<p>The proposed Large Hadron electron Collider (LHeC), with a center-of-mass energy of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>≈</mo><mn>1.3</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>, provides a clean and sensitive environment to probe the top quark’s neutral current interactions with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>−</mo></msup><mi>p</mi><mo stretchy="false">→</mo><msup><mi>e</mi><mo>−</mo></msup><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math>. We investigate the precision with which the Standard Model (SM) <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover><mi>Z</mi></math> couplings—the vector and axial-vector components (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>V</mi></mrow></msub><mo>,</mo><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>A</mi></mrow></msub></math>) can be measured, along with possible new physics effects parametrized by higher-dimensional operators inducing weak electric and magnetic dipolelike interactions (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub><mo>,</mo><msub><mi>C</mi><mrow><mn>2</mn><mi>A</mi></mrow></msub></math>). Focusing on the semileptonic decay channel, where either the top quark decays leptonically to a positively charged lepton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>ℓ</mo><mo>+</mo></msup><mo>=</mo><msup><mi>e</mi><mo>+</mo></msup><mo>,</mo><msup><mi>μ</mi><mo>+</mo></msup></math>) and the antitop hadronically, or vice versa, we utilize the azimuthal angle difference <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>ϕ</mi><mrow><msup><mi>e</mi><mo>−</mo></msup><msup><mo>ℓ</mo><mo>±</mo></msup></mrow></msub></math> between the scattered electron and the charged lepton <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>ℓ</mo><mo>±</mo></msup></math> as the key observable to derive projected constraints. Using a one-parameter multibin <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>χ</mi><mn>2</mn></msup></math> analysis of the differential <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>ϕ</mi><mrow><msup><mi>e</mi><mo>−</mo></msup><msup><mo>ℓ</mo><mo>±</mo></msup></mrow></msub></math> distribution, the constraints on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>A</mi></mrow></msub></math> improve from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo stretchy="false">)</mo></math> at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>50</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>2</mn></mrow></msup><mo stretchy="false">)</mo></math> at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1000</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>, while the improvement for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>V</mi></mrow></msub></math> remains within the same order of magnitude, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo stretchy="false">)</mo></math>. These results correspond to average relative precisions of approximately 8% and 68%, respectively, with respect to their SM values. The anomalous tensor couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><mrow><mn>2</mn><mi>A</mi></mrow></msub></math> are constrained at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo stretchy="false">)</mo></math> level even at low luminosity and improve moderately with increasing luminosity. While the two-parameter analysis broadens the allowed regions due to parameter correlations, it maintains competitive sensitivity, particularly for the SM-like couplings. Throughout, we assume a systematic uncertainty of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>δ</mi><mi>s</mi></msub><mo>=</mo><mn>5</mn><mo>%</mo></math> in all analyses, and all results are quoted at the 95% confidence level. These results demonstrate the LHeC’s potential to provide complementary and competitive sensitivity to top-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> couplings compared to current and future hadron and lepton collider capabilities.</p>

South Africa

Katlego Machethe

India

Pramod Sharma

Mukesh Kumar

Brazil

Rafiqul Rahaman

Bruce Mellado

Analyzing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover><mi>Z</mi></math>-couplings at the future <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>−</mo></msup><mi>p</mi></math> collider

