290 research outputs found
Feasibility investigation of exposed-core fiber for methadone sensing in biological fluids
No full textIn this paper, we explore numerically the feasibility of a methadone sensor based on novel exposed-core optical fiber coated with a sensitive polymeric layer. The sensor characteristics have been simulated using the Finite Element Method (FEM). In particular, we have shown that the sensor performance can be enhanced, more specifically the minimum detectable concentration of methadone can be reduced, via a suitable choice of the fiber cross section.T. Palmisano, F. Prudenzano, M. De Sario, L. Mescia, S.C. Warren-Smith and T. M. Monr
The bearable lightness of new physics beyond the Standard Model
No full textThe absence of new physics signals at the TeV scale has recently triggered a shift of interest towards light and weakly coupled extensions of the Standard Model (SM). We consider a light new physics scenario coupled to the SM fields in a effective theory. Different types of light new physics, searched by present and future experiments at the intensity frontier, are studied and investigated, from sub-GeV abelian gauge vector bosons to right-handed neutrinos at GeV scale. In the former case, we study the dependence on the UV completion of the effective Wess-Zumino terms that appears in the IR theory when gauge bosons are coupled to a SM current whose conservation is broken at loop level. We show how to avoid the would be strong constraints of energy enhanced process due to flavor changing neutral current generated by the Wess-Zumino terms. In the latter case, we work in a minimal see-saw scenario with two right-handed neutrinos with mass at the GeV scale and highlight the prospects for testing the decay induced by an effective dipole operator at future facilities targeting long-lived particles such as the SHiP experiment. In the last part of the thesis, we critically re-examine the new particle interpretation of recent experimental anomalies observed in nuclear transition from the ATOMKI collaboration. Indeed, the hypothetical particle, denoted as and proposed by the collaboration itself, would be a light and weakly-interacting boson and we employ a multipole expansion to estimate the nucleon coupling to the light state, identifying the axial vector state as the most promising candidate. Intensity-frontier experiments like MEG II and PADME will probe the ATOMKI anomaly in the near future
Coupling of the light vector meson to the vector and to the tensor current
No full textWe present results for the coupling of the light vector mesons to the tensor current, relative to the standard vector meson decay constants. From an O(a)-improved lattice study, performed at three values of the lattice spacing in the quenched approximation, our final values (in the continuum limit), in the (MS) over bar scheme at mu = 2 GeV, are: f(rho)(T)/f(rho) = 0.72(2)((+2)(-0)), f(K)(T)*/f(K)* = 0.74(2), f(phi)(T)/ f(phi) = 0.76(1)
The place of cyclical therapy for the treatment of membranous nephropathy in the era of rituximab
No full textPrimary membranous nephropathy (MN) is the most frequent cause of nephrotic syndrome in adults, due to a variety of autoantibodies, most frequently against phospholipase A2 receptor (PLA2R). In severe cases or when spontaneous remission is not achieved, immunosuppression is required. Cyclical therapy, based on glucocorticoids and cyclophosphamide on alternate months for 6 months, has proven effective to induce remission and reduce the risk of end-stage renal disease. Since the early 2000s, rituximab (RTX) has emerged as a key player in the management of MN, showing overall comparable effectiveness and likely better safety compared with the cyclical regimen, despite the lack of adequately powered trials comparing the two approaches head to head. For these reasons, RTX is now considered the agent of choice for most patients with MN. However, there are still uncertainties. Around 20-40% of patients are resistant to RTX, especially in the setting of high anti-PLA2R levels, and this drug remains relatively unexplored in patients with the most severe disease. In these scenarios, although the expanding therapeutic armamentarium is probably going to provide further options, the cyclical regimen still plays a key role as a safety net. The aim of this article is to illustrate the role of cyclical therapy in the RTX era
K ->pi l nu semileptonic form factors from two-flavor lattice QCD
No full textWe present new lattice results of the K ->pi l nu semileptonic form factors obtained from simulations with two flavors of dynamicaltwisted-mass fermions, using pion masses as light as 260 MeV. Our main result is f(+)(0)=0.9560(84), which, combined with the latest experimental data for Kl3 decays, leads to |Vus|=0.2267(5)(exp)(20)(f+(0)). Using the PDG(2008) determinations of|Vud| and |Vub| our result implies for the unitarity relation |Vud|^2+|Vus|^2+|Vub|^2=1.0004(15). For the O(p^6) term of the chiral expansion of f+(0) we get Delta f = f+(0)-1-f2=-0.0214(84)
