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The Analytical Solutions of Equatorial Geodesic Motion in Kerr Spacetime
Yan Liu, Bing Sun
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The study of Kerr geodesics has a long history, particularly for those occurring within the equatorial plane, which is generally well-understood. However, upon comparison with the classification introduced by one of us [Phys. Rev. D 105, 024075 (2022)], it becomes apparent that certain classes of geodesics, such as trapped orbits, are still lacking analytical solutions. Thus, in this study, we provide explicit analytical solutions for equatorial timelike geodesics in Kerr spacetime, including solutions of trapped orbits, which capture the characteristics of special geodesics, such as the positions and conserved quantities of circular orbits, bound orbits, and deflecting orbits. Specifically, we determine the precise location at which retrograde orbits undergo a transition from counter-rotating to prograde motion due to the strong gravitational effects near the rotating black hole. Interestingly, we observe that for orbits with negative energy, the trajectory remains prograde despite the negative angular momentum. Furthermore, we investigate the intriguing phenomenon of deflecting orbits exhibiting an increased number of revolutions around the black hole as the turning point approaches the turning point of the trapped orbit. Additionally, we find that only prograde marginal deflecting geodesics are capable of traversing through the ergoregion. In summary, our findings present explicit solutions for equatorial timelike geodesics and offer insights into the dynamics of particle motion in the vicinity of a rotating black hole.
Pair of dyon production near the magnetized dyonic Reissner-Nordstrom black holes
Haryanto M. Siahaan
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We investigate the phenomenon of pair production of massive scalar particles with magnetic charge near the horizon of a magnetized dyonic Reissner-Nordstrom black hole. The intrinsic symmetry between electric and magnetic quantities in the Einstein-Maxwell equations suggests that the pair can be generated through both Hawking radiation and the Schwinger effect, provided that the Dirac quantization condition is satisfied.
One-loop contributions for ${\boldsymbol h \bf\rightarrow \boldsymbol\ell \bar{\boldsymbol\ell}\gamma}$ and ${{\boldsymbol e}^{\bf -}{\boldsymbol e}^{\bf +}\bf\rightarrow {\boldsymbol h\gamma}}$ in ${{\boldsymbol U}{\bf (1)}_{{\boldsymbol B}{\bf -}{\boldsymbol L}}}$ extension of the standard model
Tran Dzung Tri, Thanh Huy Nguyen, Khiem Hong Phan
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We present one-loop contributing for \begin{document}$ h\rightarrow \ell \bar{\ell}\gamma $\end{document} with \begin{document}$ \ell =\nu_{e, \mu, \tau}, e, \mu $\end{document} and \begin{document}$ e^-e^+\rightarrow h\gamma $\end{document} in \begin{document}$ U(1)_{B-L} $\end{document} extension of the standard models. In phenomenological results, the signal strengths for \begin{document}$ h\rightarrow \ell \bar{\ell}\gamma $\end{document} at Large Hadron Collider and for \begin{document}$ e^-e^+\rightarrow h\gamma $\end{document} at future Lepton Colliders are analyzed in physical parameter space for both vector and chiral \begin{document}$ B-L $\end{document} models. We find that the contributions from neutral gauge boson \begin{document}$ Z' $\end{document} to the signal strengths are rather small. Consequently, the effects are hard to probe at future colliders. While the impacts of charged Higgs, CP-odd Higgs in the chiral \begin{document}$ B-L $\end{document} model on the signal strengths are significant and can be measured with the help of the initial polarization beams at future lepton colliders.
Searching for the light leptophilic gauge boson Zx via four-lepton final states at the CEPC
Chong-Xing Yue, Yan-Yu Li, Mei-Shu-Yu Wang, Xin-Meng Zhang
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We investigate the possibility of detecting the leptophilic gauge boson \begin{document}$ Z_x $\end{document} predicted by the \begin{document}$ U(1)_{L_e-L_\mu} $\end{document} model via the processes \begin{document}$ e^+e^-\rightarrow \ell^+\ell^-Z_x(Z_x\rightarrow \ell^+\ell^-) $\end{document} and \begin{document}$ e^+e^-\rightarrow \ell^+\ell^-Z_x(Z_x\rightarrow \nu_\ell\bar{\nu_\ell}) $\end{document} at the Circular Electron Positron Collider (CEPC) with the center of mass energy \begin{document}$ \sqrt s=240 $\end{document} GeV and the luminosity \begin{document}$ \mathcal{L}=5.6 \;\; \mathrm{ab^{-1}} $\end{document}. We give the expected sensitivities of the CEPC to the parameter space at \begin{document}$ 1\sigma $\end{document}, \begin{document}$ 2\sigma $\end{document}, \begin{document}$ 3\sigma $\end{document} and \begin{document}$ 5\sigma $\end{document} levels.