The Large Electron Positron collider observed an indication for a new Higgs boson with a mass around 95 GeV-100 GeV in the process <math altimg='si23.svg'><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup><mo>&#8594;</mo><msup><mi>Z</mi><mo>*</mo></msup><mo>&#8594;</mo><mi>Z</mi><mi>S</mi></mrow></math> with <math altimg='si8.svg'><mrow><mi>S</mi><mo>&#8594;</mo><mi>b</mi><mover accent='true'><mi>b</mi><mo>&#175;</mo></mover></mrow></math>. The interest in this excess re-emerged with the di-photon signature at <math altimg='si24.svg'><mo>&#8776;</mo></math> 95 GeV at the Large Hadron Collider. In fact, a combined global significance of <math altimg='si25.svg'><mrow><mn>3.4</mn><mi>&#963;</mi></mrow></math> is obtained once <math altimg='si26.svg'><mrow><mi>W</mi><mi>W</mi></mrow></math> and <math altimg='si27.svg'><mrow><mi>&#964;</mi><mi>&#964;</mi></mrow></math> signals are included in addition. In this article, we perform a feasibility study for discovering such a new scalar <math altimg='si10.svg'><mi>S</mi></math> at future electron-positron colliders using the recoil-mass method applied to <math altimg='si28.svg'><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup><mo>&#8594;</mo><mi>Z</mi><mi>S</mi></mrow></math> with <math altimg='si29.svg'><mrow><mi>Z</mi><mo>&#8594;</mo><msup><mi>&#956;</mi><mo>+</mo></msup><msup><mi>&#956;</mi><mo>&#8722;</mo></msup></mrow></math> and <math altimg='si8.svg'><mrow><mi>S</mi><mo>&#8594;</mo><mi>b</mi><mover accent='true'><mi>b</mi><mo>&#175;</mo></mover></mrow></math>. For this, we employ a Deep Neural Network to enhance the separation between the Standard Model background and the signal, reducing the required integrated luminosity necessary for discovery by a factor of two to three. As a result, an <math altimg='si11.svg'><mrow><mi>S</mi><mi>U</mi><msub><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow><mi>L</mi></msub></mrow></math> singlet Higgs with a mass of <math altimg='si24.svg'><mo>&#8776;</mo></math> 95 GeV can be observed with more than 5 <math altimg='si18.svg'><mi>&#963;</mi></math> significance at a 250 GeV centre-of-mass energy collider with <math altimg='si30.svg'><mrow><mn>5</mn><mspace width='0.33em' /><msup><mrow><mrow><mi mathvariant='normal'>a</mi></mrow><mi>b</mi></mrow><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></mrow></math> integrated luminosity if it has a mixing angle of at least 0.1 with the Standard Model Higgs, which means that a discovery can be achieved within the whole 95 % confidence-level region preferred by Large Electron Positron excess. Furthermore, including more decay channels such as <math altimg='si31.svg'><mrow><mi>S</mi><mo>&#8594;</mo><mi>&#964;</mi><mi>&#964;</mi></mrow></math> and <math altimg='si32.svg'><mrow><mi>Z</mi><mo>&#8594;</mo><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup></mrow></math> further enhances the discovery potential of future <math altimg='si33.svg'><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup></mrow></math> accelerators, like CEPC, CLIC, FCC-ee and ILC.

Anza-Tshilidzi Mulaudzi

Karabo Mosala

Thuso Mathaha

Switzerland

Andreas Crivellin

France

Maxim Titov

China

Manqi Ruan

Yaquan Fang

Discovery potential of future electron-positron colliders for a 95 GeV scalar

The anomalies observed in the <math><mi>W</mi></math> mass measurements at the CDF-II experiments and the excesses seen around 95 GeV at the Large Hadron Collider (LHC) motivate this work, in which we investigate and constrain the parameter space of the Scale Invariant Scotogenic Model with a Majorana dark matter candidate. The scanned parameters are chosen to be consistent with the dark matter relic density and the observed excesses at <math><mo>∼</mo><mn>95</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> signal strength rates in different channels. We found that significant part of the viable space addresses the excess in the channel <math><mi>γ</mi><mi>γ</mi></math>, while a tight part can address the excess in both <math><mi>γ</mi><mi>γ</mi></math> and <math><mi>b</mi><mover><mi>b</mi><mo>¯</mo></mover></math> channels. Furthermore, the model’s viable parameters can be probed in both the LHC and future <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> colliders for di-Higgs production.

