Post on 13-Dec-2015
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Rare Bottom and Charm Decays at the Tevatron
Dmitri Tsybychev (SUNY at Stony Brook)On behalf of CDF and D0 Collaborations
Flavor Physics and CP-Violation Taiwan, May 8, 2008
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Rare Decays Electroweak symmetry breaking determines flavor
structure CKM matrix, FCNC, CP-violation
Rare decays are instrumental probes CKM matrix Sizeable deviations – sign of New Physics
FCNC decays are forbidden at tree level in the SM Rates are highly suppressed in SM
NP allows tree level processes, enhancement in loops Look for
B0(s )→ μ+μ-
B±0(s)→ h μ+μ-
D0 → μ+μ-
D± → π±μ+μ-
B Physics at the Tevatron
Flavor Creation
q b
q bFlavor Excitation
q q
bg
b
b
Gluon Splitting
g
g g
b
- Mechanisms for b production in pp collisions at 1.96 TeV
•Total inelastic cross section at the Tevatron is ~1000 larger than b cross section
• Plethora of states accessible only at the Tevatron: Bs, Bc, Λb, Ξb, Σb…
•Large backgrounds suppressed by triggers that target specific decays
(bb)
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Analysis Procedures Preselection of dimuon events
Trigger Selection optimization Blind analysis
Avoid biases Side-band background subtraction
Normalization to resonant decays in similar final state
Large, well-known BR in SM Efficiency normalization Significant signal – perform measurement
Otherwise set limit for relevant process
)()( XnormBRf
f
N
NXsigBR
sig
norm
sig
norm
norm
sig
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Discriminating Variables
Isolation
Flight length significance
impact parameter
significance
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B0(s)→μ+μ-
Br(B0s→μ+μ-) = (3.42 ± 0.54)x10-9 Buras, PLB 566, 115 (2003)
Br(B0d→μ+μ-) = (1.00 ± 0.14)x10-9 suppressed by (Vtd/Vts)2
New Physics contribution: MSSM ~tan6(for largetan( SUSY with R-parity violation (RPV) Z’ with off diagonal couplings
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B0(s)→μ+μ- Selection and Optimization
Signal: MC Background: data
mass sidebands Final selection
Likelihood ratio (D0) Neural network (CDF)
Check selection with control samples Misidentified muon Same sign muons
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B0(s)→μ+μ- Normalization
Combinatorial backgrounds estimated from fit in mass sidebands and propagated to signal region
BR normalized to B±→J/ψK ±
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B0(s)→μ+μ- Results
No excess over expected background observed
B0s→μ+μ- B0
d→μ+μ- CDF < 4.7x10-8 < 1.5x10-8
PRL 100,101802 (2008)
D0 < 7.3x10-8
D0 Note 5344
New HFAG average < 4.7 x10-8 @ 90% CLMost stringent to date!
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B(±,0)(s)→h(±,0)μ+μ-
Non resonant decays via box or penguin diagrams
BaBar/Belle: B±
u→K+- PRD73, 092001 (2006)
B0d→K*+- PRL96, 251801
(2006) Look for B0
s→+-
Prediction: BR(B0
s→+-) =1.6x10-6
JPHYS G 29, 1103 (2003) NP
Larger BR Modified invariant
mass Modified angular
distributions
Fourth GenerationPRD 77, 014016 (2008)
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B(±,0)(s)→h(±,0)μ+μ- Observations
Remove resonant J/ψ,ψ(2S) by cutting on invariant mass
44.7±5.84.5
18.5±3.62.9
7.5±1.52.4
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B(±,0)(s)→h(±,0)μ+μ- Results
BR(B0s→+-) @ 90%CL
CDF(hep-ex/0804.3908) < 5.0x10-6 (includes uncertainty
on normalization channel)
D0 (PRD 74 , 031107 (2006)) < 3.2x10-6
B(±,0)(s)→h(±,0)l+l-
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D0→μ+μ-
B0s→μ+μ- vs D0→μ+μ-
down quark sector vs up quark sector
Short range contribution BR~10-18
GIM suppressed Long range contribution
BR ~ 4 x 10-13 Burdman et al. hep-ph/0112235 Significant
enhancement possible in SUSY with R-parity violation
Long range SM
SUSY with R-parity violation
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D0→μ+μ- Analysis
Events from two-track trigger Normalize to D0→ to cancel
acceptance and trigger effects Background reduction by D* tag
Muon ID efficiency from J/ψ→μμ data
Muon mistag rate from D0 →K
Background estimated from MC
Dominant background from B → μμX Reduced by the impact
parameter and lifetime significance cuts
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Results
Detector CMU-CMU CMU-CMX CMX-CMX
Total Expected Background
4.9 ± 1.3 2.7 ± 1.0 1.0 ± 0.5
Observed Events 3 (p=0.3)0 (p=0.11)
1 (p=0.7)BR(D0 → μ+μ-) < 4.3 x 10-7 at 90% CL λ21kλ22k = 1.5√ BR(D0 → μ+μ-) < 9.8 × 10-4
CDF Note 9226
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D+(s)→π±μ+μ-
Orthogonal to B0s→μ+μ-
Effects in up-quark sector
factors of >1000 over SM not ruled out
Long distance resonance production BR = 1.9x10-6
Short distance continuum production
Little Higgs models with new up sector vector quark
Fajfer et al. hep-ph/0511048RPV in the up sector and not the down
sectorBurdman et al. hep-ph/0112235
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Resonant D+(s) Decays
Resonant production Selection of events with
m(μμ) in φ region N(Ds
+) = 254 ± 36 N(D+) = 115 ± 31
Statistical significance 8 for Ds
+ and D+, 4.1 for D+
First observation for Ds First evidence for D+
BR(D+→φπ+→μ+μ-π+) = (1.8 ± 0.5 ± 0.6) x 10-6
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Continuum D+(s) Decays
Exclude resonant φ→μμ mass region 19 candidates in D+
window Background
expectation 25.8 ± 4.6 (p-value=0.14)
Normalize to D+→φπ+
BR(D+→ μμπ+)
< 3.9 x 10-6 @ 90% CL PRL 100, 101801(2008)
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Summary B, D hadron decays provide a Sensitive
Probe of EW Symmetry Breaking & Physics Beyond the SM Allow classes of models to be favored/ruled out Complementary to direct searches for new
particles The CDF and DØ experiments are making
major contributions to CKM measurements World’s best limits in B,D rare decays Complimentary to B factories Adding more data every day
Significant reduction of New Physics parameter space Bounds on general flavor mixing
Paving the way for LHC
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The Tevatron Accelerator
World’s highest energy collider Proton-antiproton
synchrotron Experiments CDF and DØ
Run II (2001-2010?) s = 1.96 TeV Current peak luminosity
L~3 x 1032 cm-2s-1
Expect up to L= ∫Ldt = 8 fb-1 integrated luminosity in Run II
Large pp cross-section High collision rate 1.7 MHz
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D0→μ+μ- Summary
Detector CMU-CMU CMU-CMX CMX-CMX
Combinatorial Background 0.040 ± 0.007 0.008 ± 0.001 0.0007 ± 0.0001
B Decays Involving One Real Muon 0.54 ± 0.06 0.13 ± 0.03 0.07 ± 0.02
B Decays Involving Two Real Muons 3.8 ± 1.3 2.5 ± 1.0 1.0 ± 0.5
Total Expected Background 4.9 ± 1.3 2.7 ± 1.0 1.0 ± 0.5
Observed Events 3 0 1