Light hadrons from lattice QCD with light (u, d), strange and charm dynamical quarks

Abstract

We present results of lattice QCD simulations with mass-degenerate up and down and mass-split strange and charm (N f = 2 + 1 + 1) dynamical quarks using Wilson twisted mass fermions at maximal twist. The tuning of the strange and charm quark masses is performed at two values of the lattice spacing a ≈ 0.078 fm and a ≈ 0.086 fm with lattice sizes ranging from L ≈ 1.9 fm to L ≈ 2.8 fm. We measure with high statistical precision the light pseudoscalar mass m PS and decay constant f PS in a range 270 m PS 510 MeV and determine the low energy parameters f 0 andl 3,4 of SU(2) chiral perturbation theory. We use the two values of the lattice spacing, several lattice sizes as well as different values of the light, strange and charm quark masses to explore the systematic effects. A first study of discretisation effects in light-quark observables and a comparison to N f = 2 results are performed.

Constraint on the low energy constants of Wilson chiral perturbation theory

“…The results of Refs. [11][12][13][14][15][16][17][18][19][20], however, favor the first-order scenario, with m ± π > m 0 π for µ 0 = 0. This means that 2W ′ 6 + W ′ 8 > 0, which, combined with the inequality W ′ 8 ≤ 0, implies in turn that…”

“…For discussion of these issues see Refs. [17,18,20,[25][26][27][28][29][30][31]. All that matters here, however, is that a consistent criterion exists in which m c is fixed, such as the one based on the PCAC mass used in practice in present simulations [18][19][20].…”

“…the results of simulations using dynamical twisted-mass fermions, which find strong evidence for the first-order scenario [11][12][13][14][15][16][17][18][19][20]. Of course, large N c scaling may not be useful for N c = 3, in which case the connection between the constraint and the phase scenario need not hold.…”

Lattice QCD determination of m b , f B and f Bs with twisted mass Wilson fermions

“…A comparison of our N f = 2 result for the B and B s decay constants, to existing results from N f = 2 + 1 quark flavor simulations [39,40] suggests that the error due to the partial quenching of the strange quark is smaller at present than other systematic uncertainties. In this respect we mention that simulations with N f = 2 + 1 + 1 dynamical flavors are already being performed by ETMC and preliminary results for several flavor physics observables have been recently presented [41,42].…”

Alpha, Lambda and Gluon condensate: Precision sudies with dynamical charm

“…These are the first to incorporate the effects of dynamical charm quarks. In other words, this is an ensemble of sample gauge fields including N f =2+1+1, two light degenerate and two heavy, dynamical quark flavours (see [9,10] for details of the simulations setup) with a twisted-mass fermion action [11,12]. Combining the propagators in Taylor scheme we were able to extract the strong coupling constant, which agrees pretty well with the experimental results from τ decays [13] and "world average" from PDG [14] at all scales from τ to Z 0 .…”