The neutrino mass generation via conventional seesaw mechanism is realized at high scales around <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mn>14</mn></msup><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> with natural Yukawa couplings of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>O</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>, making the test of the neutrino seesaw a great challenge. It is intriguing to note that the neutrino seesaw scale is typically around the upper range of the cosmological inflation scale. In this work, we propose a new framework incorporating inflation and the neutrino seesaw in which the inflaton primarily decays into right-handed neutrinos after inflation. This decay process is governed by the inflaton interaction with the right-handed neutrinos that respects the shift symmetry. Through the neutrino seesaw mechanism, fluctuations of the Higgs field can modulate the inflaton decays and contribute to the curvature perturbation. We investigate the induced non-Gaussian signatures and demonstrate, for the first time, that such signatures provide an important means to directly probe the high scale of natural neutrino seesaw. We further analyze the interplay of the non-Gaussianity signatures with the low-energy neutrino experiments, and their interplay with the Higgs self-coupling measurements at the LHC and future colliders.

China

Jingtao You

Linghao Song

Hong-Jian He

South Korea

Chengcheng Han

Cosmological non-Gaussianity from the neutrino seesaw mechanism

The tiny neutrino masses are most naturally explained by seesaw mechanism through singlet right-handed neutrinos, which can further explain the matter-antimatter asymmetry in the Universe. In this work, we propose a new approach to study cosmological signatures of neutrino seesaw through the interaction between inflaton and right-handed neutrinos, which respects the shift symmetry. In our framework, after inflation the inflaton predominantly decays into right-handed neutrinos and its decay rate is modulated by the fluctuations of the Higgs field, which act as the source of curvature perturbations. This gives a new realization of Higgs modulated reheating, and it produces primordial non-Gaussian signatures that can be measured by the forthcoming large-scale structure surveys. We demonstrate, for the first time, that the measurements of non-Gaussianity by these surveys can probe the neutrino seesaw scale and have the potential to constrain a large portion of the seesaw parameter space, opening up a new window for directly testing the high-scale seesaw mechanism.

Cosmological signatures of neutrino seesaw mechanism

We present a model-independent extraction of the $$\phi $$ – $$^{4}\textrm{He}$$ scattering length from near-threshold $$\phi $$ photoproduction on helium-4, based on LEPS Collaboration data for the coherent process $$\gamma + {}^{4}\textrm{He} \rightarrow \phi + {}^{4}\textrm{He}$$ and the Vector Meson Dominance framework. Assuming an energy-independent differential cross section, we extract the absolute value of the $$\phi -^4\!\textrm{He}$$ scattering length $$|\alpha _{\phi ^{4}\textrm{He}}| = (3.33 \pm 0.06) \times 10^{-4}~\textrm{fm}$$ from a fit at threshold $$t_{\text {thr}}$$ . This value is orders of magnitude smaller than those for $$\phi N$$ and $$\phi d$$ scattering length, indicating an inverse dependence of $$|\alpha _{VA}|$$ on the target nucleus mass. Our results provide new insight into the $$\phi $$ –nucleus interaction, supporting the notion of weak $$\phi $$ –nucleus coupling. We further explore the dependence of $$|\alpha _{VA}|$$ on the vector meson mass, the target atom mass, and the threshold energy. An approximate exponential suppression of $$|\alpha _{VA}|$$ is observed with increasing vector meson mass or target atom mass, indicating that heavier vector mesons or heavier target nuclei exhibit weaker couplings in vector meson–nucleus interactions.

Chengdong Han

Wei Kou

Rong Wang

Xurong Chen

First extraction of the $$\phi $$ - $$^{4}\textrm{He}$$ scattering length from near-threshold $$\phi $$ photoproduction on helium-4

We discuss the landscape of flavor physics at the Circular Electron-Positron Collider (CEPC), based on the nominal luminosity outlined in its Technical Design Report. The CEPC is designed to operate in multiple modes to address a variety of tasks. At the $\textit{Z}$ pole, the expected production of 4 Tera $\textit{Z}$ bosons will provide unique and highly precise measurements of $\textit{Z}$ boson couplings, while the substantial number of boosted heavy-flavored quarks and leptons produced in clean $\textit{Z}$ decays will facilitate investigations into their flavor physics with unprecedented precision. We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models. Our studies indicate that, with its highlighted advantages and anticipated excellent detector performance, the CEPC can explore beauty and $\textit{τ}$ physics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments, potentially enabling the detection of new physics at energy scales of 10 TeV and above. This potential also extends to the observation of yet-to-be-discovered rare and exotic processes, as well as testing fundamental principles such as lepton flavor universality, lepton and baryon number conservation, etc., making the CEPC a vibrant platform for flavor physics research. The $\textit{WW}$ threshold scan, Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard, especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements, and Flavor-Changing-Neutral-Current physics of Higgs boson and top quarks. We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals. The role of machine learning for innovative detector design and advanced reconstruction algorithms is also stressed. The CEPC flavor physics program not only develops new capabilities for exploring flavor physics beyond existing projects but also enriches the physics opportunities of this machine. It should be remarked that, given the richness of the CEPC flavor physics, this manuscript is not meant to be a comprehensive survey, but rather an investigation of representative cases. Uncovering the full potential of flavor physics at the CEPC will require further dedicated explorations in the future.

