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Lifetime and Mixing. Chunlei Liu / University of Pittsburgh On behalf of CDF and D0 collaborations FPCP 2008 May 5-9. Part I Lifetime Motivation and Experiments B 0 s , B c lifetimes Part II Mixing B 0 s mixing from D0 D 0 mixing from CDF. - PowerPoint PPT Presentation
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1/27
Lifetime and Mixing
Chunlei Liu / University of Pittsburgh
On behalf of CDF and D0 collaborations
FPCP 2008 May 5-9
Lifetime and Mixing / Chunlei Liu 2/27
Part I Lifetime Motivation and Experiments B0
s , Bc lifetimes
Part II Mixing B0
s mixing from D0 D0 mixing from CDF
Lifetime and Mixing / Chunlei Liu 3/27
Spectator model: all b hadron lifetimes are equal.
Pauli interference prolongs lifetimes:+5% for B+, +3% for b
Weak annihilation or scatteringreduces lifetimes -7% b
Heavy Quark Expansion (HQE):
Lifetime ratios are better predicted:
(B+)/(B0), (Bs)/B0), (b)/(B0)…
Decay of B Hadrons
kinetic and chromomagnetic operator
weak annihilation and Pauli interference
Lifetime and Mixing / Chunlei Liu 4/27
The Bc Doubly Heavy Meson
• Doubly heavy with b and c quark – interesting lab for studying QCD
• Both quarks decay or annihilate, shorter lifetime than light B mesons
theory prediction:
(Bc) :0.47 0.59 ps
arXiv:hep-ph/0308214v1Phy Rev. D 64, 14003 (2001)Phy Lett. B 452, 129 (1999)hep-ph/0002127 ( and references within)
Lifetime and Mixing / Chunlei Liu 5/27
B0s Lifetime and Decay Width Difference
b ss
cc
W WW
s
B0s →J/
Eigenstates: Bslight and Bs
heavy => L and H
s= (L+H)/2 , = L-H
Two kinds of lifetime measurements:
1) Measure 1/s and directly (need to identify CP eigenstates)
2) Treat L and H together as one exponential, measure e.g flavor specific channel:
Lifetime and Mixing / Chunlei Liu 6/27
Combine s and
: theoretically calculable and sensitive to new Physics
Probe to New Physics : = 2|12|cos(s)
Lifetime and Mixing / Chunlei Liu 7/27
Latest HFAG (by 03/08)
New measurements today:
1) Bs lifetime –direct measurement
2) Bs lifetime – flavor specific
3) Bc lifetime
Theory references:
PRD 68, 114006 (2003)
PRD 70, 094031 (2004)
hep-ph/0705.3802 (2007)
Lifetime and Mixing / Chunlei Liu 8/27
Tevatron • pp collisions at 1.96 TeV
• 3.4 fb–1 data on tape (recorded at D0)
• Initial instantaneous luminosity up to 3x1032cm–2s–1
Main Injector & Recycler
Tevatron
p source
Booster CDFDØ
Apr 2002 – Apr 2008
Lifetime and Mixing / Chunlei Liu 9/27
CDF II Detector DØ Detector
• Central tracking: silicon vertex detector drift chamber
=> pT/pT = 0.0015 pT excellent vertex resolution• Particle identification: dE/dX and TOF
• Excellent muon coverage • Good tracker coverage• Silicon layer 0 installed in 2006 improves
track parameter resolution
tracker
Lifetime and Mixing / Chunlei Liu 10/27
Measure s and from B0s→J/
ct=L/
=Lxy/sin/
=LxyM/PT
CP conservation (s=0)
|BsH> : CP odd eigenstate ~ 25%
|BsL> : CP even eigenstate ~ 75%
S, D waves: CP even
P wave: CP odd
Angular distribution in transversity basis => separate CP eigenstates
Lifetime and Mixing / Chunlei Liu 11/27
Events Selection at CDF/D0
• Di-muon trigger • Neural Network selection at CDF ~ 2500 signal events• Cuts based selection at D0 ~ 2000 signal events
Lifetime and Mixing / Chunlei Liu 12/27
Measure s and
(s=0) =1.52 ± 0.04(stat) ± 0.02(syst) ps =0.08 ± 0.06(stat) ± 0.01(syst) ps-1
World’s best measurement!
