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Flavour physics

Justine Serrano

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Journée SFP: Futur de la physique des particules 23 janvier 2015

I will present a (biased, incomplete) review about quarks and charged leptons

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Different aspects of flavour physics: number of families, mass hierarchies, mixing and coupling, symmetries principles and their violation (CPT)

In the past, flavour physics made a lot of « indirect » discoveries

890

1064.0

107

)(

)(

KBR

KBR+

u

W+

s

+

d s

-

K+

allowed K0

forbidden

not a Z0

1970: Glashow, Iliopoulos, Maiani (GIM) proposed a solution No flavor changing neutral current (FCNC) FCNC are suppressed by loop diagrams charm quark prediction

Observed in 1973

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• 1964: observation of CP violation in kaons. In 1973 Kobayashi and Maskawa skow that this can be explained if there are 3 generations

prediction of the third family, directly observed in 1977

• 1987: B meson mixing

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1

2

1

0.00002 psGeV

0.5ps

tB

mm

c

Argus measured First hint of high quark top mass, discovered in 1995

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In the past, flavour physics made a lot of « indirect » discoveries

2000-2010: the B factories

771M + 463M bb pairs accumulated Only Bd and Bu produced, but very clean events

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e+e-

Section

efficace (nb)

uu 1,39

dd 0,35

ss 0,35

cc 1,30

bb 1,10

B factories produced a lot of results (~1000 publications), and a Nobel prize!

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Unitarity triangle measurements

tbtstd

cbcscd

ubusud

CKM

VVV

VVV

VVV

V

λ =|Vus|~0.22

η responsible for CP

2( ) (1 / 2) ( )

2 3

2 2 4

3 2

1 / 2 ( )

1 / 2 ( )

(1 ) 1

A i

A O

A i A

9 elements but only 4 independent parameters : ,A, ,

Unitarity condition: † † 1V V V V

* * * 0ub ud cb cd tb tdV V V V V V

Measurements of the angles and sides of the triangle allow to test SM consistency 7

Unitarity triangle fit

• Importance of global fit (CKM fitter, UTfit) • Need theoretical inputs: Lattice QCD

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Search for new physics with flavour

NP contribution can be expressed as a perturbation to the SM lagrangian

If NP particles are discovered at the LHC, we are able to study the flavour

structure of the NP

Flavour physics can probe very high energy scale (even beyond the LHC

reach)

Considering the present experimental constraints in flavour physics:

• if C=1, Λ ~ O(100TeV)

• If Λ~1TeV (quantum stabilization of electroweak scale), C ~ O(10-7).

Where is this suppression coming from ?

This is the NP flavour problem. The flavour structure of NP should be

highly non trivial.

ℒ𝑒𝑓𝑓 = ℒ𝑆𝑀 +𝐶𝑁𝑃

Λ2

NP coupling

NP scale

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Search for new physics with flavour

• Sensitivity to new physics through virtual particles that can appear in loop diagrams

• Method: measure observables precisely predicted in the SM

Mixing, CP violation Rare decays

MS

NP

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The main observables

From Buras arXiv:1306.3775

Correlations between observables can constrain NP models

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LHCb

Belle2

LHCb

Belle2

CMS,ATLAS

LHCb

CMS,ATLAS

Belle2 Belle2 LHCb

Belle2

LHCb

Na62, KOTO

Belle2

LHCb

CMS,ATLAS MEG nEDM

Belle2 LHCb

Belle2

theory theory

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BES III

b (an c) physics

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LHCb • Forward spectrometer optimised for

heavy flavour physics at the LHC

– acceptance 2<η<5

– Low trigger thresholds

– Precise vertexing

– Efficient particle identification

– Large boost (B mesons flight ~1cm)

• great performances: constant luminosity 4x1032 cm-2 s-1 (2x design), µ~1.4 (nominal 0.4)

• 3 fb-1 recorded: ~300 billions of bb pairs produced in LHCb

• Lot of physics results (~220 publications)

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LHCb: some key results

93.0

1.0

1.1

0.1

0 10))()(9.2()(

syststatBBR S

Significance: 4.0 σ

• CMS obtained similar results with 25 fb-1

• Combination (arXiv:1411.4413) :

Results compatible with SM predicitons at 1.2 σ for Bs and 2.2 σ for Bd.

