We investigate the discovery potential of the $T_{bc}$ state with $J^P = 0^+$ in proton-proton ( $pp$ ) collisions at LHCb at a center-of-mass energy of $\sqrt{s} = 13~{\rm{TeV}}$ . The study focuses on the decay channel $T_{bc} \to B^- D^+$ . A phenomenological approach is employed to construct the background model based on the associated production of $\textit{B}$ and $\textit{D}$ mesons, incorporating previously published LHCb results. Background processes are simulated using ${\mathtt{MadGraph5\_aMC@NLO}}$ and ${\mathtt{Pythia8.3}}$ . We explore the parameter space of the $T_{bc}$ mass, width, production cross section, and the effective double-parton scattering cross section ( $\sigma_{{\rm{eff}}}$ ) relevant for the $B D$ meson background. The integrated luminosity required for a $5\sigma$ discovery at LHCb is evaluated under various assumptions. In particular, we consider three representative $T_{bc}$ production cross section scenarios: an optimistic estimate of $103~{\rm{nb}}$ , an intermediate value of $18~{\rm{nb}}$ obtained by scaling from the $T_{cc}^+$ production cross section, and a conservative lower bound of $0.3~{\rm{nb}}$ . We find that a $5\sigma$ observation is achievable for a production cross section of $103~{\rm{nb}}$ , which is expected to be within reach during Run4. In contrast, the more realistic cross section estimate of $18~{\rm{nb}}$ requires the full Run5 dataset ( $300~{\rm{fb}}^{-1}$ ) under the most favorable parameter choices. For the conservative scenario, no significant signal would be observable even with $300~{\rm{fb}}^{-1}$ . In addition, we estimate the minimum observable $\sigma(T_{bc}) \times {\cal{B}}(T_{bc} \to $ $ B^- D^+)$ for a $5\sigma$ discovery under different luminosity scenarios, providing guidance for future experimental searches at LHCb.

China

Mingjie Feng

Yiming Li

France

Hua-Sheng Shao

Prospects for discovering strongly decaying doubly heavy T$_{bc}$ tetraquark states at LHCb * Mingjie Feng and Yiming Li is Supported by the National Natural Science Foundation of China (NSFC) (2175245, 12188102, W2443008). Hua-Sheng Shao is Supported by the European Research Council (101041109, 'BOSON') and the French National Research Agency (grant ANR-20-CE31-0015, 'PrecisOnium')

The dark matter scattering with atomic bound electrons is a crucial avenue for exploring the sub-GeV mass range. The commonly used factorization, where atomic effects are encoded in an overall form factor multiplying the free-electron scattering matrix element, is not necessarily true. Especially, the free-electron kinematics and phase space cannot consistently apply for off-shell bound electrons. Starting from the first principles of quantum field theory, we establish a theoretically consistent formalism to account for the atomic effects. By taking the scalar-type interaction as an example, we investigate the difference between the non-relativistic and relativistic calculations to show that the relativistic effects can lead to a $$30{-}50\%$$ reduction in the scattering phase space and differential cross section. In other words, not just a theoretically consistent formalism for the atomic effects but also relativistic calculation with Dirac equation are necessary.

