We study the new $Z'$ boson as a portal for the production of Higgs bosons $h_0$ and $H_0$ predicted by the Bestest Little Higgs Model through Higgs-strahlung processes $\mu^+\mu^- \to (Z, Z') \to Zh_0, ZH_0$ . We focus on the resonant and nonresonant effects of the $Zh_0, ZH_0$ signals. In our analysis, we consider the center-of-mass energies of $\sqrt{s}=3, 4, 6, 10, 30$ TeV and integrated luminosities of ${\cal{L}}=2, 4, 6, 10, 30$ ${ {\rm{ab}}^{-1}}$ projected for a future muon collider. The possibility of performing precision measurements for Higgs bosons $h_0$ and $H_0$ is very promising for the future muon collider. Furthermore, our results may be useful to the High Energy Physics community. Complementarily, we generate and provide the Feynman rules necessary for studying processes $\mu^+\mu^- \to (Z, Z') \to Zh_0, ZH_0$ .

J.M. Martínez-Martínez

A. Gutiérrez-Rodríguez

E. Cruz-Albaro

M.A. Hernández-Ruíz

New $\textit{Z}$' boson of the bestest little Higgs model as a portal to signatures of Higgs bosons $\textit{h}$ $_{0}$ and $\textit{H}$ $_{0}$ at the future muon collider

Due to Heisenberg’s uncertainty principle, atomic electrons localized around the nucleus exhibit a characteristic momentum distribution that, in elements with high atomic number, remains significant up to relativistic values. Consequently, in fixed-target experiments, atoms can effectively act as electron accelerators, increasing the centre-of-mass energy in collisions with beam particles. In this work, we leverage this effect to explore its potential for new physics searches. We consider positrons from beams of various energies annihilating with atomic electrons in a W fixed target. We compute the production rates of new vector bosons and pseudoscalar particles as functions of their couplings and masses. We show that the electron-at-rest approximation significantly underestimates the mass reach for producing these new states compared to the results obtained by properly accounting for atomic electron momenta. In particular, we estimate the sensitivity for detecting these new particles using the positron beam at the Beam Test Facility linac at the Laboratori Nazionali di Frascati, the H4 beamline in the CERN North Area, and the proposed Continuous Electron Beam Accelerator Facility of Jefferson Laboratory.

Italy

Fernando Arias-Aragón

Giovanni Grilli di Cortona

Estonia

Enrico Nardi

France

Léo Veissière

Atoms as electron accelerators for new physics searches

While dual-phase xenon time projection chambers have driven the sensitivity toward weakly interacting massive particles at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>GeV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>TeV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></math> mass scale, the scope for sub-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>GeV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></math> dark matter particles is hindered by a limited nuclear recoil energy detection threshold. One approach to probe for lighter candidates is to consider cases where they have been boosted by collisions with cosmic rays in the Milky Way, such that the additional kinetic energy lifts their induced signatures above the nominal threshold. In this Letter, we report first results of a search for cosmic ray-boosted dark matter (CRDM) with a combined <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>4.2</mn><mtext> </mtext><mtext> </mtext><mi>metric</mi><mtext> </mtext><mi>ton</mi><mo>/</mo><mi>yr</mi></mrow></math> exposure from the LUX-ZEPLIN experiment. We observe no excess above the expected backgrounds and establish world-leading constraints on the spin-independent CRDM-nucleon cross section as small as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>3.9</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>33</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>cm</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math> at 90% confidence level for sub-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>GeV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></math> masses.

