445 research outputs found

    Time Evolution of Decay Spectrum in K^0, K^0 bar -> pi^+ pi^- e^+ e^-

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    We consider the decay K^0 (K^0 bar) -> pi^+ pi^- e^+ e^- of a neutral K meson prepared in a state of strangeness +1 (-1). The time evolution of the state produces remarkable time-dependent effects in the angular distribution of the pi^+ pi^- e^+ e^- system. These effects are correlated with the time-dependence of the photon polarization in the radiative decay K^0 (K^0 bar) -> pi^+ pi^- gamma. We study, in particular, the CP-odd, T-odd term in the distribution d Gamma / d phi of the angle between the pi^+ pi^- and the e^+ e^- planes. We also give the spectrum in the case that the decaying meson is an incoherent mixture of K^0 and K^0 bar, and discuss the case of K_S regeneration in a K_L beam.Comment: 16 pages, 8 figures, minor typos corrected, to appear in Phys. Lett.

    Violation of Time Reversal Invariance in the Decays K_L -> pi^+ pi^- gamma and K_L -> pi^+ pi^- e^+ e^-

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    The origin of the large CP-odd and T-odd asymmetry observed in the decay K_L -> pi^+ pi^- e^+ e^- is traced to the polarization properties of the photon in the decay K_L -> pi^+ pi^- gamma. The Stokes vector of the photon S = (S_1, S_2, S_3) is studied as a function of the photon energy and found to possess CP-violating components S_1 and S_2 which are sizeable over a large part of the phase space, despite being proportional to the epsilon parameter of the K_L wave function. The component S_2 is T-even and manifests itself as a circular polarization of the photon, while S_1 is T-odd and gives rise to the asymmetry observed in K_L -> pi^+ pi^- e^+ e^-. The latter is shown to survive in the ``hermitian'' limit in which all unitarity phases are absent, and represents a genuine example of time reversal symmetry breaking in a CPT invariant theory.Comment: 4 pages including 2 figure

    Post-depositional subsidence of the Avellino tephra marker bed in the Pontine plain (Lazio, Italy):Implications for Early Bronze Age palaeogeographical, water level and relative sea level reconstruction

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    Land subsidence has played and is still playing a significant role in coastal wetlands worldwide and in palaeogeographical reconstructions of such wetlands. The varying thickness of compaction-prone sediments over a stable subsurface is a key factor in determining its magnitude and in locating the most affected areas. In the coastal low-lying Agro Pontino (Lazio, Italy), subsidence of the past 90 years has been mapped using historical elevation data. Due to the fortunate preservation of distal Avellino tephra (AV-tephra, ca. 1900 cal. BCE) within its marshy strata, discovered a decade ago, detailed palaeogeographical reconstruction of the landscape in preparation for an assessment of its land use suitability in the Early Bronze Age (EBA) was possible. Current altitude variations of water-lain tephra in lake areas assumed to be connected necessitated a closer look at its original deposition altitude and the role of post-depositional subsidence. Recent subsidence patterns proved very useful for distinguishing stable from subsidence-prone areas. Two different EBA palaeo lake environments are distinguished: an inland and a near-coastal lake. The AV-tephra altitude variation within these lakes partly marks differential post-depositional subsidence within these lakes. Calculation of initial ripening of tephra-bearing lake deposits on top of shallowly buried Pleistocene ridges allowed for an estimation of original tephra deposition altitudes and associated lake levels. For the inland lake, a wide lake edge zone between 0.5 and 2 m above current sea level (m asl) was reconstructed, where EBA habitation or land use was possible. At the near-coastal lake, a water level of −1.5 to −1.3 m asl at the time of AV-tephra deposition was constrained. Because tephra deposition occurred here just after marine influence ceased, this altitude range is proposed to be a Relative Sea Level (RSL) index point at the time of AV-tephra deposition. The altitude range is in agreement with RSL models for tectonically stable areas in this region. The importance of subsidence in palaeogeographical, water level and RSL reconstructions in the region is stressed

