نتایج جستجو برای: baryon mass
تعداد نتایج: 483501 فیلتر نتایج به سال:
We analyze the octet baryon masses and the pion/kaon–nucleon σ–terms in the framework of heavy baryon chiral perturbation theory. We include all terms up-to-and-including quadratic order in the light quark masses, mq. We develop a consistent scheme to estimate low–energy constants related to scalar–isoscalar operators in the framework of resonance exchange involving one–loop graphs. The pertine...
We investigate whether the Affleck-Dine (AD) mechanism works when the contribution of the twoloop thermal correction to the potential is negative in the gauge-mediated supersymmetry breaking models. The AD field is trapped far away from the origin by the negative thermal correction for a long time until the temperature of the universe becomes low enough. The most striking feature is that the Hu...
The quark cluster model approach to the baryon-baryon interaction is reviewed and recent application to the charge symmetry breaking in nuclear force is discussed. According to quantum chromodynamics (QCD), hadrons are bound states of quarks and gluons, and their interactions are governed by the non-Abelian gauge interaction. Their structures are potentially very complex as QCD is strongly inte...
A new intuitive method for the rapid calculation of the leading nonanalytic behavior of hadronic observables in quenched chiral perturbation theory is presented. After proving the technique in a consideration of baryon masses, the quenched magnetic moments of octet baryons are addressed. The technique provides a separation of magnetic moment contributions into full, sea, valence and quenched va...
We study baryon pair production in two-photon collisions, γγ → BB̄, within perturbative quantum chromodynamics, treating baryons as quark-diquark systems. We extend previous work within the same approach by treating constituent-mass effects systematically by means of an expansion in the small parameter (mass/photon energy). Our approach enables us to give a consistent description of the cross se...
Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK0 S → pπ+π−. A peak is observed in the pK0 S invariant mass spectrum at 1528 ± 2.6(stat) ± 2.1(syst) MeV. Depending on the background model, the naive statistical significance of the peak is 4–6 standard deviations and its width may be somewhat larger than the experimental...
Resonances and the Weinberg–Tomozawa 56-baryon –35-meson interaction. Abstract. Vector meson degrees of freedom are incorporated into the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian by using a scheme which relies on spin–flavor SU(6) symmetry. The corresponding Bethe-Salpeter approximation successfully reproduces previous SU(3)–flavor WT results for the lowest-lying s–wave negative pa...
Recently, Falk [1] has proposed that there exist two undiscovered heavy baryons: a Σc(2380) that decays radiatively to the Λc, and a Σb(5760) that decays radiatively to the Λb. In this note I use the systematics of the spin-dependent forces between quarks to argue against the existence of these two new states. The same ideas suggest that two of the proposed “equal spacing rules” [1] among heavy...
The mass of the nucleon is studied in a chiral quark-diquark model. Both scalar and axial-vector diquarks are taken into account for the construction of the nucleon state. After the hadronization procedure to obtain an effective meson-baryon Lagrangian, the quark-diquark self-energy is calculated in order to generate the baryon kinetic term as well as the mass of the nucleon. It turns out that ...
We have studied bounds on the neutrino mass using new data from the Sloan Digital Sky Survey measurement of the baryon acoustic peak. We find that even in models with a running spectral index where the number of neutrinos and the dark energy equation of state are allowed to vary, the bound on the sum of neutrino masses is robustly below 0.5 eV. Using the SDSS Lyman-α constraint on the amplitude...
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