United Arab Emirates

Amine Ahriche

Algeria

Mohamed Lamine Bellilet

Sudan

Mohammed Omer Khojali

Anza-Tshildzi Mulaudzi

Scale invariant scotogenic model: CDF-II <math><mi>W</mi></math>-boson mass and the 95 GeV excesses

In this work, we explore the possibilities of producing Axion-Like Particles (ALPs) in a future  $$e^-p$$  <math> <mrow> <msup> <mi>e</mi> <mo>-</mo> </msup> <mi>p</mi> </mrow> </math>   collider. Specifically, we focus on the proposed Large Hadron electron collider (LHeC), which can achieve a center-of-mass energy of  $$\sqrt{s} \approx 1.3$$  <math> <mrow> <msqrt> <mi>s</mi> </msqrt> <mo>≈</mo> <mn>1.3</mn> </mrow> </math>   TeV, enabling us to probe relatively high ALP masses with  $$m_a \lesssim 300$$  <math> <mrow> <msub> <mi>m</mi> <mi>a</mi> </msub> <mo>≲</mo> <mn>300</mn> </mrow> </math>   GeV. The production of ALPs can occur through various channels, including  $$W^+W^-$$  <math> <mrow> <msup> <mi>W</mi> <mo>+</mo> </msup> <msup> <mi>W</mi> <mo>-</mo> </msup> </mrow> </math>  ,  $$\gamma \gamma $$  <math> <mrow> <mi>γ</mi> <mi>γ</mi> </mrow> </math>  , ZZ, and  $$Z\gamma $$  <math> <mrow> <mi>Z</mi> <mi>γ</mi> </mrow> </math>  -fusion within the collider environment. To investigate this, we conduct a comprehensive analysis that involves estimating the production cross section and constraining the limits on the associated couplings of ALPs, namely  $$g_{WW}$$  <math> <msub> <mi>g</mi> <mrow> <mi>WW</mi> </mrow> </msub> </math>  ,  $$g_{\gamma \gamma }$$  <math> <msub> <mi>g</mi> <mrow> <mi>γ</mi> <mi>γ</mi> </mrow> </msub> </math>  ,  $$g_{ZZ}$$  <math> <msub> <mi>g</mi> <mrow> <mi>ZZ</mi> </mrow> </msub> </math>  , and  $$g_{Z\gamma }$$  <math> <msub> <mi>g</mi> <mrow> <mi>Z</mi> <mi>γ</mi> </mrow> </msub> </math>  . To achieve this, we utilize a multiple-bin  $$\chi ^2$$  <math> <msup> <mi>χ</mi> <mn>2</mn> </msup> </math>   analysis on sensitive differential distributions. Through the analysis of these distributions, we determine upper bounds on the associated couplings within the mass range of 5 GeV  $$\le m_a \le $$  <math> <mrow> <mo>≤</mo> <msub> <mi>m</mi> <mi>a</mi> </msub> <mo>≤</mo> </mrow> </math>   300 GeV. The obtained upper bounds are of the order of  $$\mathcal{O}(10^{-1})$$  <math> <mrow> <mi>O</mi> <mo>(</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mo>)</mo> </mrow> </math>   for  $$g_{\gamma \gamma }$$  <math> <msub> <mi>g</mi> <mrow> <mi>γ</mi> <mi>γ</mi> </mrow> </msub> </math>   ( $$g_{WW}$$  <math> <msub> <mi>g</mi> <mrow> <mi>WW</mi> </mrow> </msub> </math>  ,  $$g_{ZZ}$$  <math> <msub> <mi>g</mi> <mrow> <mi>ZZ</mi> </mrow> </msub> </math>  ,  $$g_{Z\gamma }$$  <math> <msub> <mi>g</mi> <mrow> <mi>Z</mi> <mi>γ</mi> </mrow> </msub> </math>  ) in  $$m_a \in $$  <math> <mrow> <msub> <mi>m</mi> <mi>a</mi> </msub> <mo>∈</mo> </mrow> </math>   [5, 200 (300)] GeV considering an integrated luminosity of 1 ab $$^{-1}$$  <math> <msup> <mrow></mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </math>  . Furthermore, we compare the results of our study with those obtained from other available experiments. We emphasize the limits obtained through our analysis and showcase the potential of the LHeC in probing the properties of ALPs.

