BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Search for mixing-induced CP violation using partial reconstruction of (B)over-bar(0) -> D*(+)Xl(-)(nu)over-bar(l) and kaon tagging. Phys. Rev. D, 93(3), 032001–13pp.
Abstract: We describe in detail a previously published measurement of CP violation in B-0-(B) over bar (0) oscillations, based on an integrated luminosity of 425.7 fb(-1) collected by the BABAR experiment at the PEPII collider. We apply a novel technique to a sample of about 6 million (B) over bar (0) -> D*(+)l(-)(nu) over bar (l) decays selected with partial reconstruction of the D*(+) meson. The charged lepton identifies the flavor of one B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine a CP violating asymmetry A(CP) = (N((BB0)-B-0) – N((B) over bar (0)(B) over bar (0)))/(N((BB0)-B-0) + N((B) over bar (0)(B) over bar (0))) = (0.06 +/- 0.17(-0.32)(+0.38))% corresponding to Delta(CP) = 1-vertical bar q/p vertical bar = (0.29 +/- 0.84(-1.61)(+1.88)) x 10(-3). This measurement is consistent and competitive with those obtained at the B factories with dilepton events.
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Abbas, G., Abyaneh, M. Z., Biswas, A., Gupta, S., Patra, M., Rajasekaran, G., et al. (2016). High scale mixing relations as a natural explanation for large neutrino mixing. Int. J. Mod. Phys. A, 31(17), 1650095–47pp.
Abstract: The origin of small mixing among the quarks and a large mixing among the neutrinos has been an open question in particle physics. In order to answer this question, we postulate general relations among the quarks and the leptonic mixing angles at a high scale, which could be the scale of Grand Unified Theories. The central idea of these relations is that the quark and the leptonic mixing angles can be unified at some high scale either due to some quark lepton symmetry or some other underlying mechanism and as a consequence, the mixing angles of the leptonic sector are proportional to that of the quark sector. We investigate the phenomenology of the possible relations where the leptonic mixing angles are proportional to the quark mixing angles at the unification scale by taking into account the latest experimental constraints from the neutrino sector. These relations are able to explain the pattern of leptonic mixing at the low scale and thereby hint that these relations could be possible signatures of a quark lepton symmetry or some other underlying quark lepton mixing unification mechanism at some high scale linked to Grand Unified Theories.
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Hernandez-Pinto, R. J., Sborlini, G. F. R., & Rodrigo, G. (2016). Towards gauge theories in four dimensions. J. High Energy Phys., 02(2), 044–14pp.
Abstract: The abundance of infrared singularities in gauge theories due to unresolved emission of massless particles (soft and collinear) represents the main difficulty in perturbative calculations. They are typically regularized in dimensional regularization, and their subtraction is usually achieved independently for virtual and real corrections. In this paper, we introduce a new method based on the loop-tree duality (LTD) theorem to accomplish the summation over degenerate infrared states directly at the integrand level such that the cancellation of the infrared divergences is achieved simultaneously, and apply it to reference examples as a proof of concept. Ultraviolet divergences, which are the consequence of the point-like nature of the theory, are also reinterpreted physically in this framework. The proposed method opens the intriguing possibility of carrying out purely four-dimensional implementations of higher-order perturbative calculations at next-to-leading order (NLO) and beyond free of soft and final-state collinear subtractions.
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Rinaldi, M., Scopetta, S., Traini, M., & Vento, V. (2016). Double parton scattering: A study of the effective cross section within a Light-Front quark model. Phys. Lett. B, 752, 40–45.
Abstract: We present a calculation of the effective cross section sigma(eff), an important ingredient in the description of double parton scattering in proton-proton collisions. Our theoretical approach makes use of a Light-Front quark model as a framework to calculate the double parton distribution functions at low-resolution scale. QCD evolution is implemented to reach the experimental scale. The obtained values of sigma(eff) in the valence region are consistent with the present experimental scenario, in particular with the sets of data which include the same kinematical range. However the result of the complete calculation shows a dependence of sigma(eff) on x(i), a feature not easily seen in the available data, probably because of their low accuracy. Measurements of sigma(eff) in restricted x(i) regions are addressed to obtain indications on double parton correlations, a novel and interesting aspect of the three dimensional structure of the nucleon.
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Baek, S., Ko, P., Park, M., Park, W. I., & Yu, C. (2016). Beyond the dark matter effective field theory and a simplified model approach at colliders. Phys. Lett. B, 756, 289–294.
Abstract: Direct detection of and LHC search for the singlet fermion dark matter (SFDM) model with Higgs portal interaction are considered in a renormalizable model where the full Standard Model (SM) gauge symmetry is imposed by introducing a singlet scalar messenger. In this model, direct detection is described by an effective operator m(q)(q) over barq (chi) over bar chi as usual, but the full amplitude for monojet + is not an element of(T) involves two intermediate scalar propagators, which cannot be seen within the effective field theory (EFT) or in the simplified model without the full SM gauge symmetry. We derive the collider bounds from the ATLAS monojet + is not an element of(T) as well as the CMS t (t) over bar + is not an element of(T) data, finding out that the bounds and the interpretation of the results are completely different from those obtained within the EFT or simplified models. It is pointed out that it is important to respect unitarity, renormalizability and local gauge invariance of the SM.
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