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1ITEP Meeting on the future of heavy flavour physics
Experimental methods for precise determination of CKM matrix sides
Marie-Hélène Schune
Member of the BaBar and LHCb collaborations
LAL-Orsay
•Introduction
•Present status • Vtd, Vts :
• B mixing • Rare B decays
•Vcb, Vub : • Semileptonic decays• B
•Charm physics
•Overall status and future• B factories : • LHCb :
• Radiative B decays • Bs mixing
2ITEP Meeting on the future of heavy flavour physics
Introduction
3ITEP Meeting on the future of heavy flavour physics
Mass eigenstates weak interaction eigenstates mixing matrix : the Cabbibo-Kobayashi-Maskawa matrix
Weak interaction eigenstates
Mass eigenstatesCKM matrix
Transition amplitude between the quarks i and j : Vij
b u
W
Vub
Vij complex CP violation
Framework : the CKM matrix
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
d’
s’
b’
=
d
s
b
1-2 A 3(-i)
- 1- 2/2 A 2
A3(1- -i) -A 2 1
+ O(4)
Wolfenstein parametrisation
4ITEP Meeting on the future of heavy flavour physics
3 families + CKM matrix unitarity 4 parameters
Relations between the CKM matrix elements
The unitarity triangle
/2
/1 /3
(,)
(0,0)
(1,0)
*ub
cb
V
V*td
cb
V
V
* * *ub ud tb td cb cdV V V V V V 0
1-2 A 3(-i)
- 1- 2/2 A 2
A3(1- -i) -A 2 1
4 parameters known with different precisions :
=sin(c) ~0.4 %
A ~ 1.7 %
~ 15 %
~ 5 %
CKM : present status
5ITEP Meeting on the future of heavy flavour physics
Some of the experiments
BELLE
CDF D0
BABAR
e+e- (4s)
pp
s=1.96 TeV
LHCb pit june 2006
pp s=14 TeV
6ITEP Meeting on the future of heavy flavour physics
Present status
7ITEP Meeting on the future of heavy flavour physics
Vtd and Vts
top quark couplings
loop or box diagrams
Search for New Physics
Vtb
Vts
b
ds
b
ds
W
W
Vtd
t t
Vtb
Vtd
Vts
Bd,s0Bd,s
0
b
ds
ds
b
W W
Vtb
Vtd
Vts
tVtb
Vtd
Vts
Bd,s0Bd,s
0
B B mixing :
t
Top quark contribution dominates
b
d W , ,t c u0B
d
ds
K*
Radiative B decays
Top quark contribution dominates
8ITEP Meeting on the future of heavy flavour physics
B0-B0 oscillations
( )0 /1( ) 1 cos( )
2 t
q qP t e mB t
Time-dependent probability for a produced at t=0 to be observed as a
or at time t
0qB
0qB
0qB
Can be predicted in the SM framework
0 00 0
2222 2 2
2 26 qq qqB BtF
q tb W Btq BW
fMG
m V V M M B SM
Non-perturbative QCD
perturbative QCD
Reconstruct the decay time (t)
Tag the B production state :
Other B information (B factories and pp colliders)
Same side tagging (for pp colliders only/ Bs)
9ITEP Meeting on the future of heavy flavour physics
B0-B0 Oscillations: md
SU(3) flavour breaking
smaller theoretical uncertainties
HFAG
=1
00
0
0
0
0
0 0
2 2
22d
s
d
ss
d d
s
B B BBtd
B B
d
s Bts B
f B
f
MV
m B
m
MV
md : a high precision measurement (~0.8%) dominated by B factories results
md = 0.5070.004 ps-1
Asy
mm
etr
y
co
s(
mdt)
|t| (ps)
Weak constraint on the UT triangle due to the knowledge of
BELLE 152 106 BB . Full B reconstruction
0 02
d dB Bf B
useDue to the size of the CKM elements ms >> md
10ITEP Meeting on the future of heavy flavour physics
Several analysis from LEP, SLD, Tevatron
Combine different limits : the amplitude method
measurement of A at each ms
At a given ms :• A=0 : no oscillation• A=1 : oscillation
ms excluded at 95% CL : A+1.645A<1
Sensitivity : same relation with A=0
00 1
A( ) 1 cos2
tss sP B B e m t
( )( )
First limit was set in 1993 at ms>1.8 ps-1 at 95%CL !
