b hadron mixing and lifetimes

Lepton-Photon 2007 Mike Hildreth – B-mixing and Lifetimes

B Hadron Mixing and B Hadron Mixing and LifetimesLifetimes

Mike Hildreth

UniversitUniversitéé de Notre Dame du Lac de Notre Dame du Lac

XXIII Lepton-Photon SymposiumXXIII Lepton-Photon Symposium

Daegu, KoreaDaegu, Korea

August 13-18, 2007August 13-18, 2007


OverviewOverview

What are we after here?

• b, c Quark Production– details of QCD, parton luminosities, fragmentation functions

• b, c Hadron Masses• b, c Hadron Lifetimes• b, c Hadron Decays

Tevatron and B-Factories Largely Complementary

Tests of, inputs to HQE, CKM

Extraction Extraction of CKM of CKM ParameterParameterss

Heavy Quark Expansion


Tevatron Collider DetectorsTevatron Collider Detectors

Silicon

Central TrackerLumi

Monitor

TOF

Solenoid

Central Calorimeter (E/H)Central

Muon

Wall Calorimeter (H)

Plug Calorimeter (E/H)

Forward Muon

Forward Calorimeter (E)

• Excellent Muon Coverage ||<2

• L1 triggers....

• Excellent Tracking Coverage ||<3

DØ:

• Excellent Mass Resolution

• Particle ID: TOF and dE/dx

• Two-track transverse mass trigger @ L1

• Impact Parameter Trigger @ L2

CDF:


DatasetsDatasets

Tevatron:• ~3.3 fb-1 delivered to each

experiment, ~2.8 fb-1 on tape

• Peak lumi ~ 3x1032/cm2/s– up to 10 interactions/x-ing

• Summer results include up to 2.4 fb-1 (May 30, 2007)

Tevatron Integrated Luminosity

Inte

grat

ed L

umin

osity

[fb-1

]

B-Factories:• Belle: ~700 fb-1

• Babar: ~ 500 fb-1 1fb-1 = ~106 Bs

• Peak luminosity:– 1.7x1034/cm2/s

(KEKB)– 1.2x1034/cm2/s

(PEPII)


Heavy Quark Expansion: LifetimesHeavy Quark Expansion: Lifetimes

• HQE: no leading order corrections 1/mQ

– General feature of QCD gauge structure

– hadronization and bound state effects given in terms of local HQ operators Same operators used for CKM analyses!

• Precise predictions possible:

– verification tests calculational validity of HQE, supplies needed input for extraction of CKM parameters

mesons vs. baryons, (1%)

B0 vs. B+ vs. Bs, (3-20%)

0(B ) / (B ) 1.06 0.02 s0

(B )1 0.01

(B )

0

b( ) / (B ) 0.88 0.05 e.g. Tarantino; Gabbiani, Onishchenko, Petrov

e.g. Gabbiani, Onishchenko, Petrov

evaluation of QCD/mQ terms requires knowledge of light quark dynamics in the presence of the heavy quark field

Bigi, Shifman, Uraltsev, Vainshtein


bb Lifetime Lifetime

• One of the un-solved mysteries of HF lifetime measurements– long-standing discrepancy between theory and measurement

– recent HQE calculation refinements

• inclusion of sub-leading spectator

terms

• inclusion of NLO and 1/mb

spectator effects

– lowered expected value of

• at time of HFAG 2006, theoretical predictions and experimental results agreed within ~1.2

• more accurate results needed for thorough test of theory

Updates of precision b lifetime measurements from CDF, DØ

C. Tarantino hep-ph/0702235

bm4(1/ )

b dB( ) / ( )


bb Lifetime Measurements Lifetime Measurements

DØ (1.2-1.3 fb-1)• fully-reconstructed bJ/

• semi-leptonic mode bc

• similar topology control modes:– B0J/ Ks (all-charged)

– BsJ/ (all-charged)

– B0, B+DX (semi-leptonic)

– BsDsX (semi-leptonic)

• Lifetime from or c vertex

CDF (1 fb-1) (Preliminary)

• fully reconstructed bJ/

• similar topology control modes:– B0J/ Ks

– B0J/ K*– B+J/ K+

– BsJ/

• Lifetime from vertex

hep-ex/0706.2358

hep-ex/0704.3909

PRL 97, 241801 (2006)

PRL 94, 182001 (2005)

PRL, 94, 042001 (2005)


bbJ/J/ Lifetime Measurements Lifetime Measurements

CDF:• reoptimization and detailed study of

resolution functions for J/and vertexing

• Results:

DØ:• extensive studies of non-prompt

backgrounds

• Results:


bbcc Lifetime Measurement ( Lifetime Measurement (DDØ)Ø)

• main issue: huge background after selection of the cfinal state

cut

Likelihood for signal selection developed from data:

B0 DX, DKsBs DsX, DsKsK

full sample: 4437±329 events

B0/B+/BsD+, D+Ks

• 2 fit in bins of decay length– Nsignal, Nbkg, errors determined from mass fits

• mass and width held constant

• Global fit uses lifetime pdf to extract b lifetime from number of signal events/bin


bb Lifetime: Summary Lifetime: Summary

• Lifetime Cross Checks:

DØ Run II (02-06)1.501±0.078±0.050 ps

not in average

PDG 2006


bb Lifetime: Summary Lifetime: Summary

not in average

PDG 2006PDG 2007

not in average

Tevatron: more statistics definitely coming... LHCb will certainly contribute


B Meson MixingB Meson Mixing

• For neutral B Mesons, Weak Mass CP eigenstates– time-dependent evolution

– three observables characterize system:

• m = MHML ~ 2|M12|

• CP = even odd ~2|12|

• = arg(12/M12)

relates mass and CP eigenstates through s = LH = CPcoss

• Mixing Measurements in Bd and Bs systems access to CKM elements

iM iM

i

B Bi

BMt iMB

12 12

12 12

0 0

0 0

2

2

2

2

s

d d d

s sB B

d B B B

tsBs

tdm m

m f

f

B

B

VmV

2

2

2

sensitive to New Physicsnot sensitivesensitive to New Physics

• md well-measured: 0.509±0.004 ps-1

• many uncertainties cancel in ratio


Quantum EntanglementQuantum Entanglement

• Belle: EPR tests of quantum coherence of Y(4S)– measurement of flavor asymmetry vs t can distinguish between

models suggesting different degrees of coherence

• essentially, test levels of coherence with t

– true Bell’s inequality test impossible due to short B lifetime, passive nature of flavor measurement

Quantum Mechanics:

Spontaneous Decoherence:

Local Realistic Model:

Models of decoherence include dependence on the absolute times of the decays, instead of a pure t form

Rev. Mod. Phys. 64, 339 (1992)

Eur. Phys. J. C. 14, 469 (2000)


Quantum CoherenceQuantum Coherence

• flavor asymmetry studied in bins of t (~150fb-1)– high-purity flavor tags used to optimize sensitivity to deviations

– backgrounds and mistags subtracted bin-by-bin, deconvolution used to extract true asymmetry distribution

– weighted least-squares fit to the different models for A, including a term containing world-average md

• Belle/BaBar values assuming QC excluded

• QM favored over SD by 13, over PS by 5.1 – additional fit for fraction of instantaneous decoherence yields

, consistent with no decoherence

QM SD PS


• If there is no direct CP violation in the Bs system, semi-leptonic decays are a direct tag of the flavor state:

• CP-violation in mixing can then be explored using decay asymmetries:

• In fact, a flavor tag of the initial state is unnecessary, use untagged:

• Since the state is untagged, measurement of oscillation is also unnecessary; use time-integral of distribution:

• ASL is the time-integrated untagged asymmetry

Leptonic Decay Asymmetries in BLeptonic Decay Asymmetries in Bss

SM: aSL = (0.21± 0.04)∙10-4 sensitivity to New Physics


AASLSL in B in Bss Decays Decays

• DØ Analysis: Use BsDsX, Ds , KK (1.3 fb-1)

– Experimentally,

– Break data set into 8 equal portions based on muon direction(), muon toroid polarity(), solenoid polarity, and muon charge(q)

– Fit separately for Ds, D, and background components from sidebands to extract physics and detector-induced asymmetries

•

• background fits consistent with 0

• correcting for flavor composition:

yields

PRL 98, 151801 (2007)

(constraints on s will be discussed later)


BBss Mixing Measurements at the Tevatron Mixing Measurements at the Tevatron

• Time-dependent flavor evolution of Bs measured directly

• Three ingredients:– measurement of production flavor

• various indirect techniques based on properties of associated fragmentation and decay products

– measurement of decay flavor

• flavor-specific final state or lepton decay flavor

– proper time of decay

• position resolution of tracking system

• momentum resolution critical for

background suppression

cm

VPDLDØ MC Bs→

DØ: new inner Si layer <>=48m

DØ: old <>=67m

CDF: Ds <>=45m

CDF: Ds <>=26mms = 17 ps-1

Bs Lifetime

t (lifetimes)


BBss Mixing Measurements: final states Mixing Measurements: final states

• Semi-leptonic:– most numerous, but missing

neutrino spoils proper time resolution

• Specific Hadronic Final States:– all-charged final states give

excellent vertex resolution

2.4 fb-1

CDF Run II

DsX Ds Ds3

CDF (1fb-1) 61,500 4100 1500

DØ (2.4 fb-1) 64,100 200*

part. rec.

