We investigate the potential of future tau neutrino experiments for identifying the <math><mrow><msub><mrow><mi>ν</mi></mrow><mrow><mi>τ</mi></mrow></msub></mrow></math> appearance in probing secret neutrino interactions, which is very important in a variety of fields, such as neutrino physics, dark matter physics, grand unified theories, astrophysics, and cosmology. The reference experiments include the DUNE far detector utilizing the atmospheric data, which is for the first time probing secret interactions, the Forward Liquid Argon Experiment (FLArE100) detector at the Forward Physics Facility, and emulsion detector experiments such as SND@LHC, <math><mi>FASER</mi><mi>ν</mi></math>, AdvSND, <math><mrow><mi>FASER</mi><mi>ν</mi><mn>2</mn></mrow></math>, and SND@SHiP. For concreteness, we consider a reference scenario in which the hidden interactions among the neutrinos are mediated by a single light gauge boson <math><msup><mi>Z</mi><mo>′</mo></msup></math> with a mass at most below the sub-GeV scale and an interaction strength <math><msub><mi>g</mi><mrow><mi>α</mi><mi>β</mi></mrow></msub></math> between the active neutrinos <math><msub><mi>ν</mi><mi>α</mi></msub></math> and <math><msub><mi>ν</mi><mi>β</mi></msub></math>. We confirm that these experiments have the capability to significantly enhance the current sensitivities on <math><msub><mi>g</mi><mrow><mi>α</mi><mi>β</mi></mrow></msub></math> for <math><msub><mi>m</mi><msup><mi>Z</mi><mo>′</mo></msup></msub><mo>≲</mo><mn>500</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> due to the production of high-energy neutrinos and excellent ability to detect tau neutrinos. Our analysis highlights the crucial role of “downward-going” DUNE atmospheric data in the search for secret neutrino interactions because of the rejection of backgrounds dominated in the upward-going events. Specifically, ten years of DUNE atmospheric data can provide the best sensitivities on <math><msub><mi>g</mi><mrow><mi>e</mi><mi>τ</mi></mrow></msub></math> and <math><msub><mi>g</mi><mrow><mi>μ</mi><mi>τ</mi></mrow></msub></math> which are about 2 orders of magnitude improvement. In addition, the beam-based experiments such as FLArE100 and <math><mrow><mi>FASER</mi><mi>ν</mi><mn>2</mn></mrow></math> can improve the current constraint on <math><msub><mi>g</mi><mrow><mi>e</mi><mi>τ</mi></mrow></msub></math> and <math><msub><mi>g</mi><mrow><mi>μ</mi><mi>τ</mi></mrow></msub></math> by more than an order of magnitude after the full running of the high luminosity LHC with the integrated luminosity of <math><mrow><mn>3</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>ab</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. For <math><msub><mi>g</mi><mrow><mi>e</mi><mi>μ</mi></mrow></msub></math> and <math><msub><mi>g</mi><mrow><mi>e</mi><mi>e</mi></mrow></msub></math> the SHiP experiment can play the most important role in the high-energy region of <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo>&gt;</mo><mi>few</mi><mtext> </mtext><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math>, and FLArE100 and <math><mrow><mi>FASER</mi><mi>ν</mi><mn>2</mn></mrow></math> can set the most stringent constraints for <math><msub><mi>m</mi><msup><mi>Z</mi><mo>′</mo></msup></msub></math> less than few keV, in particular, if atmospheric flux uncertainty reduces DUNE sensitivity. Although our analysis is proceeded under our reference scenario of secret <math><msup><mi>Z</mi><mo>′</mo></msup></math>, our analysis strategies can be readily applicable to other types of secret interactions such as Majoron models.

