heavy flavour in a nutshell - cern · heavy flavour in a nutshell (for a 27 -km annular nut at...
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Rob Lambert, CERN Moriond QCD, 22nd March 2011 1
Heavy Flavour in a Nutshell
(for a 27-km annular nut at 1.8K)
Robert W. Lambert, CERN
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Flavour physics timeline
Rob Lambert, CERN Moriond QCD, 22nd March 2011 2
THEORY
EXPERIMENT
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Outline
1. Welcome to our universe
2. Introduction to flavour physics
3. Hottest new physics searches
4. Flavour-specific asymmetry
Recent papers: D∅ measurement of Ab, 3.2σ deviation from the SM (May 2010)
Evidence for an anomalous like-sign dimuon charge asymmetryPRL. 105, 081801 (2010)
Nierste and Lenz B-mixing update (Feb 2011)Numerical updates of lifetimes and mixing parameters of B mesonshep-ph arxiv:1102.4274
WMAP 7-year sky maps (Feb 2011)Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Sky Maps, Systematic Errors, and Basic ResultsJarosik, N., et.al., 2011, ApJS, 192, 14
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Light
Rob Lambert, CERN Moriond QCD, 22nd March 2011 4(13.75 ± 0.13) Gyr
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Matter
Rob Lambert, CERN Moriond QCD, 22nd March 2011 5
73% Dark Energy
22% Cold Dark Matter
5% Atoms
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Antimatter
Rob Lambert, CERN Moriond QCD, 22nd March 2011 6
Matter + Antimatter = photons
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Antimatter
Rob Lambert, CERN Moriond QCD, 22nd March 2011 7
CP-violation, CPVobservable difference between
matter and antimatter
Matter + Antimatter = photons
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Antimatter
Rob Lambert, CERN Moriond QCD, 22nd March 2011 8
( ) 10105.05.5 −×±=γn
nbaryon
You Are Here
2010−<γn
nbaryon
Where did you go?
Guys…? Guys…??
REALITY SM (maximal CPV)
CP-violation, CPVobservable difference between
matter and antimatter
Matter + Antimatter = photons
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Rob Lambert, CERN Moriond QCD, 22nd March 2011 9
What does that have to do with heavy flavour physics?
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A beautiful image
Rob Lambert, CERN Moriond QCD, 22nd March 2011 10
µ-
PV
SV
TV
Bs
Ds+
π+,Κ+,Κ−
EVT: 49700980RUN: 70684
LHCb Preliminary
Heavy flavour is a microcosmof the entire standard model
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There are in general two types of new physics searches
Complementarity
Rob Lambert, CERN Moriond QCD, 22nd March 2011 11
Precision measurementsDirect Searches
“Old
phy
sics
” pr
evio
us c
ollid
er s
earc
hes
New Physics Scale / Collider Energy1 10000.1
Rare Decays
CP-violating asymmetries
Mixing parameters
CKM measurements
LSP
Higgs
Hidden valley
WIMP/
SMP
4th Gen
Rare Decays
CP-violating asymmetries
Mixing parameters
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Neutral mesons are
“mass-decay eigenstates are not the flavour eigenstates” Probably the weirdest phenomenon in physics!
“neither of those are the CP-eigenstates” CP-violation is very weird in itself Observation of CPV in Kaons in 1964, before any predictions!
Rob Lambert, CERN Moriond QCD, 22nd March 2011 12
0sB0
dB0K
0K
0K
(CPLear) (PDG) (PDG)
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Questions
1. Where is the CP-violation we need?
2. What is the flavour structure of new-physics?
But first we ask ourselves: How can we best look for this new physics, and where?
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Looking for NP
1. Find a place where new physics is unlikely
2. Precisely measure well-predicted observables
3. Find a place where new physics could enter
4. Precisely measure related observables
Rob Lambert, CERN Moriond QCD, 22nd March 2011 14
Unlikely: tree-level decays Likely: loops and penguins
0qB 0
qB?
q
q
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Looking for NP
1. Find a place where new physics is unlikely
2. Precisely measure well-predicted observables
3. Find a place where new physics could enter
4. Precisely measure related observables
Rob Lambert, CERN Moriond QCD, 22nd March 2011 15
Unlikely: tree-level decays Likely: loops and penguins
0qB 0
qB?
q
q
qq ?
