0L The K decay WLS ﬁber readout for KOTO …koto.kek.jp/pub/talks_files/2013/KAON13_Kawasaki.pdfJul. 1, 2008 “Search for the Decay K0L!!0""#”e T. Sumida 7 FIG. 1 The penguin

Jul. 1, 2008 “Search for the Decay K0L!!0""#” T. Sumida

7

FIG. 1 The penguin and box diagrams contributing to K+ ! !+"". For KL ! !0"" only the spectator quark is changed fromu to d.

The function X(xt) relevant for the top part is given by

X(xt) = X0(xt) +!s(mt)

4"X1(xt) = #X · X0(xt), #X = 0.995, (II.6)

where

X0(xt) =xt

8

!

!2 + xt

1 ! xt+

3xt ! 6

(1 ! xt)2lnxt

"

(II.7)

describes the contribution of Z0 penguin diagrams and box diagrams without the QCD corrections (Buchalla et al.,1991; Inami and Lim, 1981) and the second term stands for the QCD correction (Buchalla and Buras, 1993a,b, 1999;Misiak and Urban, 1999) with

X1(xt) = !29xt ! x2

t ! 4x3t

3(1 ! xt)2!

xt + 9x2t ! x3

t ! x4t

(1 ! xt)3lnxt

K0

K0

K0

d

d

d

!0

!0

!0

!

!

!

!

!

!

W±

Z0

W±

W± W±

W±

Z0

u,c,t

u,c,t

u,c,t

d

d

ds

s

s

l-

Vtd

The K0L!!0""# decay

• “Direct” CP violation process

• Measurement of the parameter $ in CKM

- Amplitude% A(K0

L!!0""#) ∝ A(K0!!0""#) - A(K#0!!0""#)

∝ Vtd*Vts - Vts*Vtd

= 2 x Vts x Im(Vtd) ∝ $3

11. CKM quark-mixing matrix 1

11. THE CABIBBO-KOBAYASHI-MASKAWAQUARK-MIXING MATRIX

Revised January 2004 by F.J. Gilman (Carnegie-Mellon University), K. Kleinknecht andB. Renk (Johannes-Gutenberg Universitat Mainz).

In the Standard Model with SU(2)!U(1) as the gauge group of electroweak interactions,both the quarks and leptons are assigned to be left-handed doublets and right-handedsinglets. The quark mass eigenstates are not the same as the weak eigenstates, andthe matrix relating these bases was defined for six quarks and given an explicitparametrization by Kobayashi and Maskawa [1] in 1973. This generalizes the four-quarkcase, where the matrix is described by a single parameter, the Cabibbo angle [2].

By convention, the mixing is often expressed in terms of a 3 ! 3 unitary matrix Voperating on the charge "e/3 quark mass eigenstates (d, s, and b):

!

"d !

s !

b !

#

$ =

!

"Vud Vus VubVcd Vcs VcbVtd Vts Vtb

#

$

!

"dsb

#

$ . (11.1)

The values of individual matrix elements can in principle all be determined fromweak decays of the relevant quarks, or, in some cases, from deep inelastic neutrinoscattering. Using the eight tree-level constraints discussed below together with unitarity,and assuming only three generations, the 90% confidence limits on the magnitude of theelements of the complete matrix are!

"0.9739 to 0.9751 0.221 to 0.227 0.0029 to 0.00450.221 to 0.227 0.9730 to 0.9744 0.039 to 0.0440.0048 to 0.014 0.037 to 0.043 0.9990 to 0.9992

#

$ . (11.2)

The ranges shown are for the individual matrix elements. The constraints of unitarityconnect di!erent elements, so choosing a specific value for one element restricts the rangeof others.

