DESY SUMMER SCHOOL 2016 Lectures on Experimental Flavour

Lectures on Experimental Flavour Lectures on Experimental Flavour PhysicsPhysics

DESY SUMMER SCHOOL 2016

1

Gianluca Inguglia- DESY24/08/2016

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Lectures on Experimental Flavour Lectures on Experimental Flavour PhysicsPhysics

DESY SUMMER SCHOOL 2016

1

Gianluca Inguglia- DESY24/08/2016

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What is flavour physics?

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What is flavour physics?

Study of the properties of the families of fermions● Mass hierarchies● Mixing and couplings● Number of families● Allowed and forbidden transitions● Discrete symmetries and their violation● Quark flavour, charged leptons, neutrinos ● ...

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The Universe as seen by Planck (the The Universe as seen by Planck (the ESA mission..)ESA mission..)

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68.3%

26.8%

68.3%

Composition of the Universe after Composition of the Universe after Planck (the ESA mission..)Planck (the ESA mission..)

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According to the theory of big bang, at the time of big bang matter and antimatter were produced in equal amounts...

...where is the antimatter then?

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Sakharov conditionsSakharov conditions

● Baryon number violation● C & CP violation● Departure from thermal equilibrium

A Universe balanced in terms of the amount of matter and antimatter can evolve into a matter dominated Universe if three conditions are satisfied*:

*A. D. Sakharov, "Violation of CP invariance, C asymmetry, and baryon asymmetry of the universe". Journal of Experimental and Theoretical Physics 5: 24–27, (1967)

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Particle events

The experimental processThe experimental process

(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

10

Particle events

Particle detector


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

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Particle events

Particle detector


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

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Particle events

Particle detector

Electric signal


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

13

Particle events

Particle detector

Electric signal

Detector electronics


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

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Particle events

Particle detector

Electric signal


Event data

0111001010001010101101010101011100101000101010110101011


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

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Particle events

Particle detector

Electric signal


Event data

0111001010001010101101010101011100101000101010110101011

Data processing


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

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Particle events

Particle detector

Electric signal


Event data

0111001010001010101101010101011100101000101010110101011

Data processing

Data storage


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

17

Particle events

Particle detector

Electric signal


Event data

0111001010001010101101010101011100101000101010110101011

Data processing

Data storage

Data processing


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

18

Particle events

Particle detector

Electric signal


Event data

0111001010001010101101010101011100101000101010110101011

Data processing

Data storage

Data processing

Obtain the result


(B0→ J /ψK s

0)

J /ψ→μ+μ-

K s0→π+π-

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20

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LHCb detectorLHCb detector

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electrons (7GeV)

positrons (4GeV)

KL and muon detector:Resistive Plate Counter (barrel outer layers)Scintillator + WLSF + MPPC (end-caps , inner 2 barrel layers)

Particle Identification Time-of-Propagation counter (barrel)Prox. focusing Aerogel RICH (fwd)

Central Drift ChamberHe(50%):C2H6(50%), small cells, long lever arm, fast electronics

EM Calorimeter:CsI(Tl), waveform sampling (barrel)Pure CsI** + waveform sampling (end-caps)

Vertex Detector2 layers DEPFET + 4 layers DSSD

Beryllium beam pipe2cm diameter

Belle II detector

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e- 2.6 A

e+ 3.6 A

To obtain x40 higher luminosity

Colliding bunches

Damping ring

Low emittance gun

Positron source

New beam pipe& bellows

Belle II

New IR

TiN-coated beam pipe with antechambers

Redesign the lattices of HER & LER to squeeze the emittance

Add / modify RF systems for higher beam current

New positron target / capture section

New superconducting /permanent final focusing quads near the IP

Low emittance electrons to inject

Low emittance positrons to inject

Replace short dipoles with longer ones (LER)

KEKB to SuperKEKB

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The standard modelThe standard model

Dark matter

New forces

?

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A 3x3 matrix is defined by 18 parameters, howeverV

CKM is a unitary matrix VV†=V†V=I : 9 unitarity conditions..

