Search results for "Quark"
showing 10 items of 2905 documents
Charmonium spectroscopy above thresholds
2009
We present a systematic and self-consistent analysis of four-quark charmonium states and applied it to study compact four-quark systems and meson-meson molecules. Our results are robust and should serve to clarify the situation of charmonium spectroscopy above the threshold production of charmed mesons.
The Neutral K Meson System
2003
After the observation of direct CP violation in the neutral kaon system in 1988, it became clear that the Kobayashi-Maskawa mechanism of weak quark mixing was the most likely and most natural candidate for explaining this phenomenon. It seemed natural, therefore, that the same mechanism would also produce observable CP-violating effects in other neutral meson systems. The B0 system is the evident candidate for observing CP violation in another physical system described in this chapter.
Heavy meson-antimeson molecules in effective field theory: The role of one pion exchange and heavy quark spin symmetry
2012
In this contribution we study heavy meson-antimeson molecules from the effective field theory perspective. In particular, we are concerned with the role of the one pion exchange interaction and heavy quark spin symmetry in the description of molecular states. As we will show, one pion exchange is in general a perturbative effect. This means that at lowest order we can describe the molecular states in terms of contact interactions only, a remarkable simplification. The application of heavy quark spin symmetry will be very interesting, as we will be able to predict new heavy meson-antimeson bound states from known ones. For instance, if we assume that the X(3872) is in fact a JPC = 1++ DD/DD …
Prediction of NarrowN*andΛ*Resonances with Hidden Charm above 4 GeV
2010
Up to now, all established baryons can be ascribed into 3-quark (qqq) configurations [1], although some of them were suggested to be meson-baryon dynamically generated states [2–8] or states with large (qqqq¯ q) components [9–11]. A difficulty to pin down the nature of these baryon resonances is that the predicted states from various models are around the same energy region and there are always some adjustable ingredients in each model to fit the experimental data. In this letter, we report a study of the interactions between various charmed mesons and charmed baryons within the framework of the coupled channel unitary approach with the local hidden gauge formalism. Several meson-baryon dyn…
The Bc → J/ΨKD weak decay and its relation with the D*s0(2317) resonance
2016
We study the influence of the D * s 0 (2317) + resonance in the decay B c → J/ψKD . In this process, we consider that the B c meson decays first into J/ψ and the quark pair cs , and then the quark pair hadronizes into DK or D s η components. The final state interaction, generating the D * s 0 (2317) + resonance, is described by the chiral heavy meson unitary approach. With the parameters chosen in order to match the pole position of the D * s 0 (2317) + , we obtain the DK invariant mass distribution of the decay B c → J/ψDK , and also the rate for B c → J/ψD * s 0 (2317). We predict the ratio of these two magnitudes. This decay mechanism has not been measured yet, and it would provide insig…
A dynamical mechanism for quark mixing and neutrino oscillations
1999
We show that assuming fermion generations to be given by a gauge symmetry plus a certain Higgs mechanism for its breaking, the known empirical features of quark and lepton mixing can be largely explained, including in particular the fact that the mixing (CKM) matrix element $U_{\mu3}$ responsible for the muon anomaly in atmospheric neutrinos is near maximal and much larger than their quark counterparts $V_{cb}$ and $ V_{ts}$, while the corner elements for both quarks ($V_{ub}, V_{td}$) and leptons ($U_{e3}$) are all very small. The mechanism also gives automatically a hierarchical fermion mass spectrum which is intimately related to the mixing pattern.
Quark-model study of few-baryon systems
2005
We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the NN, N$\Delta$, $\Delta\Delta$ and NN$^*(1440)$ systems, and also for the binding energies of three non-strange baryon systems. We make emphasis on observable effects related to quark antisymmetry and its interplay with quark dynamics.
Nucleon Structure Functions in a Constituent Quark Scenario
1999
Using a simple picture of the constituent quark as a composite system of point-like partons, we construct the polarized part on distributions by a convolution between constituent quark momentum distributions and constituent quark structure functions. We achieve good agreement with experiments in the unpolarized as well as in the polarized case, though a good description of the recent polarized neutron data requires the introduction of one more paramater. When our results are compared with similar calculations using non-composite constituent quarks, the accord with the experiments of the present scheme is impressive. We conclude that DIS data are consistent with a low energy scenario dominat…
Phenomenology of enhanced light quark Yukawa couplings and the W±h charge asymmetry
2017
I propose the measurement of the $W^\pm h$ charge asymmetry as a consistency test for the Standard Model (SM) Higgs, which is sensitive to enhanced Yukawa couplings of the first and second generation quarks. I present a collider analysis for the charge asymmetry in the same-sign lepton final state, $p p \to W^\pm h \to (\ell^\pm \nu) (\ell^\pm \nu jj)$, aimed at discovery significance for the SM $W^\pm h$ production mode in each charge channel with 300 fb$^{-1}$ of 14 TeV LHC data. Using this decay mode, I estimate the statistical precision on the charge asymmetry should reach 0.4\% with 3 ab$^{-1}$ luminosity, enabling a strong consistency test of the SM Higgs hypothesis. I also discuss di…
SU(3) Analysis of $$p\overline p$$ Decays into Two Mesons
1985
The process \(p\overline p \to MM'\) is analyzed in terms of 8 SU(3) invariant amplitudes with definite charge conjugation properties. The amplitudes are constructed such that they either correspond to quark annihilation or rearrangement diagrams. For the C’-odd case the process \(p\overline p \to PS + PS\) is examined, whereas for the C’-even case the decay \(p\overline p \to PS + V\) is analyzed. It will be shown that for C’-odd both annihilation and rearrangement contribute, whereas rearrangement is dominant in the C’-even case.