The production of charmonium pentaquark from b-baryon and B-meson decay: SU(3) analysis
Wei-Hao Han, Ye Xing, Ji Xu
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In this paper, we study the production of charmonium pentaquark \begin{document}$ c \bar c q q q $\end{document} from bottom baryon and B-meson decays under the flavor SU(3) symmetry. Decay amplitudes for various processes are parametrized in terms of the SU(3) irreducible nonperturbative amplitudes. A number of relations between decay widths have been deduced. Moreover, the strong decays of pentaquark is also taken into account. These results can be tested in future measurements at LHCb, Belle II and CEPC. Once a few decay branching fractions have been measured, our work could provide hints for exploring new decay channels or new pentaquark states.
Efficient parameter inference for gravitational wave signals in the presence of transient noises using temporal and time-spectral fusion normalizing flow
Tian-Yang Sun, Chun-Yu Xiong, Shang-Jie Jin, Yu-Xin Wang, Jing-Fei Zhang, Xin Zhang
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Glitches represent a category of non-Gaussian and transient noise that frequently intersects with gravitational wave (GW) signals, exerting a notable impact on the processing of GW data. The inference of GW parameters, crucial for GW astronomy research, is particularly susceptible to such interference. In this study, we pioneer the utilization of temporal and time-spectral fusion normalizing flow for likelihood-free inference of GW parameters, seamlessly integrating the high temporal resolution of the time domain with the frequency separation characteristics of both time and frequency domains. Remarkably, our findings indicate that the accuracy of this inference method is comparable to traditional non-glitch sampling techniques. Furthermore, our approach exhibits greater efficiency, boasting processing times on the order of milliseconds. In conclusion, the application of normalizing flow emerges as pivotal in handling GW signals affected by transient noises, offering a promising avenue for enhancing the field of GW astronomy research.
Strong decays of the Pc(4312) and its isospin cousin via the QCD sum rules
Xiu-Wu Wang, Zhi-Gang Wang
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In the present work, considering the conservation of isospin in the strong decays, we investigate the strong decays of the pentaquark molecule candidate \begin{document}$ P_c(4312) $\end{document} and its possible higher isospin cousin \begin{document}$ P_c(4330) $\end{document} in the framework of the QCD sum rules. What's more, the pole residue of the Δ baryon with isospin eigenstate \begin{document}$ |II_3\rangle=|\frac{3}{2}\frac{1}{2}\rangle $\end{document} is obtained. If the possible pentaquark molecule candidate \begin{document}$ P_c(4330) $\end{document} could be testified in the future experiment, it would shed light on interpretations of the \begin{document}$ P_c $\end{document} states.
