各位老师和同学们好，
为加强本单位高能物理核物理及交叉学科等各研究方向研究生相互间的学术交流，拓宽研究生的学术视野，激励青年人才的成长，促进本单位科学研究的发展，第十届粒子所“青年之星”年度学术论坛将于2024年11月20-21日如期举行。期待所有在本年度（2023/11-2024/11）发表或arXived文章（包括实验组文章 paper proposal approved）的在所研究生登台，一展风采。具体的会议活动细节、日程和安排会随后发出。欢迎同学们踊跃参加，具体事项通知如下:
1.论坛邀请粒子所全体师生参加。
2.申请报告需经导师同意，并在会议网站提交报告：
（1）注明博研或硕研身份。
（2）提交报告题目和摘要（中英文不限）。
（3）注明报告关联的已发表论文刊号（期刊或 arXiv 预印本号），论文数量不限。
3.论坛邀请全体博士后参加，汇报年度研究成果，可提交报告，但不参与“青年之星”评选。
4.注册截止时间为11月15日，报告时间暂定15+5分钟。所有参会者将提供中晚餐盒饭和茶歇。
5.论坛组委会将在报告申请中，筛选15--25名报告人。论坛组委会将在论坛期间评选出2024年度“青年之星”，并设立奖项。
粒子物理研究所
夸克与轻子物理教育部重点实验室
夸克物质及探测技术国际联合研究中心
In the high-energy physics, particularly within the context of heavy-ion collisions conducted at the Large Hadron Collider (LHC), there exists a puzzle where viscous hydrodynamics fails to accurately depict the experimental data for the second and third flow harmonics, $v_{2}\{2 \}$ and $v_{3}\{2 \}$, in ultra-central Pb + Pb collisions at 2.76 TeV. This study proposes a novel approach to address this issue by reducing the initial state fluctuations through the augmentation of the minimum inter-nucleon distance within the nucleus. It was observed that increasing this minimum distance resulted in a reduction of the initial eccentricity, as compared to the predictions made by the Woods-Saxon model. Consequently, a lower ratio of shear viscosity to entropy density, $\eta / s$, is necessitated. Employing the TRENTo model, this research calculated the eccentricities within the $0–1 \%$ centrality class and subsequently determined the flow harmonic coefficients $v_2\{2 \}$ and $v_3 \{2\}$ using the (3+1) dimensional viscous hydrodynamics models CLVisc. By comparing various scenarios with different minimum distances between nucleons, this study discovered that a reduction in initial state fluctuations has a substantial impact on resolving the aforementioned puzzle within the nucleus of Pb. This conclusion not only addresses the specific issue of flow harmonic discrepancies but also contributes to a broader understanding of the initial state conditions in heavy-ion collisions. By refining our models to better reflect the true initial conditions, this study enhances the predictive capabilities of hydrodynamic simulations, thereby advancing the field of high-energy physics.
By analyzing the $e^{+}e^{-}$ collision data sample with an integrated luminosity of 8.0 fb$^{-1}$ collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, we perform an amplitude analysis of $D^+\to K_S^0 K_S^0 \pi^+$ for the first time. Our amplitude model contains intermediate decays $D^+ \to K_S^0K^*(892)^+$ and $D^+\to K_S^0 (K_S^0\pi^+)_{\rm s-wave}$. The dominant intermediate process is $D^+\to K_S^0K^*(892)^+$, with a fit fraction of $(97.8 \pm 1.0_{\rm stat.}\pm 0.4_{\rm syst.})\%$, where the first uncertainty is statistical and the second uncertainty is systematic. In addition, with the detection efficiency obtained from the updated generic MC samples generated based on the amplitude analysis results, we obtain the absolute branching fraction of $\displaystyle\mathcal{B}(D^{+}\to K_{S}^{0}K_{S}^{0}\pi^{+}) = (2.97 \pm 0.09_{\rm stat.} \pm 0.05_{\rm syst.})\times 10^{-3}$. Using the branching fraction we measured, we obtain the branching fraction $\displaystyle\mathcal{B}(D^+ \to K_S^0 K^*(892)^+)$ = $(8.72 \pm 0.28_{\rm stat.}\pm 0.15_{\rm syst.})\times10^{-3}$.
