CP�AND�T� CP�AND�T� M.S.�Sozzi M.S.�Sozzi VIOLATION VIOLATION University�of�Pisa University�of�Pisa WITH�K�MESONS WITH�K�MESONS August 30 th , 2007 - Time and Matter 2007 - Bled, Slovenia
Outline • Introduction� • Direct�CP�violation • Indirect�CP�violation • CPV�in�charged�K�decays • T�violation Some�byproducts • The�future • Conclusions TAM07 CP/T violation with K M. S. Sozzi
Of�Kaons,�Flavour and�CP�violation Kaons:�the�lightest�kind�of�flavoured matter • The�birth�of�the�flavour physics�puzzle • The�first�failure�of�a�discrete�symmetry • The�matter"antimatter�asymmetry A�large�and�significant�part�of�particle�physics… TAM07 CP/T violation with K M. S. Sozzi
CP�violation The�“C” requires�HEP� experiments The�smallest� symmetry�violation A�necessary�ingredient� for�baryogenesis Linked�to�flavour (at�least�in�the�SM) Must�be�present�in�New�Physics TAM07 CP/T violation with K M. S. Sozzi
CP�and�T�violation Even�more�intriguing� and�mysterious: the�interplay�of�CP�and�T� through�the�“rock"solid” (?)� CPT�theorem TAM07 CP/T violation with K M. S. Sozzi
Kaons as�the� minimal�flavour laboratory Kaons remain�a�privileged�observatory for�flavour physics�phenomena • All the�features�of�flavour physics�are� present�(i.e.�all�kinds�of�CP�violation�– of�same�size�as�in�B) • Very� simple (minimal)�system • Very�nicely� accessible experimentally • Very� hard for�theorists… TAM07 CP/T violation with K M. S. Sozzi
Searching�for�CP/T�violation�with�K Transitions�among�CP�eigenstates with�opposite� K 2 → ππ �� eigenvalues ��� Search�for�physical�states�not�being�CP� K L → ππ �� eigenstates (non"exponential�decay�of�CP� and ��� eigenstates) K s → πππ Differences�in�the�partial�decay�widths�or�decay� ∆g(K → 3π) ��� ��� properties�of�particles�and�antiparticles Test�of�time"reversibility P(K 0 → K 0 )�≠ P(K 0 → K 0 ) � Measure�of�non"zero�T"odd�quantities P T (K 53 ) Triple�prod. TAM07 CP/T violation with K M. S. Sozzi
CPV:�the�long�hiatus Despite�great�efforts:� no�news�on�CP�violation�for�36�years… The�long"standing�superweak scenario “At�present�our�experimental� understanding�of�CP�violation�can�be� K 0 K 0 summarized�by�the�statement�of�a� single�number”.�(J.�Cronin,�10.12.1980) G SW ≈ 10 "7 G F Is�CP�violation�an�intrinsic�property� of�weak�interactions,�or�is�it�rather� a�peculiar�effect�linked�to�quasi" degenerate�state�mixing? TAM07 CP/T violation with K M. S. Sozzi
Direct�and�indirect�CPV�in�SM Indirect CP�violation� (K 0 "K 0 mixing):� ε ≈ 2.2� ⋅ 10 –3 Direct CP�violation� (decay):� ε ’ Could be superweak Cannot be superweak K L ∝ K 2 +�ε K 1 K L ∝ K 2 +�ε K 1 ππ ππ TAM07 CP/T violation with K M. S. Sozzi
