x10121500kW・day
(= 30kW・50days)
Beam
source ∆RK/RK
Detector acceptance 0.05%
PID performance 0.11%
Background 0.04%
Total systematic error 0.13%
Statistical sensitivity
Systematic errors
2.4
2.42
2.44
2.46
2.48
2.5
2.52
2.54
2.56
2.58
2.6
2007 2008 2009 2010 2011 2012 2013
Year
RK
(x
10-5
)
PDG
KLOE
NA62TREKAvr.
SM
Summary of systematic uncertainties
We estimated the systematic uncertainty to be ∆RK/RK=0.13%
∆RK=0.003 x 10-5
∆RK=0.005 x 10-5
� Since the J-PARC facility was seriously damage by the earthquake, it is very
difficulty to say accurate schedule.
� According to the J-PARC director, the delay is estimated to be 1 year.
Schedule
Collaboration
� Canada U. Saskatchewan
TRIUMF
UBC
U. Montreal
U. Manitoba
� USA Hampton U.
MIT
U. South Carolina
Iowa State U.
� Russia INR
� Vietnam National Science U.
� Japan KEK
Tohoku U.
Osaka U.
TITech
U. of Tokyo
� Beamline
� Target
� Cherenkov and TOF
� CsI(Tl) readout
� γ detectors
� DAQ
� GEM chambers
� Tracking upgrade
S. Shimizu (suguru@phys.sci.osaka-u.ac.jp) PANIC2011, MIT, July 28, 2011
Summary
� RK is a very sensitive prove of SUSY LFV contribution, which
can be strongly enhanced by emitting a τ neutrino.
� We propose a J-PARC experiment with low-intensity beam
such as during the 30kW operation to pursue
∆RK/RK =0.2%
� We will use K1.1BR beamline.
� The experiment will be performed using upgraded E246
detector (a part of TREK detector)
� The proposed experiment can be done on our way to the final
TREK configuration.
S. Shimizu (suguru@phys.sci.osaka-u.ac.jp) PANIC2011, MIT, July 28, 2011
Backup Slides
Overview of the measurementNumber of accepted events
RK is basically obtained as,
N(Ke2)= N(Ke2) + N(Ke2g)
N(Kµ2)= N(Kµ2) + N(Kµ2γ)~
~~~
~
~
~
~~~
~~
� Most of the systematic effects are reduced by forming the ratio of N(Ke2) and N(Kµ2) and their acceptances.
� Several items will not be cancelled out perfectly, which introduces a systematic error in the RK measurement.
� Dominant contributions to the RK uncertainties can be considered as three groups: [G1]. Misunderstanding of the detector acceptances[G2]. Imperfect PID performance [G3]. Background contaminations
� Comparison of various Ke2 and Kµ2 spectra with the MC.� Ke3, Kµ3, and Kπ2 spectra are also compared with the MC.
� These studies have already been performed in the E246/470 experiment with the level of 1%.
� This uncertainty should be improved with increasing the numbers of Ke3, Kµ3, and Kπ2 up to 106 level, which is 100 times higher statistics than E246/470.
� We aim at achieving this uncertainty better than∆RK/RK<0.1%
PL B513(2001)311
PL B495(2000)33
[G1] Imperfect reproducibility of the experimental spectra
solid: exp.dotted: MC
Kµ3
Kπ2Kπ2
Kµ3
Ke3Ke3
E246/470 data
χ2=1.07χ2=0.96
χ2=1.12 χ2=0.94
χ2=1.10 χ2=1.07
[G1] High energy external bremss. emission� The probability of the bremsstrahlung
emission is proportional to the flight path in the target .
� Uncertainty of the path length in the target of σ=1.4 mm introduces the systematic uncertainty.∆RK/RK=0.02%
� Also, offset of the path length distribution is taken into account.
target
high energy
ext. bremss. γ
e+
e+ momentum
Ke2Ke3 endpoint
[G1] Effect from efficiency difference between e+s and µ+s for particle trackers
� The efficiencies are directly measured by using experimental data.
� By changing spectrometer field, sufficient Ke3 and Kµ3 events are collected within one hour.
� Particle identification will be performed by the AC counter and the TOF system.