In the NνDEx collaboration, a high-pressure gas TPC is being developed to search for the neutrinoless double beta decay. The use of electronegative $^{82}SeF_6$ gas mandates an ion-TPC. The reconstruction of z coordinate is to be realized exploiting the feature of multiple species of charge carriers. As the initial stage of the development, we studied the properties of the $SF_6$ gas, which is non-toxic and has similar molecular structure to $^{82}SeF_6$. In this work we present the measurement of drift velocities and mobilities of the majority and minority negative charge carriers found in SF6 at a pressure of 750 Torr, slightly higher than the local atmospheric pressure. The reduced fields range between 3.0 and 5.5 Td. It was performed using a laser beam to ionize the gas inside a small TPC, with a drift length of 3.7 cm. A customized charge sensitive amplifier was developed to read out the anode signals induced by the slowly drifting ions. The reconstruction of z coordinate using the difference in the velocities of the two carriers was also demonstrated.
The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at centre-of-momentum energy of $\sqrt{s}=13$ TeV collected during the LHC Run 2 data-taking period.
The measurement is performed by combining the measurements of the electromagnetic calorimeter EMCal and the central tracking detectors ITS and TPC, covering a pseudorapidity range of $|\eta^{\gamma}|<0.67$ and a transverse momentum range of $7
The measurement is compared with next-to-leading order perturbative QCD calculations and the results from the ATLAS and CMS experiments as well as with measurements at other collision energies. The measurement and theory prediction are in agreement with each other within the experimental and theoretical uncertainties.
Neutrinoless double beta (0νββ) decay is the most promising way to determine whether neutrinos are Majorana particles. There are many experiments based on different isotopes searching for 0νββ decay. Combining the searches of 0νββ decay in multiple isotopes provides a possible method to distinguish operators and different models. The contributions to 0νββ decay come from standard, long-range, and short-range mechanisms. We analyze the scenario in which the standard and short-range operators exist simultaneously within the framework of low-energy effective field theory. Five specific models are considered, which can realize neutrino mass and can contribute to 0νββ decay via multiple mechanisms. A criterion to evaluate the possibilities of future experiments to discriminate operators and models is built. We find that the complementary searches for 0νββ decay in different isotopes can distinguish the cases that contain the low-energy effective operators O1,2,5 and R-parity violating supersymmetry model. For other cases and models, the experimental searches within multiple isotopes can also more effectively constrain the parameter region than with only one isotope.
In this work, we make a study of the τ− → ωπ−ντ decay in the framework of low energy effective field theory.The JPG decompositions of the quark currents and the ωπ final state show that, besides the Standard Model vector interaction, only the non-standard tensor interaction can have a non-zero contribution to the decay. To discuss its effect, a reliable calculation of the ωπ tensor form factors is necessary. After constructing the Lagrangian of resonance chiral theory with external tensor sources, we calculate both the vector and tensor form factors with the relevant resonance couplings determined by combining the QCD short-distance constraints, the fit to the spectral function of τ− → ωπ−ντ decay, as well as the matching between the O(p4) odd-intrinsic-parity operators after integrating out the vector resonances and the O(p6) operators of chiral perturbation theory. The new physics effect is then investigated in the distributions of the spectral function and the forward-backward asymmetry of τ− → ωπ−ντ decay. We find that the spectral function is dominated by the Standard Model, and the non-standard tensor contribution is negligible. However, since the forward-backward asymmetry can be only generated with a non-zero tensor interaction, the observable is quite sensitive to this kind of new physics. A future measurement of the observable at the Belle II experiment as well as at the proposed Tera-Z and STCF facilities is, therefore, strongly called for to check the existence of such a non-standard tensor interaction.