Revisiting the top-quark pair production at future e+e colliders
Jin Ma, Sheng-Quan Wang, Ting Sun, Jian-Ming Shen, Xing-Gang Wu
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In this paper, we reanalyze the top-quark pair production at the next-to-next-to-leading order (NNLO) in QCD at future \begin{document}$ e^+e^- $\end{document} colliders by using the Principle of Maximum Conformality (PMC) method. The PMC renormalization scales in \begin{document}$ \alpha_s $\end{document} are determined by absorbing the non-conformal β terms by recursively using the Renormalization Group Equation (RGE). Unlike the conventional scale-setting method of fixing the scale at the center-of-mass energy \begin{document}$ \mu_r=\sqrt{s} $\end{document}, the determined PMC scale \begin{document}$ Q_\star $\end{document} is far smaller than the \begin{document}$ \sqrt{s} $\end{document} and increases with the \begin{document}$ \sqrt{s} $\end{document}, yielding the correct physical behavior for the top-quark pair production process. Moreover, the convergence of the pQCD series for the top-quark pair production is greatly improved due to the elimination of the renormalon divergence. For a typical collision energy of \begin{document}$ \sqrt{s}=500 $\end{document} GeV, the PMC scale is \begin{document}$ Q_\star=107 $\end{document} GeV; the QCD correction factor K for conventional results is \begin{document}$ K\sim1+0.1244^{+0.0102+0.0012}_{-0.0087-0.0011}+0.0184^{-0.0086+0.0002}_{+0.0061-0.0003} $\end{document}, where the first error is caused by varying the scale \begin{document}$ \mu_r\in[\sqrt{s}/2, 2\sqrt{s}] $\end{document} and the second error is from the top-quark mass \begin{document}$ \Delta{m_t}=\pm0.7 $\end{document} GeV. After applying the PMC, the renormalization scale uncertainty is eliminated and the QCD correction factor K is improved to \begin{document}$ K\sim 1+0.1507^{+0.0015}_{-0.0015}-0.0057^{+0.0001}_{-0.0000} $\end{document}, where the error is from the top-quark mass \begin{document}$ \Delta{m_t}=\pm0.7 $\end{document} GeV. The PMC improved predictions for the top-quark pair production are helpful for detailed studies of properties of the top-quark at future \begin{document}$ e^+e^- $\end{document} colliders.
Correlations of Baryon and Charge Stopping in Heavy Ion Collisions
Wendi Lv, Yang Li, Ziyang Li, Rongrong Ma, Zebo Tang, Prithwish Tribedy, Chun Yuen Tsang, Zhangbu Xu, Wangmei Zha
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Baryon numbers are carried by valence quarks in the standard QCD picture of the baryon structure, while some theory proposed an alternative baryon number carrier, a non-perturbative Y-shaped configuration of the gluon field, called the baryon junction in the 1970s. However, neither of the theories has been verified experimentally. It was recently suggested to search for the baryon junction by investigating the correlation of net-charge and net-baryon yields at midrapidity in heavy-ion collisions. This paper presents studies of such correlations in collisions of various heavy ions from Oxygen to Uranium with the UrQMD Monte Carlo model. The UrQMD model implements valence quark transport as the primary means of charge and baryon stopping at midrapidity. Detailed study are also carried out for isobaric \begin{document}$ _{40}^{96}{\rm{Zr}} $\end{document} + \begin{document}$ _{40}^{96}{\rm{Zr}} $\end{document} and \begin{document}$ _{44}^{96}{\rm{Ru}} $\end{document} + \begin{document}$ _{44}^{96}{\rm{Ru}} $\end{document} collisions. We found a universal trend of the charge stopping with respect to the baryon stopping, and that the charge stopping is always more than the baryon stopping. This study provides a model baseline in valence quark transport for what is expected in net-charge and net-baryon yields at midrapidity of relativistic heavy-ion collisions.
Revisit spin effects induced by thermal vorticity
Jian-Hua Gao, Shi-Zheng Yang
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We revisit the spin effects induced by thermal vorticity by calculating them directly from the spin-dependent distribution functions. For the spin-1/2 particles, we give the polarization up to the first order of thermal vorticity and compare it with the usual result calculated from the spin vector. For the spin-1 particles, we find that all the non-diagonal elements vanish and there is no spin alignment up the first order of thermal vortcity. We present the spin alignment at second-order contribution from thermal vorticity. We also find that the spin effects for both Dirac and vector particles will receive extra contribution when the spin direction is associated with the particle's momentum.
Theoretical calculations of proton emission half-lives based on a deformed Gamow-like model
Dong-Meng Zhang, Xiao-Yuan Hu, Lin-Jing Qi, Hong-Ming Liu, Ming Li, Xiao-Hua Li
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In the present study, proton emission half-lives have been investigated for the deformed proton emitters with \begin{document}$ 53\leq Z \leq 83 $\end{document} in the deformed Gamow-like model, where the deformation effect has been included in the Coulomb potential. The experimental half-lives of proton emitters can be reproduced within a factor of 3.45. For comparison, other results from the universal decay law and the new Geiger-Nuttall law are presented as well. Furthermore, the relevance of the half-lives to the angular momentum l for 117La, 121Pr, 135Tb and 141Ho has been analyzed, and corresponding possible values of l has been put forward: l=3, 3, 4, 4.
