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>.

China

Shao-Feng Ge

Chui-Fan Kong

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

United States

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

The fragmentation reactions of neutron-rich unstable nuclei $^{81}$Ga and $^{82}$Ge at 250 MeV/nucleon have been studied in order to search the optimal mean for the production of very neutron-rich nuclei in the vicinity of $^{78}$Ni. The newly measured cross sections were compared with various calculations, showing a good agreement with EPAX3.01. The present work provides experimental insights into the two-step scheme—fragmentation following fission—as a method to produce very neutron-rich nuclei through a combination of ISOL and fragmentation of post-accelerated beams of unstable nuclei. Our results enable an evaluation of the potential of the two-step scheme in the production of very neutron-rich nuclei for the $^{78}$Ni region. The two-step scheme using fragmentation of a post-accelerated $^{81}$Ga beam could be an option to produce neutron-rich nuclei around $^{78}$Ni when the $^{81}$Ga beam intensity reaches <math><mn>1.0</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>8</mn></mrow></msup></math> pps, compared to the one-step scheme with fission of $^{238}$U.

X.H. Sun

H. Wang

K. Yoneda

N. Aoi

H. Baba

Poland

P. Bednarczyk

Hungary

Zs. Dombrádi

P. Doornenbal

Zs. Fülöp

S. Go

T. Hashimoto

E. Ideguchi

K. Kobayashi

Y. Kondo

Hong Kong

J. Lee

H.N. Liu

W.P. Liu

J.L. Lou

M. Matsushita

R. Minakata

T. Motobayashi

D. Nishimura

H. Otsu

H. Sakurai

Y. Shiga

Y.P. Shen

D. Sohler

D. Steppenbeck

Y.L. Sun

S. Takeuchi

A. Tamii

R. Tanaka

Z.Y. Tian

Zs. Vajta

T. Yamamoto

X.F. Yang

Z.H. Yang

Y.L. Ye

R. Yokoyama

J. Zenihiro

Production of neutron-rich nuclei in the vicinity of Ni: Fragmentation reactions of unstable Ga and Ge beams

The origin of neutrino masses remains unknown. Both the vacuum mass and the dark mass generated by the neutrino interaction with dark matter (DM) particles or fields can fit the current oscillation data. The dark mass squared is proportional to the DM number density and, therefore, varies on the galactic scale with much larger values around the Galactic Center. This affects the group velocity and the arrival time delay of core-collapse supernovae (SN) neutrinos. This time delay, especially for the <math><mrow><msub><mrow><mi>ν</mi></mrow><mrow><mi>e</mi></mrow></msub></mrow></math> neutronization peak with a sharp time structure, can be used to distinguish the vacuum and dark neutrino masses. For illustration, we explore the potential of the Deep Underground Neutrino Experiment (DUNE), which is sensitive to <math><msub><mi>ν</mi><mi>e</mi></msub></math>. Our simulations show that DUNE can distinguish the two neutrino mass origins at more than <math><mn>5</mn><mi>σ</mi></math> C.L., depending on the observed local value of neutrino mass, the neutrino mass ordering, the DM density profile, and the SN location.

Germany

Alexei Y. Smirnov

Testing the Origins of Neutrino Mass with Supernova-Neutrino Time Delay

We report the first search for the elastic scatterings between cosmic-ray boosted sub-MeV dark matter (DM) and electrons in the PandaX-4T liquid xenon experiment. Sub-MeV DM particles can be accelerated by scattering with electrons in the cosmic rays and produce detectable electron recoil signals in the detector. Using the commissioning data from PandaX-4T of <math><mrow><mn>0.63</mn><mtext> </mtext><mtext> </mtext><mi>tonne</mi><mo>·</mo><mi>year</mi></mrow></math> exposure, we set new constraints on DM-electron scattering cross sections for DM masses ranging from <math><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>eV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></math> to <math><mn>3</mn><mtext> </mtext><mtext> </mtext><mi>keV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></math>.

Xiaofeng Shang

Abdusalam Abdukerim

Zihao Bo

Wei Chen

Xun Chen

Yunhua Chen

Chen Cheng

Zhaokan Cheng

Xiangyi Cui

Yingjie Fan

Deqing Fang

Lisheng Geng

Karl Giboni

Xuyuan Guo

Chencheng Han

Ke Han

Changda He

Jinrong He

Di Huang

Junting Huang

Zhou Huang

Ruquan Hou

Yu Hou

Xiangdong Ji

Xiangpan Ji

Yonglin Ju

Chenxiang Li

Jiafu Li

Mingchuan Li

Shuaijie Li

Tao Li

Qing Lin

Jianglai Liu

Congcong Lu

Xiaoying Lu

Lingyin Luo

Yunyang Luo

Wenbo Ma

Yugang Ma

Yajun Mao

Yue Meng

Xuyang Ning

Binyu Pang

Ningchun Qi

Zhicheng Qian

Xiangxiang Ren

Nasir Shaheed

Xiyuan Shao

Guofang Shen

Manbin Shen

Lin Si

Wenliang Sun

Yi Tao

Anqing Wang

Meng Wang

Qiuhong Wang

Shaobo Wang

Siguang Wang

Wei Wang

Xiuli Wang

Xu Wang

Zhou Wang

Yuehuan Wei

Mengmeng Wu

Weihao Wu

Yuan Wu

Mengjiao Xiao

Xiang Xiao

Kaizhi Xiong

Binbin Yan

Xiyu Yan

Yong Yang

Chunxu Yu

Ying Yuan

Zhe Yuan

Youhui Yun

Xinning Zeng

Minzhen Zhang

Peng Zhang

Shibo Zhang

Shu Zhang

Tao Zhang

Wei Zhang

Yang Zhang

Yingxin Zhang

Yuanyuan Zhang

Li Zhao

Jifang Zhou

Ning Zhou

Xiaopeng Zhou

Yubo Zhou

Zhizhen Zhou

Chen Xia

Search for Cosmic-Ray Boosted Sub-MeV Dark-Matter–Electron Scattering in PandaX-4T

We investigate the incoherent regime of the fermionic dark matter absorption by nuclei using the relativistic Fermi gas model and nuclear form factors. With the momentum transfer being roughly equal to the dark matter mass <math><msub><mi>m</mi><mi>χ</mi></msub></math>, the incoherent regime contributes significantly to the absorption process for <math><msub><mi>m</mi><mi>χ</mi></msub><mo>≳</mo><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> with a spin-independent operator and for even smaller mass with a spin-dependent one. We also compare the situations for various target nuclei (<math><mrow><mmultiscripts><mrow><mi>Xe</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>131</mn></mrow></mmultiscripts></mrow></math>, <math><mrow><mmultiscripts><mrow><mi>Ge</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>72</mn></mrow></mmultiscripts></mrow></math>, <math><mrow><mmultiscripts><mrow><mi>Ar</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>40</mn></mrow></mmultiscripts></mrow></math>, <math><mrow><mmultiscripts><mrow><mi>Ne</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>20</mn></mrow></mmultiscripts></mrow></math>, and <math><mrow><mmultiscripts><mrow><mi>He</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>4</mn></mrow></mmultiscripts></mrow></math>) that are typically used in the dark matter direct detection. A heavier nucleus actually has the advantage of probing the incoherent scattering of the fermionic absorption dark matter. Observing both the coherent and incoherent contributions would be an important justification of the fermionic dark matter absorption.

Oleg Titov

Incoherent fermionic dark matter absorption with nucleon Fermi motion