United States

J. Aalbers

D.S. Akerib

United Kingdom

A.K. Al Musalhi

F. Alder

C.S. Amarasinghe

A. Ames

T.J. Anderson

N. Angelides

H.M. Araújo

J.E. Armstrong

M. Arthurs

A. Baker

S. Balashov

J. Bang

J.W. Bargemann

Switzerland

E.E. Barillier

K. Beattie

T. Benson

A. Bhatti

A. Biekert

T.P. Biesiadzinski

H.J. Birch

E. Bishop

G.M. Blockinger

B. Boxer

C.A.J. Brew

Portugal

P. Brás

S. Burdin

M. Buuck

M.C. Carmona-Benitez

M. Carter

A. Chawla

H. Chen

J.J. Cherwinka

Y.T. Chin

N.I. Chott

M.V. Converse

R. Coronel

A. Cottle

G. Cox

D. Curran

C.E. Dahl

I. Darlington

S. Dave

A. David

J. Delgaudio

S. Dey

L. de Viveiros

L. Di Felice

C. Ding

J.E.Y. Dobson

E. Druszkiewicz

S. Dubey

S.R. Eriksen

A. Fan

N.M. Fearon

N. Fieldhouse

S. Fiorucci

H. Flaecher

E.D. Fraser

Australia

T.M.A. Fruth

R.J. Gaitskell

A. Geffre

J. Genovesi

C. Ghag

R. Gibbons

S. Gokhale

J. Green

M.G.D. van der Grinten

J.J. Haiston

C.R. Hall

T. Hall

S. Han

E. Hartigan-O’Connor

S.J. Haselschwardt

M.A. Hernandez

S.A. Hertel

G. Heuermann

G.J. Homenides

M. Horn

D.Q. Huang

D. Hunt

E. Jacquet

R.S. James

M.K. Kannichankandy

A.C. Kaboth

A.C. Kamaha

D. Khaitan

A. Khazov

J. Kim

South Korea

Y.D. Kim

J. Kingston

R. Kirk

D. Kodroff

L. Korley

E.V. Korolkova

H. Kraus

S. Kravitz

L. Kreczko

V.A. Kudryavtsev

New Constraints on Cosmic Ray-Boosted Dark Matter from the LUX-ZEPLIN Experiment

Recently, the Belle II Collaboration reported the branching fraction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msup><mi>B</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>+</mo></msup><mi>ν</mi><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>2.3</mn><mo>±</mo><mn>0.7</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math> with a significance of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3.5</mn><mi>σ</mi></math>, which is <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2.7</mn><mi>σ</mi></math> above the Standard Model expectation. Motivated by this measurement, we calculate this decay channel at the next-to-leading order and twist-three level using the perturbative QCD approach. By combining lattice QCD data with our results, we obtain form factors with improved reliability. Using these form factors, we estimate the branching ratios of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>+</mo></msup></math> semileptonic flavor-changing neutral current decays, including <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>+</mo></msup><mi>ν</mi><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math>. To address the anomalies in these two processes, we introduce a leptoquark model as a new physics scenario. Analyzing five possible types of leptoquarks, we successfully explain the latest experimental measurements and derive further constraints on the leptoquarks. Furthermore, the single leptoquark model becomes invalid once the stringent constraints from process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mi>s</mi></msub><mo stretchy="false">→</mo><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mi>s</mi></msub><mo>−</mo><mover accent="true"><msub><mi>B</mi><mi>s</mi></msub><mo stretchy="true">¯</mo></mover></math> mixing is taken into account.

China

Chao-Qi Zhang

Jin Sun

Zhi-Peng Xing

Rui-Lin Zhu

Probing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>+</mo></msup></math> semileptonic FCNC decay with new physics effects in the PQCD approach

