Very recently, the LHCb Collaboration reported the doubly charmed tetraquark state $T_{cc}^{+}$ below the $D^{*+}{D}^0$ threshold about 273 keV. As a very near-threshold state, its long-distance structure is very important. In the molecular scheme, we relate the coupling constants of $T_{cc}^{+}$ with $D^{*0}{D}^{+}$ and $D^{*+}{D}^0$ to its binding energy and mixing angle of two components with a coupled-channel effective field theory. With the coupling constants, we investigate the kinetically allowed strong decays $T_{cc}^{+}\to D^0{D}^0{\pi }^{+}$, $T_{cc}^{+}\to D^{+}{D}^0{\pi }^0$ and radiative decays $D^{+}{D}^0\gamma$. Our results show that the decay width of $T_{cc}^{+}\to D^0{D}^0{\pi }^{+}$ is the largest one, which is just the experimental observation channel. Our theoretical total strong and radiative widths are in favor of the $T_{cc}^{+}$ as a $|D^{*+}{D}^0⟩$ dominated bound state. The total strong and radiative width in the single channel limit and isospin singlet limit are given as ${59.7}_{-4.4}^{+4.6}\mathrm{keV}$ and ${46.7}_{-2.9}^{+2.7}\mathrm{keV}$, respectively. Our calculation is cutoff-independent and without prior isospin assignment. The absolute partial widths and ratios of the different decay channels can be used to test the structure of $T_{cc}^{+}$ state when the updated experimental results are available.

We have explored the multicomponent structure of electrical conductivity of relativistic Fermionic and bosonic fluid in the presence of a magnetic field by using the Kubo approach. This is done by explicitly evaluating the thermomagnetic vector current spectral functions using the real time formalism of finite temperature field theory and the Schwinger proper time formalism. In the absence of a magnetic field, the one-loop diagramatic representation of the Kubo expression of any transport coefficients is exactly the same with a relaxation time approximation (RTA)-based expression, but this equality does not hold for a finite magnetic field picture due to a lack of proper implementation of quantum effect in a latter approach. We have shown this discrepancy for a particular transport coefficient—electrical conductivity, whose starting point in the Kubo approach will be an electromagnetic current-current correlator and its one-loop skeleton diagram carrying two scalar/Dirac propagators for a scalar/Dirac fluid. Through a numerical comparison between RTA and Kubo expressions of conductivity components (parallel and perpendicular), we have attempted to interpret a detailed quantum field theoretical effect, contained by the Kubo expression but not by the RTA expression. In a classical RTA expression we get a magnetic field independent parallel conductivity due to zero Lorentz force but in the field theoretical Kubo expression, it decreases and increases with the magnetic field for a scalar and Dirac medium, respectively, due to the Landau quantization effect. This parallel component of conductivity can be interpreted as a zero momentum limit of quantum fluctuation with the same Landau level internal lines, while for a perpendicular component of conductivity, fluctuation with Landau level differences $\pm 1$ are noticed, which might be a new realization of transportation in a field theoretical sector.

Three-loop counterterms for the Standard Model (SM) revealed that the matrix of anomalous dimensions ($\gamma$) of quarks is divergent in the $d\to 4$ limit unless a carefully chosen non-Hermitian square-root of the $Z$ matrix is used in the textbook formula for $\gamma$. Here, an alternative prescription is given, which expresses $\gamma$ and $\beta$ functions directly in terms of counterterms (instead of $\sqrt{Z}$ and conventional ‘bare couplings’) and produces finite results. In the SM, this prescription reproduces results obtained previously by adjusting $\sqrt{Z}$.

