查看更多>>摘要：A systematic study of the neutrino mass matrix M v with two texture zeros in a basis that the charged leptons are diagonal,and under the assumption that neutrinos are Dirac particles is performed.Our study is conduc-ted without any approximation,first analytically and then numerically.Current neutrino oscillation data is used in our analysis.Phenomenological implications of M v on lepton CP violation and neutrino mass spectrum are explored.
查看更多>>摘要：By using the3P0 pair creation model,we provide a detailed derivation of the transition matrix for a bary-on decaying into a meson-baryon system.This analysis was successfully conducted for a meson in[J.Segovia,D.R.Entem,and F.Fernandez,Phys.Lett.B 715,322(2012)],and we extend the same formalism to the baryon sector,focusing on the △(1232)→ πN strong decay width because all hadrons involved in the reaction are very well estab-lished,the two hadrons in the final state are stable and require no further analysis,all quarks are light and thus equi-valent,and the decay width of the process is relatively well measured.Utilizing a very common Rayleigh-Ritz vari-ational method to solve the 2-and 3-body Schödinger bound-state equation in which the hadron's radial wave func-tions are expanded in terms of a Gaussian basis,we can relate the expression of the invariant matrix element with the mean-square radii of hadrons involved in the decay.We use their experimental measures in such a way that only the strength of the quark-antiquark pair creation from the vacuum is a free parameter.This is then taken from our previ-ous study on strong decay widths in the meson sector[J.Segovia,D.R.Entem,and F.Fernández,Phys.Lett.B 715,322(2012)],and the obtained results are compatible with the experimental results for the calculated △(1232)→ πN decay width.Despite requiring the calculation of additional baryon strong decays,a feasible avenue towards a uni-fied description of both baryon and meson strong decay widths within a single constituent quark model framework may be attainable.Finally,this research has been developed to lay the foundation for a novel raft of applications to exotic hadrons,i.e.,the description of the baryon's coupling to meson-baryon thresholds,one of the mechanisms that is considered to be responsible for providing either a large renormalization to naive states or genuine dynamically-generated meson-baryon molecules.
查看更多>>摘要：We study the possibility of finding axion-like particles(ALPs)through the leptonic decays of heavy mesons.The Standard Model(SM)predictions of the branching ratios of the leptonic decays of heavy mesons are less than the corresponding experimental upper limits.This provides some room for the existence of decay channels,of which the ALP is one of the products.Three scenarios are considered:First,the ALP is only coupled to one single charged fermion,namely,the quark,the antiquark,or the charged lepton;second,the ALP is only coupled to quark and antiquark with the same strength;and third,the ALP is coupled to all the charged fermions with the same strength.The constraints of the coupling strength in different scenarios are obtained by comparing the experimental data of the branching ratios of leptonic decays of B-,D+,and Ds+mesons with the theoretical predictions achieved by using the Bethe-Salpeter(BS)method.These constraints are further applied to predict the upper limits of the leptonic decay processes of the Bc-meson in which the ALP participates.
查看更多>>摘要：In this paper,we introduce the More-Interaction Particle Transformer(MIParT),a novel deep-learning neural network designed for jet tagging.This framework incorporates our own design,the More-Interaction Atten-tion(MIA)mechanism,which increases the dimensionality of particle interaction embeddings.We tested MIParT using the top tagging and quark-gluon datasets.Our results show that MIParT not only matches the accuracy and AUC of LorentzNet and a series of Lorentz-equivariant methods,but also significantly outperforms the ParT model in background rejection.Specifically,it improves background rejection by approximately 25％with a signal effi-ciency of 30％on the top tagging dataset and by 3％on the quark-gluon dataset.Additionally,MIParT requires only 30％of the parameters and 53％of the computational complexity needed by ParT,proving that high performance can be achieved with reduced model complexity.For very large datasets,we double the dimension of particle embed-dings,referring to this variant as MIParT-Large(MIParT-L).We found that MIParT-L can further capitalize on the knowledge from large datasets.From a model pre-trained on the 100M JetClass dataset,the background rejection performance of fine-tuned MIParT-L improves by 39％on the top tagging dataset and by 6％on the quark-gluon dataset,surpassing that of fine-tuned ParT.Specifically,the background rejection of fine-tuned MIParT-L improves by an additional 2％compared to that of fine-tuned ParT.These results suggest that MIParT has the potential to in-crease the efficiency of benchmarks for jet tagging and event identification in particle physics.
查看更多>>摘要：We study the exclusive semileptonic decays Υ(1S)→ B(c)ℓ(v)ℓ,where ℓ=e,μ,τ.The relevant hadronic form factors are calculated using the covariant confined quark model developed previously by our group.We pre-dict the branching fractions B(Υ(1S)→ B(c)ℓ(v)ℓ)to be of the order of 10-13 and 10-10 for the case of B and B c,re-spectively.Our predictions agree well with other theoretical calculations.We also consider the effects of possible new physics in the case of Υ(1S)→ B cτ(v)τ and show that the branching fraction of this decay can be enhanced by an order of magnitude using constraints from the B →D(*)ℓ(v)ℓ and B c → J/Ψℓ(v)ℓ experimental data.