We present a comprehensive investigation exploring the theoretical framework of Einstein–Aether gravity theory when combined with two modified cosmological paradigms: the Barrow Agegraphic Dark Energy (BADE) and its newer variant, the New Barrow Agegraphic Dark Energy (NBADE). Our study focuses on reconstructing the functional form of the Einstein–Aether Lagrangian component $\textit{F}$($\textit{K}$) from these phenomenological dark energy models. Model parameters are constrained using a Markov Chain Monte Carlo (MCMC) approach based on multiple datasets, including cosmic chronometers (CC), Baryon Acoustic Oscillations (BAO), and the Pantheon+SH0ES compilation. Using best-fit parameters, we analyze various cosmological diagnostics: Hubble and deceleration parameter evolution, dark energy equation of state ( $$\omega _{DE}$$ ), density parameter trajectories, $$\omega _{DE}'$$ – $$\omega _{DE}$$ phase space behavior, statefinder diagnostics $$(r,s^*)$$ and ($\textit{r}$, $\textit{q}$), and Om(z) trajectories. Both models exhibit late-time acceleration, with the dark energy sector showing a quintessence-like nature in the current epoch and evolving toward a phantom regime in the future. Stability analysis based on the squared sound speed ( $$v_s^2$$ ) highlights partial epoch-dependent stability. While our results demonstrate reasonable agreement with observational data and reveal physically plausible dynamics, the models do not yet offer a fundamentally superior alternative to other dark energy reconstructions. Nonetheless, their behavior under modified entropy assumptions and their flexibility in dynamical diagnostics provide a useful framework for probing non-standard extensions of Einstein–Aether gravity and dark energy phenomenology.

India

Banadipa Chakraborty

Tamal Mukhopadhyay

Anamika Kotal

Ujjal Debnath

Reconstructions of Einstein–Aether gravity from barrow agegraphic and new barrow agegraphic dark energy models: examinations and observational limits

Energy correlators have recently come to the forefront of jet substructure studies at colliders due to their remarkable properties: they naturally separate physics at different scales, are robust to contamination from soft radiation, and offer a direct connection with quantum field theory. The current parametrization used for energy correlators, however, is based on redundant pairwise angles with complex phase space restrictions. In this Letter, we introduce a new parametrization of energy correlators that features a simpler phase space structure and preserves information about the orientation of jet constituents. Further, our parametrization drastically reduces the computational cost to compute energy correlators on experimental data; whereas the time to compute a traditional projected <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>-point energy correlator scales as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>M</mi><mi>N</mi></msup><mo>/</mo><mi>N</mi><mo>!</mo></math> on a jet with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>M</mi></math> particles, our new parametrization achieves a scaling of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>M</mi><mn>2</mn></msup><mi>ln</mi><mi>M</mi></math>, remarkably independently of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>. Even for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi><mo>=</mo><mn>3</mn></math>, this improved scaling is particularly important for studies of heavy ion collisions, and higher values of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> will enable new qualitative understanding of gauge theories. Theoretical calculations for our new energy correlators differ from those of traditional parametrizations only at next-to-next-to-leading logarithmic accuracy and beyond, and we expect that our simpler phase space structure will simplify those calculations. We also discuss how to extend our parametrization to resolved <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>-point energy correlators that encode angular distances between greater numbers of particles, yielding intuitive visualizations of jet substructure that are qualitatively different for different jet samples. We propose two possible generalizations for probing multiprong jets and testing jet scaling behavior.

Samuel Alipour-fard

Netherlands

Ankita Budhraja

Jesse Thaler

Wouter J. Waalewijn

New Angles on Energy Correlators

We illustrate the potential of a future high-intensity $$e^+ e^-$$ collider running at the $\textit{Z}$ pole in probing extensions of the Standard Model via precise measurements of flavor-changing processes. We illustrate this potential both within effective field theories and simplified models inspired by current $\textit{B}$-physics data, focusing on selected flavor-physics measurement projections at FCC-ee, and by the theoretically well-motivated scenario of TeV-scale new physics predominantly coupled to third-generation fields. In particular, we demonstrate the key role played by the interplay among different flavor-physics measurements, and between flavor and electroweak measurements, in cornering the New Physics parameter space. Updated constraints on new physics, in the limit that no deviations from the Standard Model are observed, are also presented.

