beauty at the tevatron
DESCRIPTION
Beauty at the Tevatron. Brendan Casey SEL11, TIFR, 1/11/11. Tevatron. Only machine currently at both the Energy and Luminosity Frontiers Complementary to other machines at each frontier Large B s data set compared to B factories Different channels compared to LHC - PowerPoint PPT PresentationTRANSCRIPT
Beauty at the Tevatron
Brendan CaseySEL11, TIFR,
1/11/11
Tevatron• Only machine currently at both the
Energy and Luminosity Frontiers• Complementary to other machines at
each frontier– Large Bs data set compared to B factories– Different channels compared to LHC
• qqbar WH lnbb vrs gg H gg
• Weak sector (charginos, neutralinos) vrs strong sector (squarks, gluinos)
• Interference effects (top Afb) vrs resonance search (GA )
• Will be superseded by LHC and super B factories but expect to be relevant for a few more years– Still have a lot to analyze with the 2011
data.2/281/11/11B. Casey, SEL11
pbar complexNow producing 2.6
ng of antimatter per year
B. Casey, SEL11 1/11/11 3/28Some familiar faces (plus many more)
B. Casey, SEL11
Overlapping beauty
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BVV polarizationCPV in charm mixing
BDADSK
B. Casey, SEL11
Complementary Beauty
1/11/11 5/28
Very Rare Processescharged currents
neutral currents
B fa
ctor
ies TevatronAnomalous CP Violation
Db = Ds = 1 Db = Ds = 2
b
u n
b
s
l-
l+
l-
b
s
s
bb s
q
q
6/25
Leptonic B decays
• Standard Model rate well understood
• Standard Model rate is small
• New physics enhancements can be large
SM BF:B(Bs→mm) = (3.6±0.3) x 10-9
Buras, arXiv:0904.4917
B. Casey, SEL11 1/11/11 6/28
Kp
bc
KBs
m
m
Signal and Background
c
p
p
b
b
m
m
p
p
Bs
m
m
b p
p
m
mbc
Signal sequential
double
B→KK
B. Casey, SEL11 1/11/11 7/28
Background reduction
SV
PV
Flight length significance
sidebands
Signal MC + J/y K data and MC
Minimum DCA
Signal MC + J/y K data and MC
sidebands
sidebands
Signal MC + J/y K data and MC
Angle between
momentum and directionVertex c2
sidebands
Signal MC + J/y K data and MC
pT (mm)
sidebands
Signal MC + J/y K
data and MCsidebands
Minimum pT (m)
Signal MC + J/y K
data and MC
mm
B. Casey, SEL11 1/11/11 8/28
Background reductionMultivariate discriminants
Expect ~3 signal events in D0 data with these cuts
B. Casey, SEL11 1/11/11 9/28
Expect ~1 signal event in CDF data with these cuts
Almost 2x rapidity coverage at D0 + higher purity
Results
preliminary 2009:43 x 10-9 observed (12xSM)
33 x 10-9 expected (9xSM)B. Casey, SEL11 1/11/11
2010:51 x 10-9 observed (14xSM) 38 x 10-9 expected (11xSM)
B. Casey, SEL11
Why?
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Tracker radius1.3 m
vrs 0.5 m
B. Casey, SEL11
What’s next?
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~20k B+ @ 3.7 fb-1, 2 TeVvrs
~10k B+ @ 34 pb-1, 7 TeV
A. Schopper, CERN Council Report, Dec. 17 2010
B. Casey, SEL11
CPV in Bs mixing
1/11/11 13/28
(WS Hou)
B. Casey, SEL11
Dimuon charge asymmetry
1/11/11 14/28
tW Wb
s b
s
tW Wb
s b
s
t
t
)()()()(
XbbNXbbNXbbNXbbNASL --
--
-
mmmmmmmm
Bs mixing in the mirror
B. Casey, SEL11
Measurement history at Dzero• 1992: first internal note outlining measurement• 1994: 7.3 pb-1: A = (81-96)/(81+96)• 1996: significant asymmetries observed due to
asymmetries in range-out.
– From then on, Dzero switches polarity every few weeks to enable this measurement
• 2003: analysis of ~100 pb-1 RunII data indicates we are competitive. Begin planning for a 1 fb-1
result.– Dimuon result. Single muon result ruled out
because completely dominated by Kaon asymmetry1/11/11 15/28
Iron toroid+ -
B. Casey, SEL11
Measurement history at Dzero• 1 fb-1 result:
– ASL = -(0.92 ± 0.44 ± 0.32)%– World leading measurement– Dominant error is now Kaon asymmetry
determined using D*Dp, DKp, KmX• Raw asymmetry A = -(0.05± 0.13)%• Kaon asymmetry AK = -(0.23 ± 0.08)%
1/11/11 16/28
B. Casey, SEL11
2010 Update
• Need a way to constrain the Kaon asymmetry• Two samples:
– Like-sign dimuon system = physics + Kaon– Single muon system: asymmetry is almost
entirely from the Kaons• Use the single muon system to make a high
statistics measurement of the kaon asymmetry and subtract it from the dimuon asymmetry
1/11/11 17/28
B. Casey, SEL11
Dimuon results• ASL =
(0.957±0.251±0.146)%• Systematic error dominated
by Kaon asymmetry– In dimuon analysis:
• 2.1%– In combined single and
dimuon analysis:• 0.15%
• Verified the B content by measuring the mixing probability in the first fb-1 data set– X = 0.136±0.001±0.024– PDG: 0.1281± 0.0076
1/11/11 18/28
19/25
Bs →J/y f: Kaon type CPV
Pseudo scalar →Vector + Vector. Both even and odd states contribute.
Angular analysis tells if its even or odd.
Lifetime measurement tells if its long or short Look for even states decaying
with a longer lifetime⇛ CPV
Dt/t ≈ 10%
t(Short)t(Long)
Bs(even)
Bs(odd)
20/25
Bs →J/y f: Bd type CPV
Need to analyze Bs and Bs initial states separately
Bs
Bs
J/y f
Mirror image of a double slit experiment
mm
KK
Fragmentation: s or s?
recoil: b or b?
m
K
Validate tagging performance using B± samples
Act
ual p
erfo
rman
ce
expected performance
Bs
BsJ/y f
p
p
21/25
J/y f resultsResults taken from a multi-parameter fit including flavor, lifetime, polarization, backgrounds, CP conserving, and CP violating interference
Latest comb not available but expect less than 2s effect
B. Casey, SEL11
Future
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A. Schopper, CERN Council Report, Dec. 17 2010
23/25
Future• The large anomalous CPV in Bs mixing reported at the Tevatron +
minimal flavor violation predicts EDMs are “around the corner!”– Gino Isidori, ICHEP 2010 plenary talk
• Need lepton and quark EDM searches to distinguish new weak interaction from a small QQCD
• Need different leptons to determine if the new phase is universal
• New g-2 experiment: muon EDM below 10-21 e-cm
• Nuclear EDMs can be probed at Project X wit copious production of high-Z nuclei to perform EDM measurements far beyond limits from Hg
Large Bs CPV shrinks available parameter space
Titaniumneutron
Mercury
10-25
10-30
Buras, Isidori, Paradisi arXiv:1007.5291
Bs CPV
B. Casey, SEL11
Conclusions
• Beauty at the Tevatron has been beautiful (even in a somewhat ugly environment.)
• Next round of updates should still be interesting and competitive. Then its LHCb’s turn.
• In any case, the Tevatron has clearly demonstrated the advantages of having a luminosity frontier program at an energy frontier machine.
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