7,409 research outputs found
Rates for the reactions antiproton-proton --> pi phi and gamma phi
We study antiproton-proton annihilation at rest into and
. Rescattering by and
for states is sizable, of
order in the branching ratio, but
smaller than experiment. For the
rescattering contributions are negligible, but the channel is well
explained by a intermediate state combined with vector meson
dominance.Comment: 12 pages, plain latex, 2 postscript figures available upon request,
PSI-PR-93-2
Scalar Quarkonium Masses and Mixing with the Lightest Scalar Glueball
We evaluate the continuum limit of the valence (quenched) approximation to
the mass of the lightest scalar quarkonium state, for a range of different
quark masses, and to the mixing energy between these states and the lightest
scalar glueball. Our results support the interpretation of as
composed mainly of the lightest scalar glueball.Comment: 14 pages of Latex, 5 PostScript figure
Study of nuclear recoils in liquid argon with monoenergetic neutrons
For the development of liquid argon dark matter detectors we assembled a
setup in the laboratory to scatter neutrons on a small liquid argon target. The
neutrons are produced mono-energetically (E_kin=2.45 MeV) by nuclear fusion in
a deuterium plasma and are collimated onto a 3" liquid argon cell operating in
single-phase mode (zero electric field). Organic liquid scintillators are used
to tag scattered neutrons and to provide a time-of-flight measurement. The
setup is designed to study light pulse shapes and scintillation yields from
nuclear and electronic recoils as well as from {\alpha}-particles at working
points relevant to dark matter searches. Liquid argon offers the possibility to
scrutinise scintillation yields in noble liquids with respect to the
populations of the two fundamental excimer states. Here we present experimental
methods and first results from recent data towards such studies.Comment: 9 pages, 8 figures, proceedings of TAUP 2011, to be published in
Journal of Physics: Conference Series (JCPS
Estimating sigma-meson couplings from D \to 3\pi decays
Using recent experimental evidence from E791 on the sigma meson in D \to 3\pi
decays, we study the relevant couplings in D \to \sigma \pi and \sigma \to \pi\
pi within the accepted theoretical framework for non leptonic D decays. We also
review the linear sigma model, finding that it gives a description which is
consistent with the experimental data.Comment: 6 pages, no figures. Final version accepted for publication as a
Brief Report in Physical Review
The multiplets of finite width 0++ mesons and encounters with exotics
Complex-mass (finite-width) nonet and decuplet are investigated by
means of exotic commutator method. The hypothesis of vanishing of the exotic
commutators leads to the system of master equations (ME). Solvability
conditions of these equations define relations between the complex masses of
the nonet and decuplet mesons which, in turn, determine relations between the
real masses (mass formulae), as well as between the masses and widths of the
mesons. Mass formulae are independent of the particle widths. The masses of the
nonet and decuplet particles obey simple ordering rules. The nonet mixing angle
and the mixing matrix of the isoscalar states of the decuplet are completely
determined by solution of ME; they are real and do not depend on the widths.
All known scalar mesons with the mass smaller than (excluding
) and one with the mass belong to two
multiplets: the nonet and the
decuplet .
It is shown that the famed anomalies of the and widths
arise from an extra "kinematical" mechanism, suppressing decay, which is not
conditioned by the flavor coupling constant. Therefore, they do not justify
rejecting the structure of them. A unitary singlet state (glueball)
is included into the higher lying multiplet (decuplet) and is divided among the
and mesons. The glueball contents of these particles
are totally determined by the masses of decuplet particles. Mass ordering rules
indicate that the meson does not mix with the nonet particles.Comment: 22 pp, 1 fig, a few changes in argumentation, conclusions unchanged.
