We confront the indications of lepton flavor universality (LFU) violation observed in semi-tauonic B meson decays with new physics (NP) searches using high pT tau leptons at the LHC. Using effective ...field theory arguments we correlate possible non-standard contributions to semi-tauonic charged currents with the τ+τ− signature at high energy hadron colliders. Several representative standard model extensions put forward to explain the anomaly are examined in detail: (i) weak triplet of color-neutral vector resonances, (ii) second Higgs doublet and (iii) scalar or (iv) vector leptoquark. We find that, in general, τ+τ− searches pose a serious challenge to NP explanations of the LFU anomaly. Recasting existing 8 TeV and 13 TeV LHC analyses, stringent limits are set on all considered simplified models. Future projections of the τ+τ− constraints as well as caveats in interpreting them within more elaborate models are also discussed.
We show that new physics models without new flavor violating interactions can explain the recent anomalies in the b→sℓ+ℓ− transitions. The b→sℓ+ℓ− arises from a Z′ penguin which automatically ...predicts the V−A structure for the quark currents in the effective operators. This framework can either be realized in a renormalizable U(1)′ setup or be due to new strongly interacting dynamics. The dimuon resonance searches at the LHC are becoming sensitive to this scenario since the Z′ is relatively light, and could well be discovered in future searches by ATLAS and CMS.
A
bstract
We explore the interplay of New Physics (NP) effects in (
g
−
2)
ℓ
and
h
→
ℓ
+
ℓ
−
within the Standard Model Effective Field Theory (SMEFT) framework, including one-loop Renormalization ...Group (RG) evolution of the Wilson coefficients as well as matching to the observables below the electroweak symmetry breaking scale. We include both the leading dimension six chirality flipping operators including a Higgs and SU(2)
L
gauge bosons as well as four-fermion scalar and tensor operators, forming a closed operator set under the SMEFT RG equations. We compare present and future experimental sensitivity to different representative benchmark scenarios. We also consider two simple UV completions, a Two Higgs Doublet Model and a single scalar LeptoQuark extension of the SM, and show how tree level matching to SMEFT followed by the one-loop RG evolution down to the electroweak scale can reproduce with high accuracy the (
g
−
2)
ℓ
and
h
→
ℓ
+
ℓ
−
contributions obtained by the complete one- and even two-loop calculations in the full models.
Present measurements of b→cτν and b→uτν transitions differ from the standard model predictions of lepton flavor universality by almost 4σ. We examine new physics interpretations of this anomaly. An ...effective field theory analysis shows that minimal flavor violating models are not preferred as an explanation, but are also not yet excluded. Allowing for general flavor violation, right-right vector and right-left scalar quark currents are identified as viable candidates. We discuss explicit examples of two Higgs doublet models, leptoquarks as well as quark and lepton compositeness. Finally, implications for LHC searches and future measurements at the (super-)B factories are presented.
We extend the use of Classification Without Labels for anomaly detection with a hypothesis test designed to exclude the background-only hypothesis. By testing for statistical independence of the two ...discriminating dataset regions, we are able to exclude the background-only hypothesis without relying on fixed anomaly score cuts or extrapolations of background estimates between regions. The method relies on the assumption of conditional independence of anomaly score features and dataset regions, which can be ensured using existing decorrelation techniques. As a benchmark example, we consider the LHC Olympics dataset where we show that mutual information represents a suitable test for statistical independence and our method exhibits excellent and robust performance at different signal fractions even in presence of realistic feature correlations.
Uncovering latent jet substructure Dillon, Barry M.; Faroughy, Darius A.; Kamenik, Jernej F.
Physical review. D,
09/2019, Volume:
100, Issue:
5
Journal Article
Peer reviewed
Open access
We apply techniques from Bayesian generative statistical modeling to uncover hidden features in jet substructure observables that discriminate between different a priori unknown underlying short ...distance physical processes in multijet events. In particular, we use a mixed membership model known as latent Dirichlet allocation to build a data-driven unsupervised top-quark tagger and tt¯ event classifier. We compare our proposal to existing traditional and machine learning approaches to top-jet tagging. Finally, employing a toy vector-scalar boson model as a benchmark, we demonstrate the potential for discovering new physics signatures in multijet events in a model independent and unsupervised way.
A
bstract
Motivated by the tantalizing excesses recently reported in the di-photon invariant mass spectrum at the LHC, we scrutinize some implications of scalar di-photon resonances in high energy ...proton-proton collisions. In particular, indications of a large width impose several challenges for model building. We show how calculability and unitarity considerations severely limit possible perturbative realizations of such a signal and propose a simple criterion that can be adapted to any renormalizable model. Furthermore, we discuss correlations between a di-photon excess and precision observables, including the anomalous magnetic and electric dipole moments of quarks and leptons, neutral meson oscillations and radiative flavor changing neutral current mediated decays of heavy leptons and hadrons. We find that existing searches and measurements significantly constrain the possibilities for a scalar resonance decaying into final states involving Standard Model fermions. We propose future search strategies which could elucidate some remaining currently unconstrained decay channels and discuss possible correlations between the di-photon excess and several recently reported flavor anomalies, showing that the latter can be addressed in a new incarnation of a gauged U(1)
′
model, with the di-photon resonance being the physical remnant of the U(1)
′
-breaking field.
We study the constraints implied by partial wave unitarity on new physics in the form of spin-zero di-boson resonances at LHC. We derive the scale where the effective description in terms of the SM ...supplemented by a single resonance is expected to break down depending on the resonance mass and signal cross section. Likewise, we use unitarity arguments in order to set perturbativity bounds on renormalizable UV completions of the effective description. We finally discuss under which conditions scalar di-boson resonance signals can be accommodated within weakly coupled models.
Collider constraints on light pseudoscalars Haisch, Ulrich; Kamenik, Jernej F.; Malinauskas, Augustinas ...
The journal of high energy physics,
03/2018, Volume:
2018, Issue:
3
Journal Article
Peer reviewed
Open access
A
bstract
We investigate the bounds on light pseudoscalars that arise from a variety of collider searches. Special attention is thereby devoted to the mass regions
3
,
5
GeV and
9
,
11
GeV, in ...which a meaningful theoretical description has to include estimates of non-perturbative effects such as the mixing of the pseudoscalar with QCD bound states. A compendium of formulas that allows to deal with the relevant corrections is provided. It should prove useful for the interpretation of future LHC searches for light CP-odd spin-0 states.
What is the gamma gamma resonance at 750 GeV? Franceschini, Roberto; Giudice, Gian F; Kamenik, Jernej F ...
The journal of high energy physics,
03/2016, Volume:
2016, Issue:
3
Journal Article
Peer reviewed
Open access
Run 2 LHC data show hints of a new resonance in the diphoton distribution at an invariant mass of 750 GeV. We analyse the data in terms of a new boson, extracting information on its properties and ...exploring theoretical interpretations. Scenarios covered include a narrow resonance and, as preliminary indications suggest, a wider resonance. If the width indications persist, the new particle is likely to belong to a strongly-interacting sector. We also show how compatibility between Run 1 and Run 2 data is improved by postulating the existence of an additional heavy particle, whose decays are possibly related to dark matter.
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