�� The�quest�for�direct�CPV ��� The�search�for�direct�CP�violation�(CPV�in�the�K → 2π decay�amplitude):�a�long�series�of�precision�counting� experiments�(the�only�working�approach�so�far) 2 η + − Γ → π π Γ → π π 0 0 ( ) ( K ) K = = − ε ε 00 L S 1 6 Re( ' / ) + − Γ → π π Γ → π π 2 0 0 η ( K ) ( K ) + − S L The�(inconclusive)�legacy�of�the� NA31�(CERN)�and�E731�(FNAL)�experiments The�whole�of�K�physics�in�the�last�decade� spun�off�from�this�central�experimental�program TAM07 CP/T violation with K M. S. Sozzi
KTeV at�Fermilab �� ��� Main�Injector�(120�GeV)�p Double�K L beam�(<p>=70�GeV/c) Regenerated�K S Pure�CsI calorimeter Data�taking�in�1997�and�1999 100�physicists,�12�USA/Japan� institutions TAM07 CP/T violation with K M. S. Sozzi
NA48�at�CERN �� ��� SPS�(450�GeV)�p K S and�K L beams�(<p>=100�GeV/c) K S tagging�by�time"of"flight Liquid�Krypton�calorimeter Data"taking�1998"1999"2001 130�physicists,�16�European�institutions TAM07 CP/T violation with K M. S. Sozzi
�� Direct�CP�violation:� ε ε ’/ ε ��� ε ε ε ε ε 1999:�proof�of�direct�CP�violation�(after�36�years!)�at�>7� σ Re( ε ε ’/ ε ε )�=� (16.3± 2.2)�W 10 "4 World�average: ε ε ε ε NA48 (1997"2001):�final�result Re( ε ε ’/ ε ε ) ε ε ε ε KTeV (1997"1999):�½ statistics�(1997) χ 2 =6.2/3,�consistency�10% Room�for�improvement�(…)� 2005�EPS�Prize�to�the� NA31�collaboration 2007�APS�Panofsky Prize�to� Italo Mannelli (Pisa),�Heinrich�Wahl�(CERN)� and�Bruce�Winstein (Chicago) TAM07 CP/T violation with K M. S. Sozzi
�� Direct�CPV:� ��� the�meaning�of�it The�first�test�of�the�CKM�paradigm�for�CP�violation CPV�is�a�universal�property�of�weak�interactions, not�a�peculiarity�of�neutral�kaons + − + − Γ → π π − Γ → π π 0 0 ( K ) ( K ) − = ± × 6 ( 5 . 04 0 . 82 ) 10 + − + − Γ → π π + Γ → π π 0 0 ( K ) ( K ) Also:�the�evidence�of�direct�CPV�makes�the� anti"gravity�argument�useless TAM07 CP/T violation with K M. S. Sozzi
ε ’ confronts�the�SM ε ε ε The�qualitative importance�of� ε ’/ ε ≠ 0 clearly�trascends the�(dire)�theoretical�difficulties�in�relating�precisely�such� quantity�to�the�Standard�Model�parameters ε’/ε theoretical�predictions�(SM) New�measurements Experimental�values�are�compatible�with�the�SM� (accidentally�quasi"superweak) ε ’/ ε measured�to�10"15% Waiting�for�lattice�QCD�for�K�to�become�also� a�quantitative test�of�SM. TAM07 CP/T violation with K M. S. Sozzi
KLOE�(1999=2007) At�Frascati DAΦNE�Φ"factory with�separate�e+e" rings�and� 12.5�mrad�crossing�angle working�at� √ s =�m(Φ) =�1019.4�MeV Integrated�luminosity: ~�2.5�fb =1 1999"2006 ( ~ 2.5�W 10 9 K S K L events) TAM07 CP/T violation with K M. S. Sozzi
CPV�by�interferometry �� ��� Decays�from�entangled�K S "K L states�(Φ decays) t 1 Φ t 2 f 1 f 2 K S ,K L K S ,K L ∞ 1 ∫ 2 ∆ = ∆ = I ( f , f ; t ) A ( f , f ; t , t ) dt 1 2 1 2 2 ∆ t ( ) 1 2 2 − Γ ∆ 2 − Γ ∆ − Γ∆ η + η − η η ∆ ∆ + φ − φ t t t / 2 f K f K e e 2 e cos( m t ) L S Γ 1 S 2 S 1 2 1 2 1 2 2 In�principle�many�different�quantities�might�be� measured,�e.g.�f 1 =π+π–,�f 2 =π 0 π 0 ⇒ Re(ε’/ε),�Im(ε’/ε) High�statistics�required,�no�results�available�yet TAM07 CP/T violation with K M. S. Sozzi
Recommend
More recommend