Traganje za nedostajućim barionima snopom linearno polariziranog zračenja

The photoproduction of ω and ρ mesons from protons with a beam of linearlypolarized photons will be used to decouple baryon resonance production from texchange processes in the center-of-mass energy regime of 1.72 to 2.24 GeV at Hall B of Jefferson Lab. Both the ωN and ρN channels are expected to be a significant branch for baryon resonances. t-channel exchange contributions can only be disentangled by the use of a linearly-polarized photon beam. The measurement will employ a linearly-polarized beam of photons, produced by the approved Coherent Bremsstrahlung Facility, to measure the beam asymmetry as well as the spin density matrix elements of the decay spin-0 mesons of the parent vector meson. The spin density matrix elements and polarization asymmetry of the vector meson decay will be extracted as functions of the vector meson production angle θcm and the center-of-mass energy √ s in the center-of-mass frame. These measurements will expedite the search for baryon resonance contributions, and furthermore, will yield new physics information on diffractive, t- and u-channel processes. Our approved experiments will increase the world’s data set by three orders of magnitude.Fototvorba ω i ρ mezona na protonima snopom linearno polariziranih fotona će se rabiti za odvajanje rezonantne tvorbe bariona od procesa izmjena t kvarkova pri energijama 1,72 do 2,24 GeV u Hali B u Jeffersonovom laboratoriju. Očekuje se da su ωN i ρN kanali važne grane za barionske rezonancije. Doprinos izmjene t-kanalom može se razdvojiti samo upotrebom linearno polariziranih fotona. Mjerenja će se raditi linearno polariziranim snopom fotona proizvedenim odobrenim sustavom “Coherent Bremsstrahlung Facility”, a mjerit će se asimetrija kao i matrični elementi spinske gustoće u raspadu spin-0 mezona roditeljskog vektorskog mezona. Matrični elementi spinske gustoće i polarizacijska asimetrija u raspadu vektorskih mezona će se izvesti kao funkcije kuta tvorbe θcm i energije u centru-mase √ s u sustavu centra-mase. Ta će mjerenja ubrzati potragu za doprinosima barionskih rezonancija, te nadalje, dati fizičke podatke o difraktivnim procesima u t- i u-kanalnim procesima. Ova odobrena mjerenja povećat će skup svjetskih podataka za tri reda veličine

Traganje za nedostajućim barionima snopom linearno polariziranog zračenja

The photoproduction of ω and ρ mesons from protons with a beam of linearlypolarized photons will be used to decouple baryon resonance production from texchange processes in the center-of-mass energy regime of 1.72 to 2.24 GeV at Hall B of Jefferson Lab. Both the ωN and ρN channels are expected to be a significant branch for baryon resonances. t-channel exchange contributions can only be disentangled by the use of a linearly-polarized photon beam. The measurement will employ a linearly-polarized beam of photons, produced by the approved Coherent Bremsstrahlung Facility, to measure the beam asymmetry as well as the spin density matrix elements of the decay spin-0 mesons of the parent vector meson. The spin density matrix elements and polarization asymmetry of the vector meson decay will be extracted as functions of the vector meson production angle θcm and the center-of-mass energy √ s in the center-of-mass frame. These measurements will expedite the search for baryon resonance contributions, and furthermore, will yield new physics information on diffractive, t- and u-channel processes. Our approved experiments will increase the world’s data set by three orders of magnitude.Fototvorba ω i ρ mezona na protonima snopom linearno polariziranih fotona će se rabiti za odvajanje rezonantne tvorbe bariona od procesa izmjena t kvarkova pri energijama 1,72 do 2,24 GeV u Hali B u Jeffersonovom laboratoriju. Očekuje se da su ωN i ρN kanali važne grane za barionske rezonancije. Doprinos izmjene t-kanalom može se razdvojiti samo upotrebom linearno polariziranih fotona. Mjerenja će se raditi linearno polariziranim snopom fotona proizvedenim odobrenim sustavom “Coherent Bremsstrahlung Facility”, a mjerit će se asimetrija kao i matrični elementi spinske gustoće u raspadu spin-0 mezona roditeljskog vektorskog mezona. Matrični elementi spinske gustoće i polarizacijska asimetrija u raspadu vektorskih mezona će se izvesti kao funkcije kuta tvorbe θcm i energije u centru-mase √ s u sustavu centra-mase. Ta će mjerenja ubrzati potragu za doprinosima barionskih rezonancija, te nadalje, dati fizičke podatke o difraktivnim procesima u t- i u-kanalnim procesima. Ova odobrena mjerenja povećat će skup svjetskih podataka za tri reda veličine