� From the statistical uncertainty of the efficiency measurement,
∆RK/RK=0.035%
C1
spectrometerC4
C3
C2
AC
TOF2
[G1] Misunderstanding of the SD component in D0
� SD measurement using 1 gamma events. � Statistical error for the subtraction of the SD component is
adopted as the systematic uncertainty.∆RK/RK=0.036%
CsI(Tl)
target
e+
external bremss. γ
IB γ
SD γ
IB:Internal bremss. part
of the K�lνγ process
SD: Structure dependent
part of the K�lνγ process
0
50
100
150
200
250
100 150 200 250
e+ momentum (MeV/c)
co
un
ts/b
in
(a)
0
25
50
75
100
125
150
175
200
225
0 50 100 150
θγ (deg)
co
un
ts/b
in
(b)
0
10
20
30
40
50
60
0 50 100 150 200 250
Eγ (MeV)
co
un
ts/b
in
(c)
0
20
40
60
80
100
120
140
160
180
0 50 100 150 200 250
Eγ (MeV)
θ γ (
de
g)
(d)
Black: SD
Red: IB
[G2] Effects from particle mis-identification by TOF and AC
� Direct measurement of the mis-identification probability with the help of an additional Pb-glass Cherenkov counter.
� Particle identification is performed using two of the three and signal in the other detector is checked.
� Statistical error of this measurement is adopted as a systematic uncertainty of the mis-identification effect.
∆RK/RK=0.035% (I)AC
(III)PGC
(II)TOF
[G2] Events with in-flight µ+ decay (µ+�e+νν) from Kµ2
� We can put AC counter as close as possible to the K+ stopper.
� Uncertainty of muon decay inside the AC introduces∆RK/RK=0.025%
[G2] e± creation from a radiated photon in Kµ2γ decay
� Kµ2γ events with e± generation through electro-magnetic interaction in the target would be mis-identified as Ke2
� Charged particle mass from the TOF measurement has muon rest mass. ∆RK/RK=0.02%
target
eKµ2γ µ
+
AC
γ
e± production prob. Eγ in Kµ2γ
[G3] Mis-identification of beam particles hitting to the CsI(Tl) calorimeter as photons from the target.
� Beam particle hitting the calorimeter can be mis-identified as γ.� However, these backgrounds are accidental events, and they
are common for Ke2 and Kµ2.� Taking into account realistic K+ intensity, π/K ratio, and duty
factor, the event loss probability is assumed to be 5% in the TREK experiment.
� Event loss by these backgrounds is regarded as uncertainty from this effect. ∆RK/RK=0.04%
[G3] Mis-identification of beam π+ as e+ by the aerogelCherenkov counter.
� π+ particles in the beam can generate signals in the AC counter and are identified as e+.
� B0 counter rejection (99%) for incident particles during K+
decay. π/K ratio is assumed to be <1.� Charged particle mass from the TOF measurement has muon
rest mass. ∆RK/RK=0.002% <0.01%
External bremss. distribution in E470
C3 C4
CsI(Tl)Calorimeter
IronPole
K+
CerenkovCounter
Lead Shield
C2
TOF2
0 0.5 1m
Target
TOF1
µ+
µ+
Pb-plastic Detecto r
GEMe+
e+
External bremss. distribution in E470 (2)
-1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
-100 0 100
θ e+
GPcos
(a)
-1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
-100 0 100
cos
γ m
ax
(b)
(deg) θ e+
GP (deg)
θ G
P
γ m
ax
θ G
P
exp. MC
Property of SD and IB
CsI(Tl)
target
e+external
bremss. γ
IB γ
SD γ
µ+
SD/IB spectra for Kl2g D1
0
50
100
150
200
250
300
210 220 230 240 250
µ+ momentum (MeV/c)
counts
/bin
0
10
20
30
40
50
60
0 50 100 150
θγ (deg)
counts
/bin
0
5
10
15
20
25
30
0 50 100 150 200 250
Eγ (MeV)
counts
/bin
(c)
0
20
40
60
80
100
120
140
160
180
0 50 100 150 200 250
Eγ (MeV)
θγ (
deg)
(d)
(a) (b)
0
50
100
150
200
250
100 150 200 250
e+ Momentum (MeV/c)
coun
ts/b
in
(a)
0
25
50
75
100
125
150
175
200
225
0 50 100 150
θγ (deg)
coun
ts/b
in
(b)
0
10
20
30
40
50
60
0 50 100 150 200 250
Eγ (MeV)
coun
ts/b
in(c)
0
20
40
60
80
100
120
140
160
180
0 50 100 150 200 250
Eγ (MeV)
θ γ (de
g)
(d)
Km2g SD/IB D1 sample Ke2g SD/IB D1 sample
SD/IB spectra (2) Up:e+, Dn:µ+
0
100
200
300
400
500
600
700
800
100 150 200 250
(a)
e+ momentum (MeV/c)
coun
ts/b
in
0
200
400
600
800
1000
1200
1400
1600
1800
0 10 20 30 40
(b)
Eγ (MeV)
coun
ts/b
in
0
200
400
600
800
1000
1200
1400
1600
100 150 200 250
(c)
µ+ momentum (MeV/c)
coun
ts/b
in
0
500
1000
1500
2000
2500
0 10 20 30 40
Eγ (MeV)
coun
ts/b
in
(d)
0
20
40
60
80
100
120
150 175 200 225 250
Pe+ (MeV)
coun
ts/b
in
(a)
0
5
10
15
20
25
30
0 50 100 150 200 250
Eγ (MeV)
coun
ts/b
in
(b)
0
5
10
15
20
25
30
35
150 175 200 225 250
Pµ+ (MeV)
coun
ts/b
in
(c)
0
2
4
6
8
10
12
0 50 100 150 200 250
Eγ (MeV)
coun
ts/b
in
(d)
SD for Kl2g
Black:D1
Red: D0
IB for Kl2g
Summary of RK exp
Check the validity of simulation
We confirmed with use of K+→π+π0 decay.