We study the evolution of the matter-antimatter asymmetry $(\eta )$, the vorticity, and the hypermagnetic field in the symmetric phase of the early Universe, and in the temperature range $100\mathrm{GeV}\le T\le 10\mathrm{TeV}$. We assume a configuration for the hypermagnetic field which includes both helical and nonhelical $(B_z)$ components. Consequently, the hypermagnetic field and the fluid vorticity can directly affect each other, the manifestations of which we explore in three scenarios. In the first scenario, we show that in the presence of a small vorticity and a large ${\eta }_{e_R}$, helicity can be generated and amplified for an initially strong $B_z$. The generation of the helical seed is due to the chiral vortical effect and/or the advection term, while its growth is mainly due to the chiral magnetic effect which leads to the production of the baryon asymmetry, as well. The vorticity saturates to a nonzero value which depends on $B_z$, even in the presence of the viscosity, due to the backreaction of $B_z$ on the plasma. Increasing the initial vorticity, makes the values of the helicity, $\eta$’s, and vorticity reach their saturation curves sooner, but does not change their final values at the onset of the electroweak phase transition. The second scenario is similar to the first except we assume that all initial $\eta$’s are zero. We find that much higher initial vorticity is required for the generation process and, while the values of $\eta$’s do not reach their saturation curves, final $\eta$’s of order ${10}^{-9}$ are possible. In the third scenario, we show that in the presence of only a strong hypermagnetic field, $\eta$’s and vorticity can be generated and amplified. Increasing the initial helicity increases the final$\eta$’s and vorticity. Although the values of $\eta$’s do not reach their saturation curves, final values of order ${10}^{-7}$ are possible. We find that although the presence of a nonzero initial $B_z$ is necessary in all three scenarios, its increase only increases the final values of vorticity.

In this work, we report on a theoretical study of possible pentaquark states ${\mathrm{\Lambda }}_b^0(5912)$ and ${\mathrm{\Lambda }}_b^0(5920)$ in the $\gamma p\to {\mathrm{\Lambda }}_b^{0(*)}{B}^{+}$ reactions within an effective Lagrangian approach. In addition to the contributions from the $s$-channel nucleon pole and $t$-channel ${\overline{B}}^{*-}$ exchange, the contact term contribution is also included. Our theoretical approach is based on the chiral unitary theory where the ${\mathrm{\Lambda }}_b^0(5912)$ and ${\mathrm{\Lambda }}_b^0(5920)$ resonances are dynamically generated. Within the coupling constants of the ${\mathrm{\Lambda }}_b^0(5912)$ and ${\mathrm{\Lambda }}_b^0(5920)$ to $\overline{B}p$ and ${\overline{B}}^{*}p$ channels obtained from chiral unitary theory, the total and differential cross sections of the $\gamma p\to {\mathrm{\Lambda }}_b^{0(*)}{B}^{+}$ are evaluated. Our calculation indicates that the cross section for $\gamma p\to {\mathrm{\Lambda }}_b^0(5912)B^{+}$ and $\gamma p\to {\mathrm{\Lambda }}_b^0(5920)B^{+}$ reactions are of the order of 0.0164 and 0.00527 nb, respectively. If measured in future experiments, such as the Electron-Ion Collider in China or the United States, then the predicted total cross sections and specific features of the angular distributions can be used to test the (molecular) nature of the ${\mathrm{\Lambda }}_b^0(5912)$ and ${\mathrm{\Lambda }}_b^0(5920)$ that they may be pentaquark states.

Machine learning techniques are becoming an integral component of data analysis in high energy physics. These tools provide a significant improvement in sensitivity over traditional analyses by exploiting subtle patterns in high-dimensional feature spaces. These subtle patterns may not be well modeled by the simulations used for training machine learning methods, resulting in an enhanced sensitivity to systematic uncertainties. Contrary to the traditional wisdom of constructing an analysis strategy that is invariant to systematic uncertainties, we study the use of a classifier that is fully aware of uncertainties and their corresponding nuisance parameters. We show that this dependence can actually enhance the sensitivity to parameters of interest. Studies are performed using a synthetic Gaussian dataset as well as a more realistic high energy physics dataset based on Higgs boson decays to tau leptons. For both cases, we show that the uncertainty aware approach can achieve a better sensitivity than alternative machine learning strategies.

In this paper we derived in QCD the Balitsky-Fadin-Kuraev-Lipatov (BFKL) linear, inhomogeneous equation for the factorial moments of multiplicity distribution ($M_k$) from Le-Mueller-Munier equation. In particular, the equation for the average multiplicity of the color-singlet dipoles ($N$) turns out to be the homogeneous BFKL while $M_k\propto N^k$ at small $x$. Second, using the diffusion approximation for the BFKL kernel we show that the factorial moments are equal to $M_k=k!N{(N-1)}^{k-1}$ which leads to the multiplicity distribution $\frac{{\sigma }_n}{{\sigma }_{\text{in}}}=\frac{1}{N}{(\frac{N-1}{N})}^{n-1}$. We also suggest a procedure for finding corrections to this multiplicity distribution which will be useful for descriptions of the experimental data.

