Quark flavour observables in 331 models in the flavour precision era
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Transcript of Quark flavour observables in 331 models in the flavour precision era
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Quark flavour observables in 331 models in the flavour precision era
Fulvia De FazioINFN- Bari
• the flavour precision era• a NP scenario to look at flavour observables: 331 model• conclusions
Based onA.J. Buras, J. Girrbach, M.V. Carlucci,FDF
JHEP 1302 (2013) 023
EPS HEP 2013 Stockholm
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Flavour Precision Era (FPE): working assumptions
• CKM parameters have been determined by means of tree-level decays• Non-perturbative parameters are affected by very small uncertainties and fixed
Two scenarios
1. |Vub| fixed to the exclusive (smaller) value2. |Vub| fixed to the inclusive (larger) value
Using g 68° :
|Vub| in scenario 1 |Vub| in scenario 2 requires NP enhancing B(B t nt) no NP required for B(B t nt) reproduces the experimental value for SJ/yKs SJ/yKs higher than experimentsuppresses eK w.r.t. experiment eK consistent with experiment
DMs,d agree within uncertainties, slightly preferring models predicting a small suppression
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331 Model: general features
Gauge group: SU(3)C X SU(3)L X U(1)X
Spontaneously broken to SU(3)C X SU(2)L X U(1)X
Spontaneously broken to SU(3)C X U(1)QNice
features:• requirement of anomaly cancelation + asympotic freedom of QCD implies
number of generations= number of colors• two quark generations transform as triplets under SU(3)L , one as an antitriplet
this may allow to understand why top mass is so large
Fundamental relation: XTTQ 83
Key parameter: defines the variant of the model
=13 (331 variant)• leads to interesting phenomenology• new gauge bosons have integer charges
P. Frampton, PRL 69 (92) 2889F. Pisano & V. Pleitez, PRD 46 (92) 410
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331 Model: new particle content
New Gauge Bosons
ZVV
Y
00 ,
Singly charged
Neutral
Neutral
Mediates tree level FCNC in the quark sector(couplings to leptons are universal)
Extended Higgs sector Three SU(3)L triplets, one sextet
New heavy fermions D,S new heavy quarks with Q=-1/3
T new heavy quark with Q=2/3
El new heavy neutrinos (both L & R)
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331 Model: quark mixing
Quark mass eigenstates defined upon rotation through two unitary matrices UL & VL
In contrast to SM only one of them can be traded for VCKM, the other one enters in Z’ couplings to quarks
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331 Model: Z’ couplings to quarksThe case of Bd,Bs,K systems
depend only on four new parameters:
stringent correlations between observables expected
Bd system only on s13 and d1
Bs system only on s23 and d2
K system on s13 , s23 and d2 - d1
FCNC involve onlyleft-handed quarks
We fix 1MZ’ 3 TeV
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Oases in the parameter space from DF=2 observables
Imposing the experimental constraints:
One finds the allowed oases for the parameters s13 , s23 >0 & 0<d23<2p 0<d13<2p
Example of NP contribution: The case of Bd mixing
DMs
Mass difference in the B̅s –Bs system
Syf CP asymmetry in
Bs J/y f
DMd
Mass difference in the B̅d –Bd system
SyKs
CP asymmetry in Bd J/y Ks
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Oases in the parameter space from DF=2 observables
A1
A3
A2
A4
A1
B1
B3B4
B2
Small oases in Bs case can be eliminated by data on the mixing phase and on eK
Other observables should be considered to find the optimal oasis
Blue regions Syf
Red ones DMs
Blue regions SyKs Red ones DMd
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The decay Bs m+ m-
SM effective hamiltonian one master function Y0(xt)
Z’ contribution modifies this function to:
a new phase
independent on the decaying meson and on the lepton flavour
Theoretically clean observable:
the new phase involved
LHCb 1211.2674 SM
phase of the function S entering in the box diagramvanishes in SM
Analogous observables can be considered in the Bd case
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Searching for the optimal oasis
A1,B3
A1,B1
A3,B3
A3,B1 B1 B3
From both Bs and Bd systems
Observables in Bd system
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Searching for the optimal oasis
A3
A1
Triple correlation in Bs system
Test of the model: Once the sign of Ss
m+m- is determined the model uniquely predicts the correlation between Syf and B(Bs m+m-)
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Correlations with eK
It is possible to reproduce DMs, DMd and find eK consistent with experiment
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Conclusions
• Dominant NP contributions in 331 model come from tree-level Z’ exchanges
• The model can remove the tensions between SM and experiment when 1 TeV MZ’ 3 TeV
• The parameters of the model reproduce DF=2 observables in restricted oases
• The optimal oasis can be selected looking at other obervables and correlations among them
• A triple correlation in the Bs system has been identified as a valuable test of the model
• Increasing the mass of Z’ it is still possible to find oases where the DF=2 constraints are OK however some observables receive very small NP contributions (rare decays)