We systematically investigate tests of the parity <math><mi>P</mi></math> and the combined parity and charge-conjugate <math><mi>C</mi><mi>P</mi></math> symmetries from differential angular distributions of <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> decaying into the lowest-lying baryon pairs at BESIII and the next-generation super tau-charm facilities (STCFs). Large corrections from <math><mi>Z</mi></math> and <math><mi>W</mi></math> exchange induced parity-violating effects are found for <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> decays with large logarithms resummed up to <math><mi>O</mi><mo>(</mo><msub><mi>α</mi><mi>s</mi></msub><mo>)</mo></math>. The parity-violating asymmetries on the production and the decay sides of <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> are both estimated to be of <math><mi>O</mi><mo>(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo>)</mo></math>, thus barely observable with the 10 billion <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> events currently collected at BESIII. Nevertheless, these asymmetries utilizing the current BESIII data already permit a measurement of the weak mixing angle with an absolute uncertainty <math><mi>δ</mi><msubsup><mi>s</mi><mi>w</mi><mn>2</mn></msubsup><mo>≈</mo><mn>0.09</mn></math>, corresponding to the first determination of <math><msubsup><mi>s</mi><mi>w</mi><mn>2</mn></msubsup></math> at the <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> threshold. In the future, STCFs are estimated to improve this bound by a factor of <math><mo>∼</mo><mn>20</mn></math> to <math><mi>δ</mi><msubsup><mi>s</mi><mi>w</mi><mn>2</mn></msubsup><mo>≈</mo><mn>0.005</mn></math> within one year based on luminosity rescaling. We also obtain the 95% confidence level upper bounds on the electric dipole moments of the octet baryons, which are of <math><mrow><mi>O</mi><mo>(</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>18</mn></mrow></msup><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>e</mi><mtext> </mtext><mi>cm</mi></mrow></math> for BESIII and <math><mrow><mi>O</mi><mo>(</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>19</mn></mrow></msup><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>e</mi><mtext> </mtext><mi>cm</mi></mrow></math> for STCFs. These bounds are improved by 2 to 3 orders of magnitude in comparison with the only existing one on <math><mi>Λ</mi></math> from Fermilab. The method discussed in this work also paves a way for a first and direct measurement of the <math><mi>Ξ</mi></math> and <math><mi>Σ</mi></math> electric dipole moments.

China

Yong Du

Xiao-Gang He

Jian-Ping Ma

Xin-Yu Du

Fundamental tests of <math><mi>P</mi></math> and <math><mi>C</mi><mi>P</mi></math> symmetries using octet baryons at the <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> threshold

We perform a global fit to the electroweak vertices and four-fermion operators of the standard model effective field theory in this work using <math><msub><mi>N</mi><mi>eff</mi></msub></math> from cosmological probes, as well as datasets from colliders and low-energy experiments. We find <math><msub><mi>N</mi><mi>eff</mi></msub></math>, both its current measurement and future projections, can only marginally improve the fit in both the flavor universal and the most general flavor scenarios. The resulting <math><mn>1</mn><mi>σ</mi></math> bound on <math><msub><mi>N</mi><mi>eff</mi></msub></math> is significantly improved from the global fit and becomes comparable to its current theoretical uncertainty, such that the latter will become important for this study at next generation experiments like future lepton colliders. <math><msub><mi>N</mi><mi>eff</mi></msub></math> from the global fit is also adopted to predict the primordial helium abundance <math><msub><mi>Y</mi><mi>P</mi></msub></math>, which significantly reduces the parameter space on the <math><msub><mi>Y</mi><mi>P</mi></msub><mo>−</mo><msub><mi>N</mi><mi>eff</mi></msub></math> plane. Through error propagation, we also conclude that reducing the experimental uncertainty of <math><msub><mi>Y</mi><mi>P</mi></msub></math> from metal-poor galaxies down below 0.2% could play an important role in deepening our understanding of the free neutron lifetime anomaly.

