Flavour - PowerPoint Presentation

Slide1

Flavour Physics with LHCb“When Beauty Decays and Symmetries Break”

Seminar RuGMarch 31, 2008Marcel MerkNikhef and VU

31-3-2008

1

Contents:

CP

violation

with

the CKM matrix Bs meson and “new physics” B-physics with the LHCb detectorSlide2

LHCbATLASCMSALICECERNSlide3

LHC: Search for physics beyond Standard Model31-3-20083 Atlas/CMS: direct observation of new particles LHCb: observation of new particles in quantum loopsLHCb is aiming at search for new physics in CP violation and Rare DecaysFocus of this talkAtlas

CMSLHCbSlide4

Flavour physics with 3 generations of fermions31-3-20084udcstbI

IIIII

e

t

m

n

e

n

m

n

t

quarks

leptons

~0

1777

106

~0

~0

0.511

120

4300

176300

1200

~7

~3

LEP 1

2 neutrino’s

3 neutrino’s

4 neutrino’s

measurements

Beam energy

(

GeV

)

Cross section

Note

:

In the Standard Model 3

generations

of

Dirac

particles

is the minimum

requirement

to

create

a matter - antimatter

asymmetry

.Slide5

Quark flavour interactions31-3-20085 Charged current interaction with quarks: Quark mass eigenstates are not identical to interaction eigenstates: In terms of the mass eigenstates the weak interaction changes from:

u, c, td, s, b

W

g

weak

JSlide6

Quark flavour interactions31-3-20086 Charged current interaction with quarks: Quark mass eigenstates are not identical to interaction eigenstates: In terms of the mass eigenstates the weak interaction changes to:Cabibbo Kobayashi Maskawa quark mixing matrix

u, c, t

d, s, b

W

g

weak

JSlide7

The CKM Matrix VCKM31-3-20087Slide8

The CKM Matrix VCKM31-3-20088

db

d

c

V

cb

Typical

B-meson

decay diagram:The B-meson has a relatively long lifetime

of 1.5

ps

Related

to

mass

hierarchy

?Slide9

The CKM Matrix VCKM31-3-20089From unitarity (VCKM V†CKM=1) :CKM has four free parameters: 3 real: l (0.22) , A ( 1), r 1 imaginary: ih

Particle → Antiparticle: Vij → Vij*=> 1 CP Violating

phase!

Wolfenstein

parametrization: VCKMSlide10

The CKM Matrix VCKM31-3-200810From unitarity (VCKM V†CKM=1) :CKM has four free parameters: 3 real: l (0.22) , A ( 1), r 1 imaginary: ih

Particle → Antiparticle: Vij → Vij*=> 1 CP Violating

phase!

Wolfenstein

parametrization: VCKMSlide11

Unitarity Triangle: VCKM V†CKM = 1 31-3-200811Slide12

Unitarity Triangle: VCKM V†CKM = 1 31-3-200812

0

1

Im







Re

Unitarity

triangle

:

Individual

CP

violating

phases

in CKM are

not

observable

The

combinations

a

,

b

,

g

are

Amount

of CP

violation

is

proportional

to

surface

of the

triangleSlide13

0

+



Re





:

B

d

mixing phase



:

B

s

mixing phase



:

weak decay phase

0

1

Im







Re

Im

Precise determination

of parameters through

study of B-decays.

Unitarity

Triangle

and

B-physics

Slide14

Benchmark Example: Bs→Ds K31-3-200814Slide15

Benchmark Example: Bs→Ds K31-3-200815 But how can we observe a CP asymmetry? Decay probabilities are equal? No CP asymmetry??Make use of the fact that B mesons “mix”…..

Decay amplitudes: particles:antiparticles:Slide16

Sept 28-29, 200516B meson Mixing DiagramsDominated by top quark mass:db

bd

W

u,c,t

u,c,t

W

B

d

B

d

A

neutral

B-meson

can

oscillate

into

an

anti

B-meson

before

decaying

:Slide17

Sept 28-29, 200517B0B0 Mixing: ARGUS, 1987First sign of a really large mtop!Produce a bb bound state, (4S),in e+e- collisions: e+e-  (4S)  B0B0 and then observe:~17% of B0 and B0 mesons oscillate before they decay Dm ~ 0.5/ps, tB ~ 1.5 psIntegrated luminosity 1983-87: 103 pb-1Slide18