Abstract: We investigate the chiral phase transition and the properties of the shear viscosity coefficient in a Nambu-Jona-Lasinio (NJL) model at finite temperature and chemical potential. We compare the contributions from the tensor spin polarization (TSP) and anomalous magnetic moment (AMM) of quarks in (2+1)-flavor NJL model. For light $u$ and $d$ quarks, when TSP and AMM are not considered, the magnetized system is characterized by magnetic catalysis. The introduction of TSP will further enhance the magnetic catalytic characteristics. On the other hand, when AMM is introduced, the phase-transition temperature decreases with the magnetic field, which is the feature of inverse magnetic catalysis.It is found that both the ratio $\eta/s$ of shear viscosity coefficient to entropy and the collision relaxation time $\tau$ show similar trend with temperature, both of which reach minima around the critical temperature. The shear viscosity coefficient of the dissipative fluid system can be decomposed into five different components as the strong magnetic field exists. The influences of the order of chiral phase transition and the critical end point on dissipative phenomena in such a magnetized medium are quantitatively investigated. It is found that ${\eta}_{1}$, ${\eta}_{2}$, ${\eta}_{3}$, and ${\eta}_{4}$ all increase with temperature. For first-order phase transitions, ${\eta}_{1}$, ${\eta}_{2}$, ${\eta}_{3}$, and ${\eta}_{4}$ exhibit discontinuous characteristics.
We study the universal dynamical relaxation behaviors of a quantum XY chain following a quench, paying special attention to the case in which the initial state is a critical ground state, or the postquenched Hamiltonian is at a critical point of equilibrium quantum phase transition, or both of them are critical. In such a “critical quench,”we find very interesting real-time dynamical scaling behaviors and we find crossover phenomena between them.For a quench from a noncritical point to a critical point, we find that, compared to the noncritical quench,the universal power-law scaling behavior does not change; however, there may be a crossover between theexponential decaying behavior and the power-law scaling. For a quench from a critical point to a noncritical point, the power-law scaling behaviors $t^{-3/2}$ and $t^{-3/4}$ in the noncritical quenches may be changed to $t^{-1}$ and $t^{-1/2}$, respectively. If the prequenched Hamiltonian is set to be a point that is close to but not exactly at a critical point, we find interesting crossover phenomena between different power-law scaling behaviors. We also study the quench from the vicinity of a multicritical point, we find crossover behaviors that are induced by a different mechanism, and we find another crossover exponent. All the results are related to the gap-closing properties of the energy spectrum of the critical points.
Abstract:
In this study, we explore the thermodynamics of heavy quarkonium within the context of a spinning black hole background. Specifically, we analyze the impact of angular momentum on various thermodynamic properties of heavy quarkonium, including interquark distance, free energy, binding energy, entropy, entropic force, and internal energy, based on the thermodynamic relationships.
Our results demonstrate that angular momentum diminishes the maximum interquark distance,thereby facilitating quarkonium dissociation. Furthermore, we note that angular momentum suppresses free energy. The analysis of binding energy reveals that angular momentum enhances the dissociation of mesons into free quarks and antiquarks. Additionally, our findings indicate that angular momentum augments entropy and entropic force, thereby accelerating quarkonium dissociation. Angular momentum also increases internal energy at extended interquark distances.Lastly,we observe that the effects of angular momentum on quarkonium are more significant when the axis of the quark pair is perpendicular to the direction of angular momentum.
In this talk, we present lattice results for the shear and bulk viscosities of gluon plasma, calculated in SU(3) Yang-Mills theory over the temperature range $0.76T_c \leq T \leq 2.25T_c $, where $T_c$ denotes the confinement/deconfinement transition temperature. Shear viscosity and bulk viscosity quantify the response of the energy-momentum tensor to shear flow and divergent flow, respectively. These viscosities serve as critical input parameters for phenomenological and transport models used to interpret the experimental data, e.g. the elliptic flow $v_2$. Using gradient flow, we achieve unprecedented precision for the temporal Euclidean two-point correlation functions of the energy-momentum tensor, from which the viscosities are extracted. We focus particularly on how the viscosities vary around $T_c$, with the goal of understanding the critical behavior of the pure-glue system. The methodology developed in this work also paves the way for extending the study to full QCD.