Germany

Lukas Allwicher

Gino Isidori

Marko Pesut

Flavored circular collider: cornering New Physics at FCC-ee via flavor-changing processes

We explore the prospects for probing new physics (NP) beyond the Standard Model (SM) at the future lepton colliders through precision measurements of $\textit{e}$ $\textit{e}$ → $$ f\overline{f} $$ observables off the $\textit{Z}$ resonance. We consider the interference between the SM contributions and those arising from the dimension-6 four-fermion effective operators that encode the effects of NP, yielding a linear dependence on the latter. This linear dependence in general increases with the collision energy offset from the $\textit{Z}$ pole. We consider a variety of asymmetries in order to enhance the NP sensitivity while reducing the experimental systematic and theoretical SM uncertainties: the inclusive above- and below-$\textit{Z}$-resonance cross section asymmetry ($\textit{A}$ ) as well as the conventional forward-backward ($\textit{A}$ ) and polarization ($\textit{A}$ ) asymmetries. Based on the projected statistical uncertainties at the Circular Electron-Positron Collider (CEPC), we find that the measurement of $\textit{A}$ could extend the sensitivity to the NP mass scale by as much as a factor of ~ 7 compared to the present reach obtained with the CERN Large Electron Positron Collider. The projected systematic theoretical SM uncertainties substantially reduce this sensitivity gain. For $\textit{A}$ , the experimental systematic uncertainties has a marginal impact on the gain in NP reach, whereas the SM theoretical uncertainties remain a significant barrier to realizing the full NP sensitivity. Analogous conclusions apply to the CERN Future Circular Collider (FCC-ee) and International Linear Collider (ILC).

Shao-Feng Ge

Zhuoni Qian

Michael Ramsey-Musolf

Jia Zhou

New physics off the $\textit{Z}$-pole: $\textit{e}$

We revisit and extend the construction of six-dimensional orientifolds built upon the $\textit{T}$ /$\textit{ℤ}$ orbifolds with a non-vanishing Kalb-Ramond background, both in the presence of $$ \mathcal{N} $$ = (1, 0) supersymmetry and Brane Supersymmetry Breaking, thus amending some statements present in the literature. In the $\textit{N}$ = 2 case, we show how the gauge groups on unoriented D9 and D5 (anti-)branes do not need to be correlated, but can be independently chosen complex or real. For $\textit{N}$ > 2 we find that the Diophantine tadpole conditions severely constrain the vacua. Indeed, only the $\textit{N}$ = 4 orbifold with a rank-two Kalb-Ramond background may admit integer solutions for the Chan-Paton multiplicities, if the $\textit{ℤ}$ fixed points support O5 planes, both with and without supersymmetry. All other cases would involve a fractional number of branes, which is clearly unacceptable. We check the consistency of the new $\textit{ℤ}$ and $\textit{ℤ}$ vacua by verifying the unitarity constraints for string defects coupled to Ramond-Ramond two-forms entering the Green-Schwarz-Sagnotti mechanism.

Giorgio Leone

New comments on six-dimensional orientifold vacua with reduced rank and unitarity constraints

Motivated by a small but intriguing excess observed in the decay mode $\textit{H}$ → $\textit{ℓ}$ $\textit{ℓ}$ $\textit{γ}$ reported by both the ATLAS and CMS collaborations, we explore the possibility that new physics contributes directly to the effective $$ H\overline{\mathcal{ll}}\gamma $$ coupling rather than modifying the $\textit{Z}$ peak. Concretely, we consider a dimension-8 operator that could arise from new particles via box diagrams. Such non-resonant contribution may provide an alternative origin for current or future excesses. We examine how experimental cuts may distinguish between possible modifications of the $\textit{Z}$ peak and non-resonant contributions. The currently measured excess requires that the new physics scale is relatively low (Λ ~ $\textit{v}$). However, we show that it may remain within current experimental bounds. In particular, we illustrate this using a simplified model, motivated by the dark matter problem, and discuss its other experimental constraints.

Belgium

Aliaksei Kachanovich

Jean Kimus

Steven Lowette

Michel Tytgat

On new physics off the Z peak in $\textit{H → ℓ}$