Sheldon L. Glashow
Non-standard physics may induce detectable flavor-changing $ΔB=2$ interactions without inducing their flavor-conserving counterparts. Searches for $n$-$\overline n$ oscillations do not constrain such interactions, thereby motivating dedicated searches for $ΔB=2$ nuclear decays into strange final states. In particular, the simple model herein proposed enables dibaryon decay exclusively into states with $S=2$.
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Recent experiments at Jefferson Laboratory and potential new facilities at the Japan Proton Accelerator Research Complex (J-PARC) make it evident that the discovery of a spin-singlet S-wave di-cascade bound state of two cascade (Xi) particles is feasible. We state the simple arguments, based on SU(3) flavor symmetry, for the existence of this bound state, review the previous predictions and comment on the experimental conditions necessary for detection.
Roles of instantons in strangeness hadron physics are discussed. After introducing general features of instantons, hadron spectroscopy under the influence of instanton-quark effective interactions is discussed. Emphases are on the H dibaryon, spin-orbit splittings of P-wave baryons and baryon-baryon interactions and spectrum of the pentaquarks.
Lattice QCD Study of Positive Parity Dibaryons with Maximal Charm and Strangeness
本研究利用格点QCD方法，基于MILC系综计算了最大粲数、奇异数的单味双重子基态能谱，发现S=0道的Ωccc-Ωccc系统存在束缚态信号，为理解单味双重子性质提供了新结果。
The state of the art in dibaryons with strangeness is reviewed, including the K^{-}pp dibaryon which signals the onset of antikaon-nuclear binding. A new type of strange dibaryons is highlighted, where the primary binding mechanism is provided by strong p-wave pion interactions, as demonstrated by a quasibound (I=3/2,JP=2+) pion-hyperon-nucleon dibaryon calculation.
Deuteron electrodisintegration is described in a relativistic PWIA framework. The reduction to the factorized PWIA, and the effect thereof on the observables accessible in parity-violating scattering, is discussed. The extent to which such relativistic effects may affect the extraction of strangeness nucleon form factors from measurements of the PV asymmetry, is investigated.
It is pointed out that the Chiral Constituent Quark Model (CCQM) interactions that bind the H dibaryon and Lambda-Lambda-3H overbind Lambda-Lambda-6He by more than 4 MeV, thus outdating the CCQM in the strangeness S=-2 sector.
Search for singly charmed dibaryons in baryon-baryon scattering
本文在手征夸克模型下系统研究单粲双重子系统，通过重子-重子散射发现两个奇异数 S=-1 的共振态，并强调束缚道与开放道耦合计算对寻找真正共振态的重要性。
I review hadronic processes involving strange hadrons, especially hyperons from the quark structure point of view. The strong interaction of quarks expects several important new features when the strangeness is introduced upon the non-strange degrees of freedom. I concentrate on the instanton induced interaction, effects of the Pauli principle for strangeness and the nonleptonic weak interaction of strangeness. The single hadron as well as the two baryon systems including the $H$ dibaryon and other exotic hadronic systems with strangeness are studied in this context.
We consider the two-nucleon weak interaction with a pionless effective field theory. Dibaryon fields are introduced to facilitate calculations and ensure precision in the initial and final state propagators. Weak interactions are accounted for with the parity-violating dibaryon-nucleon-nucleon vertices, which contain unknown weak dibaryon-nucleon-nucleon coupling constants. We apply the model to the calculation of a parity-violating observable in the neutron-proton capture at threshold. Result is obtained up to the linear order in the unknown dibaryon-nucleon-nucleon coupling constants. We com…
In this work, we systematically investigate the dibaryons with charm number $C$=1 and strangeness number $S$=$\pm$ 1 from the interactions of a charmed baryon and a strange baryon $Λ_cΛ$, $Λ_cΣ^{(*)}$, $Σ_c^{(*)}Λ$, and $Σ^{(*)}_cΣ^{(*)}$, and corresponding interactions of a charmed baryon and an antistrange baryon $Λ_c\barΛ$, $Λ_c\barΣ^{(*)}$, $Σ^{(*)}_c\barΛ$, and $Σ^{(*)}_c\barΣ^{(*)}$. With the help of the effective Lagrangians with $SU(3)$, heavy quark, and chiral symmetries, the potentials of the interactions considered are constructed by light meson exchanges. To search for the possible…
