Detecting Gluino-Containing Hadrons

When SUSY breaking produces only dimension-2 operators, gluino and photino masses are of order 1 GeV or less. The gluon-gluino bound state has mass 1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and lifetime is largely unconstrained because missing energy and beam dump techniques are ineffective. With only small modifications, upcoming K^0 decay experiments can study most of the interesting range. The lightest gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to find it and the uud-gluino are also discussed.Comment: 13 pp, 1 figure (uuencoded). Descendant of hep-ph/9504295, hep-ph/9508291, and hep-ph/9508292, focused on experimental search techniques. To be published in Phys Rev Let

Impact of D0-D0bar mixing on the experimental determination of gamma

Several methods have been devised to measure the weak phase gamma using decays of the type B+- --> D K+-, where it is assumed that there is no mixing in the D0-D0bar system. However, when using these methods to uncover new physics, one must entertain the real possibility that the measurements are affected by new physics effects in the D0-D0bar system. We show that even values of x_D and/or y_D around 10^{-2} can have a significant impact in the measurement of sin^2{gamma}. We discuss the errors incurred in neglecting this effect, how the effect can be checked, and how to include it in the analysis.Comment: 18 pages, Latex with epsfig, 8 figure

Tattoo-Paper Transfer as a Versatile Platform for All-Printed Organic Edible Electronics

The use of natural or bioinspired materials to develop edible electronic devices is a potentially disruptive technology that can boost point-of-care testing. The technology exploits devices which can be safely ingested, along with pills or even food, and operated from within the gastrointestinal tract. Ingestible electronics could potentially target a significant number of biomedical applications, both as therapeutic and diagnostic tool, and this technology may also impact the food industry, by providing ingestible or food-compatible electronic tags that can smart track goods and monitor their quality along the distribution chain. We hereby propose temporary tattoo-paper as a simple and versatile platform for the integration of electronics onto food and pharmaceutical capsules. In particular, we demonstrate the fabrication of all-printed Organic Field-Effect Transistors (OFETs) on untreated commercial tattoo-paper, and their subsequent transfer and operation on edible substrates with a complex non-planar geometry

Tau and Charm physics highlights

In tau physics, we are at the frontier between the completion of the LEP program and the start of analyses from b-factories, which are expected to produce results in the coming years. Nice results from CLEO are steadily delivered in the meantime. For charm, impressive progress have been achieved by fixed target experiments in the search for CP violation and D^0 - \bar D^0 oscillations. First results from b-factories demonstrate the power of these facilities in such areas. The novel measurement of the D* width by CLEO happens to be rather different from current expectations. The absence of a charm factory explains the lack or the very slow progress in the absolute scale determinations for charm decays.Comment: "Typos corrected and references added

