807 research outputs found
Sneutrino-induced like sign dilepton signal with conserved R-parity
Lepton number violation could be manifest in the sneutrino sector of
supersymmetric extensions of the standard model with conserved R-parity. Then
sneutrinos decay partly into the ``wrong sign charged lepton'' final state, if
kinematically accessible. In sneutrino pair production or associated single
sneutrino production, the signal then is a like sign dilepton final state.
Under favourable circumstances, such a signal could be visible at the LHC or a
next generation linear collider for a relative sneutrino mass-splitting of
order and sneutrino width of order (1 GeV). On the
other hand, the like sign dilepton event rate at the TEVATRON is probably too
small to be observable.Comment: 19 pages, 14 Figures. Section about LSD at LHC and TEVATRON added.
Previous Title "Single sneutrino production and the wrong charged lepton
signal
Light Lepton Number Violating Sneutrinos and the Baryon Number of the Universe
Recent results of neutrino oscillation experiments point to a nonvanishing
neutrino mass. Neutrino mass models favour Majorana-type neutrinos. In such
circumstances it is natural that the supersymmetric counterpart of the
neutrino, the sneutrino, bears also lepton number violating properties. On the
other hand, the fact that the universe exhibits an asymmetry in the baryon and
antibaryon numbers poses constraints on the extent of lepton number violation
in the light sneutrino sector if the electroweak phase transition is second or
weak first order. From the requirement that the Baryon Asymmetry of the
Universe should not be washed out by sneutrino induced lepton number violating
interactions and sphalerons below the critical temperature of the electroweak
phase transition we find that the mass splitting of the light sneutrino mass
states is compatible with the sneutrino Cold Dark Matter hypothesis only for
heavy gauginos and opposite sign gaugino mass parameters.Comment: 13 pages, 4 figure
Social preferences, accountability, and wage bargaining
We assess the extent of preferences for employment in a collective wage bargaining situation with heterogeneous workers. We vary the size of the union and introduce a treatment mechanism transforming the voting game into an individual allocation task. Our results show that highly productive workers do not take employment of low productive workers into account when making wage proposals, regardless of whether insiders determine the wage or all workers. The level of pro-social preferences is small in the voting game, while it increases as the game is transformed into an individual allocation task. We interpret this as an accountability effect
Fluctuations in granular gases
A driven granular material, e.g. a vibrated box full of sand, is a stationary
system which may be very far from equilibrium. The standard equilibrium
statistical mechanics is therefore inadequate to describe fluctuations in such
a system. Here we present numerical and analytical results concerning energy
and injected power fluctuations. In the first part we explain how the study of
the probability density function (pdf) of the fluctuations of total energy is
related to the characterization of velocity correlations. Two different regimes
are addressed: the gas driven at the boundaries and the homogeneously driven
gas. In a granular gas, due to non-Gaussianity of the velocity pdf or lack of
homogeneity in hydrodynamics profiles, even in the absence of velocity
correlations, the fluctuations of total energy are non-trivial and may lead to
erroneous conclusions about the role of correlations. In the second part of the
chapter we take into consideration the fluctuations of injected power in driven
granular gas models. Recently, real and numerical experiments have been
interpreted as evidence that the fluctuations of power injection seem to
satisfy the Gallavotti-Cohen Fluctuation Relation. We will discuss an
alternative interpretation of such results which invalidates the
Gallavotti-Cohen symmetry. Moreover, starting from the Liouville equation and
using techniques from large deviation theory, the general validity of a
Fluctuation Relation for power injection in driven granular gases is
questioned. Finally a functional is defined using the Lebowitz-Spohn approach
for Markov processes applied to the linear inelastic Boltzmann equation
relevant to describe the motion of a tracer particle. Such a functional results
to be different from injected power and to satisfy a Fluctuation Relation.Comment: 40 pages, 18 figure
The Mathematical Theory of Wavelets
ABSTRACT. We present an overview of some aspects of the mathematical theory of wavelets. These notes are addressed to an audience of mathematicians familiar with only the most basic elements of Fourier Analysis. The material discussed is quite broad and covers several topics involving wavelets. Though most of the larger and more involved proofs are not included, complete references to them are provided. We do, however, present complete proofs for results that are new (in particular, this applies to a recently obtained characterization of “all ” wavelets in section 4). 1
Lepton number violating interactions and their effects on neutrino oscillation experiments
Mixing between bosons that transform differently under the standard model
gauge group, but identically under its unbroken subgroup, can induce
interactions that violate the total lepton number. We discuss four-fermion
operators that mediate lepton number violating neutrino interactions both in a
model-independent framework and within supersymmetry (SUSY) without R-parity.