自2012年希格斯粒子发现以来，标准模型作为粒子物理理论框架取得了重大成功。然而，标准模型中的粒子仅能解释约4%的宇宙物质成分，而无法解释约25%的不可见物质（即暗物质）的来源，这成为当前粒子物理学的核心挑战之一。此现象表明可能存在超出标准模型的物理理论，其中弱相互作用大质量粒子（WIMP）是一个备受关注的暗物质候选者。假设宇宙起源于大爆炸，实验测量当前暗物质丰度得出 ( \Omega h^2 = 0.12 )。
天体物理观测结果（例如星系旋转曲线和子弹星系团的研究）支持暗物质的存在，并表明其参与引力相互作用，这是目前已知的暗物质唯一已确认的相互作用形式。在高能物理领域，诸多实验正致力于直接探测暗物质的性质，尽管在探索达到GeV量级的较重暗物质方面尚未取得突破。值得注意的是，GeV量级与B介子物理衰变的典型能标相符，并且去年实验首次测得了 ( B^+ \to K^+ \nu \bar{\nu} ) 衰变分支比的中心值，与标准模型的理论预言存在 ( 2.7\sigma ) 的偏差。因此，本研究旨在通过分析B介子衰变过程，探讨与GeV量级暗物质相关的潜在效应，以进一步加深对暗物质性质的理解。
We present the first lattice QCD results of quadratic fluctuations and correlations of conserved charges in (2+1)-flavor lattice QCD in the presence of a background magnetic field. The simulations were performed using the Highly Improved Staggered Quarks with physical pion mass $m_\pi$ = 135 MeV on $N_\tau=8$ and 12 lattices. We find that the correlation between net baryon number and electric charge, denoted as $\chi^{\rm BQ}_{11} $, can serve as a magnetometer of QCD. At pseudocritical temperatures the $\chi^{\rm BQ}_{11}$ starts to increase rapidly with magnetic field strength $eB > 2M^2_{\pi}$ and by a factor 2 at $eB\simeq 8 M^2_{\pi}$.
By comparing with the hadron resonance gas model, we find that the $eB$ dependence of $\chi^{\rm BQ}_{11}$ is mainly due to the doubly charged $\Delta$(1232) baryon. Although the doubly charged $\Delta$(1232) could not be detected experimentally, its decay products, protons and pions, retain the $eB$ dependence of $\Delta$(1232)’s contribution to $\chi^{\rm BQ}_{11}$.
Furthermore, the ratio of electric charge chemical potential to baryon chemical potential, $\mu_{\rm Q}/\mu_{\rm B}$, shows significant dependence on the magnetic field strength and varies with the ratio of electric charge to baryon number in the colliding nuclei in heavy ion collisions. These results provide baselines for effective theory and model studies, and both $\chi^{\rm BQ}_{11}$ and $\mu_{\rm Q}/\mu_{\rm B}$ could be useful probes for the detection of magnetic fields in relativistic heavy ion collision experiments as compared with corresponding results from the hadron resonance gas model.
Recently, there has been great interest in the phenomenon of severe violation of the Wiedemann-Franz law in graphene Dirac fluids around 75 K, due to the strong coupling relativistic plasma near the neutral point, where traditional perturbation theory fails. To explain this phenomenon, this article proposes a holographic dual two-current axion coupling model, describing the interaction between electrons and holes in graphene near the charge neutrality point (CNP) and revealing the related physical mechanism. The study shows that the holographic two-current model aligns with experimental results at 100μm^−2,and correctly predicts conductivity as temperature increases. Additionally, the article explores the behavior of β+γ and its impact on conductivity and thermal conductivity. The results suggest a frictional effect between electrons and holes. Consequently, this study provides us with a clearer understanding of the properties of graphene Dirac fluids and further confirms the reliability of the holographic duality method.
The impact of rotation on the deconfinement phase transition under the Einstein-Maxwell system of the soft and the hard wall models in holographic quantum chromodynamics is studied in this paper. The metric by cylindrical coordinates with rotation is introduced into the system to calculate the Hawking temperature. The first holographic study on the influence of the radius of a homogeneous rotating system on the phase diagram is proposed. It is found that the phase transition temperature hardly changes with the rotation angular velocity for a small rotation radius. Only with a larger rotation radius can the change in rotational angular velocity significantly alter the phase transition temperature. The phase transition temperature decreases rapidly with the increase of rotation angular velocity as the rotation radius increases.
