85538672
Study of kaon decay to two pions
The weak decay of the kaon to two pions is studied within the model of Nambu and Jona-Lasinio. Using the standard effectiveweak Hamiltonian, both the decay amplitude arising from an intermediate state σ meson and the direct decay amplitude are calculated. The effect of final state interactions is also included. When the matching scale is chosen such that the decay amplitude with isospin I ¼ 2 is close to its experimental value, our model including the σ meson contributes up to 80% of the total I ¼ 0 amplitude. This supports recent suggestions that the σ meson should play a vital role in explaining the ΔI ¼ 1=2 rule in this system.
67819117
Pseudoscalar Mesons Scattering off D*-mesons with Chiral Perturbation Theory
We have systematically calculated the s-wave pseudoscalar mesons and D*- mesons scattering lengths to the third order with chiral perturbation theory, which will be helpful to reveal their strong interaction. We present the scattering lengths (1) in the framework of the heavy meson chiral perturbation theory and (2) in the framework of the infrared regularization.
118506962
Chiral perturbation theory and the $\bar B \bar B$ strong interaction
We have calculated the potentials of the heavy (charmed or bottomed) pseudoscalar mesons up to $O(\epsilon^2)$ with the heavy meson chiral perturbation theory. We take into account the contributions from the football, triangle, box, and crossed diagrams with the 2$\phi$ exchange and one-loop corrections to the contact terms. We notice that the total 2$\phi$-exchange potential alone is attractive in the small momentum region in the channel ${\bar B \bar B}^{I=1}$, ${\bar B_s \bar B_s}^{I=0}$, or ${\bar B \bar B_s}^{I=1/2}$, while repulsive in the channel ${\bar B \bar B}^{I=0}$. Hopefully the analytical chiral structures of the potentials may be useful in the extrapolation of the heavy meson interaction from lattice QCD simulation.
122655890
The $\bar B \bar B$ strong interaction with chiral perturbation theory
We study the strong interaction potentials of up to order with the heavy meson chiral perturbation theory. Besides the leading contributions from the contact terms we also consider the one-loop corrections to the contact diagrams and the contributions from the 2ϕ-exchange diagrams. Hopefully, the analytical structures of our result will be helpful in the extrapolation of the relevant heavy meson interaction in the lattice QCD simulation.
118457565
Pseudoscalar Meson and Decuplet Baryon Scattering Lengths
The excited states of the nucleon and their strong interactions with various hadrons play an important role in our understanding of non-perturbative QCD. Generally speaking, their coupling with the pseudoscalar pion, kaon and eta is governed by chiral dynamics. The first excited state of the nucleon, J = 3/2 ∆(1232), belongs to the lightest decuplet. It is degenerate with the nucleon in the large Nc limit [1, 2]. From the strong decay widths, one can extract the coupling constants of the pseudoscalar meson decuplet baryon interaction. Although it may be quite difficult to measure their scattering lengths experimentally, unlike in the pion-nucleon and kaon-nucleon cases [3–5], it is still interesting to study the scattering processes theoretically. As two well-known non-perturbative approaches of QCD at low energy, chiral perturbation theory and lattice QCD have been widely used in studying meson-baryon interactions [6–14]. With the explicitly consistent power counting scheme, the heavy baryon chiral perturbation theory (HBχPT) is a practical and useful tool in the study of the meson baryon scattering. The expansion is organized with p/Λχ, where p represents the momentum (mass) of the meson or the small residue momentum of the baryon in the non-relativistic limit, and Λχ = 4πfπ is the scale of chiral symmetry breaking. Numerically it is around the baryon mass in the chiral limit. Because of the large mass of the strange quark, the chiral corrections from the kaon and eta meson loops are significantly larger than that from the pion loop, which leads to the worse convergence of the chiral expansion in the SU(3) case. In HBχPT, the effects of excited baryons are encoded in the unknown low energy constants (LECs) in the Lagrangians. In the large Nc limit, one expects that the inclusion of the decuplet baryon contribution may partially cancel the octet contribution and be helpful to the chiral expansion. In order to investigate the contributions of the ∆, HBχPT with explicit spin-3/2 baryons and the small-scale expansion scheme have been developed in Refs. [15, 16]. Now the expansion is organized with ǫ, where ǫ means p in HBχPT or the mass difference δ between ∆ and the nucleon in the chiral limit, which is widely used in the exploration of the decuplet related processes [17–21]. There exists another power counting scheme “δ expansion” in the two-flavor case, where mπ scales as δ 2 [22–25]. In our previous work [21], we studied the decuplet contributions to the pseudoscalar meson octet baryon scattering lengths, which is an important observable reflecting their strong interaction near the threshold. The inclusion of the decuplet baryons does not improve the convergence significantly. In this paper, we will study the scattering lengths of the pseudoscalar mesons and the light decuplet baryons in the framework of the SU(3) heavy baryon chiral perturbation theory with explicit decuplet baryons. We will explore whether the small scale expansion works well in this case.