    Stokes Vector of Photon in the Decays B^0 -> rho^0 gamma and B^0 -> K^* gamma

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    We consider a model for the decay Bbar^0 -> rho^0 gamma in which the short-distance amplitude determined by the Hamiltonian describing b -> d gamma is combined with a typical long-distance contribution Bbar^0 -> D^+ D^- -> rho^0 gamma. The latter possesses a significant dynamical phase which induces a CP-violating asymmetry A_CP, as well as an important modification of the Stokes vector of the photon. The components S_1 and S_3 of the Stokes vector S = (S_1, S_2, S_3) can be measured in the decay Bbar^0 -> rho^0 gamma^* -> pi^+ pi^- e^+ e^- where they produce a characteristic effect in the angular distribution d Gamma / d phi, phi being the angle between the pi^+ pi^- and e^+ e^- planes. A similar analysis is carried out for the decays Bbar^0 -> Kbar^* gamma and Bbar^0 -> Kbar^* gamma^* -> pi^+ K^- e^+ e^-Comment: 13 pages, 8 figures; v2: Some clarifying remarks added, together with additional references. Minor typos corrected. No change in result

    Autismo in famiglia: quali i tratti in comune? Un contributo di ricerca nell'ambito del Broader Autism Phenotype

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    Background. L’espressione Broader Autism Phenotype (BAP), la cui versione italiana è “fenotipo autistico ampio”, descrive una condizione subclinica, indagata a partire dagli anni 70 sia in ambito genetico che psicologico, nella quale si collocano soggetti , e soprattutto parenti di primo grado di soggetti con autismo, che presentano tratti riconducibili ai tratti peculiari e ai domini dei Disturbi dello Spettro Autistico (ASD). La maggior parte delle ricerche ha mostrato, mediante Studi Familiari e l’uso di Scale Psicometriche, come questi tratti siano maggiormente presenti nei genitori di soggetti nello Spettro autistico rispetto alla popolazione generale. Pochi risultano dalla letteratura i contributi di ricerca nei quali sono stati analizzati i tratti maggiormente condivisi da genitori e figli ASD. Obiettivi. l’obiettivo principale della nostra ricerca sperimentale è stato valutare, in un campione di 131 genitori italiani di 68 bambini con Disturbo dello Spettro Autistico (ASD), le correlazioni tra i tratti dei genitori misurati con l’AQ e i tratti autistici e le variabili cliniche dei figli misurate rispettivamente mediante l’AQ-child e il protocollo diagnostico. Risultati. Sono stati evidenziati tratti comuni soprattutto tra padri e figli e in particolare nella sfera sociale e comunicativa. Si evince un rapporto di correlazione positivo tra numero di tratti autistici nei padri e tratti autistici nei figli. Alcuni tratti dei padri correlano con il comportamento adattivo dei figli misurato con la scala Vineland . Tra i genitori che hanno superato i criteri soglia per il BAP, sono emersi tratti in comune solo tra le madri e i figli. In particolare a una maggiore o minore tendenza all’elaborazione locale degli stimoli nelle madri corrisponde una maggiore o minore tendenza anche nei figli. L’età della madre correla con la gravità della sintomatologia autistica nei figli misurata con l’ADOS. Dallo studio non è emersa una relazione positiva e significativa tra maggiori tratti autistici nei genitori e gravità della sintomatologia autistica nei figli. Conclusioni. valutare i tratti comuni tra genitori e figli ASD permette di comprendere le modalità di trasmissione dei tratti BAP a livello intergenerazionale e permette di verificare i tratti dei genitori che possono costituire fattori di rischio o protezione all’ASD dei figli. Può inoltre risultare utile nella formulazione di programmi di Parent Coaching più adeguati alle caratteristiche del genitore

    Large Direct CP Violation in B^0 -> pi^+ pi^- and an Enhanced Branching Ratio for B^0 -> pi^0 pi^0

