b s → mm at d Ø
DESCRIPTION
B s → mm at D Ø. New result first presented by Fermilab Postdoc Masato Aoki at FPCP2010. Primary author of manuscript now submitted to Physics Letters arXiv:1006.3469v1 [hep-ex]. News from Batavia. Tevatron, detectors, collaborations all going strong Now have 9 fb -1 delivered. - PowerPoint PPT PresentationTRANSCRIPT
BBss→→ at D at DØØ
New result first presented by Fermilab Postdoc Masato Aoki at
FPCP2010
Primary author of manuscript now
submitted to Physics Letters
arXiv:1006.3469v1 [hep-
ex]
B. Casey, ICHEP2010B. Casey, ICHEP2010 22
News from BataviaNews from Batavia
• Tevatron, detectors, collaborations all going strong
• Now have 9 fb-1
delivered.
• Expecting ~12 fb-1 per experiment
• Lots of exciting results still coming out
“The Toes of Joe
Lykken”
Party celebrating 9 fb-
1
July 16, 2010
B. Casey, ICHEP2010B. Casey, ICHEP2010 33
Leptonic B decaysLeptonic B decays
• Standard Model rate well understood
• Standard Model rate is small
• New physics enhancements can be large
SM BF:
B(Bs→) = (3.6±0.3) x 10-9
Buras, arXiv:0904.4917
B. Casey, ICHEP2010B. Casey, ICHEP2010 44
Kp
bc
KBs
Signal and BackgroundSignal and Background
c
p
p
b
b
p
p
Bs
b p
p
bc
Signal sequential
double
B→KK
B. Casey, ICHEP2010B. Casey, ICHEP2010 55
Background reductionBackground reduction
SV
PV
Flight length significance
sidebands
Signal MC + J/ K data and MC
Minimum DCA
Signal MC + J/ K data and MC
sidebands
sidebands
Signal MC + J/ K data and MC
Angle between
momentum and directionVertex 2
sidebands
Signal MC + J/ K data and MC
pT ()
sidebands
Signal MC + J/ K
data and MCsidebands
Minimum pT ()
Signal MC + J/ K
data and MC
B. Casey, ICHEP2010B. Casey, ICHEP2010 66
Background reductionBackground reduction
Angle between momentum and direction
Minimum DCA
Vertex 2
SV
PV
Flight length significance
pT ()Minimum pT ()
Dave Butler
B. Casey, ICHEP2010B. Casey, ICHEP2010 77
Background reductionBackground reduction
Bayesian Neural Network
Signal region
B+→J/ K+
Calibration sample
Expect ~3 signal events in our data with these cuts
B. Casey, ICHEP2010B. Casey, ICHEP2010 88
BB→→hh++hh
After penetration + matching cuts
B→D0, D0→K10-20 before outer muon layers
Matching variables
default tuned
B→KK0.8±0.
60.5±0.
4B→K ~0.1 ~0.05B→ ~0 ~0
total0.9±0.
60.6±0.
4
B. Casey, ICHEP2010B. Casey, ICHEP2010 99
Signal extractionSignal extraction
2D fit to m() and BNN
Background shape from BNN sideband,
norm from m() sidebands
m()
BNN
double
sequential
m()
B. Casey, ICHEP2010B. Casey, ICHEP2010 1010
ComparisonsComparisons
Old: 1D just counting events in signal region
New: 2D including shape in signal region
~40% improvement in expected limit New/OldBNN
New
Old
m()
m()
B. Casey, ICHEP2010B. Casey, ICHEP2010 1111
ResultsResults
In highest sensitivity region:
51 ± 4 expected bkg events,
55 data events
BF < 51 x 10-9 (95% CL)
14x SM
Expected limit: 38 x 10-9
11x SM
arXiv:1006.3469v1 [hep-ex]CDF preliminary 2009:
43 x 10-9 observed
33 x 10-9 expected
B. Casey, ICHEP2010B. Casey, ICHEP2010 1212
ConclusionsConclusions
• Have a new limit based on 6.1 fb-1
– 4.6 times more data than last pub
– 2.4 times sensitivity of last pub
• Includes many improvements– 33% reduction in KK background at
same efficiency
– 40% improvement from 2D fitting
• Next steps– More data
– Design variables to target dominant background of gluon fusion bb production where both B mesons decay semileptonically.
Present
Future