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Overview on neutrinos and the Daya Bay experiment
Miao He
Frontiers of Physics. 2013, 8 (3 ): 242-247.
https://doi.org/10.1007/s11467-013-0296-x
Neutrinos are elementary particles in the Standard Model. Neutrino oscillation is a quantum mechanical phenomenon beyond the Standard Model. Neutrino oscillation can be described by two independent mass-squared di.erences Δ m 21 2 , Δ m 31 2 (or Δ m 32 2 ) and a3×3 unitary matrix, containing three mixing angles θ 12 , θ 23 , θ 13 , and one charge-parity (CP) phase. θ 12 is about 34° and determined by solar neutrino experiments and the reactor neutrino experiment KamLAND. θ 23 is about 45° and determined by atmospheric neutrino experiments and accelerator neutrino experiments. θ 13 can be measured by either accelerator or reactor neutrino experiments. On Mar. 8, 2012, the Daya Bay Reactor Neutrino Experiment reported the .rst observation of non-zero θ 13 with 5.2 standard deviations. In June, with 2.5× previous data, Daya Bay improved the measurement of sin2 2 θ 13 = 0.089±0.010(stat)±0.005(syst).
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Higgs boson searches at the Tevatron
Gavin J. Davies, on behalf of the CDF and D0 Collaborations
Frontiers of Physics. 2013, 8 (3 ): 270-284.
https://doi.org/10.1007/s11467-013-0293-0
This article reviews the Higgs searches at the Tevatron, as presented over the summer of 2012; both standard model (SM) and beyond the standard model (BSM) results are discussed as detailed (arXiv: 1207.0449; Phys. Rev. Lett., 2012, 109: 071804; Phys. Rev. D, 2012, 85: 032005).We discuss the combination of searches by the CDF and D0 Collaborations for the standard model Higgs boson in the mass range 100-200 GeV/c 2 produced in the the gg →H , WH , ZH , t t ˉ H , and vector boson fusion production modes, and decaying in the H → b b ˉ , H →W + W - , H →ZZ , H →τ + τ - , and H →γγ modes. The data, collected at the Fermilab Tevatron collider inp p ˉ collisions at s = 1.96 TeV, correspond to integrated luminosities of up to 10 fb-1 . In the absence of signal, we expect to exclude the regions 100<mH <120 GeV/c 2 and 139<mH <184 GeV/c 2 . We exclude, at the 95% C.L., two regions: 100<mH <103 GeV/c 2 , and 147<mH <180 GeV/c 2 . We observe a signi.cant excess of events in the mass range between 115 and 140 GeV/c 2 . The local signi.cance corresponds to 3.0 standard deviations at mH =120 GeV/c 2 ; the global signi.cance (incorporating the lookelsewhere e.ect) for such an excess anywhere in the full mass range investigated is approximately 2.5 standard deviations. Furthermore, we separately combine searches for H → b b ˉ , H →W + W - and H →γγ. We find that the excess is concentrated in the H →bb ˉ channel, appearing in the searches over a broad range of mH ; the maximum local significance of 3.3 standard deviations corresponds to a global significance of approximately 3.1 standard deviations. The observed signal strengths in all channels are consistent with the expectation for a standard model Higgs boson at mH = 125 GeV/c 2 . The production of neutral Higgs bosons in association with b -quarks can be significantly enhanced in various beyond the standard model scenarios, including Supersymmetry. The recent combination of such searches from the two collaborations is discussed.
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Ground states, solitons and spin textures in spin-1 Bose–Einstein condensates
Shu-Wei Song, Lin Wen, Chao-Fei Liu, S.-C. Gou, Wu-Ming Liu
Frontiers of Physics. 2013, 8 (3 ): 302-318.
https://doi.org/10.1007/s11467-013-0350-8
We present an overview of our recent theoretical studies on the quantum phenomena of the spin-1 Bose–Einstein condensates, including the phase diagram, soliton solutions and the formation of the topological spin textures. A brief exploration of the effects of spin–orbit coupling on the ground-state properties is given.We put forward proposals by using the transmission spectra of an optical cavity to probe the quantum ground states: the ferromagnetic and polar phases. Quasi-one-dimension solitons and ring dark solitons are studied. It is predicted that characteristics of the magnetic solitons in optical lattice can be tuned by controlling the long-range light-induced and static magnetic dipoledipole interactions; solutions of single-component magnetic and single-, two-, three-components polar solitons are found; ring dark solitons in spin-1 condensates are predicted to live longer lifetimes than that in their scalar counterparts. In the formation of spin textures, we have considered the theoretical model of a rapidly quenched and fast rotating trapped spin-1 Bose–Einstein condensate, whose dynamics can be studied by solving the stochastic projected Gross–Pitaevskii equations. Spontaneous generation of nontrivial topological defects, such as the hexagonal lattice skyrmions and square lattice of half-quantized vortices was predicted. In particular, crystallization of merons (half skyrmions) can be generated in the presence of spin–orbit coupling.
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Recent development in SU (3) covariant baryon chiral perturbation theory
Li-Sheng Geng
Frontiers of Physics. 2013, 8 (3 ): 328-348.
https://doi.org/10.1007/s11467-013-0327-7
Baryon chiral perturbation theory (BChPT), as an effective field theory of low-energy quantum chromodynamics (QCD), has played and is still playing an important role in our understanding of non-perturbative strong-interaction phenomena. In the past two decades, inspired by the rapid progress in lattice QCD simulations and the new experimental campaign to study the strangeness sector of low-energy QCD, many efforts have been made to develop a fully covariant BChPT and to test its validity in all scenarios. These new endeavours have not only deepened our understanding of some long-standing problems, such as the power-counting-breaking problem and the convergence problem, but also resulted in theoretical tools that can be confidently applied to make robust predictions Particularly, the manifestly covariant BChPT supplemented with the extended-on-mass-shell (EOMS) renormalization scheme has been shown to satisfy all analyticity and symmetry constraints and converge relatively faster compared to its non-relativistic and infrared counterparts. In this article, we provide a brief review of the fully covariant BChPT and its latest applications in the u , d , and s three-flavor sector.
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