Search results for "Down quark"
showing 10 items of 23 documents
Light baryons and their electromagnetic interactions in the covariant constituent quark model
2012
We extend the confined covariant constituent quark model that was previously developed by us for mesons to the baryon sector. In our numerical calculation we use the same values for the constituent quark masses and the infrared cutoff as have been previously used in the meson sector. In a first application we describe the static properties of the proton and neutron, and the $\Lambda$-hyperon (magnetic moments and charge radii) and the behavior of the nucleon form factors at low momentum transfers. We discuss in some detail the conservation of gauge invariance of the electromagnetic transition matrix elements in the presence of a nonlocal coupling of the baryons to the three constituent quar…
Quark mean field model for nucleons in nuclei
1998
We propose the quark mean field model for nucleons in nuclei, where the meson mean fields created by other nucleons act on quarks in a nucleon and change the nucleon properties in nuclei. We take the constituent quark model for the nucleon, which naturally allows the direct coupling of pions and in turn other mesons as $\ensuremath{\sigma}$ and $\ensuremath{\omega}$ mesons. We find very good nuclear matter properties with the use of the nonlinear self-energy terms in the meson Lagrangian. We expect the spin-orbit splitting in finite nuclei to be large due to the large reduction of the nucleon mass, which is in agreement with experiment. The nucleon size increases by about 7% at the normal m…
Integrating out strange quarks in ChPT
2007
We study three flavour chiral perturbation theory in a limit where the strange quark mass is much larger than the external momenta and the up and down quark masses, and where the external fields are those of two-flavour chiral perturbation theory. In this case, the theory reduces to the one of SU(2)_L x SU(2)_R. Through this reduction, one can work out the strange quark mass dependence of the LECs in the two-flavour case. We present the pertinent relations at two-loop order for F,B and l_i.
Heavy baryons in the relativistic quark model
2003
Abstract We present a summary of results for exclusive decays of single and double heavy-flavored baryons in the relativistic three-quark model.
Charm quark mass and D-meson decay constants from two-flavour lattice QCD
2013
We present a computation of the charm quark's mass and the leptonic D-meson decay constants f_D and f_{D_s} in two-flavour lattice QCD with non-perturbatively O(a) improved Wilson quarks. Our analysis is based on the CLS configurations at two lattice spacings (a=0.065 and 0.048 fm, where the lattice scale is set by f_K) and pion masses ranging down to ~ 190 MeV at L*m_pi > 4, in order to perform controlled continuum and chiral extrapolations with small systematic uncertainties.
Minimal Leptoquark Explanation for theRD(*),RK, and(g−2)μAnomalies
2016
We show that by adding a single new scalar particle to the standard model, a TeV-scale leptoquark with the quantum numbers of a right-handed down quark, one can explain in a natural way three of the most striking anomalies of particle physics: the violation of lepton universality in B[over ¯]→K[over ¯]l^{+}l^{-} decays, the enhanced B[over ¯]→D^{(*)}τν[over ¯] decay rates, and the anomalous magnetic moment of the muon. Constraints from other precision measurements in the flavor sector can be satisfied without fine-tuning. Our model predicts enhanced B[over ¯]→K[over ¯]^{(*)}νν[over ¯] decay rates and a new-physics contribution to B_{s}-B[over ¯]_{s} mixing close to the current central fit v…
Up and down quark masses from Finite Energy QCD sum rules to five loops
2008
The up and down quark masses are determined from an optimized QCD Finite Energy Sum Rule (FESR) involving the correlator of axial-vector divergences, to five loop order in Perturbative QCD (PQCD), and including leading non-perturbative QCD and higher order quark mass corrections. This FESR is designed to reduce considerably the systematic uncertainties arising from the (unmeasured) hadronic resonance sector, which in this framework contributes less than 3-4% to the quark mass. This is achieved by introducing an integration kernel in the form of a second degree polynomial, restricted to vanish at the peak of the two lowest lying resonances. The driving hadronic contribution is then the pion …
Quark number susceptibilities at high temperatures
2013
We calculate second and fourth order quark number susceptibilities for 2+1 flavor QCD in the high temperature region. In our study we use two improved staggered fermion formulations, namely the highly improved staggered quark formulation, and the so-called p4 formulation, as well as several lattice spacings. Second order quark number susceptibilities are calculated using both improved staggered fermion formulations, and we show that in the continuum limit the two formulations give consistent results. The fourth order quark number susceptibilities are studied only using the p4 formulation and at non-zero lattice spacings. We compare our results on quark number susceptibilities with recent we…
Quark and lepton mixing in weak interactions
1986
The coupling strength of weak interactions between quarks of different flavour shows a clear pattern: couplings between members of the same family are much stronger than the ones between neighbour families and couplings between first and third family haye escaped detection so far. The coupling strength between different families decreases with increasing quark mass, but a theoretical explanation of this pattern is still missing. On the other side, lepton mixing and neutrino oscillations have not been seen in experiments yet. An analysis of experimental data in the framework of simultaneous oscillations of three neutrino fluxes yields limits on the three mixing angles which are about as rest…
Experimental analysis of weak mixing angles between three or four quark generations
1987
New data on weak quark decays and on weak heavy quark production are used to obtain the allowed ranges of elements of the quark mixing matrix for three or four generations of sequential quarks. The analysis yields allowed ranges for the three mixing angles in the six-quark case and for the six mixing angles in the eight-quark case.