South Korea

Pouya Bakhti

Meshkat Rajaee

Seodong Shin

Uncovering secret neutrino interactions at tau neutrino experiments

We investigate the sensitivities of the liquid scintillator counter (LSC) at Yemilab and JUNO to solar neutrino oscillation parameters, focusing on <math><msub><mi>θ</mi><mn>12</mn></msub></math> and <math><mrow><mi>Δ</mi><msubsup><mrow><mi>m</mi></mrow><mrow><mn>21</mn></mrow><mrow><mn>2</mn></mrow></msubsup></mrow></math>. We compare the potential of JUNO with LSC at Yemilab utilizing both reactor and solar data in determining those parameters. We find that the solar neutrino data of LSC at Yemilab is highly sensitive to <math><msub><mi>θ</mi><mn>12</mn></msub></math> enabling its determination with a higher precision compared to reactor experiments. Our study also reveals that if <math><mi>Δ</mi><msubsup><mi>m</mi><mn>21</mn><mn>2</mn></msubsup></math> is larger, with a value close to the best-fit value of KamLAND, JUNO reactor data will have about two times better precision than the reactor LSC at Yemilab. On the other hand, if <math><mi>Δ</mi><msubsup><mi>m</mi><mn>21</mn><mn>2</mn></msubsup></math> is smaller and closer to the best-fit value of solar neutrino experiments, the precision of the reactor LSC at Yemilab will be better than JUNO.

United States

Seon-Hee Seo

Exploring solar neutrino oscillation parameters with the liquid scintillator counter at Yemilab with a comparison to JUNO

We conduct a combined analysis to investigate dark matter (DM) with hypercharge anapole moments, focusing on scenarios where Majorana DM particles with spin <math><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math>, 1, <math><mrow><mn>3</mn><mo>/</mo><mn>2</mn></mrow></math>, and 2 interact exclusively with Standard Model particles through <math><mrow><msub><mrow><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mi>Y</mi></msub></mrow></math> hypercharge anapole terms for the first time. For completeness, we construct general effective U(1) gauge-invariant three-point vertices. These enable the generation of hypercharge gauge-invariant interaction vertices for both a virtual photon <math><mi>γ</mi></math> and a virtual <math><mi>Z</mi></math> boson with two identical massive Majorana particles of any nonzero spin <math><mi>s</mi></math>, after the spontaneous breaking of electroweak gauge symmetry. For complementarity, we adopt effective operators tailored to each dark matter spin allowing crossing symmetry. We calculate the relic abundance, analyze current constraints and future sensitivities from dark matter direct detection and collider experiments, and apply the conceptual naive perturbativity bound. Our estimations based on a generalized vertex calculation demonstrate that the scenario with a higher-spin DM is more stringently constrained than a lower-spin DM, primarily due to the reduced annihilation cross section and/or the enhanced rate of LHC monojet events. As a remarkable outcome, the spin-2 anapole DM scenario is almost entirely excluded, while the high-luminosity LHC exhibits high sensitivities in probing spin-1 and -<math><mrow><mn>3</mn><mo>/</mo><mn>2</mn></mrow></math> scenarios, except for a tiny parameter range of DM mass around 1 TeV. A significant portion of the remaining parameter space in the spin-<math><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> DM scenario can be explored through upcoming Xenon experiments, with more than 20 ton-yr exposure equivalent to approximately 5 years of running the XENONnT experiment.

Seong Youl Choi

Jaehoon Jeong

Dong Woo Kang

Hunting for hypercharge anapole dark matter in all spin scenarios

In this work, we obtain the current limits on the pair production of vectorlike leptons decaying to a Standard Model gauge boson and a lepton in the second generation using the Run-2 data at the LHC. Since there is no dedicated search out of Run-2 data, we recast the ATLAS analyses searching for the type-III seesaw heavy leptons in the multi-lepton channels. There is no limit for the SU(2) L  singlet vectorlike lepton beyond about 100 GeV, while the limit is about 780 GeV for the doublet one. Thus, dedicated searches for the vectorlike leptons are necessary, especially for the singlet one. We also study the general cases of the vectorlike lepton decays and future sensitivities at the HL-LHC.

Junichiro Kawamura

Current status on pair-produced muon-philic vectorlike leptons in multilepton channels at the LHC

We propose a novel experimental scheme, called DAMSA (Dump-produced Aboriginal Matter Searches at an Accelerator), for searching for dark-sector particles, using rare nuclear isotope accelerator facilities that provide high-flux proton beams to produce a large number of rare nuclear isotopes. The high-intensity nature of their beams enables the investigation of dark-sector particles, including axionlike particles (ALPs) and dark photons. By contrast, their typical beam energies are not large enough to produce the backgrounds such as neutrinos resulting from secondary charged particles. The detector of DAMSA is then placed immediate downstream of the proton beam dump to maximize the prompt decay signals of dark-sector particles, which are often challenging to probe in other beam-dump-type experiments featuring a longer baseline, at the expense of an enormous amount of the beam-related neutron background. We demonstrate that beam-related neutrons can be significantly suppressed if the signal accompanies multiple, correlated visible particles in the final state. We show that the close proximity of the detector to the ALP production dump makes it possible to probe a high-mass region of ALP parameter space that the existing experiments have never explored.