The hypothetical $SU(3)$ flavor-singlet dibaryon state $S$ with strangeness $-2$ has been discussed as a dark-matter candidate capable of explaining the curious 5-to-1 ratio of the mass density of dark matter to that of baryons. We study the early-universe production of dibaryons and find that irrespective of the hadron abundances produced by the QCD quark/hadron transition, rapid particle reactions thermalized the $S$ abundance, and it tracked equilibrium until it "froze out" at a tiny value. For the plausible range of dibaryon masses (1860 - 1890 MeV) and generous assumptions about its inter…
We investigate $S=-2$ production from the $Λp\to K^+X$ reactions within the effective Lagrangian approach. The $Λp\to K^+ΛΛ$ and $Λp\to K^+Ξ^-p$ reactions are considered to find the lightest $S=-2$ system, which is $H$-dibaryon. We assume that the $H(2250)\toΛΛ$, and $H(2270)\toΞ^-p$ decays with the intrinsic decay width of 1 MeV. According to our calculations, the total cross-sections for $Λp\to K^+ΛΛ$ and $Λp\to K^+Ξ^-p$ reactions were found to be of the order of a few $μ$b in the $Λ$ beam momentum range of up to 5 GeV$/c$. Furthermore, the direct access of information regarding the interfer…
Dense compact objects like neutron stars or black holes have always been one of Gerry Brown's favorite research topics. This is closely related to the effects of strangeness in nuclear physics. Here, we review the chiral Effective Field Theory approach to interactions involving nucleons and hyperons, the possible existence of strange dibaryons, the fate of hyperons in nuclear matter and the present status of three-body forces involving hyperons and nucleons.
The momentum correlation functions of baryon pairs, which reflects the baryon-baryon interaction at low energies, are investigated for multi-strangeness pairs ($ΩΩ$ and $NΩ$) produced in relativistic heavy-ion collisions. We calculate the correlation functions based on an expanding source model constrained by single-particle distributions. The interaction potentials are taken from those obtained from recent lattice QCD calculations at nearly physical quark masses. Experimental measurements of these correlation functions for different system sizes will help to disentangle the strong interaction…
The flavor-singlet H-dibaryon, which has strangeness -2 and baryon number 2, is studied by the approach recently developed for the baryon-baryon interactions in lattice QCD. The flavor-singlet central potential is derived from the spatial and imaginary-time dependence of the Nambu-Bethe-Salpeter wave function measured in N_f=3 full QCD simulations with the lattice size of L = 2, 3, 4 fm. The potential is found to be insensitive to the volume, and it leads to a bound H-dibaryon with the binding energy of 30 - 40 MeV for the pseudo-scalar meson mass of 673 - 1015 MeV.
We have revisited the calculation of the neutron electric dipole moment in the presence of the CP-violating operators up to dimension five based on the chiral perturbation theory. Especially, we focus on the contribution of strangeness content. In the calculation, we extract the nucleon matrix elements of scalar-type quark operators from the results of the lattice QCD simulations, while those of the dipole-type quark-gluon operators are evaluated by using the method of the QCD sum rules. As a result, it is found that although the strangeness quantity in nucleon is small, the contribution of th…
The $J/ψ$ weak decays are rare but possible within the standard model of elementary particles. Inspired by the potential prospects at the future intensity frontier, the $C$ parity violating $J/ψ$ ${\to}$ $πη^{({\prime})}$, $ηη^{\prime}$ decays and the strangeness changing $J/ψ$ ${\to}$ $πK$, $Kη^{({\prime})}$ decays are studied with the perturbative QCD approach. It is found that the $J/ψ$ ${\to}$ $ηη^{\prime}$ decays have relatively large branching ratios, about the order of $10^{-11}$, which might be within the measurement capability and sensitivity of the future STCF experiment.