χ2 = 114/107 χ2 = 183/191
π + (MeV/
co
un
ts /
bin
co
un
ts /
bin
cos θπ+π
0
(b)(a)
momentum c)
Exp.
MC
Exp.
MC
Reproducibility of Charged particle
• black line : experimental data
• red line: MC
co
un
ts /
bin
C2Z (cm)
C4R (cm)
Target Z (cm)
C3R (cm)
co
un
ts /
bin
co
un
ts /
bin
co
un
ts /
bin
(c)
(b)(a)
(d)
counts
/ b
in
Tracking
Target distance (cm)
Ring distance (cm)χ 2
counts
/ b
in
counts
/ b
in
(a) (b)
(c)
hit position in tracking elementstracking status
K+→π+π0 decay.
γ and π0 reproducibility
• black line : experimental data
• red line: MC
(MeV)
counts
/ b
in
ME
E1 2
E
γγ γγ
γγ
(MeV)(MeV)
(MeV)
(a)
(c)
(b)
(d)
counts
/ b
incounts
/ b
in
counts
/ b
in cos θπ+π
0
counts
/ b
in
cos θ γγ
(a) (b)
counts
/ b
in
K+→π+π0 decay.
Ke3 and Kµ3 spectra
• black line : experimental data
• red line: MC
C4R<105 cm 105<C4R<115 cm
115<C4R<125 cm 125<C4R cm
(a)
co
un
ts /
bin
x 10 3
M (MeV 4 2
c ) / 2
TOF
(b)
co
un
ts /
bin
x 10 3
M (MeV 4 2
c ) / 2
TOF
(c)
co
un
ts /
bin
x 10 3
M (MeV 4 2
c ) / 2
TOF
(d)
co
un
ts /
bin
x 10 3
M (MeV 4 2
c ) / 2
TOF
(deg)θ π
(a)
co
un
ts /
bin
µ
(b)
P (MeV/c)µ
co
un
ts /
bin
(d)
co
un
ts /
bin
P (MeV/c)e
(c)
θeπ
co
un
ts /
bin
(deg)
Kµ3
Ke3
TOF spectra gated C4R
e
µ
Measurement of Γ（Kμ3）/Γ（Ke3) ratio
• Physics motivation
� Evaluation of ChPT theory
� µ-e universality
• Measurement
co
un
ts /
bi
n
x 10 3
µ
+
+
e
M (MeV 4 2
c ) / 2
TOF
Exp MC
K. Horie et al.
Phys. Lett. B513(2001)311
Basic method is
similar to Γ(Kµ2)/Γ(Ke2)
Spectroscopy of
Ke3 decay
Spectroscopy of
K+� e+π0π0ν
BR=3x10-5 ~ BR(Ke2)-1 -0.5 0 0.5 1
cos θ π0 π
0
counts
/bin
counts
/bin
counts
/bin
0
20
40
0
20
40
-0.5 0 0.5
q2/(4 m
π 2)
Spectroscopy of
K+�π+π0γ
treatment
for both of IB and SD
(MeV/c)pπcos πθ
cos πθ E (MeV)
+
0
+
γ 3γ
3
γ 3
counts
/ b
incounts
/ b
in
counts
/ b
incounts
/ b
in
Exp
MC
MC DE
Exp Exp
Exp
MC
MC DE
MC
MC DE
MC
MC DE
Spectroscopy of K+�π0µ+γν
radiative decay
J-PARC K1.1BR beamline
� The beamline K1.1BR was completed in summer 2010.
� The beam tuning was carried out in Oct. and Nov. 2010 by the TREK group.
� A reasonable K+ intensity with fairly well π/K ratio ~1 could be confirmed.
� There might be still room for improvement.
� However, a better π/K ratio (~0.3) can be only achieved by upgrading
electro-static separator.
charge exchange reaction K+ � K0
• cross section of K+ � K0 is ~ 5mb• considering degrader (BeO) length , reaction
probability is • rou/A x 6*1023 *30 x sigma
= 3/25x6*1023 x 30 x 5*10-27 =0.01