344 research outputs found
Three- and Four-Body Scattering Calculations including the Coulomb Force
The method of screening and renormalization for including the Coulomb
interaction in the framework of momentum-space integral equations is applied to
the three- and four-body nuclear reactions. The Coulomb effect on the
observables and the ability of the present nuclear potential models to describe
the experimental data is discussed.Comment: Proceedings of the Critical Stability workshop, Erice, Sicily,
October 2008, to be published in Few-Body System
Two-meson cloud contribution to the baryon antidecuplet self-energy
We study the self-energy of the SU(3) antidecuplet coming from two-meson
virtual clouds. Assuming that the exotic Theta+ belongs to an antidecuplet
representation with N(1710) as nucleon partner, we derive effective Lagrangians
that describe the decay of N(1710) into N pi pi with two pions in s- or p-wave.
It is found that the self-energies for all members of the antidecuplet are
attractive, and the larger strangeness particle is more bound. From two-meson
cloud, we obtain about 20 % of the empirical mass splitting between states with
different strangeness.Comment: 4 pages, 2 figures, 1 table, Talk given at the 10th International
Conference on Baryons (Baryons04), Palaiseau (France), October 25-29, 200
Today's View on Strangeness
There are several different experimental indications, such as the
pion-nucleon sigma term and polarized deep-inelastic scattering, which suggest
that the nucleon wave function contains a hidden s bar s component. This is
expected in chiral soliton models, which also predicted the existence of new
exotic baryons that may recently have been observed. Another hint of hidden
strangeness in the nucleon is provided by copious phi production in various N
bar N annihilation channels, which may be due to evasions of the
Okubo-Zweig-Iizuka rule. One way to probe the possible polarization of hidden s
bar s pairs in the nucleon may be via Lambda polarization in deep-inelastic
scattering.Comment: 8 pages LaTeX, 10 figures, to appear in the Proceedings of the
International Conference on Parity Violation and Hadronic Structure,
Grenoble, June 200
Longitudinal scaling property of the charge balance function in Au + Au collisions at 200 GeV
We present measurements of the charge balance function, from the charged
particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au
collisions at 200 GeV using the STAR detector at RHIC. We observe that the
balance function is boost-invariant within the pseudorapidity coverage [-1.3,
1.3]. The balance function properly scaled by the width of the observed
pseudorapidity window does not depend on the position or size of the
pseudorapidity window. This scaling property also holds for particles in
different transverse momentum ranges. In addition, we find that the width of
the balance function decreases monotonically with increasing transverse
momentum for all centrality classes.Comment: 6 pages, 3 figure
Inclusive production of protons, anti-protons and neutrons in p+p collisions at 158 GeV/c beam momentum
New data on the production of protons, anti-protons and neutrons in p+p
interactions are presented. The data come from a sample of 4.8 million
inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c
beam momentum. The charged baryons are identified by energy loss measurement in
a large TPC tracking system. Neutrons are detected in a forward hadronic
calorimeter. Inclusive invariant cross sections are obtained in intervals from
0 to 1.9 GeV/c (0 to 1.5 GeV/c) in transverse momentum and from -0.05 to 0.95
(-0.05 to 0.4) in Feynman x for protons (anti-protons), respectively. pT
integrated neutron cross sections are given in the interval from 0.1 to 0.9 in
Feynman x. The data are compared to a wide sample of existing results in the
SPS and ISR energy ranges as well as to proton and neutron measurements from
HERA and RHIC.Comment: 69 pages, 72 figure
Dioctahedral mixed K-Na-micas and paragonite in diagenetic to low-temperature metamorphic terrains: bulk rock chemical, thermodynamic and textural constraints
Abstract
Metamorphic mineral assemblages in low-temperature metaclastic rocks often contain paragonite and/or its precursor metastable phase (mixed K-Na-white mica). Relationships between the bulk rock major element chemistries and the formation of paragonite at seven localities from Central and SE-Europe were studied, comparing the bulk chemical characteristics with mineral assemblage, mineral chemical and metamorphic petrological data. Considerable overlaps between the projection fields of bulk chemistries of the Pg-free and Pg-bearing metaclastic rocks indicate significant differences between the actual (as analyzed) and effective bulk chemical compositions. Where inherited, clastic, inert phases/constituents were excluded, it was found that a decrease in Na/(Na+Al*) and in K/(K+Al*) ratios of rocks favors the formation and occurrence of Pg and its precursor phases (Al* denotes here the atomic quantity of aluminum in feldspars, white micas and “pure” hydrous or anhydrous aluminosilicates). In contrast to earlier suggestions, enrichment in Na and/or an increase in Na/K ratio by themselves do not lead to formation of paragonite. Bulk rock chemistries favorable to formation of paragonite and its precursor phases are characterized by enrichment in Al and depletion in Na, K, Ca (and also, Mg and Fe2+). Such bulk rock chemistries are characteristic of chemically “mature” (strongly weathered) source rocks of the pelites and may also be formed by synand post-sedimentary magmatism-related hydrothermal (leaching) activity. What part of the whole rock is active in determining the effective bulk chemistry was investigated by textural examination of diagenetic and anchizone-grade samples. It is hypothesized that although solid phases act as local sources and sinks, transport of elements such as Na through the grain boundaries have much larger communication distances. Sodium-rich white micas nucleate heterogeneously using existing phyllosilicates as templates and are distributed widely on the thin section scale. The results of modeling by THERMOCALC suggest that paragonite preferably forms at higher pressures in low-T metapelites. The stability fields of Pg-bearing assemblages increase, the Pg-in reaction line is shifted towards lower pressures, while the stability field of the Chl-Ms-Ab-Qtz assemblage decreases and is shifted towards higher temperatures with increasing Al* content and decreasing Na/(Na+Al*) and K/(K+Al*) ratios
Search for a pentaquark decaying to Cascade- pi-
We present a search for a pentaquark decaying strongly to in
collisions at a center-of-mass energy up to 25 GeV/c^2. Finding no
evidence for such a state in the mass range of 1480 MeV/c^2 to 2400 MeV/c^2, we
set limits on the yield and on the cross section times branching ratio relative
to .Comment: Accepted by Physics Letters
Multiplicity dependence of inclusive J/psi production at midrapidity in pp collisions at root s=13 TeV
Measurements of the inclusive J/psi yield as a function of charged-particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 13 TeV with ALICE at the LHC are reported. The J/psi meson yield is measured at midrapidity (vertical bar y vertical bar <0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (vertical bar eta vertical bar <1) and at forward rapidity (-3.7 <eta <-1.7 and 2.8 <eta <5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/psi yield with normalized dN(ch)/d eta is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively. (C) 2020 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe
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