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Looking for CPV
SM has only one source of CPV, from the CKM, a phase
Observe this and any NP phase with interference: Need observables with two competing amplitudes
SM phase manifests most obviously in the b-quark system
Measure in many different ways to constrain the same phaseRob Lambert, CERN Moriond QCD, 22nd March 2011 16
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CKM - status
Plot everything together on a single graph
Everything is consistent ... so far ...
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Hottest new physics searches
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Looking for CP (1)
Check CP-violating observables
Disagreement would point to CPV new physics
No hints yet, but the angle γ is not well knownRob Lambert, CERN Moriond QCD, 22nd March 2011 19
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Looking for flavour (1)
Bd→ K*µµ has both loops and penguins!
Amongst many observables Afb is sensitive to SUSY
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e.g.
CDF
SM
BELLE
BABAR
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Looking for flavour (2)
Very rare decays, where SM BR predictions are very good
In the case of Bs/d→µµ, the rate is very sensitive to SUSY
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CDF Prelim:
e.g.
LHCb:
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Looking for CP (2)
CP-asymmetry in decays (Direct CP-violation)
Interesting hint: the B→Kπ “puzzle”
Precision two-body B-decays will be very interestingRob Lambert, CERN Moriond QCD, 22nd March 2011 22
ACP
CP asymmetry
HFAGAugust 2010
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Mixing can be modified in both magnitude and phase
Define a complex number parameter ∆q for the new physics
Just like we did with the CKM Collect all the measurements together Plot all at once in 2D (complex plane)
Looking for both
Rob Lambert, CERN Moriond QCD, 22nd March 2011
0qB 0
qB?
23
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SM is disfavoured by 3.6σ
Owing a lot to the recent D∅ measurement
Status: NP in mixing?
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Flavour-specific asymmetry… a smoking gun for new physics??
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Surprise!
Rob Lambert, CERN Moriond QCD, 22nd March 2011 26
…
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Translate
Very difficult measurement
Observe
Flavour-specific asymmetry from B0-mixing in the SM:
In the standard model afs is almost negligible
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)( ++µµN ≠ )( −−µµN
( ) 4103.00.2 −×±−=SM2
dfs
sfsb aa
A+
≈ ( )%3.01±−≈D∅
b b
c
µ−
c
µ−
ν
CP asymmetry in mixing, afs
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Hot Topic
Rob Lambert, CERN Moriond QCD, 22nd March 2011 28
Situation couldreally be clearedup by LHCb
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Current status
LHCb is reconstructing both and
LHCb is catching up with D∅ very quickly
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~100k Ds in 5 fb-1 ~100k Ds in 0.2 fb-1
µνµ ±→ ss DB0
µνµ ±→ dd DB0
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Experimental Challenge
LHC is a pp-collider, not a pp-collider
LHCb is in the forward region Can’t measure the same thing as D∅ Need a clever new method
Subtract two asymmetries to eliminate systematics
Rob Lambert, CERN Moriond QCD, 22nd March 2011 30
( ) 4103.01.22
−×±=−
=∆dfs
sfs
fs
aaA
( )
×±−
+ −4103.00.2~2
~dfs
sfsb aa
ANB: D∅(inclusive)
LHCb(subtraction)
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After 1fb-1 of LHCb
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LHCb measurement cuts at right-angles to D∅
Only one exampleof the great physicson the way from LHCb
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Summary
? Need new physics to explain the observed universe LHC is a discovery machine Precision measurements complement direct searches
LHCb is the flavour experiment at the LHC B→Kπ, CKM-angle γ, Bs/d→µµ, Bd→K*µµ, Bs→J/ψΦ ...