Shao-Feng Ge

Japan

Jie Sheng

Chuan-Yang Xing

Relativistic atomic effects of dark matter electron scattering

We evaluate discovery prospects for photophobic axion-like particles (ALPs) in the $\textit{WWjj}$ final state at the High-Luminosity LHC (HL-LHC; $\sqrt{s}=14\ {\rm{TeV}}$ , ${\cal{L}}=3\ {\rm{ab}}^{-1}$ ). In the photophobic limit ( $g_{a\gamma\gamma}=0$ ), ALPs couple to electroweak gauge bosons and are produced in association with two jets ( $ pp\to jj\ a $ ) via both $\textit{s}$-channel electroweak exchange and vector boson fusion (VBF)–like topologies, followed by $a\to W^+W^-$ decay. We target the different-flavour dilepton mode $W^+W^- \to e^\pm\mu^\mp\nu \bar{\nu}$ with two jets and moderate missing transverse momentum. The analysis employs a two-step strategy: initial preselection that defines the signal-like final state, followed by a multivariate analysis (MVA) trained on dijet and dileptonic-$\textit{WW}$ kinematics from both the $\textit{s}$-channel and VBF-like production mechanisms to separate signal from background; the MVA threshold is optimized independently at each $m_a$ . We present 2$\textit{σ}$ and 5$\textit{σ}$ discovery sensitivities for the ALP–$\textit{W}$ coupling $g_{aWW}$ across the 170–4000 GeV mass range. For $260\ {\rm{GeV}}\le m_a\le1500\ {\rm{GeV}}$ , the 2$\textit{σ}$ (5$\textit{σ}$) sensitivity is approximately flat around $ 0.61(0.76)\ {\rm{TeV}}^{-1}$ . At large masses/couplings, the mapping between an experimental rate and a single EFT parameter $g_{aWW}$ can become UV sensitive, and we treat the extreme high-mass/high-coupling corner as an extrapolation; therefore, we also report model-independent discovery thresholds for the fiducial quantity $ \sigma(pp\to jj\ a)\times\rm{Br}(a\to W^+W^-) $ over the same mass range to enable reinterpretation for other models. These results indicate that the $WWjj$ topology offers competitive and complementary sensitivity to heavy photophobic ALPs at the HL-LHC.

Jiaojiao Feng

Ying-nan Mao

Kechen Wang

Discovery prospects for photophobic axion-like particles in the $\textit{WWjj}$ final state at the High-Luminosity LHC * Jiaojiao Feng and Kechen Wang are supported by the National Natural Science Foundation of China (11905162), the Excellent Young Talents Program of the Wuhan University of Technology (40122102, 40122103) and the research program of the Wuhan University of Technology (2020IB024, 104972025KFYjc0101). Ying-nan Mao is supported by the National Natural Science Foundation of China (12205227). The simulation and analysis work of this article was completed with the computational cluster provided by the Theoretical Physics Group at the Department of Physics, School of Physics and Mechanics, Wuhan University of Technology

The JUNO first data and the recent neutrino global fit results are implemented in the sum rule from the residual <math altimg='si1.svg'><msubsup><mi mathvariant='double-struck'>Z</mi><mn>2</mn><mi>s</mi></msubsup></math> and <math altimg='si2.svg'><msubsup><mover><mrow><mi mathvariant='double-struck'>Z</mi></mrow><mo stretchy='true'>&#8254;</mo></mover><mn>2</mn><mi>s</mi></msubsup></math> symmetries to make prediction of the leptonic Dirac CP phase <italic>&#948;<inf>D</inf></italic>. Without involving model parameters, the probability distribution of <italic>&#948;<inf>D</inf></italic> can be readily obtained from the experimental measurements of the three mixing angles. We then confront the theoretical predictions with the global fit results for the CP phase as well as the T2K and NOvA joint analysis for their CP measurements to give the data preference of the two residual symmetries with Bayes factor for both normal and inverted orderings. We further extend our analysis to a two-dimensional probability distribution to fully explore the correlation between the CP phase <italic>&#948;<inf>D</inf></italic> and the atmospheric angle <italic>&#952;<inf>a</inf></italic>&#8239;&#8801;&#8239; <italic>&#952;</italic> <inf>23</inf>.

South Korea

Chui-Fan Kong

João Paulo Pinheiro

CP prediction from residual <math altimg='si1.svg'><msubsup><mi mathvariant='double-struck'>Z</mi><mn>2</mn><mi>s</mi></msubsup></math> and <math altimg='si2.svg'><msubsup><mover><mrow><mi mathvariant='double-struck'>Z</mi></mrow><mo stretchy='true'>&#8254;</mo></mover><mn>2</mn><mi>s</mi></msubsup></math> symmetries with the latest data

