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Mike Strauss

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Title: Mike Strauss


1
Rare Heavy Flavor Decays at DØ
  • Mike Strauss
  • for the DØ Collaboration
  • The University of Oklahoma
  • The Oklahoma Center for High Energy Physics

XXXIII International Conference on High Energy
Physics Moscow, Russia 26 July 2 August, 2006
2
Outline
  • Search for D ? p m m
  • FCNC in Charm Sector
  • Search for Bs0 ? m m and Bs0 ? f m m
  • FCNC in Bottom Sector

3
FCNC in the Charm Sector
  • Experimental limits exist for b?s and s?d
  • Some models predict violations from SM in up
    quark sector, but not down quark sector
  • RPV in the up sector
  • Burdman et.al.
  • hep-ph/0112234
  • Little Higgs Models
  • Fajfer et.al.
  • hep-ph/0511048

SM
c ? u mm
4
c ? umm Analysis
  • ?1 fb1 of data
  • Find Ds ? pf ? pmm
  • (100 of Ds ? pf)
  • BF(Ds?pf) 0.0360.009
  • BF(f ?mm)
  • (2.8500.19)104
  • Search for D ? pmm
  • for m(mm) ? m(f)
  • Add track to low mass dimuon candidate

w
f
5
Selection and Optimization Criteria
  • Isolation ID p(D)/?pcone
  • R (?h2 ?f2)½ lt 1.0
  • Transverse flight length significance SD
  • Collinearity angle QD
  • Pion impact parameter significance Sp
  • M c2vtx kp2 DRp2
  • kp 1/pT(p)

6
D ? pf ? pmm
0.96 lt m(m m) lt 1.06 GeV/c2
Resonance optimized cuts
Loose cuts
D
Ds
n(D) 26 9 n(Ds) 65 11
7
Extracting the Resonant Branching Fraction
fc?D Fraction produced in fragmentation fp
Prompt fraction e Reconstruction efficiency
SM 1.77106 CLEO-c (f?ee)
8
Nonresonant D ? p m m-
0.2 lt m(mm) lt 0.96 GeV/c2 1.06 lt m(mm) lt 1.76
GeV/c2
0.96 lt m(mm) lt 1.06 GeV/c2
BF(D ? p m m-) lt 4.7106 _at_ 90 C.L
9
Bs0 ? m m
  • FCNC with zero cross section at tree level
  • SM Branching Fraction
  • BF(Bs0 ? m m) (3.42 0.54) 109
  • BF(Bd0 ? m m) (1.00 0.14) 1010
  • Non-SM processes can enhance BF(Bs0 ? m m)
  • MSSM enhances BF up to 3 orders of magnitude
  • 2HDM, minimal supergravity, minimal SO(10) GUT,
    all have BF enhancements

10
Search for Bs0 ? m m
  • 300 pb-1 data analyzed (PRL 94, 071802 (2005))
  • Sensitivity for 0.7 fb-1 determined
  • Blind analysis to avoid bias
  • Side bands used for background determination
  • Normalize to resonant decay B ? J/y K
  • pT(m) gt2.5 GeV/c
  • h(m)lt 2
  • c2vertex lt 10
  • CFT hits gt 4
  • SMT hits gt 3
  • pT(Bs) gt 5 GeV/c
  • dLxy lt 0.15 mm

11
Analysis and Optimization
  • Optimization using MC signal and background from
    data sidebands using
  • Collinearity (Pointing) Angle
  • Decay length significance
  • Isolation

12
Analysis and Normalization
  • R BF(Bd)/BF(Bs) is small due to Vtd/Vts2
  • eB/eBs efficiency
  • eBd /eBs relative efficiency for Bd ?m m-
    versus Bs? m m-
  • fs/fu fragmentation ratio

0.3 fb1
additional 0.4 fb1
13
300 pb-1 Limit (published 2005)
Observed 4, expect 4.3 1.2
BF(Bs ? mm-) lt 5.0107 _at_ 95 C.L.
14
DØ Sensitivity 0.7 fb-1
0.4 fb1
  • For new dataset of 0.4 fb1
  • Expect 2.2 0.7 background events
  • Expect a sensitivity of about 3.0107 _at_ 95 C.L.
  • Combined 0.7 fb1 sensitivity of 1.9107 _at_ 95
    C.L

15
Search for Bs0 ? f m m
  • ?0.45 fb1 of data
  • Similar selection criteria to Bs0 ? m m
  • 0.5 lt m(mm) lt 4.4 GeV/c2 excluding 5s around
    J/y y(2S)
  • f ? K K
  • pT (K)gt0.7 GeV/c
  • 1.008 lt m(f) lt 1.032 GeV/c2

16
Analysis Method
  • Blind analysis Optimization using MC signal and
    background from data sidebands using
  • Pointing Angle lt 0.1 rad
  • Decay length significance gt 10.3
  • Isolation gt 0.72
  • Normalize to resonant decay Bs ? J/y f

17
Bs0 ? f m m Results
  • Expected background from sidebands 1.6 0.4
    events
  • Observe zero events in signal region

18
Bs0 ? f m m Results
_at_ 95 C.L
(10 times better than best limit)
Accepted for PRD Rapid Communication
  • SM BF(Bs0 ? ? m m) 1.6 106 (30
    uncertainty)
  • (Geng and Liu, J. Phys G 29, 1103 (2003)
  • Accessible with about 4 fb1 of data

19
Conclusions
  • Searches for FCNC can give insight into physics
    beyond the Standard Model
  • New DØ limits on D ? pmmand Bs0 ? ? m m are
    worlds best
  • New limit on Bs0 ? m m should be coming soon
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