477 research outputs found
A determination of the average up-down, strange and charm quark masses from
We present a lattice QCD determination of the average up-down, strange and
charm quark masses based on simulations performed by the European Twisted Mass
Collaboration with dynamical fermions. We simulated at three
different values of the lattice spacing, the smallest being approximately
, and with pion masses as small as . Our results are:
,
, ,
and
Mass of the b-quark and B-decay constants from Nf=2+1+1 twisted-mass Lattice QCD
We present precise lattice computations for the b-quark mass, the quark mass
ratios mb/mc and mb/ms as well as the leptonic B-decay constants. We employ
gauge configurations with four dynamical quark flavors, up/down, strange and
charm, at three values of the lattice spacing (a ~ 0.06 - 0.09 fm) and for pion
masses as low as 210 MeV. Interpolation in the heavy quark mass to the bottom
quark point is performed using ratios of physical quantities computed at nearby
quark masses exploiting the fact that these ratios are exactly known in the
static quark mass limit. Our results are also extrapolated to the physical pion
mass and to the continuum limit and read: mb(MSbar, mb) = 4.26(10) GeV, mb/mc =
4.42(8), mb/ms = 51.4(1.4), fBs = 229(5) MeV, fB = 193(6) MeV, fBs/fB =
1.184(25) and (fBs/fB)/(fK/fpi) = 0.997(17).Comment: Version to appear in PRD. Added comments to simulation setup and
error budget discussion. 1+20 pages, 9 figure
Leptonic decay constants fK, fD and fDs with Nf = 2+1+1 twisted-mass lattice QCD
We present a lattice QCD calculation of the pseudoscalar decay constants fK,
fD and fDs performed using the gauge configurations produced by the European
Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks, which include
in the sea, besides two light mass degenerate quarks, also the strange and
charm quarks with masses close to their values in the real world. The
simulations are based on a unitary setup for the two light mass-degenerate
quarks and on a mixed action approach for the strange and charm quarks. We use
data simulated at three different values of the lattice spacing in the range
0.06 - 0.09 fm and at pion masses in the range 210 - 450 MeV. Our main results
are: fK+ / fpi+ = 1.184 (16), fK+ = 154.4 (2.0) MeV, which incorporate the
leading strong isospin breaking correction due to the up- and down-quark mass
difference, and fK = 155.0 (1.9) MeV, fD = 207.4 (3.8) MeV, fDs = 247.2 (4.1)
MeV, fDs / fD = 1.192 (22) and (fDs / fD) / (fK / fpi) = 1.003 (14) obtained in
the isospin symmetric limit of QCD. Combined with the experimental measurements
of the leptonic decay rates of kaon, pion, D- and Ds-mesons our results lead to
the following determination of the CKM matrix elements: |Vus| = 0.2269 (29),
|Vcd| = 0.2221 (67) and |Vcs| = 1.014 (24). Using the latest value of |Vud|
from superallowed nuclear beta decays the unitarity of the first row of the CKM
matrix is fulfilled at the permille level.Comment: 20 pp., 4 figures; revised version to appear in PRD; improved
calculation of IB effects for fK+; minor changes in the final values. arXiv
admin note: text overlap with arXiv:1403.450
- …