Recent B physics at D Ø

Brad Abbott University of Oklahoma

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Recent B physics at DØ

Brad Abbott

University of

Oklahoma


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Overview

• CP violation :– BsJ/ – Bs Ds

(*)Ds(*)

– B+ J/ K+

– Latest Bs mixing results

• Spectroscopy:– Bc mass– Bc lifetime

• Upsilon Polarization

} More detail

No time for details (apologies)


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B physics at the TevatronProduce heavier states not currently accessible anywhere else:Bs

0,Bc,B**,Bs**,b,b,b,….

Complementary to B factories at (4S)

Huge production rates (pp bb) ≈ 150 b But also huge backgrounds

Need to design specific B physics triggers

Currently in the realm of precision measurements. Can be competitive with B factories in some B+ and Bd decays

Triggers strongly affect what physics can be done


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DØCollecting data from pp collisions at √s = 1.96 TeV

Tevatron running with peak luminosities of300 x 10 cm-2 s-1 (up to 10 interactions/crossing)

Total delivered ~ 4.2 fb-1, recorded ~ 3.7 fb-1

May record month: Tevatron delivered 221 pb-1

DØ recorded 204 pb-1

Large angle coverageSingle and dimuon triggersChanging solenoid/toroid polarity regularly

(~ 100 pb-1 Run 1)


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CP violation in BS decays

• Trying to understand source of CP violation• Bs system good place to search for new physics• B factories have shown that large (> ~10%)

contributions of new physics are excluded from tree level B+ and B0 decays

• Bs decays much less constrained. • Current experiments do not exclude large

phases from new physics• CP violation in Bs system is expected to be small

in Standard Model. A large CP phase is a possible indication of new physics


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Bs0–Bs

0 Mixing Flavor eigenstates propagate according to the Schrodinger Eq.

Observables

Diagonalizing gives two physically observed“Heavy” and “Light” mass eigenstates


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CP Violation in the Bs0 System

How could new physics affect these phases?

Measure the phase responsible for CP violation in Bs J/ decays

sJ/ ≈ s

NP (if large)

~0.04


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CP Violation in Bs0→ J/ψΦ decays

CP violation becomes observable in these decays due to the interference between the mixing and decay amplitudes.

J/ + is an admixture of states that are both CP(even) and CP(odd)

Angular analysis is used to separate the CP components and measure the lifetimes of each component

Flavor Tagging gives us useful information on the flavor of the produced Bs

0 meson


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Bs0 → J/ψΦ

J/ψ and φ are vector particles and have definite angular distributions for CP-even and CP-odd final states.

Bs → V1 + V2 (J/ψ + φ) Spin 0 → 1 + 1 ℓ = 0,1,2

Parameterized angular decay in the Transversity basis.

Angular dependencies are described in terms of polarization amplitudes:

A0: Both vectors longitudinally polarized (ℓ = 0,2) CP even

A║: Transversely polarized and vectors parallel (ℓ = 0,2) CP even

A┴: Transversely polarized and vectors perpendicular (ℓ = 1) CP odd


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Angular Analysis

J/ψ rest frameφ rest frame


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(Stat + syst)

ΔΓs CP Conservation, φs = 0


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Four-fold ambiguity reduces to two-fold after applying flavor tagging.

Sensitivity to φs

No Flavor tagging

Probability of fluctuation from SM to observation is 6.6% (1.8 )

After flavor tagging

=

90% CL

68% CL


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Angular Fit Projections


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Results with Flavor Tagging

1,2 CP conserving strong phases)


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Br(Bs→Ds(*)Ds

(*) ): theory based analysis:

CP even (5~30%) comparable error band consistent with theory untagged: efficiency,

purity, acceptance simpler measurement

Theory predictionTheory predictionΔΔΓΓss = 0.096 ± 0.039 = 0.096 ± 0.039

(J. HEP. 0706, 072)(J. HEP. 0706, 072)

Flavor Specific: Bs Ds

Direct: Bs J/


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purely CP even !!!(*) (*)s sD D

+ heavy quark (mc→ ∞)+ factorization (2mc→ mb)

0 (*) (*) 1 cos 1 cos2 ( ) CP s s

s s s sL H

Br B D D

Ds(*)Ds

(*) ground states

0 (*) (*)

