Elastic Scattering of Neutrinos off Polarized Electrons

We calculate the cross sections for elastic nu_l + e -> nu_l + e and antinu_l + e -> antinu_l + e scattering (l=e, mu or tau) in the Born approximation and with exactly fixed polarization states of target and final-state electrons, discussing their sensitivity to the incident (anti)neutrino flavor. We suggest investigation of the flavor composition of a (anti)neutrino beam by a flux-independent analysis of the scattering of its constituents off polarized electrons.Comment: 6 pages, 2 figure

Elimination of Threshold Singularities in the Relation Between On-Shell and Pole Widths

In a previous communication by two of us, Phys. Rev. Lett. 81, 1373 (1998), the gauge-dependent deviations of the on-shell mass and total decay width from their gauge-independent pole counterparts were investigated at leading order for the Higgs boson of the Standard Model. In the case of the widths, the deviation was found to diverge at unphysical thresholds, m_H = 2 root{xi_V} m_V (V = W,Z), in the R_xi gauge. In this Brief Report, we demonstrate that these unphysical threshold singularities are properly eliminated if a recently proposed definition of wave-function renormalization for unstable particles is invoked.Comment: 8 pages (Latex), 1 figure (Postscript

A New Renormalization Scheme of Fermion Fields in Electroweak Standard Model

This paper has been withdrawn by the author,due a immature idea.Comment: 6 page

Soft SUSY Breaking Grand Unification: Leptons vs Quarks on the Flavor Playground

We systematically analyze the correlations between the various leptonic and hadronic flavor violating processes arising in SUSY Grand Unified Theories. Using the GUT-symmetric relations between the soft SUSY breaking parameters, we assess the impact of hadronic and leptonic flavor observables on the SUSY sources of flavor violation.Comment: 39 pages, 10 figure

Mind-body relationships in elite apnea divers during breath holding: a study of autonomic responses to acute hypoxemia

The mental control of ventilation with all associated phenomena, from relaxation to modulation of emotions, from cardiovascular to metabolic adaptations, constitutes a psychophysiological condition characterizing voluntary breath-holding (BH). BH induces several autonomic responses, involving both autonomic cardiovascular and cutaneous pathways, whose characterization is the main aim of this study. Electrocardiogram and skin conductance (SC) recordings were collected from 14 elite divers during three conditions: free breathing (FB), normoxic phase of BH (NPBH) and hypoxic phase of BH (HPBH). Thus, we compared a set of features describing signal dynamics between the three experimental conditions: from heart rate variability (HRV) features (in time and frequency-domains and by using nonlinear methods) to rate and shape of spontaneous SC responses (SCRs). The main result of the study rises by applying a Factor Analysis to the subset of features significantly changed in the two BH phases. Indeed, the Factor Analysis allowed to uncover the structure of latent factors which modeled the autonomic response: a factor describing the autonomic balance (AB), one the information increase rate (IIR), and a latter the central nervous system driver (CNSD). The BH did not disrupt the FB factorial structure, and only few features moved among factors. Factor Analysis indicates that during BH (1) only the SC described the emotional output, (2) the sympathetic tone on heart did not change, (3) the dynamics of interbeats intervals showed an increase of long-range correlation that anticipates the HPBH, followed by a drop to a random behavior. In conclusion, data show that the autonomic control on heart rate and SC are differentially modulated during BH, which could be related to a more pronounced effect on emotional control induced by the mental training to BH

Mind-body relationships in elite apnea divers during breath holding: a study of autonomic responses to acute hypoxemia