A discussion on the anomalous threshold enhancement of $ {\boldsymbol J/\boldsymbol\psi }$${ \boldsymbol\psi \bf (3770) }$ couplings and ${\boldsymbol X \bf (6900) }$ peak
Ye Lu, Chang Chen, Guang-You Qin, Han-Qing Zheng
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The attractive interaction between \begin{document}$ J/\psi $\end{document} and \begin{document}$ \psi(3770) $\end{document} has to be strong enough if X(6900) is of molecule type. We argue that since \begin{document}$ \psi(3770) $\end{document} decays predominantly into a \begin{document}$ D\bar D $\end{document} pair, the interactions between \begin{document}$ J/\psi $\end{document} and \begin{document}$ \psi(3770) $\end{document} may be significantly enhanced due to the three point \begin{document}$ D\bar D $\end{document} loop diagram. The enhancement comes from the anomalous threshold located at \begin{document}$ t=-1.288 $\end{document}GeV\begin{document}$ ^2 $\end{document}, which effect propagates into the s-channel partial wave amplitude in the vicinity of \begin{document}$ \sqrt{s}\simeq 6.94 $\end{document}GeV. This effect may be helpful in forming the \begin{document}$ X(6900) $\end{document} peak.
Exploring dark matter-gauge boson effective interactions at the current and future colliders
Yu Zhang, Yi-Wei Huang, Wei-Tao Zhang, Mao Song, Ran Ding
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In this work, we investigate the collider constraints on effective interactions between Dark Matter (DM) particles and electroweak gauge bosons in a systematic way. We consider the simplified models in which scalar or Dirac fermion DM candidates only couple to electroweak gauge bosons through high dimensional effective operators. Taking into account the induced DM-quarks and DM-gluons operators from the Renormalization Group Evolution (RGE) running effect, we present comprehensive constraints on effective energy scale Λ and Wilson coefficients \begin{document}$ C_B(\Lambda),\,C_W(\Lambda) $\end{document} from direct detection, indirect detection, and collider searches. In particular, we present the corresponding sensitivity from the Large Hadron Electron Collider (LHeC) and the Future Circular Collider in electron-proton mode (FCC-ep) for the first time, update the mono-j and mono-γ search limits at the Large Hadron Collider (LHC), and derive the new limits at the Circular Electron Positron Collider (CEPC).
α particle preformation factor in heavy and superheavy nuclei
Song Luo, Dong-Meng Zhang, Lin-Jing Qi, Xun Chen, Peng-Cheng Chu, Xiao-Hua Li
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In the present work, the α-particle preformation in heavy and superheavy nuclei from \begin{document}$ ^{220}{\rm{Th}} $\end{document} to \begin{document}$ ^{294}{\rm{Og}} $\end{document} have been investigated. Combing the experimental α decay energies and half-lives, the α-particle preformation factors \begin{document}$ P_{\alpha} $\end{document} are extracted from the ratios between theoretical α decay half-lives calculated by Two-Potential Approach (TPA) and experimental data. It is found that the α-particle preformation factors show the obvious odd-even staggering behavior and unpaired nucleons will inhibit α-particle preformation. Meanwhile, it is also found that both the α decay energy and the mass number of parent nucleus show considerable regularity with the extracted experimental α-particle preformation factors. After considering the major physical factors, a local phenomenological formula with only five valid parameters for α-particle preformation factors \begin{document}$ P_{\alpha} $\end{document} is proposed. This analytic expression not only has clear physical meaning but also has good precision. As an application, this analytic formula is extended to estimate the α-particle preformation factors and further predict the α decay half-lives for unknown even-even nuclei with Z = 118 and 120.
