<p>The diphoton channel for exploring the Georgi-Machacek (GM) scenario containing scalar triplets at the Large Hadron Collider (LHC) has been identified as germane and subjected to a detailed study. The scalar spectrum of the model, which imposes a custodial SU(2) on the potential, gets classified into a 5-plet, a 3-plet, and two singlets under the custodial symmetry. While most attempts to probe or constrain the scenario at the LHC depend largely on signals of charged scalars, we point out that the custodial SU(2) singlet state <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>H</mi></mrow></math> can have a substantial branching ratio (amounting to a few percent) into two photons. We carry out a detailed simulation of the resulting signal and the standard model backgrounds, obtaining the signal significance in different regions of the parameter space using the profile likelihood ratio method. Substantial regions of the GM parameter space are thus shown to be accessible to LHC studies, both at the high-luminosity run with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∫</mo><mi mathvariant="script">L</mi><mi>d</mi><mi>t</mi><mo>=</mo><mn>3000</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> and also in Run-3 with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∫</mo><mi mathvariant="script">L</mi><mi>d</mi><mi>t</mi><mo>=</mo><mn>300</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>, even after folding in systematic errors. We have also demonstrated that a rather substantial improvement in the signal significance is achieved by switching over from a cut-based analysis to one based on a neural network.</p>

India

Satyaki Bhattacharya

Rituparna Ghosh

Biswarup Mukhopadhyaya

Diphoton signals for the Georgi-Machacek scenario at the Large Hadron Collider

The exotic decay modes of the already discovered 125-GeV scalar into a pair of light pseudoscalars are a good probe of those new physics scenarios where such pseudoscalars exist. Searches in the mass region where the pseudoscalar (A) is lighter than 62.5 GeV have yielded null findings so far. No search has yet examined <math><msub><mrow><mi>m</mi></mrow><mrow><mi>A</mi></mrow></msub><mo>&gt;</mo><mn>62.5</mn></math> GeV where the cross section is suppressed by the off-shell pseudoscalar. We point out a possible enhancement of the sensitivity of probing hAA coupling in the context of a Type-X two Higgs doublet model. We focus on <math><mi>h</mi><mo>→</mo><mi>A</mi><msup><mrow><mi>A</mi></mrow><mrow><mo>(</mo><mo>⁎</mo><mo>)</mo></mrow></msup><mo>→</mo><mn>4</mn><mi>τ</mi></math>, and select events with two same-sign τ-jets along with a pair of same-sign leptons. This enables much more effective background elimination than in the erstwhile proposed channels. Taking two values of the ττA coupling into account, we obtain limits on the hAA coupling that can be probed at 2σ and 3σ significance, for <math><msub><mrow><mi>m</mi></mrow><mrow><mi>A</mi></mrow></msub></math> ranging up to 85 GeV. For <math><msub><mrow><mi>m</mi></mrow><mrow><mi>A</mi></mrow></msub><mo>&lt;</mo><mn>62.5</mn></math> GeV, too, we find the probe through our suggested channel exhibits considerable improvement upon the usual <math><mn>2</mn><mi>μ</mi><mn>2</mn><mi>τ</mi></math>-based searches conducted at the LHC. Within this region, achieving the reach of <math><msub><mrow><mi>λ</mi></mrow><mrow><mi>h</mi><mi>A</mi><mi>A</mi></mrow></msub></math> coupling at 3000 fb$^{−1}$ luminosity using our strategy would require approximately ∼3.6<math><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>5</mn></mrow></msup></math> fb$^{−1}$ luminosity using conventional <math><mn>2</mn><mi>μ</mi><mn>2</mn><mi>τ</mi></math>-based searches.

Sirshendu Samanta

Tousik Samui

Ritesh K. Singh

Improving probes of coupling in the Type-X two Higgs doublet model scenario: The crucial role of -jet Charge Identification

The identification and isolation of two weakly interacting massive particles (WIMP) dark matter (DM) components at colliders is of wide interest on the one hand but extremely challenging on the other, especially when the dominant signal of both DM components is of the mono-<math><mi>X</mi></math> type (<math><mi>X</mi><mo>=</mo><mi>γ</mi></math>, <math><mrow><mi>Z</mi></mrow></math>, <math><mrow><mi>H</mi></mrow></math>). After emphasizing that an <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> collider is more suitable for this goal, we first identify the theoretical principles that govern the occurrence of two peaks in missing energy (<math><mi>E</mi></math>) distribution, in a double-DM scenario. We then identify a variable that rather spectacularly elicits the double-peaking behavior, namely, the plot of bin-wise statistical significance (<math><mi>S</mi><mo>/</mo><msqrt><mi>B</mi></msqrt></math>) against <math><mi>E</mi></math>. Using Gaussian fits of the histograms, we apply a set of criteria developed by us, to illustrate the above points numerically for suitable benchmarks.

