Based on a machine learning holographic QCD model, we construct a systematical framework to investigate the properties of the scalar glueballs continuously from zero temperature to finite temperature. By using both the quasinormal frequencies and the spectral functions, we extract the pole masses, thermal widths, screening masses and dispersion relation of the scalar glueballs in hot medium. It is shown that the pole masses almost remain the vacuum values at temperatures far below the critical temperature <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>c</mi></msub></math>, and then decrease with the increasing of temperature until a temperature lower than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>c</mi></msub></math>. This result qualitatively agrees with earlier lattice simulations. While the pole masses increase monotonically above the critical temperature <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>c</mi></msub></math>, which agrees with recent lattice calculation. Meanwhile, it is shown that the thermal widths increase monotonically with temperature, which also agrees with the near <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>c</mi></msub></math> lattice simulations. The screening mass exhibits a similar temperature-dependent behavior to the pole mass, while the dispersion relation increasingly deviates from the relativistic one as the temperature rises. It is interesting to note that we obtain the imaginary corrections in the thermal correlators, which contains both the temperal and spatial information and might be helpful for the four-dimensional calculations. Furthermore, by comparing the quasinormal modes and the spectral functions, we note that it requires more careful analysis when applying the spectral functions in studying thermal hadrons from holography, since there could be other types of quasinormal modes which are not related with bound states while they may contribute to the peaks of the spectral functions.

China

Ruixiang Chen

Danning Li

Mei Huang

Thermal properties of the scalar glueballs from holography

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 study dynamical properties of strongly coupled chiral matter by using the holographic method. We demonstrate, at both linear and nonlinear levels, that perturbations on thermodynamically unstable backgrounds within the spinodal region of chiral first-order phase transitions exhibit dynamic instability. The corresponding magnitude of dynamic instability can be characterized by the critical momentum. Furthermore, we found that, within a certain temperature range, the quasinormal-mode spectrum contains purely imaginary diffusive modes. As spatial momentum increases, a transition occurs in the system’s long-time dynamics. The dominant contribution shifts from diffusive mode to propagating mode. When the diffusive mode becomes dominant, the spectral function exhibits a transport peak structure in the low-frequency region. A heuristic argument suggests that this particular transition can be related to the chiral symmetry breaking and restoration.

Pei Zheng

Yidian Chen

Yu-xin Liu

Dynamical instability and transport peak of chiral matter from holography

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)

The observation of a resonance structure in the opening angle of the electron-positron pairs in the $$^{7}$$ Li(p,e $$^+$$ e $$^-$$ ) $$^{8}$$ Be reaction was claimed and interpreted as the production and subsequent decay of a hypothetical particle (X17). Similar excesses, consistent with this particle, were later observed in processes involving $$^{4}$$ He and $$^{12}$$ C nuclei with the same experimental technique. The MEG II apparatus at PSI, designed to search for the $$\mu ^+ \rightarrow \textrm{e}^+ \gamma $$ decay, can be exploited to investigate the existence of this particle and study its nature. Protons from a Cockroft–Walton accelerator, with an energy up to 1.1 MeV, were delivered on a dedicated Li-based target. The $$\gamma $$ and the e $$^{+}$$ e $$^{-}$$ pair emerging from the $$^8\textrm{Be}^*$$ transitions were studied with calorimeters and a spectrometer, featuring a broader angular acceptance than previous experiments. We present in this paper the analysis of a four-week data-taking in 2023 with a beam energy of 1080 keV, resulting in the excitation of two different resonances with Q-value 17.6 and 18.1 MeV. No significant signal was found, and limits at 90% C.L. on the branching ratios (relative to the $$\gamma $$ emission) of the two resonances to X17 were set, $$R_{17.6} <{1.8}\,\times \,10^{-6}$$ and $$R_{18.1} < {1.2}\,\times \,10^{-5}$$ in the mass range between $${16.5}\hbox { MeV}/\hbox {c}^{2}$$ and $${17.1}\hbox { MeV}/\hbox {c}^{2}$$ .