Higgs-like (pseudo)Scalars in AdS4, Marginal and Irrelevant Deformations in CFT3 and Instantons on S3
M. Naghdi
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With a 4-form ansatz of 11-dimensional supergravity over non-dynamical \begin{document}$AdS_4 \times S^7/Z_k$\end{document} background, with the internal space as a \begin{document}$S^1$\end{document} Hopf fibration on \begin{document}$CP^3$\end{document}, we get a consistent truncation. The (pseudo)scalars, in the resulting scalar equations in Euclidean AdS\begin{document}$_4$\end{document} space, may be viewed as arising from (anti)M-branes wrapping around internal directions in the (Wick-rotated) skew-whiffed M2-branes background (as the resulting theory is for anti-M2-branes) and so, realizing the modes after swapping the three fundamental representations \begin{document}${\bf{8}}_s$\end{document}, \begin{document}${\bf{8}}_c$\end{document}, \begin{document}${\bf{8}}_v$\end{document} of \begin{document}$SO(8)$\end{document}. Taking the backreaction on the external and internal spaces, we get massless and massive modes, corresponding to exactly marginal and marginally irrelevant deformations on the boundary CFT\begin{document}$_3$\end{document}, and write a closed solution for the bulk equation and compute its correction to the background action. Next, considering the Higgs-like (breathing) mode \begin{document}$m^2=18$\end{document}, having all supersymmetries, parity and scale-invariance broken, by solving the associated bulk equation with mathematical methods, especially the Adomian decomposition method, and analyzing the behavior near the boundary of the solutions, we realize the boundary duals in \begin{document}$SU(4) \times U(1)$\end{document}-singlet sectors of the ABJM model. Then, introducing new dual deformation \begin{document}$\Delta_+ = 3, 6$\end{document} operators made of bi-fundamental scalars, fermions and \begin{document}$U(1)$\end{document} gauge fields, we obtain \begin{document}$SO(4)$\end{document}-invariant solutions as small instantons on a three-sphere with radius at infinity, which actually correspond to collapsing bulk bubbles leading to big-crunch singularities.
Tensor force impact on shell evolution in neutron-rich Si and Ni isotopes
S.V. Sidorov, A.S. Kornilova, T.Yu. Tretyakova
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The influence of the tensor interaction of nucleons on the characteristics of neutron-rich silicon and nickel isotopes was studied in this work. Tensor forces are taken into account within the framework of the Hartree-Fock approach with the Skyrme interaction. It is shown that the addition of tensor component of interaction improves the description of the splitting between different single-particle states and leads to a decrease in nucleon-nucleon pairing correlations in silicon and nickel nuclei. Special attention was given to the role of isovector tensor forces relevant for interaction of like nucleons.
Search for the production of dark fermion candidates in association with heavy neutral gauge boson decaying to dimuon in proton-proton collisions at ${ \sqrt{\boldsymbol s} \bf = 8} $ TeV using the CMS open data
Y. Mahmoud, H. Abdallah, M. T. Hussein, S. Elgammal
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In this paper we have done a search for dark matter using a part of the data recorded by the CMS experiment during run-I of the LHC in 2012 with 8 TeV center of mass energy and integrated luminosity of 11.6 fb−1. This data has been gathered from the CMS open data. The dark matter, in the framework of simplified model (mono-Z\begin{document}$ ^{\prime} $\end{document}), can be produced from proton-proton collisions in association with a new hypothetical gauge boson Z\begin{document}$ ^{\prime} $\end{document}. Thus, the search was conducted in the dimuon plus large missing transverse momentum channel. One benchmark scenario of the mono-Z\begin{document}$ ^{\prime} $\end{document}, which is known as the Light Vector, has been used for interpreting the CMS open data. No evidence for dark matter has been observed and exclusion limits have been set on the masses of dark matter and Z\begin{document}$ ^{\prime} $\end{document} at 95% confidence level (CL).
