12 research outputs found
Constraints on the parameters of the Left Right Mirror Model
We study some phenomenological constraints on the parameters of a left right
model with mirror fermions (LRMM) that solves the strong CP problem. In
particular, we evaluate the contribution of mirror neutrinos to the invisible Z
decay width (\Gamma_Z^{inv}), and we find that the present experimental value
on \Gamma_Z^{inv}, can be used to place an upper bound on the Z-Z' mixing angle
that is consistent with limits obtained previously from other low-energy
observables. In this model the charged fermions that correspond to the standard
model (SM) mix with its mirror counterparts. This mixing, simultaneously with
the Z-Z' one, leads to modifications of the \Gamma(Z --> f \bar{f}) decay
width. By comparing with LEP data, we obtain bounds on the standard-mirror
lepton mixing angles. We also find that the bottom quark mixing parameters can
be chosen to fit the experimental values of R_b, and the resulting values for
the Z-Z' mixing angle do not agree with previous bounds. However, this
disagreement disappears if one takes the more recent ALEPH data.Comment: 7 pages, 2 figures, REVTe
Cosmological limit on the neutrino mass
We have performed a careful analysis of constraints on the neutrino mass from
current cosmological data. Combining data from the cosmic microwave background
and the 2dF galaxy survey yields an upper limit on the sum of the three
neutrino mass eigenstates of \sum m_nu < 3 eV (95% conf.), without including
additional priors. Including data from SNIa observations, Big Bang
nucleosynthesis, and HST Hubble key project data on H_0 tightens the limit to
\sum m_nu < 2.5 eV (95% conf.). We also perform a Fisher matrix analysis which
illustrates the cosmological parameter degeneracies affecting the determination
of \sum m_nu.Comment: 6 pages, 2 figures, uses Revtex
A Simple Approach to Fourth Generation Effects in Decay
In a scenario in which fourth generation fermions exist, we study effects of
new physics on the differential decay width, forward-backward asymmetry
and integrated branching ratio for
decay with . Prediction of the new physics on the mentioned
quantities essentially differs from the Standard Model results, in certain
regions of the parameter space, enhancement of new physics on the above
mentioned physical quantities can yield values as large as two times of the SM
predictions, whence present limits of experimental measurements of branching
ratio is spanned, contraints of the new physics can be extracted.
For the fourth generation CKM factor we
use and ranges, take into consideration the
possibility of a complex phase where it may bring sizable contributions,
obtained no significant dependency on the imaginary part of the new CKM factor.
For the above mentioned quantities with a new family, deviations from the SM
are promising, can be used as a probe of new physics.Comment: 9 pages aps forma
Search for Heavy Neutral and Charged Leptons in e+ e- Annihilation at LEP
A search for exotic unstable neutral and charged heavy leptons as well as for
stable charged heavy leptons is performed with the L3 detector at LEP.
Sequential, vector and mirror natures of heavy leptons are considered. No
evidence for their existence is found and lower limits on their masses are set
Simple Connection Between Atmospheric and Solar Neutrino Vacuum Oscillations
Extending the minimal standard model of particle interactions (without
right-handed singlet neutrinos) to include a heavy scalar triplet to
obtain nonzero Majorana neutrino masses, I derive the following simple
realistic connection between atmospheric and solar neutrino vacuum
oscillations: , where is the assumed common approximate mass of
each neutrino (which may be suitable for hot dark matter) and comes from the radiative
splitting of the degeneracy due to the charged leptons.Comment: Version to appear in Phys. Rev. Let
Axillary dissection versus no axillary dissection in patients with breast cancer and sentinel-node micrometastases (IBCSG 23-01): 10-year follow-up of a randomised, controlled phase 3 trial
Background: We previously reported the 5-year results of the phase 3 IBCSG 23-01 trial comparing disease-free survival in patients with breast cancer with one or more micrometastatic ( 642 mm) sentinel nodes randomly assigned to either axillary dissection or no axillary dissection. The results showed no difference in disease-free survival between the groups and showed non-inferiority of no axillary dissection relative to axillary dissection. The current analysis presents the results of the study after a median follow-up of 9\ub77 years (IQR 7\ub78\u201312\ub77). Methods: In this multicentre, randomised, controlled, open-label, non-inferiority, phase 3 trial, participants were recruited from 27 hospitals and cancer centres in nine countries. Eligible women could be of any age with clinical, mammographic, ultrasonographic, or pathological diagnosis of breast cancer with largest lesion diameter of 5 cm or smaller, and one or more metastatic sentinel nodes, all of which were 2 mm or smaller and with no extracapsular extension. Patients were randomly assigned (1:1) before surgery (mastectomy or breast-conserving surgery) to no axillary dissection or axillary dissection using permuted blocks generated by a web-based congruence algorithm, with stratification by centre and menopausal status. The protocol-specified primary endpoint was disease-free survival, analysed in the intention-to-treat population (as randomly assigned). Safety was assessed in all randomly assigned patients who received their allocated treatment (as treated). We did a one-sided test for non-inferiority of no axillary dissection by comparing the observed hazard ratios (HRs) for disease-free survival with a margin of 1\ub725. This 10-year follow-up analysis was not prespecified in the trial's protocol and thus was not adjusted for multiple, sequential testing. This trial is registered with ClinicalTrials.gov, number NCT00072293. Findings: Between April 1, 2001, and Feb 8, 2010, 6681 patients were screened and 934 randomly assigned to no axillary dissection (n=469) or axillary dissection (n=465). Three patients were ineligible and were excluded from the trial after randomisation. Disease-free survival at 10 years was 76\ub78% (95% CI 72\ub75\u201381\ub70) in the no axillary dissection group, compared with 74\ub79% (70\ub75\u201379\ub73) in the axillary dissection group (HR 0\ub785, 95% CI 0\ub765\u20131\ub711; log-rank p=0\ub724; p=0\ub70024 for non-inferiority). Long-term surgical complications included lymphoedema of any grade in 16 (4%) of 453 patients in the no axillary dissection group and 60 (13%) of 447 in the axillary dissection group, sensory neuropathy of any grade in 57 (13%) in the no axillary dissection group versus 85 (19%) in the axillary dissection group, and motor neuropathy of any grade (14 [3%] in the no axillary dissection group vs 40 [9%] in the axillary dissection group). One serious adverse event (postoperative infection and inflamed axilla requiring hospital admission) was attributed to axillary dissection; the event resolved without sequelae. Interpretation: The findings of the IBCSG 23-01 trial after a median follow-up of 9\ub77 years (IQR 7\ub78\u201312\ub77) corroborate those obtained at 5 years and are consistent with those of the 10-year follow-up analysis of the Z0011 trial. Together, these findings support the current practice of not doing an axillary dissection when the tumour burden in the sentinel nodes is minimal or moderate in patients with early breast cancer. Funding: International Breast Cancer Study Group