The influence of gluon and Goldstone boson induced tensor interactions on the dibaryon masses and D-wave decay widths has been studied in the quark delocalization, color screening model. The effective S-D wave transition interactions induced by gluon and Goldstone boson exchanges decrease rapidly with increasing strangeness of the channel. The tensor contribution of K and $η$ mesons is negligible in this model. There is no six-quark state in the light flavor world studied so far that can become bound by means of these tensor interactions besides the deuteron. The partial D-wave decay widths of…
Ever since Yukawa proposed that the pion is responsible for mediating the nucleon-nucleon interaction, meson exchanges have been widely used in understanding hadron-hadron interactions. The most studied mesons are the $σ$, $π$, $ρ$, and $ω$, while other heavier mesons are often argued to be less relevant because they lead to short range interactions. However, the ranges of interactions should be compared with the size of the system under study but not in absolute terms. In this work, we propose that one charmoninium exchange is responsible for the formation of the $Ω_{ccc}Ω_{ccc}$ dibaryon, re…
Investigation of deuteron-like singly bottomed dibaryon resonances
本文利用旋轮子核模型研究了具有不同strangeness的双核子共振态，发现两个可能的共振态并探讨了其结构特征和实验探索意义。
$H$ dibaryon and its cousins from SU(6)-constrained baryon-baryon interaction
基于SU(6)约束的核子-核子相互作用，研究H双核子及其相关态的束缚态和共振特性，提供实验验证的信号。
Recently the HAL QCD Collaboration reported the $Ω-Ω$ and $N-Ω$ interaction potentials by the lattice QCD simulations. Based on these results, $NΩ$ ($^5S_2$) and $ΩΩ$ ($^1S_0$) bound states were predicted with the binding energy about a few MeV. In addition, $N-Ω$ HBT correlation function was also measured by the STAR Collaboration as well as the ALICE Collaboration. These results provide dynamical information whether or not $Ω$-dibaryons exist in the interaction aspects. Another necessary point for the detection of $Ω$-dibaryons is the experimental environment where the bound state could be p…
We analyze the parity-violating (PV) components of the analyzing power in elastic electron-proton scattering and discuss their sensitivity to the strange quark contributions to the proton weak form factors. We point out that the component of the analyzing power along the momentum transfer is independent of the electric weak form factor and thus compares favorably with the PV beam asymmetry for a determination of the strangeness magnetic moment. We also show that the transverse component could be used for constraining the strangeness radius. Finally, we argue that a measurement of both componen…
The extraction of the strangeness form factors from parity violating elastic electron-proton scattering is sensitive to the electromagnetic form factors at low Q^2. We provide parameterizations for the form factors and uncertainties, including the effects of two-photon exchange corrections to the extracted EM form factors. We study effect of the correlations between different form factors, in particular as they impact the parity violating asymmetry and the extraction of the strangeness form factors. We provide a prescription to extract the strangeness form factors from the asymmetry that provi…
Two particle vacuum transitions (oscillations) are studied in the general case. We found that: 1) a nondiagonal mass term characterising oscillations is the width of two particle transitions into each other (this width can be computed by the standard method); 2) two types of oscillations take place: real and virtual. Solution of the problem of origin of mixing angle in the theory of vacuum oscillations is given. It is shown that neutral K meson and neutrino oscillations must proceed via two stages. First, neutral K^{o}, antineutral K-eigenstates of strong interaction (or nu(e), nu(mu), nu(tau)…
Even though lots of $Λ$-hypernuclei have been found and measured, multi-strangeness hypernuclei consisting of $Ω$ are not yet discovered. The studies of multi-strangeness hypernuclei help us further understand the interaction between hyperons and nucleons. Recently the $ΩN$ and $ΩΩ$ interactions as well as binding energies were calculated by the HAL-QCD's lattice Quantum Chromo-Dynamics (LQCD) simulations and production rates of $Ω$-dibaryon in Au + Au collisions at RHIC and Pb + Pb collisions at LHC energies were estimated by a coalescence model. The present work discusses the production of m…
The production of dibaryons, light nuclei and hypertriton in the most central Au+Au collisions at $\sqrt{s_{NN}}=$ 11.5 and 200 GeV are investigated by using a naive coalescence model. The production of light nuclei is studied and found that the production rate reduces by a factor of 330 (1200) for each extra nucleon added to nuclei at $\sqrt{s_{NN}}=$ 11.5 (200) GeV. The $p_{T}$ integrated yield of multistrange hadrons falls exponentially as strangeness quantum number increases. We further investigate strangeness population factor $S_{3}, S_{2}$ as a function of transverse momentum as well as…
Standard analyses of low-energy NN and nuclear parity-violating observables have been based on a pi-, rho-, and omega-exchange model capable of describing all five independent s-p partial waves. Here a parallel analysis is performed for the one-body, exchange-current, and nuclear polarization contributions to the anapole moments of 133Cs and 205Tl. The resulting constraints are not consistent, though there remains some degree of uncertainty in the nuclear structure analysis of the atomic moments.