There are several parametrizations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix.We advocate a “standard” parametrization [3] of V that utilizes angles !12, !23, !13, anda phase, "13

V =

%c12c13 s12c13 s13e!i!13

"s12c23"c12s23s13ei!13 c12c23"s12s23s13ei!13 s23c13s12s23"c12c23s13ei!13 "c12s23"s12c23s13ei!13 c23c13

&

, (11.3)

with cij = cos !ij and sij = sin !ij for the “generation” labels i, j = 1, 2, 3. This hasdistinct advantages of interpretation, for the rotation angles are defined and labeled ina way which relate to the mixing of two specific generations and if one of these anglesvanishes, so does the mixing between those two generations; in the limit !23 = !13 = 0 thethird generation decouples, and the situation reduces to the usual Cabibbo mixing of thefirst two generations with !12 identified as the Cabibbo angle [2]. This parametrization isexact to all orders, and has four parameters; the real angles !12, !23, !13 can all be madeto lie in the first quadrant by an appropriate redefinition of quark field phases.

The matrix elements in the first row and third column, which have been directlymeasured in decay processes, are all of a simple form, and, as c13 is known to deviate from

CITATION: S. Eidelman et al., Physics Letters B592, 1 (2004)

available on the PDG WWW pages (URL: http://pdg.lbl.gov/) September 8, 2004 15:22

2 11. CKM quark-mixing matrix

unity only in the sixth decimal place, Vud = c12 , Vus = s12 , Vub = s13 e!i!13 , Vcb = s23 ,and Vtb = c23 to an excellent approximation. The phase !13 lies in the range 0 ! !13 < 2",with non-zero values breaking CP invariance for the weak interactions. The generalizationto the n generation case contains n(n " 1)/2 angles and (n " 1)(n " 2)/2 phases. Usingtree-level processes as constraints only, the matrix elements in Eq. (11.2) correspond tovalues of the sines of the angles of s12 = 0.2243 ± 0.0016, s23 = 0.0413 ± 0.0015, ands13 = 0.0037 ± 0.0005.

If we use the loop-level processes discussed below as additional constraints, the centralvalues of the sines of the angles do not change, and the CKM phase, sometimes referredto as the angle # = $3 of the unitarity triangle, is restricted to !13 = (1.05± 0.24) radians= 60o ± 14o.

Kobayashi and Maskawa [1] originally chose a parametrization involving the fourangles %1, %2, %3, and !:

!d !

s !

b !

"

=

!c1 !s1c3 !s1s3

s1c2 c1c2c3!s2s3ei! c1c2s3+s2c3ei!

s1s2 c1s2c3+c2s3ei! c1s2s3!c2c3ei!

"!d

s

b

"

, (11.4)

where ci = cos %i and si = sin %i for i = 1, 2, 3. In the limit %2 = %3 = 0, this reducesto the usual Cabibbo mixing with %1 identified (up to a sign) with the Cabibbo angle [2].Note that in this case Vub and Vtd are real and Vcb complex, illustrating a di!erentplacement of the phase than in the standard parametrization.

An approximation to the standard parametrization proposed by Wolfenstein [4]emphasizes the hierarchy in the size of the angles, s12 # s23 # s13 . Setting & $ s12 , thesine of the Cabibbo angle, one expresses the other elements in terms of powers of &:

V =

#

$1 " &2/2 & A&3(' " i()

"& 1 " &2/2 A&2

A&3(1 " ' " i() "A&2 1

%

& + O(&4) . (11.5)

with A, ', and ( real numbers that were intended to be of order unity. This approximateform is widely used, especially for B-physics, but care must be taken, especially forCP -violating e!ects in K-physics, since the phase enters Vcd and Vcs through terms thatare higher order in &. These higher order terms up to order (&5) are given in [5].

Another parametrization has been advocated [6] that arises naturally where one buildsmodels of quark masses in which initially mu = md = 0. With no phases in the thirdrow or third column, the connection between measurements of CP -violating e!ects for Bmesons and single CKM parameters is less direct than in the standard parametrization.

Di!erent parametrizations shu"e the placement of phases between particular tree andloop (e.g., neutral meson mixing) amplitudes. No physics can depend on which of theabove parametrizations (or any other) is used, as long as a single one is used consistentlyand care is taken to be sure that no other choice of phases is in conflict.

