Publications

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Non-Standard neutrino interactions and neutral gauge bosons

Julian Heeck, Manfred Lindner, Werner Rodejohann, Stefan Vogl

SciPost Phys. 6, 038 (2019) · published 27 March 2019 | · pdf

We investigate Non-Standard Neutrino Interactions (NSI) arising from a flavor-sensitive $Z'$ boson of a new $U(1)'$ symmetry. We compare the limits from neutrino oscillations, coherent elastic neutrino--nucleus scattering, and $Z'$ searches at different beam and collider experiments for a variety of straightforward anomaly-free $U(1)'$ models generated by linear combinations of $B-L$ and lepton-family-number differences $L_\alpha-L_\beta$. Depending on the flavor structure of those models it is easily possible to avoid NSI signals in long-baseline neutrino oscillation experiments or change the relative importance of the various experimental searches. We also point out that kinetic $Z$-$Z'$ mixing gives vanishing NSI in long-baseline experiments if a direct coupling between the $U(1)'$ gauge boson and matter is absent. In contrast, $Z$-$Z'$ mass mixing generates such NSI, which in turn means that there is a Higgs multiplet charged under both the Standard Model and the new $U(1)'$ symmetry.

52 citations
QCD or what?

Theo Heimel, Gregor Kasieczka, Tilman Plehn, Jennifer M Thompson

SciPost Phys. 6, 030 (2019) · published 8 March 2019 | · pdf

Autoencoder networks, trained only on QCD jets, can be used to search for anomalies in jet-substructure. We show how, based either on images or on 4-vectors, they identify jets from decays of arbitrary heavy resonances. To control the backgrounds and the underlying systematics we can de-correlate the jet mass using an adversarial network. Such an adversarial autoencoder allows for a general and at the same time easily controllable search for new physics. Ideally, it can be trained and applied to data in the same phase space region, allowing us to efficiently search for new physics using un-supervised learning.

121 citations
The Global Higgs Picture at 27 TeV

Anke Biekoetter, Dorival Gonçalves, Tilman Plehn, Michihisa Takeuchi, Dirk Zerwas

SciPost Phys. 6, 024 (2019) · published 25 February 2019 | · pdf

We estimate the reach of global Higgs analyses at a 27 TeV hadron collider in terms of Higgs couplings and in terms of a gauge-invariant effective Lagrangian, including invisible Higgs decays and the Higgs self-coupling. The new collider will indirectly probe new physics in the TeV range and allow for a meaningful test of the Higgs self-coupling also embedded in a global analysis.

9 citations
The rare and forbidden: Testing physics beyond the standard model with Mu3e

Ann-Kathrin Perrevoort on behalf of the Mu3e Collaboration

SciPost Phys. Proc. 1, 052 (2019) · published 22 February 2019 | · pdf

The upcoming Mu3e experiment aims to search for the lepton flavour violating decay $\mu^+ \to e^+ e^- e^+$ with an unprecedented final sensitivity of one signal decay in $10^{16}$ observed muon decays by making use of an innovative experimental design based on novel ultra-thin silicon pixel sensors. In a first phase, the experiment is operated at an existing muon beam line with rates of up to $10^8$ muons per second. Detailed simulation studies confirm the feasibility of background-free operation and project single event sensitivities in the order of $10^{-15}$ for signal decays modelled in an effective field theory approach. The precise tracking of the decay electrons and large geometric and momentum acceptance of Mu3e enable searches for physics beyond the Standard Model in further signatures. Examples of which are searches for lepton flavour violating two-body decays of the muon into an electron and an undetected boson as well as for electron-positron resonances in $\mu^+ \to e^+ e^- e^+ \bar{\nu}_\mu \nu_e$ which could result for instance from a dark photon decay. The Mu3e experiment is expected to be competitive in all of these channels already in phase I.

15 citations
Renormalization-group improvement in hadronic $τ$ decays in 2018

Diogo Boito, Pere Masjuan, Fabio Oliani

SciPost Phys. Proc. 1, 049 (2019) · published 22 February 2019 | · pdf

One of the main sources of theoretical uncertainty in the extraction of the strong coupling from hadronic tau decays stems from the renormalization group improvement of the series. Perturbative series in QCD are divergent but are (most likely) asymptotic expansions. One needs knowledge about higher orders to be able to choose the optimal renormalization-scale setting procedure. Here, we discuss the use of Pad\'e approximants as a model-independent and robust method to extract information about the higher-order terms. We show that in hadronic \boldmath $\tau$ decays the fixed-order expansion, known as fixed-order perturbation theory (FOPT), is the most reliable mainstream method to set the scale. This fully corroborates previous conclusions based on the available knowledge about the leading renormalon singularities of the perturbative series.