Phys. Rev. Lett. 100, 121803 (2008)
(s free)=1.52 ± 0.05(stat)±0.01(syst) ps =0.19±0.07(stat) +0.02
-0.01(syst) ps-1
s=0) =1.53 ± 0.06(stat) ps =0.14 ± 0.07(stat) ps-1
(arXiv:/0802.2255[hep-ex])
Lifetime and Mixing / Chunlei Liu 13/27
Bs Lifetime Measurement from Bs→ Ds+() - X - CDF
fully and partially reconstructed channel such as: Bs→ Ds
-1 (+ 0)
Double statistics!
“K” factor accounts for missing momentum and mass
Extensive test on B0, B+ control samples
x2 stats
Lifetime and Mixing / Chunlei Liu 14/27
Data (1.3 fb-1) collected by displaced-vertex trigger ( 120m<d0<1mm )
~ 1100 fully reconstructed events
~ 2000 partially reconstructed events
=> cut on lifetime ( events with ct<d0 removed)
modeled with “trigger efficiency curve” from MC
Two-step fit, 1)mass fit
=> relative fraction of various modes and background
2) lifetime fit (shape from MC, fraction from mass fit)
=> extract lifetime only
Events Selection and Fit Strategy
Lifetime and Mixing / Chunlei Liu 15/27
Fix fractions from mass fit
(Bs) only free parameter
= 1.518 ± 0.041(stat.) ± 0.025(syst.) ps
(http://www-cdf.fnal.gov/physics/new/bottom/080207.blessed-bs-lifetime/)
Lifetime for control samples:B0→ D-(K+--) + B0→ D*-(D0(K+-)-) + B+ →D0(K+-) +
Agrees well with PDG
Lifetime Result (CDF)
D0 had Bs semileptonic lifetime in 2006 from Bs→Ds
-+X
=1.398±0.044(stat)+0.0280.025(syst) ps
PRL 97, 241801 (2006)
Lifetime and Mixing / Chunlei Liu 16/27
Bc Semileptonic Lifetime
Missing momentum, correct pseudo-lifetime: ct= K x ct*
K= pT(J/ l)/ pT(Bc)
Main challenge is multiple backgrounds:• real J/Ψ + fake lepton• fake J/Ψ + real lepton• real J/Ψ + real lepton → from bb events • prompt J/Ψ + lepton• residual conversion (J/+e only)
Lifetime and Mixing / Chunlei Liu 17/27
Bc→J/++X from D0 (1.35 fb-1)
Mass – lifetime simultaneous fit used to disentangle small signal fraction among large fraction of backgrounds
http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B52/
Lifetime and Mixing / Chunlei Liu 18/27
Bc→J/+l+X from CDF (1.0 fb-1)
Muon channel Electron channel
c=179.1+32.6-27.2(stat) m c=121.7+18.0
-16.3(stat) m
combined (by likelihood):
=0.475+0.052-0.049(stat) ± 0.018(syst) ps
(http://www-cdf.fnal.gov/physics/new/bottom/080327.blessed-BC_LT_SemiLeptonic/)
Lifetime fit only
Lifetime and Mixing / Chunlei Liu 19/27
Combine Bc Lifetime from D0 and CDF
Bc lifetime measurements have been exclusive to Tevatron
Weighted average:=0.459 ± 0.037 ps
Theory prediction:
=0.47 – 0.59 ps
Lifetime and Mixing / Chunlei Liu 20/27
Part I Lifetime Motivation and Experiments B0
s , Bc lifetimes
Part II Mixing B0
s mixing from D0 D0 mixing from CDF
Lifetime and Mixing / Chunlei Liu 21/27
two eigenstates and
ms mH – mL , s ( H + L)/2, L – H
msTheo =19.3 ± 6.4 ± 1.9
(arXiv: 0705.3802/hep-ph)
ms/md |V∝ ts|2/|Vtd|2
HeavysB
LightsB
B0s Mixing
CDF measured at: 17.77 ± 0.10(stat) ± 0.07(syst) ps
Show D0 new result today !