118416217
Pseudoscalar Goldstone bosons scattering off charmed baryons with chiral perturbation theory
Abstract We have systematically calculated the pseudoscalar Goldstone boson and charmed baryon scattering lengths to the third order with heavy baryon chiral perturbation theory. The scattering lengths can reveal the interaction of K Λ c , K Σ c , π Ω c , etc. For each channel, we take into account of the interaction between the external particle and every possible charmed baryon in the triplet, sextet, and excited sextet. We use dimensional regularization and modified minimal subtraction to get rid of the divergences in the loop-diagram corrections. We notice that the convergence of chiral expansion for most of the channels becomes better after we let the low energy constants absorb the analytic contributions of the loop-diagram corrections and keep the non-analytic terms only.
118060536
Measurement of $\chi_{cJ}$ decaying into $p\bar{n}\pi^{-}$ and $p\bar{n}\pi^{-}\pi^{0}$
Using a data sample of $1.06 \times 10^{8}$ $\psip$ events collected with the BESIII detector in 2009, the branching fractions of $\chi_{cJ}\to p\bar{n}\pi^{-}$ and $\chi_{cJ}\to p\bar{n}\pi^{-}\pi^{0}$ ($J$=0,1,2) are measured{Throughout the text, inclusion of charge conjugate modes is implied if not stated otherwise.}. The results for $\chi_{c0}\to p\bar{n}\pi^{-}$ and $\chi_{c2}\to p\bar{n}\pi^{-}$ are consistent with, but much more precise than those of previous measurements. The decays of $\chi_{c1}\to p\bar{n}\pi^{-}$ and $\chi_{cJ}\to p\bar{n}\pi^{-}\pi^{0}$ are observed for the first time.
7776635
Measurements of the continuum R(uds) and R values in e(+)e(-) annihilation in the energy region between 3.650 and 3.872 GeV.
We report measurements of the continuum R(uds) near the center-of-mass energy of 3.70 GeV, the R[uds(c)+psi(3770)](s) and the R(had)(s) values in e(+)e(-) annihilation at 68 energy points in the energy region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC Collider. We obtain the R(uds) for the continuum light hadron (containing u, d, and s quarks) production near the DD threshold to be R(uds)=2.141+/-0.025+/-0.085.
125977653
Lattice study on exotic vector charmonium relevant to X(4260)
In the quenched approximation and with very high statistics, a heavy vector charmonium state, with a mass of 4.33(2)GeV, is disentangled from the conventional charmonium states by using spatially extended hybrid-like interpolating field operators. Through a simultaneous fit of correlation functions built from different operators, the leptonic decay constant this state is estimated to be 31(15)MeV, which gives a much smaller leptonic decay width of 23(20)eV in comparison with that of conventional vector charmonia. The connection of this state with X(4260) is also discussed.
117349439
Probing supergravity unified theories at the Large Hadron Collider
The discovery of supersymmetry is one of the major goals of the current experiments at the Tevatron and in proposed experiments at the Large Hadron Collider (LHC). However when sparticles are produced the signatures of their production will to a significant degree depend on their hierarchical mass patterns. Here we investigate hierarchical mass patterns for the four lightest sparticles within one of the leading candidate theories - the SUGRA model. Specifically we analyze the hierarchies for the four lightest sparticles for the mSUGRA as well as for a general class of supergravity unified models including nonuniversalities in the soft breaking sector. It is shown that out of nearly $10^4$ possibilities of sparticle mass hierarchies, only a small number survives the rigorous constraints of radiative electroweak symmetry breaking, relic density and other experimental constraints. The signature space of these mass patterns at the LHC is investigated using a large set of final states including multi-leptonic states, hadronically decaying $\tau$s, tagged $b$ jets and other hadronic jets. In all, we analyze more than 40 such lepton plus jet and missing energy signatures along with several kinematical signatures such as missing transverse momentum, effective mass, and invariant mass distributions of final state observables. It is shown that a composite analysis can produce significant discrimination among sparticle mass patterns allowing for a possible identification of the source of soft breaking. While the analysis given is for supergravity models, the techniques used in the analysis are applicable to wide class of models including string and brane models.
117255094
Evidence for $\eta_{c} \rightarrow \gamma\gamma$ and Measurement of $J/\psi\rightarrow 3\gamma$
The decay of $J/\psi$ to three photons is studied using $\psi(3686)\to\pi^+\pi^-J/\psi$ in a sample of $1.0641\times10^8$ $\psi(3686)$ events collected with the BESIII detector. Evidence of the direct decay of $\eta_c$ to two photons, $\eta_c\to\gamma\gamma$, is reported, and the product branching fraction is determined to be $\mathcal{B}(J/\psi\to\gamma\eta_c,\eta_c\to \gamma\gamma)=(4.5\pm1.2\pm0.6)\times10^{-6}$, where the first error is statistical and the second is systematic. The branching fraction for $J/\psi\to3\gamma$ is measured to be $(11.3\pm1.8\pm2.0)\times 10^{-6}$ with improved precision.