We revisit the holographic Langevin diffusion coefficients of a heavy quark, when travelling through a strongly coupled anisotropic plasma in the presence of magnetic field $\mathcal{B}$.The Langevin diffusion coefficients are calculated within the membrane paradigm in the magnetic branes model which has been extensively studied to investigate the magnetic effects on various observables in strongly coupled QCD scenarios by holography. In addition to confirming some conventional conclusions, we also find several new interesting features among the five Langevin diffusion coefficients in the magnetic anisotropic plasma.
It is observed that the transverse Langevin diffusion coefficients depend more on the direction of motion rather than the directions of momentum diffusion at the ultra-fast limit, while one would find an opposite conclusion when the moving speed is sufficiently low. For the Longitudinal Langevin diffusion coefficient, we find that motion perpendicular to $\mathcal{B}$ affects the Langevin coefficients stronger at any fixed velocity. We should also emphasize that all five Langevin coefficients are becoming larger with increasing velocity. We find that the universal relation $\kappa^{\parallel}>\kappa^{\perp}$ in the isotropic background, is broken in a different new case that a quark moving paralleled to $\mathcal{B}$. This is one more particular example where the violation of the universal relation occurs for the anisotropic background.Further, we find the critical velocity of the violation will become larger with increasing $\mathcal{B}$.
Machine learning has been widely applied in physics research. Although unsupervised learning can extract the critical points of phase transitions, the percolation model remains a challenge. Unsupervised learning using the raw configurations of the percolation model fails to capture the critical points. To capture the configuration characteristics of the percolation model, this paper proposes using the maximum cluster as input to the neural network. It is well understood that the order parameter of the percolation model is not simply the particle density, but rather the probability that a given site or bond belongs to the percolating cluster. Additionally, we introduce the use of a Siamese Neural Network (SNN) to detect percolation phase transitions. Unlike unsupervised dimensionality reduction methods or supervised binary classification outputs, the SNN produces a scalar output referred to as similarity. By combining the maximum cluster and the SNN, we not only successfully extract the critical value of the percolation model, but also calculate the correlation exponent via data collapse. We believe that the SNN has great potential in handling phase transition classification problems and can serve as a reference for studying other phase transition systems.
In recent years, neural networks have increasingly been employed to identify critical points of phase transitions. For the tricritical directed percolation model, its steady-state configurations encompass both first-order and second-order phase transitions. Due to the presence of crossover effects, identifying the critical points of phase transitions becomes challenging. This study utilizes Monte Carlo simulations to obtain steady-state configurations under different probabilities $p$ and $q$, and by calculating the increments in average particle density, we observe first-order transitions, second-order transitions, and regions where both types of transitions interact.These Monte Carlo-generated steady-state configurations are used as input to construct and train a convolutional neural network, from which we determine the critical points $p_{c}$ for different probabilities $q$. Furthermore, by learning the steady-state configurations associated with the superheated point $p=p_u$, we locate the tricritical point at $q_{t}=0.893$. Simultaneously, we employed a three-output CNN model to obtain the phase transition boundaries and the range of the crossover regions. Our method offers a neural network-based approach to capture critical points and distinguish phase transition boundaries, providing a novel solution to this problem.
In this study, we employ a superstatistical approach to construct $q$ exponential and $q$ Maxwell Boltzmann complex networks, generalizing the concept of scale-free networks. By adjusting the crossover parameter $\lambda$, we control the degree of the $q$ exponential plateau at low node degrees, allowing a smooth transition to pure power-law degree distributions. Similarly, the parameter $b$ modulates the $q$ Maxwell Boltzmann curvature, facilitating a shift toward pure power-law networks. This framework introduces a novel perspective for constructing and analyzing scale-free networks. Our results show that these additional degrees of freedom significantly enhance the flexibility of both network types in terms of topological and transport properties, including clustering coefficients, small-world characteristics, and resilience to attacks. Future research will focus on exploring the dynamic properties of these networks, offering promising directions for further investigation.
The QCD critical point is suggested to be in the same universality class as the 3D Ising model, which implies that the behavior of thermodynamic observables near the QCD critical point can be described by the critical exponents and scaling laws of the Ising model. The percolation study offers valuable insights into the characteristics of phase transition, revealing the underlying mechanisms that govern the formation of global connectivity within the system. We explore the percolation phase transition in the 3D cubic Ising model by employing two machine learning techniques. Our results demonstrate the effectiveness of machine learning methods in distinguishing different phases during the percolation transition. Through the finite-size scaling analysis on the output of the neural networks, the percolation temperature and a correlation length exponent in the geometrical percolation transition are extracted and compared to those in the thermal magnetization phase transition within the 3D Ising model. These findings provide valuable insights essential for enhancing our understanding of the QCD phase transition.
