Within the framework of Dyson-Schwinger equations (DSEs) and by means of the Multiple Reflection Expansion approximation, we study the finite volume effects on the constituent quark mass in a strong external magnetic field. Since the magnetic field influences the coupling constant, which controls the strength of strong interactions in QCD, we adopt the magnetic-field-dependent running coupling constant in our simulations. The results show that, in addition to the magnetic field, the masses of constituent quarks also have a significant dependence on the volume and the running coupling constant. The model behaves closely to the infinite volume limit for large sizes, but the effect of the finite volume is significant when the system size $\textit{R}$ is about $ 2-6 $ fm. The finite volume effects and the magnetic-field-dependent running coupling constant have considerable influence on the phase transition.

China

Li-Juan Zhou

De-Xian Wei

Zhong-Yi Liu

Hong-Wei Zhong

Dynamical quark mass and finite volume effects in the Dyson-Schwinger equations * Li-Juan Zhou has been supported by the National Natural Science Foundation of China (11865005), the Natural Science Foundation of Guangxi (China) (2025GXNSFAA069552). De-Xian Wei has been supported by the National Natural Science Foundation of China (12105057), the Natural Science Foundation of Guangxi (China) (2023GXNSFAA026020)

We report an experimental investigation of an unexplored breakup pathway of 6Li proceeding via one-proton stripping to the unbound 5He nucleus, followed by its decay into <math altimg='si22.svg'><mrow><mi>&#945;</mi><mo linebreak='goodbreak'>+</mo><mi>n</mi></mrow></math>, in the 6Li + 112Sn reaction at <math altimg='si3.svg'><mrow><msub><mi>E</mi><mrow><mrow><mi mathvariant='normal'>b</mi></mrow><mi>e</mi><mi>a</mi><mi>m</mi></mrow></msub><mo linebreak='goodbreak'>=</mo><mn>30</mn></mrow></math> MeV. Coincident <italic>&#945;</italic>- <italic>n</italic> events were measured using an array of silicon strip telescopes in conjunction with liquid scintillator neutron detectors. Successive kinematical cuts on the reconstructed projectile-like, fragment energies and Q-values enabled a clear separation of contributions arising purely through 5He <math altimg='si6.svg'><mrow><mo>&#8594;</mo><mi>&#945;</mi><mo linebreak='goodbreak'>+</mo><mi>n</mi></mrow></math> from competing processes such as evaporation following complete and incomplete fusion. The resultant relative energy distributions exhibit a pronounced peak at 0.84 MeV, indicating sequential breakup through the first unbound resonance 5He(3/2 <math altimg='si23.svg'><msup><mrow /><mo>&#8722;</mo></msup></math>) and show good agreement with Monte-Carlo simulations. Absolute breakup cross-sections for the ( 6Li, 5He&#8239;&#8594;&#8239; <italic>&#945;n</italic>) channel are determined using the efficiency-corrected yields. In addition, angular distributions for elastic scattering and breakup cross sections are interpreted within coupled-channels (CDCC+CRC) framework. The present results provide valuable insight into transfer-induced breakup dynamics of weakly bound nuclei near the Coulomb barrier.

India

Tanya Singh

S. Santra

P.C. Rout

A. Pal

A. Baishya

H. Kumawat

T. Santhosh

M. Meher

Jyotisankar Das

Ramandeep Gandhi

Sequential breakup of 6Li via ( 6Li, 5He <math altimg='si6.svg'><mrow><mo>&#8594;</mo><mi>&#945;</mi><mo linebreak='goodbreak'>+</mo><mi>n</mi></mrow></math>) reaction

A wide range of scintillating bolometers are under investigation for applications in the search for rare events and processes beyond the Standard Model. In this work, we report the first measurement of a natural, non-molybdenum-doped, lithium tungstate (Li $$_2$$ WO $$_4$$ ) crystal operated underground as a scintillating cryogenic calorimeter. The detector achieved a baseline energy resolution of 0.5 keV RMS with a low-energy threshold of about 1.5 keV. The simultaneous readout of heat and light enabled particle identification, revealing a clear separation between $$\beta /\gamma ,$$ $$\alpha ,$$ and nuclear recoil populations above 300 keV, with a light-yield-based particle discrimination better than $$6\sigma .$$ These results, fully comparable with those achieved with other compounds in the field, demonstrate that Li $$_2$$ WO $$_4$$ is a promising candidate for rare-event searches. In particular, the combination of excellent radio-purity (with U/Th levels below 0.5 mBq/kg) and sensitivity to neutron interactions via the $$^6$$ Li(n, $$\alpha )$$ $$^3$$ H reaction makes this material an attractive option for next-generation experiments in dark matter, coherent elastic neutrino-nucleus scattering, and spin-dependent interactions.