? We’ve seen a hint of new physics already from D∅ LHCb will make an early complementary measurement
This is only the start of the LHC era, so .... Stay tuned for the latest experimental results!
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End
Backups are often required
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Acknowledgements
Ulrich Kerzel for discussions on two-body B-decays
Guy Wilkinson and Thomas Ruf for their great advice
Johannes Albrecht for discussions on Bs→µµ
The CKM-fitter members of LHCb for updating the βs plot, pointing out to me a long-standing physics goof in our TDR and other publications, and for putting up with my crazy questions about their fitting methods
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Further References LHCb:
Bs→µµ first result: http://arxiv.org/abs/1103.2465 Detector paper: J. of Instrumentation (No. 3 pp. S08005P) “Roadmap” of physics analyses: arXiv:0912.4179
– Chapter 2: γ– Chapter 3: B → Kπ– Chapter 5: Bs/d → µµ– Chapter 6: K* µµ
∆Afs studies: – R.W. Lambert, CERN-THESIS-2009-001– N. Brook et al., CERN-LHCb-2007-054
CPLear: Kaon mixing: Physics Reports, Volume 374, Issue 3, Pages 165-270 (January 2003)
Experimental averages: CKM fitter group : http://ckmfitter.in2p3.fr/ HFAG (B →Kπ): http://www.slac.stanford.edu/xorg/hfag/rare/ichep10/acp/index.html
More on B→Kπ Theory Status: S. Mishima from CKM 2010, arXiv:1101.1501 New Physics : S. Baek et al., arXiv:hep-ph/0412086
CDF Bs/d → µµ : CDF Public Note 9892 (preliminary)
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Further introduction
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Gravity
Rob Lambert, CERN Moriond QCD, 22nd March 2011 37(13.75 ± 0.13) Gyr
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Antimatter
Rob Lambert, CERN Moriond QCD, 22nd March 2011 38
( ) 10105.05.5 −×±=γn
nbaryon 2010−<γn
nbaryon
REALITY SM (maximal CPV)
CP-violation, CPVobservable difference between
matter and antimatter
Matter + Antimatter = photons
Mass of entire solar system: 2x1030 kg Mass of largest asteroid, Ceres: 1021 kg
Area ~ Kazakhstan: Population~one small dog
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CKM and CPV
CPV in the SM is ensconced in a single unitary matrix
The phase is most readily observed in the b-quark systemRob Lambert, CERN Moriond QCD, 22nd March 2011 39
The CKM matrix
Three real parameters
One complex phase violates CP
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Unitarity Triangles
Product of rows and columns are constrained by unitarity
Of the nine relationships, six form a unitarity triangle
The most well-known triangle is:
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CKM - status
Couplings, rates and mixings constrain magnitudes
Asymmetries and mixings constrain phases
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Mixing observables
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QM 101
The most basic hamiltonian of anything
Because:
Rob Lambert, CERN Moriond QCD, 22nd March 2011 43
XiMXdtdiH XX
Γ−==
2
( ) ( )tiMiHt eetX Γ−−− ~~
Wave-like propagation Decay
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Mixing
It’s weird, it’s confusing… it must be quantum mechanics
In the b-system, for example, we have two coupled states
Simplest one-line hamiltonian is now a matrix
Off-diagonal elements provide mixing and interferenceRob Lambert, CERN Moriond QCD, 22nd March 2011 44
0qB 0
qB?
q
q
Γ−=
)()(
2)()(
0
0
0
0
tBtBiM
tBtB
dtdi
q
qqq
q
q
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Mass-decay
So, it’s not a diagonal matrix… OK
let’s diagonalize it to find:
Not the flavour states, a time-dependent mixture of them!
