NA48/1: NA48/1: K K s s rare rare decays decays and and Hyperons Hyperons Mauro Raggi Perugia University & INFN Vemes Rencontres du Vietnam HANOI August 5-11 2004 On behalf of the NA48/1 Collaboration: Cambridge, CERN, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Warsaw, Wien
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NA48/1:NA48/1:KKss rare rare decaysdecays and and HyperonsHyperons
Mauro RaggiPerugia University & INFN
Vemes Rencontres du VietnamHANOI August 5-11 2004
On behalf of the NA48/1 Collaboration:Cambridge, CERN, Chicago, Dubna, Edinburgh, Ferrara, Firenze,
Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Warsaw, Wien
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
OutlineOutline
The NA48/1 beam and detector
KLØπ0l+l- and CKM matrix
First observation of: KsØπ0e+e- and KsØπ0µ+µ-
BR and decay asymmetry Ξ0ØΛγ
Preliminary information on Ξ0 beta decay
Conclusion
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
The NA48/1 KThe NA48/1 KS S beam linebeam line
SPS protons energy: 400 GeVDuty cycle: 4.8 s/ 16.8 s
Production angle: -4.2 mradProton per pulse on target: 5·1010
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
The NA48/1 detectorThe NA48/1 detector
%5.01.0%2.3)(⊕⊕=
EEEEσ
ppp
×⊕= 009.0%48.0)(σ
Liquid Kr EM Calorimeter
Spectrometer- 4 DCH- Magnet
mmyxVTX 2~,σ
mmyx 3.1, <σ E in GeV
E in GeV
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
NA48 data taking periodsNA48 data taking periods
1997 : ε’/ε run1998 : ε’/ε run1999 : ε’/ε run + 2 days of KS2000 : KL only + KS high intensity2001 : ε’/ε run + few days of KS2002 : KS High intensity2003 : K± High intensity2004 : K± High intensity
NA48
NA48/1
NA48/2
No spectrometer
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
Interest of KInterest of KLLÆÆππ00ll++ll--
η can be measured using :−+→ llKL
0πρ can be measured using :
−+++ → llK π vvKL0π→
Unitarity triangle
Direct CP violating component is sensitive to Im(λt):
52)Im( ληλ At = tdtst VV *=λ
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
ΞΞ00ÆÆΛγΛγ decay asymmetrydecay asymmetryDecay asymmetry in weak radiative hyperons decay was predicted to be small.Discovery of large decay asymmetry α in weak radiative Σ+ØpγNew SU(3) breaking models were developed:– Pole models based on χPT approach:
α > 0 only for Ξ0ØΛγA measurements of α in Ξ0ØΛγ can distinguish between different models
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
α(Ξα(Ξ00ÆÆΛγ)Λγ) measurementsmeasurements
First observation of a negative decay asymmetry for Ξ0 decay
ΘΛ angle between incoming Ξ0 and outgoing p in the Λ rest frame
(Signal-background)/(flat MC)
syststat 06.018.078.0 ±±−=α
)cos)()(1(cos
00 Λ
−
Λ
ΘΛ→Ξ→Λ−=Θ
γαπα pNd
dN
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
BR(BR(ΞΞ00ÆÆΛγΛγ))
Signal: 730 events
Background: 58.2 ± 7.8 events
30 10)06.005.016.1()( −⋅±±=Λ→Ξ syststatBR γ
2 days of 1999 data
Almost a factor 100 more statistic is expected in 2002 dataAnalysis is in progress …
Systematic error dominated by asymmetry measurements
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
ΞΞ00 beta decay: beta decay: ΞΞ00ÆÆΣΣ++ee−−ννee
Physics goals:- Vus measurements using BR- studies of SU(3) breaking in the
form factors
Signal region MeVMM PDGrec 10<− ++ ΣΣ
BG ~ 3%
eve−+Σ→Ξ0
0πp
00 πΛ→Ξevpe−
World largest sample of Ξ0 β decay
BG ~ 3%
M. M. RaggiRaggi NA48 CollaborationNA48 Collaboration
ConclusionsConclusions2 new rare K decays observed:
KSØπ0e+e-
KS Øπ0µ+µ-
The form factor aS has been extracted and an estimate of KL BR was givenThe Ξ0ØΛγ decay asymmetry and BR have been measured on 1999 data.World largest sample of Ξ0 beta decay has been collected and BR ratio measurements will come soon