Covert symmetries in the neutrino mass matrix
No full textThe flavour neutrino puzzle is often addressed by considering neutrino mass matrices m with a certain number of vanishing entries (mij = 0 for some values of the indices), since a reduction in the number of free parameters increases the predictive power. Symmetries that can enforce textures zero can also enforce a more general type of conditions f(mij) = 0 with f some function of the matrix elements mij. In this case m can have all entries non-vanishing with no reduction in its predictive power. We classify all generation-dependent U(1) symmetries which, in the presence of two leptonic Higgs doublets, can reduce the number of independent high-energy parameters of type-I seesaw to the minimum number compatible with non-vanishing neutrino mixings and CP violation. These symmetries are broken above the scale where the effective operator is generated and can thus remain covert, in the sense that no explicit evidence of the symmetry can be read off the neutrino mass matrix, and different symmetries can give rise to the same low-energy structure. We find that only two cases are viable: one yields a structure with two zero-textures already considered in the literature, the other has no zero-textures and has never been considered before. It predicts normal ordering, a lightest neutrino mass ∼ 10 meV, a Dirac phase δ ∼ 3π2 and definite values for the Majorana phases
First lattice calculation of the electromagnetic operator amplitude (Pi0|Q(+)gamma|K0)
No full textWe present the first lattice calculation of the matrix element of the electromagnetic operator [pi (0)|Q(+)(gamma)|K(0)], where = Q(+)(gamma) = (Q(d)e/16 pi (2))((s) over bar (L)sigma (mu nu) F(mu nu)d(R) + (s) over bar (R)sigma (mu nu) F(mu nu)d(L)) This matrix element plays an important roe, since it contributes to enhance the CP violating part of the K-L --> pi (0)e(+)e(-) amplitude in supersymmetric extensions of the Standard Model
Nonperturbatively improved heavy-light mesons: Masses and decay constants
No full textWe present a study of the heavy-light spectrum and of the D- and B-meson decay constants. The results were obtained in the quenched approximation, by using the nonperturbatively improved clover lattice action at beta =6.2, with a sample of 100 configurations, on a 24(3)x64 lattice. After a careful analysis of the systematic errors present in the extraction of the physical results, by assuming quite conservative discretization errors, we find f(D)=231+/-12(-1)(+8) Mev, f(D) = 211 +/- 14(-12)(+2), MeV f(Ds)/f(D) = 1.10(2) f(Bs) = 204+/-16(-0)(+36) MeV, f(B)=179 +/-18(-9)(+34) MeV, f(Bs)/f(B) = 1.14(3)(-1)(+1). Our results, which have smaller discretization errors than many previous estimates at fixed value of the lattice spacing a, support a large value of f(B) in the quenched approximation. [S0556-2821(99)00317-3]
Nonperturbatively improved heavy-light mesons: Masses and decay constants
No full textWe present a study of the heavy-light spectrum and of the D- and B-meson decay constants. The results were obtained in the quenched approximation, by using the nonperturbatively improved clover lattice action at beta =6.2, with a sample of 100 configurations, on a 24(3)x64 lattice. After a careful analysis of the systematic errors present in the extraction of the physical results, by assuming quite conservative discretization errors, we find f(D)=231+/-12(-1)(+8) Mev, f(D) = 211 +/- 14(-12)(+2), MeV f(Ds)/f(D) = 1.10(2) f(Bs) = 204+/-16(-0)(+36) MeV, f(B)=179 +/-18(-9)(+34) MeV, f(Bs)/f(B) = 1.14(3)(-1)(+1). Our results, which have smaller discretization errors than many previous estimates at fixed value of the lattice spacing a, support a large value of f(B) in the quenched approximation
Window for preferred axion models
No full textWe discuss phenomenological criteria for defining "axion windows," namely regions in the parameter space of the axion-photon coupling where realistic models live. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be highly desirable to specify them in terms of precise phenomenological requirements. We first focus on hadronic axion models within post-inflationary scenarios, in which the initial abundance of the new vectorlike quarks Q is thermal. We classify their representations RQ by requiring that (i) the Q are sufficiently short lived to avoid issues with long-lived strongly interacting relics, (ii) the theory remains weakly coupled up to the Planck scale. The more general case of multiple RQ is also studied, and the absolute upper and lower bounds on the axion-photon coupling as a function of the axion mass is identified. Pre-inflationary scenarios in which the axion decay constant remains bounded as fa≤5×1011 GeV allow for axion-photon couplings only about 20% larger. Realistic Dine-Fischler-Srednicki-Zhitnitsky type of axion models also remain encompassed within the hadronic axion window. Some mechanisms that can allow to enhance the axion-photon coupling to values sizeably above the preferred window are discussed
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