Rob Lambert, CERN Moriond QCD, 22nd March 2011 45
( ) ( )tiMiHtH
HHeetB Γ−−− ~~
( ) ( )tiMiHtL
LLeetB Γ−−− ~~These are the mass-decay-eigenstates
0sB0
dB
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Observables
Four simple observables:1. Average width
2. Average mass
3. Width Difference
4. Mass Difference
And we also have a phase, which violates CP:
All very predictable observables in the SMRob Lambert, CERN Moriond QCD, 22nd March 2011 46
( )
Γ
Γ=Γ−Γ=∆Γ q
qqq
LqHq M12
1212 arg2
2211, Γ+ΓΓ
( ) qqL
qHq MMMm 122=−=∆
2211, MMM +
Γ
= q
qqfs M
a12
12Imand/or
Γ−= q
q
qM
12
12argφ
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Rob Lambert, CERN Moriond QCD, 22nd March 2011 47
Flavour-specific asymmetry… a smoking gun for new physics??
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Translate
1. pp-interactions within a symmetric experiment
2. Correct all experimental biases (magnets, mis-id …)
3. Observe
4. In the SM, the favoured way to make charge asymmetry is if:
5. Which comes from B0-mixing:
In the standard model it is almost negligible
Rob Lambert, CERN Moriond QCD, 22nd March 2011 48
)( ++µµN ≠ )( −−µµN
++→ µµbb ≠ −−→ µµbb
XBBBBbb ++→⇒ µµ0000 ~ ≠ XBBBBbb −−→⇒ µµ0000 ~
( ) 4103.00.2 −×±−=SM2
dfs
sfsb aa
A+
≈ ( )%3.01±−≈D∅
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Discovery Potential
afs is very sensitive to new physics (NP) even if: Tree-level processes are SM-dominated SM flavour structure Unitary CKM
With very weird scenarios (like leptoquarks) Probe NP mixing, interference and/or decays
Usual formula is modified:
Rob Lambert, CERN Moriond QCD, 22nd March 2011 49
Γ
≈ SM
SMSM
Ma
12
12Im
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Discovery Potential
afs is very sensitive to new physics (NP) even if: Tree-level processes are SM-dominated SM flavour structure Unitary CKM
With very weird scenarios (like leptoquarks) Probe NP mixing, interference and/or decays
If we allow a single NP phase in the mixing Θ
Rob Lambert, CERN Moriond QCD, 22nd March 2011 50
Θ
Γ
−Θ
Γ
≈ sinRecosIm12
12
12
12SM
SM
SM
SMNP
MMa
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Discovery Potential
afs is very sensitive to new physics (NP) even if: Tree-level processes are SM-dominated SM flavour structure Unitary CKM
With very weird scenarios (like leptoquarks) Probe NP mixing, interference and/or decays
If we allow a single NP phase in the mixing Θ (first part is just the SM value)
Rob Lambert, CERN Moriond QCD, 22nd March 2011 51
Θ
Γ
−Θ
Γ
≈ sinRecosIm12
12
12
12SM
SM
SM
SMNP
MMa SM
fsa
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Discovery Potential
afs is very sensitive to new physics (NP) even if: Tree-level processes are SM-dominated SM flavour structure Unitary CKM
With very weird scenarios (like leptoquarks) Probe NP mixing, interference and/or decays
If we allow a single NP phase in the mixing Θ (first part is just the SM value)
Up to 200-times the SM!!! [[[ ... still... < D∅ measurement ]]]Rob Lambert, CERN Moriond QCD, 22nd March 2011 52
Θ
Γ
+Θ
Γ
≈ sinRecosIm12
12
12
12SM
SM
SM
SMNP
MMa 5101.2 −× 3100.4 −×
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Flavour-specific asymmetryAt LHCb
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Experimental Challenge
At the LHC we have extra complications in the measurement
Polluting asymmetries, which are all much larger than afs Production asymmetry δp ~(10-2) Detector asymmetry δc ~(10-2) Background asymmetry δb ~(10-3)
Use a, time-dependent, untagged, simultaneous fit to Bs+Bd
Subtract two asymmetries to eliminate detector component