Italy

D. Helis

A. Melchiorre

S. Nagorny

Switzerland

M. Noia

L. Pagnanini

S. Pirro

A. Puiu

G. Benato

P. Carniti

R. Elleboro

P. Gambacorta

C. Gotti

Russia

V. Grigorieva

S. Nisi

France

E. Olivieri

G. Pessina

S. Piacentini

Kazakhstan

M. Shafiee

V. Shlegel

Characterization of the Li $$_2$$ WO $$_4$$ crystal as a cryogenic scintillating calorimeter

The competition between the breakup channels in the 6Li + 209Bi fusion reaction at the above-barrier energies has been investigated using a classical dynamic model. By incorporating the breakup processes from the short-lived nucleus formed via direct excitation and <italic>n</italic>-stripping, the model provides a comprehensive description of both complete and incomplete fusion cross sections. Although the <italic>n</italic>-stripping channel exhibits a higher probability, it contributes less to the complete fusion cross section compared to the direct excitation channel. An unexpected behavior was observed in incomplete fusion at the above barrier energies: the light-fragment capture predominantly occurs near the critical angular momentum, while the <italic>&#945;</italic> capture is favored at lower angular momenta, particularly in cases with large mass asymmetry between the two fragments. These findings provide further insight into the origin of fusion suppression in reactions involving weakly bound nuclei.

Kai-Xuan Cheng

Chun-Wang Ma

Mechanism of breakup channel competition in the 6Li+ 209Bi system at above-barrier energies

The 2HDM+S is the singlet extension of the two-Higgs-doublet model (2HDM). The singlet field and its mixing with the 2HDM Higgs sector lead to new contributions to the electroweak precision observables, in particular, the oblique parameters. In this study, we performed a systematic investigation of the impacts of each mixing angle on the oblique parameters. We adopted the mixing angles and physical Higgs masses as our parameters, which allow a mapping when a specific symmetry structure of the Higgs potential and various theoretical considerations are taken into account. We identified five benchmark cases, where at most one mixing angle was nonzero, and analyzed the 95% C.L. allowed parameter space using the oblique parameters. In the alignment limit of the 2HDM, we find that, other than the usual mass relations of $m_H\sim m_{H^\pm}$ or $m_A\sim m_{H^\pm}$ , electroweak precision measurements also impose an upper limit on the neutral Higgs masses. In the cases with nonzero singlet mixing with the 2HDM Higgses $\textit{H}$ or $\textit{A}$, we find approximate mass relations of $c^2_{\alpha_{HS}} m_{H} + s^2_{\alpha_{HS}}m_{h_S} = m_{H^\pm}$ or $c^2_{\alpha_{AS}} m_{A} + s^2_{\alpha_{AS}}m_{A_S} = m_{H^\pm}$ . These relations are universal to the 2HDM+S models, with or without further symmetry assumption. We also studied the non-alignment limit of the 2HDM+S, which typically has tighter constraints on the masses and mixing angles. Finally, we examined the complementarity between the electroweak precision analyses and the Higgs coupling precision measurements.

Cheng Li

Juxiang Li

Shufang Su

Wei Su

Electroweak precision constraints of the 2HDM+S * Cheng Li, Juxiang Li, and Wei Su are supported by the Natural Science Foundation of China (NSFC) (12305115), Shenzhen Science and Technology Program (202206193000001, 20220816094256002), Guangdong Provincial Key Laboratory of Gamma-Gamma Collider and Its Comprehensive Applications (2024KSYS001), and Guangdong Provincial Key Laboratory of Advanced Particle Detection Technology (2024B1212010005). Juxiang Li is also supported by the Fundamental Research Funds for the Central Universities, and the Sun Yat-sen University Science Foundation. Shufang Su is supported by the Department of Energy (DEFG02-13ER41976/DE-SC0009913)

Electroweak (EW) amplitudes in the gauge-Goldstone five-component formalism have a distinctive property: gauge symmetry is imprinted in the amplitudes, manifested as the massive Ward identity (MWI) $ k^M{\cal{M}}_M=0 $ . In this study, we used the HELAS package to numerically study gauge symmetry in EW amplitudes. First, we directly tested gauge symmetry by examining the MWI of amplitudes. Second, we modified the couplings within a vertex and among vertices to check if and how the MWI changes. Third, we tested gauge symmetry by considering the couplings modified by operators from the standard model effective field theory (SMEFT). Similar to the standard model, there are relations between different couplings that are protected by gauge symmetry. We observed that, if we modify the couplings to deviate from the relations, the MWI is violated. In contrast, the MWI is restored when the relations between couplings reduce to those in the SMEFT.

Wang-Fa Li

Junmou Chen

Qian-Jiu Wang

Zhao-Huan Yu

Numerical study on the gauge symmetry of electroweak amplitudes * Junmou Chen is supported by National Natural Science Foundation of China (12205118), Wang-Fa Li, Qian-Jiu Wang, and Zhao-Huan Yu are supported by the Guangzhou Science and Technology Planning Project (2024A04J4026)

