118028911
Cogeneration of dark matter and baryons by non-standard-model sphalerons in unified models
A bstractSphalerons of a new gauge interaction can convert a primordial asymmetry in B or L into a dark matter asymmetry. From the equilibrium conditions for the sphalerons of both the electroweak and the new interactions, one can compute the ratios of B, L, and X, where X is the dark matter number, thus determining the mass of the dark matter particle fairly precisely. Such a scenario can arise naturally in the context of unification with larger groups. An illustrative model embeddable in SU(6) × SU(2) ⊂ E6 is described in detail as well as an equally simple model based on SU(7).
118658279
A simple grand unified relation between neutrino mixing and quark mixing
A bstractIt is proposed that all flavor mixing is caused by the mixing of the three quark and lepton families with vectorlike fermions in $ 5+\bar{5} $ multiplets of SU(5). This simple assumption implies that both VCKM and UM N S are generated by a single matrix. The entire 3 × 3 complex mass matrix of the neutrinos Mv is then found to have a simple expression in terms of two complex parameters and an overall scale. Thus, all the presently unknown neutrino parameters are predicted. The best fits are for θatm ≲ 40°. The leptonic Dirac CP phase is found to be somewhat greater than π.
119197432
Proton decay and the origin of quark and lepton mixing
A bstractIt was recently proposed that all flavor mixing has a single source, namely the mixing of the three quark and lepton families with “extra” vectorlike fermions in 5 + $ \overline{5} $ multiplets of SU(5). This was shown to lead to several testable predictions including neutrino masses and CP-violating phases. Here it is shown that the mixing angles within grand unified fermion multiplets are also predicted. Proton decay branching ratios would thus give several independent tests of the model. Certain model parameters could be determined independently from the quark and lepton spectrum and from proton decay.
198142987
Permanent magnet system of alpha magnetic spectrometer
Alpha magnetic spectrometer (AMS) is the first large magndtic spectrometer in space. Its precursor flioht was completed successfully in June 1998. The key part of AMS is the permanent magnet system, which was built by the lnstitute of Electric Engineering, the institute of High Energy Physics and the Chinese Academy of Launch Vehicle Technology. This system includes a permanent magnet made of high grade NdFeB and a support structure. The unique design of the permanent magnet based on the magic ring fulfills the severe requirements on the magnetic field leakage and the dipole moment for space experiments. The permanent magnet weighs about 2 tons, and provides a geometric acceptance of 0.6 m2 · sr and an analyzing powerBL2 of 0.135 T · m2. It works up to 40°C without demagnetization. The main structure is a thin double shell, which undergoes the strong magnetic force and torque of the permanent magnet, as well as the large load during launching and landing. The permanent magnet system fulfills the requirements from AMS, and satisfies the strict safety standards of NASA.
118457882
Towards a warped inflationary brane scanning
We present a detailed systematics for comparing warped brane inflation with the observations, incorporating the effects of both moduli stabilization and ultraviolet bulk physics. We explicitly construct an example of the inflaton potential governing the motion of a mobile D3 brane in the entire warped deformed conifold. This allows us to precisely identify the corresponding scales of the cosmic microwave background. The effects due to bulk fluxes or localized sources are parametrized using gauge/string duality. We next perform some sample scannings to explore the parameter space of the complete potential, and first demonstrate that without the bulk effects there can be large degenerate sets of parameters with observationally consistent predictions. When the bulk perturbations are included, however, the observational predictions are generally spoiled. For them to remain consistent, the magnitudes of the additional bulk effects need to be highly suppressed.
118433127
Constraints on large-extra-dimensions model through 125 GeV Higgs pair production at the LHC
Based on the analysis of 5 fb−1 of data at the LHC, the ATLAS and CMS collaborations have presented evidence for a Higgs boson with a mass in the 125 GeV range. We consider the 125 GeV neutral Higgs pair production process in the context of large-extra-dimensions (LED) model including the Kaluza–Klein (KK) excited gravitons at the LHC. We consider the standard model (SM) Higgs pair production in gluon–gluon fusion channel and pure LED effects through graviton exchange as well as their interferences. It is shown that such interferences should be included; the LED model raises the transverse momentum (Pt) and invariant mass (MHH) distributions at high scales of Pt and MHH of the Higgs pair production. By using the Higgs pair production we could set the discovery limit on the cutoff scale MS up to 6 TeV for δ=2 and 4.5 TeV for δ=6.
119277497
Meson exchange effects in elastic ep scattering at loop level and the electromagnetic form factors of the proton
A new form of two-photon exchange (TPE) effect is studied to explain the discrepancy between unpolarized and polarized experimental data in elastic ep scattering. The mechanism is based on a simple idea that apart from the usual TPE effects from box and crossed-box diagrams, the mesons may also be exchanged in elastic ep scattering by two-photon coupling at loop level. The detailed study shows such contributions to reduced unpolarized cross section (sigma(un)) and polarized observables (P-t, P-l) at fixed Q(2) are only dependent on proton's electromagnetic form factors G(E,M) and a new unknown universal parameter g. After combining this contribution with the usual TPE contributions from box and crossed-box diagrams, the ratio mu(p)G(E)/G(M) extracted from the recent precise unpolarized and polarized experimental data can be described consistently.
122433573
The segmentation of hadron calorimeters
Abstract Optimization of the segmentation of large hadron calorimeters is important in order to obtain good resolution for jet physics at minimum construction cost for the next generation of high energy experiments. The principles of the segmentation of hadron calorimeters are discussed. As an example, the Monte Carlo optimization of the segmentation of the L3 hadron calorimeter barrel at CERN is described. Comparisons of results for the reconstructed jet shapes show that the optimum number ADC channels is about 20K for the readout of 450K wires of the proportional chambers. The matching between the sandwiched φ towers and Z towers is the dominant factor for angular resolution. Based on these Monte Carlo simulations, an optimized tower structure is obtained.