280 research outputs found
New Results for Light Gravitinos at Hadron Colliders - Tevatron Limits and LHC Perspectives
We derive Feynman rules for the interactions of a single gravitino with
(s)quarks and gluons/gluinos from an effective supergravity Lagrangian in
non-derivative form and use them to calculate the hadroproduction cross
sections and decay widths of single gravitinos. We confirm the results obtained
previously with a derivative Lagrangian as well as those obtained with the
non-derivative Lagrangian in the high-energy limit and elaborate on the
connection between gauge independence and the presence of quartic vertices. We
perform extensive numerical studies of branching ratios, total cross sections,
and transverse-momentum spectra at the Tevatron and the LHC. From the latest
CDF monojet cross section limit, we derive a new and robust exclusion contour
in the gravitino-squark/gluino mass plane, implying that gravitinos with masses
below to eV are excluded for
squark/gluino-masses below 200 and 500 GeV, respectively. These limits are
complementary to the one obtained by the CDF collaboration,
eV, under the assumption of infinitely heavy squarks and gluinos. For the LHC,
we conclude that SUSY scenarios with light gravitinos will lead to a striking
monojet signal very quickly after its startup.Comment: 30 pages, 12 figures. Tevatron limit improved and unitarity limit
included. Version to be published in Phys. Rev.
3D Finite Element Modeling of Electromagnetic Forming Processes
In the electromagnetic forming process (EMF, also known as magnetic pulse forming) the metal is deformed by applying a pressure generated by an intense, transient magnetic field. A great deal of research and investigation efforts are needed for gaining better understanding on the deformation mechanism in order to develop a suitable forming strategy and equipment. One way to reach this target is to employ suitable FE software to model the process. This investigation was partly conducted in the framework of a European project called EMF (G3RD-CT-2002-00798). The first part of the paper presents the relevant physical phenomena which govern the EMF process and their interactions. The physical coupling principle as well as the required numerical models are also established. In the second section some cases for which the so developed code can be used for virtual testing is presented for validation. Finally, numerical results are compared with experiments on a 3D model, highlighting the interest of numerical modeling for process improvements
Effect of Platelet-activating Factor on in vitro and in vivo Interleukin-6 Production
The aim of the present study was to investigate the possible effect
of platelet-activating factor (PAF), by comparison with
interleukin-1β and polyriboinositic/polyribocytidylic (poly
I–C) acid, on IL-6 production by L 929 mouse fibroblasts. At
concentrations above 1 μM PAF, the production of IL-6 by mouse
fibroblasts was enhanced in a dose dependent fashion. At 5 μM
PAF, the peak increase (60.1 ± 19.4 U/ml) was similar to
that induced by 50 μg/ml poly I–C (60.0 ± 35.0
U/ml) and higher than the one evoked by 100 U/ml IL-1β
(3.8 ± 1.8 U/ml). The increase of 11-6 activity induced
by 5 μM PAF was maximal after a 22 h incubation period with L 929
cells. Lyso-PAF (5 μM) also increased IL-6 activity from
fibroblasts to a similar extent compared with 5 μM PAF. In
addition, the IL-6 activity induced by 5 μM PAF was still
observed when the specific PAF antagonist, BN 52021 (10 μM), was
added to the incubation medium of L 929 cells. The result suggests
that the production of IL-6 by L 929 cells evoked by PAF in
vitro is not receptor mediated. The in vivo
effect of PAF on IL-6 production was also investigated in the rat.
Two hours after intravenous injection of PAF (2 to 4 μg/kg),
a dramatic increase of IL-6 activity in rat serum was observed, this
effect being dose dependent. The increase of IL-6 induced by 3
μg/kg PAF was not observed when the animals were treated with
the PAF antagonist, BN 52021 (1 to 60 mg/kg0. These results
demonstrate that PAF modulates IL-6 production and that the in
vivo effect is receptor mediated
Probing neutron-hidden neutron transitions with the MURMUR experiment
MURMUR is a new passing-through-walls neutron experiment designed to
constrain neutron/hidden neutron transitions allowed in the context of
braneworld scenarios or mirror matter models. A nuclear reactor can act as a
hidden neutron source, such that neutrons travel through a hidden world or
sector. Hidden neutrons can propagate out of the nuclear core and far beyond
the biological shielding. However, hidden neutrons can weakly interact with
usual matter, making possible for their detection in the context of low-noise
measurements. In the present work, the novelty rests on a better background
discrimination and the use of a mass of a material - here lead - able to
enhance regeneration of hidden neutrons into visible ones to improve detection.
The input of this new setup is studied using both modelizations and
experiments, thanks to tests currently performed with the experiment at the BR2
research nuclear reactor (SCKCEN, Mol, Belgium). A new limit on the
neutron swapping probability p has been derived thanks to the measurements
taken during the BR2 Cycle 02/2019A: at 95% CL.
