Flavour physics, why do we care of? An experimental review.

IFIC Valencia, 16 January 2019

Flavour physics, why do we care of?

An experimental review.

[James O'Brien for Quanta Magazine]

[Acknowledgements to M. Bona, T. Gershon A. Mathad, M. Moulson, M. Vesterinen, V. Vagnoni, and G. Wormser for some material]

Flavour physics

Credits: Asimmetrie

6 March 1869, 150 years ago

“The” table today

[https://en.wikipedia.org/wiki/Periodic_table]

Antimatter

[Physical Review 43 (6) 491–494]

By Cush - Own work - previous version, CC0, https:// commons.wikimedia.org/w/index.php?curid=57404346

Parity

[https://commons.wikimedia.org/w/index.php?curid=49071459]

[Phys. Rev. 105, 1413]

Parity and Charge Conjugation: CP?

A lesson from the past: K L → ππ

[At Dubna, Okonov’s group studied 600 K

decays into charged particles.

At that stage the experiment was terminated by the administration of the lab.]

1964, annus mirabilis

Nobel laureate 1969

Nobel laureates 1978

Nobel laureates 1980

"for the discovery of violations of fundamental symmetry principles in

"for his contributions and discoveries

concerning the classification of

elementary particles and

their interactions."

"for their discovery of cosmic microwave background radiation."

[+Higgs mechanism +Bell theorem + colour hypothesis + …]

Cosmological Standard Model

Credits:https://commons.wikimedia.org/w/index.php?curid=11885244

25 30 35 40 ] c [GeV/

p 20

40 60 80 100 120 140 160 180 200 220

/GeV]cb µ [p/dσd

LHCb X

→ p pHe

= 110 GeV sNN

c < 0.7 GeV/

pT

0.4 <

20 30 40 50

] c [GeV/

p 20

40 60 80 100 120 140

/GeV]cb µ [p/dσd

LHCb X

→ p pHe

= 110 GeV sNN

c < 1.2 GeV/

pT

0.7 <

10 15 20 25 30 35

/GeV]cb µ [p/dσd

DATA EPOS LHC EPOS 1.99 QGSJETII-04 QGSJETII-04m HIJING 1.38 PYTHIA 6.4

LHCb X

→ p pHe

= 110 GeV sNN

c < 2.8 GeV/

pT

1.2 <

A matter’s universe?

[Phys. Rev. Lett. 121, 222001]

[PRL102,051101 (2009) PRL117,091103 (2016)]

Sakharov conditions

[proposed in 1967]

Inferred from:

- abundances of light elements in the intergalactic medium formed in the process of Big Bang nucleosynthesis - power spectrum of temperature

fluctuations in the Cosmic Microwave Background

Quantitatively, from the Universe:

Assuming a baryo-symmetric universe

Sakharov conditions

[proposed in 1967]

We can estimate the magnitude of the baryon asymmetry of the Universe caused by CP violation

- Vanish for degenerate quark masses - M O(100 GeV): electroweek scale

- J O(10

): parameterization invariant measure of CPv in the quark sector [PRL 55 (1985) 1039];

Quantitatively, from the SM:

10

Open points: SM (and beyond)

- No explanation for the quark hierarchy - Why are there 3 families/generations?

- No real explanation for CP violation

- Why it is only found in the weak interaction?

- Mass value of the Higgs boson - EW and strong unification

- …

- No explanation for baryogenesis - Dark matter and dark energy - Neutrino masses

- Gravity - …

Possible “answers” from flavour sector

Up to the third generation

Different mass and flavour (weak) eigenstates (1963)

GIM mechanism (1970)

"CP Violation in the Renormalizable

c: 1974 t: 1994

b: 1977

CKM matrix

The CKM matrix arises from the relative misalignment of the Yukawa matrices (couplings of the quarks to the Higgs field ) for the up- and down-type quarks

CKM is a 3x3 complex unitary matrix, described by 9 real parameters:

- 5 can be absorbed as phase differences between the quark fields - 3 can be expressed as (Euler) mixing angles

- the fourth makes the CKM matrix complex (i.e. give it is a phase) - Weak interaction couplings differ for quarks and antiquarks