Wooyoung Jang

Doojin Kim

Kyoungchul Kong

Youngjoon Kwon

Jong-Chul Park

Min Sang Ryu

Richard G. Van de Water

Un-Ki Yang

Jaehoon Yu

Search prospects for axionlike particles at rare nuclear isotope accelerator facilities

We show the prospects of probing neutral-current nonstandard interaction (NSI) in the propagation of atmospheric neutrinos in future large-volume neutrino experiments including DUNE, HK, KNO, and ORCA. For DUNE, we utilize its ability of identifying the tau neutrino event and combine the <math><msub><mi>ν</mi><mi>τ</mi></msub></math> appearance with the <math><msub><mi>ν</mi><mi>μ</mi></msub></math> disappearance. Based on our simulated results, the 10 years of data taking of the atmospheric neutrinos can enormously improve the bounds on the NSI parameters <math><msub><mi>ϵ</mi><mrow><mi>μ</mi><mi>τ</mi></mrow></msub><mo>,</mo><mo>|</mo><msub><mi>ϵ</mi><mrow><mi>μ</mi><mi>μ</mi></mrow></msub><mo>−</mo><msub><mi>ϵ</mi><mrow><mi>τ</mi><mi>τ</mi></mrow></msub><mo>|</mo></math>, <math><msub><mi>ϵ</mi><mrow><mi>e</mi><mi>μ</mi></mrow></msub></math>, <math><msub><mi>ϵ</mi><mrow><mi>e</mi><mi>τ</mi></mrow></msub></math> and <math><mo>|</mo><msub><mi>ϵ</mi><mrow><mi>μ</mi><mi>μ</mi></mrow></msub><mo>−</mo><msub><mi>ϵ</mi><mrow><mi>e</mi><mi>e</mi></mrow></msub><mo>|</mo></math> by a couple of orders of magnitudes. In addition, we show the expected correlations between the <math><mrow><mi>C</mi><mi>P</mi></mrow></math>-violation phase <math><msub><mi>δ</mi><mrow><mi>C</mi><mi>P</mi></mrow></msub></math> and the NSI parameters <math><msub><mi>ϵ</mi><mrow><mi>e</mi><mi>μ</mi></mrow></msub><mo>,</mo><msub><mi>ϵ</mi><mrow><mi>e</mi><mi>τ</mi></mrow></msub></math>, and <math><mo>|</mo><msub><mi>ϵ</mi><mrow><mi>e</mi><mi>e</mi></mrow></msub><mo>−</mo><msub><mi>ϵ</mi><mrow><mi>μ</mi><mi>μ</mi></mrow></msub><mo>|</mo></math> and confirm the potentials of DUNE, HK, KNO (combined with HK) in excluding the “No <math><mrow><mi>C</mi><mi>P</mi></mrow></math> violation” hypothesis at <math><mrow><mn>1</mn><mi>σ</mi></mrow></math>, <math><mrow><mn>2</mn><mi>σ</mi></mrow></math>, and <math><mrow><mn>3</mn><mi>σ</mi></mrow></math>, respectively.

Nonstandard interaction of atmospheric neutrino in future experiments

We demonstrate the potential of fully leptonic cascade decays of a heavy neutral Higgs boson through vectorlike leptons as a simultaneous probe for extended Higgs sectors and extra matter particles at the LHC. The processes we explore are unique in that their event topologies lead to di-boson-like leptonic final states with a lepton pair which does not reconstruct the mass of a gauge boson. By recasting existing   <math> <mn>2</mn> <mi>ℓ</mi> <mo>+</mo> <msubsup> <mi>E</mi> <mi>R</mi> <mtext>miss</mtext> </msubsup> </math>  $$ 2\ell +{E}_R^{\textrm{miss}} $$  and 3/4ℓ searches channels using run2 data from the LHC we obtain model independent bounds on the masses of heavy scalars and vectorlike leptons and use these results to explore future prospects at the HL-LHC. Our results can be directly applied to any kind of new physics scenarios sharing the final states and the event topology. For concreteness, we apply our results to a benchmark scenario: a two Higgs doublet model type-II augmented with vectorlike leptons. Remarkably, even with current data the sensitivity of our analysis shows a reach for masses of a heavy neutral Higgs and vectorlike leptons up to 2 TeV and 1.5 TeV, respectively. Even for low tan β ≳ 1, the analysis retains sensitivity to heavy Higgs masses slightly above 1 TeV. The future sensitivities at the HL-LHC extend the reach for heavy Higgses and new leptons to 2.7 TeV and 2 TeV, respectively.