查看更多>>摘要：Using gauge/gravity duality,we studied the exotic hybrid pseudopotentials at finite temperature and chemical potential.The Σ hybrid meson can be described by a model including an object called"defect"on a string linking the quark and antiquark.The Σu-hybrid potential at zero temperature and chemical potential was first pro-posed by Andreev and is perfectly described.In this study,we extended the aforementioned model to finite chemic-al potential and compared the separate distance and pseudopotentials of ∑g+and Σu-.Unlike the Σg+ground state,theΣu-hybrid pseudopotentials no longer exhibit Coulomb-like behavior at short distances.In addition,temperature and chemical potential have a significant impact on the Σu-hybrid pseudopotentials.The screen distances and hybrid pseudopotentials of Σu-significantly decrease when increasing temperature and chemical potential.We represented the melting diagram of Σg+and Σu-in the T-μ plane and confirmed that the quark-antiquark pair in Σu-excited state is easier to melt than that in Σg+ground state.
查看更多>>摘要：A systematic study was conducted on the theoretical estimation of the nuclear cross sections of charged particle induced reactions on rare earth nuclei.The production cross sections of the 150,149,148,146,144,143,141 Pm and 149,147Nd nuclei were calculated theoretically via proton induced reactions on neodymium using TALYS(version 1.96)code in the default mode,with different combinations of nuclear models as well as adjusted nuclear model parameters from the reaction threshold up to a proton energy of 65 MeV.The theoretically computed results were compared with the experimental results taken from the EXFOR database and literature reported by various research groups.Moreover,the effects of various level density models,preequilibrium models,optical model potentials,and gamma strength functions on the cross section calculation were considered.This theoretical analysis will help elucid-ate the theory of nuclear reaction models and improve the evaluated nuclear data libraries.
查看更多>>摘要：An algebraic model with three-body boson interactions is proposed to incorporate the different quadru-pole modes in nuclear collectivity.It is shown that the recently observed anomalous collective structure character-ized by B4/2=B(E2;4 1 → 2 1)/B(E2;2 1 → 0 1)＜1.0 and R4/2=E(4 1)/E(2 1)≥2.0,which cannot yet be explained by any other microscopic nuclear models,naturally emerges in the present model due to the inclusion of triaxial ro-tor modes.This description is further extended to describe odd-A nuclei by including the coupling to the Fermion de-gree of freedom.This allows us to give a unified explanation of the anomalous B(E2)strengths in both even-even and even-odd systems,which indicate different behaviors.As examples,the model is applied to describe the spectro-scopy and E2 transition properties of 168,169,170,171 Os.Allrecent measurements of these isotopes can be well repro-duced on the same footing,which suggests that the anomalous collectivity persists even in odd-A systems.
查看更多>>摘要：The observed low-lying K=5/2±positive-and negative-parity bands in the stable nucleus 153Eu are in-vestigated using the reflection-asymmetric triaxial particle rotor model.The experimental energy spectra,energy staggering parameters,and intraband E2 and Ml transition probabilities are well reproduced.The calculated interb-and B(E1)values are found to depend sensitively on the octupole deformation parameter β30,although the energy spectra and intraband E2 and Ml transitions can be reproduced without the octupole degree of freedom.The ob-served enhanced E1 transition probabilities can be reproduced with β30=0.05.The detailed analysis of the intrinsic wave functions shows these nearly degenerate positive-and negative-parity bands are built on two individual proton configurations,i.e.,dominated by πg7/2[Ω=5/2]and πh11/2[Ω=5/2],respectively,which differs from the parity doublet bands built on a single parity-mixed configuration.
查看更多>>摘要：The blast wave model with Tsallis statistics is used to analyze the transverse momentum spectra of pro-tons(p),deuterons(d),and tritons(t)in√S NN=200 GeV gold-gold(Au-Au)collisions at the RHIC in various cent-rality bins.In particular transverse momentum ranges,the model results closely match experimental data from the PHENIX(p)and STAR(d and t)collaborations.The data are compared with those of protons obtained in Cu+Cu collisions and deuterons and tritons in Ru+Ru collisions at a center of mass energy of 200 GeV from the STAR col-laboration.Particle spectra are used to derive the kinetic freeze-out temperatures,transverse flow velocities,and freeze-out volumes.According to the findings,the kinetic freeze-out temperature increases from the central to peri-pheral collisions.In this transition,the transverse flow velocity and freeze-out volume both decrease.For the colli-sions of both collaborations,this study reveals mass-dependent kinetic freeze-out temperature and differential volume possibilities.Overall,the non-extensivity parameter q decreases with increasing centrality of the studied heavy-ion collisions,and heavier mass particles have smaller values of q,which implies higher degrees of thermaliz-ation and equilibrium in more central collisions and for heavier particles.
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