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06/01/10 Menu2010 - Phil Rubin, George Mason University 1
Measurement ofBR(K → eν)/BR(K → μν)
Phil Rubin
for the NA62 (CERN) Collaboration
Ultra-rare Kaon Decays
06/01/10 Menu2010 - Phil Rubin, George Mason University 2
Leptonic Decays
● Test theoretical tools● Search for new physics
━ Rates━ Lepton Universality
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Lepton Universality
[a few %]
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New Physicseg., MSSM
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Experimental Status
PDG '08 (based on '70s measurements)
KLOE '09~14K Ke2 events
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NA62(Phase I: Using the NA48 Detector)
● ~150 K Ke2 events
● < 10% background
● δRK/RK < 0.5%
Goal:
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Data Taking and Analysis
● 4-month run in 2007; 2-week (systematics) run in 2008
● Simultaneous Ke2 – Kμ2 collection
●
● RK calculated in 10 momentum bins (account for background-momentum dependencies)
● Primary systematic: NB(Ke2)
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Event Selection
● Kinematics
━ Good for pℓ < 25 GeV/c
● E/p
━ e: 0.9 < E/p < 1.1
━ μ: E/p < 0.85
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40% of the Data, Preliminary
~51 K Ke2 events, ~8% background
x5 x25 x5
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Preliminary Result
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RK Conclusion
● Measurement agrees with Standard Model prediction to 1.5σ
● Total NA62 data set will yield 0.4%-0.5% measurement.
0 100 200 300 400 500 600 700 800 900 1000
02
04
06
08
01
00
Charged Higgs Mass [GeV/c2]
tan
β
tan β vs mH
(95% Exclusion Limits)
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● Strongly suppressed
● Calculable with uncertainty O(10%)
● Very sensitive to new physics
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NA62● 10% measurement of
━ 1013 kaon decays (2 yrs); 10% bkgd uncertainty
● Decay-in-flight from high momentum beam● High resolution and hermiticity
━ 92% of Γ constrained kinematically━
━ Timing to match Kπ━ Veto photons and muons
● Particle identification
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NA62 Detector Layout
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Source Events/yrSignal 55Background 7.5-9.4
Channel Fraction (%)4.3-7.5
2.2≤3
≤1.5~2
~0.7
Schedule and Sensitivity
● First data in second half of 2012