ultra-rare kaon decay for a precision test of the standard model kristin schimert university of...
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ULTRA-RARE KAON DECAY FOR A PRECISION TEST OF THE STANDARD MODEL
K R I S T I N S C H I M E R T
U N I V E R S I T Y O F C A L I F O R N I A , B E R K E L E Y
P H Y S I C S 1 2 9
7 D E C E M B E R 2 0 1 0
K+ → π+ ν`ν
Kristin Schimert
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Overview
1) Motivation
2) Goals
3) Theoretical background: see Francisco’s presentation
4) Experimental strategy
5) Detectors
7 December 2010
K+ → π+ ν`ν
Kristin Schimert
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Why study rare kaon decays?
7 December 2010
1) Explicit violations of the Standard Model (SM)
2) SM parameters
3) CP Violation
4) Strong interactions at low energy
Most common kaon decays:
Kristin Schimert
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The NA62 experiment
7 December 2010
NA62 Collaboration: Bern ITP, Birmingham, Bristol, CERN, Dubna, Ferrara, Fairfax, Florence, Frascati, Glasgow, IHEP, INR, Liverpool, Louvain, Mainz, Merced, Naples, Perugia, Pisa,Rome I, Rome II, San Luis Potosi, SLAC, Sofia, TRIUMF, Turin
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Motivation for using K+ → π+ ν`ν
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• Excellent process to study flavor physics because of clean nature• Dominated by short-distance dynamics• Mainly one-loop diagrams with top-quark intermediate states
• High theoretical precision
• But most precise experimental result (at BNL) is
Gap between theoretical precision and experimental error: strong motivation for experimental precision
• Extract 10% precision measurement of CKM parameter |Vtd|• Deviation from theory indicates new physics
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Experimental goals
Collect about 80 events with signal:background ratio of 10:1 in two years of data taking Requires 1013 K+ decays
with a branching ratio of 10-10
Construction criteria: kaon intensity, signal acceptance, background suppression
7 December 2010
Kristin Schimert
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Experimental strategy
400 GeV/c protons from CERN SPS hit a beryllium target, producing a secondary charged beam of 75 GeV/c (K+, π+, p+)
Signature of signal = a single π+ track reconstructed downstream of the decay volume and matched to a K+ track upstream
Need timing, spatial and angular info to match π+ and K+ tracks7 December 2010
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Detector overview
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Tracking devices for both K+ and π+
Calorimeters to veto photons, positrons, and muonsParticle identification systems to identify incident kaons
and to distinguish π+ from μ+ and e+
Guiding principles for construction of NA62 detectors: “accurate kinematic reconstruction, precise particle timing, efficiency of the vetoes, and excellent particle identification”
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Detector overview
http://na62.web.cern.ch/na62/Documents/MaterialPresentationSchemas.html 7 December 2010
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References
1. Proposal to measure the rare decay K+ → π+ ν`ν at the CERN SPS http://na62.web.cern.ch/na62/Documents/Proposal%20spsc-2005-013.pdf
2. Technical Design Documenthttp://na62.web.cern.ch/NA62/Documents/TD_Full_doc_v10.pdf
3. The accelerator complexhttp://public.web.cern.ch/public/en/research/AccelComplex-en.html
4. Rare kaon decayshttp://pdg.lbl.gov/2009/reviews/rpp2009-rev-rare-kaon-decays.pdf
5. Super proton synchroton marks its 25th birthdayhttp://cerncourier.com/cws/article/cern/28470
7 December 2010