Chen, P., Centelles Chulia, S., Ding, G. J., Srivastava, R., & Valle, J. W. F. (2019). CP symmetries as guiding posts: revamping tri-bi-maximal mixing. Part I. J. High Energy Phys., 03(3), 036–27pp.
Abstract: We analyze the possible generalized CP symmetries admitted by the Tri-Bi-Maximal (TBM) neutrino mixing. Taking advantage of these symmetries we construct in a systematic way other variants of the standard TBM Ansatz. Depending on the type and number of generalized CP symmetries imposed, we get new mixing matrices, all of which related to the original TBM matrix. One of such revamped TBM variants is the recently discussed mixing matrix of arXiv:1806.03367. We also briefly discuss the phenomenological implications following from these mixing patterns.
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Dai, L. R., Wang, G. Y., Chen, X., Wang, E., Oset, E., & Li, D. M. (2019). The B+ -> J/phi omega K+ reaction and D*(D)over-bar* molecular states. Eur. Phys. J. A, 55(3), 36–7pp.
Abstract: We study the B+J/K+ reaction, and show that it is driven by the presence of two resonances, the X(3940) and X(3930), that are of molecular nature and couple most strongly to D*D*, but also to J/. Because of that, in the J/ mass distribution we find a peak related to the excitation of the resonances and a cusp with large strength at the D*D* threshold.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Search for CP violation using triple product asymmetries in Lambda(0)(b) -> pK(-) pi(+) pi(-), Lambda(0)(b) -> pK(-) K+ K- and Xi(0)(b) -> pK(-) K- pi(+) decays. J. High Energy Phys., 08(8), 039–27pp.
Abstract: A search for CP and P violation using triple- product asymmetries is performed with Lambda(0)(b) -> pK(-) pi(+) pi(-), Lambda(0)(b) -> pK(-) K+ K- and Xi(0)(b) -> pK(-) K- pi(+) decays. The data sample corresponds to integrated luminosities of 1.0 fb(-1) and 2.0 fb(-1), recorded with the LHCb detector at centre- of- mass energies of 7TeV and 8TeV, respectively. The CP- and P-violating asymmetries are measured both integrating over all phase space and in speci fi c phase- space regions. No signi fi cant deviation from CP or P symmetry is found. The fi rst observation of Lambda(0)(b) -> pK(-) chi(c0) (1P)(->pi(+) pi(-), K+ K-) decay is also reported.
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Escudero, M., Hooper, D., Krnjaic, G., & Pierre, M. (2019). Cosmology with a very light Lmu – Ltau gauge boson. J. High Energy Phys., 03(3), 071–29pp.
Abstract: In this paper, we explore in detail the cosmological implications of an abelian L – L gauge extension of the Standard Model featuring a light and weakly coupled Z. Such a scenario is motivated by the longstanding approximate to 4 sigma discrepancy between the measured and predicted values of the muon's anomalous magnetic moment, (g – 2), as well as the tension between late and early time determinations of the Hubble constant. If sufficiently light, the Z population will decay to neutrinos, increasing the overall energy density of radiation and altering the expansion history of the early universe. We identify two distinct regions of parameter space in this model in which the Hubble tension can be significantly relaxed. The first of these is the previously identified region in which a approximate to 10 – 20 MeV Z reaches equilibrium in the early universe and then decays, heating the neutrino population and delaying the process of neutrino decoupling. For a coupling of g (-) similar or equal to (3 – 8) x 10(-4), such a particle can also explain the observed (g – 2) anomaly. In the second region, the Z is very light (mZ approximate to 1eV to MeV) and very weakly coupled (g (-) approximate to 10(-13) to 10(-9)). In this case, the Z population is produced through freeze-in, and decays to neutrinos after neutrino decoupling. Across large regions of parameter space, we predict a contribution to the energy density of radiation that can appreciably relax the reported Hubble tension, N-eff similar or equal to 0.2.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., et al. (2019). Search for pair production of Higgs bosons in the b(b)over-barb(b)over-bar final state using proton-proton collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 01(1), 030–49pp.
Abstract: A search for Higgs boson pair production in the bbbb final state is carried out with up to 36.1 fb(-1) of LHC proton-proton collision data collected at s=13 TeV with the ATLAS detector in 2015 and 2016. Three benchmark signals are studied: a spin-2 graviton decaying into a Higgs boson pair, a scalar resonance decaying into a Higgs boson pair, and Standard Model non-resonant Higgs boson pair production. Two analyses are carried out, each implementing a particular technique for the event reconstruction that targets Higgs bosons reconstructed as pairs of jets or single boosted jets. The resonance mass range covered is 260-3000 GeV. The analyses are statistically combined and upper limits on the production cross section of Higgs boson pairs times branching ratio to bbbb are set in each model. No significant excess is observed; the largest deviation of data over prediction is found at a mass of 280 GeV, corresponding to 2.3 standard deviations globally. The observed 95% confidence level upper limit on the non-resonant production is 13 times the Standard Model prediction.
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