The mental control of ventilation with all associated phenomena, from relaxation to modulation of emotions, from cardiovascular to metabolic adaptations, constitutes a psychophysiological condition characterizing voluntary breath-holding (BH). BH induces several autonomic responses, involving both autonomic cardiovascular and cutaneous pathways, whose characterization is the main aim of this study. Electrocardiogram and skin conductance (SC) recordings were collected from 14 elite divers during three conditions: free breathing (FB), normoxic phase of BH (NPBH) and hypoxic phase of BH (HPBH). Thus, we compared a set of features describing signal dynamics between the three experimental conditions: from heart rate variability (HRV) features (in time and frequency-domains and by using nonlinear methods) to rate and shape of spontaneous SC responses (SCRs). The main result of the study rises by applying a Factor Analysis to the subset of features significantly changed in the two BH phases. Indeed, the Factor Analysis allowed to uncover the structure of latent factors which modeled the autonomic response: a factor describing the autonomic balance (AB), one the information increase rate (IIR), and a latter the central nervous system driver (CNSD). The BH did not disrupt the FB factorial structure, and only few features moved among factors. Factor Analysis indicates that during BH (1) only the SC described the emotional output, (2) the sympathetic tone on heart did not change, (3) the dynamics of interbeats intervals showed an increase of long-range correlation that anticipates the HPBH, followed by a drop to a random behavior. In conclusion, data show that the autonomic control on heart rate and SC are differentially modulated during BH, which could be related to a more pronounced effect on emotional control induced by the mental training to BH

Testing new physics with the electron g-2

We argue that the anomalous magnetic moment of the electron (a_e) can be used to probe new physics. We show that the present bound on new-physics contributions to a_e is 8*10^-13, but the sensitivity can be improved by about an order of magnitude with new measurements of a_e and more refined determinations of alpha in atomic-physics experiments. Tests on new-physics effects in a_e can play a crucial role in the interpretation of the observed discrepancy in the anomalous magnetic moment of the muon (a_mu). In a large class of models, new contributions to magnetic moments scale with the square of lepton masses and thus the anomaly in a_mu suggests a new-physics effect in a_e of (0.7 +- 0.2)*10^-13. We also present examples of new-physics theories in which this scaling is violated and larger effects in a_e are expected. In such models the value of a_e is correlated with specific predictions for processes with violation of lepton number or lepton universality, and with the electric dipole moment of the electron.Comment: 34 pages, 7 figures. Minor changes and references adde

Low-Energy Supersymmetry Breaking from String Flux Compactifications: Benchmark Scenarios

Soft supersymmetry breaking terms were recently derived for type IIB string flux compactifications with all moduli stabilised. Depending on the choice of the discrete input parameters of the compactification such as fluxes and ranks of hidden gauge groups, the string scale was found to have any value between the TeV and GUT scales. We study the phenomenological implications of these compactifications at low energy. Three realistic scenarios can be identified depending on whether the Standard Model lies on D3 or D7 branes and on the value of the string scale. For the MSSM on D7 branes and the string scale between 10^12 GeV and 10^17 GeV we find that the LSP is a neutralino, while for lower scales it is the stop. At the GUT scale the results of the fluxed MSSM are reproduced, but now with all moduli stabilised. For the MSSM on D3 branes we identify two realistic scenarios. The first one corresponds to an intermediate string scale version of split supersymmetry. The second is a stringy mSUGRA scenario. This requires tuning of the flux parameters to obtain the GUT scale. Phenomenological constraints from dark matter, (g-2)_mu and BR(b->s gamma) are considered for the three scenarios. We provide benchmark points with the MSSM spectrum, making the models suitable for a detailed phenomenological analysis.Comment: 29 pages, 12 figures, reference adde

Width and Partial Widths of Unstable Particles in the Light of the Nielsen Identities

Fundamental properties of unstable particles, including mass, width, and partial widths, are examined on the basis of the Nielsen identities (NI) that describe the gauge dependence of Green functions. In particular, we prove that the pole residues and associated definitions of branching ratios and partial widths are gauge independent to all orders. A simpler, previously discussed definition of branching ratios and partial widths is found to be gauge independent through next-to-next-to-leading order. It is then explained how it may be modified in order to extend the gauge independence to all orders. We also show that the physical scattering amplitude is the most general combination of self-energy, vertex, and box contributions that is gauge independent for arbitrary s, discuss the analytical properties of the NI functions, and exhibit explicitly their one-loop expressions in the Z-gamma sector of the Standard Model.Comment: 20 pages (Latex); minor changes included, accepted for publication in Phys. Rev.