Results on flavor anomalies at ATLAS and CMSStefano Giagu - Sapienza Università di Roma and INFN for the ATLAS and CMS Collaborations

ALPS 2018 - April 15-20th, 2018

Introduction & Outline• Rare FCNC decays have always been a powerful probe to search for New Physics effects:

• virtual effects in loops makes them complementary with direct searches

• Standard Model effects are tiny, new physics if present competitive in magnitude

• Standard Model predictions relatively accurate when compared with current statistical precision

• In this brief talk:

• review of the most recent results from ATLAS and CMS on b→sµµ angular analyses and Bs/Bd→µµ branching fraction measurements

"2NOTE: only a small and partial subset of all the flavour physics results from ATLAS and CMS presented here. Full and daily updated list of results from collider experiments, with details on each analysis, available here:

https://twiki.cern.ch/twiki/bin/view/AtlasPublic/BPhysPublicResults https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsBPH

B0→K*µµ angular analysis• b→sl+l- decays like B0→K*µ+µ- proceed in the SM via FCNC and offer several

observables which probe helicity structure of the process and sensitivity to NP

• the process can be fully described by the three angles (θl, θk, φ) and the di-muon invariant mass squared q2

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FL, P and P' parameters sensitive to new physics entering the loops chosen in order to be the

less sensitive to theoretical uncertainties at LO

Experimental challenge: • low statistic process and multidimensional pdf model

• fold the signal model using its symmetries to reduce complexity and improve convergence

• ATLAS: neglect non resonant S-wave component (few %)

• CMS: fit only for P1 and P’5, fixing the other parameters from previous measurements

• BOTH: use large B0→K*J/ψ and B0→K*ψ(2s) control samples to constraint K*µµ invariant mass model parameters

B0→K*µµ

"4

ATLAS-CONF-2017-023 CMS: arXiv:1710.02846

B0→K*J/ψ

B0→K*µµ• latest results from ATLAS and CMS based on ~20/fb of 8 TeV data taken in 2012

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CMS

ATLAS

[4.3,6.0] GeV2

[0.04,6.0] GeV2

ATLAS-CONF-2017-023 CMS: arXiv:1710.02846

simultaneous fit projections

B0→K*µµ

"6results statistically limited …

DHMV/JC: QCD factorization, hadronic uncertainties from calculationsHEPfit/CFFMPSV: hadronic charm contributions fitted from LHCb data

• CMS: consistent with SM predictions in the whole range of q2, DHMV predictions favoured at low q2

• ATLAS: generally good agreement with SM except a +2.5σ deviation on P’5 and P’4 in the 4-6 GeV2 q2 bin

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B+→K+µµ• Just released by CMS: based on 20.5/fb taken at 8 TeV in 2012 run • two model-independent parameters describe the decay rate:

• forward-backward asymmetry of the di-muon system: AFB • contribution from pseudo-scalar, scalar, and tensor amplitudes to the decay width: FH

• both can be measured via angular analysis

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CMS-PAS-BPH-15-001

B+→K+µµ• Results in agreement with the SM • large statistical uncertainties for q2 < 2 GeV2

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Bs→µµFlagship of HF rare decays:

• FCNC and helicity suppressed, extremely rare in SM (BR~4×10-9) and sensitive to NP (SUSY, 2HDM, …) • theoretically and experimentally clean

• Observed in combined LHCb+CMS analysis in Run-, recent Run-2 result from LHCb with >5σ evidence for a single experiment and measurement of effective lifetime

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Bs→µµ• ATLAS search based on full Run-1 statistic and ML discriminants didn’t brought at a significant signal yet

• result slightly in tension with CMS+LHCb but compatible with SM at 2σ

"10

ATLAS: Eur. Phys. J. C 76 (2016) 513

• EFT and OPE: describe complex b→s transitions with point-like interactions, effects of large scale contained in effective couplings

• O9, O10 describes vector and axial-vector contributions and are SM, all other operators are BSM

• NP can add new operators and/or modify the Wilson coefficients

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Parametrise sensitivity to NP in rare decays in a model independent way

Ci: Wilson coefficients (short distance effects)

Oi: Local OperatorsC’O’: right handed terms

(suppressed in SM)

(pseudo)-scalar NP contributions

Theory interpretation• ATLAS and CMS results compared with LHCb in the EFT framework • combination favours a modified SM vector-current • possible effects of underestimated QCD uncertainties cannot be ruled out at this time

"12in each 2D plot all other Wilson coefficients assumed to be SM-like

W.Altmannshofer, C.Niehoff, P.Stangl, D.M.Straub: arXiv:1703.09189

Other flavor-physics related studies: • A wide set of other HF measurements and NP searches ongoing

in ATLAS and CMS • so far everything consistent with the Standard Model • updated results with 13 TeV Run-2 datasets expected soon

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CP violating phase in Bs→J/ψΦ • sensitive to NP, and effects in the

mixing vs b→scc decay amplitudes

ΔΓd/Γd in Bd→J/ψKs and J/ψK* • best single measurement to date: ΔΓd/Γd=(-0.1±1.1±0.9)×10-2 • consistent with SM

Search for 3rd generation scalar LQ → tτ • may provide explanation for the flavour

anomalies observed by LHCb and B-factories

ATLAS: JHEP06 (2016) 081 CMS: CMS-B2G-16-028

ATLAS: JHEP 08 (2016) 147 CMS: Phys. Lett. B 757 (2016) 97

Conclusions• Current flavour anomalies observed in B-factories and LHCb may be interpreted

in global fits as modifications in the C9 and C10 coefficients (predominantly V-A type), but effects from hadronic uncertainties cannot be ruled out at this time

• ATLAS and CMS have a rich heavy-flavour physics program going on that will help to constraint global fits and to complement measurements provided by dedicated HF experiments

• so far tests performed on Run-1data are consistent with the SM … but statistical uncertainties dominate overall accuracy

• much larger Run-2 datasets under analysis now and several new results will come soon to shed new light in these exciting results

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Additional slides

The experimental tools: di-muon spectrum• in ATLAS and CMS the reconstruction of heavy flavour processes relies mostly in muon and

central tracking detectors

• highly efficient and high resolution single/di/multi-muon triggers allow to collect both low-rate signals and very large samples of calibrations/normalisation processes

"16CMS-DP-2017-029 ATLAS: B-phys PUB

Global Fits: b→sµµ VS RK/LFU

"17W.Altmannshofer, P.Stangl, D.M.Straub: Phys. Rev. D 96, 055008 (2017)

Global Fits: Bs→µµ today and perspectives

"18W.Altmannshofer, C.Niehoff, D.M.Straub: arXiv:1702.05498

Systematic uncertanties:

B0→K*µµ

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ATLAS-CONF-2017-023 CMS: arXiv:1710.02846

CMS

ATLAS