Dark matter (DM) may be comprised of axionlike particles (ALPs) with couplings to photons and the standard model fermions. In this paper, we study photon signals arising from cosmic ray (CR) electron scattering on background ALPs. For a range of masses we find that these bounds can place competitive new constraints on the ALP-electron coupling, although in many models lifetime constraints may supersede these bounds. In addition to current Fermi constraints, we also consider future e-Astrogram bounds which will have greater sensitivity to ALP-CR induced gamma-rays.

We construct a procedure to separate boosted Higgs bosons decaying into hadrons, from the background due to strong interactions. We employ the Lund jet plane to obtain a theoretically well-motivated representation of the jets of interest and we use the resulting images as the input to a convolutional neural network classifier. In particular, we consider two different decay modes of the Higgs boson, namely into a pair of bottom quarks or into light jets, against the respective backgrounds. For each case, we consider both a moderate- and high- boost scenario. The performance of the tagger is compared to what is achieved using a traditional single-variable analysis which exploits a QCD inspired color-singlet tagger, namely the jet color ring observable.

We consider gauged U(1) extensions of the standard model of particle physics with three right-handed sterile neutrinos and a singlet scalar. The neutrinos obtain mass via the type I seesaw mechanism. We compute the one-loop corrections to the elements of the tree-level mass matrix of the light neutrinos and show explicitly the cancellation of the gauge-dependent terms. We present a general formula for the gauge-independent, finite one-loop corrections for arbitrary number new U(1) groups, new complex scalars, and sterile neutrinos. We estimate the size of the corrections relative to the tree-level mass matrix in a particular extension, the superweak model.

Spectra with full towers of levels are expected due to the quantization of the string vibrations; however, different theoretical models exist for the excitation spectra. First principle computations are important to test the different models and to search for novel phenomena, but so far, only a few excited states of QCD flux tubes have been studied with pure gauge SU(3) lattice QCD in $3+1$ dimensions. We thus aim to study a spectrum of flux tubes with static quark and antiquark sources up to a significant number of excitations. We specialize on the spectrum of the most symmetric case, namely ${\mathrm{\Sigma }}_g^{+}$, where up to two levels are already published in the literature. To achieve the highest possible excitation level, we construct a large set of operators with the correct symmetry, solve the generalized eigenvalue problem, and compare the results of different lattice QCD gauge actions with different lattice spacings and anisotropies.

Within the framework of the massive $\mathrm{O}(N)$ nonlinear sigma model extended to the next-to-leading order in the chiral counting [for $N=3$ corresponding to the two(-quark)-flavor Chiral Perturbation Theory], we calculate the relativistic six-pion scattering amplitude at low energy up to and including terms $\mathcal{O}(p^4)$. Results for the pion mass, decay constant, and four-pion amplitude in the case of $N$ (meson) flavors at $\mathcal{O}(p^4)$ are also presented.

In this work, we perform a combined analysis to the measured data of the cross section of open-strange processes $e^{+}{e}^{-}\to K^{+}{K}^{-}$, $e^{+}{e}^{-}\to K{\overline{K}}^{*}+\mathrm{c}.\mathrm{c}.$, $e^{+}{e}^{-}\to K^{*+}{K}^{*-}$, $e^{+}{e}^{-}\to K_1(1270{)}^{+}{K}^{-}$, $e^{+}{e}^{-}\to K_1(1400{)}^{+}{K}^{-}$, $e^{+}{e}^{-}\to K_2^{*}(1430)\overline{K}+\mathrm{c}.\mathrm{c}.$, and $e^{+}{e}^{-}\to K(1460{)}^{+}{K}^{-}$ with the support of study of hadron spectroscopy. We reveal the contribution of the possible light vector mesons around 2 GeV to reproduce the cross section data of the reported open-strange processes from $e^{+}{e}^{-}$ annihilation which may provide a new perspective to construct the light vector meson family and understand the $Y(2175)$.