Subhaditya Bhattacharya

Purusottam Ghosh

Germany

Jayita Lahiri

Mono-<math><mi>X</mi></math> signal and two component dark matter: New distinction criteria

We consider, in the context of the Large Hadron Collider, some signals of the type-X two Higgs doublet model (2HDM). The analysis takes into account all theoretical and observational constraints, and is based on the final state comprising a same-sign dilepton pair and a pair of same-sign <math><mi>τ</mi></math> jets. The crucial ingredient in making the signal clean is the same-sign feature of both the dilepton and the <math><mi>τ</mi></math>-jet pair individually. After a detailed estimate of the signal and all noteworthy backgrounds, we show that this channel offers by far the best signal significance among those studied so far, predicting discovery with an integrated luminosity of <math><mn>3000</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>, and strong indications even with <math><mn>1000</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> if systematic uncertainties do not exceed about 10%. We also demonstrate that the recently developed dynamic radius jet algorithm is effective in this connection.

Novel signals for the type-X two-Higgs-doublet scenario at the Large Hadron Collider

The study of standard QCD jets produced along with fat jets, which may appear as a result of the decay of a heavy particle, has become an essential part of collider studies. Current jet clustering algorithms, which use a fixed radius parameter for the formation of jets from the hadrons of an event, may be inadequate to capture the differing radius features. In this work, we develop an alternative jet clustering algorithm that allows the radius to vary dynamically based on local kinematics and distribution in the η-ϕ plane inside each evolving jet. We present the usefulness of this dynamic radius clustering algorithm through two Standard Model processes, and thereafter illustrate it for a scenario beyond the Standard Model at the 13 TeV LHC.

Ritesh Singh

Dynamic radius jet clustering algorithm

The Georgi-Machacek model, introducing a complex and a real scalar triplet as additional components of the electroweak symmetry breaking sector, enables substantial triplet contributions to the weak gauge boson masses, subject to the equality of the complex and the real triplet vacuum expectation values (vev) via a custodial SU(2) symmetry. We present an updated set of constraints on this scenario, from collider data (including those from <math><mrow><mn>137</mn><mo>/</mo><mn>139</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> of luminosity at the Large Hadron Collider), available data on the 125 GeV scalar, indirect limits, and also theoretical restrictions from vacuum stability and unitarity. It is found that some bounds get relaxed, and the phenomenological potential of the scenario is more diverse, if the doubly charged scalar in the spectrum can decay not only into two like-sign <math><mi>W</mi></math>’s but also into one or two singly charged scalars. Other interesting features are noticed in a general approach, such as substantial <math><mi>γ</mi><mi>γ</mi></math> and <math><mi>Z</mi><mi>γ</mi></math> branching ratios of the additional custodial singlet scalar and appreciable strength of the trilinear interaction of a charged scalar, the <math><mi>W</mi></math> and the <math><mi>Z</mi></math>. Finally, we take into account the possibility of custodial SU(2) breaking, resulting in inequality of the real and the complex scalar vevs which, too, in principle may allow large triplet contribution to weak boson masses. Illustrative numerical results on the modified limits and predictions are presented, once more taking into account all the constraints mentioned above.

Some new observations for the Georgi-Machacek scenario with triplet Higgs scalars

We investigate ways of identifying two kinds of dark matter (DM) component particles at high-energy colliders. The strategy is to notice and distinguish double-peaks(humps) in the missing energy/transverse energy distribution. The relative advantage of looking for missing energy is pointed out, in view of the fact that the longitudinal component of the momentum imbalance becomes an added input. It thus turns out that an electron-positron collider is better suited for discovering a two-component DM scenario, so long as both of the components are kinematically accessible. This and a number of associated conclusions are established, using for illustration a scenario including a scalar and a spin-1/2 particle. We also formulate a set of measurable quantities which quantify the distinguishability of the two humps, defined in terms of double-Gaussian fits to the missing energy distribution. The efficacy of these variables in various regions of the parameter space is discussed, using the aforesaid model as illustration.