Given the untapped potential for continuous improvement of examinations, quantitative investigations of examinations could guide efforts to considerably improve learning efficiency and evaluation and thus greatly help both learners and educators. However, there is a general lack of quantitative methods for investigating examinations. To address this gap, we propose a new metric via complex networks; i.e., the knowledge point network (KPN) of an examination is constructed by representing the knowledge points (concepts, laws, etc.) as nodes and adding links when these points appear in the same question. Then, the topological quantities of KPNs, such as degree, centrality, and community, can be employed to systematically explore the structural properties and evolution of examinations. In this work, 35 physics examinations from the Chinese National College Entrance Examination spanning from 2006 to 2020 were investigated as an evidence. We found that the constructed KPNs are scale-free networks that show strong assortativity and small-world effects in most cases. The communities within the KPNs are obvious, and the key nodes are mainly related to mechanics and electromagnetism. Different question types are related to specific knowledge points, leading to noticeable structural variations in KPNs. Moreover, changes in the KPN topology between examinations administered in different years may offer insights guiding college entrance examination reforms. Based on topological quantities such as the average degree, network density, average clustering coefficient, and network transitivity, the comprehensive difficulty coefficient is proposed to evaluate examination difficulty. All the above results show that our approach can objectively and comprehensively quantify the knowledge structures and examination characteristics. These networks may elucidate comprehensive examination knowledge graphs for educators and guide adjustments and improvements in teaching methodologies.
We present a theoretical study of the medium modifications of the $p_{\rm T}$ balance ($x_{\rm J}$) of dijets in Xe+Xe collisions at $\sqrt{s_{\rm NN}}=5.44$ TeV. The initial production of dijets was carried out using the POWHEG+PYTHIA8 prescription, which matches the next-to-leading-order (NLO) QCD matrix elements with the parton shower (PS) effect. The SHELL model described the in-medium evolution of nucleus-nucleus collisions using a transport approach. The theoretical results of the dijet $x_{\rm J}$ in the Xe+Xe collisions exhibit more imbalanced distributions than those in the p+p collisions, consistent with recently reported ATLAS data. By utilizing the Interleaved Flavor Neutralisation, an infrared-and-collinear-safe jet flavor algorithm, to identify the flavor of the reconstructed jets, we classify dijets processes into three categories: gluon-gluon ($gg$), quark-gluon ($qg$), and quark-quark ($qq$), and investigated the respective medium modification patterns and fraction changes of the $gg$, $qg$, and $qq$ components of the dijet sample in Xe+Xe collisions. It is shown that the increased fraction of $qg$ component at a small $x_{\rm J}$ contributes to the imbalance of the dijet; in particular, the $q_1g_2$ (quark-jet-leading) dijets experience more significant asymmetric energy loss than the $g_1q_2$ (gluon-jet-leading) dijets traversing the QGP. By comparing the $\Delta \langle x_{\rm J}\rangle = \langle x_{\rm J} \rangle_{\rm pp} - \langle x_{\rm J} \rangle_{\rm AA}$ of inclusive, $c\bar{c}$ and $b\bar{b}$ dijets in Xe+Xe collisions, we observe $\Delta \langle x_{\rm J} \rangle_{\rm incl.}>\Delta \langle x_{\rm J} \rangle_{\rm c\bar{c}}>\Delta \langle x_{\rm J} \rangle_{\rm b\bar{b}}$. Moreover, $\rho_{\rm Xe, Pb}$, the ratios of the nuclear modification factors of dijets in Xe+Xe to those in Pb+Pb, were calculated, which indicates that the yield suppression of dijets in Pb+Pb is more pronounced than that in Xe+Xe owing to the larger radius of the lead nucleus.