Bs-Bs oscillations: ms
HFAG
LEP/SLD 1999LEP/SLD 2002
ms : already a high precision measurement (~2.3%)
0.42 -10.2117.33 0.07 pssm
CDF 2006
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Implications of md/ ms measurements on the CKM parameters determinations
Two very precise measurements : (~0.8 % and 2%)
5.9 -14.221.7 pssmIndirect measurement of ms (prediction) :
But it does not translate into a precise determination of the SM parameters …
2
22
s
d
B tss
d B td
m Vmm m V
known to 5-8%
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Radiative B decays
BR(b d ) |Vtd|2
BR(b s ) |Vts|2
b
,u d W , ,t c u
ds
,u d
Semi-inclusive analysis (~55% of the modes reconstructed)
K* peak visible due to the good resolution
New Physics
BF of bs and bd
Standard Model
E spectrum in b s|Vcb| and |Vub|
BF(bs)/BF(bd) |Vtd|2/|Vtd|2
Inclusive photon energy spectrum sensitive to b-quark motion inside B meson
reduces the systematic uncertainty in the Vcb and Vub extractions
bs
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B/
First observation: 5.5
signal
K*other B
2BR( / )
BR( )td
ts
B
B
V
VK
SU(3) breaking correction
weak annihilation diagram for BR(B )
Experiment BF(B )
BaBar (211 x 106 BB)
Belle (386 x 106 BB)
68%CL
95%CL
Full UT fit
0.34 0.10 60.31 0.091.32 10
With the present statistics : use of all the modes, in future only ?
< 1.2 10-6 at 90% CL
Expect new BaBar results at ICHEP
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32
02( , , ) 1
n
QCDl X n
nl X b
f E q m CE q m m
+
Vcb or Vub
Exclusive and inclusive semileptonic approaches : different theoretical uncertainties
Weak decay of a free quark :
2
3
] 5[2
[ ]192
c
b
u bFGb c u m
V
free quark decay Perturbative +non-perturbative corrections
At the hadron level :
Exclusive decays : depend on QCD form factors from eg LQCD, quark models...Inclusive decays : use Heavy Quark symmetry+ OPE
measure OPE parameters from data (spectra and moments of bs and b cℓ distributions)
Complication for charmless decays:
need to apply kinematic cuts to suppress b cℓ background measurements of partial branching fractions in restricted phase space regions
theoretical uncertainties more difficult to evaluate
501
V
V
)clb()ulb(
2cb
2ub
Semileptonic decays: Vub and Vcb
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Vcb inclusive (Buchmüller/Flächer):
Vcb from semileptonic decays
Good agreement
|Vcb|F(1)= (37.60.8)10-3
Vcb exclusive ~5% precision
|Vcb|= (41.960.23exp 0.35HQE0.59SL)10-3
~2% precision
|Vcb|= (41.32.0)10-32
with F(1) = 0.91 0.04theo
Does not contain the latest result from BaBar : |Vcb|=
1.5 3stat exp 1.3theo37.6 0.3 1.3 10
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Vub in inclusive B decaysIn these regions the theory (OPE) breaks down, acceptance sensitive to Fermi motion of b quark inside the B meson
Several approaches :
Method S/B Pros & Cons
UntaggedElectron spectrum endpoint
0.050.2 High statisticsBkg subtraction
UntaggedEe vs q2 neutrino reconstruction
~0.5 High statisticsLower syst. on shape functionsBkg subtraction
Breco TagsmX vs q2 analysis
~2 Low backgroundVery small syst. on SF paramSmall statistics
signal
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B 0 ℓB + ℓ
Vub exclusive : Bℓ Bℓ = missing of the event ; ,E p
[[[[[[[[[[[[[[can add Breco tag to improve S/B
Missing mass2
ℓ
ℓ ℓ
ℓ
Measure the form factor q2 dependance.Compare with theoretical calculations
BF(B ℓ ) precision~8%
Various experimental results in good agreement
signal
Yields :36 -ℓ, 34 0ℓ
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Vub from semileptonic decays summary
Vub inclusive (HFAG) Vub determination from exclusive decays
BF precision~8% but |Vub| precision ~20%
theory dominated
~8% precision
|Vub|~ (4.40.2 0.3 )10-3 inclusive|Vub|~ (3.70.2 0.7 )10-3 exclusive
Understanding of the difference ?
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B
22222 2 4
B2 ubBR( ) 1 f 10 in the SMV8
F B B
B
mG mB m
m In the SM it measures fB |Vub|
Direct measurement of fB when using |Vub| from SL decays (to be compared to LQCD predictions)
Test of NP (e.g.: charged Higgs could enhance BF)
Experimental technique
One B fully reconstructed (hadronic or semileptonic)
Search for in the rest of the event (2)
BR(B) . 104
BABAR 232 106 BB < 2.6 at 90% CL
BELLE 447 106 BB 0.34 0.18
0.28 0.161.06 4.2
Electromagnetic energy not associated with the Btag nor the 0 from the decay (GeV)
b
u
B
WVub
~216 signal events
Using |Vub| from HFAG : 28 20
23 19176 MeVBf
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Charm physics
Measurements of fD+ and fDs
improved prediction of fB/fBs
precise measurements of md and ms
precise determination of Vtd/Vts parameters
+
D BF measurements
Vcd
Extraction of D form factors
Validation of LQCD (DK ℓ )
B form factors (D /ℓ)
precise determination of Vub/Vcb parameters
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Recent lattice result (hep-lat/0506030)
Measuring fD and fDs
Pseudo scalar decay :
222
22 21
18 F D cd
DD
mD G m M V
Mf
Vcd
wave function overlap
CLEO-c 281 pb-1
50 events NBkgd=2.920.50
79223 16 MeV
Df
201 3 17 MeV
D*S DS and normalize to Ds
Ds → signal
N = 489±55Preliminary
stat syst Ds→
LQCD Aubin et al. PRL 95 122002 (2005)
/ 1.25 0.14
as expected from LQCDs
BaBar CLEOD Dff
22ITEP Meeting on the future of heavy flavour physics
Semi-leptonic D decays
DK ℓ form factor : comparison of recent experimental results with LQCD calculation
e
K e
0
0
0
0
(3770)
,
D
D
D
D K eK
0Example: D e
CLEO BF relative to PDG
(~117 events)
Events
/ 1
0 M
eV
U ( = Emiss – |Pmiss| )
CLEO-c
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Overall status and future
24ITEP Meeting on the future of heavy flavour physics
Phases and sides measurements in good agreement
The CKM mechanism works well… NP should appear as correction to this framework
Preferred region using only the sides measurements
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Future from the sides point of view : the B factories
The existing B factories will collect about 1 ab-1 (X2 present samples) per experiment
B measurement will improve confrontation with LQCD predictionsB/ determination will improve Vub analyses will be able to discriminate between theoretical models improved Vub extraction
B factories : charm factories !
