We present a proposal for a future light dark matter search experiment at the Electron Stretcher Accelerator ELSA in Bonn: . It employs the fixed-target missing momentum based technique for searching for dark-sector particles. The experiment uses a beam of electrons that is extracted from the ELSA accelerator and that is shot onto a thin target to produce mainly Standard Model bremsstrahlung and – in rare occasions – possibly new particles coupling feebly to the electron. A well motivated candidate for such a new particle is the dark photon, a new, possibly massive gauge boson arising from a new gauge interaction in a dark sector and mixing kinetically with the Standard Model photon. The experiment is estimated to reach sensitivity to couplings small enough to explain the relic abundance of dark matter in various models for dark photon masses between $$\sim 1 $$ and $$\sim {100\,\mathrm{\text {M}\text {eV}}}$$ .

Germany

Philip Bechtle

Christian Bespin

France

Dominique Breton

Spain

Carlos Orero Canet

Klaus Desch

Herbi Dreiner

Oliver Freyermuth

Rhorry Gauld

Markus Gruber

César Gutiérrez

Hazem Hajjar

Matthias Hamer

Jan-Eric Heinrichs

Adrian Irles

Jochen Kaminski

Laney Klipphahn

Hans Krüger

Michael Lupberger

Jihane Maalmi

Roman Pöschl

Dennis Proft

Norway

Leonie Richarz

Tobias Schiffer

Patrick Schwäbig

Martin Schürmann

Dirk Zerwas

A proposal for the

The program HiggsSignals confronts the predictions of models with arbitrary Higgs sectors with the available Higgs signal rate and mass measurements, resulting in a likelihood estimate. A new version of the program, HiggsSignals-2, is presented that contains various improvements in its functionality and applicability. In particular, the new features comprise improvements in the theoretical input framework and the handling of possible complexities of beyond-the-SM Higgs sectors, as well as the incorporation of experimental results in the form of simplified template cross section (STXS) measurements. The new functionalities are explained, and a thorough discussion of the possible statistical interpretations of the HiggsSignals results is provided. The performance of HiggsSignals is illustrated for some example analyses. In this context the importance of public information on certain experimental details like efficiencies and uncertainty correlations is pointed out. HiggsSignals is continuously updated to the latest experimental results and can be obtained at  https://gitlab.com/higgsbounds/higgssignals  .

Sven Heinemeyer

Tobias Klingl

Tim Stefaniak

Georg Weiglein

Sweden

Jonas Wittbrodt

HiggsSignals-2: probing new physics with precision Higgs measurements in the LHC 13 TeV era

We describe recent developments of the public computer code HiggsBounds. In particular, these include the incorporation of LHC Higgs search results from Run 2 at a center-of-mass energy of 13 TeV, and an updated and extended framework for the theoretical input that accounts for improved Higgs cross section and branching ratio predictions and new search channels. We furthermore discuss an improved method used in HiggsBounds to approximately reconstruct the exclusion likelihood for LHC searches for non-standard Higgs bosons decaying to  $$\tau \tau $$  <math> <mrow> <mi>τ</mi> <mi>τ</mi> </mrow> </math>   final states. We describe in detail the new and updated functionalities of the new version HiggsBounds-5.

Daniel Dercks

HiggsBounds-5: testing Higgs sectors in the LHC 13 TeV Era

The   <math> <mi>CP</mi> </math>  $$ \mathcal{CP} $$  structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the   <math> <mi>CP</mi> </math>  $$ \mathcal{CP} $$ -nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant   <math> <mi>CP</mi> </math>  $$ \mathcal{CP} $$ -odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the   <math> <mi>CP</mi> </math>  $$ \mathcal{CP} $$  properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the   <math> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> <mi>H</mi> </math>  $$ t\overline{t}H $$  rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone.