Spectroscopic Properties of Double-Strangeness Molecular Tetraquarks
本文基于单玻色子交换模型与耦合道薛定谔方程，研究了 $\ar K^{(*)} \ar K^{(*)}$ 双奇异分子四夸克态的谱学性质，确定了 $0(1^+)$ 态为最可能候选者，并分析了其强衰变、磁矩与辐射衰变，呼吁实验在 $B$ 介子衰变中寻找。
We study the parity-violating pion-nucleon coupling $G_π$ in the framework of a realistic three flavor Skryme model. We find a sizeable enhancement of $G_π\simeq 0.8 ... 1.3 \cdot 10^{-7}$ compared to previous calculations in two-flavor models with vector mesons. This strangeness enhancement stems from induced kaon fields of the chiral soliton and the non-monotoneous dependence on symmetry breaking of the nucleon matrix element of the flavor singlet piece of the operator associated with these induced fields. Both features are sensitive to four quark operators including an $\bar s s$ pair.
Contributions from physics beyond the Standard Model, strange quarks in the nucleon, and nuclear structure effects to the left-right asymmetry measured in parity-violating (PV) electron scattering from $\nuc{12}{C}$ and the proton are discussed. It is shown how lack of knowledge of the distribution of strange quarks in the nucleon, as well as theoretical uncertainties associated with higher-order dispersion amplitudes and nuclear isospin-mixing, enter the extraction of new limits on the electroweak parameters $S$ and $T$ from these PV observables. It is found that a series of elastic PV electr…
We consider lepton-flavor violation in strangeness changing ($|ΔS|=1$) semileptonic $τ$-lepton decays arising from new physics encoded in a standard model effective Lagrangian. Its invariance under the standard model gauge group entails the relevance of other processes which can serve as complementary probes of the new physics operators. We show in particular that for some of them the bounds implied by current data on the rare kaon decays involving a neutrino pair, $K\to πν\barν$, are stronger than the existing limits from direct searches for lepton-flavor-violating semileptonic $τ$ decays. We…
The pieces of the hypernuclear strangeness violating potential due to the pseudoscalar meson exchanges are derived using methods which were successfully applied to hyperon nonleptonic decays. The estimates are tested by comparison with measured hyperon nonleptonic decay amplitudes. All isospin changes $ΔI=1/2$ and $ΔI=3/2$ are included in the derived potential. All calculational methods used are reviewed and described in detail.
Rare kaon decays are an important testing ground of the electroweak flavor theory: They can provide new signals of CP-violating phenomena. The interplay of long-distance QCD effects in strangeness-changing transitions can be analyzed with Chiral Perturbation Theory techniques. In particular, two rare kaon decays are analyzed: The first decay, K_L -> pi0 e+e-, is being searched for as a signal of direct Delta S = 1 CP violation. We provide a thorough updating of the analysis of the three components of the decay: 1) Direct CP violation, 2) CP violation through the mass matrix and 3) CP-conservin…
In models with a low quantum gravity scale, one might expect sizable effects from nonrenormalizable interactions that violate the global symmetries of the standard model. While some mechanism must be invoked in such theories to suppress higher-dimension operators that contribute to proton decay, operators that change baryon number by two units are less dangerous and may be present at phenomenologically interesting levels. Here we focus on Delta B=2 operators that also change strangeness. We demonstrate how to compute explicitly a typical nucleon-nucleon decay amplitude, assuming a nonvanishing…
New physics (NP) in charmless strangeness-changing $B$ and $B_s$ decays, which are dominated by the $b \to s$ penguin amplitudes, can either preserve isospin or change it by one unit. A general formalism is presented studying pairs of processes related to each other by isospin reflection. We discuss information on $ΔI$ in NP amplitudes, provided by time-integrated CP-violating rate asymmetries in $B^+$ and $B^0$ decays (or in $B_s$ decays), differences between rates for isospin-reflected processes, and coefficients $S$ of $\sin Δm t$ in time-dependent CP asymmetries. These four asymmetries in …
Studies of the strangeness changing hadronic weak interaction have produced a number of puzzles that have so far evaded a complete explanation within the Standard Model. Their origin may lie either in dynamics peculiar to weak interactions involving strange quarks or in more general aspects of the interplay between strong and weak interactions. In principle, studies of the strangeness conserving hadronic weak interaction using parity violating hadronic and nuclear observables provide a complementary window on this question. However, progress in this direction has been hampered by the lack of a…
Studies of lepton-flavor violation in strangeness-changing ($|ΔS|=1$) transitions have a~long tradition in the kaon sector where they provide some of the strongest limits on physics beyond the standard model. Recent hints of violation of lepton-flavor universality in $B$-meson decays have revived interest in lepton-flavor violation as the two phenomena appear simultaneously in many extensions of the standard model. At the same time, the LHCb experiment has produced new results for the hyperon process $Σ^+\to pμ^+μ^-$ and may be in a position to study other rare hyperon decay modes. With this i…
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