The effective couplings of such operators are constrained by: i) the upper
bounds on the relevant elementary couplings between the bosons and the
fermions, ii) by the limit on universality violation in pion decays, iii) by
the data on neutrinoless double beta decay and, iv) by loop-induced neutrino
masses. We find that the present bounds imply that lepton number violating
neutrino interactions are not relevant for the solar and atmospheric neutrino
problems. Within SUSY without R-parity also the LSND anomaly cannot be
explained by such interactions, but one cannot rule out an effect
model-independently. Possible consequences for future terrestrial neutrino
oscillation experiments and for neutrinos from a supernova are discussed.Comment: 28 pages, 2 figures, Late
Interplay of LFV and slepton mass splittings at the LHC as a probe of the SUSY seesaw
We study the impact of a type-I SUSY seesaw concerning lepton flavour
violation (LFV) both at low-energies and at the LHC. The study of the di-lepton
invariant mass distribution at the LHC allows to reconstruct some of the masses
of the different sparticles involved in a decay chain. In particular, the
combination with other observables renders feasible the reconstruction of the
masses of the intermediate sleptons involved in decays. Slepton mass splittings can be either
interpreted as a signal of non-universality in the SUSY soft breaking-terms
(signalling a deviation from constrained scenarios as the cMSSM) or as being
due to the violation of lepton flavour. In the latter case, in addition to
these high-energy processes, one expects further low-energy manifestations of
LFV such as radiative and three-body lepton decays. Under the assumption of a
type-I seesaw as the source of neutrino masses and mixings, all these LFV
observables are related. Working in the framework of the cMSSM extended by
three right-handed neutrino superfields, we conduct a systematic analysis
addressing the simultaneous implications of the SUSY seesaw for both high- and
low-energy lepton flavour violation. We discuss how the confrontation of
slepton mass splittings as observed at the LHC and low-energy LFV observables
may provide important information about the underlying mechanism of LFV.Comment: 50 pages, 42 eps Figures, typos correcte
Peaks and Troughs of Three-Dimensional Vestibulo-ocular Reflex in Humans
The three-dimensional vestibulo-ocular reflex (3D VOR) ideally generates compensatory ocular rotations not only with a magnitude equal and opposite to the head rotation but also about an axis that is collinear with the head rotation axis. Vestibulo-ocular responses only partially fulfill this ideal behavior. Because animal studies have shown that vestibular stimulation about particular axes may lead to suboptimal compensatory responses, we investigated in healthy subjects the peaks and troughs in 3D VOR stabilization in terms of gain and alignment of the 3D vestibulo-ocular response. Six healthy upright sitting subjects underwent whole body small amplitude sinusoidal and constant acceleration transients delivered by a six-degree-of-freedom motion platform. Subjects were oscillated about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5° in azimuth. Transients were delivered in yaw, roll, and pitch and in the vertical canal planes. Eye movements were recorded in with 3D search coils. Eye coil signals were converted to rotation vectors, from which we calculated gain and misalignment. During horizontal axis stimulation, systematic deviations were found. In the light, misalignment of the 3D VOR had a maximum misalignment at about 45°. These deviations in misalignment can be explained by vector summation of the eye rotation components with a low gain for torsion and high gain for vertical. In the dark and in response to transients, gain of all components had lower values. Misalignment in darkness and for transients had different peaks and troughs than in the light: its minimum was during pitch axis stimulation and its maximum during roll axis stimulation. We show that the relatively large misalignment for roll in darkness is due to a horizontal eye movement component that is only present in darkness. In combination with the relatively low torsion gain, this horizontal component has a relative large effect on the alignment of the eye rotation axis with respect to the head rotation axis
