Search results for "meson"
showing 10 items of 1548 documents
Exotic meson-meson molecules and compact four-quark states
2009
PACS numbers: 12.39.Jh, 14.40.Lb, 21.45.-v, 31.15.xj.-- ArXiv pre-print avaible at: http://arxiv.org/abs/0903.2949v1
Quark-meson coupling model with constituent quarks: Exchange and pionic effects
1998
The binding energy of nuclear matter including exchange and pionic effects is calculated in a quark-meson coupling model with massive constituent quarks. As in the case with elementary nucleons in QHD, exchange effects are repulsive. However, the coupling of the mesons directly to the quarks in the nucleons introduces a new effect on the exchange energies that provides an extra repulsive contribution to the binding energy. Pionic effects are not small. Implications of such effects on observables are discussed.
Quark-lepton mass relation and CKM mixing in an A(4) extension of the minimal supersymmetric standard model
2013
An interesting mass relation between down-type quarks and charged leptons has been recently predicted within a supersymmetric SU(3)(c) circle times SU(2)(L) circle times U(1)(Y) model based on the A(4) flavor symmetry. Here we propose a simple extension which provides an adequate full description of the quark sector. By adding a pair of vectorlike up quarks, we show how the CKM entries V-ub, V-cb, V-td and V-ts arise from deviations of the unitarity. We perform an analysis including the most relevant observables in the quark sector, such as oscillations and rare decays of kaons, B-d and B-s mesons. In the lepton sector, the model predicts an inverted hierarchy for the neutrino masses, leadi…
Mixing induced CP asymmetries in b → sγ decay and spontaneous CP violation
1998
Abstract We analyze the mixing induced CP asymmetry in the decay b → sγ in the left-right symmetric model with spontaneous CP . This model possesses the useful property that all the CP -violating observables can be expressed in term of a single phase, a ratio of scalar vevs, quark masses and weak mixing angles but not on unconstrained quantities such as Yukawa coupling or additional phases. The calculated CP asymmetry can be much larger than in the Standard Model.
Study of exclusive semileptonic and nonleptonic decays ofBc−in a nonrelativistic quark model
2006
We present results for different observables measured in semileptonic and non-leptonic decays of the $B_c^-$ meson. The calculations have been done within the framework of a nonrelativistic constituent quark model. In order to check the sensitivity of all our results against the inter-quark interaction we use five different quark--quark potentials. We obtain form factors, decay widths and asymmetry parameters for semileptonic $B_c^-\to c\bar c$ and $B_c^-\to \bar B$ decays. In the limit of infinite heavy quark mass our model reproduces the constraints of heavy quark spin symmetry. For the actual heavy quark masses we find nonetheless large corrections to that limiting situation for some for…
A new state of hadronic matter at high density
1997
We propose in this article that if the chemical potential exceeds a critical value in dense hadronic medium, a first-order phase transition to a new state of matter with Lorentz symmetry spontaneously broken (in addition to the explicit breaking) takes place. As a consequence, light vector mesons get excited as ``almost'' Goldstone bosons. Since the light vector mesons dominantly couple to photons, the presence of these new vector mesons could lead to an enhancement in the dilepton production from dense medium at an invariant mass lower than the free-space vector-meson mass. We provide a low-energy quark model which demonstrates that the above scenario is a generic case for quark theories w…
Deeply virtual electroproduction of photons and mesons on the nucleon
1999
We give predictions for the leading order amplitudes for deeply virtual Compton scattering and hard meson electroproduction reactions at large Q^2 in the valence region in terms of skewed quark distributions. We give first estimates for the power corrections to these leading order amplitudes. In particular, we outline examples of experimental opportunities to access the skewed parton distributions at the current high-energy lepton facilities : JLab, HERMES and COMPASS.
Meson-Baryon s-wave Resonances with Strangeness -3
2006
Starting from a consistent SU(6) extension of the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian (Phys. Rev. D74 (2006) 034025), we study the s-wave meson-baryon resonances in the strangeness S=-3 and negative parity sector. Those resonances are generated by solving the Bethe-Salpeter equation with the WT interaction used as kernel. The considered mesons are those of the 35-SU(6)-plet, which includes the pseudoscalar (PS) octet of pions and the vector (V) nonet of the rho meson. For baryons we consider the 56-SU(6)-plet, made of the 1/2+ octet of the nucleon and the 3/2+ decuplet of the Delta. Quantum numbers I(J^P)=0(3/2^-) are suggested for the experimental resonances Omega*(2250)-…
The size of and physics beyond the Standard Model
2005
Abstract We analyse the allowed range of values of χ , both in the Standard Model and in models with new physics, pointing out that a relatively large value of χ , e.g., of order λ , is only possible in models where the unitarity of the 3 × 3 Cabibbo–Kobayashi–Maskawa matrix is violated through the introduction of extra Q = 2 / 3 quarks. We study the interesting case where the extra quark is an isosinglet, determining the allowed range for χ and the effect of a large χ on various low-energy observables, such as CP asymmetries in B meson decays. We also discuss the correlated effects which would be observable at high energy colliders, like decays t → c Z , modifications of the cross section …
Search for admixture of scalar top quarks in the tt¯ lepton + jets final state at s=1.96 TeV
2009
A search for pair production of the lightest supersymmetric partner of the top quark is performed in the lepton+jets channel using 0.9 fb-1 of data collected by the D0 experiment. Kinematic differences between scalar top quark pair production and the dominant top quark pair production background are used to separate the two processes. First limits from Run II of the Fermilab Tevatron Collider for the scalar top quark decaying to a chargino and a b quark are obtained for scalar top quark masses of 130-190 GeV and chargino masses of 90-150 GeV.