Direct CP violation in neutral kaon decays

(1)

!"""""#$%&'())*+%,'

-.""*/ " " " "

012'"3 4 ""0'5" "26

¼

7 )

"""3"", -"""

&&8 "5""0'5","26

¼

79687

:"/ " "" " ,"";

<(" """;5

:"0'5"="3

!!!" #$%%&&'!((!

' "% ! #)"(& *(+&&)&' !(

(! , - )!&&& ! #&"( (!.& " /&

)&, 0) ))$#' 1& )!&& & (&!( . $ (0

%#&()#2(.)!&.#&"()#34455665

768' *&(! & (&!( .)%" (%#& ( 9"1(

"&%)#

¼

, :! &"& +!*! ((!!"&

#&"#&$)#&) "&%)#("(!(%

748, (' &(( #( !*/!& (&

) ( * "

¼

)!& "% !#) * $)0

#&, ;'!##)%)##!!"#&"#*

%&&!&(*0!(&.&#!&(!!"($&!

&+!, ;*$)#& !.) ((&"&#&"#

¼

< 7=8(;>?78,

$)#.'&! #&"("9"!&"

&#""&.%&((!. #(& "/& *)&' (

¼

'

(2)

7 K

cristal

~ 114 m

~ 126 m Ks tagging station

S

0 0 00 0 00 00 0 0

1 1 11 1 11 11 1 1

Proton momentum : 400 GeV/c Cycle time : 16.8 s SPS spill length : 5.2 s

(AKS)

0 00 0 00 00 0 0

1 11 1 11 11 1 1

(~ 40 m long) 6.8 cm Target

K anticounter Ks

0.6 mrad

Last collimator

Decay Region Target

Bent

~2.4 10 protons per spill 12

Muon sweeping

( ~7. 10 protons per spill)

not to scale !

L NA48 Detector

K S

K L

Drift chamber 3 Drift chamber 2

Drift chamber 1 Drift chamber 4

Hadron Muon anticounter

hodoscope Neutral

hodoscope Charged Kevlar window

Magnet

Beam pipe

window

Helium tank

9.2 m 5.4 m 7.2 m

Beam monitor

10.7 m Aluminium

2,4 m

24.1 m

34.8 m KL target

KS target 97.1 m 217.1 m

Veto counter 6 Veto counter 7

2.7 m LKr

calorimeter calorimeter

1.8 m

"5, 6" " 7 012 " 3 4

6"7"*""6;"7"," ";

3

6@

¼

6

"&$)% !!&&.&#!+!& !"% &#*.

)!&&&,

$)# ' (!.&

# *! #&')0

("!( . 55A>)& *%&&)(.645# 1%"6' '

& ( &#(!.%( %&( (!& (*&# 1%"

6'%,

(!.&(&%"&(#

.!!(! *(0

!.# ( #& )& )("!%

#

#( .(!.

$)&& &#&

#(, (##2(+!

!!)! (" (+#&'

(!.& *%( &"!

))#&"&#/%&)!&#&

,

:!.&

#&"(.#%!&)!#!#)&("

(!#&* () #%, 9"(!.) !#%! !#0

' % (&!) 6464 &). ( " !&' & "&(

!&"!

(!.&,

;%%&(&%(("!55/2)!&&)!#

&&65/2,

; %%

(!.& )& %" &"#& 4 !&'

2( !'! (/#! &"&%/0")&,

9"&!#%!%.()&%B5A>'!%.

!# #)! &# 4B !#' $ )& $!(% B

#&( &&&$)/& ! & &)C!&,

%(%%&* &, 1& 9"& !!(!

& &%&< !!(! ))& 9"(& !%( %% (&!)'

!# #")!.(!#!%.()& =BA>,;

&!( !&&& & 0"(%&.!"&)!&&&!&"!%

!/&,

;%%&!!)(&9"#&!/&' $(!&"!(

#&&9"."1(,

@54 !"#

(3)

χ ²

Weigthed events

K _L K _S

Signal region Control region

K _L candidates

K _S (norm to K _L ) + Ke3 + Kµ3 + collimator K _S (norm to K _L )

Ke3 Kµ3

collimator scattering

p _T ^/2 (GeV/c) ²

Weighted events

Signal region

-

", /

;

"

43;6"7 0

>"

43;"

6;"7

?

(!.&'## .=D655A>)&*&

& "&(, %"( $ )&

& !&"!( "&% &* %&

(#)!!(& , ; %&"

&BB!# (

/%. & 5,BE, #&&& 0)& !#)"(, ;

)%& &!(

& .9"% &"# ) #&&&& !&&

("

#&&((+!2, ;

#&&&!&"!(#

(!.&* &"**6 F>, #& &#( #

#&%!!&!!"&(&/**!!"!.445)&,

;!/%"( "#(!#& "9".#

=

(!.&( &

%.&"))&&( .9"% ((&*&* = & "(

#, #%!/%"(&# (.!&(

"##&&&

)&!, 1%"4',

;

(!.& !&"!( # !/& "&% & (

!#&'#%!1(#)((!&%#, %

&"

& B5 !# (

& 4 ##, ; / #&& & !&"!( &

#(*!!"!.4,BF>, #&% .!%((&!)*

!!"!.=55&,

%(!/%"(

(!.&!#&#G

(&&"))&&("&%

&*!&##)& (% )!&, ?