Final version to appear in EPJ
Jets associated with Z^0 boson production in heavy-ion collisions at the LHC
The heavy ion program at the LHC will present unprecedented opportunities to
probe hot QCD matter, that is, the quark gluon plasma (QGP). Among these
exciting new probes are high energy partons associated with the production of a
Z^0 boson, or Z^0 tagged jets. Once produced, Z^0 bosons are essentially
unaffected by the strongly interacting medium produced in heavy-ion collisions,
and therefore provide a powerful signal of the initial partonic energy and
subsequent medium induced partonic energy loss. When compared with theory,
experimental measurements of Z^0 tagged jets will help quantify the jet
quenching properties of the QGP and discriminate between different partonic
energy loss formalisms. In what follows, I discuss the advantages of tagged
jets over leading particles, and present preliminary results of the production
and suppression of Z^0 tagged jets in relativistic heavy-ion collisions at LHC
energies using the Guylassy-Levai-Vitev (GLV) partonic energy loss formalism.Comment: To appear in the proceedings of the 2010 Winter Workshop on Nuclear
Dynamics, which was held in Ocho Rios, Jamaica, mon
Seawater acidification more than warming presents a challenge for two Antarctic macroalgal-associated amphipods
Elevated atmospheric pCO2 concentrations are triggering seawater pH reductions and seawater temperature increases along the western Antarctic Peninsula (WAP). These factors in combination have the potential to influence organisms in an antagonistic, additive, or synergistic manner. The amphipods Gondogeneia antarctica and Paradexamine fissicauda represent prominent members of macroalgal-associated mesograzer assemblages of the WAP. Our primary objective was to investigate amphipod behavioral and physiological responses to reduced seawater pH and elevated temperature to evaluate potential cascading ecological impacts. For 90 d, amphipods were exposed to combinations of seawater conditions based on present ambient (pH 8.0, 1.5°C) and predicted end-of-century conditions (pH 7.6, 3.5°C). We recorded survival, molt frequency, and macroalgal consumption rates as well as change in wet mass and proximate body composition (protein and lipid). Survival for both species declined significantly at reduced pH and co-varied with molt frequency. Consumption rates in G. antarctica were significantly higher at reduced pH and there was an additive pH-temperature effect on consumption rates in P. fissicauda. Body mass was reduced for G. antarctica at elevated temperature, but there was no significant effect of pH or temperature on body mass in P. fissicauda. Exposure to the pH or temperature levels tested did not induce significant changes in whole body biochemical composition of G. antarctica, but exposure to elevated temperature resulted in a significant increase in whole body protein content of P. fissicauda. Our study indicates that while elevated temperature causes sub-lethal impacts on both species of amphipods, reduced pH causes significant mortality
Tests of silicon sensors for the CMS pixel detector
The tracking system of the CMS experiment, currently under construction at
the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland), will include a
silicon pixel detector providing three spacial measurements in its final
configuration for tracks produced in high energy pp collisions. In this paper
we present the results of test beam measurements performed at CERN on
irradiated silicon pixel sensors. Lorentz angle and charge collection
efficiency were measured for two sensor designs and at various bias voltages.Comment: Talk presented at 6th International Conference on Large Scale
Applications and Radiation Hardness of Semiconductor Detectors, September
29-October 1, 2003, Firenze, Italy. Proceedings will be published in Nuclear
Instr. & Methods in Phys. Research, Section
Scintillation efficiency of liquid argon in low energy neutron-argon scattering
Experiments searching for weak interacting massive particles with noble gases
such as liquid argon require very low detection thresholds for nuclear recoils.
A determination of the scintillation efficiency is crucial to quantify the
response of the detector at low energy. We report the results obtained with a
small liquid argon cell using a monoenergetic neutron beam produced by a
deuterium-deuterium fusion source. The light yield relative to electrons was
measured for six argon recoil energies between 11 and 120 keV at zero electric
drift field.Comment: 21 pages, 19 figures, 4 table
A Study in Depth of f0(1370)
Claims have been made that f0(1370) does not exist. The five primary sets of
data requiring its existence are refitted. Major dispersive effects due to the
opening of the 4pi threshold are included for the first time; the sigma -> 4pi
amplitude plays a strong role. Crystal Barrel data on pbar-p -> 3pizero at rest
require f0(1370) signals of at least 32 and 33 standard deviations in 1S0 and
3P1 annihilation respectively. Furthermore, they agree within 5 MeV for mass
and width. Data on pbar-p -> eta-eta-pizero agree and require at least a 19
standard deviation contribution. This alone is sufficient to demonstrate the
existence of f0(1370). BES II data for J/Psi -> phi-pi-pi contain a visible
f0(1370) signal > 8 standard devations. In all cases, a resonant phase
variation is required. The possibility of a second pole in the sigma amplitude
due to the opening of the 4pi channel is excluded. Cern-Munich data for pi-pi
elastic scattering are fitted well with the inclusion of some mixing between
sigma, f0(1370) and f0(1500). The pi-pi widths for f2(1565), rho3(1690),
rho3(1990) and f4(2040) are determined.Comment: 25 pages, 22 figures. Typos corrected in Eqs 2 and 7. Introduction
rewritten. Conclusions unchange
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