Only 9 parameters are “free”, and these are 3 angles and 6 phases, however

5 phases are non-physical (unobservable)V

CKM can be parametrised by 4 parameters: 3 Euler angles and 1

complex phase. The complex phase in VCKM

violates CP.

q

q'

WV

qq'

With probability proportional to |V

qq'|2

Transitions between quarks: the Transitions between quarks: the CKM matrixCKM matrix

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CKM matrix: standard parametrization CKM matrix: standard parametrization 3 Euler rotations

1 complex (CP violating) phase

c ij=cosθij sij=sinθij

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CKM matrix: Wolfenstein CKM matrix: Wolfenstein parametrization parametrization

4 parameters: A, λ, ρ, η

COMPLEX REAL

OK for B mesons and K, not for D26

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The CKM matrix up to The CKM matrix up to λλ55+O(+O(λλ66))

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Unitarity relationsUnitarity relations∑i

V ijV ik*=δ jk

∑j

V ijV kj*=δ ik

Column orthogonality

row orthogonality

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Unitarity relationsUnitarity relations∑i

V ijV ik*=δ jk

∑j

V ijV kj*=δ ik

Column orthogonality

row orthogonality

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λ3

λ5

Unitarity trianglesUnitarity triangles

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λ3

λ5

Unitarity trianglesUnitarity triangles

ℑ[V ijV klV il*V kj

*]=J∑

mn

ϵikm ϵ jlnℑ[V ijV klV il*V kj

*]=J∑

mn

ϵikm ϵ jln

J=c12c23 c132 s12 s23 s13sinδKM≈λ

6 A2η

Jarlskog invariant JThe area of the unitarity triangles is a constant and it is proportional to CP violation. If any of the mixing angles is zero, there is no CP violation even if δ

KM is large!!

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C: charge conjugation C: charge conjugation

CΨ(r , t)→Ψ*(r , t)

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P: parityP: parity

PΨ(r ,t )→Ψ(−r , t)

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T: time reversalT: time reversal

T Ψ(r , t)→Ψ(r ,−t)

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CP symmetryCP symmetry

CPΨ(r , t)→Ψ*(−r , t)

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CPT: a symmetry of Nature CPT: a symmetry of Nature

CPTΨ(r ,t )→Ψ*(−r ,−t)

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CPT: a symmetry of Nature CPT: a symmetry of Nature

CPTΨ(r ,t )→Ψ*(−r ,−t)CPT is now considered a symmetry of Nature (until proven to be broken), so if CP is violated then also T has to be violated to preserve CPT.

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How does CP violation manifest?How does CP violation manifest?

● Direct CP violation● Indirect CP violation● Interference CP violation

λ f=AAqp

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Direct CP violationDirect CP violation AA≠1

ACP ( f CP)=N (B0

→ f CP)−N (B0→ f CP )

N (B0→ f CP)+N (B0→ f CP)

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Direct CP violationDirect CP violation AA≠1

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Direct CP violationDirect CP violation

This might be a difficult measurement due to systematic effects!! (some) experimenters tend to combine different measurement so that the systematic cancels:

AA≠1

( )

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Direct CP violationDirect CP violation

This might be a difficult measurement due to systematic effects!! (some) experimenters tend to combine different measurement so that the systematic cancels:

AA≠1

( )

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Neutral mesons mixing Neutral mesons mixing

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CP violation in Mixing (indirect)CP violation in Mixing (indirect)

D0 D0 D0 D0

if P(D0→D0

)≠P (D0→D 0

)→CP

Example of t-channel (s-channel possible) box diagram for D0 meson mixing

qp≠1

P=probability

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CP violation in Mixing (indirect)CP violation in Mixing (indirect)

D0 D0 D0 D0

if P(B0→B0

)≠P(B0→B0

)→CP

Example of t-channel (s-channel possible) box diagram for B0 meson mixing

qp≠1

P=probability

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Interference CP violation Interference CP violation (time-dependent)(time-dependent)

ℑλ f≠0

B0 J / ψK s

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ℑλ f≠0

D0

ϕMIX

A

A

B0 J / ψK s

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ℑλ f≠0

B0

π+π

-

ϕMIX

A

B0

50


ℑλ f≠0

ϕMIX

A

B0

B0

J / ψK s

51


ℑλ f≠0

ϕMIX

A

A

B0

B0

J / ψK s

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ℑλ f≠0

ddt⟨Ψ (t)∣Ψ(t )⟩=−⟨Ψ(t )∣Γ∣Ψ( t)⟩

The study of CP violation in the interference between mixing and decay requires knowledge of the time evolution.

J / ψK s

ϕMIX

A

A

2βB0

B0

Phase mismatch between the two paths

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ℑλ f≠0

ddt⟨Ψ (t)∣Ψ(t )⟩=−⟨Ψ(t )∣Γ∣Ψ( t)⟩


π+π

-

ϕMIX

A

A

D0

D0

Phase mismatch between the two paths

2βc

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ℑλ f≠0

ddt⟨Ψ (t)∣Ψ(t )⟩=−⟨Ψ(t )∣Γ∣Ψ( t)⟩


J / ψK s

ϕMIX

A

A

2βB0

B0

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TDCPV as a double-slit experimentTDCPV as a double-slit experiment

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In order to measure the time at which the decay occurs one has to measure the distance: t=L/v. This requires vertexing with good vertex resolution.