Bd vs Bs mixing31-3-200818dbbd

W

t

t

W

Bd

B

d

The top quark and

its interactions can be studied without producing it directly!

s

s

b

d

W

t

t

W

B

s

B

s

B

d

→

B

d

B

d

→

B

d

B

d

mixing

B

s

mixing

B

s

→

B

s

B

s

→

B

s

B

s

mixingSlide19

The CP violating decay: Bs→Ds K31-3-200819Due to mixing possibility the decay Bs→Ds K can occur in two quantum amplitudes:a1. Directly:a2. Via mixing:Coupling constant with CP odd phase gHow do the phase differences between the amplitudes lead to an

observable CP violation effect…?

In

addition

,

mixing

and gluon interactions add a

non-CP violating phase “

d” between a1 and

a2Slide20

Sept 28-29, 200520Observing CP violation|A||A|  Only if both g and d are not 0BDs+ K−BDs− K+A=a1+a2A=a1+a

2dd

+

g

-

g

a

1

a

1a2a

2

A

A

Compare the |amplitude| of the B decay versus that of anti-B decay;

g

is the CP odd phase ,

d

is a CP even phase

Note for completeness

: since the CP even phase depends on the mixing

the CP violation effect becomes

decay time dependentSlide21

Double slit experiment with quantum waves31-3-200821

B

s

D

s-

K

+

LHCb

is a completely analogous interference experiment using B-mesons…Slide22

6-sept-2007Nikhef-evaluation22“slit A”: A Quantum Interference B-experimentpp at LHCb:100 kHz bbDecay time

B

s

D

s

-

K

+

“slit B”:

Measure decay timeSlide23

6-sept-2007Nikhef-evaluation23CP Violation: matter – antimatter asymmetry

BsDs-

K+

An interference pattern:

Decay time



Decay timeSlide24

6-sept-2007Nikhef-evaluation24BsD

s+K-

B

s

D

s

-

K

+

Matter

Antimatter

CP-mirror:

Difference between curves is proportional to the phase

g

Decay time

Decay time



Decay time

An interference pattern:

CP Violation: matter – antimatter asymmetry

CP Violation: matter – antimatter asymmetry

Observation of CP Violation is a consequence of quantum interference!!Slide25

6-sept-2007Nikhef-evaluation25Searching for new virtual particlesStandard Model

B

s

J/

y

f

Standard Model



Decay timeSlide26

6-sept-2007Nikhef-evaluation26Searching for new virtual particlesStandard ModelNew Physics

B

s

J/

y

f



Decay time

Tiny

weak

phase

in

couplings

!

Possible

weak

phase

in

couplings

!

?Slide27

6-sept-2007Nikhef-evaluation27Searching for new virtual particlesStandard ModelNew PhysicsMission:To search for new particles and interactions that affect theobserved matter-antimatter asymmetry in Nature, by makingprecision measurements of B-meson decays.B->J/yfB->J/yf

B

s

J/

y

f

Search for a CP asymmetry:



Decay time

?Slide28

31-3-200828+First sign of New Physics in Bs mixing?SM box has (to a good approx.) no weak phase: fSM = 0

S.M. N.P.

?Slide29

31-3-200829+First sign of New Physics in Bs mixing?SM box has (to a good approx.) no weak phase:

fSM = 0If fS ≠ 0 then new physics outside

the CKM is present…

S.M.

N.P.

UTfit

collab.; March 5, 2008Combining recent

results of CDF, D0 on

with Babar, Belle

results:March 5,2008

?

3.7

s

deviation

From

0Slide30

The LHCb experimentLHCbATLASCMSALICEqbqb

LHCb experiment:

700

physicists

50

institutes

15

countriesSlide31

LHCb experiment in the cavern31-3-200831Shielding wall(against radiation)Electronics + CPU farmOffset interaction point (to make best use of existing cavern)Detectors can be moved away from beam-line for accessSlide32

b-b detection in LHCb31-3-200832LHCb event rate: 40 MHz1 in 160 is a b-bbar event 1012 b-bbar events per yearBackground SupressionFlavour taggingDecay time measurement vertices and momenta reconstruction effective particle identification (π, К, μ, е, γ) triggersSlide33

33GEANT MC simulationUsed to optimise the experiment and to test measurement sensitivitiesSlide34

