221 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.
Transitions between levels of a quantum bouncer induced by a noise-like perturbation
The probability of transition between levels of a quantum bouncer, induced by
a noise-like perturbation, is calculated. The results are applied to two
sources of noise (vibrations and mirror surface waviness) which might play an
important role in future GRANIT experiment, aiming at precision studies of/with
the neutron quantum bouncer
Magnetic hybrid Pd/Fe-oxide nanoparticles meet the demands for ablative thermo-brachytherapy
Objective: To investigate the potential of hybrid Pd/Fe-oxide magnetic nanoparticles designed for thermo-brachytherapy of breast cancer, considering their specific loss power (SLP) and clinical constraints in the applied magnetic field. Methods: Hybrid nanoparticles consisting of palladium-core and iron oxide shell of increasing thickness, were suspended in water and their SLPs were measured at varying magnetic fields (12–26 mT peak) and frequencies (50–730 kHz) with a commercial alternating magnetic field generator (magneTherm™ Digital, nanoTherics Ltd.). Results: Validation of the heating device used in this study with commercial HyperMag-C nanoparticles showed a small deviation (±4%) over a period of 1 year, confirming the reliability of the method. The integration of dual thermometers, one in the center and one at the bottom of the sample vial, allowed monitoring of homogeneity of the sample suspensions. SLPs measurements on a series of nanoparticles of increasing sizes showed the highest heating for the diameter of 21 nm (SLP = 225 W/g) at the applied frequencies of 346 and 730 kHz. No heating was observed for the nanoparticles with the size <14 nm, confirming the importance of the size-parameter. The heating ability of the best performing Pd/Fe-oxide-21 was calculated to be sufficient to ablate tumors with a radius ±4 and 12 mm using 10 and 1 mg/mL nanoparticle concentration, respectively. Conclusions: Nanoparticles consisting of non-magnetic palladium-core and magnetic iron oxide shell are suitable for magnetic hyperthermia/thermal ablation under clinically safe conditions of 346 kHz and 19.1 mT, with minimal eddy current effects in combination with maximum SLP.</p
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
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
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
Gravitational depolarization of ultracold neutrons: comparison with data
We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin-depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data
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.)
TUmor-volume to breast-volume RAtio for improving COSmetic results in breast cancer patients (TURACOS); a randomized controlled trial
Background: Cosmetic result following breast conserving surgery (BCS) for cancer influences quality of life and psychosocial functioning in breast cancer patients. A preoperative prediction of expected cosmetic result following BCS is not (yet) standard clinical practice and therefore the choice for either mastectomy or BCS is still subjective. Recently, we showed that tumour volume to breast volume ratio as well as tumour location in the breast are independent predictors of superior cosmetic result following BCS. Implementation of a prediction model including both factors, has not been studied in a prospective manner. This study aims to improve cosmetic outcome by implementation of a prediction model in the treatment decision making for breast cancer patients opting for BCS. Methods/design: Multicentre, single-blinded, randomized controlled trial comparing standard preoperative work-up to a preoperative work-up with addition of the prediction model. Tumour volume to bre
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