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    Recent measurements of B^0 -> pi pi decays reveal two features that are in conflict with conventional calculations: the channel B^0 (Bbar^0) -> pi^+ pi^- shows a large direct CP-violating asymmetry, and the channel B^0 (B^0) -> pi^0 pi^0 has an unexpectedly high branching ratio. We show that both features can be understood in terms of strong-interaction mixing of pi pi and D Dbar channels in the isospin-zero state, an effect that is important because of the large experimentally observed ratio Gamma(B^0 / Bbar^0 -> D^+ D^-) / Gamma (B^0 / Bbar^0 -> pi^+ pi^-) approx. 50. Our dynamical model correlates the branching ratios and the CP-violating parameters C and S, for the decays B^0 (Bbar^0) -> pi^+ pi^-, B^0 (Bbar^0) -> pi^0 pi^0, B^0 (Bbar^0) -> D^+ D^- and B^0 (Bbar^0) -> D^0 Dbar^0.Comment: 10 pages, 2 figures, 1 table; v2: Misprint corrected in Eq. (12), second line: -a_m replaced by +a_m. To appear in Phys. Lett.

    Fc receptor-mediated immunity against Bordetella pertussis

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    The relevance of specific Abs for the induction of cellular effector functions against Bordetella pertussis was studied. IgG-opsonized B. pertussis was efficiently phagocytosed by human polymorphonuclear leukocytes (PMN). This process was mediated by the PMN IgG receptors, FcγRIIa (CD32) and FcγRIIIb (CD16), working synergistically. Furthermore, these FcγR triggered efficient PMN respiratory burst activity and mediated transfer of B. pertussis to lysosomal compartments, ultimately resulting in reduced bacterial viability. Bacteria opsonized with IgA triggered similar PMN activation via FcαR (CD89). Simultaneous engagement of FcαRI and FcγR by B. pertussis resulted in increased phagocytosis rates, compared with responses induced by either isotype alone. These data provide new insights into host immune mechanisms against B. pertussis and document a crucial role for Ig-FcR interactions in immunity to this human pathogen.Centro de Investigación y Desarrollo en Fermentaciones Industriale

    Fc receptor-mediated immunity against Bordetella pertussis

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    The relevance of specific Abs for the induction of cellular effector functions against Bordetella pertussis was studied. IgG-opsonized B. pertussis was efficiently phagocytosed by human polymorphonuclear leukocytes (PMN). This process was mediated by the PMN IgG receptors, FcγRIIa (CD32) and FcγRIIIb (CD16), working synergistically. Furthermore, these FcγR triggered efficient PMN respiratory burst activity and mediated transfer of B. pertussis to lysosomal compartments, ultimately resulting in reduced bacterial viability. Bacteria opsonized with IgA triggered similar PMN activation via FcαR (CD89). Simultaneous engagement of FcαRI and FcγR by B. pertussis resulted in increased phagocytosis rates, compared with responses induced by either isotype alone. These data provide new insights into host immune mechanisms against B. pertussis and document a crucial role for Ig-FcR interactions in immunity to this human pathogen.Centro de Investigación y Desarrollo en Fermentaciones Industriale

    CP-Violation in the decay B^0, (B^0)bar -> pi^+ pi^- gamma

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    The decay (B^0)bar -> pi^+ pi^- gamma has a bremsstrahlung component determined by the amplitude for (B^0)bar -> pi^+ pi^-, as well as a direct component determined by the penguin interaction V_tb V^*_td c_7 O_7. Interference of these amplitudes produces a photon energy spectrum d Gamma/d x = a/x + b + c_1 x + c_2 x^2 + ... (x = 2 E_gamma/m_B) where the terms c_1,2 contain a dependence on the phase alpha_eff = pi - arg[(V_tb V^*_td)^* Amp((B^0)bar -> pi^+ pi^-)]. We also examine the angular distribution of these decays, and show that in the presence of strong phases, an untagged B^0/(B^0)bar beam can exhibit an asymmetry between the pi^+ and pi^- energy spectra.Comment: 11 pages, 4 figures, 1 table In abstract and in Eq. (17), a + b/x corrected to a/x + b. Slight improvement in Figs. 1b, 2c and 2
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