Rob Lambert, CERN Moriond QCD, 22nd March 2011 54
( ) 4103.01.22
−×±=−
=∆dfs
sfs
fs
aaA
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Experimental Challenge
At the LHC we have extra complications in the measurement
Polluting asymmetries, which are all much larger than afs Production asymmetry δp ~(10-2) Detector asymmetry δc ~(10-2) Background asymmetry δb ~(10-3)
Use a, time-dependent, untagged, simultaneous fit to Bs+Bd
Subtract two asymmetries to eliminate detector component
Rob Lambert, CERN Moriond QCD, 22nd March 2011 55
( ) 4103.01.22
−×±=−
=∆dfs
sfs
fs
aaA
( )
×±−
+ −4103.00.2~2
~dfs
sfsb aa
ANB: D∅
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Rob Lambert, CERN Moriond QCD, 22nd March 2011 56
The simple formula
( )( )
qqb
q
qqp
qfs
qc
qfsq
fs SB
ttmaa
tA
+
∆Γ
∆
+−−=
22/coshcos
2222)( δδδ
10-3 -> 10 -5
( ) ( )( ) ( )ff
fftAqfs Γ+Γ
Γ−Γ=)(
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Rob Lambert, CERN Moriond QCD, 22nd March 2011 57
The simple formula
Polluting asymmetries are much larger than afs Detector asymmetry δc ~(10-2) Production asymmetry δp ~(10-2) Background asymmetry δb ~(10-3)
( )( )
qqb
q
qqp
qfs
qc
qfsq
fs SB
ttmaa
tA
+
∆Γ
∆
+−−=
22/coshcos
2222)( δδδ
1//
1)()(
1)()(
0
0
−=
−=
−=
SBSB
ININ
ff
b
p
i
ic
δ
δ
εεδ
10 -2 10 -2 10 -310-3 -> 10 -5
Very Complicated
( ) ( )( ) ( )ff
fftAqfs Γ+Γ
Γ−Γ=)(
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Simplify
We measure time-dependent decay rates:
Ac, Ap and Afs are correlated and cannot be separately fitted
First, reparameterise
Rob Lambert, CERN Moriond QCD, 22nd March 2011 58
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Reparameterise
Just to make it easier to see what we’re doing…
production asymmetry is an initial state asymmetry
Changes the mixing amplitude, does not change the physics
Fit for x1 independently, which now only has detector asym
Rob Lambert, CERN Moriond QCD, 22nd March 2011 59
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The subtraction method
Take Bs/Bd with the same final states ( =KKπ µ)
All production asymmetry is in x2/x3, just throw it away
Measure the difference between Bs and Bd
Rob Lambert, CERN Moriond QCD, 22nd March 2011 60
f
2211,
dfs
sfs
dsds
fs
aaxxA−
=−
=∆ ( ) 45.06.0 105.2 −+
− ×+=SM
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Projections
MC sensitivities, Real data yields and systematics 0.1 fb-1 σ~5x10-3 ... First result (2011) 1.0 fb-1 σ~2x10-3 ... 5σ observation? (2012/2013)
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LHCb projections
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J/ψ Φ
Rob Lambert, CERN Moriond QCD, 22nd March 2011 63
LHCb MC!
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K*µµ
Rob Lambert, CERN Moriond QCD, 22nd March 2011 64
BaBar657M bb-pairs
LHCb MC 1fb-1
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µµ
LHCb will exclude most SUSY models this year!
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Rob Lambert, CERN Moriond QCD, 22nd March 2011 66
Misc
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Looking for flavour (3)
Check loop-level observables
Would need a very accurate determination of dmd/dms
Rob Lambert, CERN Moriond QCD, 22nd March 2011 67
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c.f. J/Ψ Φ
Rob Lambert, CERN Moriond QCD, 22nd March 2011 68
Directly Measure sin φs
σ(φs) = 0.05c in 1 fb-1
Effectively Measures
σ(Θ) = 0.5c in 1 fb-1
But they constrain NP differently Effective power enhanced NB physical limit of afs is at 4x10-3 < current D∅ result!
Φ→ ψ/0 JBs
sfsa
Θ
Γ
−Θ
Γ sinRecosIm
12
12
12
12
MM