In symmetric energy collisions taking place at the Y(4S) peakplab =0.3 GeV, mB=5.28 GeVAverage flight distance: <L>= ()cB= (p/m)(468m)=(0.3/5.28)(468m)=(27m)

Too small to be measured!!In asymmetric energy collisions the entire system is Lorentz Boosted:= plab /Ecm=(phigh-plow)/Ecm

SLAC: 9 GeV+3.1 GeV, = 0.55 <L>= 257mKEK: 8 GeV+3.5 GeV, = 0.42 <L>= 197mthese distances/lengths can be measured!!Due to the boost and the small plab the time measurement is a measurement of the of The decay vertex in the z-direction.

e-e

0B

0B

m 30

e-e

0B

0Bm 200

symmetricCESR

asymmetricSLAC, KEK

z-axis

B=1.6x10-12 sec

Symmetric vs. asymmetric energy collisionsSymmetric vs. asymmetric energy collisions

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Ingredient for TDCPV studiesIngredient for TDCPV studies

LHCb is perfectly suited for TDCPV measurements since it studies highly boosted b-events in the forward direction. This is a very alternative and original approach.Belle II will start data taking next year and then from 2018. Nice competition ahead!

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TDCPV in B0 → J/TDCPV in B0 → J/Ψ KΨ Kss00

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Combined fit to the unitarity triangle:Combined fit to the unitarity triangle:CKM fitterCKM fitter

All the results from different flavour measurements can be combined into a fit of the unitarity triangle.

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Sakharov conditionsSakharov conditions

● Baryon number violation● C & CP violation● Departure from thermal equilibrium

A Universe balanced in terms of the amount of matter and antimatter can evolve into a matter dominated Universe if three conditions are satisfied*:

ηobs=nB−nB

nγ≈6×10−10 , ηCP∼10−18

ηCPηobs=

10−18

10−10=10−8 Need additional sources of CP violation to explain matter-antimatter asymmetry!

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New physics in BNew physics in Bs,ds,d→μμ?→μμ?

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New physics in BNew physics in B→μμ?→μμ?

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Belle results PRD 92, 051102 (2015)PRD 82, 071101 (2010)Br(B+→τ+υ)= Hadronic TAG [0.72±0.27±0.11]x10-4

SL TAG [1.54±0.38±0.37]x10-4

Belle 2 sensitivity (50 ab-1)Br(B→τυ) ~ 4*10-5

Belle, hadronic TAG Belle, SL TAG

B→τυB→τυ

3

New physics in BNew physics in B→lμ?→lμ?

64

Belle, hadronic TAG Belle, SL TAG

B→τυB→τυ

4

Expected precision with the Belle full data sample, and 5 ab−1 and 50 ab−1 of Belle II data.

(x10-6)

New physics in BNew physics in B→lμ?→lμ?

65

New Physics could affect this decay topology in two ways:Branching FractionTau polarization

BaBar searches in this topology excluded Type II- 2HDM at 3.4 standard deviations

Experimentally challenging2 missing neutrinos in hadronic tau decays topologies3 missing neutrinos in leptonic tau decay topologies

New physics in BNew physics in B→D*τυ?→D*τυ?

66

R(D(∗))=

Γ(B0→D(∗)

τ ν)

Γ(B0→D(∗) l ν)l=μ ,e

Very precise SM prediction:R(D) =0.297 ± 0.017 Phys.Rev.D78(2008) 014003

R(D*) = 0.252 ± 0.003 Phys.Rev.D85(2012)

Leptoquark could be a possible explanation for the tension

HFAG 2016:R(D)=0.397±0.040±0.028R(D*)=0.316±0.016±0.010

HFAG 2016:R(D*)=0.316±0.016±0.010


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(x10-3)


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B K→ (*) : νν → b→s flavourchanging neutral current → suppressed within the SM → golden mode of Belle II because theoretically very clean:

free of uncertain longdistant hadronic effects

Why at Belle II? > Can be measured only in e+e, experimentally challenging> Existing limits from BABAR and Belle leave room for NP

Sensitivity with full Belle II data> SM expectation for exclusive

> B → K(*) can be probed at νν5 levelσ

JHEP 1502, 184 (2015)

BABAR :BR(B+→K +ν ν)<1.7×10−5

BELLE :BR(B0→K* 0

ν ν)<5.5×10−5

Babar, B → K(*) ν ν , PRD 87, 112005 (2013)Belle, B → K(*)/π/ρ ν ν, PRD 87, 111103(R) (2013)

New physics in BNew physics in B→K→K(*)(*)υυ?υυ?

