482 research outputs found
Quark Contributions to Nucleon Momentum and Spin from Domain Wall fermion calculations
We report contributions to the nucleon spin and momentum from light quarks
calculated using dynamical domain wall fermions with pion masses down to 300
MeV and fine lattice spacing a=0.084 fm. Albeit without disconnected diagrams,
we observe that spin and orbital angular momenta of both u and d quarks are
opposite, almost canceling in the case of the d quark, which agrees with
previous calculations using a mixed quark action. We also present the full
momentum dependence of n=2 generalized form factors showing little variation
with the pion mass.Comment: 7 pages, 5 figures, NT-LBNL-11-020, MIT-CTP-4323. Presented at the
29th International Symposium on Lattice Field Theory (Lattice 2011), Squaw
Valley, California, 10-16 Jul 201
Kluyveromyces aestuarii, a potential environmental quality indicator yeast for mangroves in the State of Rio de Janeiro, Brazil
Nucleon Electromagnetic Form Factors from Lattice QCD using 2+1 Flavor Domain Wall Fermions on Fine Lattices and Chiral Perturbation Theory
We present a high-statistics calculation of nucleon electromagnetic form
factors in lattice QCD using domain wall quarks on fine lattices, to
attain a new level of precision in systematic and statistical errors. Our
calculations use lattices with lattice spacing a=0.084 fm for
pion masses of 297, 355, and 403 MeV, and we perform an overdetermined analysis
using on the order of 3600 to 7000 measurements to calculate nucleon electric
and magnetic form factors up to 1.05 GeV. Results are shown
to be consistent with those obtained using valence domain wall quarks with
improved staggered sea quarks, and using coarse domain wall lattices. We
determine the isovector Dirac radius , Pauli radius and
anomalous magnetic moment . We also determine connected contributions
to the corresponding isoscalar observables. We extrapolate these observables to
the physical pion mass using two different formulations of two-flavor chiral
effective field theory at one loop: the heavy baryon Small Scale Expansion
(SSE) and covariant baryon chiral perturbation theory. The isovector results
and the connected contributions to the isoscalar results are compared with
experiment, and the need for calculations at smaller pion masses is discussed.Comment: 44 pages, 40 figure
Long-lived photoexcited states in polydiacetylenes with different molecular and supramolecular organization
With the aim of determining the importance of the molecular and supramolecular organization on the excited states of polydiacetylenes, we have studied the photoinduced absorption spectra of the red form of poly[1,6-bis(3,6-didodecyl-N-carbazolyl)-2,4-hexadiyne] (polyDCHD-S) and the results compared with those of the blue form of the same polymer. An interpretation of the data is given in terms of both the conjugation length and the interbackbone separation also in relation to the photoinduced absorption spectra of both blue and red forms of poly[1,6-bis(N-carbazolyl)-2,4-hexadiyne] (polyDCHD), which does not carry the alkyl substituents on the carbazolyl side groups. Information on the above properties is derived from the analysis of the absorption and Raman spectra of this class of polydiacetylenes
Peripherical processes 2 3 and 2 4 in QED and QCD in high energy collisions
Differential cross section of processes with high energy
collisions in frames of QED: creation of scalar, pseudoscalar and lepton pair -
are considered in Weizs\"acker - Williams approximation. In frames of QCD
processes with conversion of initial proton (antiproton) to fermionic jets
accompanied with one gluon jet as well as the state of two gluons and
quark-antiquark pair (with out rapidity gap) are considered in frames of
effective Reggion action of theory of Lipatov. Process of creation of a Higgs
boson accompanied with two fermionic jets is considered. The azimuthal
correlation in process of two gluon jet separated by rapidity gap is
investigated. Effects of gluon reggeization are taken into account. Some
distributions are illustrated by numerical calculations.Comment: 17 pages, 6 figure
The size of electron-hole pairs in pi conjugated systems
We have performed momentum dependent electron energy-loss studies of the
electronic excitations in sexithiophene and compared the results to those from
parent oligomers. Our experiment probes the dynamic structure factor
S(q,omega)and we show that the momentum dependent intensity variation of the
excitations observed can be used to extract the size of the electron-hole pair
created in the excitation process. The extension of the electron-hole pairs
along the molecules is comparable to the length of the molecules and thus maybe
only limited by structural constraints. Consequently, the primary
intramolecular electron-hole pairs are relatively weakly bound. We find no
evidence for the formation of excitations localized on single thiophene units.Comment: RevTex, 3 figures, to appear in Physical Review Letter
Ab-initio calculation of the electronic and optical excitations in polythiophene: effects of intra- and interchain screening
We present an calculation of the electronic and optical excitations of an
isolated polythiophene chain as well as of bulk polythiophene. We use the GW
approximation for the electronic self-energy and include excitonic effects by
solving the electron-hole Bethe-Salpeter equation. The inclusion of interchain
screening in the case of bulk polythiophene drastically reduces both the
quasi-particle band gap and the exciton binding energies, but the optical gap
is hardly affected. This finding is relevant for conjugated polymers in
general.Comment: 4 pages, 1 figur
Vertex functions for d-wave mesons in the light-front approach
While the light-front quark model (LFQM) is employed to calculate hadronic
transition matrix elements, the vertex functions must be pre-determined. In
this work we derive the vertex functions for all d-wave states in this model.
Especially, since both of and are mesons, the Lorentz
structures of their vertex functions are the same. Thus when one needs to study
the processes where is involved, all the corresponding formulas for
states can be directly applied, only the coefficient of the vertex
function should be replaced by that for . The results would be useful
for studying the newly observed resonances which are supposed to be d-wave
mesons and furthermore the possible 2S-1D mixing in with the LFQM.Comment: 12 pages, 2 figures, some typos corrected and more discussions added.
Accepted by EPJ
Quark Soup al dente: Applied Superstring Theory
We discuss the application of the AdS/CFT correspondence to possibly gain new
physical insights for the strongly coupled quark-gluon plasma. This article
provides an informal summary of a talk given by RCM at the 18th International
Conference on General Relativity and Gravitation in July 2007.Comment: This article provides an informal summary of a talk given by RCM at
the 18th International Conference on General Relativity and Gravitation in
July 200
Heavy Flavour Production at Tevatron and Parton Shower Effects
We present hadron-level predictions from the Monte Carlo generator Cascade
and numerical calculations of charm and beauty production at the Fermilab
Tevatron within the framework of the -factorization QCD approach. Our
consideration is based on the CCFM-evolved unintegrated gluon densities in a
proton. The performed analysis covers the total and differential cross sections
of open charm and beauty quarks, and mesons (or rather muons from their
semileptonic decays) and the total and differential cross sections of di-jet hadroproduction. We study the theoretical uncertainties of our
calculations and investigate the effects coming from parton showers in initial
and final states. Our predictions are compared with the recent experimental
data taken by the D0 and CDF collaborations. Special attention is put on the
specific angular correlations between the final-state particles. We demonstrate
that the final state parton shower plays a crucial role in the description of
such observables. The decorrelated part of angular separations can be fully
described, if the process is included.Comment: Fig 8,9 10 replaced, small corrections in text A discussion of the
delta phi results is adde
- …