Henning Bahl

Judith Katzy

Krisztian Peters

CERN

Matthias Saimpert

Indirect   <math> <mi>CP</mi> </math>  $$ \mathcal{CP} $$  probes of the Higgs-top-quark interaction: current LHC constraints and future opportunities

The prediction of additional Higgs bosons is one of the key features of physics beyond the Standard Model (SM) that gives rise to an extended Higgs sector. We assess the sensitivity of the Large Hadron Collider (LHC) in the high luminosity (HL) run alone and in combination with a possible future International Linear Collider (ILC) to probe heavy neutral Higgs bosons. We employ the Minimal Supersymmetric Standard Model (MSSM) as a framework and assume the light  $$\mathcal {CP}$$  <math> <mi>CP</mi> </math>  -even MSSM Higgs boson to be the Higgs boson observed at  $$125\,\mathrm{GeV}$$  <math> <mrow> <mn>125</mn> <mspace width="0.166667em"></mspace> <mi>GeV</mi> </mrow> </math>  . We discuss the constraints on the MSSM parameter space arising from the precision measurements of the rates of the detected signal at  $$125\,\mathrm{GeV}$$  <math> <mrow> <mn>125</mn> <mspace width="0.166667em"></mspace> <mi>GeV</mi> </mrow> </math>   and from direct searches for new heavy Higgs bosons in the  $$\tau ^+\tau ^-$$  <math> <mrow> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msup> <mi>τ</mi> <mo>-</mo> </msup> </mrow> </math>  ,  $$b\bar{b}$$  <math> <mrow> <mi>b</mi> <mover> <mrow> <mi>b</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>   and di-Higgs (hh) final states. A new benchmark scenario for heavy Higgs searches in the  $$b\bar{b}$$  <math> <mrow> <mi>b</mi> <mover> <mrow> <mi>b</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>   channel is proposed in this context. For the future Higgs rate measurements at the HL-LHC and ILC two different scenarios are investigated, namely the case where the future rate measurements agree with the SM prediction and the case where the rates agree with the predictions of possible realizations of the MSSM Higgs sector in nature.

Stefan Liebler

HL-LHC and ILC sensitivities in the hunt for heavy Higgs bosons

SCYNet (SUSY Calculating Yield Net) is a tool for testing supersymmetric models against LHC data. It uses neural network regression for a fast evaluation of the profile likelihood ratio. Two neural network approaches have been developed: one network has been trained using the parameters of the 11-dimensional phenomenological Minimal Supersymmetric Standard Model (pMSSM-11) as an input and evaluates the corresponding profile likelihood ratio within milliseconds. It can thus be used in global pMSSM-11 fits without time penalty. In the second approach, the neural network has been trained using model-independent signature-related objects, such as energies and particle multiplicities, which were estimated from the parameters of a given new physics model.

Sebastian Belkner

Tim Keller

Michael Krämer

Björn Sarrazin

Jan Schütte-Engel

Jamie Tattersall

SCYNet: testing supersymmetric models at the LHC with neural networks

We perform a parameter scan of the phenomenological Minimal Supersymmetric Standard Model (pMSSM) with eight parameters taking into account the experimental Higgs boson results from Run I of the LHC and further low-energy observables. We investigate various MSSM interpretations of the Higgs signal at 125GeV . First, we consider the case where the light CP -even Higgs boson of the MSSM is identified with the discovered Higgs boson. In this case it can impersonate the SM Higgs-like signal either in the decoupling limit , or in the limit of alignment without decoupling . In the latter case, the other states in the Higgs sector can also be light, offering good prospects for upcoming LHC searches and for searches at future colliders. Second, we demonstrate that the heavy CP -even Higgs boson is still a viable candidate to explain the Higgs signal – albeit only in a highly constrained parameter region, that will be probed by LHC searches for the CP -odd Higgs boson and the charged Higgs boson in the near future. As a guidance for such searches we provide new benchmark scenarios that can be employed to maximize the sensitivity of the experimental analysis to this interpretation.