Test particles and quasiperiodic oscillations around Kiselev black hole with cloud of strings
Javlon Rayimbaev, Uktambek Eshimbetov, Bushra Majeed, Ahmadjon Abdujabbarov, Alisher Abduvokhidov, Bakhrom Abdulazizov, Akram Xalmirzayev
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In the present work, we study the dynamics of test particles around a Schwarzschild black hole surrounded by quintessence and immersed in a scalar string cloud field. We start our study by defining the possible values of quintessence and cloud of string parameters corresponding to the existence of the black hole horizon for the fixed values of the parameter of the equation of state for dark energy. We also study the behavior of the effective potential for the circular motion of test particles, energy, and angular momentum of the particles together with innermost stable circular orbits (ISCOs). We investigate the fundamental frequencies in the particles' oscillations along stable circular orbits. We related the stability of the orbits to the Lyapunov exponent, and the chaotic behavior is studied graphically. Finally, we apply the fundamental frequencies to describe quasiperiodic oscillations (QPOs), and it is obtained that in the presence of both fields low-frequency twin-peak QPOs {are not observed}. Also, we obtain constraint values for the string clouds parameter and mass of the black hole candidates located in the center of the microquasars GRO J1655-40 & GRS 1915+105 and Milky Way galaxy.
Exploration of the ground state properties of neutron-rich sodium isotopes using the deformed relativistic mean field theory in complex momentum representations with BCS pairings
Yu-Xuan Luo, Quan Liu, Jian-You Guo
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This study explores the ground-state characteristics of neutron-rich sodium isotopes, encompassing two-neutron separation energies, root-mean-square radii, quadrupole moments of proton and neutron distributions, single-particle levels of bound and resonant states, neutron density distributions, and shapes. Simultaneously, special attention is given to the distinctive physical phenomena associated with these isotopes. The deformed relativistic mean field theory in complex momentum representations with BCS pairings (DRMF-CMR-BCS), employed in our work, provides resonant states with real physics, offering insights into deformed halo nuclei. Four effective interactions (NL3, NL3*, PK1, and NLSH) were considered to assess the influence of continuum and deformation effects on halo structures. Calculations for odd-even nuclei 35–43Na revealed the dependence on the chosen effective interaction and the number of considered resonant states. Neutron occupation patterns near the Fermi surface, particularly in orbitals \begin{document}$ 1/2^{-}_3 $\end{document} and \begin{document}$ 3/2^{-}_2 $\end{document}, were found to play a crucial role in halo formation. The study provided detailed insights into the density distributions, shape evolution, and structure of neutron-rich sodium isotopes, contributing valuable information to the field of nuclear physics.
The astrophysical S-factor and reaction rate for 15N(p,γ)16O within the modified potential cluster model
S.B. Dubovichenko, A.S. Tkachenko, R.Ya. Kezerashvili, N.A. Burkova, B.M. Yeleusheva
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We study a radiative \begin{document}$ p^{15} {\rm{N}}$\end{document} capture on the ground state of 16O at stellar energies within the framework of a modified potential cluster model (MPCM) with forbidden states, including low-lying resonances. The investigation of the 15N(\begin{document}$ p, \gamma _{0} $\end{document})16O reaction includes the consideration of \begin{document}$ {}^{3}S_{1} $\end{document} resonances due to \begin{document}$ E1 $\end{document} transitions and the contribution of \begin{document}$ {}^{3}P_{1} $\end{document} scattering wave in p + 15N channel due to \begin{document}$ {}^{3}P_{1}\longrightarrow $\end{document} \begin{document}$ {}^{3}P_{0} $\end{document} \begin{document}$ M1 $\end{document} transition. We calculated the astrophysical low-energy \begin{document}$ S- $\end{document}factor, and extrapolated \begin{document}$ S(0) $\end{document} turned out to be within 34.7-40.4 keV·b. The important role of the asymptotic constant (AC) for the 15N(\begin{document}$ p, \gamma _{0} $\end{document})16O process with interfering \begin{document}$ {}^{3}S_{1} $\end{document}(312) and \begin{document}$ {}^{3}S_{1} $\end{document}(962) resonances is elucidated. A comparison of our calculation for \begin{document}$ S- $\end{document}factor with existing experimental and theoretical data is addressed, and a reasonable agreement is found. The reaction rate is calculated and compared with the existing rates. It has negligible dependence on the variation of AC, but shows a strong impact of the interference of \begin{document}$ {}^{3}S_{1} $\end{document}(312) and \begin{document}$ {}^{3}S_{1} $\end{document}(962) resonances, especially at temperatures, referring to the CNO Gamow windows. We estimate the contribution of cascade transitions to the reaction rate based on the exclusive experimental data by Imbriani, et al. 2012. The reaction rate enhancement due to the cascade transitions is observed from \begin{document}$ T_{9} > 0.3 $\end{document} and reaches the maximum factor ~ 1.3 at \begin{document}$ T_{9}=1.3 $\end{document}. We present the Gamow energy window and a comparison of rates for radiative proton capture reactions 12N(\begin{document}$ p, \gamma $\end{document})13O, 13N(\begin{document}$ p, \gamma $\end{document}) 14O, 14N(\begin{document}$ p, \gamma $\end{document})15O, and 15N(\begin{document}$ p, \gamma $\end{document})16O obtained in the framework of the MPCM and give temperature windows, prevalence, and significance of each process.
