3,175 research outputs found
Non-perturbative renormalization of tensor currents: strategy and results for and QCD
Tensor currents are the only quark bilinear operators lacking a
non-perturbative determination of their renormalisation group (RG) running
between hadronic and electroweak scales. We develop the setup to carry out the
computation in lattice QCD via standard recursive finite-size scaling
techniques, and provide results for the RG running of tensor currents in and QCD in the continuum for various Schr\"odinger Functional
schemes. The matching factors between bare and renormalisation group invariant
currents are also determined for a range of values of the lattice spacing
relevant for large-volume simulations, thus enabling a fully non-perturbative
renormalization of physical amplitudes mediated by tensor currents.Comment: 50 pages, 14 Figure
X(3872) as a D-D* molecule bound by quark exchange forces
The Bethe-Salpeter equation for the T-Matrix of D-D* scattering is solved
with a meson-meson potential that results from 2nd order Born approximation of
quark exchange processes. This potential turns out to be complex and energy
dependent due to the pole contribution from the coupling to the intermediate
J/psi-rho meson pair propagator. As a consequence, a bound state with a mass
close to 3.872 GeV occurs in the J/psi-rho continuum. This result suggests that
quark exchange forces may provide the solution to the puzzling question for the
origin of the interaction which leads to a binding of D and D* mesons in the
X(3872) state.Comment: 6 pages, 3 figures, contribution to the Proceedings of the 28th
Max-Born-Symposium on "Three days on quarkyonic island", Wroclaw, Poland, May
19-21, 201
A road map to solar neutrino fluxes, neutrino oscillation parameters, and tests for new physics
We analyze all available solar and related reactor neutrino experiments, as
well as simulated future 7Be, p-p, pep, and ^8B solar neutrino experiments. We
treat all solar neutrino fluxes as free parameters subject to the condition
that the total luminosity represented by the neutrinos equals the observed
solar luminosity (the `luminosity constraint'). Existing experiments show that
the p-p solar neutrino flux is 1.02 +- 0.02 (1 sigma) times the flux predicted
by the BP00 standard solar model; the 7Be neutrino flux is 0.93^{+0.25}_{-0.63}
the predicted flux; and the ^8B flux is 1.01 +- 0.04 the predicted flux. The
neutrino oscillation parameters are: Delta m^2 = 7.3^{+0.4}_{-0.6}\times
10^{-5} eV^2 and tan^2 theta_{12} = 0.41 +- 0.04. We evaluate how accurate
future experiments must be to determine more precisely neutrino oscillation
parameters and solar neutrino fluxes, and to elucidate the transition from
vacuum-dominated to matter-dominated oscillations at low energies. A future 7Be
nu-e scattering experiment accurate to +- 10 % can reduce the uncertainty in
the experimentally determined 7Be neutrino flux by a factor of four and the
uncertainty in the p-p neutrino flux by a factor of 2.5 (to +- 0.8 %). A future
p-p experiment must be accurate to better than +- 3 % to shrink the uncertainty
in tan^2 theta_{12} by more than 15 %. The idea that the Sun shines because of
nuclear fusion reactions can be tested accurately by comparing the observed
photon luminosity of the Sun with the luminosity inferred from measurements of
solar neutrino fluxes. Based upon quantitative analyses of present and
simulated future experiments, we answer the question: Why perform low-energy
solar neutrino experiments?Comment: Updated all calculations to include SNO salt-phase data and improved
GNO and SAGE data, all released September 7, 2003 at TAUP03. Updating
produces only minor numerical changes. Accepted for publication in JHE
Probing New Physics by Comparing Solar and KamLAND Data
We explore whether KamLAND and solar data may end up inconsistent when
analyzed in terms of two-flavor neutrino oscillations. If this turned out to be
the case, one would be led to conclude that there is more new physics, besides
neutrino masses and mixing, in the leptonic sector. On the other hand, given
that KamLAND and solar data currently agree when analyzed in terms of
two-flavor neutrino oscillations, one is able to place nontrivial bounds on
several manifestations of new physics. In particular, we compute how well a
combined KamLAND and solar data analysis is able to constrain a specific form
of violation of CPT invariance by placing a very stringent upper bound, |Delta
m^2 - Delta bar{m}^2| < 1.1 10^{-4} eV^2 (3 sigma). We also estimate upper
bounds on sin^2 theta - sin^2 bar{theta}. These are quite poor due to the fact
that matter effects are almost irrelevant at KamLAND, which leads to an
intrinsic inability to distinguish whether the antineutrino mixing angle is on
the light (bar{theta}
pi/4). We briefly discuss whether this ambiguity can be resolved by future
long-baseline bar{nu}_e to bar{nu}_{e,mu} searches.Comment: Reference adde
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