experimental methods for precise determination of ckm matrix sides
DESCRIPTION
Experimental methods for precise determination of CKM matrix sides. Introduction Present status V td , V ts : B mixing Rare B decays V cb , V ub : Semileptonic decays B Charm physics Overall status and future B factories : LHCb : Radiative B decays B s mixing. - PowerPoint PPT PresentationTRANSCRIPT
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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
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Introduction
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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
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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
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Some of the experiments
BELLE
CDF D0
BABAR
e+e- (4s)
pp
s=1.96 TeV
LHCb pit june 2006
pp s=14 TeV
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Present status
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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
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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)
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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
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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
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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
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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