451 research outputs found

    The Role of CP violation in D0 anti-D0 Mixing

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    In current searches for D0 anti-D0 mixing, the time evolution of ``wrong-sign'' decays is used to distinguish between a potential mixing signal and the dominant background from doubly-Cabibbo-suppressed decays. A term proportional to ΔMt\Delta Mt in the expression for the time evolution is often neglected in theoretical discussions and experimental analyses of these processes. We emphasize that, in general, this term does not vanish even in the case of CP invariance. Furthermore, CP invariance is likely to be violated if the rate of D0 anti-D0 mixing is close to the experimental bound. The consequence of either of these two facts is that the strongest existing measured bound is not applicable for constraining New Physics.Comment: 14 pages, uuencoded gzip-compressed postscript (84 kB

    Vector Leptoquark Pair Production in e+eÔłĺe^+e^- Annihilation

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    The cross section for vector leptoquark pair production in e+eÔłĺe^+e^- annihilation is calculated for the case of finite anomalous gauge boson couplings ╬║╬│,Z\kappa_{\gamma, Z} and ╬╗╬│,Z\lambda_{\gamma, Z}. The minimal cross section is found to behave ÔłŁ╬▓7\propto \beta^7, leading to weaker mass bounds in the threshold range than in models studied previously.Comment: 10 pages Latex, including 5 eps-figure

    Proton Stability in Leptoquark Models

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    We show that in generic leptoquark (LQ) extensions of the standard model lepton and baryon numbers are broken at the level of renormalizable operators. In particular, this may cause fast proton decay unless the leptoquarks are heavy enough. We derive stringent bounds for the 1st generation LQ masses and couplings from the proton stability constraints.Comment: 7 pages, 1 tabl

    Perceptions of service providers and parents regarding improving outcomes of young children living in circumstances of disadvantage

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    Many children live in circumstances which make it difficult for them to develop the capacities needed to succeed later in life. Previous research has focused on determining the risk factors for impaired outcomes and on evaluating the impact of specific programs. There has been a lack of research exploring the wisdom of people at the grassroots level and across programs. This research asked service providers and parents to describe the challenges that are faced by families with young children living in circumstances of disadvantage, the barriers preventing participation in programs, and the strategies that would address these challenges and barriers. Three research approaches were incorporated into the design of this project; qualitative policy research, community-based participatory research, and knowledge transfer methodology. These approaches were applied in order to encourage the participation of community organizations, to produce information that would provide guidance to policy-makers, and to promote implementation of the strategies recommended by research participants. In Phase One, 28 service providers from 24 Regina programs were interviewed. In Phase Two, the results from the service provider interviews were presented to focus groups of target parents to obtain their feedback. This process served to acknowledge the expertise of the parents as those with firsthand experience of their own reality. The categories of challenges, barriers and strategies that were identified by participants were psychosocial (related to personal connections and mental well-being) and/or structural (concrete and tangible issues). Four themes emerged from these findings. First, interrelatedness and synergistic interaction among the social conditions faced by these families was evident. Second, instability was present at both familial and program delivery levels. Third, target families faced power imbalances from multiple sources. Finally, a lack of belonging or connectedness was experienced by families as a result of their circumstances of social exclusion. The results point to the need for policies to address the following areas: adequate household income, childcare, funding of non-government organizations, housing, and mental health and addictions. By presenting the views of people at the grassroots level, it is hoped that these research results will provide direction to policy-makers

    Baryogenesis from the Kobayashi-Maskawa Phase

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    The Standard Model fulfills the three Sakharov conditions for baryogenesis. The smallness of quark masses suppresses, however, the CP violation from the Kobayashi-Maskawa phase to a level that is many orders of magnitude below what is required to explain the observed baryon asymmetry. We point out that if, as a result of time variation in the Yukawa couplings, quark masses were large at the time of the electroweak phase transition, then the Kobayashi-Maskawa mechanism could be the source of the asymmetry. The Froggatt-Nielsen mechanism provides a plausible framework where the Yukawa couplings could all be of order one at that time, and settle to their present values before nucleosynthesis. The problems related to a strong first order electroweak phase transition may also be alleviated in this framework. Our scenario reveals a loophole in the commonly held view that the Kobayashi-Maskawa mechanism cannot be the dominant source of CP violation to play a role in baryogenesis.Comment: 4 page

    Leptoquark Production in Electron-Photon Scattering

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    We perform a model independent analysis of the production of scalar and vector leptoquarks in the eÔłĺ╬│e^-\gamma mode of a linear collider of the next generation. Since these leptoquarks are produced singly, higher masses can be probed than in other collider modes, like e+eÔłĺe^+e^- scattering. We discuss the discovery potential and show how polarization and angular distributions can be used to distinguish between the different types of leptoquarks.Comment: Major mistakes corrected and references added. The previous version should be discarde
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