Lepton-Photon 2007Mike Hildreth – B-mixing and Lifetimes B Hadron Mixing and Lifetimes Mike Hildreth Université de Notre Dame du Lac

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

B Hadron Mixing and LifetimesB Hadron Mixing and Lifetimes

Mike Hildreth

UniversitUniversitéé de Notre Dame du Lac de Notre Dame du Lac


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

• Excellent Tracking Coverage ||<3

• Impact Parameter Trigger @ L2

DØ:

• Excellent Mass Resolution

• Particle ID: TOF and dE/dx

• Two-track invariant mass trigger @ L1

• Impact Parameter Trigger @ L2

CDF:


B-Factory DetectorsB-Factory Detectors

1. Silicon Vertex Detector2. Central Drift Chamber3. Aerogel Cerenkov Counter4. Time of Flight Counter5. CsI Calorimeter6. KLM Detector7. Superconducting Solenoid8. Superconducting Final

Focussing System

• Excellent Mass Resolution

• Excellent EM Energy Resolution

• Excellent Particle ID (TOF/aerogel/DIRC)

Common Features:

• Coherent B-B production

• Beam constrained mass excellent background rejection

(4s) Running:


DatasetsDatasets

Tevatron:• >3 fb-1 delivered to each

experiment

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

• Summer results include up to 2.4 fb-1

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 Flavor Factories: Heavy Flavor Factories:

• Tevatron Cross Sections:– central (|y|<1) b’s at 10kHz

– central charm at 500kHz

– ~9x1010 b’s already in Run II

– ~6x1012 charm hadrons

~ infinite statistics for some studies

If you can trigger... (S/N ~ .006)– muon triggers, all-charged modes

CDF 360 pb-1

• B-Factory Cross Sections:– B’s at ~ 50 Hz

– clean initial state

• E(Y(4S))/2 – MB ~ 300MeV

– ~no extra particles

– “easy” B selection

– coherent B-B production

• “automatic” flavor tagging

even works at Y(5S):

Belle

s sB D MC


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...)


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 )

0b( ) / (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)• all-charge decay mode bJ/

• semi-leptonic mode bc

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

– B0D*X (semi-leptonic)– B+D0X (semi-leptonic)

– BsDsX (semi-leptonic)

• Lifetime from or c vertex

CDF (1 fb-1)• all-charge decay mode bJ/

• similar topology control modes:– B0J/ Ks

– B0J/ K*– B+J/ K+

– BsJ/

• Lifetime from vertex


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:

N(J/) = 171


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 proper 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

more statistics definitely coming...


B Hadron MixingB Hadron Mixing

• For neutral B Hadrons, 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

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

Quantum Mechanics:

Spontaneous Decoherence:

Local Realistic Model:


Quantum CoherenceQuantum Coherence

• Fits of flavor asymmetry to different coherence models– spontaneous decoherence disfavored by 18, local reality model

disfavored by 5.1


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

• hardest part of measurement

• 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


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:


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


DDØØ Results Results

• Numerous improvements to analysis– combined “event charge” flavor tag (D2 = 4.49%)

– more refined momentum determination for semi-leptonic decays

– event-by-event resolution rescaling

• Addition of new tracking layer for Run IIb

3.1 statistical significance

DØ Run II PreliminaryDØ Run II Preliminary


constraints on new physics in B-mixingconstraints on new physics in B-mixing


• First Tevatron measurement with direct bearing on CP violation in the Bs system (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



• CDF Angular projections:

• Similar Results from DØ PRL 98 , 121801 (2007) (Lifetime-enhanced 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 assymetry, ms

hep-ex/0702030

Documents

Lepton-Photon 2007Mike Hildreth – B-mixing and Lifetimes B Hadron Mixing and Lifetimes Mike Hildreth Université de Notre Dame du Lac