Heavy Flavour in a Nutshell › presentations › B-physics and...Heavy Flavour in a Nutshell (for a...

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

Flavour physics timeline


THEORY

EXPERIMENT

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


http://arxiv.org/abs/1005.2757�

http://arxiv.org/abs/1102.4274�

http://lambda.gsfc.nasa.gov/product/map/dr4/pub_papers/sevenyear/basic_results/wmap_7yr_basic_results_reprint.pdf�



Light

Rob Lambert, CERN Moriond QCD, 22nd March 2011 4(13.75 ± 0.13) Gyr

Matter


73% Dark Energy

22% Cold Dark Matter

5% Atoms

Antimatter


Matter + Antimatter = photons

Antimatter


CP-violation, CPVobservable difference between

matter and antimatter


Antimatter


( ) 10105.05.5 −×±=γn

nbaryon

You Are Here

2010−<γn

nbaryon

Where did you go?

Guys…? Guys…??

REALITY SM (maximal CPV)





What does that have to do with heavy flavour physics?

A beautiful image


µ-

PV

SV

TV

Bs

Ds+

π+,Κ+,Κ−

EVT: 49700980RUN: 70684

LHCb Preliminary

Heavy flavour is a microcosmof the entire standard model

There are in general two types of new physics searches

Complementarity


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

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!


0sB0

dB0K

0K

0K

(CPLear) (PDG) (PDG)

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?


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


Unlikely: tree-level decays Likely: loops and penguins

0qB 0

qB?

q

q

qq

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


Unlikely: tree-level decays Likely: loops and penguins

0qB 0

qB?

q

q

qq ?

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

CKM - status

Plot everything together on a single graph

Everything is consistent ... so far ...



Hottest new physics searches

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

Looking for flavour (1)

Bd→ K*µµ has both loops and penguins!

Amongst many observables Afb is sensitive to SUSY


e.g.

CDF

SM

BELLE

BABAR


Very rare decays, where SM BR predictions are very good

In the case of Bs/d→µµ, the rate is very sensitive to SUSY


CDF Prelim:

e.g.

LHCb:

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

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

SM is disfavoured by 3.6σ

Owing a lot to the recent D∅ measurement

Status: NP in mixing?



Flavour-specific asymmetry… a smoking gun for new physics??

Surprise!


…

Translate

Very difficult measurement

Observe

Flavour-specific asymmetry from B0-mixing in the SM:

In the standard model afs is almost negligible


)( ++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

Hot Topic


Situation couldreally be clearedup by LHCb

Current status

LHCb is reconstructing both and

LHCb is catching up with D∅ very quickly


~100k Ds in 5 fb-1 ~100k Ds in 0.2 fb-1

µνµ ±→ ss DB0

µνµ ±→ dd DB0

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


( ) 4103.01.22

−×±=−

=∆dfs

sfs

fs

aaA

( )

×±−

+ −4103.00.2~2

~dfs

sfsb aa

ANB: D∅(inclusive)

LHCb(subtraction)

After 1fb-1 of LHCb


LHCb measurement cuts at right-angles to D∅

Only one exampleof the great physicson the way from LHCb

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!


End

Backups are often required


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


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)


https://mmm.cern.ch/owa/redir.aspx?C=e2c84b597bb64d9682dac8b51e5afbe8&URL=http://arxiv.org/abs/1103.2465�

http://dx.doi.org/10.1016/S0370-1573(02)00367-8�

http://ckmfitter.in2p3.fr/�

http://www.slac.stanford.edu/xorg/hfag/rare/ichep10/acp/index.html�


Further introduction

Gravity

Rob Lambert, CERN Moriond QCD, 22nd March 2011 37(13.75 ± 0.13) Gyr

Antimatter


( ) 10105.05.5 −×±=γn

nbaryon 2010−<γn

nbaryon

REALITY SM (maximal CPV)




Mass of entire solar system: 2x1030 kg Mass of largest asteroid, Ceres: 1021 kg

Area ~ Kazakhstan: Population~one small dog

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

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:


CKM - status

Couplings, rates and mixings constrain magnitudes

Asymmetries and mixings constrain phases



Mixing observables

QM 101

The most basic hamiltonian of anything

Because:


XiMXdtdiH XX

Γ−==

2

( ) ( )tiMiHt eetX Γ−−− ~~

Wave-like propagation Decay

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

qq

Γ−=

)()(

2)()(

0

0

0

0

tBtBiM

tBtB

dtdi

q

qqq

q

q

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!


( ) ( )tiMiHtH

HHeetB Γ−−− ~~

( ) ( )tiMiHtL

LLeetB Γ−−− ~~These are the mass-decay-eigenstates

0sB0

dB

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


Flavour-specific asymmetry… a smoking gun for new physics??

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


)( ++µµN ≠ )( −−µµN

++→ µµbb ≠ −−→ µµbb

XBBBBbb ++→⇒ µµ0000 ~ ≠ XBBBBbb −−→⇒ µµ0000 ~

( ) 4103.00.2 −×±−=SM2

dfs

sfsb aa

A+

≈ ( )%3.01±−≈D∅

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:


Γ

≈ SM

SMSM

Ma

12

12Im

Discovery Potential



If we allow a single NP phase in the mixing Θ


Θ

Γ

−Θ

Γ

≈ sinRecosIm12

12

12

12SM

SM

SM

SMNP

MMa

Discovery Potential



If we allow a single NP phase in the mixing Θ (first part is just the SM value)


Θ

Γ

−Θ

Γ

≈ sinRecosIm12

12

12

12SM

SM

SM

SMNP

MMa SM

fsa

Discovery Potential



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 −×


Flavour-specific asymmetryAt LHCb


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


( ) 4103.01.22

−×±=−

=∆dfs

sfs

fs

aaA


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


( ) 4103.01.22

−×±=−

=∆dfs

sfs

fs

aaA

( )

×±−

+ −4103.00.2~2

~dfs

sfsb aa

ANB: D∅


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=)(


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=)(

Simplify

We measure time-dependent decay rates:

Ac, Ap and Afs are correlated and cannot be separately fitted

First, reparameterise


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


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


f

2211,

dfs

sfs

dsds

fs

aaxxA−

=−

=∆ ( ) 45.06.0 105.2 −+

− ×+=SM

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)



LHCb projections

J/ψ Φ


LHCb MC!

K*µµ


BaBar657M bb-pairs

LHCb MC 1fb-1

µµ

LHCb will exclude most SUSY models this year!



Misc


Check loop-level observables

Would need a very accurate determination of dmd/dms


c.f. J/Ψ Φ


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

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Heavy Flavour in a Nutshell › presentations › B-physics and...Heavy Flavour in a Nutshell (for a...

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