Title: Mike Strauss
1Rare 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
2Outline
- Search for D ? p m m
- FCNC in Charm Sector
- Search for Bs0 ? m m and Bs0 ? f m m
- FCNC in Bottom Sector
3FCNC 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
4c ? 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
5Selection 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)
6D ? 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
7Extracting the Resonant Branching Fraction
fc?D Fraction produced in fragmentation fp
Prompt fraction e Reconstruction efficiency
SM 1.77106 CLEO-c (f?ee)
8Nonresonant 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
9Bs0 ? 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
10Search 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
11Analysis and Optimization
- Optimization using MC signal and background from
data sidebands using - Collinearity (Pointing) Angle
- Decay length significance
- Isolation
12Analysis 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
13300 pb-1 Limit (published 2005)
Observed 4, expect 4.3 1.2
BF(Bs ? mm-) lt 5.0107 _at_ 95 C.L.
14DØ 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
15Search 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
16Analysis 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
17Bs0 ? f m m Results
- Expected background from sidebands 1.6 0.4
events - Observe zero events in signal region
18Bs0 ? 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
19Conclusions
- 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