Some remarks on compositeness of Tcc+
Chang Chen, Ce Meng, Zhiguang Xiao, Han-Qing Zheng
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Recently LHCb experimental group found an exotic state \begin{document}$ T^+_{cc} $\end{document} from the process \begin{document}$ pp \to D^0D^0\pi^+ + X $\end{document}. A key question is if it is just a molecule or may have confined tetraquark ingredient. To investigate this, different methods are taken, including a two-channel (\begin{document}$ D^{*+}D^0 $\end{document} and \begin{document}$ D^{*0}D^+ $\end{document}) K-matrix unitarization and a single channel Flatté-like parametrization method analysed by pole counting rule and spectral density function sum rule. These analyses demonstrate that \begin{document}$ T^+_{cc} $\end{document} is a molecular state, though the possibility that there may exist elementary ingredient that can not be excluded, by rough analysis on its production rate.
Solving bound-state equations for scalar and hybrid QCD in two-dimensional spacetime
Xiaolin Li, Yu Jia, Ying Li, Zhewen Mo
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We investigate the bound-state equations in two-dimensional QCD in the \begin{document}$ N_c\to \infty $\end{document} limit. We consider two types of hadrons, an exotic "meson" (which is composed of a bosonic quark and a bosonic anti-quark), and an exotic "baryon" (composed of a fermionic quark and a bosonic antiquark). Using the Hamiltonian operator approach, we derive the corresponding bound-state equations for both types of hadrons from the perspectives of the light-front quantization and equal-time quantization, and confirm the known results. We also present a novel diagrammatic derivation for the exotic "meson" bound-state equation in the equal-time quantization. The bound-state equation for the exotic baryons in the equal-time quantization in two-dimensional QCD is new. We also numerically solve various bound-state equations, obtain the hadron spectrum and the bound-state wave functions of the lowest-lying states. We explicitly demonstrate the pattern that as the hadron is boosted to the infinite-momentum frame, the forward-moving bound-state wave function approaches the corresponding light-front wave function.
Soft pattern of Rutherford scattering from heavy target mass expansion
Yu Jia, Jia-Yue Zhang
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We investigate the soft behavior of the tree-level Rutherford scattering process. We consider two types of Rutherford scattering, a low-energy massless point-like projectile (say, a spin-\begin{document}$ {1\over 2} $\end{document} or spin-\begin{document}$ 0 $\end{document} electron) hits a static massive composite target particle carrying various spins (up to spin-\begin{document}$ 2 $\end{document}), and a slowly-moving light projectile hits a heavy static composite target. For the first type, the unpolarized cross sections in the laboratory frame are found to exhibit universal forms in the first two orders of \begin{document}$ 1/M $\end{document} expansion, yet differ at the next-to-next-to-leading order (though some terms at this order still remain to be universal or depend on the target spin in a definite manner). For the second type, at the lowest order in electron velocity expansion, through all orders in \begin{document}$ 1/M $\end{document}, the unpolarized cross section is universal (also not sensitive to the projectile spin). The universality partially breaks down at relative order-\begin{document}$ v^2/M^2 $\end{document}, though some terms at this order are still universal or depend on the target spin in a specific manner. We also employ the effective field theory approach to reproduce the soft behavior of the differential cross sections for the target particle being a composite spin-\begin{document}$ {1\over 2} $\end{document} fermion.