ultra-rare kaon decay For a precision test of the standard model Kristin Schimert

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ULTRA-RARE KAON DECAY FOR A PRECISION TEST OF THE STANDARD MODEL KRISTIN SCHIMERT UNIVERSITY OF CALIFORNIA, BERKELEY PHYSICS 129 7 DECEMBER 2010 K + → π + ν`ν

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K +  → π +  ν ` ν. ultra-rare kaon decay For a precision test of the standard model Kristin Schimert University of california , berkeley Physics 129 7 December 2010. Overview. Motivation Goals Theoretical background: see Francisco’s presentation Experimental strategy Detectors. - PowerPoint PPT Presentation

Transcript of ultra-rare kaon decay For a precision test of the standard model Kristin Schimert

Page 1: ultra-rare  kaon  decay  For  a precision test of the standard model Kristin  Schimert

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 TU 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 97 D E C E M B E R 2 0 1 0

K+ → π+ ν`ν

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Overview

1) Motivation2) Goals3) Theoretical background: see Francisco’s presentation4) Experimental strategy5) Detectors

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K+ → π+ ν`ν

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Why study rare kaon decays?

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1) Explicit violations of the Standard Model (SM)

2) SM parameters

3) CP Violation4) Strong interactions

at low energy

Most common kaon decays:

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The NA62 experiment

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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

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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+ tracks

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CERN SPS

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NA62

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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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Kinematic rejection

7 December 2010rejects more than 90% of K+ decays!

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Detector overview

http://na62.web.cern.ch/na62/Documents/MaterialPresentationSchemas.html 7 December 2010

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Detector layout

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Large-angle photon veto

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γγ

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Large-angle veto

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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

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