- Allow for CP violation

- Defined pattern ~diagonal with no known underlying reason

- Properties from Unitarity

CKM matrix

The CKM matrix arises from the relative misalignment of the Yukawa matrices (couplings of the quarks to the Higgs field ) for the up- and down-type quarks

Choice of the 4 parameters: many parameterizations exist (up to 30!) somehow confusing

[Chau, Phys. Rev. Lett. 53, 1802 (1984), PDG, Phys. Rev. D 98, 030001 (2018)]

CKM (Wolfenstein parameterization)

The first row

≈ 2×10⁻⁵

[Based on CKM2018 update from M. Moulson]

Most precise test of CKM

unitarity

Triangles from unitarity

[hep-ph/9607305v1]

- Three complex numbers add to zero ⇒ triangle in Argand plane - All TU have same area, proportional to CP violation

[Jarlskog parameter]

Provides numerous tests of constraints between independent observables

The UT triangle [bd]

Constraints in the unitarity plane

[EPJC 41 (2005) 1]

- In SM the CKM phase is the sole origin of CP violation - All measurements must

agree on the position of the apex of the Unitarity Triangle

[Illustration assumes no experimental or theoretical uncertainties.]

Trees and loops

e.g. B

→K

π

In the presence of relevant new physics effects, the various contours would not cross each other in a single point

Tree-level decays: expected

to be largely unaffected by

non-SM contributions

Trees and loops

e.g. B

→K

π

In the presence of relevant new physics effects, the various contours would not cross each other in a single point

FCNC: Loops in the

relevant diagrams: sensitive

to non-SM physics.

References: fits, averages, reviews…

http://ckmfitter.in2p3.fr/

https://hflav.web.cern.ch/

Recent reviews/summaries:

ICHEP2018 “Summary of quark flavour” (Phillip Urquijo) BELLE2-TALK-CONF-2018-092

CKM 2018 https://indico.cern.ch/event/684284/

timetable/#20180917.detailed

http://www.utfit.org/UTfit/

Rare kaon decays

Rare kaon decays: K πνν

K→πνν is a uniquely sensitive

indirect probe for high mass scales:

need precision measurements of both K

and K

decays

NA62 will improve on current

knowledge of BR(K

→π

νν) in the short term, ultimately reaching ~100 event sensitivity

KOTO will reach SM sensitivity to BR(K

→π

νν) by 2021

KLEVER: preliminary study for

BR(K

→π

νν) at SPS@CERN (60

SM events, S/B~1)

When B-factories started… (1998)

[From BaBar physics book (SLAC-R-504)]

CP violation:

- experimentally established only for kaons

- favoured theoretical framework provided by the existence of at least 6 quarks (KM) - all measurements consistent with flavour being the only CP violation source

(although with room for other sources)

[Btw, same year of neutrino oscillations from Kamiokande]

…sin 2 β (not only kaon eventually)

From Ba Bar 25

annive rsary

indico.c ern.ch/ event/765572/

…sin 2 β (not only kaon eventually)

[CP from Interference of Mixing and Decay]

For B

→J/ ψ K

; S=sin2 β , C=0

(q/p)

Asymmetric B factory principle

Asymmetric B factories

Belle and BaBar

“High vertex resolution, good tracking, excellent calorimetry and sophisticated particle ID ability,

good geometrical 4 coverage”

[Nucl.Instrum.Meth.A479:1-116,2002 arXiv:hep-ex/0105044]

[Nucl.Instrum.Meth.A479:117-232,2002]

B factories data

~430/fb on Y(4S) ~710/fb on Y(4S)

Total over 10

BB pairs recorded

sin 2 β : a lesson from extrapolations

sin 2 β : the golden mode

sin 2 β : some tensions along the years

In 2005: 3.8 σ tension between sin 2 β (b→c) and sin 2 β (b→s)

Since 2008 tension is below 1 σ

LHC

[θ ~ 0]

[θ = π /2]

LHCb at LHC

Extremely large σ (bb) and σ( cc) in LHC hadron collisions.

Run 1 (7-8 TeV), in LHCb acceptance:

~0.7×10

bb/fb ~6.0×10

cc/fb

Run 2 (13TeV): ~×2 with respect to Run 1

To be compared with ~10

BB pairs B-factories data sample.