Our present knowledge of the matrix elements comes from the following sources:

September 8, 2004 15:22





!d !

s !

b !

"

=

!c1 !s1c3 !s1s3



"!d

s

b

"

, (11.4)



V =

#

$1 " &2/2 & A&3(' " i()

"& 1 " &2/2 A&2

A&3(1 " ' " i() "A&2 1

%

& + O(&4) . (11.5)





September 8, 2004 15:22





!d !

s !

b !

"

=

!c1 !s1c3 !s1s3



"!d

s

b

"

, (11.4)



V =

#

$1 " &2/2 & A&3(' " i()

"& 1 " &2/2 A&2

A&3(1 " ' " i() "A&2 1

%

& + O(&4) . (11.5)





September 8, 2004 15:22

module ID0 5 10 15 20 25 30 35 40 45 50

Ligh

t Yie

ld (p

.e./M

eV)

5

6

7

8

9

Light Yield of Common

• KL → π0νν decay• rare decay :Br=2.4x10-11 @SM• “direct” CP violating process• measure η in CKM matrix : Br(KL→π0νν)∝η2• small theoretical uncertainty (1~2%)　　　　　　　→　good probe for New Physics

Naoki Kawasaki for the KOTO collaboration, Kyoto University (Japan)

• undoped CsI • relatively large interaction length (λI =39cm )& short radiation length (X0 =1.9cm) → suppress π0 generation by halo neutron & convert 2γ from π0 decay• fast (τ~ 20ns) → can operate in high-rate condition (~ 1 MHz) • each module consists of 3 crystals with 2 types of WLS fiber readout• Individual readout : 4 fibers read singals from each crystal individually → distinguish neutron from γ using shower shape difference • Common Readout : common 28 fibers for 3 crystals → good light collection to achieve <1MeV background veto threshold

Concept of Neutron Collar Counter(NCC)

construction

• dedicated experiment for this decay mode• Uses high inteisity KL beam @ J-PARC• Detectors upgraded from E391a experiment

KOTO experiment

• To identify signal event　　　　　　　　　・2γ → CsI calorimeter　　　　　　　　　・nothing → hermetic Veto detectors

“2γ + nothing”→2γ→cannot detect

_KL→π0 νν

25201510

fiber emission

Q.E. of PMT(Bialkali)

emission of pure CsI

Q.E.(%)

wavelength(nm)

300 400 500

fiber absorption

Current status and prospect

Gamma and Neutron Counter made of undoped CsI crystals with WLS fiber readout for KOTO experiment

KL→π0νν

• Introduction

• J-PARC

• Kaon

experiments

Contents

So, ...• KOTO

• Piano

• Papionn

• Pi+KL

KOs

d

T!!

PIAn NOthino

poco a poco

Front View Side View

Beam Hole56cm

56cm45cm

γ

中性子

γ検出部中性子測定部

γ

n

Front viewSide view

γ veto part

neutron meas. part

56cm

56cm

Neutron Collar Counter(NCC) is a fully active detector made of undoped CsI with WLS fiber readout

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ID0 10 20 30 40 50

devi

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ean

0.50.6

0.7

0.8

0.91

1.1

1.2

1.3

1.41.5

front

middlerear

uniformity

peak0 1000 2000 3000 4000 5000 6000020406080

100120140160180200220

ID:16 histsame16Entries 2236Mean 2079RMS 621.8

/ ndf 2� 22.38 / 10Prob 0.01327Constant 43.8! 1261 MPV 12.3! 1802 Sigma 8.4! 188.4

ID:16

peak0 1000 2000 3000 4000 5000 60000

10

20

30

40

50

60

70

ID:17 histsame17Entries 648Mean 2409RMS 662

/ ndf 2� 11.46 / 12Prob 0.4898Constant 25.4! 376.5 MPV 17.1! 2120 Sigma 12.0! 165.2