Russia

K. Afanaciev

Italy

A. Baldini

Japan

S. Ban

H. Benmansour

G. Boca

P. Cattaneo

G. Cavoto

F. Cei

M. Chiappini

A. Corvaglia

Switzerland

G. Maso

A. Bari

M. Gerone

L. Barusso

M. Francesconi

L. Galli

G. Gallucci

F. Gatti

L. Gerritzen

F. Grancagnolo

E. Grandoni

M. Grassi

D. Grigoriev

M. Hildebrandt

United Kingdom

F. Ignatov

F. Ikeda

T. Iwamoto

S. Karpov

P. Kettle

N. Khomutov

A. Kolesnikov

N. Kravchuk

V. Krylov

N. Kuchinskiy

F. Leonetti

W. Li

V. Malyshev

A. Matsushita

M. Meucci

S. Mihara

W. Molzon

T. Mori

D. Nicolò

H. Nishiguchi

A. Ochi

W. Ootani

A. Oya

D. Palo

M. Panareo

A. Papa

V. Pettinacci

A. Popov

F. Renga

S. Ritt

M. Rossella

A. Rozhdestvensky

S. Scarpellini

P. Schwendimann

G. Signorelli

M. Takahashi

Y. Uchiyama

A. Venturini

B. Vitali

C. Voena

K. Yamamoto

R. Yokota

T. Yonemoto

Search for the X17 particle in $$^{7}\textrm{Li}(\textrm{p},\textrm{e}^+ \textrm{e}^{-}) ^{8}\textrm{Be}$$ processes with the MEG II detector

By using the holographic approach, we investigate the interplay between the order parameter and Goldstone modes in the real-time dynamics of the chiral phase transition. By quenching the system to a different thermal bath and obtaining different kinds of initial states, we solve the real-time evolution of the system and find that an additional prethermalization stage emerges at non-critical temperature after introducing the Goldstone modes. Some basic properties related to this additional prethermalization stage have been discussed in detail. More interestingly, an additional scaling relation is observed, indicating the appearance of a non-thermal fixed point in the dynamical region.

Yuxin Liu

Non-equilibrium dynamics of Goldstone excitation from holography

The jet quenching parameter and energy loss of light and heavy quarks have been investigated in the framework of holographic quantum chromodynamics (QCD) models with a critical end point (CEP) at finite baryon chemical potential in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>f</mi></msub><mo>=</mo><mn>2</mn><mo>,</mo><mn>2</mn><mo>+</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>+</mo><mn>1</mn><mo>+</mo><mn>1</mn></math> systems. The properties of the jet quenching parameter and energy loss around phase boundary have been carefully studied. It is found that the dimensionless jet quenching parameter and the energy loss of light and heavy quarks exhibit evident features around the phase boundary. Specifically, all these quantities increase rapidly near the CEP phase transition temperature <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mrow><mi>CEP</mi></mrow></msub></math> with fixed <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mrow><mi>CEP</mi></mrow></msub></math>. Moreover, the velocity dependent behavior of heavy quark energy loss differs significantly from charged particle energy loss in quantum electrodynamics (QED) matter. For electromagnetic interaction, the energy loss of charged particle can be described by the Bethe-Bloch formula and the Lindhand-Scharff-Schiott theory at low and high velocities, respectively. However, the heavy quark energy loss at CEP is approximately proportional to velocity at low velocities and aligns with Bjorken’s results at high velocities, which indicates that the heavy quark energy loss is predominantly collisional at low velocities and gluon radiation dominant at high velocities. For light quark energy loss, the behavior of the energy loss per unit length and the total energy loss differs significantly. However, the total energy loss and stopping distance exhibit similar behavior. This implies that the stopping distance predominantly determines the total energy loss. Thus, even with increased energy loss per unit length at higher temperatures or chemical potentials, the total energy loss decreases due to the reduced stopping distance.

Zhibin Li

Jet quenching and quark energy loss from holographic QCD

The properties of quantum chromodynamics (QCD) matter at finite isospin densities are investigated employing holographic hard-wall and soft-wall anti–de Sitter (AdS)/QCD models. It is confirmed that at high enough isospin densities, charged pions start to condense and the pion superfluid phase appears in the system. It is shown that the chiral condensate and the pion condensate can be transformed to each other and form a chiral circle in the superfluid phase. We derived the equation of state (EoS) for pionic matter, calculated the normalized trace anomaly <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mi>ε</mi><mo>−</mo><mn>3</mn><mi>p</mi><mo stretchy="false">)</mo><mo>/</mo><msubsup><mi>m</mi><mi>π</mi><mn>4</mn></msubsup></math>, and analyzed the sound speed and adiabatic index. Additionally, we provided data on the mass-radius relation and tidal deformability of pion stars. The results indicate that the holographic models align well with lattice QCD concerning isospin density, axial-vector condensation, EoS, and trace anomaly, though discrepancies in sound speed and adiabatic index emerge at higher isospin chemical potentials. The holographic models closely match the leading-order results from chiral perturbation theory (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mi>PT</mi></math>) in certain observables, suggesting that they may effectively capture aspects of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mi>PT</mi></math> dynamics within a five-dimensional framework under the probe approximation.