We present the first theoretical investigation of Fox-Wolfram moments (FWMs) for multi-jet production in relativistic heavy ion collisions. In this work, jet productions in p+p collisions are computed with a Monte Carlo event generator SHERPA, while the Linear Boltzmann Transport model is utilized to simulate the multiple scattering of energetic partons in the hot and dense QCD matter. The event-normalized distributions of the lower-order FWM, $H_1^T$ in p+p and Pb+Pb collisions are calculated. It is found that for events with jet number $n_\text{jet} = 2$ the $H_1^T$ distribution in Pb+Pb is suppressed at small $H_1^T$ while enhanced at large $H_1^T$ region as compared to p+p. For events with $n_\text{jet}>2$, the jet number reduction effect due to jet quenching in the QGP decreases the $H_1^T$ distribution at large $H_1^T$ in Pb+Pb relative to p+p. The medium modification of the Fox-Wolfram moment $H_1^T$ for events with $n_\text{jet}\ge 2$ are also presented, which resemble those of events with $n_\text{jet} = 2$. Its reason is revealed through the relative contribution fractions of events with different final-state jet numbers to $H_1^T$
二维（2D）喷注层析技术是研究高能重离子碰撞中，喷注介质修正效应的一种工具。它结合了梯度（在本文中表现为横向）和纵向的喷注层析，用于选择横平面内不同初始喷注产生位置的喷注事件。它利用了夸克-胶子等离子体（QGP）的横向梯度和喷注路径长度的横向不对称性和能量损失的特性。在本研究中，我们采用二维喷注层析技术，结合描述喷注部分子在QGP介质中传播的线性玻尔兹曼输运（LBT）模型，研究了光子标记喷注的喷注形状受到的介质修正效应。我们的结果表明，横向不对称度（$A_N^y$）较小或 光子-喷注横动量不平衡性（$x_{J\gamma}=p_T^{\rm jet}/p_T^\gamma$）较小的喷注，其对应的喷注形状比$A_N^y$或$x_{J\gamma}$较大的喷注更加展宽，这是因为前者在QGP的中心产生并有着更长的传输路径，而后者的产生位置则偏离中心并靠近QGP火球表面。对于$A_N^y$不为零的事件，喷注形状相对于事件平面是不对称的，我们发现，喷注核心的硬部分子在$\hat{q}$梯度的驱动下被偏转到远离致密区域的方向，而来自介质响应的大角度软部分子则更多地产生在QGP的致密区域。
我们对旋转Myers-Perry黑洞中的全息Schwinger效应进行了势分析。通过计算附着在AdS空间中D3膜探针上弦的经典作用量，我们计算了产生的粒子对之间的势能。我们发现，增加角动量会减少势垒，从而增强Schwinger效应，这与之前通过局部洛伦兹变换得到的结果一致。另外我们还发现这些效应在粒子对位于横向平面时比沿纵向方向时更为明显。此外，我们还讨论了在强耦合下，随着角动量的影响，Schwinger效应如何随着剪切粘度与熵密度比的变化而变化。
We study the CP asymmetries of the rare top-quark decays $t \to c \gamma$ and $t \to cg$ in the aligned two-Higgs-doublet model (A2HDM), which is generically characterized by new sources of CP violation beyond the Standard Model (SM). Specifically, the branching ratios and CP asymmetries of these rare top-quark decays are explicitly formulated, with an emphasis on the origins of weak and strong phases in the A2HDM. Taking into account the most relevant constraints on this model, we evaluate the variations of these observables with respect to the model parameters. It is found that the branching ratios of $t \to c \gamma$ and $t \to cg$ decays can maximally reach up to $1.47\times10^{-10}$ and $4.86\times10^{-9}$ respectively, which are about four and three orders of magnitude higher than the corresponding SM predictions. While the branching ratios are almost independent of the relative phase $\varphi$ between the two alignment parameters $\varsigma_u$ and $\varsigma_d$ within the allowed parameter space, the CP asymmetries are found to be very sensitive to $\varphi$. When the two alignment parameters are complex with a non-zero $\varphi$ varied within the range $[50^\circ,150^\circ]$, the magnitudes of the CP asymmetries can be significantly enhanced relative to both the SM and the real case. In particular, the maximum absolute values of the CP asymmetries can even reach up to $\mathcal{O}(1)$ for these two decay modes, in the range $\varphi \in [70^\circ,100^\circ]$. These interesting observations could be utilized to discriminate the SM and the different scenarios of the A2HDM.