!#&

#&#)!(!.&(&C!(.!"5'&#" '

!&+! #&&(!"

1%"4'%,

?

#('

(

(&%"&( . & & $ )0

&, ?

#(' * ' .

& !&"!( ( (&

# # # %% !, 1%" 6' ( 9" & !!(!'

*4&'* #'"&(&%"&%

#

, .&#!&

(4)

$

15"6

7 15"6

7

8

*

(%%%!##%%%Æ!!.&#). %&

#!!(!#&%%%!!(!!(!*)(

#, - +!& &#( "&% $ (1! # !%( #(

(!"((&.&#!,

!!!)! ))"&()(&

(

0

#&(+'!!&((!!"(+!!!)!&0

*

(

, :&"& &

"&*%(

"&% #& ( !!"% ! #, ; )!(" *&!!/(

( &.&#! *& !!"( "&% % &&!& F 65

(!.&)#(,

&.&#! +!& !"% " ( & !"(

!# &!%

#' & %. ( (&! &!&

# #%&' %. /%# !"&&' 0. 0

%.&)&'0A"&&&%.&)&(!!(+!&("

&.#()(!(&.(+!*

(

#&,

&&!& !&"!(( !!)( &"&( (#

#"& @B#!, 6, ?%"=&"##2&&"!&

&.&#!&(!!& , & &#C&.&#!+!&

!# #!!)!(!%!/%"(,

;1 " )#(.0

&

¼

36H65I6B65

36H4465

4

*1&&)"&&!#4&#)&'&!(&&.&#!

# &&!& ! &#) "&( & &# ( ( &

!" &.&#! &, .

¼

& "!

%. *&!".!!/(( %. ()(! *&"(, &'

1(&%(!&&!. &"&#(...*6IIH (

4556,

((

¼

&)&( 1%"=%%* %(

%#" $)#&74D8'

¼

36@H6@65

, A( %0

# * $)#& ! C"(%( # 1%", $&!

(!

(!.&&"&) (') (%*.)!&"#0

., )!!. $!"(&&J& &")*/ .)&& 7B8

*!&&"#(

¼

35,

(5)

R stability against cut variations

R - R _standard (10 ^-4 ) Acceptance Accidentals Tagging Energy scale Neut. Backg.

Charg. Backg.

Beam Halo total syst. error

Estimated systematic for correction under test outgoing tracks

ingoing tracks no mom. asym. cut mom. asym. < 0.2 track radius > 20 cm γ radius > 20 cm no Ks/Kl intensity weighting no extra clusters in π ⁺ π ^- reject DCH-ovfl ± 350 ns reject DCH-ovfl ± 234 ns accept MBX dead time accept QX dead time tagging window ± 1.5 ns tagging window ± 2.5 ns τ < 2.9 τ S τ < 3.8 τ S χ ² < 9.9 χ ² < 17.1 p' _T 2 < 1.5x10 ^-4 p' _T 2 < 3.0x10 ^-4

∆M _ππ < 2 σ

∆M _ππ < 4 σ Cg < 7 cm Cg < 11.5 cm

-20 -10 0 10 20 30

NA31 E731 KTEV(96,pub.) KTEV(96-97,prel.) NA48(97-99) NA48(2001) NA48

ε , / ε

× 10 ^-4

- " " " " ,

""."5"4""4"

"" "","4"4"""

"6"7,""26

¼

76;"7

& &!##. /*' $)(%

¼

#& #$#&

"09"/)&

3665'%!#)&+! #0

' &)& K 3 64 ( K 3 =4 )& 7@8, ; 1& )

& (#(. %"! )%" )!&&( &!( .

)%",

; & )) &9" )9"/#&& ( (%

!! **'(" (&"! !*! & &&0

, ! ) 9"/ #&& & (. /* )& * !!"0

!. B A>L!

768 ( )%" !!& /* %* %(

)!&'%!"!.!#&# %0%)#$

#&("&%!&*! !!"(0)" .,

; !"$)# )!&

¼

& . "&" "

#) #F#$)#!"&"%!"&%

)& &!"& * )!", +& *(& &# M: !&

#!!!"&&((&&!.&"&7H8'#.!"&

"&%"!())$#&'& 9"!( ))$#' (

#/ )#!#)". !, ? $#)' !".(

"&

¼

% (!&&*2*&'*!

&%$)#78, (('!"

¼

# 1

&!&&&#( ( #.&#(" .%

##)& 1 &,

(6)

!

?@ '":"AB C#;, %67

?@ B AD &'6&&7

18B (CA44 ' 6&&7

?@ *B ( 67

*B E2D" &(##&867

?@ C-B5)#" )6&&&7

C-B5)#" %'F67

?F@ (+" F6&7

?@ A0D ((5E'560'G/&&&7

?8@ E( %(67

F67

?*@ 0')'0BE3)"H*

2D0B-D )"H8F

@5@ !"#