The first results from the JUNO reactor neutrino oscillation experiment improve our knowledge of neutrino masses and mixing parameters, especially the solar angle $\textit{θ}$ ≡ $\textit{θ}$ and the solar mass squared difference $$ \Delta {m}_s^2\equiv \Delta {m}_{21}^2 $$ . We discuss the implications of these results on neutrinoless double beta decay by itself and in combination with the global fit of neutrino oscillation experiments, the JUNO first data, and cosmological constraints on the neutrino mass sum. For the effective mass ⟨$\textit{m}$ ⟩, the uncertainties in its lower limits for both mass orderings and upper limits for the normal ordering are largely reduced. Since the cosmological CMB and DESI BAO data put a stringent constraint on the neutrino mass scale, we also show how the probability distribution of both the real and imaginary parts of the effective mass ⟨$\textit{m}$ ⟩ on the complex plane is affected. Especially, the funnel region with |⟨$\textit{m}$ ⟩| ≲ 1 meV receives larger chance to happen. Correspondingly, the chance of determining the two Majorana CP phases simultaneously in this region also increases with reduced uncertainty.

Germany

Manfred Lindner

João Pinheiro

Neutrinoless double beta decay in light of JUNO first data

<p>Instead of the energy recoil signal at direct detection experiments, dark fermion appears as missing energy at hadron colliders. For a fermionc dark sector particle that coupled with quarks and neutrino via absorption operators, its production at collider is accompanied by an invisible neutrino. We study in details the mono-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> (photon, jet, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math>) productions at the Large Hadron Collider (LHC). We start from the quark-level absorption operators to make easy comparison between the collider and direct detection experiments. In other words, we study the model-independent constraints on a dark fermion with absorption operator. In addition, the interplay and comparison with the possible detection at the neutrino experiments, especially Borexino, is also briefly discussed. We find that light nuclear target can provide the stronger constraints on both spin-dependent and spin-independent absorption operators.</p>

Kai Ma

Lin-Yun He

Ning Zhou

Complementary search of fermionic absorption operators at hadron colliders and direct detection experiments

We analyzed two-loop planar contributions to a three-body form factor at next-to-leading power in the high-energy limit, where the masses of the external particles are much smaller than their energies. Calculations were performed by exploiting differential equations for the expansion coefficients, both to facilitate linear relations among them and to derive their analytic expressions. The results are expressed in terms of generalized polylogarithms involving a few simple symbol letters. Our method can readily be applied to calculations of non-planar contributions as well. Our results provide crucial information for establishing sub-leading factorization theorems for massive scattering amplitudes in the high-energy limit.

Yishuai Guo

Zhi-Feng Liu

Mingming Lu

Tianya Xia

Li-Lin Yang

A three-body form factor at sub-leading power in the high-energy limit: planar contributions * Supported in part by the National Natural Science Foundation of China Sunder (12375097, 12347103) and the Fundamental Research Funds for the Central Universities. Zhi-Feng Liu was supported by the China Postdoctoral Science Foundation (2023M733123, 2023TQ0282) and the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation

The beta decay of $$^{77}$$ Ge and $$^{77\textrm{m}}$$ Ge, both produced by neutron capture on $$^{76}$$ Ge, is a potential background for Germanium based neutrinoless double-beta decay search experiments such as GERDA or the LEGEND experiment. In this work we present a search for $$^{77}$$ Ge decays in the full GERDA Phase II data set. A delayed coincidence method was employed to identify the decay of $$^{77}$$ Ge via the isomeric state of $$^{77}$$ As ( $$9/2^+$$ , $${475}\,\hbox {keV}$$ , $${T_{1/2} = {114}\,{\upmu }\hbox {s}}$$ , $$^{77\textrm{m}}$$ As). New digital signal processing methods were employed to select and analyze pile-up signals. No signal was observed, and an upper limit on the production rate of $$^{77}$$ Ge was set at $$<0.216$$ nuc/(kg $$\cdot $$ yr) (90% CL). This corresponds to a total production rate of $$^{77}$$ Ge and $$^{77\textrm{m}}$$ Ge of $$<{0.38}$$ nuc/(kg $$\cdot $$ yr) (90% CL), assuming equal production rates. A previous Monte Carlo study predicted a value for in-situ $$^{77}$$ Ge and $$^{77\textrm{m}}$$ Ge production of (0.21 ± 0.07) nuc/(kg.yr), a prediction that is now further corroborated by our experimental limit. Moreover, tagging the isomeric state of $$^{77\textrm{m}}$$ As can be utilised to further suppress the $$^{77}$$ Ge background. Considering the similar experimental configurations of LEGEND-1000 and GERDA, the cosmogenic background in LEGEND-1000 at LNGS is estimated to remain at a sub-dominant level.

