600 research outputs found
Invisible Z-Boson Decays at e+e- Colliders
The measurement of the invisible Z-boson decay width at e+e- colliders can be
done "indirectly", by subtracting the Z-boson visible partial widths from the
Z-boson total width, or "directly", from the process e+e- -> \gamma \nu
\bar{\nu}. Both procedures are sensitive to different types of new physics and
provide information about the couplings of the neutrinos to the Z-boson. At
present, measurements at LEP and CHARM II are capable of constraining the
left-handed Z\nu\nu-coupling, 0.45 <~ g_L <~ 0.5, while the right-handed one is
only mildly bounded, |g_R| <= 0.2. We show that measurements at a future e+e-
linear collider at different center-of-mass energies, \sqrt{s} = MZ and
\sqrt{s}s ~ 170 GeV, would translate into a markedly more precise measurement
of the Z\nu\nu-couplings. A statistically significant deviation from Standard
Model predictions will point toward different new physics mechanisms, depending
on whether the discrepancy appears in the direct or the indirect measurement of
the invisible Z-width. We discuss some scenarios which illustrate the ability
of different invisible Z-boson decay measurements to constrain new physics
beyond the Standard Model
The prognostic value of tumor mitotic rate in children and adolescents with cutaneous melanoma:A retrospective cohort study
Background: Mitotic rate is a strong predictor of outcome in adult patients with primary cutaneous melanoma, but for children and adolescent patients this is unknown. Objective: We sought to assess the prognostic value of primary tumor mitotic rate in children and adolescents with primary melanoma. Methods: This was a cohort study of 156 patients who were <20 years of age and who had clinically localized cutaneous melanoma. Patients <12 years of age were classified as children and those 12 to 19 years of age as adolescents. Clinicopathologic and outcome data were collected. Recurrence-free and melanoma-specific survival were calculated. Univariable and multivariable analyses were performed using Cox proportional hazard models. Results: Thirteen of 156 patients (8%) were children. The mitotic rate was ≥1/mm2 in 104 patients (67%) and correlated with increasing Breslow thickness. A positive sentinel node was found in 23 of 61 patients (38%) in whom a sentinel lymph node biopsy specimen was obtained. The median follow-up was 61 months. Five-year melanoma-specific and recurrence-free survival rates were 91% and 84%, respectively. Mitotic rate was a stronger predictor of outcome than tumor thickness and was the only factor independently associated with recurrence-free survival. Limitations: This research was conducted at a single institution and the sample size was small. Conclusion: Mitotic rate is an independent predictor of recurrence-free survival in children and adolescents with clinically localized melanoma
The OPERA experiment Target Tracker
The main task of the Target Tracker detector of the long baseline neutrino
oscillation OPERA experiment is to locate in which of the target elementary
constituents, the lead/emulsion bricks, the neutrino interactions have occurred
and also to give calorimetric information about each event. The technology used
consists in walls of two planes of plastic scintillator strips, one per
transverse direction. Wavelength shifting fibres collect the light signal
emitted by the scintillator strips and guide it to both ends where it is read
by multi-anode photomultiplier tubes. All the elements used in the construction
of this detector and its main characteristics are described.Comment: 25 pages, submitted to Nuclear Instrument and Method
A LRRK2-Dependent EndophilinA Phosphoswitch Is Critical for Macroautophagy at Presynaptic Terminals.
Synapses are often far from the soma and independently cope with proteopathic stress induced by intense neuronal activity. However, how presynaptic compartments turn over proteins is poorly understood. We show that the synapse-enriched protein EndophilinA, thus far studied for its role in endocytosis, induces macroautophagy at presynaptic terminals. We find that EndophilinA executes this unexpected function at least partly independent of its role in synaptic vesicle endocytosis. EndophilinA-induced macroautophagy is activated when the kinase LRRK2 phosphorylates the EndophilinA-BAR domain and is blocked in animals where EndophilinA cannot be phosphorylated. EndophilinA-phosphorylation promotes the formation of highly curved membranes, and reconstitution experiments show these curved membranes serve as docking stations for autophagic factors, including Atg3. Functionally, deregulation of the EndophilinA phosphorylation state accelerates activity-induced neurodegeneration. Given that EndophilinA is connected to at least three Parkinson's disease genes (LRRK2, Parkin and Synaptojanin), dysfunction of EndophilinA-dependent synaptic macroautophagy may be common in this disorder
Can lepton flavor violating interactions explain the atmospheric neutrino problem?