This constraint is better than the bound from the previous passing-through-wall
neutron experiment made at ILL in 2015, despite BR2 is less efficient to
generate hidden neutrons by a factor 7.4, thus raising the interest of such
experiment using regenerating materials.Comment: 15 pages, 8 figures, final version, accepted for publication in
European Physical Journal
Biological Markers Predictive of Invasive Recurrence in DCIS
DCIS is a heterogeneous group of non-invasive cancers of the breast characterized by various degrees of differentiation and unpredictable propensity for transformation into invasive carcinoma. We examined the expression and prognostic value of 9 biological markers with a potential role in tumor progression in 133 patients with pure DCIS treated with breast conserving surgery alone, between 1982–2000. Histology was reviewed and immunohistochemical staining was performed. Pearson correlation coefficient was used to determine the associations between markers and histopathological features. Univariate and multivariate analysis examined associations between time to recurrence and clinicopathologic features and biological markers
GRANIT project: a trap for gravitational quantum states of UCN
Previous studies of gravitationally bound states of ultracold neutrons showed
the quantization of energy levels, and confirmed quantum mechanical predictions
for the average size of the two lowest energy states wave functions.
Improvements in position-like measurements can increase the accuracy by an
order of magnitude only. We therefore develop another approach, consisting in
accurate measurements of the energy levels. The GRANIT experiment is devoted to
the study of resonant transitions between quantum states induced by an
oscillating perturbation.
According to Heisenberg's uncertainty relations, the accuracy of measurement
of the energy levels is limited by the time available to perform the
transitions. Thus, trapping quantum states will be necessary, and each source
of losses has to be controlled in order to maximize the lifetime of the states.
We discuss the general principles of transitions between quantum states, and
consider the main systematical losses of neutrons in a trap.Comment: presented in ISINN 15 seminar, Dubn
An Improved Search for the Neutron Electric Dipole Moment
A permanent electric dipole moment of fundamental spin-1/2 particles violates
both parity (P) and time re- versal (T) symmetry, and hence, also charge-parity
(CP) symmetry since there is no sign of CPT-violation. The search for a neutron
electric dipole moment (nEDM) probes CP violation within and beyond the Stan-
dard Model. The experiment, set up at the Paul Scherrer Institute (PSI), an
improved, upgraded version of the apparatus which provided the current best
experimental limit, dn < 2.9E-26 ecm (90% C.L.), by the RAL/Sussex/ILL
collaboration: Baker et al., Phys. Rev. Lett. 97, 131801 (2006). In the next
two years we aim to improve the sensitivity of the apparatus to sigma(dn) =
2.6E-27 ecm corresponding to an upper limit of dn < 5E-27 ecm (95% C.L.), in
case for a null result. In parallel the collaboration works on the design of a
new apparatus to further increase the sensitivity to sigma(dn) = 2.6E-28 ecm.Comment: APS Division for particles and fields, Conference Proceedings, Two
figure
Constraining interactions mediated by axion-like particles with ultracold neutrons
We report a new limit on a possible short range spin-dependent interaction
from the precise measurement of the ratio of Larmor precession frequencies of
stored ultracold neutrons and Hg atoms confined in the same volume. The
measurement was performed in a 1 T vertical magnetic holding field
with the apparatus searching for a permanent electric dipole moment of the
neutron at the Paul Scherrer Institute. A possible coupling between freely
precessing polarized neutron spins and unpolarized nucleons of the wall
material can be investigated by searching for a tiny change of the precession
frequencies of neutron and mercury spins. Such a frequency change can be
interpreted as a consequence of a short range spin-dependent interaction that
could possibly be mediated by axions or axion-like particles. The interaction
strength is proportional to the CP violating product of scalar and pseudoscalar
coupling constants . Our result confirms limits from complementary
experiments with spin-polarized nuclei in a model-independent way. Limits from
other neutron experiments are improved by up to two orders of magnitude in the
interaction range of m
Revised experimental upper limit on the electric dipole moment of the neutron
We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons; an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of dn=−0.21±1.82×10−26 e cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of 3.0×10−26 e cm (90% C.L.) or 3.6×10−26 e cm (95% C.L.)
Minimal Length and the Quantum Bouncer: A Nonperturbative Study
We present the energy eigenvalues of a quantum bouncer in the framework of
the Generalized (Gravitational) Uncertainty Principle (GUP) via quantum
mechanical and semiclassical schemes. In this paper, we use two equivalent
nonperturbative representations of a deformed commutation relation in the form
[X,P]=i\hbar(1+\beta P^2) where \beta is the GUP parameter. The new
representation is formally self-adjoint and preserves the ordinary nature of
the position operator. We show that both representations result in the same
modified semiclassical energy spectrum and agrees well with the quantum
mechanical description.Comment: 14 pages, 2 figures, to appear in Int. J. Theor. Phy
- …