Radovan Dermisek

Enrico Lunghi

Canada

Navin McGinnis

Leptonic cascade decays of a heavy Higgs boson through vectorlike leptons at the LHC

The sensitivity to dark matter signals at neutrino experiments is fundamentally challenged by the neutrino rates, as they leave similar signatures in their detectors. As a way to improve the signal sensitivity, we investigate a dark matter search strategy which utilizes the timing and energy spectra to discriminate dark matter from neutrino signals at low-energy, pulsed-beam neutrino experiments. This strategy was proposed in our companion paper Phys. Rev. Lett. 124 (2020) 121802 [1], which we apply to potential searches at COHERENT, JSNS2, and CCM. These experiments are not only sources of neutrinos but also high intensity sources of photons. The dark matter candidate of interest comes from the relatively prompt decay of a dark sector gauge boson which may replace a Standard-Model photon, so the delayed neutrino events can be suppressed by keeping prompt events only. Furthermore, prompt neutrino events can be rejected by a cut in recoil energy spectra, as their incoming energy is relatively small and bounded from above while dark matter may deposit a sizable energy beyond it. We apply the search strategy of imposing a combination of energy and timing cuts to the existing CsI and LAr data of the COHERENT experiment as concrete examples, and report a mild excess beyond known backgrounds. We then investigate the expected sensitivity reaches to dark matter signals in our benchmark experiments.

Bhaskar Dutta

Shu Liao

Louis Strigari

Adrian Thompson

Searching for dark matter signals in timing spectra at neutrino experiments

We study 4b + 2τ and 4b + 1τ signatures of heavy neutral and charged Higgs bosons originating from cascade decays of pair-produced new quarks. Decays of vectorlike quarks through heavy Higgses can easily dominate in the two Higgs doublet model of type-II, and the studied signatures are common to many possible decay chains. We design search strategies for these final states and discuss the mass ranges of heavy Higgs bosons and new quarks that can be explored at the Large Hadron Collider as functions of branching ratios in a model independent way. We further combine the results with a similar study focusing on decays which lead to a 6b final state and interpret the sensitivity to charged and neutral Higgs bosons and vectorlike quarks in the type-II two Higgs doublet model. We find that the LHC reach for their masses extends to well above 2 TeV in the case of an SU(2) doublet quark and to at least 1.8 TeV for a bottom-like SU(2) singlet quark in the whole range of tan β between 1 and 50.

Tau-jet signatures of vectorlike quark decays to heavy charged and neutral Higgs bosons

The dark matter interpretation for a recent observation of excessive electron recoil events at the XENON1T detector seems challenging because its velocity is not large enough to give rise to recoiling electrons of   <math> <mi>O</mi> <mfenced> <mi>keV</mi> </mfenced> </math>  $$ \mathcal{O}\left(\mathrm{keV}\right) $$ . Fast-moving or boosted dark matter scenarios are receiving attention as a remedy for this issue, rendering the dark matter interpretation a possibility to explain the anomaly. We investigate various scenarios where such dark matter of spin 0 and 1/2 interacts with electrons via an exchange of vector, axial-vector, pseudo-scalar, or scalar mediators. We find parameter values not only to reproduce the excess but to be consistent with existing bounds. Our study suggests that the scales of mass and coupling parameters preferred by the excess can be mostly affected by the type of mediator, and that significantly boosted dark matter can explain the excess depending on the mediator type and its mass choice. The method proposed in this work is general, and hence readily applicable to the interpretation of observed data in the dark matter direct detection experiment.

Saudi Arabia

Haider Alhazmi

Gopolang Mohlabeng

Implications of the XENON1T excess on the dark matter interpretation