3100

New Analysis

Data Samples:

*all muon-tagged


BBss Mixing Measurements: flavor tag Mixing Measurements: flavor tag

• No luxury of coherent B0-B0 initial state for flavor tagging– need to use as much information as possible in the event to determine

production flavor

– Figure of Merit: D2 efficiency of tag x (dilution factor)2

final state tags decay flavor

• Kaon flavor: bcXK

• lepton flavor: bX, but bcX+

• jet charge: momentum-weighted charge of initial fragmentation tracks

• Kaon flavor: strange quark not included in Bs forms Kaon

CDF achieved: D2 = 1.8% (OST)

D2 = 3.7% (SSThad), 4.8%(SSTlep)


CDF ResultsCDF Results

semi-leptonic

BsDs

combined

PRL 97, 242003 2006


DDØØ Results Results

• Numerous improvements to analysis– combined OS+SS Tagging (D2 = 4.49%)

– more refined momentum determination for semi-leptonic decays

– track-by-track resolution rescaling

• Addition of new innermost tracking layer for Run IIb

3.1 statistical significance

DØ Run II PreliminaryDØ Run II Preliminary


• First study of CP violation in the Bs mixing (sensitive to New Physics!?)– define Heavy (H, CP-odd) and Light (L, CP-even) Bs states:

– H and L are partial widths, sLH, s=1/2(H+L)

– Differential decay rate (Lifetime difference!):

– s 0 new CP-violation; expected SM value is very small

( , , )

CP-even angular configurations (L=0, 2)

CP-odd angular configuration (L=1)

ss//s s and and ss

;


ss//ss Measurements Measurements

Strategy: • Choose decay with definite CP states: BsJ/, J/+, K+K

– Vector mesons in final state are CP-odd (L=1) or CP-even (L=0,2)

– rate depends on relative orientation

of meson polarization

• time-dependent angular

distributions allow separation of

BsLand sH components

• Simultaneous fit to lifetimes,

angle space

– modifications of angular distributions

due to acceptance effects taken

from MC models



New Measurement from CDF:– very loose pre-selection

– Neural Net used to maximize S/S+B; ~2500 BsJ/ decays

(s = 0)

1.52 ± 0.04 ± 0.02cf. DØ:

PRL 98 , 121801 (2007)



• CDF Angular projections:

• Similar Results from DØ PRL 98 , 121801 (2007)

(Note: DØ plots have signal content enhanced with lifetime cuts)


Constraints on Constraints on ss

• CDF– allowed region in s plane

determined by frequentist method to account for biases at low values of or s

contours

• DØ:– combined constraints from

BsJ/, semileptonic charge asymmetry, lifetime, CDF ms

hep-ex/0702030


Conclusions & OutlookConclusions & Outlook

• Incredibly rich menu of B physics on offer• mature experiments at Tevatron and B-Factories

– sophisticated techniques emerging to extract the most information available from the data

– HUGE datasets, with more to come– largely complementary in focus, scope

• Exploration of flavor sector with unprecedented detail– see following talks...


Backup SlidesBackup Slides


Quarkonia: Upsilon PolarizationQuarkonia: Upsilon Polarization

• Non-relativistic QCD (NRQCD) predicts significant polarization at high pT

– Production described by short distance cross sections non-perturbative matrix elements for evolution to quarkonium state.

– color octet modes required on top of color singlet to describe production (demonstrated by CDF in Run I)

• New results from DØ: (1S) and (2S) production, final state– measurements of polarization in rest frame of Y:

Bodwin, Braaten, Lepage, PRD51, 1125 (1995)

Cho, Wise, PLB 346, 129 (1995)

Braaten, Fleming, PRL74, 3327 (1995)

T L

T L

2

2where fit cos* distribution in bins

of pT to extract

NRQCD prediction

NRQCD prediction

kT factorization models

CDF Data (PRL 88 161802 (2002))

DØ Data


Belle: Y(5S) StudiesBelle: Y(5S) Studies

• Belle took 23.6 fb-1 at the Y(5S) in 2006– fs = (18 ± 1.3 ± 3.2) % (earlier results from 1.86fb-1)

– [PRL 98 (2007) 052001, PRD 76 (2007) 012002]

• New results on inclusive Bs semi-leptonic decays

– inclusive spectra not accessible at the Tevatron

s s s sN B B N B B* * (*) (*) 79( ) / ( ) (97 1)%

Belle Preliminary

23.6 fb-1

Belle Preliminary

23.6 fb-1

sB e XsB X

sBr B X e( ) (10.9 1.0 0.9)% sBr B X( ) (9.2 1.0 0.8)%

Combined Result:

sBr B X( )

(10.2 0.8 0.9)%

c.f. the B0 system:d

dBr B X0( )

(10.33 0.28)%(PDG 2007)

(see results on rare Bs decays later...)

b hadron mixing and lifetimes

Documents

b hadron mixing

lbjyl lifetime measurementscdf

c hadron lifetimesb

c hadron massesb

c hadron decaystevatron

heavy quark fieldbigi

ckm analyses

signal selection