<math><msub><mi>N</mi><mi>eff</mi></msub></math> as a new physics probe in the precision era of cosmology

Using the functional method, one-loop matching of the type-I, -II and -III see-saw models are investigated and the results are presented in both the Green’s and the Warsaw bases. Although these models generate the same dimension-5 Weinberg operator, they could induce quite different types of dimension-6 effective operators that can be utilized for model discrimination. We also find the threshold effects from one-loop matching could be significant, which turn out to allow triggering electroweak symmetry breaking radiatively in type-II seesaw while forbid that in type-I/-III models. An analytical criterion for such radiative symmetry breaking is also derived in type-II seesaw. Finally, we investigate the indirect signatures from different types of dimension-6 operators at high-energy colliders, low-energy precision experiments and forward physics facilities for model discrimination.

Xu-Xiang Li

Jiang-Hao Yu

Neutrino seesaw models at one-loop matching: discrimination by effective operators

The type-II seesaw model is a possible candidate for simultaneously explaining non-vanishing neutrino masses and the observed baryon asymmetry of the Universe. In this work, we study in detail the pattern of phase transition and the gravitational wave production of this model. We find a strong first-order electroweak phase transition generically prefers positive Higgs portal couplings and a light triplet below ~ 550 GeV. In addition, we find the gravitational wave yield generated during the phase transition would be at the edge of BBO sensitivity and could be further examined by Ultimate-DECIGO.

Ruiyu Zhou

Ligong Bian

Electroweak phase transition and gravitational waves in the type-II seesaw model

We reinterpret COHERENT data within the Standard Model effective field theory (SMEFT), giving full consideration to the effect of matching onto the low-energy effective field theory (LEFT) and running to the characteristic energy scale. Within the same framework, we also investigate the prospects of next-generation neutrino oscillation experiments DUNE, T2HK, and JUNO including TAO, while in addition we take into account the matching between quantum mechanics neutrino nonstandard interaction (NSI) parameters and those charged and neutral current neutrino NSI parameters defined in the LEFT. Combining the results of two types of experiments, we analyze 1635 dimension-six SMEFT operators with no flavor assumptions and derive lower bounds to the UV scale <math><mi>Λ</mi></math>. From our analysis, we find COHERENT with CsI and LAr targets to be sensitive to new physics up to <math><mrow><mo>∼</mo><mn>900</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>, while the most powerful probe is obtained on <math><mrow><msub><mrow><mi>O</mi></mrow><mrow><msub><mrow><mi>l</mi><mi>e</mi><mi>d</mi><mi>q</mi></mrow><mrow><mn>1211</mn></mrow></msub></mrow></msub></mrow></math> with <math><mrow><mi>Λ</mi><mo>≳</mo><mn>450</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> due to the electron neutrino sample in the T2HK near detector. We also find DUNE and JUNO to be complementary to T2HK in exploring different subsets of SMEFT operators at about 25 TeV. We conclude that near detectors play a significant role in each experiment.

Hao-Lin Li

Jian Tang

Sampsa Vihonen

Exploring SMEFT induced nonstandard interactions: From COHERENT to neutrino oscillations

The number of relativistic species, N eff, has been precisely calculated in the standard model, and would be measured to the percent level by CMB-S4 in future. Neutral-current non-standard interactions would affect neutrino decoupling in the early Universe, thus modifying N eff. We parameterize those operators up to dimension-7 in the effective field theory framework, and then provide a complete, generic and analytical dictionary for the collision term integrals. From precision measurements of N eff, the most stringent constraint is obtained for the dimension-6 vector-type neutrino-electron operator, whose scale is constrained to be above about 195 (331) GeV from Planck (CMB-S4). We find our results complementary to other experiments like neutrino coherent scattering, neutrino oscillation, collider, and neutrino deep inelastic scattering experiments.