Xiaocong Ai

United States

Wolfgang Altmannshofer

Peter Athron

Xiaozhi Bai

Lorenzo Calibbi

Germany

Lu Cao

Yuzhi Che

Chunhui Chen

Ji-Yuan Chen

Long Chen

Mingshui Chen

Shanzhen Chen

Xuan Chen

Shan Cheng

Cheng-Wei Chiang

Switzerland

Andreas Crivellin

Hanhua Cui

France

Olivier Deschamps

Sébastien Descotes-Genon

Xiaokang Du

Shuangshi Fang

Yu Gao

Yuanning Gao

Li-Sheng Geng

Pablo Goldenzweig

Jiayin Gu

Feng-Kun Guo

Yuchen Guo

Zhi-Hui Guo

Tao Han

Jibo He

Miao He

Xiaogang He

Yanping Huang

Gino Isidori

Quan Ji

Jianfeng Jiang

Xu-Hui Jiang

Slovenia

Jernej F. Kamenik

Tsz Hong Kwok

Gang Li

Geng Li

Haibo Li

Haitao Li

Hengne Li

Honglei Li

Liang Li

Lingfeng Li

Qiang Li

Shu Li

Xiaomei Li

Xin-Qiang Li

Yiming Li

Yubo Li

Yuji Li

Zhao Li

Hao Liang

Zhijun Liang

Libo Liao

Zoltan Ligeti

Jia Liu

Jianbei Liu

Tao Liu

Yi Liu

Yong Liu

Zhen Liu

Xinchou Lou

Peng-Cheng Lu

Italy

Alberto Lusiani

Hong-Hao Ma

Kai Ma

Farvah Mahmoudi

Yajun Mao

Yaxian Mao

David Marzocca

Juan-Juan Niu

Soeren Prell

Huirong Qi

Sen Qian

Zhuoni Qian

Qin Qin

Ariel Rock

Jonathan L. Rosner

Manqi Ruan

Dingyu Shao

Chengping Shen

Xiaoyan Shen

Haoyu Shi

United Kingdom

Liaoshan Shi

Zong-Guo Si

Cristian Sierra

Huayang Song

Shufang Su

Wei Su

Zhijia Sun

Michele Tammaro

Dayong Wang

En Wang

Flavor physics at the CEPC: a general perspective * We acknowledge financial support from the National Natural Science Foundation of China (NSFC) (12125507, 12047503, 12035008, 2211530479, 12475094, 12135006, 12075097, 12375086, 2022YFA1601903, 12061141007, 12375091, 12342502, 12235018, 12335003, 12105100, 12475106, 11961141015, 12188102, 12175245, 12205171, 12321005, tsqn202312052, 2024HWYQ-005, 12405121, 12447167, 12061141006, 12405102, 12125503,12305115, 12075213, 12335005, 12235008); the Chinese Academy of Sciences (YSBR-101, XDB34030000); the National Key R&D Program of China (2022YFE0116900, 2023YFA1606703, 2022YFA1601901); the National Key Research and Development Program of China (2023YFA1606300); the Excellent Postdoctoral Program of Jiangsu Province (2023ZB891); the Shenzhen Science and Technology Program (202206193000001, 20220816094256002); the Natural Science Foundation for Distinguished Young Scholars of Henan Province (242300421046); the Beijing Municipal Natural Science Foundation (JQ22002); the Area of Excellence (AoE/P-404/18-3) and the General Research Fund (16304321) (both grants are issued by the Research Grants Council of Hong Kong S.A.R); the MOST National Key R&D Program (2023YFA1606303); the Shanghai Key Laboratory for Particle Physics and Cosmology, Key Laboratory for Particle Astrophysics and Cosmology (Ministry of Education), Shanghai Jiao Tong University

Inclusive electron scattering at carefully chosen kinematics can isolate scattering from the high-momentum nucleons in short-range correlations (SRCs). SRCs are produced by the hard, short-distance interactions of nucleons in the nucleus, and because the two-nucleon (2N) SRCs arise from the same N-N interaction in all nuclei, the cross section in the SRC-dominated regime is identical up to an overall scaling factor. This scaling behavior has been used to identify SRC dominance and to measure the contribution of SRCs in a wide range of nuclei. We examine this scaling behavior over a range of momentum transfers using new data on 2H, 3H, and 3He, and find an expanded scaling region compared to heavy nuclei. Motivated by this improved scaling, we examine the 3H and 3He data in kinematics where three-nucleon SRCs may play an important role. The data for the largest struck nucleon momenta are consistent with isolation of scattering from three-nucleon SRCs, and suggest that the very highest momentum nucleons in 3He have a nearly isospin-independent momentum configuration.

S. Li

S.N. Santiesteban

J. Arrington

R. Cruz-Torres

L. Kurbany

D. Abrams

Saudi Arabia

S. Alsalmi

Croatia

D. Androic

K. Aniol

T. Averett

C. Ayerbe Gayoso

J. Bane

S. Barcus

J. Barrow

A. Beck

V. Bellini

H. Bhatt

D. Bhetuwal

D. Biswas

D. Bulumulla

A. Camsonne

J. Castellanos

J. Chen

J.P. Chen

D. Chrisman

M.E. Christy

C. Clarke

S. Covrig

K. Craycraft

D. Day

D. Dutta

E. Fuchey

C. Gal

F. Garibaldi

T.N. Gautam

Japan

T. Gogami

J. Gomez

P. Guèye

A. Habarakada

T.J. Hague

J.O. Hansen

F. Hauenstein

W. Henry

D.W. Higinbotham

R.J. Holt

C.E. Hyde

K. Itabashi

M. Kaneta

A. Karki

A.T. Katramatou

C.E. Keppel

M. Khachatryan

V. Khachatryan

P.M. King

Israel

I. Korover

T. Kutz

N. Lashley-Colthirst

W.B. Li

H. Liu

N. Liyanage

E. Long

Canada

J. Mammei

P. Markowitz

R.E. McClellan

F. Meddi

D. Meekins

S. Mey-Tal Beck

R. Michaels

M. Mihovilovič

A. Moyer

S. Nagao

V. Nelyubin

Inclusive studies of two- and three-nucleon short-range correlations in 3H and 3He