34A walk through the LHCb detectorpp~ 200 mrad~ 300 mrad (horizontal)10 mradInner acceptance ~15 mrad (10 mrad conical beryllium beampipe)Slide35

LHCb Tracking: vertex region31-3-200835Vertex locator around the interaction regionSilicon strip detector with ~ 30 mm impact-parameter resolutionSlide36

36Pile-Up StationsInteraction Regions=5.3 cmLHCb tracking: vertex region

yx

y

xSlide37

37LHCb tracking: momentum measurement 

By[T]

Bfield:

B dl = 4 Tm

Tracking: Mass resolution for background suppression in

eg. D

sKSlide38

38LHCb tracking: momentum measurement All tracking stations have four layers:0,-5,+5,0 degree stereo angles.

Silicon: ~1.41.2 m2

Straw tubes

~6



5 m

2Slide39

39~1.41.2 m2Red = Measurements (hits)Blue = Reconstructed tracksEff = 94% (p > 10 GeV)

Typical Momentum resolution dp/p ~ 0.4% Typical Impact Parameter resolution

sIP

~ 40 mm

LHCb tracking: momentum measurement Slide40

40LHCb Hadron Identification: RICH3 radiators to coverfull momentum range: Aerogel C4F10 CF4RICH2: 100 m3 CF4 n=1.0005RICH: K/p separation e.g. to distinguish Dsp and DsK events.

RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014

Cerenkov

light

emission angleSlide41

41LHCb calorimetersehCalorimeter system : Identify electrons, hadrons, neutrals Level 0 trigger: high electron and hadron Et (e.g. Ds K events)Slide42

42LHCb muon detectionmMuon system: Identify muons Level0 trigger: High Pt muons Slide43

View of LHCb in Cavern31-3-200843VELOMuon detCalo’sRICH-2MagnetOTRICH-1

VELO

Muon

det

Calo’s

RICH-2

Magnet

OT

RICH-1

It’s

full!

Installation

of major structures is essentially completeSlide44

Hope to soon see the first events from…31-3-200844Slide45

31-3-200845Display of LHCb simulated event Slide46

46Prepare Bs→DsK Reconstruction… Trigger : ET Calorimeters, Vertex topologyFlavour Tag: Lepton-ID, Kaon-IDBackground suppression: Mass resolution, K/p IDDecay time: Decay distance measurementMomentum measurement Ds

B

s

K



K







,K





d

p

47

m

m

144

m

m

440

m

m

Invariant

MassSlide47

… to see time dependent CP violation signal! 31-3-2008475 years data:Bs→ Ds-p+Bs→ Ds-K+The amplitude of these “wiggles“ are proportional to the imaginary part of the CKM phase gamma!Decay time (ps) →Slide48

Conclusion: after 5 years of LHCb…31-3-200848To make this plot only Standard Model physics is assumed.CKM Unitarity Triangle in 2007:Expected errors after 5 years (10 fb-1) of LHCb:Slide49

Conclusion and Outlook LHCb31-3-200849CP ViolationMeasure the Bs mixing phase (Bs→J/y f )Measure the CKM angle gamma via tree method (Bs → DsK)Measure the CKM angle gamma via penguin loops (B(s) → h+h - )Rare DecaysMeasure Branching Ratio B

s → m+

m -

Measure

angular distribution

B

0 → K*

m+

m

- Measure radiative penguins decays: b → s g (

B

→

X

s

g

)

Other

Flavour

Physics

Angle

beta

,

B-oscillations

,

lifetimes

,

D-physics

,

Higgs

,…?

The

collaboration

has

organised

analysis

groups

and

identified

“hot topics”:

Atlas and CMS look

for

new

physics

via direct

production

of

particles

LHCb

tries

to

study

it

via the (

possibly

complex)

couplings

in B

decay

loop

diagramsSlide50

Summary of Signal Efficiencies31-3-200850Slide51

Thank you for the attention. 31-3-200851Slide52

31-3-200852Slide53

31-3-200853Slide54

31-3-200854Slide55

Research QuestionsIs flavour physics fully described by the CKM mechanismIs CP violation in CKM sufficient to describe baryogenesis Many models beyond the SM include a rich flavour physics structureAre the penguin, box and tree diagrams governed by the same physics?Search for CP violation where SM predicts noneMeasure Branching Ratio for processes which are forbidden in SMFor the hypothesis that neutrinos are not massless the lepton system has a similar flavour strcture VCKM → VPMNS31-3-200855Slide56