0 (*) (*)

2 ( )

1 (In SM : 0

)( )s s s s

s s s ss

Br B D D

Br B D D

(Phys. Lett. B 316, 567 (1993))

=

= (s=0)In SM

Ds(*) since cannot distinguish Ds from Ds*undetected particle inDs* Ds/0


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0sB

sD

K1

K2

trigger

0sB

sD

sD

K1

K2

K3

K4

trigger

(*) (*) (*) (*)

(*) (*)

(*

(*

)

) (*) ( ) ( )(

( ) ( )2

( ) (

(

)

)

)

s s s

s

s

s s s

s s s s

s

s

s sBr B Br D Br K KR

Br

D

B D

N B D D B D DR

N B B

D

D D

Sampling: Dsφμ vs. Dsμ

Normalizing: Dsφμ to Dsμ

m(φπ)

N=28,680±288

Ds

D±


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0sB

sD

sD

K1

K2

K3

K4

trigger

2-D Unbinned Loglikelihood FitDs(φ1π) vs. φ(K3K4)

m(φ

1π

)m(K3K4)

Bkg-Sig

Sig-BkgSig-Sig

Bkg-Bkg


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0sB

sD

sD

K1

K2

K3

K4

trigger

2-D Unbinned Loglikelihood FitDs(φ1π) vs. φ(K3K4)

Ds(φ1π)

φ(K3K4)

N(Ds)=31.0 ± 9.4Significance of 3.7


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Peaking backgrounds

• Bs Ds(*)Ds

(*) X ~ 0 % contribution

• B±,0 Ds(*) Ds

(*) KX 5 ± 2% (m(Ds)>4.3 GeV)

• cc Ds(*)X 2 ± 1% (lifetime cut)

• Bs Ds(*)±m()<1.

85 GeV) Peaking backgrounds small


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,1

,1

,1 ,1 ,1

(*) (*)

(*) (*) ( )

( )

( )

a a

c

s s

cc s sc s a a

a a b b c c

f M

N D f M

f M

N D D

N Df f

DM M

a: Bs→Ds

(*)Ds(*)

b: B±,0→Ds(*)Ds

(*)KX c: Bs→Ds

(*)µφ

Mi : total # of events for channel inj : total # of events in j region fi,j : fraction for channel i in region j

pure signal events: N(Bpure signal events: N(Bss00→ D→ Dss

(*)(*) D Dss(*)(*)) = 27.5 ± 9.8 ) = 27.5 ± 9.8


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Sources Uncertainty

Br(Bs0→Ds

(*)μν) 0.0127

Br(Ds→φμν) 0.0047

ε(Ds(*)Ds

(*))/ ε(Ds(*)μν) 0.0072

fitting procedure 0.0071

N(Ds(*)Ds

(*)): Matrix 0.0041

ccbar 0.0011

f(Bs0→Ds

(*)μν) 0.0006

N(Dsμ) 0.0005

Total 0.0174

• poor precision of branching ratios ( ≥ 60 %)• large room for further improvement

• trigger efficiency model dependent calculation

• uncertainty by ccbar contamination is small


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•Br(Bs Ds(*)Ds

(*))=0.042 ± 0.015 (stat) ± 0.017 (sys)

s/s=0.088 ± 0.030(stat) ± 0.036(sys)

Results


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Direct CP Violation

• SM predicts ~ 1% CP asymmetry for B+ J/ K+

• Frequent solenoid and toroid polarity changes allow a control of charge asymmetry systematic uncertainties

• Correct for K+/K- asymmetry

ACP(B+ J/ K+) = +0.0075 ± 0.0061 ± .0027

Factor of 2 better than current world average

hep-ex: 0802.3299


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Update on Bs mixing

• Select Bs candidateLook on the decay mode BsνlDs(φπ)

• For each Bs candidate– BS flavor at decay time from lepton sign at the reconstructed side– Transverse length LT and its error– Transverse momentum PT(Bs) (use PT(Dsl))– B-hadron flavor at the opposite side (indicates BS flavor at production time)

