511 research outputs found

    Phase coherent transport in SrTiO3/LaAlO3 interfaces

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    The two dimensional electron gas formed between the two band insulators SrTiO3 and LaAlO3 exhibits a variety of interesting physical properties which make it an appealing material for use in future spintronics and/or quantum computing devices. For this kind of applications electrons have to retain their phase memory for sufficiently long times or length. Using a mesoscopic size device we were able to extract the phase coherence length, and its temperature variation. We find the dephasing rate to have a power law dependence on temperature. The power depends on the temperature range studied and sheet resistance as expected from dephasing due to strong electron-electron interactions.Comment: Submitted to Phys. Rev

    Production and decay of the neutral top-pion in high energy e+e−e^{+}e^{-} colliders

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    We study the production and decay of the neutral top-pion πt0\pi_{t}^{0} predicted by topcolor-assisted technicolor(TC2) theory. Our results show that, except the dominant decay modes bbˉb\bar{b}, tˉc\bar{t}c and gggg, the πt0\pi_{t}^{0} can also decay into γγ\gamma\gamma and ZÎłZ \gamma modes. It can be significantly produced at high energy e+e−e^{+}e^{-} collider(LC) experiments via the processes e+e−→πt0Îłe^{+}e^{-}\to \pi_{t}^{0}\gamma and e+e−→Zπt0e^{+}e^{-}\to Z\pi_{t}^{0}. We further calculate the production cross sections of the processes e+eâˆ’â†’ÎłÏ€t0→γtˉce^{+}e^{-}\to\gamma\pi_{t}^{0}\to\gamma\bar{t}c and e+e−→Zπt0→Ztˉce^{+}e^{-}\to Z\pi_{t}^{0}\to Z\bar{t}c. We find that the signatures of the neutral top-pion πt0\pi_{t}^{0} can be detected via these processes.Comment: Latex file, 13 Pages, 6 eps figures. to be published in Phys.Rev.

    Single superparticle production via γγ\gamma\gamma collision with explicit R-parity violation

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    We study the single production of scalar neutrinos or charginos via γγ\gamma\gamma collision in an R-parity (RpR_{p}) violating supersymmetric model. It may be possible to detect a sneutrino or a chargino at a Linear Collider (LC) in γγ\gamma \gamma operation mode, as a test of supersymmetry and RpR_p-violation. Because of the clean background in LC, stringent constraints on RpR_p violating parameters can be obtained even if the process cannot be observed at the future Linear Collider.Comment: 13 pages, 15 figure

    Can there be any new physics in b -> d penguins

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    We analyze the possibility of observing new physics effects in the b→db \to d penguin amplitudes. For this purpose, we consider the decay mode B→K0Kˉ0B \to K^0 \bar K^0 , which has only b→db \to d penguin contributions. Using the QCD factorization approach, we find very tiny CP violating effects in the standard model for this process. Furthermore, we show that the minimal supersymmetric standard model with LRLR mass insertion and R-parity violating supersymmetric model can provide substantial CP violation effects. Observation of sizable CP violation in this mode would be a clear signal of new physics.Comment: Published versio

    Flavourful Production at Hadron Colliders

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    We ask what new states may lie at or below the TeV scale, with sizable flavour-dependent couplings to light quarks, putting them within reach of hadron colliders via resonant production, or in association with Standard Model states. In particular, we focus on the compatibility of such states with stringent flavour-changing neutral current and electric-dipole moment constraints. We argue that the broadest and most theoretically plausible flavour structure of the new couplings is that they are hierarchical, as are Standard Model Yukawa couplings, although the hierarchical pattern may well be different. We point out that, without the need for any more elaborate or restrictive structure, new scalars with "diquark" couplings to standard quarks are particularly immune to existing constraints, and that such scalars may arise within a variety of theoretical paradigms. In particular, there can be substantial couplings to a pair of light quarks or to one light and one heavy quark. For example, the latter possibility may provide a flavour-safe interpretation of the asymmetry in top quark production observed at the Tevatron. We thereby motivate searches for diquark scalars at the Tevatron and LHC, and argue that their discovery represents one of our best chances for new insight into the Flavour Puzzle of the Standard Model.Comment: 18 pp., 8 figures, references adde

    Broken R Parity Contributions to Flavor Changing Rates and CP Asymmetries in Fermion Pair Production at Leptonic Colliders

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    We examine the effects of the R parity odd renormalizable interactions on flavor changing rates and CP violation asymmetries in the production of fermion-antifermion pairs at e−−e+e^-- e^+ leptonic colliders. The produced fermions may be leptons, down-quarks or up-quarks, and the center of mass energies may range from the Z-boson pole up to 1000 1000 GeV. Off the Z-boson pole, the flavor changing rates are controlled by tree level amplitudes and the CP asymmetries by interference terms between tree and loop level amplitudes. At the Z-boson pole, both observables involve loop amplitudes. The lepton number violating interactions, associated with the coupling constants, \l_{ijk}, \l'_{ijk}, are only taken into account. The consideration of loop amplitudes is restricted to the photon and Z-boson vertex corrections. We briefly review flavor violation physics at colliders. We present numerical results using a single, species and family independent, mass parameter, m~\tilde m, for all the scalar superpartners and considering simple assumptions for the family dependence of the R parity odd coupling constants.Comment: Latex File. 23 pages. 4 postscript figures. 1 table. Revised version with new results and several corrections in numerical result

    Hasbara 2.0: Israel’s Public Diplomacy in the Digital Age

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    The Internet has been a counter-public space for Palestinian liberation politics for over a decade, and digital technologies have become an increasingly important tool for solidarity groups across the world. However, the Israeli state and Zionist supporters worldwide are harnessing the same technologies and platforms to mobilize technology primarily to increase pro-Israel sentiments. The aims of this article are to examine hasbara [Israeli public diplomacy] through an exploration of similar diplomacy programmes; to illustrate how social media have affected the basic algorithms of hasbara; and to probe the assertions of hasbara in the light of pro-Palestinian solidarity. Through a study of public diplomacy, this article critically analyzes hasbara as a site of contestation and a method that is hampered by contradictions. On the one hand, there has been a massive growth in hasbara in recent years—indicated by the increase in funding for it and by its professionalized and centralized character; and on the other hand, hasbara has attracted sharp critiques in Israel for its reputed failures. To understand this contradiction, hasbara must be placed within the context of Israel’s settler-colonialism, which sets the state apart from other ‘post-conflict’ states. This article reviews the methods utilized in hasbara, as well as their readjustment in the context of recent wars. Events in 2014 illustrate that hasbara actually destabilizes Israel’s diplomacy. Online journalism and the suppression of solidarity for Palestine together stimulate more criticism and, in turn, help to shift public opinion. Paradoxically, therefore, adjustments (‘hasbara 2.0’) have underlined the image of Israel as a colonial power engaged in violent occupation

    The fully differential single-top-quark cross section in next-to-leading order QCD

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    We present a new next-to-leading order calculation for fully differential single-top-quark final states. The calculation is performed using phase space slicing and dipole subtraction methods. The results of the methods are found to be in agreement. The dipole subtraction method calculation retains the full spin dependence of the final state particles. We show a few numerical results to illustrate the utility and consistency of the resulting computer implementations.Comment: 37 pages, latex, 2 ps figure
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