75 research outputs found
Static-static-light-light tetraquarks in lattice QCD
I report on a lattice computation of the energy of a system of two light
quarks and two static antiquarks as a function of the separation of the static
antiquarks. In terms of hadrons such a system corresponds to a pair of B mesons
and its energy to the hadronic potential. I present selected results for
different isospin, spin and parity combinations of the individual B mesons
mainly focusing on those channels relevant to determine, whether two B mesons
may form a bound tetraquark state.Comment: 6 pages, 1 figure, talk given at "Excited QCD 2011", February 20-25
2011, Les Houches, Franc
The omega-rho meson mass splitting and mixing from lattice QCD
We compare flavour singlet and non-singlet vector mesons from first
principles using lattice QCD. With N_f=2 flavours of light quark, this
addresses the omega-rho mass difference.
Using maximally twisted-mass lattice QCD, we are able for the first time to
determine this mass difference precisely and we compare with experiment. We
also discuss omega-rho mixing effects arising within QCD through the u-d quark
mass difference.Comment: 12 pages 4 figure
K -> pion Semileptonic Form Factors from Two-Flavor Lattice QCD
We present new lattice results of the K -> pion semileptonic form factors
obtained from simulations with two flavors of dynamical twisted-mass fermions,
using pion masses as light as 260 MeV. Our main result is f+(0) = 0.9560 (84),
which, combined with the latest experimental data for Kl3 decays, leads to
|V_{us}| = 0.2267 (5)_exp (20)_f+(0). Using the PDG(2008) determinations of
|Vud| and |Vub| our result implies for the unitarity relation |Vud|**2 +
|Vus|**2 + |Vub|**2 = 1.0004 (15). For the O(p**6) term of the chiral expansion
of f+(0) we get Df = f+(0) - 1 - f2 = -0.0214 (84).Comment: 4 pages, 4 figures, 1 table, revte
Static-light meson masses from twisted mass lattice QCD
We compute the static-light meson spectrum using two-flavor Wilson twisted
mass lattice QCD. We have considered five different values for the light quark
mass corresponding to 300 MeV < m_PS < 600 MeV. We have extrapolated our
results, to make predictions regarding the spectrum of B and B_s mesons.Comment: 7 pages, 2 figures, talk given at the XXVI International Symposium on
Lattice Field Theory, July 14 - 19 2008, Williamsburg, Virginia, US
Light quark masses and pseudoscalar decay constants from Nf=2 Lattice QCD with twisted mass fermions
We present the results of a lattice QCD calculation of the average up-down
and strange quark masses and of the light meson pseudoscalar decay constants
with Nf=2 dynamical fermions. The simulation is carried out at a single value
of the lattice spacing with the twisted mass fermionic action at maximal twist,
which guarantees automatic O(a)-improvement of the physical quantities. Quark
masses are renormalized by implementing the non-perturbative RI-MOM
renormalization procedure. Our results for the light quark masses are
m_ud^{msbar}(2 GeV)= 3.85 +- 0.12 +- 0.40 MeV, m_s^{msbar}(2 GeV) = 105 +- 3 +-
9 MeV and m_s/m_ud = 27.3 +- 0.3 +- 1.2. We also obtain fK = 161.7 +- 1.2 +-
3.1 MeV and the ratio fK/fpi=1.227 +- 0.009 +- 0.024. From this ratio, by using
the experimental determination of Gamma(K-> mu nu (gamma))/Gamma(pi -> mu nu
(gamma)) and the average value of |Vud| from nuclear beta decays, we obtain
|Vus|=0.2192(5)(45), in agreement with the determination from Kl3 decays and
the unitarity constraint.Comment: 20 pages, 5 figure
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