Cathodic protection and hydrogen embrittlement

The main topic of the research activity carried out at the Department of Engineering and Applied Sciences of the University of Bergamo during this 3-year PhD Program was the study of hydrogen embrittlement in high strength low alloy steels under cathodic protection. The project of this PhD Thesis is entitled “Cathodic Protection and Hydrogen Embrittlement”, and the entire research activity was financed by APCE Service Srl (Associazione per la Protezione dalle Corrosioni Elettrolitiche). The necessity of deepening this very wide and complex theme was driven by the purpose of a more efficient prevention and control of the corrosion mechanisms that can verify, in particular operating situations, in underground steel pipelines and transport systems, in which the combined use of a cathodic polarization and a protective coating must be necessarily involved. Cathodic protection (CP), along with the application of protective coatings, represents one of the main techniques for corrosion protection of submerged parts of metal structures exposed to the marine environment, buried structures, and equipment operating with natural and process waters. The extensive experience has made it one of the most reliable protection techniques, essential to guarantee full safety and long service lives in naval, offshore and underground structures, Oil&Gas equipment, transport systems and pipelines, etc. It is usually applied to protect carbon and low alloy steels in neutral or slightly alkaline solutions, in order to reduce the overall loss of metal and to enhance the corrosion-fatigue limits. Protection is achieved by means of a cathodic current, flowing from the anode towards the structure to be protected, sufficient to lower the metal potential at any point of the surface below a protective limit, the so-called protection potential (Ep). To less noble potentials of Ep, the general corrosion rate reduces to less than 10 μm/year, or it becomes nil if the polarization leads to immunity conditions. The effectiveness of this protection technique is indubitable. However, there may be particular conditions in which CP, especially if not correctly applied, can produce negative effects. The most important effect, analyzed in this PhD Thesis work, is that connected to Hydrogen Embrittlement (HE), a specific type of Environmental Assisted Cracking (EAC) connected to the absorption and consequent diffusion of atomic hydrogen through the metal matrix. The risk of such effect becomes evident mostly for excessive cathodic polarizations, when over-protection potentials (Eop) are reached, well below Ep, in which the polarization cathodic current density becomes high and the process of hydrogen development becomes relevant. Therefore, the aim of this PhD Thesis was to better understand the process of hydrogen diffusion in a commercial pipeline steel, because the presence of hydrogen in metallic materials is well known to be detrimental for the mechanical properties in certain conditions, as it causes significant decrease in ductility and/or fracture strength, unexpected failure, etc. Measurements of hydrogen permeation in metallic materials were carried out for nearly 40 years according to the electrochemical permeation technique proposed by Devanathan and Stachurski and used in the experimental tests, which probably provides the simplest and most flexible approach. However, even if many results were published since then and several methods were developed to evaluate hydrogen uptake and transport, the interpretation of the literature data and the correlation with the proposed models was not always satisfactory. The structure of this PhD Thesis is organized in a general section (from Chapter 1 to Chapter 6) and in an experimental section (from Chapter 7 to Chapter 10). As regards the general section, Chapter 1 illustrates the application of CP to buried pipelines in order to eliminate or reduce the corrosion rate of the coating defects exposed to the soil environment down to negligible values, along with the importance of the application of a protective coating on a steel pipeline, which must ensure the physical separation of the steel towards the environment. In fact, even the most efficient and high-performance coating present hidden or non-systematic defects, which the final qualification tests are often unable to detect. Consequently, the application of a cathodic polarization must be necessarily undertaken. However, in correspondence with very negative potentials, the steel is in over-protection conditions. Atomic hydrogen, developed from the cathodic reaction, diffuses through the steel and can lead to the formation and propagation of cracks; this risk increases with the increase in the mechanical strength of the steel. The most important national and international reference standards indicate precise limits for the application of CP to avoid the risk of embrittlement, especially in steels with a high Yield Strength (YS); the critical limit is generally indicated as the potential for the beginning of hydrogen development. Chapter 2 explains the hydrogen induced failure mechanisms related to EAC, subsequent to hydrogen evolution and permeation into the metal