NA48/3 - The Strange Penguin Experiment by James Barnard

Precise measurement of the branching ratio for the decay K +   Very rare decay - branching ratio ~ Aim to collect about 80 events in two years of data taking Signal to background ratio of 10:1 What is NA48/3?

But what about the penguins? Main Standard model decay modes are via the Z 0 penguin diagram s d Or, a little more artistically…

Sounds hard. Why bother? Exceptionally clean measurement of CKM parameter |V td | - very little hadronic uncertainty Independent of data from the B meson system Excellent test of the short distance behaviour of the Standard Model This bit here The Unitary Triangle

I’m still not convinced….. Higgs sensitivity (fat penguin diagrams) Super-symmetry sensitivity (spenguin diagrams)

Even so, is pretty small! Decay modeBranching ratio K +   0.63 K +     0.21 K +       0.06 K +       0.02 K +     0.03 K +   e  0.05 Need multiple redundancy in particle identification and momentum measurements in order to suppress background sufficiently

Gigatracker (SPIBES+FTPC) uses pixels and gas chambers to accurately measure K + momenta Requires sub-nanosecond time resolution due to huge particle fluxes involved Large vacuum chamber for decays to occur in - ensures only decays occur here (not interactions with air) Rings of lead scintillator ANTI- counters capture large angle photons from  0 decays Chambers of straw tubes provide redundant measurement of outgoing charged particle momentum Straw tubes chosen due to their capability to operate in vacuum RICH (Cherenkov radiation) detector identifies particles providing  + /  + separation CHOD hodoscope for triggering and precise timing of charged track - helps match Gigatracker signal to other tracks Liquid krypton electromagnetic calorimeter captures medium angle photons from  0 decays and any e + produced Magnetised hadron calorimeter and muon detector identifies  + with inefficiences < Also deflects charged beam away from small angle photon detectors 400 GeV protons from SPS hit target to produce high intensity 75 GeV p/  + /K + beam (~6% K + ) CEDAR (Cherenkov radiation) tracker tags K + with excellent time resolution (50MHz) The proposed experiment

With such high precision measurements it is possible to extract the K +    decays Now all we need is the funding! The result Decay modeBranching ratio K +   0.63 K +     0.21 K +       0.06 K +       0.02 K +     0.03 K +   e  0.05 Rejection techniques  + ID, 2-body kinematics  veto, 2-body kinematics Charge veto, kinematics  veto, kinematics  veto,  + ID  veto, E/p (=1 for e + )

The end! For more information visit: And many thanks to Paolo Valente for the penguin!