Bd meson vs Bs meson31-3-200856These B bbar oscillations allow for a beautiful CP experimentSlide57

57Result of track findingTypical event display: Red = measurements (hits)Blue = all reconstructed tracksEfficiency vs p :Ghost rate vs pT :Eff = 94% (p > 10 GeV)Ghost rate = 3%(for pT > 0.5 GeV)VELOTTT1T2T3On average:26 long tracks11 upstream tracks4 downstream tracks5 T tracks26 VELO tracks

2050 hits assigned to a long track: 98.7% correctly assignedGhosts:

Negligible effect on

b decay reconstructionSlide58

58Experimental Resolutiondp/p = 0.35% – 0.55%p spectrum B trackssIP= 14m + 35 m/pT1/pT spectrum B tracksMomentum resolutionImpact parameter resolutionSlide59

59Particle IDRICH 1RICH 2e (K->K) = 88%e (p->K) = 3%Example:Bs->DshK



B

s

K







,K



D

s

Prim vtxSlide60

Event in the Simulation31-3-200860Slide61

Zoom in on the Velo detector31-3-200861Slide62

Roger FortyPhysics challenges of the LHC (III)624. Expected resultsExample of an early physics measurement that is expected from LHCb:Measurement of Bs–Bs oscillationsUse channel Bs  Ds-p+Plot made for one year of data  80,000 selected eventsfor Dms = 20 ps-1 (SM preferred)Proper time distribution for eventsproduced as Bs (rather than Bs) Need to take care of flavourtagging, proper-time resolution,background rejection andacceptance correctionCan measure frequency accurately cf recent result Dms = 17.8 ± 0.1 ps

-1 [CDF] Next step: measure the phase of the oscillation, using Bs  J/y f decays (B

s counterpart of B

0  J/

y KS

), cleanly predicted in the SM: fs

= -0.04 Slide63

Roger FortyPhysics challenges of the LHC (III)63Penguin decaysThese are another category of decays involving loop diagrams New particles might appear in those loopsSome indication from the B factory experiments that their results for penguindecays do not agree with expectations might be a hint of new physics?LHCb should reach a precision of ± 0.04on the asymmetry of Bs  ffExperimentTheorySlide64

Roger FortyPhysics challenges of the LHC (III)64Rare decaysProfit from the enormous statisticsto search for very rare decays such as Bs  m+m-Branching ratio ~ 3  10-9 in the Standard ModelBR can be strongly enhanced in SUSY[G. Kane et al, hep-ph/0310042]LHCb can reach the SM predictionin a few yearsIntegrated Luminosity (fb-1)BR (x10-9)53SM prediction

SUSY modelsLHCbSlide65

bq1d, sq2W−

Topologies in B decays

g

d (s)

q

q

W

−

b

u,c,t

b

q

u,c,t

u, c, t

q

b

W

+

W

−

V*

ib

V

iq

V

iq

V*

ib

Trees

Penguins

Boxes

m

b

γ

L

+m

q

γ

R

b

q

W

–

u, c, t

Z,

γ

d (s)

l

+

l

−

W

−

b

u, c, tSlide66

Search for NP comparing observables measured in tree and loop topologies (tree+box) in B J/ Ks (tree) in many channels(tree+box) in Bs J/  (peng+tree) in B,, (peng+box) in B Ks (peng+box) in Bs  New heavy particles, which may contribute to d- and s- penguins,could lead to some phase shifts in all three angles:(NP) = (peng+tree) - (tree) (NP) = (BKs) - (BJ/Ks) ≠ 0 (NP) = (Bs) - (BsJ/) Slide67

b  s exclusive b   (L) + (ms/mb)  (R)Measurement of the photon helicity is very sensitive test of SMMethods:- mixing induced CP asymmetries in Bs   , BKs 0- b   : asymmetries in the final states angular distributions are sensitive to the photon and b polarizations. - Photon helicity can be measured directly using parity-odd triple correlation (P(),[ P(h1)  P(h2)]) between photon and 2 out of 3 final state hadrons. Good examples are B K and B K decays Slide68

B → K* μμ ?A very important property isforward-backward asymmetry....and position of its zero, which is robust in SM: AFB(s), fast MC, 2 fb–1 s = (m)2 [GeV2]