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”