In the paper, the inclusive production of heavy quarkonium ${\eta }_Q$ ($Q=b$ or $c$) via $Z$ boson decays within the framework of nonrelativistic QCD effective theory are studied. The contributions from the leading color-singlet and color-octet Fock states are considered. Total and differential decay widths for the inclusive decays $Z\to {\eta }_Q+X$ are presented. It is found that the decays $Z\to {\eta }_Q+X$ are dominated by the ${{}^{3}S}_1^{[8]}$ component, so the decays can be inversely adopted to determine the values of the long-distance matrix elements $⟨{\mathcal{O}}^{{\eta }_c}({{}^{3}S}_1^{[8]})⟩$ and $⟨{\mathcal{O}}^{{\eta }_b}({{}^{3}S}_1^{[8]})⟩$, respectively. Our numerical results show that at an $e^{+}{e}^{-}$ collider running at the $Z$ pole with a high luminosity around $10^{35}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ (a super $Z$ factory), there are about $4.5\times {10}^7$ ${\eta }_c$ meson events and $6.1\times {10}^5$ ${\eta }_b$ meson events to be produced per operation year, and the inclusive decays may be used for clarifying some problems on the heavy quarkonium ${\eta }_Q$ and nonrelativistic QCD.

Spin Hall effect (SHE) is the generation of spin current due to an electric field, and has been observed in a variety of materials. In this work, we use linear response theory to verify that the analogous spin Hall current can be induced by chemical potential and temperature gradient, both of which are present in hot and dense nuclear matter created in heavy-ion collisions. We propose to measure “directed spin flow”, the first Fourier coefficients of local spin polarization of $\mathrm{\Lambda }$ $(\overline{\mathrm{\Lambda }})$ hyperon, at central collisions to probe spin Hall current in heavy-ion collision experiments. We benchmark the magnitude of the induced “directed spin flow” at two representatively collisions energies, namely ${\sqrt{s}}_{NN}=200\mathrm{GeV}$ and ${\sqrt{s}}_{NN}=19.6\mathrm{GeV}$, by employing a phenomenologically motivated freeze-out prescription. At both beam energies, the resulting “directed spin flow” ranges from ${10}^{-4}$ to ${10}^{-3}$, and is very sensitive to the rapidity.

We study the heavy quark production processes with the transverse momentum dependent (unintegrated) gluon distribution function in a proton which is obtained recently using the Kimber-Martin-Ryskin prescription from the Bessel-inspired behavior of parton densities at small Bjorken $x$ values. Our results agree with the latest HERA experimental data for reduced cross sections ${\sigma }_{\mathrm{red}}^{c\overline{c}}(x,Q^2)$ and ${\sigma }_{\mathrm{red}}^{b\overline{b}}(x,Q^2)$, and also for deep inelastic structure functions $F_2^c(x,Q^2)$ and $F_2^b(x,Q^2)$ in a wide range of $x$ and $Q^2$ values. Comparisons with the predictions based on the Ciafaloni-Catani-Fiorani-Marchesini evolution equation and with the results of conventional pQCD calculations performed at the first three orders of perturbative expansion are presented.

What happens to the QCD vacuum when a time-periodic circularly polarized laser field with a sufficiently large intensity and frequency is applied? Based on the Floquet formalism for periodically driven systems and the systematic low-energy effective theory of QCD, we show that for a sufficiently large frequency and above a critical intensity, the QCD vacuum is unstable against the chiral soliton lattice of pions; a crystalline structure of topological solitons that spontaneously breaks parity and continuous translational symmetries. Our work would pave the way for novel “Floquet vacuum engineering.”

The leading-logarithmic (LL) gluon Sudakov form factor is derived from rapidity-ordered Balitsky-Fadin-Kuraev-Lipatov evolution with longitudinal-momentum conservation. This derivation further clarifies the relation between high-energy and transverse-momentum-dependent factorizations and can be extended beyond the LL approximation as well.

A symmetry-preserving treatment of mesons, within a Dyson-Schwinger and Bethe-Salpeter equations approach, demands an interconnection between the kernels of the quark gap equation and meson Bethe-Salpeter equation. Appealing to those symmetries expressed by the vector and axial-vector Ward-Green-Takahashi identitiges (WGTI), we construct a two-body Bethe-Salpeter kernel and study its implications in the vector channel; particularly, we analyze the structure of the quark-photon vertex, which explicitly develops a vector meson pole in the timelike axis and the quark anomlaous magnetic moment term, as well as a variety of $\rho$ meson properties: mass and decay constants, electromagnetic form factors, and valence-quark distribution amplitudes.