Ashok Goyal

Axion-like particles at future  $$e^- p$$  <math> <mrow> <msup> <mi>e</mi> <mo>-</mo> </msup> <mi>p</mi> </mrow> </math>   collider

In the last decades, the Standard Model (SM) of particle physics has been extensively tested and confirmed, with the announced discovery of the Higgs boson in 2012 being the last missing puzzle piece. Even though since then the search for new particles and interactions has been further intensified, the experiments ATLAS and CMS at the Large Hadron Collider (LHC) at CERN did not find evidence for the direct production of a new state. However, in recent years, deviations between LHC data and SM predictions in multiple observables involving two or more leptons (electrons or muons) have emerged, the so-called “multilepton anomalies,” pointing towards the existence of a beyond the SM Higgs boson <math><mi>S</mi></math>. While from these measurements its mass cannot be exactly determined, it is estimated to lay in the range between 130 and 160 GeV. Motivated by this observation, we perform a search for signatures of <math><mi>S</mi></math>, by using existing CMS and ATLAS analyses. Combining channels involving the associate productions of SM gauge bosons (<math><mi>γ</mi><mi>γ</mi></math> and <math><mi>Z</mi><mi>γ</mi></math>), we find that a simplified model with a new scalar with <math><msub><mi>m</mi><mi>S</mi></msub><mo>=</mo><mn>151.5</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> is preferred over the SM hypothesis by <math><mrow><mn>4.3</mn><mi>σ</mi></mrow></math> (<math><mrow><mn>3.9</mn><mi>σ</mi></mrow></math>) locally (globally). On the face of it, this provides a good indication for the existence of a new scalar resonance <math><mi>S</mi></math> decaying into photons, in association with missing energy, and allows for a connection to the long-standing problem of dark matter. Furthermore, because <math><mi>S</mi></math> is always produced together with other particles, we postulate the existence of a second new (heavier) Higgs boson <math><mi>H</mi></math> that decays into <math><mi>S</mi></math> and propose novel searches to discover this particle, which can be performed by ATLAS and CMS.

CERN

United Kingdom

Oliver Fischer

Srimoy Bhattacharya

Elias Malwa

Ntsoko Rapheeha

Xifeng Ruan

Qiyu Sha

Accumulating evidence for the associated production of a new Higgs boson at the LHC