Deviations from SM are still possible and these analyses will be pursued with future

LHC runs

• Bs/d → +- :

First observation of Bs → +-

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LHCb: some key results

3.7 σ !

• B → K* +- :

• Decay rate depends on three angles and the dimoun mass squared q2

μ +

μ- K

Ф

B l

K

• B → Kℓ+ℓ- : test of lepton universality

2.6 σ from SM prediction, J/Ψ mode agree with SM Can be explained by Z’ models

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• Bs → J/Ψ ϕ

LHCb: some key results

• Interference between mixing and decay give rise to the CP violating phase s

Also include Bs → J/Ψ

KK, J/Ψππ, DsDs

• UT angle

LHCb Upgrade

Current LHCb trigger • No evidence for new physics in Run1: need to

improve precision.

• x(10) data required to obtain experiemental sensitivites comparable to theoretical uncertainties

Upgrade philosophy:

• Remove L0 hardware trigger, detector read out at 40 MHz instead of 1 MHz

• Use an efficient fully software trigger accessing complete event infomation

The entire read out chain and several detectors have to be replaced (large occupancy)

18 Target luminosity : 2x1033 cm-2s -1

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installation

Expected precision for the « golden modes »

LHCb-PUB-2013-015

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Belle II

• Belle: 1999-2010 , luminosity: 2.1x1034 cm-2 s-1, total recorded ~1 ab-1

• Belle II: luminosity = KEKBx40, expect to record 50 ab-1 in ~6 years

• TDR : detector arXiv:1011.0352, physics arXiv:1002.5012

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600 collaborators from 23 countries

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Expected precisions

From Snowmass report arXiv:1401.6077v1 23

Belle 2 / LHCb complementarity

Belle 2 LHCb upgrade

Statistics

Cleaness

B hadrons produced Bu, Bd, dedicated run for Bs

Bu, Bd, Bs, Bc, baryons,…

neutrino modes

Trigger bias

Some measurements can only be done by Belle2 OR LHCb necessary to have both! Cross-check and competition for common measurements

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Kaons physics • There are still things to do with

kaons! In particular rare decays*

From Snowmass report arXiv:1401.6077v1

25 *but not only.. Other measurements will be done at KLOE-2 (Frascati)

KOTO (K0 at Tokai, J-Parc)

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Goal: observe few SM events Current SES based on 100 h run in 2013 (Preliminary): 1.29 × 10 -8, same sensitivity as KEK E391a

Data taking restart in 2015, Expect “nominal” beam intensity in 2017 Upgrade planned: KOTO-2

NA62 at CERN

• Primary goal : mesure BR(K+→π+) with 10% accuracy

• Collaboration : 28 institutes, 213 collaborators

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• Big experiment: 250 m long! (fiducial volume : 60 m)

• Pilot run oct-dec 2014, restart data taking in 2015 till LS2

• Expected sensitivities :

• Possibility of a future experiment for neutral mode at CERN discussed

Charged leptons

• Anomal magnetic moment of muon:

– SM deviation > 3 sigma remains unexplained (E821, Brookhaven) :

– New experiment in Fermilab, data taking foreseen in 2017, improvement of error by a factor of 2 (http://arxiv.org/pdf/1501.03040v1.pdf)

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• Lepton flavour violation: • Conserved in SM (up to masses),

violated in most of NP models • µ→e : MEG, Mu2e, COMET • τ→ µ , τ→e : LHCb, Belle2

µ → e • 3 decays are studied, with different sensitivity to new physics models

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Susy loop diagram

Tree diagram

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µ → e : MEG (PSI)

• ~60 collaborators

• Data taking from 2009 to 2013.

Results on 2009-2011 data:

• An upgrade of MEG, aiming at a sensitivity improvement of one order of magnitude (down to 5 x 10-14) is under construction

µ → eee : Mu3e (PSI)

Present limit: 1x10-12 (SINDRUM 1988 @ SIN (PSI))

Goal: considering MEG limit, minimal goal 1x10-15. Achieving10-16 is

scientifically exciting.

• Use the PSI next generation High intensity Muon Beam project

• Need GHz beam (a few x 109 μ+/s)

• Feasibility study in 2013 – 2014

• Operation from ~2019 (?)