69

B → K(*) νν : → b→s flavour-changing neutral current→ suppressed within the SM → golden mode of Belle II because theoretically very clean: free of uncertain long-distant hadronic effects

Why at Belle II? > Can be measured only in e+e, experimentally challenging> Existing limits from BABAR and Belle leave room for NP

Sensitivity with full Belle II data> SM expectation for exclusive B → K(*) can be probed at 5 levelνν σ

JHEP 1502, 184 (2015)

BR (B+→K +

ν ν)SM=(3.98±0.43±0.19)×10−6

BABAR :BR(B+→K+ ν ν)<1.7×10−5

BR(B0→K * 0ν ν)SM=(9.19±0.86±0.50)×10−6

BELLE :BR (B0→K* 0

ν ν)<5.5×10−5

Fake signal: B → f '2 K*

With f'2 → K0L K

0L (22%)

B → ηc K+

With ηc → K0L K0

L

B decays to D0:D0 → K0

L π0

Searched signal: K+

Ks K*+ → Ks π

+

K*+ → K+ π0

K*0 → K+ π

Separation between signal and fake signal requires very good signal-selection/background-rejection algorithms → K0

L VETO

*Ongoing work with promising preliminary results*Algorithm to be implemented into Belle II Full Event Interpretation (FEI) module

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New physics in BNew physics in B→K→K(*)(*)υυ?υυ?

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q2[GeV 2

/c 4]

* Preliminary MC results shown* Box opened* Analysis now in Belle wide review process* Shown today: MC sensitivity studies

>Full angular analysis of final state particles

20q2[GeV 2

/c 4] 21

* Analysis performed blind* New: Box opened* Analysis now in Belle wide review process* Shown today: MC sensitivity studies

New physics in BNew physics in B→K→Kllll??

71

e+e-→Y (3 S)↓

Y (3 S)→π+π

-Y (1S)↓

Y (1S)→ invisible

e+e-→Y (2S )↓

Y (2 S)→π+π

-Y (1 S)↓

Y (1 S)→invisible

➔ Low mass dark matter particles however might might play a role in the decays of Y(1S), having Y(1S)→χχ if kinematic allowed. [Phys. Rev. D 80, 115019, 2009]

➔ Also, new mediators (Z', A0, h0) or SUSY particles might enhance Y(1S)→νν(γ). [Phys. Rev. D 81, 054025, 2010]

➔ In absence of new physics enhancement, Belle2 should be able to observe the SM Y(1S)→νν

M Y (3S )=10.355GeV /c2 , M Y (2S )=10.023GeV / c2 , M Y (1S )=9.460GeV /c2

~ 900MeV available for Pπ π

~ 540MeV available for Pπ π

BR (Y (1S )→ν ν̄)

BR(Y (1S )→e+e-)=

27G2 M Y (1S)4

64 π2α2 (−1+43

sin2θW )

2

=4.14×10−4

BR (Y (1S )→ν ν̄)∼9.9×10−6

Belle2 SimulationY(3S)→π+π-Y(1S), Y(1S)→ νν

(4.4%)

(18.1%)

Y(nS): bound state of a b quark and a b antiquark

New physics in YNew physics in Y→invisible?→invisible?

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e+e-→Y (3 S)↓

Y (3 S)→π+π

-Y (1S)↓

Y (1S)→ invisible

e+e-→Y (2S )↓

Y (2 S)→π+π

-Y (1 S)↓

Y (1 S)→ invisible



➔ In absence of new physics enhancement, Belle2 should be able to observe the SM Y(1S)→νν

BR (Y (1S )→ν ν̄)

BR(Y (1S )→e+e-)=

27G2 M Y (1S)4

64 π2α

2 (−1+43

sin2θW )

2

=4.14×10−4

BR (Y (1S )→ν ν̄)∼9.9×10−6

(4.4%)

(18.1%)

A signal of Y(1S)→invisible is an excess of events over the background in the M

r distribution at a mass

equivalent to that of the Y(1S) (9.460 GeV/c2)

M r2=s+M

π+π

-−2√s Eπ+π

-

CMS


73

e+e-→Y (3 S)↓

Y (3 S)→π+π

-Y (1S)↓

Y (1S)→ invisible

e+e-→Y (2S )↓

Y (2 S)→π+π

-Y (1 S)↓

Y (1 S)→ invisible



➔ In absence of new physics enhancement, Belle2 should be able to strongly constrain the SM Y(1S)→νν