ID:17

peak0 1000 2000 3000 4000 5000 600002040

6080

100120

140160



ID:18

peak0 1000 2000 3000 4000 5000 60000

51015

202530

3540



ID:19

peak0 1000 2000 3000 4000 5000 60000

50

100

150

200

250

ID:20 histsame20Entries 2340Mean 2219RMS 592


ID:20

peak0 1000 2000 3000 4000 5000 600001020304050607080



ID:21

peak0 1000 2000 3000 4000 5000 6000020406080

100120140160



ID:22

peak0 1000 2000 3000 4000 5000 60000

10

20

30

40

50



ID:23

peak0 1000 2000 3000 4000 5000 60000

50

100

150

200

250



ID:24

peak0 1000 2000 3000 4000 5000 60000

1020

304050

6070

80



ID:25

peak0 1000 2000 3000 4000 5000 600002040

6080

100120

140160



ID:26

peak0 1000 2000 3000 4000 5000 60000

510152025303540



ID:27

peak0 1000 2000 3000 4000 5000 60000

50

100

150

200

250ID:28 histsame28

Entries 2236Mean 2271RMS 627.2


ID:28

peak0 1000 2000 3000 4000 5000 60000

10

20

30

40

50

60

70



ID:29

peak0 1000 2000 3000 4000 5000 60000

20

40

60

80

100

120

140


/ ndf 2� 16.78 / 10Prob 0.07948Constant 36.6! 793.4 MPV 14.2! 1982 Sigma 9.7! 170

ID:30

peak0 1000 2000 3000 4000 5000 60000

5

10

15

20

25

30


/ ndf 2� 6.096 / 11Prob 0.8669Constant 17.5! 182.4 MPV 25.6! 1885 Sigma 16.0! 156

ID:31

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X(mm)

Y(mm)

cosmic ray track• light yield for common: > 4.5 p.e./MeV• light yield uniformity of common readout between Front,Middle,and Rear : < 20%• cross talk of individual readout between Front , Middle , and Rear : << 1%• energy calibration : < 1% error

detector calibration & performance check have beed done with cosmic ray data

→ good performance as a photon veto detector !!

detector construction : from Apr. 2012 to Nov. 2012 @ Kyoto Univ.

Detector installed @ J-PARC Dec. 2012 → successfully finished (All channels are working well !!)

First trial data for halo neutron measurement were taken in January. Analysis is ongoing

hist26Entries 1505Mean 2.564e+04RMS 7455

IntegratedADC of Common 010000 20000 30000 40000 500000

20

40

60

80

100

120

140hist26

Entries 1505Mean 2.564e+04RMS 7455

NCC_Common

ADC count

ADC spectrum of cosmic ray data

fitting with landau distribution (peak corresponds to~38MeV)

detector3

OK Tν

νs

d

Kuraray PMP fiber matches CsI emission spectrum & Q.E. of PMT

module production

module stacking

install into KOTO detector

PMTFront7cm Middle Rear15cm 20cm 10cm

MAPMT

Individual

common

cutaway side view

IndividualCommon

top view

Concept of n/γ discrimination

→ NCC : upstream veto near the beam

• Front, Middle, and Rear crystals are optically separated with aluminum mirrors

• Modules are optically separated with Teflon wrapping

• Fiber masking with black paint for optical separation

black paint

• Neutrons existing around the KL beam(halo neutron)interact with NCC , generate π0s , and π0→2γevents become background

haloneutron γπ0

νν

KL NCC

π0

γ

γ

γmain calorimeter

Halo neutron background

• countermeasures for halo neutron BG• detect π0 generated event and veto → background reduction• measure the amount of halo-n & energy spectrum → background estimation

Documents

0L The K decay WLS ﬁber readout for KOTO …koto.kek.jp/pub/talks_files/2013/KAON13_Kawasaki.pdfJul. 1, 2008 “Search for the Decay K0L!!0""#”e T. Sumida 7 FIG. 1 The penguin