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µ N → e N

• Two concurrent experiments:

• Mu2e (FNAL)

– collaboration: 188 participants from 33 institutes

– Data taking will start ~2020

– Expected limit : ~6 10-17

• COMET (J-PARC)

– Collaboration: 149 participants from 33 institutes

– TDR phase 1 released in septembre 2014

– Data taking foreseen end 2016 for phase 1, 2020 for phase 2

– Expected limit phase 1: 7.2 10-15 32

Al

105 MeV

at 1s orbit

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Lot of progress expected in charged LFV in the coming years

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Possible future flavour experiments

• FCC-ee: use the huge amount of Z produced to study flavour physics (1012 Z!)

– Leptons: sterile neutrino, LFV Z →µτ, eµ, eτ, …

– Quarks: B(s,c) and baryons decays involving neutrals (B(s) →), neutrinos (B(s)→ττ), and large multiplicity (B(s) →ηc)

See talk by P. Janot

• Extreme flavour experiment:

– LHCb upgrade will be limited in luminosity.

– Would an experiment capable of exploiting the full HL-LHC lumi for flavour be conceivable ? Aim: O(100) times LHCb upgrade luminosity

– Certainly challenging but might be worth exploring

– Need also extreme theory precision

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Conclusion

2010 2020 2025

Belle 2

LHCb LHCb upgrade

NA62

KOTO

??

Broad flavour physics program for the next decade, with complementary experiments that will be able to drastically constrain new physics phase space OR

discover it! Next step is under study… 36

Activities in France

MEG2, COMET, Mu2E, Mu3E MEG

2015

B, τ charm

We are here

Kaons

Also EDM, antimatter,…

muons

BES III ? charm FCC-ee Extreme flavour ????

Année Particule CR/DR pression Total CR

2015 2 8

2014 3 2/57, 1/35 11

2013 3 2/63, 1/26 10

2012 3/1 1/164(blanc) 1/54 (LHC), 1/?

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2011 4/1 2/93 (CR1 blanc) 2/162 (CR2 blanc)

2/80 (CR2 particules)

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2010 4 13

2009 5/1 1/52, 4/63 13

2008 6 2/104,4/43 13

2007 4 4/47 14

2006 7(?) 15

Concours CNRS section 01

Source: rapports de la commission

Nombre total de poste CR

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Nombre de CR affectés en Particules

• Nombre de poste en physique des particules divisé par ~2 en 8 ans

De moins en moins d’entrants.. Qui sont de plus en plus vieux…

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Pyramide des âges in2p3

• Augmentation de l’âge d’entrée CR2: + 1,4 an entre les deux mandatures (29,1 30,3 ans) Peut-être dû aux fléchages des postes

27,528

28,529

29,530

30,531

20052006200720082009201020112012

Age moyen des CR2 à l’embauche

• (seulement) 11% des effectifs ont moins de 35 ans

Parler du futur de la physique des particules, c’est bien.. Si il n’y a plus

personne pour en faire dans 20 ans ca ne sert pas à grand-chose…

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backup

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Which new physics scale ?

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Example for operators contributiong to mixing in K, D, B, Bs decays :

If C~1 : ~(102-105 )TeV If ~1TeV: C~ 10-5-10-11

• : scale of CLFV physics

• Only to the first term is present in µ → e decay

• µ N → e N and µ → e sensitive to different new physics complementarity

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µ N → e N processus describe by:

B physics in ATLAS and CMS

• ATLAS and CMS have results on

– Spectroscopie and b hadron production

– Rare decays: Bs→µµ, B→K*µµ, Bs→J/Ψϕ

Only the CMS Bs→µµ measurement is competitive

with LHCb

• ATLAS/CMS pros: statistics

• ATLAS/CMS cons :

– Muon trigger only no radiative or hadronic modes,…

– tagging, mass resolution, PID

– futur run : trigger rate dedicated to B physics? pile-up effect ?

LHCb ATLAS,CMS

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Quelle échelle de nouvelle physique ?

