1 rare bottom and charm decays at the tevatron dmitri tsybychev (suny at stony brook) on behalf of...

1

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

FPCP 2008 D. Tsybychev 2

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)


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


Discriminating Variables

Isolation

Flight length significance

impact parameter

significance


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


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


B0(s)→μ+μ- Normalization

Combinatorial backgrounds estimated from fit in mass sidebands and propagated to signal region

BR normalized to B±→J/ψK ±


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!


B0s→μ+μ- Prospects


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)


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


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-


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


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


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


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


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


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)


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

21

BACKUP SLIDES


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


Data Collected


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

1 rare bottom and charm decays at the tevatron dmitri tsybychev (suny at stony brook) on behalf of...

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