1 citation
Sensitivity on the electromagnetic dipole moments of the tau-lepton at the CLIC

Maria de los Ángeles Hernández-Ruíz, Ahmet A. Billur, Murat Köksal, Alejandro Gutiérrez-Rodríguez

SciPost Phys. Proc. 1, 045 (2019) · published 22 February 2019 | · pdf

In this paper we established model independent bounds on the anomalous magnetic and electric dipole moments of the tau-lepton using the process $\gamma\gamma \to \tau^+\tau^-}$. We use data collected with the future $e^+ e^-$ linear collider such as the CLIC at $\sqrt{s}$ = 380, 1500, 3000 GeV, and we consider systematic uncertainties of $\delta_{sys}$ = 0$\%$, 3$\%$, 5$\%$. The theory predictions are a very good prospect for probing the dipole moments of the tau-lepton at the future $e^ + e^-$ linear collider at the $\gamma\gamma$ mode.
Prospects of measurements on the anomalous magnetic and electric dipole moments of the $\tau$-neutrino in $pp$ collisions at the LHC

Alejandro Gutiérrez-Rodríguez, Murat Köksal, Ahmet A. Billur, Maria de los Ángeles Hernández-Ruíz

SciPost Phys. Proc. 1, 044 (2019) · published 22 February 2019 | · pdf

In this paper the production cross-section $pp\rightarrow (\gamma, Z) \to \nu_\tau \bar \nu_\tau \gamma+X$ in $pp$ collisions at $\sqrt{s}=13, 14, 33\hspace{0.8mm}TeV$ is presented. Furthermore, we estimate bounds at the $95\%$ C.L. on the dipole moments of the $\tau$-neutrino using integrated luminosity of ${\cal L}= 100, 500, 1000, 3000 \hspace{0.8mm}fb^{-1}$ collected with the ATLAS detector at the LHC and we consider systematic uncertainties of $\delta_{sys} = 0\%, \, 5\%, \,10\%$. We found that the current and future LHC bounds are weaker than other experiments reported in the literature. However, it is shown that the process under consideration is a good prospect for probing the dipole moments of the $\tau$-neutrino at the LHC.
Tau-decay determination of the strong coupling

Antonio Pich

SciPost Phys. Proc. 1, 036 (2019) · published 21 February 2019 | · pdf

We review the current status of the determination of the strong coupling from tau decay. Using the most recent release of the ALEPH data, a very comprehensive phenomenological analysis has been performed, exploring all strategies previously considered in the literature and several complementary approaches. Once their actual uncertainties are properly assessed, the results from all adopted methodologies are in excellent agreement, leading to a very robust and reliable value of the strong coupling, $\alpha_s^{(n_f=3)}(m_\tau^2) = 0.328\pm 0.013$, which implies $\alpha_s^{(n_f=5)}(M_Z^2) = 0.1197\pm 0.0015$.

3 citations
Light sterile neutrinos: a critical overview

Ivan Esteban

SciPost Phys. Proc. 1, 026 (2019) · published 20 February 2019 | · pdf

Light sterile neutrinos, first proposed after the results of the LSND experiment, have been a polemical topic for the last decades after seemingly contradictory data appeared from different experiments. In this overview, I review the experimental hints that point towards sterile neutrinos as well as their statistical compatibility. Even though the muon neutrino disappearance experiments strongly rule out vanilla sterile neutrinos, each oscillation channel remains internally mostly consistent. In any case, in the near future a series of independent and precise experiments should finally settle down this issue.
LHC searches motivated by recent $B$-anomalies

Darius Alexander Faroughy

SciPost Phys. Proc. 1, 021 (2019) · published 19 February 2019 | · pdf

We discuss the physics case for the LHC motivated by the $B$-physics anomalies. After correlating semi-tauonic $B$ decays to di-tau production at the LHC, and discussing the possible models solving the $B$-anomalies, we show how existing LHC data in $\tau\bar\tau$ tails exclude most beyond the SM scenarios except for a handful of leptoquark (LQ) models. We analyze the impact of LHC searches for some of these LQ solutions using current data. In particular, we focus on the well known $U_1$ vector LQ as well as the GUT-inspired scalar LQs, $R_2$ and $S_3$. By exploiting the complementarity between di-tau searches and the lepton flavor violating decays $B\to K\mu\tau$ and $\tau\to\mu\phi$ we argue that these model can be cornered by the LHC, Belle~II and LHCb in the near future.

2 citations

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