Super B factory ? Japanese project, based on KEK2 experience : 40 ab-1 before 2020More futuristic : Italian project (linked to ILC development) : 50 ab-1 before 2015Improvement of all the above points :
• eg : expect few thousands BR(B) signal events !
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Future from the sides point of view : LHCb
Use of radiative B decays :
N/year B/S at 90% CL
BdK* ~0.41% 35k <0.7
Bs ~0.64% 9.3k <2.4
Bd(0) ~0.03% 40 <3.5Analysis complicated by the presence of a 0
Bd0 should be easierBELLE has ~6 signal events in this mode
LHCb 2005-01
But the extraction of |Vtd/Vts| is not completely clean from a theoretical point of view (SU(3) breaking, presence of a weak annihilation diagram in (and not in K*)
Full simulation of bb inclusive events
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Very precise measurement of ms using Bs Ds(KK ) events :
One year of data taking (2fb-1) : 80k fully reconstructed events with B/S~0.3 and (t) ~40 fs
ms (ps-1) 20
stat(ms) (ps-1) 0.011
(ms) will be dominated by the systematics (eg knowledge of the time scale)
LHCb 2003-127
The tagging performances will be checked on data (similar self tagging decay modes, double tagging technique Ksame)
Tag eff (%)
Opposite Side 3.90.3 (1.50.1 CDF)
Same Side 2.10.3(3.40.5 CDF)
Recent NN approaches lead to ~9% for Bs
Expected unmixed Bs Ds sample
in one year of LHCb data taking
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And then …
Preferred region determined by sides measurements
2010 : B factories 2 x 1 ab-1
LHCb : 4 fb-1
Vub ~ 5%Vcb ~ 1%(ms) = 0.3 ps-1
fBBB ~ 5% ~ 3%BK ~ 5%
Lattice QCD < 1° ~ 7 ° ~ 5°(half B-factories/half LHCb)
Experimental inputs
Theoretical inputs
Sides and angles determination of () : similar precision
Hopefully this picture will not be the one we will see in 2010 and sides and angles measurements will be incompatible !
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SummaryB factories : Vcb and Vub determinations
More and more inputs from data to constraint the theory improved Vub and Vcb measurements.
fB extraction from B measurement
Increasing role of charm physics which provide high-quality “lattice calibration” improvement on the precision of the CKM parameters
Hadronic colliders : Very precise measurement of the Bs–Bs mixing frequency
Measurements of BK*, Bs and B/
All modes with neutrinos are difficult in hadronic environment
Many new results expected for ICHEP !
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Backup slides
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bcℓ and buℓ Bd and Bs mixingK : CPV in K decaysBccs : 1 /B// : 2/BDK : 3/
2 sides ; 3 angles aim : to overconstrain this unitarity triangle
precision test of the Standard Model
Constraints in the (,) plane
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The “B” experiments : main characteristics
Experiment Integrated luminosity
Boost Main points
CDF/D0 1.6 fb-12 large bb/had small trigger
bb large
Incoherent production ( extra tagging dilution) All B speciesMany particles not associated with the 2 b hadrons
LHCb 2 fb-1 (/year)
BaBar/BELLE 380+630 fb-1 small bb/had ~ 0.2
Coherent BB production Only B and Bd
BB pair alone
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Experimental techniques at B factories B-Flavour tagging
t=1.6 ps z 200, 250 m
Exclusive B meson reconstruction
/rec tagt t t z c
coherent BB production
Beam Energy-substituted mass Energy difference Event shape*2 *2
ES beam Bm E p * *B beamE E E
(mES) 3 MeV (E) : mode dependent
qq events(q=u,d,s,c)
BB events
Exploit kinematic constraints from beam energies
(4S) rest frame