United Kingdom

M. Agostini

A. Alexander

Switzerland

G. Araujo

Russia

A. Bakalyarov

Italy

M. Balata

I. Barabanov

L. Baudis

C. Bauer

S. Belogurov

A. Bettini

L. Bezrukov

V. Biancacci

E. Bossio

V. Bothe

R. Brugnera

A. Caldwell

S. Calgaro

C. Cattadori

A. Chernogorov

P.J. Chiu

T. Comellato

V. D’Andrea

E. Demidova

N. Marco

E. Doroshkevich

M. Fomina

A. Gangapshev

A. Garfagnini

C. Gooch

P. Grabmayr

V. Gurentsov

K. Gusev

United States

J. Hakenmüller

S. Hemmer

W. Hofmann

J. Huang

Belgium

M. Hult

L. Inzhechik

Hungary

J. Janicskó Csáthy

J. Jochum

M. Junker

V. Kazalov

Y. Kermaïdic

H. Khushbakht

T. Kihm

K. Kilgus

I. Kirpichnikov

A. Klimenko

K. Knöpfle

O. Kochetov

V. Kornoukhov

P. Krause

V. Kuzminov

M. Laubenstein

M. Lindner

I. Lippi

A. Lubashevskiy

B. Lubsandorzhiev

G. Lutter

C. Macolino

B. Majorovits

W. Maneschg

G. Marshall

Poland

M. Misiaszek

M. Morella

Y. Müller

I. Nemchenok

M. Neuberger

L. Pandola

K. Pelczar

L. Pertoldi

P. Piseri

A. Pullia

C. Ransom

L. Rauscher

M. Redchuk

S. Riboldi

N. Rumyantseva

C. Sada

S. Sailer

F. Salamida

S. Schönert

J. Schreiner

A.K. Schütz

O. Schulz

M. Schwarz

B. Schwingenheuer

O. Selivanenko

E. Shevchik

M. Shirchenko

L. Shtembari

H. Simgen

A. Smolnikov

D. Stukov

S. Sullivan

A. Vasenko

A. Veresnikova

C. Vignoli

K. Sturm

T. Wester

Search for the in-situ production of $$^{77}$$ Ge in the GERDA neutrinoless double-beta decay experiment

<p>We propose the possibility of using the near detector at reactor neutrino experiments to probe the renormalization group (RG) running effect on the leptonic Dirac <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> phase <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>δ</mi><mi>D</mi></msub></math>. Although the reactor neutrino oscillation cannot directly measure <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>δ</mi><mi>D</mi></msub></math>, it can probe the deviation <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mi>δ</mi><mo>≡</mo><msub><mi>δ</mi><mi>D</mi></msub><mo stretchy="false">(</mo><msubsup><mi>Q</mi><mi>d</mi><mn>2</mn></msubsup><mo stretchy="false">)</mo><mo>−</mo><msub><mi>δ</mi><mi>D</mi></msub><mo stretchy="false">(</mo><msubsup><mi>Q</mi><mi>p</mi><mn>2</mn></msubsup><mo stretchy="false">)</mo></math> caused by the RG running. Being a key element, the mismatched momentum transfers at neutrino production (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>Q</mi><mi>p</mi><mn>2</mn></msubsup></math>) and detection (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>Q</mi><mi>d</mi><mn>2</mn></msubsup></math>) processes can differ by two orders. We illustrate this concept with the upcoming Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) experiment and obtain the projected sensitivity to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> RG running beta function <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>β</mi><mi>δ</mi></msub></math>.</p>

Brazil

Pedro Pasquini

Testing the RG running of the leptonic Dirac <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> phase with reactor neutrinos

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).

Zhuoni Qian

Michael Ramsey-Musolf

Jia Zhou

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