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.

China

Shao-Feng Ge

South Korea

Chui-Fan Kong

Germany

Manfred Lindner

João Pinheiro

Neutrinoless double beta decay in light of JUNO first data

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.

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

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>.

Japan

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: $\textit{e}$

The cosmic gravitational focusing (CGF) of relic neutrinos can provide an independent measurement of the absolute neutrino masses <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>i</mi></mrow></msub></mrow></math> with fourth-power dependence (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>m</mi><mi>i</mi><mn>4</mn></msubsup></math>). We demonstrate in this paper for the first time how this can help identify the neutrino mass ordering, using the fact that total mass falling below the inverted ordering threshold allows the discrimination of inverted ordering. Upon incorporating the projected CGF sensitivity at DESI, the preference for the normal ordering with a prior <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∑</mo><msub><mi>m</mi><mi>i</mi></msub><mo>&gt;</mo><mn>0.059</mn><mtext> </mtext><mtext> </mtext><mi>eV</mi></math> would increase from the original 89.9% of the existing matter clustering method with the DESI analysis to 98.2% while the inverted ordering is further disfavored from 10.1% to 1.8%. We also show how this can affect the prospects of the neutrinoless double beta and single beta decay measurements.

Liang Tan

Identifying neutrino mass ordering with cosmic gravitational focusing

We propose a new scenario that both the dark matter freeze-out in the early Universe and its possible annihilation for indirect detection around a supermassive black hole are enhanced by a Breit-Wigner resonance. With the mediator mass larger than the total initial dark matter mass, this annihilation is almost forbidden at late times. Thus, the stringent cosmic microwave background and indirect detection constraints do not apply. However, a supermassive black hole can accelerate the dark matter particles to reactivate this resonant annihilation whose subsequent decay to photons leaves a unique signal. The running Fermi-LAT and the future COSI satellites can test this scenario.

Yu Cheng

Jie Sheng

Tsutomu T. Yanagida

Dark matter annihilation via Breit-Wigner enhancement with heavier mediator

We propose practical ways of differentiating the various (Breit-Wigner, theoretical, and energy-dependent) resonance schemes of unstable particles at lepton colliders. First, the energy-dependent scheme can be distinguished from the other two by fitting the <italic>Z</italic> lineshape scan and forward-backward asymmetries at LEP and future lepton colliders with the <italic>Z</italic> mass <math altimg='si1.svg'><msub><mrow><mi>m</mi></mrow><mrow><mi>Z</mi></mrow></msub></math>, decay width <math altimg='si2.svg'><msub><mrow><mi mathvariant='normal'>&#915;</mi></mrow><mrow><mi>Z</mi></mrow></msub></math>, and coupling strength as fitting parameters. Although the Breit-Wigner and theoretical schemes work equally well, the scheme conversion requires the decay width <math altimg='si2.svg'><msub><mrow><mi mathvariant='normal'>&#915;</mi></mrow><mrow><mi>Z</mi></mrow></msub></math> to scale inversely with <math altimg='si1.svg'><msub><mrow><mi>m</mi></mrow><mrow><mi>Z</mi></mrow></msub></math> rather than the usual linear dependence from theoretical calculation. These contradicting behaviors can be used to distinguish the Breit-Wigner and theoretical schemes by the precision <italic>Z</italic> measurements with single parameter ( <math altimg='si1.svg'><msub><mrow><mi>m</mi></mrow><mrow><mi>Z</mi></mrow></msub></math>) fit at future lepton colliders. For the <italic>WW</italic> threshold scan, its combination with the precise Fermi constant provides another way of distinguishing the Breit-Wigner and theoretical schemes.

Ui Min

Verifying the resonance schemes of unstable particles at lepton colliders

We propose the nucleon consumption induced by dark matter (DM) as a new scenario to overcome the energy threshold of direct detection. It can be realized with proton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mo>+</mo><mi>p</mi><mo stretchy="false">→</mo><mi>χ</mi><mo>+</mo><msup><mo>ℓ</mo><mo>+</mo></msup></math>) or neutron (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mo>+</mo><mi>n</mi><mo stretchy="false">→</mo><mi>χ</mi><mo>+</mo><mi>ν</mi></math>) target. Both effective operators and concrete models are provided to illustrate the idea. Since the initial DM and nucleon velocity is only <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mo>/</mo><mn>4</mn></math> of the speed of light, respectively, the cross section and hence event rate are determined by the involved particle masses and not affected by the nucleon Fermi motion. Of the two realizations, the proton consumption has richer phenomena with both charged lepton and the daughter nuclei deexcitation to allow double or even triple coincidence to significantly suppress the background. We also illustrate the projected sensitivities at DM and neutrino experiments such as PandaX-4T, DUNE, JUNO, and Hyper-K.

Xiao-Dong Ma

Nucleon consumption and mass-energy conversion induced by dark matter