We investigate the alpha-decay width of a near proton-threshold resonance in 11B by the excitation functions of 7Li( <italic>&#945;, &#945;</italic>) and 7Li( <italic>&#945;, &#945;</italic>&#8217;) reactions. This resonance is an example of loosely bound atomic nuclei, understood as small open quantum systems, that exhibit properties significantly influenced by their coupling to the continuum. The present experiment focuses on the formation of a specific state in 11B at excitation energy in the region near 11.4 MeV by bombarding a 7Li target with a 4He beam at energies ranging from 3.92 to 4.56 MeV in the laboratory frame. The study provides data complementary to previous observations of the proton emission in the <italic>&#946;</italic>-decay of the neutron-rich halo nucleus 11Be. An R-matrix fit to the data provides resonance energy and partial widths consistent with <italic>J&#960;</italic>= <math altimg='si1.svg'><mrow><mn>1</mn><mo linebreak='goodbreak'>/</mo><msup><mn>2</mn><mo>+</mo></msup></mrow></math> for a narrow near-threshold state in 11B at 11.400(20) MeV, that is 171(20) keV above the proton emission threshold, with partial <italic>&#945;</italic>-decay width &#915; <inf><italic>&#945;</italic></inf>=2.5 <math altimg='si10.svg'><msubsup><mrow /><mrow><mo>&#8722;</mo><mn>1.5</mn></mrow><mrow><mo>+</mo><mn>3.5</mn></mrow></msubsup></math> keV in elastic scattering and &#915; <inf><italic>&#945;</italic>'</inf>=15.8 <math altimg='si11.svg'><msubsup><mrow /><mrow><mo>&#8722;</mo><mn>0.4</mn></mrow><mrow><mo>+</mo><mn>1.9</mn></mrow></msubsup></math> keV in inelastic scattering. These findings contribute to the understanding of the structure of this open quantum system resonance.

United States

T. Tang

W. Mittig

Spain

Y. Ayyad

C. Hebborn

J.J. Kolata

P. O’Malley

T. Ahn

D. Bazin

M. Couder

A. Muñoz-Ramos

K. Manukyan

Z. Maschuq

J.S. Randhawa

N. Rijal

G.H. Sargsyan

W.W. von Seeger

Alpha-decay width of a near proton-threshold resonance in the 7Li( <italic>&#945;, &#945;</italic>) channel

We develop a theoretical framework for the production of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> pairs through the decay of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> mesons produced from a thermal background, based on the Nambu-Jona-Lasinio (NJL) model. The differential production rate of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> is related to the self-energy of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> meson, incorporating the contributions of the quark loop at leading order and the kaon loop at next-to-leading order in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mo>/</mo><msub><mi>N</mi><mi>c</mi></msub></math> expansion. We numerically evaluate the invariant mass spectrum of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> pair both in vacuum and at finite temperature. The inclusion of the kaon loop results in a finite width of the spectrum, improving agreement with experimental data. We also investigate the spin alignment of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> meson induced by its motion relative to the thermal background. In the NJL model with only chiral condensates, we find that deviations from the unpolarized limit of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mo>/</mo><mn>3</mn></mrow></math> are negligible.

Germany

Xin-Nan Zhu

Xin-Li Sheng

Defu Hou

Production of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> pairs through the decay of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> mesons

We study $ \cos2\phi $ azimuthal asymmetry in doubly longitudinally polarized proton-proton Drell-Yan collisions within the transverse momentum dependent factorization framework. The asymmetry arises from the convolution of the longitudinal transversity distribution $ h_{1L}^{\perp} $ for both protons. Using the Bacchetta-Delcarro-Pisano-Radici-Signori parameterization for the nonperturbative Sudakov form factor and the Wandzura-Wilczek approximation for collinear $ h_{1L}^{\perp} $ , we predict the double spin asymmetry $ A_{LL}^{\cos2\phi} $ at RHIC and NICA kinematics. Our results demonstrate sensitivity to sea quark distributions, with the asymmetry reaching up to 25% for maximal sea quark contributions. These predictions highlight the potential of polarized Drell-Yan measurements to probe sea quark dynamics and advance our understanding of nucleon structures.

Hui Li

Ting Hu

Liang-Liang Liu

Xiao-Yu Wang

Zhun Lu

Asymmetry ${{\boldsymbol A}_{\boldsymbol{LL}}^{\bf\cos2\boldsymbol\phi}} $ in the polarized proton-proton Drell-Yan process within TMD factorization * Hui Li is supported by Fundamental Research Program of Shanxi Province (202203021222224) and Natural Science Foundation of Shanxi Normal University (JCYJ2023021). Xiao-Yu Wang is supported by the Natural Science Foundation of Henan Province (242300421377, 232300421140)

We derive expressions for the vector and tensor components of the spin polarization of massive vector bosons at local thermodynamic equilibrium up to second order in the space-time gradients of the thermodynamic fields pertaining to the canonical stress-energy tensor and spin tensor of the free Proca field. A set of Feynman rules is devised to calculate the Wigner function and the matrix-valued spin-dependent distribution (MVSD) functions order by order in space-time gradients. Due to constraints imposed by time-reversal symmetry, the leading contribution to spin alignment — defined as the 00-component of the tensor polarization — arises from second-order terms in MVSD, for which we provide an analytic formula. We discuss the physical meaning of different contributions to vector and tensor polarization. These formulae provide a prediction of a contribution to the spin alignment which can be compared with the observations in relativistic heavy-ion collisions.

Zhong-Hua Zhang

Xu-Guang Huang

Francesco Becattini

Vector and tensor spin polarization for vector bosons at local equilibrium