231 research outputs found
Search for the Photoexcitation of Exotic Mesons in the π+π+π− System
A search for exotic mesons in the π+π+π− system photoproduced by the charge exchange reaction γp→π+π+π−(n) was carried out by the CLAS Collaboration at Jefferson Lab. A tagged-photon beam with energies in the 4.8 to 5.4 GeV range, produced through bremsstrahlung from a 5.744 GeV electron beam, was incident on a liquid-hydrogen target. A partial wave analysis was performed on a sample of 83 000 events, the highest such statistics to date in this reaction at these energies. The main objective of this study was to look for the photoproduction of an exotic JPC=1−+ resonant state in the 1 to 2 GeV mass range. Our partial wave analysis shows production of the a2(1320) and the π2(1670) mesons, but no evidence for the a1(1260), nor the π1(1600) exotic state at the expected levels. An upper limit of 13.5 nb is determined for the exotic π1(1600) cross section, less than 2% of the a2(1320) production
Search for the Photoexcitation of Exotic Mesons in the \u3ci\u3eπ\u3c/i\u3e​\u3csup\u3e+\u3c/sup\u3e\u3ci\u3eπ\u3c/i\u3e\u3csup\u3e​+\u3c/sup\u3e\u3ci\u3eπ\u3c/i\u3e\u3csup\u3e-\u3c/sup\u3e System
A search for exotic mesons in the π+π+π- system photoproduced by the charge exchange reaction γp → π+π+π- was carried out by the CLAS Collaboration at Jefferson Lab. A tagged-photon beam with energies in the 4.8 to 5.4 GeV range, produced through bremsstrahlung from a 5.744 GeV electron beam, was incident on a liquid-hydrogen target. A partial wave analysis was performed on a sample of 83 000 events, the highest such statistics to date in this reaction at these energies. The main objective of this study was to look for the photoproduction of an exotic JPC = 1-+ resonant state in the 1 to 2 GeV mass range. Our partial wave analysis shows production of the a2(1320) and the π2(1670) mesons, but no evidence for the a1(1260), nor the π1(1600) exotic state at the expected levels. An upper limit of 13.5 nb is determined for the exotic π1(1600) cross section, less than 2% of the a2(1320) production
Magnetic fluctuations in frustrated Laves hydrides R(Mn_{1-x}Al_{x})_{2}H_{y}
By neutron scattering, we have studied the spin correlations and spin
fluctuations in frustrated Laves hydrides, where magnetic disorder sets in the
topologically frustrated Mn lattice. Below the transition towards short range
magnetic order, static spin clusters coexist with fluctuating and alsmost
uncorrelated spins. The magnetic response shows a complexe lineshape, connected
with the presence of the magnetic inhomogeneities. Its analysis shows the
existence of two different processes, relaxation and local excitations, for the
spin fluctuations below the transition. The paramagnetic fluctuations are
discussed in comparison with classical spin glasses, cluster glasses, and non
Fermi liquid itinerant magnets
Determination of organic pollutants in sediment & some commercial species biota from eastern waters of Hormozgan province
This survey was conducted to determine the petroleum pollutants in sediment & some commercial aquatics of species in eastern waters of Hormozgan province during 2006-2008. We have selected 3 stations at 5, 10 and 20 meters depth in each of Sirik, Kuh-e-mobarak and Jask area. The selected biota were Penaeus indicus & Psettodes eruemi.Selected components of PAHs in sediment & biota samples were: Naphthalene (Na), Acenaphthylene (AcPY), Acenaphthene (AcP), Fluorene (FL), Phenantheren (PHEN), Anthracene (AN), Fluornthene (FLUR), Pyrene (PY), Benzo(a)anthracene (BaA), Chrysene(CHRY), Benzo(b) fluoranthene (BaF), Benzo(k)fluoranthene (BkF), Benzo(a) pyrene (BaP), Dibenzo(a,h)anthrancene (dBAn), Benzo(ghi)perylene (BPe), Indeno (1,2.3-cd)pyrene (IcdP) . Our results were: Based to our results Bioaccumulation of PAHs didn't relate to sex and length of selected biota. Percent of naphthalene as a PAH with two rings has a significant difference against other PAHs in all areas. High ratio of HPAH to LPAH, show the combustion source of PAHs. Values for total PAHs at shrimp in Sirik, Kuh-e- mobarak & Jask area were 349.9 ±236.7, 809.1± 605.4 & 1015±1300.1 ng/g. Values for total PAHs at Psettodes eruemi, in Sirik, Kuh-e- mobarak & Jask area were 494 ±460.8, 1465.3±1678.2 and 292.3±400.7 ng/g respectively. In shrimp samples, the values for total PAHs had significant difference between Jask & Kuh e-mobarak, whereas for Psettodes eruemi, the significant difference was observed in Jask & Kuh-e-mobark. In sediment, concentration of total PAHs and their components didn't show any significant difference with area and depth of sampling at 95% confidence level. Average concentration of total PAHs and their components with 2, 3, 4, 5and 6 rings were 279.7±117.4, 4.5± 9.3, 6.2±7.1, 5.4±1.4, 263.6±113.9 respectively. Based to NOAA standards, pollution level of sediment is lower than ERL values
Measurement of the Muon Decay Parameter delta
The muon decay parameter delta has been measured by the TWIST collaboration.
We find delta = 0.74964 +- 0.00066(stat.) +- 0.00112(syst.), consistent with
the Standard Model value of 3/4. This result implies that the product Pmuxi of
the muon polarization in pion decay, Pmu, and the muon decay parameter xi falls
within the 90% confidence interval 0.9960 < Pmuxi < xi < 1.0040. It also has
implications for left-right-symmetric and other extensions of the Standard
Model.Comment: Extended to 5 pages. Referee's comments answere
Confirmation of a pi_1^0 Exotic Meson in the \eta \pi^0 System
The exclusive reaction , at 18 GeV has been studied with a partial wave analysis on a sample
of 23~492 events from BNL experiment E852. A mass-dependent fit
is consistent with a resonant hypothesis for the wave, thus providing
evidence for a neutral exotic meson with , a mass of MeV, and a width of MeV. New
interpretations of the meson exotics in neutral system observed in
E852 and Crystal Barrel experiments are discussed.Comment: p3, rewording the paragraph (at the bottom) about the phase
variations. p4, rewording paragrath "The second method ..." . p4, at the
bottom of paragrath "The third method ..." added consistent with the results
of methods 1 and 2
Search for Exotic Mesons in pi- P Interactions at 18 GeV/c
The recent search for non mesons in interactions at
Brookhaven National Laboratory is summarized. Many final states such as , , , , , ,
which are favored decay modes of exotics, are under investigation.Comment: 9 pages, PostScript, Presented at the International School of Nuclear
Physics, Erice, Sicily, Italy, September 199
Exotic Meson Production in the System observed in the Reaction at 18 GeV/c
This letter reports results from the partial wave analysis of the
final state in collisions at 18GeV/c.
Strong evidence is observed for production of two mesons with exotic quantum
numbers of spin, parity and charge conjugation, in the decay
channel . The mass MeV/c^2 and
width MeV/c^2 of the first state are consistent
with the parameters of the previously observed . The second
resonance with mass MeV/c^2 and width MeV/c^2 agrees very well with predictions from theoretical
models. In addition, the presence of is confirmed with mass MeV/c^2 and width MeV/c^2
and a new state, , is observed with mass
MeV/c^2 and width MeV/c^2. The decay properties of
these last two states are consistent with flux tube model predictions for
hybrid mesons with non-exotic quantum numbers
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