Distinguishing two dark matter component particles at e + e  −  colliders

We investigate the potential of the channel mono-Higgs + missing transverse energy (MET) in yielding signals of dark matter at the high-luminosity Large Hadron Collider (LHC). As illustration, a Higgs-portal scenario has been chosen, where an extension of the Standard Model with a real scalar gauge-singlet which serves as a dark matter candidate. The phenomenological viability of this scenario has been ensured by postulating the existence of dimension-6 operators that enable cancellation in certain amplitudes for elastic scattering of dark matter in direct search experiments. These operators are found to have non-negligible contribution to the mono-Higgs signal. Thereafter, we carry out a detailed analysis of this signal, with the accompanying MET providing a useful handle in suppressing backgrounds. Signals for the Higgs decaying into both the diphoton and  $$b{\bar{b}}$$  <math> <mrow> <mi>b</mi> <mover> <mrow> <mi>b</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>   channels have been studied. A cut-based simulation is presented first, optimizing over various event selection criteria. This is followed by a demonstration of how the statistical significance can be improved through analyses based on boosted decision trees and artificial neural networks.

Debabrata Bhowmik

The mono-Higgs + MET signal at the Large Hadron Collider: a study on the  $$\gamma \gamma $$  <math> <mrow> <mi>γ</mi> <mi>γ</mi> </mrow> </math>   and  $$b\bar{b}$$  <math> <mrow> <mi>b</mi> <mover> <mrow> <mi>b</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>   final states

The field of particle physics is at the crossroads. The discovery of a Higgs-like boson completed the Standard Model (SM), but the lacking observation of convincing resonances Beyond the SM (BSM) offers no guidance for the future of particle physics. On the other hand, the motivation for New Physics has not diminished and is, in fact, reinforced by several striking anomalous results in many experiments. Here we summarise the status of the most significant anomalies, including the most recent results for the flavour anomalies, the multi-lepton anomalies at the LHC, the Higgs-like excess at around 96 GeV, and anomalies in neutrino physics, astrophysics, cosmology, and cosmic rays. While the LHC promises up to 4  $$\hbox {ab}^{-1}$$  <math> <msup> <mtext>ab</mtext> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </math>   of integrated luminosity and far-reaching physics programmes to unveil BSM physics, we consider the possibility that the latter could be tested with present data, but that systemic shortcomings of the experiments and their search strategies may preclude their discovery for several reasons, including: final states consisting in soft particles only, associated production processes, QCD-like final states, close-by SM resonances, and SUSY scenarios where no missing energy is produced. New search strategies could help to unveil the hidden BSM signatures, devised by making use of the CERN open data as a new testing ground. We discuss the CERN open data with its policies, challenges, and potential usefulness for the community. We showcase the example of the CMS collaboration, which is the only collaboration regularly releasing some of its data. We find it important to stress that individuals using public data for their own research does not imply competition with experimental efforts, but rather provides unique opportunities to give guidance for further BSM searches by the collaborations. Wide access to open data is paramount to fully exploit the LHCs potential.

United Kingdom

Oliver Fischer

South Africa

Bruce Mellado

Switzerland

Stefan Antusch

Emanuele Bagnaschi

CERN

Shankha Banerjee

Geoff Beck

Italy

Benedetta Belfatto

United States

Matthew Bellis

Zurab Berezhiani

Monika Blanke

Bernat Capdevila

Taiwan

Kingman Cheung

Andreas Crivellin

Nishita Desai

Bhupal Dev

Rohini Godbole

Tao Han

Philip Harris

Martin Hoferichter

Matthew Kirk

Austria

Suchita Kulkarni

Clemens Lange

Finland

Kati Lassila-Perini

Zhen Liu

France

Farvah Mahmoudi

Claudio Manzari

David Marzocca

Spain

Antonio Pich

Xifeng Ruan

Luc Schnell

Jesse Thaler

Susanne Westhoff

Unveiling hidden physics at the LHC

We investigate the modification of the Higgs signals from vector boson fusion at the LHC arising from higher-dimensional effective operators involving quarks, electroweak gauge bosons, and the 125 GeV scalar discovered in 2012. Taking a few of the admissible dimension-6 operators as illustration, we work within the framework of the Standard Model effective field theory (SMEFT) and identify kinematic variables that can reflect the presence of such effective operators. The useful variables turn out to be the geometric mean of the transverse momenta of the two forward jets produced in vector boson fusion and the rapidity difference between the two forward jets. We identify the shift in event population caused by the effective operators in the same, spanned by the above kinematic variables. Minimum values of the Wilson coefficients of the chosen dimension-6 operators are identified, for which they can be probed at the <math><mrow><mn>3</mn><mi>σ</mi></mrow></math> level in the high-luminosity run of the LHC at 14 TeV. Projected exclusion limits on some of the couplings, obtained from our analysis, can significantly improve the limits on such couplings derived from electroweak precision data.

Tisa Biswas

Anindya Datta

Following the trail of new physics via the vector boson fusion Higgs boson signal at the Large Hadron Collider