μ+,e+

π -

K+K-

φD-

S

μ(e) B

ν

00ss BB

X

Reconstructed SideOpposite Side

LT

Example from semileptonicdecay


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Amplitude Method

• If mixing signal with Δms, amplitude A=1 otherwise A=0

• Scan Δms, for each value find A ± A

• Plot A for each value of ms

A

cKxΔmec

Kp s

c

Kx

B

oscnoss

sB

s

/cos15.0/ D

s

s

BT

DT

ppK


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Bs mixing results

2.9 significancems=18.53 ± .093 (stat) ± 0.30 (sys) ps-1

0.2018 ±.0053 (exp) ± .0010 (md) + .0078 - .0058 ()


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Spectroscopy: Bc meson

• Bc contains two different heavy quarks (Unique)

• Decays – via b quark:

• Bc+ Bs +, Bs l+

– via c quark• Bc J/ +, J/ Ds

+, J/ l+

– Annihilation• Bc l+

M(Bc+)=6300 ± 14 ± 5 MeV

Mass

Accepted by PRLhep-ex 0802.4258


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Bc lifetime

• Decays – via b quark:

• Bc+ Bs +, Bs l+

– via c quark• Bc J/ +, J/ Ds

+, J/ l+

– Annihilation• Bc l+

Simultaneous fit to massTemplates and lifetime models

Most precise by a factor of 2

(Bc)= 0.444+0.039 + 0.039-0.036 – 0.034

ps

Theory (hep-ph/0308214)(Bc)=0.48± 0.05 ps Submitted PRL

hep-ex 0805.2614


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Upsilon polarizationNon relativistic QCD predicts that the S-wave quarkonium should betransversely polarized at high PT

Dimuon invariant mass fitted in bins of |cos*|(* angle of positive lepton in the quarkonium center of mass frame with respect to the momentumcf the decaying particle in the laboratory frame)

0.4 < |cos *| < 0.5

Good agreement between data (points)and weighted MC(histogram)


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Upsilon polarization Define polarization =(T – 2 L)/(T + 2 L)

Lower purple curve:Kt factorization model with Quark-spin conservation hypothesis

Upper purple curve:Kt factorization model with Full quark-spin depolarization hypothesis

Significant PT dependent longitudinal polarization for (1S) which is inconsistentwith NRQCD predictions

NRQCDCDF

DØ Data

Submitted PRLhep-ex 0804.2799


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Conclusions

• Tevatron doing very well• DØ continuing to collect high quality

physics data• Producing precision measurements

(World’s best) in a number of different areas

• Continue to exploit large luminosities and large number of states produced at Tevatron


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Backup


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CP Violation in the Bs0 System

SM accommodates CPV by introducing a single complex phase in the CKM matrix

Bs0 unitary condition

Im

Re1

VtsVtb*/VcsVcb*

VusVub*/VcsVcb*

Area of triangleproportional to level of CP violation

Vts

CKM Matrix

βs

Vts >> Vub


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CP Violation in Bs0– Bs

0 Mixing

Bs0 Bs

0

b

s

s

b

W

W

u,c,t u,c,t

InterferenceSemileptonic asymmetry

Matter Antimatter

N(Bs0 → D--) vs N(Bs

0 → Bs0 → D--)


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Differential Decay Rate and Amplitudes


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Polarization AmplitudesUpper sign: Time evolution of pure Bs

0 → J/ψΦ at t=0Lower sign: Time evolution of pure Bs

0 → J/ψΦ at t=0


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Polarization Amplitudes (no Flavor Tagging)Assuming equal production rate of Bs

0 and Bs0

Opposite terms vanish, but still sensitive to φs


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Flavor Tagging

Measurement of Bs0 or Bs

0 flavor at production

εD2 for Bs0 → J/ψφ is 4 – 5 %

b quarks produced in pairs


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Universal Trigger Efficiency Curve

Different muon property- Bs

0→Ds(*)μν: primary

- Bs0→Ds

(*)Ds(*)(Ds →φμν):

secondary

dataMC

Normalized signal yield for data and model

( )

( )T Trig

T ZB

p

p

D0 RunII Preliminary (2.8 fb-1)

DO Collaboration MeetingDO Collaboration Meeting May 22, 2008May 22, 2008


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Ms

Recent B physics at D Ø

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