The proposed future Large Hadron electron collider provides sufficient center of mass energies,     $$\sqrt{s}$$  <math> <msqrt> <mi>s</mi> </msqrt> </math>  , to probe heavy particles decaying into     $$W^\pm (Z)-$$  <math> <mrow> <msup> <mi>W</mi> <mo>±</mo> </msup> <mrow> <mo>(</mo> <mi>Z</mi> <mo>)</mo> </mrow> <mo>-</mo> </mrow> </math>  boson of mass     $$&gt;2m_W$$  <math> <mrow> <mo>&gt;</mo> <mn>2</mn> <msub> <mi>m</mi> <mi>W</mi> </msub> </mrow> </math>       $$(2m_Z)$$  <math> <mrow> <mo>(</mo> <mn>2</mn> <msub> <mi>m</mi> <mi>Z</mi> </msub> <mo>)</mo> </mrow> </math>  . In this work we present a study to produce one such heavy CP even scalar H of mass     $$2m_h&lt; m_H &lt; 2 m_t$$  <math> <mrow> <mn>2</mn> <msub> <mi>m</mi> <mi>h</mi> </msub> <mo>&lt;</mo> <msub> <mi>m</mi> <mi>H</mi> </msub> <mo>&lt;</mo> <mn>2</mn> <msub> <mi>m</mi> <mi>t</mi> </msub> </mrow> </math>   through charged-current production mode where     $$H \rightarrow W^+W^-$$  <math> <mrow> <mi>H</mi> <mo>→</mo> <msup> <mi>W</mi> <mo>+</mo> </msup> <msup> <mi>W</mi> <mo>-</mo> </msup> </mrow> </math>  , where hadronic decay of     $$W^\pm -$$  <math> <mrow> <msup> <mi>W</mi> <mo>±</mo> </msup> <mo>-</mo> </mrow> </math>  boson is considered to reconstruct     $$m_H$$  <math> <msub> <mi>m</mi> <mi>H</mi> </msub> </math>  . Due to the presence of missing energy and forward jet in this channel, it is challenging to reconstruct     $$m_H$$  <math> <msub> <mi>m</mi> <mi>H</mi> </msub> </math>   with above final state and thus we employed three different reconstruction methods and discuss the significance of each one. For this analysis we consider a benchmark value of     $$m_H = 270$$  <math> <mrow> <msub> <mi>m</mi> <mi>H</mi> </msub> <mo>=</mo> <mn>270</mn> </mrow> </math>   GeV and     $$\sqrt{s} \approx 1.3$$  <math> <mrow> <msqrt> <mi>s</mi> </msqrt> <mo>≈</mo> <mn>1.3</mn> </mrow> </math>   TeV with an assumed luminosity of 1 ab    $$^{-1}$$  <math> <msup> <mrow></mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </math>  .

Feasibility of the observation of a heavy scalar through the fully hadronic final state at the LHeC

The interaction between the dark     $$U(1)_d$$  <math> <mrow> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>d</mi> </msub> </mrow> </math>   sector with the visible Standard Model (SM) sector takes place through the kinetic mixing between the dark photon     $$U(1)_d$$  <math> <mrow> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>d</mi> </msub> </mrow> </math>   field     $$Z_d^\mu $$  <math> <msubsup> <mi>Z</mi> <mi>d</mi> <mi>μ</mi> </msubsup> </math>   and the SM     $$U(1)_Y$$  <math> <mrow> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>Y</mi> </msub> </mrow> </math>   gauge field     $$B_\mu $$  <math> <msub> <mi>B</mi> <mi>μ</mi> </msub> </math>  . After the electroweak and     $$U(1)_d$$  <math> <mrow> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>d</mi> </msub> </mrow> </math>   symmetry breaking, the dark photon     $$Z_d^\mu $$  <math> <msubsup> <mi>Z</mi> <mi>d</mi> <mi>μ</mi> </msubsup> </math>   acquires a mass and mixes with the SM neutral vector boson     $$Z_\mu $$  <math> <msub> <mi>Z</mi> <mi>μ</mi> </msub> </math>  . This mixing leads to parity-violating coupling between the     $$Z_d^\mu $$  <math> <msubsup> <mi>Z</mi> <mi>d</mi> <mi>μ</mi> </msubsup> </math>   and SM. The coupling between the dark photon and SM can be explored in low energy phenomenology as well as in collider experiments. The Lorentz structure of dark photon interaction with SM fermions is explored in the proposed high energy future Large Hadron-electron collider, which would provide efficient energy and a clean environment using cross-section and asymmetries associated with polarisation observable of the dark photon in leptons decay. A     $$\chi ^2$$  <math> <msup> <mi>χ</mi> <mn>2</mn> </msup> </math>  -analysis is performed to compare the strength of various variables for both the charge- and neutral-current processes. Based on this analysis,     $$90\%$$  <math> <mrow> <mn>90</mn> <mo>%</mo> </mrow> </math>   confidence level (C.L.) contours in the     $$\varepsilon $$  <math> <mi>ε</mi> </math>  -    $$m_{Z_d}$$  <math> <msub> <mi>m</mi> <msub> <mi>Z</mi> <mi>d</mi> </msub> </msub> </math>   and     $$\varepsilon $$  <math> <mi>ε</mi> </math>  -    $$g_V$$  <math> <msub> <mi>g</mi> <mi>V</mi> </msub> </math>   plane are obtained to put limits on the     $$Z_d^\mu $$  <math> <msubsup> <mi>Z</mi> <mi>d</mi> <mi>μ</mi> </msubsup> </math>   mass up to 100 GeV, coupling strength     $$\varepsilon $$  <math> <mi>ε</mi> </math>   and on the Lorentz structure of dark photon coupling with the SM fermions (    $$g_V$$  <math> <msub> <mi>g</mi> <mi>V</mi> </msub> </math>  ) at     $$\sqrt{s} \approx 1.3$$  <math> <mrow> <msqrt> <mi>s</mi> </msqrt> <mo>≈</mo> <mn>1.3</mn> </mrow> </math>   TeV.

