445 research outputs found

    Reply to "Comment on 'Isotope effect in multi-band and multi-channel attractive systems and inverse isotope effect in iron-based superconductors'"

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    The Comment insists on the following: in our model it is assumed that the effective interactions have specific energy ranges within the single band with a cutoff at \omega_1 for the phononic part and a range from \omega_1 to \omega_2 in the AF channel. Our reply is that we assume that V_i(k,k')\neq 0 if |\xi_k|<\omega_i and |\xi_{k'}|<\omega_i, and otherwise V_i(k,k')= 0 (i=1,2), as stated in our paper. This is the model of BCS type with two attractive interactions, and this assumption is the characteristic of the BCS approximation. The claim "the integration limits have been modified such that the AF channel mediated pairing sets in where the ph-channel pairing terminates and is limited at an energy given by \omega_j=\omega_{AF}" in the Comment is wrong. We describe the model and the method to solve the gap equation in more detail

    Pair production of charged Higgs scalars from electroweak gauge boson fusion

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    We compute the contribution to charged Higgs boson pair production at the Large Hadron Collider (LHC) due to the scattering of two electroweak (EW) gauge bosons, these being in turn generated via bremsstrahlung off incoming quarks: q q --> q q V^*V^* --> q q H^+H^- (V=gamma,Z,W^{+/-}). We verify that the production cross section of this mode is tan beta independent and show that it is smaller than that of H^+H^- production via q q-initiated processes but generally larger than that of the loop-induced channel gg --> H^+H^-. Pair production of charged Higgs bosons is crucial in order to test EW symmetry breaking scenarios beyond the Standard Model (SM). We show that the detection of these kind of processes at the standard LHC is however problematic, because of their poor production rates and the large backgrounds.Comment: 22 pages, latex, 8 figures (largely revised version to appear in JPG

    Flavour structure of low-energy hadron pair photoproduction

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    We consider the process γγ→H1Hˉ2\gamma\gamma\to H_1\bar H_2 where H1H_1 and H2H_2 are either mesons or baryons. The experimental findings for such quantities as the ppˉp\bar p and KSKSK_SK_S differential cross sections, in the energy range currently probed, are found often to be in disparity with the scaling behaviour expected from hard constituent scattering. We discuss the long-distance pole--resonance contribution in understanding the origin of these phenomena, as well as the amplitude relations governing the short-distance contribution which we model as a scaling contribution. When considering the latter, we argue that the difference found for the KSKSK_SK_S and the K+K−K^+K^- integrated cross sections can be attributed to the s-channel isovector component. This corresponds to the ρω→a\rho\omega\to a subprocess in the VMD (vector-meson-dominance) language. The ratio of the two cross sections is enhanced by the suppression of the ϕ\phi component, and is hence constrained. We give similar constraints to a number of other hadron pair production channels. After writing down the scaling and pole--resonance contributions accordingly, the direct summation of the two contributions is found to reproduce some salient features of the ppˉp\bar p and K+K−K^+K^- data.Comment: 12 pages, 9 figures, revised version to be published in EPJ

    Next-to-Leading order Higgs + 2 jet production via gluon fusion

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    We present phenomenological results for the production of a Higgs boson in association with two jets at the LHC. The calculation is performed in the limit of large top mass and is accurate to next-to-leading order in the strong coupling, i.e. O(αs6){\cal O}(\alpha_s^6)Comment: 13 pages, 6 figures; v2: references added, modified acknowledgments, final version as published in JHE

    Dissociative photoionization of the NO molecule studied by photoelectron-photon coincidence technique

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    Low-energy photoelectron–vacuum ultraviolet (VUV) photon coincidences have been measured using synchrotron radiation excitation in the inner-valence region of the nitric oxide molecule. The capabilities of the coincidence set-up were demonstrated by detecting the 2s−1 → 2p−1 radiative transitions in coincidence with the 2s photoelectron emission in Ne. In NO, the observed coincidence events are attributed to dissociative photoionization with excitation, whereby photoelectron emission is followed by fragmentation of excited NO+ ions into O+ + N* or N+ + O* and VUV emission from an excited neutral fragment. The highest coincidence rate occurs with the opening of ionization channels which are due to correlation satellites of the 3σ photoionization. The decay time of VUV photon emission was also measured, implying that specific excited states of N atoms contribute significantly to observed VUV emission
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