Mingshan Ding

Iran

Kazem Bitaghsir Fadafan

Pion condensation and pion star from holographic QCD

We investigate Λ production in the ( <math altimg='si146.svg'><msup><mrow><mi>&#960;</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math>, <math altimg='si3.svg'><msup><mrow><mi>K</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math>) reaction on a 6Li target at <math altimg='si4.svg'><msub><mrow><mi>p</mi></mrow><mrow><msup><mrow><mi>&#960;</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1.05</mn></math> GeV/ <italic>c</italic>, using the distorted-wave impulse approximation (DWIA) with the Fermi-averaged <math altimg='si5.svg'><msup><mrow><mi>&#960;</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup><mi>n</mi><mo stretchy='false'>&#8594;</mo><msup><mrow><mi>K</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup><mi mathvariant='normal'>&#923;</mi></math> amplitudes. The calculated spectrum is in good agreement with the experimental data, suggesting that <math altimg='si1.svg'><mmultiscripts><mrow><mi mathvariant='normal'>He</mi></mrow><mprescripts /><mrow><mi mathvariant='normal'>&#923;</mi></mrow><mrow><mn>4</mn></mrow></mmultiscripts></math>- <italic>d</italic> configurations play a key role in describing the &#923; continuum states of <math altimg='si23.svg'><msubsup><mrow /><mrow><mi mathvariant='normal'>&#923;</mi></mrow><mrow><mn>6</mn></mrow></msubsup></math>Li near and above the <math altimg='si8.svg'><mmultiscripts><mrow><mi mathvariant='normal'>He</mi></mrow><mprescripts /><none /><mrow><mn>3</mn></mrow></mmultiscripts><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>d</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi mathvariant='normal'>&#923;</mi></math> threshold. Our analysis shows that the <math altimg='si1.svg'><mmultiscripts><mrow><mi mathvariant='normal'>He</mi></mrow><mprescripts /><mrow><mi mathvariant='normal'>&#923;</mi></mrow><mrow><mn>4</mn></mrow></mmultiscripts></math> hypernucleus as a hyperfragment is prominently produced through <italic>D</italic>-wave resonances with <math altimg='si9.svg'><msup><mrow><mi>J</mi></mrow><mrow><mi>P</mi></mrow></msup><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msup><mrow><mn>3</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math>, <math altimg='si10.svg'><msup><mrow><mn>2</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math>, and <math altimg='si11.svg'><msup><mrow><mn>1</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math> in the <math altimg='si108.svg'><mmultiscripts><mrow><mi mathvariant='normal'>He</mi></mrow><mprescripts /><mrow><mi mathvariant='normal'>&#923;</mi></mrow><mrow><mn>4</mn></mrow></mmultiscripts><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>d</mi></math> channel at a large momentum transfer <math altimg='si13.svg'><mi>q</mi><mo>&#8771;</mo><mn>360</mn></math>&#8211;400 MeV/ <italic>c</italic>. These findings provide theoretical evidence for the production of a <math altimg='si1.svg'><mmultiscripts><mrow><mi mathvariant='normal'>He</mi></mrow><mprescripts /><mrow><mi mathvariant='normal'>&#923;</mi></mrow><mrow><mn>4</mn></mrow></mmultiscripts></math> hyperfragment via a cluster-like mechanism in the 6Li( <math altimg='si146.svg'><msup><mrow><mi>&#960;</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math>, <math altimg='si3.svg'><msup><mrow><mi>K</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math>) reaction.

Toru Harada

Yoshiharu Hirabayashi

Evidence for <math altimg='si1.svg'><mmultiscripts><mrow><mi mathvariant='normal'>He</mi></mrow><mprescripts /><mrow><mi mathvariant='normal'>&#923;</mi></mrow><mrow><mn>4</mn></mrow></mmultiscripts></math> hyperfragment production in the 6Li( <italic>&#960;</italic> +, <italic>K</italic> +) reaction

The ultralight dark photon is an intriguing dark matter candidate. The interaction between visible and dark photons is introduced by the gauge kinetic mixing between the field strength tensors of the Abelian gauge groups in the Standard Model and dark sector. Relativistic electrodynamics was generalized to quantum electromagnetodynamics (QEMD) in the presence of both electric and magnetic charges. The photon is described by two four-potentials corresponding to two $ U(1) $ gauge groups and satisfying non-trivial commutation relations. In this work, we construct low-energy dark photon-photon interactions in the QEMD framework and obtain new dark photon-photon kinetic mixings. Then, we derive the consequent field and Maxwell's equations. We also investigate the detection strategies of dark photons as light dark matter and generic kinetic mixings at haloscope experiments.

Chang-Jie Dai

Tong Li

Rui-Jia Zhang

Dark photon dark matter in quantum electromagnetodynamics and detection at haloscope experiments * Li Tong is supported by the National Natural Science Foundation of China (12375096, 12035008, 11975129)