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http://hdl.handle.net/2440/12353
2014-10-20T11:21:09ZQuasifixed point scenarios and the Higgs mass in the E₆ inspired supersymmetric models
http://hdl.handle.net/2440/86363
Title: Quasifixed point scenarios and the Higgs mass in the E₆ inspired supersymmetric models
Author: Nevzorov, R.
Abstract: We analyze the two-loop renormalization group (RG) flow of the gauge and Yukawa couplings within the E6 inspired supersymmetric models with extra U(1)N gauge symmetry under which right-handed neutrinos have zero charge. In these models, single discrete Z˜H2 symmetry forbids the tree-level flavor-changing transitions and the most dangerous baryon and lepton number violating operators. We consider two different scenarios A and B that involve extra matter beyond the minimal supersymmetric Standard Model contained in three and four 5+5¯ representations of SU(5), respectively, plus three SU(5) singlets which carry U(1)N charges. In scenario A, the measured values of the SU(2)W and U(1)Y gauge couplings lie near the fixed points of the RG equations. In scenario B, the contribution of two-loop corrections spoils the unification of gauge couplings, resulting in the appearance of the Landau pole below the grand unification scale MX. The solutions for the Yukawa couplings also approach the quasifixed points with increasing their values at the scale MX. We calculate the two-loop upper bounds on the lightest Higgs boson mass in the vicinity of these quasifixed points and compare the results of our analysis with the corresponding ones in the next-to-minimal supersymmetric Standard Model. In all these cases, the theoretical restrictions on the Standard-Model-like Higgs boson mass are rather close to 125 GeV.2013-12-31T13:30:00ZSpin and orbital angular momentum in the proton
http://hdl.handle.net/2440/86238
Title: Spin and orbital angular momentum in the proton
Author: Thomas, A.W.
Abstract: Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of the problem, showing that not only have strong upper limits have been placed on the amount of polarized glue in the proton but that the experimental determination of the spin content has become much more precise. It is now clear that the origin of the discrepancy between experiment and the naive expectation of the fraction of spin carried by the quarks and anti-quarks in the proton lies in the non-perturbative structure of the proton. We explain how the features expected in a modern, relativistic and chirally symmetric description of nucleon structure naturally explain the current data. The consequences of this explanation for the presence of orbital angular momentum on quarks and gluons is reviewed and comparison made with recent results from lattice QCD and experimental data.2008-12-31T13:30:00ZCentre vortices and the quark propagator
http://hdl.handle.net/2440/86195
Title: Centre vortices and the quark propagator
Author: Bowman, P.O.; Langfeld, K.; O'Cais, A.; Leinweber, D.B.; Sternbeck, A.; Von Smekal, L.; Williams, A.G.; Jens-Kusterer, D.
Abstract: It is thought that confinement and chiral symmetry breaking might be driven by the same mechanism. Centre vortices have long been considered a promising candidate for such a mechanism. We use the Landau-gauge quark propagator as a probe of dynamical chiral symmetry breaking and show that, for SU(2) gauge theory, the infrared behaviour of the quark propagator is indeed dominated by the vortex matter. This is in constrast to the SU(3) theory, where DcSB isseen to survive even on non-confining, vortex-removed configurations.
Description: PoS(ConfinementVIII)0562007-12-31T13:30:00ZObservation of 7 TeV gamma rays from the Crab using the large zenith angle air Čerenkov imaging technique
http://hdl.handle.net/2440/86009
Title: Observation of 7 TeV gamma rays from the Crab using the large zenith angle air Čerenkov imaging technique
Author: Tanimori, T.; Tsukagoshi, T.; Kifune, T.; Edwards, P.G.; Fujimoto, M.; Hara, T.; Hayashida, N.; Matsubara, Y.; Mizumoto, Y.; Muraki, Y.; Ogio, S.; Patterson, J.; Roberts, M.D.; Rowell, G.; Suda, T.; Tamura, T.; Teshima, M.; Thornton, G.J.; Watase, Y.; Yoshikoshi, T.
Abstract: We have observed the Crab pulsar/nebula from 1992 December to 1993 January to search for very high energy gamma rays, using an imaging air Cerenkov telescope of 3.8 m diameter, located at Woomera, Australia. Since the observation was carried out in the southern hemisphere, the zenith angle of the object is large, which results in a maximum sensitivity of approximately 10-13/cm2/sec with approximately 7 TeV threshold energy for detected gamma rays. With high angular resolution, the Cerenkov imaging technique is found to be useful at zenith angles 53 to 56 deg. We report here possible evidence of detection with 4 sigma significance of very high energy gamma-rays above approximately 7 TeV from the Crab pulsar/nebula. The integral flux is estimated to be (7.6 plus or minus 1.9) x 10-13/cm2/sec. The result is consistent with the revised spectrum of the Crab recently reported by the Whipple group (Lewis et al. 1993).1993-12-31T13:30:00Z