Search for New Physics via ? Rare Decay - PowerPoint PPT Presentation

About This Presentation
Title:

Search for New Physics via ? Rare Decay

Description:

Physics Motivation. Why ? meson is interesting? ? ... Why ? Meson Is Interesting? One of the Goldstone bosons due to spontaneous chiral symmetry breaking ... – PowerPoint PPT presentation

Number of Views:24
Avg rating:3.0/5.0
Slides: 20
Provided by: jlab5
Learn more at: https://www.jlab.org
Category:

less

Transcript and Presenter's Notes

Title: Search for New Physics via ? Rare Decay


1
Search for New Physics via ? Rare Decay
  • Liping Gan
  • University of North Carolina Wilmington

2
Contents
  • Physics Motivation
  • Why ? meson is interesting?
  • ???0??
  • ???0?0
  • Experimental Design
  • Summary

3
Why ? Meson Is Interesting?
  • One of the Goldstone bosons due to spontaneous
    chiral symmetry breaking
  • The heaviest member in the octet pseudoscalar
    mesons
  • Provide a rich program to investigate evidences
    of symmetry breaking and the new physics beyond
    Standard Model

4
The Neutral ? Decay (from B.Nefkens)
5
Study of the ???0?? Decay
  • A stringent test of the ?PTh prediction at ?(p6)
    level
  • Tree level amplitudes (both ?(p2) and ?(p4))
    vanish
  • ?(p4) loop terms involving kaons are suppressed
    large mass of kaon
  • ?(p4) loop terms involving pions are suppressed
    by G parity
  • The first sizable contribution comes at ?(p6)
    level
  • A long history that experimental results have
    large discrepancies with theoretic predictions.
  • Current experimental limits in PDG is BR(???0??
    )lt4.4x10-4

6
Theoretical Status on ???0??
By E. Oset et al.
Unitarized ?PTh with new PDG inputs 0.330.08

7
Study of ???0 ?0 Reaction
  • The Origin of CP violation is still a mystery
  • CP violation is described in SM by the phase in
    the Cabibbo-Kobayashi-Maskawa quark mixing
    matrix. A recent SM calculation predicts BR(???0
    ?0)lt3x10-17
  • The ???0 ?0 is one of a few available
    flavor-conserving reactions listed in PDG to test
    CP violation.
  • Current experimental limit in PDG is BR(???0
    ?0)lt4.3x10-4
  • Unique test of P and PC symmetries, and search
    for new physics beyond SM

8
History of the ???0?? Measurements
After 1980
A long standing ? puzzle is still un-settled.
9
GAMS Experiment on ???0?? at Serpukhov
  • Experimental result was first published in 1981
  • The ?s were produced with 30 GeV/c ?- beam in
    the ?-p??n reaction
  • Decay ?s were detected by lead-glass wall

Final result (D. Alde et al.) 40 of ???0??
events BR(???0??)(7.11.4)x10-4 ?(???0??)0.840
.17 eV
  • Major Background
  • ?-p? ?0?0n
  • ? ??0?0?0

10
CB experiment on ???0?? at AGS
  • About 3x107 ?s data were collected in 1998 at
    AGS, BNL
  • The ?s were produced with 720 MeV/c ?- beam
    through the ?-p??n reaction
  • NaI crystal ball calorimeter with 672 modules
  • Decay ?s energy range 50-500 MeV

11
CB Data Analysis I (by S. Prakhov et al. in 2005)
?-p? ?0?0n
? ??0?0?0
  • Final result
  • 1600 of ???0?? events
  • BR(???0??)(3.50.9)x10-4
  • ?(???0??)0.450.12 eV

12
CB Data Analysis II (by N. Knecht et al. in 2004)
  • Final result
  • 12137 of ???0?? events
  • BR(???0??)(2.70.90.8)x10-4
  • ?(???0??)0.320.15 eV

13
What can be improved?
  • Tagged ? to reduce non-resonance ?0?0 background
  • Higher beam energy to reduce the background from
    ?? ?0?0 ?0
  • Lower relative threshold for ?-ray detection
  • Improve calorimeter resolution
  • Calorimeter with PWO4 insertion
  • Higher energy resolution ? improve ?0??invariance
    mass
  • Higher granularity? better position resolution
    and less pile-up clusters
  • Large statistics to provide a precision
    measurement of Dalitz plot

14
Experimental Design
  • ? produced on LH2 target with 11 GeV tagged
    photon beam
  • Tag ? by measuring recoil p with GlueX
  • Forward calorimeter with PWO4 insertion to detect
    multi-photons from the ? decay

15
Kinematics of Recoil Proton
  • Polar angle 65o-80o
  • Kinetic energy 20-300 MeV
  • Momentum 200-800 MeV/c

16
Acceptance
17
Invariance Mass of ?0??
18
Rate Estimation
  • The ? production rateLH2 target length L30cm,
    ?0.0708 g/cm3
  • The ?p??p cross section 1 µb
  • Photon beam intensity N?1.5x107 Hz
  • The ???0?? detection rate BR(???0?? )4x10-4 ,
    detection efficiency 11.4

19
Summary
  • High energy and high intensity tagged photon beam
  • First tagged ? experiment by measuring recoil p
    with GlueX
  • High resolution calorimeter with PWO4 crystal
    insertion to reduce the major backgrounds
  • Precision measurement on ?(???0??) to test the
    ?PTh prediction at ?(p6) order
  • Measurements of branching ratio/upper limits for
    various rare and forbidden ? decays involving
    photons in the final states to test P, PC and C
    symmetries, and search for new physics beyond
    Standard Model
Write a Comment
User Comments (0)
About PowerShow.com