Satendra Kumar

Exploring dark     $$Z_d$$  <math> <msub> <mi>Z</mi> <mi>d</mi> </msub> </math>  -boson in future large hadron-electron collider

In this paper we consider a spin- $$\frac{3}{2}$$  <math> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> </math>   dark matter (DM) particle which couples to neutrinos, as a viable candidate to produce the observed DM relic density through the thermal freeze-out mechanism. The couplings of DM to neutrinos is considered first in a general dimension-6 effective field theory framework. We then consider two specific neutrino-portal models discussed in the literature. In the first model DM couples to the standard model neutrinos through mixing generated by a sterile pseudo-Dirac massive neutrino, and in the second model we consider the  $$U(1)_{L_\mu - L_\tau }$$  <math> <mrow> <mi>U</mi> <msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mrow> <msub> <mi>L</mi> <mi>μ</mi> </msub> <mo>-</mo> <msub> <mi>L</mi> <mi>τ</mi> </msub> </mrow> </msub> </mrow> </math>   gauge symmetric model. For each of these models we explore the parameter space required to generate the observed relic density. The constraints on the parameters of these models from the existing and proposed neutrino experiments, as well as from existing cosmological and astrophysical bounds, are considered in the context of the relic density calculations.

Mohammed Khojali

Alan Cornell

Neutrino specific spin-3/2 dark matter

The proposed future  $$e^- p$$  <math> <mrow> <msup> <mi>e</mi> <mo>-</mo> </msup> <mi>p</mi> </mrow> </math>   collider provides sufficient energies to produce the Standard Model Higgs Boson (h) through  $$W^\pm $$  <math> <msup> <mi>W</mi> <mo>±</mo> </msup> </math>   and Z-Boson fusion in charged and neutral current modes, respectively and to measure its properties. We take this opportunity to investigate the prospect of measuring the CP properties of h through  $$h \rightarrow \tau ^{+} \tau ^{-}$$  <math> <mrow> <mi>h</mi> <mo>→</mo> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msup> <mi>τ</mi> <mo>-</mo> </msup> </mrow> </math>  , where  $$\tau ^{-}\,\left( \tau ^{+}\right) $$  <math> <mrow> <msup> <mi>τ</mi> <mo>-</mo> </msup> <mspace width="0.166667em"></mspace> <mfenced> <msup> <mi>τ</mi> <mo>+</mo> </msup> </mfenced> </mrow> </math>   decays to a charged pion  $$\pi ^-\,\left( \pi ^+\right) $$  <math> <mrow> <msup> <mi>π</mi> <mo>-</mo> </msup> <mspace width="0.166667em"></mspace> <mfenced> <msup> <mi>π</mi> <mo>+</mo> </msup> </mfenced> </mrow> </math>   and a neutral pion  $$\pi ^0$$  <math> <msup> <mi>π</mi> <mn>0</mn> </msup> </math>   in association with neutrino (anti-neutrino). An interesting CP sensitive angular observable  $$\alpha _{\mathrm{CP}}$$  <math> <msub> <mi>α</mi> <mi>CP</mi> </msub> </math>   between the two  $$\tau $$  <math> <mi>τ</mi> </math>  -leptons decay plane in the  $$\pi ^+\pi ^-$$  <math> <mrow> <msup> <mi>π</mi> <mo>+</mo> </msup> <msup> <mi>π</mi> <mo>-</mo> </msup> </mrow> </math>   centre of mass frame is proposed and investigated in this work. For fixed electron energy of 150 GeV along with 7 (50) TeV of proton energy, the CP phase can be measured approximately to  $$25^\circ $$  <math> <msup> <mn>25</mn> <mo>∘</mo> </msup> </math>   ( $$14^\circ $$  <math> <msup> <mn>14</mn> <mo>∘</mo> </msup> </math>  ) at integrated luminosity of 1 ab $$^{-1}$$  <math> <msup> <mrow></mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </math>   for −80% polarised electron at 95% confidence level.