BR (Y (1S )→ν ν̄)

BR(Y (1S )→e+e-)=

27G2 M Y (1S)4

64 π2α

2 (−1+43

sin2θW )

2

=4.14×10−4

BR (Y (1S )→ν ν̄)∼9.9×10−6

Belle2 SimulationY(3S)→π+π-Y(1S), Y(1S)→ νν

(4.4%)

(18.1%)

No signal was observed over the expected background and upper limits have been obtained: BR(Y→νν) < 3x10-4 (BaBar) and BR(Y→νν) < 3.0x10-3(Belle).

If we collect >200fb-1 of data @ Y(3S) [Y(2S)] we should reconstruct between 30 and 300 [~200 and ~2000] events , assuming 10-5 (SM)<BR

Y→invisible< 10-4 (NP) and ε

tot=10%.


74

B→νν , ν ν γ

BABAR (471×106 B B pairs) : BR(B→ν ν̄)<2.4 10−5(ϵsig∼18×10−4

),

BR(B→ν ν̄ γ)<1.7 10−5(ϵsig∼16×10−4)

BELLE (657×106B B pairs) : BR(B→ν ν̄)<1.3 10−4 (ϵsig∼2.2×10−4)Phys. Rev. D 86, 032002 (2012)

Phys. Rev. D 86, 051105 (2012)

Ongoing sensitivity studies at Belle 2, maybe down to BR~10-6

New physics in BNew physics in B→invisible?→invisible?

75

B→νν , ν ν γ

Additional decay topologies arise from new physics modelsThese new topologies will affect the BR of B to invisible final states, if they exist, making B to invisible “observable” (BR as high as 10-6) [Phys. Rev. D 65, 015001 (2002)].Of course this is a high risk measurement..

New physics in BNew physics in B→invisible?→invisible?

76

What's going on with charmonium and XYZ?What's going on with charmonium and XYZ?

?

77

● Flavour physics is a very active field of research in Flavour physics is a very active field of research in HEP.HEP.

● Many dedicated facilities and mostly all the experiments Many dedicated facilities and mostly all the experiments are involved in flavour physics.are involved in flavour physics.

● Many questions still unanswered → Flavour can help. Many questions still unanswered → Flavour can help.

● If LHC does NOT find new particles → flavour physics If LHC does NOT find new particles → flavour physics results can tell you at which energy scale to look for results can tell you at which energy scale to look for them.them.

78

Thank you,Thank you,

Time for questions...Time for questions...

79

T violation IT violation I

Bernabeu et al. proposed a set of four processes to be studied. The study refers to entangled neutral meson pairs to be used when looking for T violation.arXiv:1203.0171

+ and – subscripts refer to the CP eigenvalue of the CP filter mode.

One need to: identify T-conjugated final states apply filters: flavour filter and CP filter

P0→P _ vs P _→P0 : B0

→l+ X , B _→J / Ψ K S0

T conjugate : B_→ J /Ψ KL0 , B0

→l - X

BaBar found T violation (14σ) studying the processes:arXiv:1207.5832

A. Bevan, G.I., M. Zoccali, arXiv:1302.4191J. Bernabeu et al. , arXiv: 1203.0171

80

T violation IIT violation II

Φ=1

√2(|P1

0P20>+ |P2

0P10>) (P=Bd , s ,D)

81

α∈(l+ ,l-)

β∈(K S0,K L

0)

(l+ X ,l- X )

(K S0 J /Ψ , KS

0 J /Ψ )

Flavour

CP

+ if decay to flavour final state α occurs before the decay to CP final stateβ±:

From “simple” quantum mechanics and due to entanglement one has the following time evolution:

T violation IIIT violation III

(Δ Γ=0)

S=2ℑ(λ f )

1+∣λ f∣2,C=

1−∣λ f∣2

1+∣λ f∣2,ΔCT

+=C

l - , KL

-−C

l+ , KS

+ , Δ ST+=S

l- , K L

-−S

l+ , KS

+

82

Only primary leptons: low background!

What to expect for B

D0(D0

)→Xl ν

Ψ(3770)→D0 D0

D0(D 0)→h+h- K S , L

0,

D0→K S , L

0(π

0,ω ,η , η' ,ρ0,

ϕ , f 0,a0)

D0→K S

0 KS0 K L

0(→K L

0 K L0 K S

0)

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DESY SUMMER SCHOOL 2016 Lectures on Experimental Flavour