Neutrino non-standard interactions meet precision measurements of N eff

A complete, gauge-invariant computation of two-loop virtual corrections involving closed fermion loops to the polarized Møller scattering asymmetry is presented. The set of contributions involving two closed fermion loops and the set involving one closed fermion loop are numerically similar in magnitude to the one-loop bosonic corrections and yield an overall correction of 1.3% relative to the tree level asymmetry. We estimate sizes of the remaining two-loop contributions and discuss implications for the upcoming MOLLER (Measurement of a Lepton-Lepton Electroweak Reaction) experiment.

United States

Ayres Freitas

Hiren H. Patel

Michael J. Ramsey-Musolf

Parity-Violating Møller Scattering at Next-to-Next-to-Leading Order: Closed Fermion Loops

The Standard Model Effective Field Theory (SMEFT) provides a systematic and model-independent framework to study neutrino non-standard interactions (NSIs). We study the constraining power of the on-going neutrino oscillation experiments T2K, NOνA, Daya Bay, Double Chooz and RENO in the SMEFT framework. A full consideration of matching is provided between different effective field theories and the renormalization group running at different scales, filling the gap between the low-energy neutrino oscillation experiments and SMEFT at the UV scale. We first illustrate our method with a top- down approach in a simplified scalar leptoquark model, showing more stringent constraints from the neutrino oscillation experiments compared to collider studies. We then provide a bottom-up study on individual dimension-6 SMEFT operators and find NSIs in neutrino experiments already sensitive to new physics at ∼20 TeV when the Wilson coefficients are fixed at unity. We also investigate the correlation among multiple operators at the UV scale and find it could change the constraints on SMEFT operators by several orders of magnitude compared with when only one operator is considered. Furthermore, we find that accelerator and reactor neutrino experiments are sensitive to different SMEFT operators, which highlights the complementarity of the two experiment types.

Non-standard interactions in SMEFT confronted with terrestrial neutrino experiments

We study discovery prospects for a real triplet extension of the Standard Model scalar sector at the Large Hadron Collider (LHC) and a possible future 100 TeV pp collider. We focus on the scenario in which the neutral triplet scalar is stable and contributes to the dark matter relic density. When produced in pp collisions, the charged triplet scalar decays to the neutral component plus a soft pion or soft lepton pair, yielding a disappearing charged track in the detector. We recast current 13 TeV LHC searches for disappearing tracks, and find that the LHC presently excludes a real triplet scalar lighter than 248 (275) GeV, for a mass splitting of 172 (160) MeV with ℒ = 36 fb −1. The reach can extend to 497 (520) GeV with the collection of 3000 fb −1. We extrapolate the 13 TeV analysis to a prospective 100 TeV pp collider, and find that a ∼ 3 TeV triplet scalar could be discoverable with ℒ = 30 ab −1, depending on the degree to which pile up effects are under control. We also investigate the dark matter candidate in our model and corresponding present and prospective constraints from dark matter direct detection. We find that currently XENON1T can exclude a real triplet dark matter lighter than ∼ 3 TeV for a Higgs portal coupling of order one or larger, and the future XENON20T will cover almost the entire dark matter viable parameter space except for vanishingly small portal coupling.

Taiwan

Cheng-Wei Chiang

Chile

Giovanna Cottin

Kaori Fuyuto

Michael Ramsey-Musolf

Collider probes of real triplet scalar dark matter

We investigate a simplified freeze-in dark-matter model in which the dark matter only interacts with the standard-model neutrinos via a light scalar. The extremely small coupling for the freeze-in mechanism is naturally realized in several neutrino-portal scenarios with the secret neutrino interactions. We study possible evolution history of the hidden sector: the dark sector would undergo pure freeze-in production if the interactions between the dark-sector particles are negligible, while thermal equilibrium within the dark sector could occur if the reannihilation of the dark matter and the scalar mediator is rapid enough. We investigate the relic abundance in the freeze-in and dark freeze-out regimes, calculate evolution of the dark temperature, and study its phenomenological aspects on BBN and CMB constraints, the indirect-detection signature, as well as the potential to solve the small scale structure problem.