matrix, when a metallic material is not protected against an aggressive environment, represented by different kinds of soil in the case of underground pipelines. A quite exhaustive overview of the main theories proposed as a possible explanation for Hydrogen Assisted Cracking (HAC) mechanisms is then reported. In Chapter 3, after the explanation of the pure diffusion mechanism, in accordance with Fick’s first and second law, attention was paid to the effects of microstructure, temperature, sub-surface hydrogen concentration, applied mechanical stress, specimen thickness, and trapping sites. In Chapter 4, the main mathematical models for hydrogen diffusion are presented, both in the case of ideal diffusion (absence of trapping sites) and non-ideal diffusion (presence of trapping sites, i.e. sites that affect hydrogen diffusion and can represent preferential paths or traps, which are usually classified as reversible or irreversible in relation to the binding energy). Chapter 5 will provide an interesting examination of the mathematical models that try to explain the effect of elasto-plastic deformation on hydrogen permeability. In Chapter 6, the electrochemical permeation technique, proposed by Devanathan and Stachurski for the evaluation of hydrogen diffusivity through steel, and used in the further tests, will be analyzed. Chapter 7 describes the experimental permeation tests and procedures performed on one type of high strength low alloy carbon steel, catalogued as API 5L X65 grade steel, which is probably one of the mainly utilized in pipelines construction for the transportation of petroleum and natural gas. The experimental results deriving from the permeation tests, realized in accordance with the International ISO 17081:2014 standard in the absence of an applied load and in the presence of cyclic and incremental step loading conditions, are presented in Chapter 8. The discussion of the results achieved is reported in Chapter 9. For the processing of the experimental curves, firstly the implementation of the pure diffusion model (according to Fick’s second law) was proposed; however, this resulted not accurate enough to simulate the permeation process of hydrogen, due to the existence of trapping sites. Therefore, another processing method, proposed by Grabke and Riecke, allowed to calculate diffusion parameters in a more accurate way than the previous model, also in the presence of residual plastic deformation or loading conditions beyond the yield limit. In Chapter 10, the conclusions to this PhD Thesis work are drawn. From the analysis of the main international and national standards that regulate the application of CP, it was concluded that no criteria are standardized for the determination of the critical limit potential indicated to avoid the occurrence of HE phenomena. This limit should be experimentally determined by means of mechanical tests, but without any precise indication of the test methods to be adopted. As regards the permeation tests performed in the absence or in the presence of an applied load, the results allowed to better understand the variations in hydrogen transport mechanism into a X65 grade pipeline steel. In particular, with the application of cyclic loading conditions beyond the yield limit, it was observed: - Significant decrease in the apparent diffusivity, due to the enhancement of trapping phenomena - Sharp increase in the reversible trapping parameter, due to the contribution of the accumulation of new trapping sites in the plastic deformation field. The extent of the plastic deformation achieved in the tests is relatively low, thus the delaying effect related to the irreversible traps is small if compared to the multiplication of reversible traps - Significant increase in the total hydrogen concentration, as a result of enhanced hydrogen absorption and filling of an increasing number of trapping sites - Appreciable mitigation of the stress field generated by a tensile stress after the application of a compressive stress, with a consequent less marked decrease in Dapp - Temporary reduction in hydrogen flux, determined by a variation of the applied maximum stress, due to an instantaneous reduction of the mobile hydrogen concentration in the lattice, caused by an increase in the number of trapping sites following local plasticization phenomena even for stresses lower than the yield limit. Concerning the permeation tests performed in the presence of an applied incremental step load, for the X65 grade steel (sorbite) and heat treated (martensite) material, it was observed that: - Failure occurred at stress values very close to those in air, and in a region very far from the permeation area, with no crack propagation during the constant deformation phase and, thus, no susceptibility to HE in accordance with the International ASTM F1624-12 standard - Step duration, in the plastic deformation field, was not sufficient for the permeation transient to completely exhaust, even if the tested specimen was just 1-mm thick; therefore, the observation of the subsequent stabilization in the hydrogen permeation flux and the evaluation of the possible occurrence of embrittlement phenomena connected to the filling of new traps was not possible