HIV seroprevalence and its effect on outcome of moderate to severe burn injuries: A Ugandan experience
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HIV infection in a patient with burn injuries complicates the care of both the patient and the treating burn team. This study was conducted to establish the prevalence of HIV among burn patients in our setting and to compare the outcome of these patients who are HIV positive with those who are HIV negative. This was a prospective cohort study involving burn injury patients admitted to Mulago Hospital between November 2005 and February 2006. Patients were stratified into HIV positive (exposed) group and HIV-negative (unexposed) group. Data was collected using a pre-tested coded questionnaire and analyzed using SPSS statistical computer software version 11.5. Of the 130 patients included in the study, 17 (13.1%) patients tested HIV positive and this formed the study (exposed) group. The remaining 113 patients (86.9%) formed the control (unexposed) group. In the HIV positive group, females outnumbered males by a ratio of 1.4:1 and the mean age was 28.4 ± 21.5 years (range 3 months-34 years). 64.7% of HIV positive patients reported to have risk factors for HIV infection. Of these, multiple sexual partners [Odds Ratio 8.44, 95% C.I. (3.87-143.23), P = 0.011] and alcoholism [Odds Ratio 8.34, 95% C.I. (5.76-17.82), P = 0.002] were found to be independently and significantly associated with increased risk to HIV infection. The mean CD4 count for HIV positive and HIV negative patients were 394 ± 328 cells/μL and 912 ± 234 cells/μL respectively which is statistically significant (P = 0.001). There was no difference in the bacteria cultured from the wounds of HIV positive and negative patients (P = 0.322). Patients with clinical signs of sepsis had lower CD4+ counts compared to patients without sepsis (P < 0.001). ). Skin grafting was carried out in 35.3% of HIV negative patients and 29.4% of HIV positive patients with no significant difference in skin graft take and the degree of healed burn on discharge was the same (P = 0.324). There was no significant difference in hospital stay between HIV positive and negative patients (P = 0.674). The overall mortality rate was 11.5%. Using multivariate logistic regression analysis, mortality rate was found to be independently and significantly related to the age of the patient, HIV positive with stigmata of AIDS, CD4 count, inhalation injury, %TBSA and severity of burn (p-value < 0.001). HIV infection is prevalent among burn injury patients in our setting and thus presents an occupational hazard to health care workers who care for these patients. All burn health care workers in this region need to practice universal precautions in order to reduce the risk of exposure to HIV infection and post-exposure prophylaxis should be emphasized. The outcome of burn injury in HIV infected patients is dependent upon multiple variables such as age of the patient, inhalation injury and %TBSA and not the HIV status alone
Spatio-Temporal Dynamics of Human Intention Understanding in Temporo-Parietal Cortex: A Combined EEG/fMRI Repetition Suppression Paradigm
Inferring the intentions of other people from their actions recruits an inferior fronto-parietal action observation network as well as a putative social network that includes the posterior superior temporal sulcus (STS). However, the functional dynamics within and among these networks remains unclear. Here we used functional magnetic resonance imaging (fMRI) and high-density electroencephalogram (EEG), with a repetition suppression design, to assess the spatio-temporal dynamics of decoding intentions. Suppression of fMRI activity to the repetition of the same intention was observed in inferior frontal lobe, anterior intraparietal sulcus (aIPS), and right STS. EEG global field power was reduced with repeated intentions at an early (starting at 60 ms) and a later (∼330 ms) period after the onset of a hand-on-object encounter. Source localization during these two intervals involved right STS and aIPS regions highly consistent with RS effects observed with fMRI. These results reveal the dynamic involvement of temporal and parietal networks at multiple stages during the intention decoding and without a strict segregation of intention decoding between these networks
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