We study the influence of a rotation on the string tension and the temperature of the confinement-deconfinement transition of gluodynamics by gauge/gravity duality. We explore two distinct approaches, global and local transformations, to introduce rotation and compare the results. It is shown that the string tension extracted from the free energy in the presence of a heavy quarkonium decreases with increasing angular velocity, while the transition temperature determined by the Polyakov loop increases with increasing angular velocity, which is in line with lattice simulations.
The functional renormalization group (FRG) is a non-perturbative method that considers quantum and thermal fluctuations. Using the FRG flow equations, the critical region of the two-flavor quark-meson model in a finite isospin chemical potential with omega and rho vector mesons interactions is investigated in this work. We also use the traditional mean-field method to calculate the phase diagram in the chiral limit for comparison. The results show that the influences of the omega meson and rho meson on the phase structure are quite different. The existence of the isospin chemical potential also causes significant changes in the phase structure
In high-energy heavy-ion collisions, jets traverse the quark-gluon plasma (QGP) and deposit energy into the medium, leading to jet-induced medium response. The medium response takes the form of Mach-cone-like excitations and can modify the internal structure of the jet, affecting many observables, such as jet shape and jet fragmentation function and so on. However, Simulation of jet-induced medium response requires not only a complete model that can accurately describe the evolution of hard and soft partons concurrently, but also substantial computational resources for full-scale simulations. In this study, we trained a generative neural network using a flow model with gamma jet events from Pb $+$ Pb collisions of centrality $0-10\%$ at 5.02 TeV to estimate the final-state effects of jet-induced medium response. Our findings indicate that with only the initial jet information—namely, the energy-momentum of gamma and the jet, along with their initial positions—the network can accurately predict the positions of the front wake and diffusion wake, and maintain the particle spectrum within the same order of magnitude as the actual data.
疼痛是一个重要的全球健康问题。当前的治疗方案在有效性和副作用等方面都存在缺陷，特别是一些治疗疼痛药物的不恰当使用会导致上瘾的风险，因此迫切需要改进疼痛治疗方法或者开发新药。随着人工智能技术的快速发展，机器学习算法在药物分子虚拟筛选方面具有广泛的应用。其中一个重要的应用是分子特征提取，即从分子的简化分子线性输入规范字符串 (SMILES) 中提取重要的分子结构信息从而进行分子属性预测，之后本研究根据疼痛的靶点钠离子通道，构建与钠离子通道相关的蛋白质-蛋白质相互作用网络，筛选 111 个抑制剂数据集，通过深度学习算法进行治疗疼痛化合物分子筛选，评估药物分子的 ADMET 特性（吸收、分布、代谢、排泄和毒性），确定最佳先导化合物。
In high-energy physics, accurately predicting cross sections of reaction processes relies heavily on the parton fragmentation functions (FFs). Conventional methods often require parameterized forms and additional calculations to ensure the FFs conform to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations, which can be cumbersome and may not fully capture the complexity of FFs across varying energy scales. Here, we introduce a novel approach to determining parton fragmentation functions using a Physics Informed Neural Network (PINN). Unlike traditional methods, our approach does not require prior parameterized forms and directly integrates the DGLAP evolution equations into the neural network architecture, allowing the FFs to automatically satisfy these equations without additional calculations. We present new sets of parton FFs obtained for hadrons in electron-positron annihilation processes at next-to-leading order (NLO) in pQCD using this innovative technique. To validate our approach, we calculate proton-(anti)proton hadron spectra using the extracted FFs and demonstrate that our theoretical predictions align well with experimental data across various energy scales ($\sqrt{s}$ = 130, 200, 500, 630, 900, 1800, 2760, 5020, 5440, 7000 GeV). Our findings indicate that the PINN method not only simplifies the extraction process but also enhances the universal applicability of FFs across different energy scales. By eliminating the need for parameterized forms and additional DGLAP evolution, our approach represents a significant step forward in the field, paving the way for more robust and versatile predictions in high-energy physics, including the potential exploration of new research avenues in heavy ion collisions.