LHC: inclusive production of b-

hadrons, not just B

/B

but also

B

, Λ

, Ξ

, Ω

, B

and their

LHCb detector

[LHCb, A. Alves et al., The LHCb Detector at the LHC, JINST 3 (2008) S08005]

LHCb detector performance

[LHCb Detector Performance Int.J.Mod..Phys. A30 (2015) 1530022]

Oscillation frequency Δ m s and Δ m d

[Eur. Phys. J. C (2016) 76: 412]

[New Jour. Phys. 15 (2013) 053021]

The excellent decay time resolution and particle identification capabilities of the LHCb detector allow the

oscillation frequency to be measured with unprecedented precision.

Theory: ~2s higher, by far less precise than exp.

Δ m

= (615 ± 53) ns

[arXiv:1603.07770]

Δ m

= (20.01 ± 1.25) ps

[arXiv:1712.06572]

Measurement of γ

Τ he least known angle of the UT so far, measured via the interference between b→u and b→c tree-level transitions

Simple and clean theoretical interpretation, but statistically very challenging

[LHCb-CONF-2018-002]

In agreement with world averages

Most precise determination from a

single experiment

Measurement of γ

[LHCb-CONF-2018-002]

In agreement with world averages Most precise determination from a single experiment

[Accuracy of all 16 LHCb inputs is statistically limited]

Τ he least known angle of the UT so far, measured via the interference between b→u and b→c tree-level transitions

Simple and clean theoretical interpretation,

but statistically very challenging

Trigger at LHCb

40 MHz bunch crossing rate

450 kHz

h^± 400 kHz

µ/µµ 150 kHz e/γ

L0 Hardware Trigger : 1 MHz readout, high E

/P

signatures

Software High Level Trigger 26000 Logical CPU cores

Offline reconstruction tuned to trigger time constraints

Mixture of exclusive and inclusive selection algorithms

1.5 kHz Inclusive Topological

3.5 kHz (0.2 GB/s) to storage

1 kHz Inclusive/

Exclusive

1 kHz Muon and

DiMuon

LHCb 2011 Trigger Diagram

Try to defer computing needs to time without beam

[arXiv:1211.3055; CERN-LHCb-DP-2012-004]

[arXiv:1310.8544v1]

40 MHz bunch crossing rate

450 kHz

h^± 400 kHz

µ/µµ 150 kHz e/γ

L0 Hardware Trigger : 1 MHz readout, high E

/P

signatures

Software High Level Trigger 29000 Logical CPU cores

Offline reconstruction tuned to trigger time constraints

Mixture of exclusive and inclusive selection algorithms

5 kHz (0.3 GB/s) to storage Defer 20% to disk LHCb 2012 Trigger Diagram

Trigger at LHCb

[arXiv:1211.3055; CERN-LHCb-DP-2012-004]

[arXiv:1310.8544v1]

Trigger at LHCb

[ ]

“All I’m saying is now is the time to run data reconstruction only once.”

Before alignment σ(Υ) ~ 92 MeV

Trigger at LHCb

Same online and offline reconstruction and PID - prompt alignment and calibration

- completely automatic and almost in real-time

~50k logical cores

~5PiB disk space

40 MHz bunch crossing rate

450 kHz

h^± 400 kHz

µ/µµ 150 kHz

e/γ

L0 Hardware Trigger : 1 MHz readout, high ET/PT signatures

Software High Level Trigger

12.5 kHz (0.6 GB/s) to storage

Partial event reconstruction, select displaced tracks/vertices and dimuons

Buffer events to disk, perform online detector calibration and alignment

Full offline-like event selection, mixture of inclusive and exclusive triggers

LHCb 2015 Trigger Diagram

After alignment

σ(Υ) ~ 49 MeV

Trigger at LHCb-Upgrade

Work in progress

for 2021 [LHCB-TDR-016]

2009, before LHCb contributions

Latest combination (Summer 2018)

Mainly from LHCb results but also new results from BaBar, Belle, and lattice QCD.

Great success of the Standard Model CKM picture.