Lifetime and Mixing / Chunlei Liu 22/27
Same SideOpposite Side
ms Measurement Strategy
2 2122
2
ct smS Ssignificance e
S B
D
mtetPt
BBB
cos 12
1000 ,
D
Lifetime and Mixing / Chunlei Liu 23/27
Final States Reconstruction at D0
D0 Run IIa D0 Run IIb innermost layer of silicon added resolution improved
Data collected by inclusive single and di-muon triggers, 2.4 fb-1
Final cuts maximizing S/ sqrt(S+B)
Lifetime and Mixing / Chunlei Liu 24/27
Measure ms at D0
Δms = 18.53 ± 0.93(stat) ± 0.30(syst) ps-1
2.9 significance ( DO conference note 5618) Agrees with what CDF measured in 2006: Δms = 17.77 ± 0.10(stat) ± 0.07(syst) ps-1
Introduce amplitude, P(t) ~ 1 AD cos(mst)Fit for A at different ms
Lifetime and Mixing / Chunlei Liu 25/27
D0 MixingD0 mixing in SM occurs through either: ‘short range’ processes ‘long range’ processes (negligible in SM)
M/ discovered K0 0.474 0.997 1964B0 0.77 <0.01 1987Bs 27 0.15 2006D0 < 0.01 < 0.01 2007
Recent D0 mixing evidence :1) Compare D0 → ππ, KK (CP eigenstates)
with D0 → Kπ ( Belle)
2) Compare doubly Cabibbo suppressed (DCS) D0 →K+π- with Cabibbo favored (CF) D0 →K-π+ (Babar )
Lifetime ratio:
where x=M/ , y=/2, is strong phase between DCS and CF modes
Lifetime and Mixing / Chunlei Liu 26/27
Evidence for D0 Mixing at CDF (1.5 fb-1)
CDF : probe longer D0 lifetime than B factories 3.8 significance comparing DCS D0 →K+π- to CF D0 →K-π+
RD (10-3) =3.04±0.55 x’2(10-3)=0.12±0.35 y’(10-3)= 8.5±7.6
(Phys.Rev.Lett.100:121802,2008 )
Lifetime ratio fit Bayesian probability 1-4 contour: closed circle: best fit value open diamond: highest probability point physically allowed (x’2≥0) cross : no mixing point 3.8
Lifetime and Mixing / Chunlei Liu 27/27
Conclusion
Best Bs and measurement in the world Bc lifetime provide better constraint for theory Bs mixing from D0 confirms CDF measurement D0 mixing evidence from hadron collider Expect new b lifetime result for the summer
Lifetime and Mixing / Chunlei Liu 28/27
Back Up
Lifetime and Mixing / Chunlei Liu 29/27
Angular Analysis in Transversity Basis
● Bs->J/ is P -> VV decay ➔ 3 possible angular momenta:
S, D wave: CP even P wave : CP odd● Separation by angulardistribution
➢ Transversity angles , ,
Lifetime and Mixing / Chunlei Liu 30/27
B0s Systematics and Cross Check
Systematics at CDF: 1) Background angular distribution 2) Mass model 3) Lifetime resolution function 4) B0 cross feed 5) Detector acceptance 6) Silicon detector alignment
Cross check sample at CDF:
B0→J/ K*0 for angular analyis
Lifetime: d= 1.52 ± 0.02(stat) ± 0.02(syst) ps
Systematics at D0: 1) Procedure test 2) Acceptance 3) Reconstruction algorithm 4) Background model 5) Detector alignment
Lifetime and Mixing / Chunlei Liu 31/27
Bs→ J/ angular distribution
Lifetime and Mixing / Chunlei Liu 32/27
B0 → J/ K*0
cd = 456 +/- 6 (stat) +/- 6 (syst) μm
|A0|2 = 0.569 +/- 0.009 (stat) +/- 0.009 (syst) |A|||2 = 0.211 +/- 0.012 (stat) +/- 0.006 (syst) δ|| = -2.97 +/- 0.08 (stat) +/- 0.03 (syst) δ = 2.97 +/- 0.06 (stat) +/- 0.01 (syst) ⊥
Lifetime and Mixing / Chunlei Liu 33/27
Mass components:
Single B templates (MC): (signal): Bs→ Ds() X (bkgd): B0, B+, b
Real D + track (background): template comes from fit to wrong-sign sample
Ds
Fake D + track (background): template comes from D sidebands
Lifetime and Mixing / Chunlei Liu 34/27
Bc Background Summary at CDF
Lifetime and Mixing / Chunlei Liu 35/27
One word about Λb Lifetime Status
x
expected soon x
- DØ measurements are in agreement with the theoretical predictions and with the world average
- CDF measurement in is ~3highw.r.t world average
- Expect CDF measurement updates very soon
decay mode CDF lifetime (ps), 1 fb-1 DØ lifetime (ps), 1.3 fb-1
update expected soon x
Lifetime and Mixing / Chunlei Liu 36/27