Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe charm quark mass with dynamical fermions
86
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We compute the charm quark mass in lattice QCD and compare different formulations of the heavy quark, and quenched data to that with dynamical sea quarks. We take the continuum limit of the quenched data by extrapolating from three different lattice spacings, and compare to data with two flavours of dynamical sea quarks with a mass around the strange at the coarsest lattice spacing. Both the FNAL and ALPHA formalism are used. We find the different heavy quark formulations have the same continuum limit in the quenched approximation, and limited evidence that this approximation overestimates the charm quark mass.
rate research
Read More
The masses of the low-lying strange and charm baryons are evaluated using two degenerate flavors of twisted mass sea quarks for pion masses in the range of about 260 MeV to 450 MeV. The strange and charm valence quark masses are tuned to reproduce the mass of the kaon and D-meson at the physical point. The tree-level Symanzik improved gauge action is employed. We use three values of the lattice spacing, corresponding to $beta=3.9$, $beta=4.05$ and $beta=4.2$ with $r_0/a=5.22(2)$, $r_0/a=6.61(3)$ and $r_0/a=8.31(5)$ respectively. %spacings $a=0.0855(5)$ and $a=0.0667(3)$ determined from the pion decay constant. We examine the dependence of the strange and charm baryons on the lattice spacing and strange and charm quark masses. The pion mass dependence is studied and physical results are obtained using heavy baryon chiral perturbation theory to extrapolate to the physical point.
We summarize four contributions about dynamical twisted mass fermions. The resulting report covers results for N_f=2 obtained from three different gauge actions, namely the standard Wilson plaquette gauge action, the DBW2 and the tree-level Symanzik improved gauge action. In addition, first results for N_f=2+1+1 flavours of twisted mass fermions are discussed.
We present the results of a partially quenched lattice QCD calculation of light quark masses with $N_f=2$ degenerate dynamical flavors. Numerical simulations are carried out using the plaquette gauge action and the Wilson quark action at $beta = 5.8$ ($a^{-1} simeq 3.2gev$). The spatial extension of the $24^3 times 48$ lattice is about 1.5 fm. Configurations have been generated at four values of the sea quark masses, for which the ratio of pseudoscalar over vector meson masses is in the range $M_P/M_V simeq 0.60 div 0.75$. An important feature of the present study is the use of non-perturbative renormalization, performed with the $ri$ method. The effects of dynamical sea quarks in the determination of light quark masses have been investigated by performing a quenched calculation on a similar lattice. Our results for the average up-down and strange quark masses are $m_{ud}^{MS} (2gev) = 4.3(4) (^{+1.1}_{-0.4})mev$ and $m_s^{MS}(2gev)=101(8)(^{+25}_{-9}) mev$. These values are larger than those obtained by evaluating the quark mass renormalization constants with one-loop (boosted) perturbation theory. Our results for the light quark masses are compatible with those obtained in the quenched simulation. No significant sea quark effects are seen, at the values of sea quark masses used in the present study.
We present results on the mass of the nucleon and the Delta using two dynamical degenerate twisted mass quarks and the tree-level Symanzik improved gauge action. The evaluation is performed at four quark masses corresponding to a pion mass in the range of about 300-600 MeV on lattices of 2.1-2.7 fm. We check for cut-off effects by evaluating these baryon masses on lattices of spatial size 2.1 fm at beta=3.9 and beta=4.05 and on a lattice of 2.4 fm at beta=3.8. The values we find are compatible within our statistical errors. Lattice results are extrapolated to the physical limit using continuum chiral perturbation theory. Performing a combined fit to our lattice data at beta=3.9 and beta=4.05 we find a nucleon mass of 964pm 28 (stat.) pm 8 (syst.) MeV. The nucleon mass at the physical point provides an independent determination of the lattice spacing. Using heavy baryon chiral perturbation theory at O(p^3) we find a_{beta=3.9}=0.0890pm 0.0039(stat.) pm 0.0014(syst.) fm, and a_{beta=4.05}= 0.0691pm 0.0034(stat.) pm 0.0010(syst.) fm, in good agreement with the values determined from the pion decay constant. Isospin violating lattice artifacts in the Delta-system are found to be compatible with zero for the values of the lattice spacings used in this work. Performing a combined fit to our lattice data at beta=3.9 and beta=4.05 we find for the masses of the Delta^{++,-} and Delta^{+,0} 1316 pm 60 (stat.) MeV and 1330 pm 74 (stat.) MeV respectively. We confirm that in the continuum limit they are also degenerate.
We present an ongoing project aimed at determining the thermodynamic Equation of State (EoS) of quark--gluon matter from lattice QCD with two generations of dynamical quarks. We employ the Wilson twisted mass implementation for the fermionic fields and the improved Iwasaki gauge action. Relying on $T=0$ data obtained by the ETM Collaboration the strange and charm quark masses are fixed at their physical values, while the pion mass takes four values in the range from 470 MeV down to 210 MeV. The temperature is varied within a fixed--lattice scale approach. The values for the pseudocritical temperature are obtained from various observables. For the EoS we show preliminary results for the pure gluonic contribution obtained at the pion mass value 370 MeV, where we can compare with previously obtained results with $N_f=2$ degenerate light flavours.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