Still room for

new physics at

the 10% level

From Summer to Autumn

From Summer to Autumn

B (s) µµ : a long story

[hep-ex/1403.4427]

Clean theoretical prediction:

B (s) µµ at LHC (pre 2017)

B (s) µµ at LHCb (Run 2 data)

[LHCb-PAPER-2017-001]

In 2017, new

measurement from LHCb using part of Run 2: first

observation from a single experiment

It starts to be possible to measure other

properties e.g. the

effective lifetime

B (s) µµ : the story continues

[LHCb-PAPER-2017-001]

B (s) µµ : a lesson from the past

B (s) µµ : a lesson from the past

Lepton universality test with RD(*)

Evidence for a D(*) τν excess with respect to SM

[PRL 109, 101802 (2012)]

Lepton universality test with RD(*)

Evidence for a D(*) τν excess with respect to SM

Semileptonic b→s µµ

(Theoretically far more challenging due to the hadronic form factors.)

Data sit often below theory…

Lepton universality test with b→sll

Lepton universality test with b→sll

What’s next? LHCb Upgrade

LHCb just ended a successful data taking!

~10/fb on disk

A few exceptions, but most results based on 3/fb from Run 1. Full dataset is now

equivalent to 5× more b-hadrons than Run 1 Many results only statistically limited The amount of data and the physics yield from data recorded by the current LHCb experiment is limited by its detector.

Phase-I upgrade aim at collecting 10×

more data with 20× more hadronic events:

- fully software 40 MHz trigger

- redesign most of sub-detectors

for 5×-10× peak luminosity

LHCb Upgrade and Belle II

Belle II

Belle II has completed the initial data taking in 2018 (Understanding the machine and backgrounds, Detector and software checkout) The physics run is starting

~now (beginning of 2019)

[KEK Report 2010-1, BELLE2-PAPER-2018-001]

Belle II

Flavour physics maintains a huge discovery potential.

[The Belle II Physics Book, arXiv:1808.10567]

[KEK Report 2010-1, BELLE2-PAPER-2018-001]

Belle II

[The Belle II Physics Book, arXiv:1808.10567]

50/ab, SM-like scenario UT today is extrapolated to:

50/ab, world average values

[KEK Report 2010-1, BELLE2-PAPER-2018-001]

LHCb Upgrade II

Belle II and LHCb upgrade will improve the flavour precision by an order of magnitude.

However, many NP sensitive observables are far from any systematic floor, and others will remain out of reach.

[CERN-LHCC-2017-003] [arXiv:1808.08865]

Future

From “physics case for LHCb Upgrade 2”

LHCB-PUB-2018-009, arXiv:1808.08865

Future

From “physics case for LHCb Upgrade 2”

LHCB-PUB-2018-009, arXiv:1808.08865

ATLAS B-physics studies at increased LHC luminosity ATL-PHYS-PUB-2013-010

Prospects for selected standard model measurement with the CMS experiment at the High-Luminosity LHC CMS-PAS-FTR-14-015

The Belle II Physics Book, arXiv:1808.10567

Synergy of LHCb and BESIII physics programs

LHCb-PUB-2016-025

LHCb Upgrade(s)

CP-violating observables

[LHCB-PUB-2018-009, arXiv:1808.08865]

LHCb Upgrade(s)

Rare decays and lepton- universality tests

If no direct evidence of new physics pops out of the LHC, flavour physics can play a key role in indicating the way for future developments of elementary particle physics

If new particles will be detected in direct searches, flavour physics will be a fundamental ingredient in

understanding the structure of what lies beyond the SM

[LHCB-PUB-2018-009, arXiv:1808.08865]

LHCb 23/fb [Upgrade]

LHCb

23/fb

LHCb 300/fb [Upgrade II]

LHCb 300/fb

[LHCb-PUB-2018-009 ; CERN-LHCb-PUB-2018-009]

Flavour perspectives

Credits:Vlad Gerasimov· 6 July 2012

SM picture stays solid and it is necessary to have a program as diversified as possible

We still don't know:

- why there are so many fermions in the SM

- what causes the baryon asymmetry of the Universe - where exactly the new physics is and what its

flavour structure is

Flavour physics prospects are good for progress in the next few years, complementary to the high-p

program of the LHC

Anomalies are exciting, but inconclusive with current data. They sit aside powerful null results in B→µµ and B mixing.

LHCb Run-II data (+Belle II) could be sufficient to claim a discovery. The LHCb upgrades are required to fully exploit the HL-LHC capabilities in the

Dream scenario, for illustration only

Thank y ou!

https://xkcd.com/1621/