Leptogenesis and low energy observables in left-right symmetric models

In the context of left-right symmetric models we study the connection of leptogenesis and low energy parameters such as neutrinoless double beta decay and leptonic CP violation. Upon imposition of a unitarity constraint, the neutrino parameters are significantly restricted and the Majorana phases are determined within a narrow range, depending on the kind of solar solution. One of the Majorana phases gets determined to a good accuracy and thereby the second phase can be probed from the results of neutrinoless double beta decay experiments. We examine the contributions of the solar and atmospheric mass squared differences to the asymmetry and find that in general the solar scale dominates. In order to let the atmospheric scale dominate, some finetuning between one of the Majorana phases and the Dirac CP phase is required. In this case, one of the Majorana phases is determined by the amount of CP violation in oscillation experiments.Comment: 18 pages, 6 figures. Matches version to appear in PR

Effect of cyclic loading on hydrogen diffusion in low carbon steels

Carbon steels or low-alloyed steels may be affected by damaging phenomena due to Hydrogen Embrittlement (HE), which is a particular form of Environmental Assisted Cracking (EAC). The insurgence of HE depends on the intrinsic susceptibility of the steel, the applied stress, and the concentration of hydrogen inside the metal. It occurs by a mechanism of absorption and subsequent diffusion of atomic hydrogen through the metal lattice. On steels with a yield strength lower than 700 MPa, HE occurs in the plastic deformation field, in the presence of dynamic loading at slow strain rates or cyclic fatigue loading at very low frequencies. Although several important studies were carried out on the effect of loading conditions on hydrogen diffusion into the metal and HE mechanism, HE phenomena are not fully understood. In this work, the effect of the application of cyclic loads on hydrogen diffusion parameters was studied both in the elastic and in the plastic deformation field. The influence of mean load and amplitude was analyzed. Hydrogen permeation tests were performed on API 5L X65 steel, in accordance with ISO 17081:2014. The specimen behaved as bi-electrode between the two compartments of a Devanathan-Stachurski cell. The anodic side of the specimen was polarized at +340 mV vs Ag/AgCl in a 0.1 M NaOH aerated solution, while the cathodic compartment was filled with an aerated borate solution. A controller enabled temperature adjustment at 20±0.5°C. Once the passivity current registered in the anodic side reached values of 0.05 µA/cm2, a cathodic current density of 0.50 mA/cm2 was applied to charging cathodic side. The study included tests with sine waveform cycling loading, with a maximum level equal to 110% TYS, at a frequency of 10-2 Hz. The results confirmed the values of hydrogen diffusion coefficient usually indicated for low-alloyed steels with a sorbitic microstructure. Strain hardened specimens - stretched above yield strength - showed an increase of steady state current and an extension of the time lag, denoting a slight decrease in the apparent hydrogen diffusion coefficient due to traps effect in the cold deformed steel matrix. Under cyclic loading, an instantaneous peak of current with a subsequent significant transient decrease occurred after cyclic load application, whereas no relevant variation of permeation curve compared to unloaded specimens was observed if specimens were already loaded before hydrogen charging. The instantaneous current peak reached values much higher than the steady state current. This is ascribed to the rupture of the passive film – caused by loading – and its subsequent reformation; in fact, this can also be noted during tests performed on specimens without hydrogen permeation. The following transient, in which the permeation current decreases below the steady state and then returns to it, denotes a relevant trapping effect that causes the instantaneous reduction of mobile hydrogen concentration in the lattice. This becomes more significant for loads closer and closer to the yield strength, mainly beyond this, and can only be noted at the first loading step. Subsequent unloading and loading step at the same mean value showed no transient in the permeation curren

Experiments to Find or Exclude a Long-Lived, Light Gluino

Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter gluinos are allowed, except for certain ranges of lifetime. Only small parts of the mass-lifetime parameter space are excluded for larger masses unless the lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and lifetime estimates for R-hadrons are given, present direct and indirect experimental constraints are reviewed, and experiments to find or definitively exclude these possibilities are suggested.Comment: 27 pp, latex with 1 uufiled figure, RU-94-35. New version amplifies discussion of some points and corresponds to version for Phys. Rev.

Leptogenesis and Neutrino Oscillations Within A Predictive G(224)/SO(10)-Framework

A framework based on an effective symmetry that is either G(224)= SU(2)_L x SU(2)_R xSU(4)^c or SO(10) has been proposed (a few years ago) that successfully describes the masses and mixings of all fermions including neutrinos, with seven predictions, in good accord with the data. Baryogenesis via leptogenesis is considered within this framework by allowing for natural phases (~ 1/20-1/2) in the entries of the Dirac and Majorana mass-matrices. It is shown that the framework leads quite naturally, for both thermal as well as non-thermal leptogenesis, to the desired magnitude for the baryon asymmetry. This result is obtained in full accord with the observed features of the atmospheric and solar neutrino oscillations, as well as with those of the quark and charged lepton masses and mixings, and the gravitino-constraint. Hereby one obtains a unified description of fermion masses, neutrino oscillations and baryogenesis (via leptogenesis) within a single predictive framework.Comment: Efficiency factor updated, some clarifications and new references added. 19 page

Measurement of CP asymmetry in Cabibbo suppressed D0 decays

We measure the CP-violating asymmetries in decays to the D0 -> K+K- and D0 -> pi+pi- CP eigenstates using 540 fb^{-1} of data collected with the Belle detector at or near the Upsilon(4S) resonance. Cabibbo-favored D0 -> K-pi+ decays are used to correct for systematic detector effects. The results, A_{CP}^{KK} = (-0.43 +- 0.30 +- 0.11)% and A_{CP}^{pipi} = (+0.43 +- 0.52 +- 0.12)%, are consistent with no CP violation.Comment: Submitted to Phys. Lett.