270 research outputs found
Allelopathic activity of micropropagated Hyssopus officinalis L., Lamiaceae, water infusions
Medium Modifications of Hadron Properties and Partonic Processes
Chiral symmetry is one of the most fundamental symmetries in QCD. It is
closely connected to hadron properties in the nuclear medium via the reduction
of the quark condensate , manifesting the partial restoration of
chiral symmetry. To better understand this important issue, a number of
Jefferson Lab experiments over the past decade have focused on understanding
properties of mesons and nucleons in the nuclear medium, often benefiting from
the high polarization and luminosity of the CEBAF accelerator. In particular, a
novel, accurate, polarization transfer measurement technique revealed for the
first time a strong indication that the bound proton electromagnetic form
factors in 4He may be modified compared to those in the vacuum. Second, the
photoproduction of vector mesons on various nuclei has been measured via their
decay to e+e- to study possible in-medium effects on the properties of the rho
meson. In this experiment, no significant mass shift and some broadening
consistent with expected collisional broadening for the rho meson has been
observed, providing tight constraints on model calculations. Finally, processes
involving in-medium parton propagation have been studied. The medium
modifications of the quark fragmentation functions have been extracted with
much higher statistical accuracy than previously possible.Comment: to appear in J. Phys.: Conf. Proc. "New Insights into the Structure
of Matter: The First Decade of Science at Jefferson Lab", eds. D.
Higinbotham, W. Melnitchouk, A. Thomas; added reference
Search for {\eta}'(958)-nucleus bound states by (p,d) reaction at GSI and FAIR
The mass of the {\eta}' meson is theoretically expected to be reduced at
finite density, which indicates the existence of {\eta}'-nucleus bound states.
To investigate these states, we perform missing-mass spectroscopy for the (p,
d) reaction near the {\eta}' production threshold. The overview of the
experimental situation is given and the current status is discussed.Comment: 6 pages, 3 figures; talk at II Symposium on applied nuclear physics
and innovative technologies, September 24th - 27th, 2014, Jagiellonian
University, Krak\'ow Poland; to appear in Acta Physica Polonica
Spectroscopy of -nucleus bound states at GSI and FAIR --- very preliminary results and future prospects ---
The possible existence of \eta'-nucleus bound states has been put forward
through theoretical and experimental studies. It is strongly related to the
\eta' mass at finite density, which is expected to be reduced because of the
interplay between the anomaly and partial restoration of chiral
symmetry. The investigation of the C(p,d) reaction at GSI and FAIR, as well as
an overview of the experimental program at GSI and future plans at FAIR are
discussed.Comment: 7 pages, 3 figures; talk at the International Conference on Exotic
Atoms and Related Topics (EXA2014), Vienna, Austria, 15-19 September 2014. in
Hyperfine Interactions (2015
MesonNet 2013 International Workshop. Mini-proceedings
The mini-proceedings of the MesonNet 2013 International Workshop held in
Prague from June 17th to 19th, 2013, are presented. MesonNet is a research
network within EU HadronPhysics3 project (1/2012 -- 12/2014). The web page of
the conference, which contains all talks, can be found at
http://ipnp.mff.cuni.cz/mesonnet13Comment: 106 pages, 53 contributions. Mini-proceedings of the MesonNet 2013
International Workshop. Editors: K. Kampf, A. Kupsc, and P. Masjua
Experimental constraints on the -nucleus real potential
In a search for mesic states, the production of -mesons in
coincidence with forward going protons has been studied in photon induced
reactions on C for incident photon energies of 1250 - 3100 MeV. The
pairs from decays of bound or quasi-free -mesons have
been measured with the CBELSA/TAPS detector system in coincidence with protons
registered in the MiniTAPS forward array. Structures in the total energy
distribution of the pairs, which would indicate the population
and decay of bound B states, are not observed. The
cross section of 0.3 nb/MeV/sr observed in the bound state energy regime
between -100 and 0 MeV may be accounted for by yield leaking into the bound
state regime because of the large in-medium width of the -meson. A
comparison of the measured total energy distribution with calculations suggests
the real part of the B potential to be small and only
weakly attractive with 35(stat) 20(syst) MeV
in contrast to some theoretical predictions of attractive potentials with a
depth of 100 - 150 MeV.Comment: 13 pages, 8 figure
Modification of the -Meson Lifetime in Nuclear Matter
The photo production of mesons on the nuclei C, Ca, Nb and Pb has
been measured using the Crystal Barrel/TAPS detector at the ELSA tagged photon
facility in Bonn. The dependence of the meson cross section on the
nuclear mass number has been compared with three different types of models, a
Glauber analysis, a BUU analysis of the Giessen theory group and a calculation
by the Valencia theory group. In all three cases, the inelastic width
is found to be at normal nuclear matter density for an
average 3-momentum of 1.1 GeV/c. In the restframe of the meson, this
inelastic width corresponds to a reduction of the lifetime by
a factor . For the first time, the momentum dependent N
cross section has been extracted from the experiment and is in the range of 70
mb.Comment: 5 pages, 4 figure
The {\eta}'-carbon potential at low meson momenta
The production of mesons in coincidence with forward-going
protons has been studied in photon-induced reactions on C and on a
liquid hydrogen (LH) target for incoming photon energies of 1.3-2.6 GeV at
the electron accelerator ELSA. The mesons have been identified
via the decay
registered with the CBELSA/TAPS detector system. Coincident protons have been
identified in the MiniTAPS BaF array at polar angles of . Under these kinematic constraints the
mesons are produced with relatively low kinetic energy (
150 MeV) since the coincident protons take over most of the momentum of the
incident-photon beam. For the C-target this allows the determination of the
real part of the -carbon potential at low meson momenta by
comparing with collision model calculations of the kinetic energy
distribution and excitation function. Fitting the latter data for
mesons going backwards in the center-of-mass system yields a potential depth of
V = (44 16(stat)15(syst)) MeV, consistent with earlier
determinations of the potential depth in inclusive measurements for average
momenta of 1.1 GeV/. Within the experimental
uncertainties, there is no indication of a momentum dependence of the
-carbon potential. The LH data, taken as a reference to check
the data analysis and the model calculations, provide differential and integral
cross sections in good agreement with previous results for
photoproduction off the free proton.Comment: 9 pages, 13 figures. arXiv admin note: text overlap with
arXiv:1608.0607
Measurement of the Beam Asymmetry in the Forward Direction for pi0 Photoproduction
Photoproduction of neutral pions has been studied with the CBELSA/TAPS
detector for photon energies between 0.92 and 1.68~GeV at the electron
accelerator ELSA. The beam asymmetry~ has been extracted for of the ~meson and for . The new beam asymmetry data improve the world database for
photon energies above 1.5~GeV and, by covering the very forward region, extend
previously published data for the same reaction by our collaboration. The
angular dependence of shows overall good agreement with the SAID
parameterization.Comment: 11 pages, 10 figures, published in Phys. Rev. C, included LEPS data
and MAID 2007 predictions for comparison with our dat
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