United States

Howard E. Haber

Oscar Stål

Netherlands

Lisa Zeune

The light and heavy Higgs interpretation of the MSSM

We investigate the constrained Minimal Supersymmetric Standard Model (cMSSM) in the light of constraining experimental and observational data from precision measurements, astrophysics, direct supersymmetry searches at the LHC and measurements of the properties of the Higgs boson, by means of a global fit using the program Fittino . As in previous studies, we find rather poor agreement of the best fit point with the global data. We also investigate the stability of the electro-weak vacuum in the preferred region of parameter space around the best fit point. We find that the vacuum is metastable, with a lifetime significantly longer than the age of the Universe. For the first time in a global fit of supersymmetry, we employ a consistent methodology to evaluate the goodness-of-fit of the cMSSM in a frequentist approach by deriving p values from large sets of toy experiments. We analyse analytically and quantitatively the impact of the choice of the observable set on the p value, and in particular its dilution when confronting the model with a large number of barely constraining measurements. Finally, for the preferred sets of observables, we obtain p values for the cMSSM below 10Â %, i.e. we exclude the cMSSM as a model at the 90Â % confidence level.

José Eliel Camargo-Molina

Herbert K. Dreiner

Brazil

Ben O’Leary

Werner Porod

Mathias Uhlenbrock

Peter Wienemann

Killing the cMSSM softly

LHC searches for non-standard Higgs bosons decaying into tau lepton pairs constitute a sensitive experimental probe for physics beyond the Standard Model (BSM), such as supersymmetry (SUSY). Recently, the limits obtained from these searches have been presented by the CMS collaboration in a nearly model-independent fashion – as a narrow resonance model – based on the full 8TeV dataset. In addition to publishing a 95%C.L. exclusion limit, the full likelihood information for the narrow resonance model has been released. This provides valuable information that can be incorporated into global BSM fits. We present a simple algorithm that maps an arbitrary model with multiple neutral Higgs bosons onto the narrow resonance model and derives the corresponding value for the exclusion likelihood from the CMS search. This procedure has been implemented into the public computer code HiggsBounds (version 4.2.0 and higher). We validate our implementation by cross-checking against the official CMS exclusion contours in three Higgs benchmark scenarios in the Minimal Supersymmetric Standard Model (MSSM), and find very good agreement. Going beyond validation, we discuss the combined constraints of the ττ search and the rate measurements of the SM-like Higgs at 125GeV in a recently proposed MSSM benchmark scenario, where the lightest Higgs boson obtains SM-like couplings independently of the decoupling of the heavier Higgs states. Technical details for how to access the likelihood information within HiggsBounds are given in the appendix. The program is available at http://higgsbounds.hepforge.org .

Applying exclusion likelihoods from LHC searches to extended Higgs sectors

We explore the room for possible deviations from the Standard Model (SM) Higgs boson coupling structure in a systematic study of Higgs coupling scale factor ( κ ) benchmark scenarios using the latest signal rate measurements from the Tevatron and LHC experiments. We employ χ 2 fits performed with HiggsSignals , which takes into account detailed information on signal efficiencies and major correlations of theoretical and experimental uncertainties. All considered scenarios allow for additional non-standard Higgs boson decay modes, and various assumptions for constraining the total decay width are discussed. No significant deviations from the SM Higgs boson coupling structure are found in any of the investigated benchmark scenarios. We derive upper limits on an additional (undetectable) Higgs decay mode under the assumption that the Higgs couplings to weak gauge bosons do not exceed the SM prediction. We furthermore discuss the capabilities of future facilities for probing deviations from the SM Higgs couplings, comparing the high luminosity upgrade of the LHC with a future International Linear Collider (ILC), where for the latter various energy and luminosity scenarios are considered. At the ILC model-independent measurements of the coupling structure can be performed, and we provide estimates of the precision that can be achieved.

Probing the Standard Model with Higgs signal rates from the Tevatron, the LHC and a future ILC