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Charm physics

• Experiments :

– Babar, Belle, Belle II : Y(4s)

– CLEO-c, BES III : charm production threshold

– LHCb : charm cross section 20 times b cross section 46

• Search for new physics complementary to B, only probe of up-type quark (D mixing, CP violation, rare decays)

• Measurement of CKM elements Vcs, Vcd

• Charmonium spectroscopy: XYZ exotic states (tetraquark, meson molecule.. ?)

• Allow to validate lattice QCD computations

๏ Broad physics program

‣ Charm physics

‣ Light hadron physics

‣ Charmonium physics

‣ XYZ meson physics

‣ QCD & 𝝉-physics

‣ …

๏ Only experiment dedicated to

charm nowadays

๏ IHEP, Beijing

‣ BEPCII collider :

- beam-energy 1.0-2.3GeV

- L = 1×1033 cm-2s-1

- 2009-now : data taking

Bd→K*0+- • Decay described by 3 angles and di-muon invariant

mass squared q2

• Folding the angle (if <0, =+π ), we can reduce the number of free parameters:

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μ +

μ- K

Ф

B l

K

AFB forward-backward asymmetry FL fraction of K∗0

longitudinally polarized S3 asymmetry in K∗0

transverse polarization A9 T-odd CP

AFB zero crossing point precisely predicted in SM: q2 = 4.36+0.33-0.31 (GeV/c2)2

2

3 )1( TL AFS

Re)1(4

3TLFB AFA

Results • Analysis based on 1 fb-1, ~900 events

• Observables measured in 6 q2 bins

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arXiv:1304.6325

Accepted by JHEP

Results

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Theory from bobeth-Hiller-Van Dyk (2011), consistent with Matias et al (2013)

Good agreement with SM predictions

First measurement of zero crossing point: 422

0 /9.09.4 cGeVq

arXiv:1304.6325

Results for new observables

Good agreement with SM predictions from J. Matias et al, arXiv:1303.5794

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arXiv:1308.1707

preliminary

preliminary

preliminary

Results for new observables

3.7 σ discrepancy in the bin 4.3<q2<8.68 GeV2

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preliminary preliminary

2.5 σ discrepancy in the bin 1<q2<6 GeV2

Could be interpreted as NP contribution in Wilson coefficients C9 and C7 (arXiv:1308.101, arXiv:1307.5683)

Several b → s measurements used in this fit

New observables • Observables with limited dependence on form-factors uncertainty have been

proposed by several theorists

• Different set of observables give different constraints complementarity!

• Use different folding to measure each P’i

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moment dipolaire électrique (EDM)

• l’observation d’un EDM plus grand que la prédiction du MS serait une preuve de l’existence de nouvelle sources de violation CP et de nouvelle physique

• Mesures faites sur les électrons, les neutrons ou les atomes

• Complémentaires car sensible a différentes source de violation de CP

• Plusieurs expériences en cours ou dans un futur proche (6 pour les neutrons)

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Expérience nEDM (PSI)

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utilise les neutrons ultra froids

~50 physiciens

3 labos français : LPC Caen, LPSC Grenoble, CSNSM

nEDM en cours de prise de donnée :

en 2013 σ ~ 6.10-26 e.cm,

but final σ ~ 5.10-27 e.cm

Projet n2EDM : une limite proche de 10-27e cm devrait être atteinte après 5 années de prises de données, soit aux alentours de 2020 (conseil scientifique IN2P2 en octobre 2013)

Contraintes des mesures à basse énergie dans un scenario de split SUSY (arXiv:1308.3653)

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LHCb results Justine Serrano 58

b → s implications: bound on Wilson coefficients

• Several studies, ex: Straub et al, arXiv:1206.0273

• Model independent constraint Ci = CiSM +Ci

NP

• Over constraint Wilson coefficients with many measurements in a global fit

BR(B →Xsll) BR(B →Xs) B →K*μμ BR(Bs →μμ) BR(B →Kμμ)

Red: Combined 1σ,2σ constraints

ACP(b →s)

Wilson coefficients compatible with their SM values at 95%CL

https://indico.in2p3.fr/getFile.py/access?resId=0&materialId=slides&contribId=10&sessionId=1&subContId=1&confId=7502

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Extreme flavour experiment Talk by v. Vagnoni at workshop « The landscape of Flavour Physics towards the high intensity era”