We investigate whether flavor changing neutrino interactions (FCNIs) can be
sufficiently large to provide a viable solution to the atmospheric neutrino
problem. Effective operators induced by heavy boson exchange that allow for
flavor changing neutrino scattering off quarks or electrons are related by an
rotation to operators that induce anomalous tau decays. Since
violation is small for New Physics at or above the weak scale, one
can use the upper bounds on lepton flavor violating tau decays or on lepton
universality violation to put severe, model-independent bounds on the relevant
non-standard neutrino interactions. Also -induced flavor changing neutral
currents, due to heavy singlet neutrinos, are too small to be relevant for the
atmospheric neutrino anomaly. We conclude that the FCNI solution to the
atmospheric neutrino problem is ruled out.Comment: 16 pages, no figures, Late
Bounds on the tau and muon neutrino vector and axial vector charge radius
A Majorana neutrino is characterized by just one flavor diagonal
electromagnetic form factor: the anapole moment, that in the static limit
corresponds to the axial vector charge radius . Experimental information
on this quantity is scarce, especially in the case of the tau neutrino. We
present a comprehensive analysis of the available data on the single photon
production process off Z-resonance, and we
discuss the constraints that these measurements can set on for the tau
neutrino. We also derive limits for the Dirac case, when the presence of a
vector charge radius is allowed. Finally, we comment on additional
experimental data on scattering from the NuTeV, E734, CCFR and
CHARM-II collaborations, and estimate the limits implied for and
for the muon neutrino.Comment: 20 pages, 2 eps figures. CCFR data included in the analysis.
Conclusion unchange
Measurement of electron-neutrino electron elastic scattering
The cross section for the elastic scattering reaction nu_e+e- -> nu_e+e- was
measured by the Liquid Scintillator Neutrino Detector using a mu+ decay-at-rest
nu_e beam at the Los Alamos Neutron Science Center. The standard model of
electroweak physics predicts a large destructive interference between the
charge current and neutral current channels for this reaction. The measured
cross section, sigma_{nu_e e-}=[10.1 +- 1.1(stat.) +- 1.0(syst.)]x E_{nu_e}
(MeV) x 10^{-45} cm^2, agrees well with standard model expectations. The
measured value of the interference parameter, I=-1.01 +- 0.13(stat.) +-
0.12(syst.), is in good agreement with the standard model expectation of
I^{SM}=-1.09. Limits are placed on neutrino flavor-changing neutral currents.
An upper limit on the muon-neutrino magnetic moment of 6.8 x 10^{-10} mu_{Bohr}
is obtained using the nu_mu and \bar{nu}_mu fluxes from pi+ and mu+ decay.Comment: 22 pages, 11 figure
Leading order analysis of neutrino induced dimuon events in the CHORUS experiment
We present a leading order QCD analysis of a sample of neutrino induced
charged-current events with two muons in the final state originating in the
lead-scintillating fibre calorimeter of the CHORUS detector. The results are
based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign
dimuon events collected during the exposure of the detector to the CERN Wide
Band Neutrino Beam between 1995 and 1998. % with GeV
and GeV collected %between 1995 and 1998. The analysis yields a
value of the charm quark mass of \mc = (1.26\pm 0.16 \pm 0.09) \GeVcc and a
value of the ratio of the strange to non-strange sea in the nucleon of , improving the results obtained in similar analyses
by previous experiments.Comment: Submitted to Nuclear Physics
Determination of the muon charge sign with the dipolar spectrometers of the OPERA experiment
The OPERA long-baseline neutrino-oscillation experiment has observed the
direct appearance of in the CNGS beam. Two large muon
magnetic spectrometers are used to identify muons produced in the
leptonic decay and in interactions by measuring their charge and
momentum. Besides the kinematic analysis of the decays, background
resulting from the decay of charmed particles produced in
interactions is reduced by efficiently identifying the muon track. A new method
for the charge sign determination has been applied, via a weighted angular
matching of the straight track-segments reconstructed in the different parts of
the dipole magnets. Results obtained for Monte Carlo and real data are
presented. Comparison with a method where no matching is used shows a
significant reduction of up to 40\% of the fraction of wrongly determined
charges.Comment: 10 pages. Improvements in the tex
Procedure for short-lived particle detection in the OPERA experiment and its application to charm decays
The OPERA experiment, designed to perform the first observation of oscillations in appearance mode through the detection of
the leptons produced in charged current interactions, has
collected data from 2008 to 2012. In the present paper, the procedure developed
to detect particle decays, occurring over distances of the order of 1 mm
from the neutrino interaction point, is described in detail. The results of its
application to the search for charmed hadrons are then presented as a
validation of the methods for appearance detection
- …