Sukanta Dutta

Abhaya Swain

Measuring CP nature of  $$h\tau {{\bar{\tau }}}$$  <math> <mrow> <mi>h</mi> <mi>τ</mi> <mover> <mrow> <mi>τ</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>   coupling at  $$e^-p$$  <math> <mrow> <msup> <mi>e</mi> <mo>-</mo> </msup> <mi>p</mi> </mrow> </math>   collider

Anomalies in multi-lepton final states at the Large Hadron Collider (LHC) have been reported in Refs. (von Buddenbrock et al., J Phys G 45(11):115003,  arXiv:1711.07874   [hep-ph], 2018; Buddenbrock et al., JHEP 1910:157,  arXiv:1901.05300   [hep-ph], 2019). These can be interpreted in terms of the production of a heavy boson, H, decaying into a standard model (SM) Higgs boson, h, and a singlet scalar, S, which is treated as a SM Higgs-like boson. This process would naturally affect the measurement of the Wh signal strength at the LHC, where h is produced in association with leptons and di-jets. Here, h would be produced with lower transverse momentum,  $$p_{Th}$$  <math> <msub> <mi>p</mi> <mrow> <mi>Th</mi> </mrow> </msub> </math>  , compared to SM processes. Corners of the phase-space are fixed according to the model parameters derived in Refs. (von Buddenbrock et al., J Phys G 45(11):115003,  arXiv:1711.07874   [hep-ph], 2018; von Buddenbrock et al., Eur Phys J C 76(10):580,  arXiv:1606.01674   [hep-ph], 2016) without additional tuning, thus nullifying potential look-else-where effects or selection biases. Provided that no stringent requirements are made on  $$p_{Th}$$  <math> <msub> <mi>p</mi> <mrow> <mi>Th</mi> </mrow> </msub> </math>   or related observables, the signal strength of Wh is  $$\mu (Wh)=2.41 \pm 0.37$$  <math> <mrow> <mi>μ</mi> <mo>(</mo> <mi>W</mi> <mi>h</mi> <mo>)</mo> <mo>=</mo> <mn>2.41</mn> <mo>±</mo> <mn>0.37</mn> </mrow> </math>  . This corresponds to a deviation from the SM of  $$3.8\sigma $$  <math> <mrow> <mn>3.8</mn> <mi>σ</mi> </mrow> </math>  . This result further strengthens the need to measure with precision the SM Higgs boson couplings in  $$e^+e^-$$  <math> <mrow> <msup> <mi>e</mi> <mo>+</mo> </msup> <msup> <mi>e</mi> <mo>-</mo> </msup> </mrow> </math>  , and  $$e^-p$$  <math> <mrow> <msup> <mi>e</mi> <mo>-</mo> </msup> <mi>p</mi> </mrow> </math>   collisions, in addition to pp collisions.

Yesenia Hernandez

Salah-Eddine Dahbi

Benjamin Lieberman

Kgomotso Monnakgotla

Shuiting Xin

The anomalous production of multi-leptons and its impact on the measurement of Wh production at the LHC