Measuring Neutrino Oscillations with Nuclear Reactors

Since the first direct observations of antineutrino events by Reines and Cowan in the 1950's [1], nuclear reactors have been an important tool in the study of neutrino properties. More recently, the study of neutrino oscillations has been a very active area of research. The pioneering observation of oscillations by the KamLAND experiment has provided crucial information on the neutrino mixing matrix. New experiments to study the remaining unknown mixing angle are currently under development. These recent studies and potential future developments will be discussed

Gluon Vortices and Induced Magnetic Field in Compact Stars

The natural candidates for the realization of color superconductivity are the extremely dense cores of compact stars, many of which have very large magnetic fields, especially the so-called magnetars. In this paper we discuss how a color superconducting core can serve to generate and enhance the stellar magnetic field without appealing to a magnetohydrodynamic dynamo mechanism.Comment: To appear in the Proceedings of the VII Latin American Symposium on Nuclear Physics and Applications. Cusco (Peru) June 200

Magnetic Phases in Dense Quark Matter

In this paper I discuss the magnetic phases of the three-flavor color superconductor. These phases can take place at different field strengths in a highly dense quark system. Given that the best natural candidates for the realization of color superconductivity are the extremely dense cores of neutron stars, which typically have very large magnetic fields, the magnetic phases here discussed could have implications for the physics of these compact objects.Comment: Presented at VII Latin American Symposium on Nuclear Physics and Applications, El Cusco, Peru, June 200

Effects of Neutron Emission on Fragment Mass and Kinetic Energy Distribution from Thermal Neutron-Induced Fission of 235U^{235}U

The mass and kinetic energy distribution of nuclear fragments from thermal neutron-induced fission of 235U have been studied using a Monte-Carlo simulation. Besides reproducing the pronounced broadening in the standard deviation of the kinetic energy at the final fragment mass number around m = 109, our simulation also produces a second broadening around m = 125. These results are in good agreement with the experimental data obtained by Belhafaf et al. and other results on yield of mass. We conclude that the obtained results are a consequence of the characteristics of the neutron emission, the sharp variation in the primary fragment kinetic energy and mass yield curves. We show that because neutron emission is hazardous to make any conclusion on primary quantities distribution of fragments from experimental results on final quantities distributions.Comment: 4 pages, 2 figure

Hadronic Resonances from Lattice QCD

The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.Comment: 8 pages, VII Latin American Symposium on Nuclear Physics and Application

Results and Frontiers in Lattice Baryon Spectroscopy

The Lattice Hadron Physics Collaboration (LHPC) baryon spectroscopy effort is reviewed. To date the LHPC has performed exploratory Lattice QCD calculations of the low-lying spectrum of Nucleon and Delta baryons. These calculations demonstrate the effectiveness of our method by obtaining the masses of an unprecedented number of excited states with definite quantum numbers. Future work of the project is outlined.Comment: To appear in the proceedings for the VII Latin American Symposium of Nuclear Physics and Application

The Tree Inclusion Problem: In Linear Space and Faster

Given two rooted, ordered, and labeled trees $P$ and $T$ the tree inclusion problem is to determine if $P$ can be obtained from $T$ by deleting nodes in $T$. This problem has recently been recognized as an important query primitive in XML databases. Kilpel\"ainen and Mannila [\emph{SIAM J. Comput. 1995}] presented the first polynomial time algorithm using quadratic time and space. Since then several improved results have been obtained for special cases when $P$ and $T$ have a small number of leaves or small depth. However, in the worst case these algorithms still use quadratic time and space. Let $n_S$, $l_S$, and $d_S$ denote the number of nodes, the number of leaves, and the %maximum depth of a tree $S \in \{P, T\}$. In this paper we show that the tree inclusion problem can be solved in space $O(n_T)$ and time: O(\min(l_Pn_T, l_Pl_T\log \log n_T + n_T, \frac{n_Pn_T}{\log n_T} + n_{T}\log n_{T})). This improves or matches the best known time complexities while using only linear space instead of quadratic. This is particularly important in practical applications, such as XML databases, where the space is likely to be a bottleneck.Comment: Minor updates from last tim