2016 Vol. 40, No. 12
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We study the scalar, vector and tensor two-gluon and trigluon glueball spectra in the framework of the 5-dimension dynamical holographic QCD model, where the metric structure is deformed self-consistently by the dilaton field. For comparison, the glueball spectra are also calculated in the hard-wall and soft-wall holographic QCD models. In order to distinguish glueballs with even and odd parities, we introduce a positive and negative coupling between the dilaton field and glueballs, and for higher spin glueballs, we introduce a deformed 5-dimension mass. With this set-up, there is only one free parameter from the quadratic dilaton profile in the dynamical holographic QCD model, which is fixed by the scalar glueball spectra. It is found that the two-gluon glueball spectra produced in the dynamical holographic QCD model are in good agreement with lattice data. Among six trigluon glueballs, the produced masses for 1±- and 2-- are in good agreement with lattice data, and the produced masses for 0--, 0+- and 2+- are around 1.5 GeV lighter than lattice results. This result might indicate that the three trigluon glueballs of 0--, 0+- and 2+- are dominated by the three-gluon condensate contribution.
We calculate the mass spectra of the singly charmed baryons (Λc+, Σc0, Ξc0 and Ωc0) using the hypercentral constituent quark model (hCQM). The hyper color Coulomb plus linear potential is used to calculate the masses of positive (up to Jp=(7+)/(2)) and negative (up to Jp=(9-)/(2)) parity excited states. The spin-spin, spin-orbital and tensor interaction terms are also incorporated for mass spectra. We have compared our results with other theoretical and lattice QCD predictions for each baryon. Moreover, the known experimental results are also reasonably close to our predicted masses. By using the radial and orbital excitation, we construct Regge trajectories for the baryons in the (n,M2) plane and find their slopes and intercepts. Other properties of these baryons, like magnetic moments, radiative transitions and radiative decay widths, are also calculated successfully.
Flavor violating Higgs signals, such as the top FCNC decay t→ch0 and the LFV Higgs decay h0→τμ, have been studied at the LHC. These signals can arise within the general Two-Higgs Doublet Model (THDM), where each Higgs doublet couples to all fermion types through Yukawa matrices Y1f and Y2f. The Yukawa matrices can be assumed to have the same form or they could have different structures. In this paper we study the case when both Y1f and Y2f have completely different forms, but in such a way that they complement to produce a specific hermitian mass matrix. We find that for specific four-zero textures, the flavor violating Higgs couplings depend only on the free parameters tan β, γf and the fermion masses. We use the current bounds on the low energy processes to derive constraints on the heavy Higgs boson mass, tan β and γf. Then, we use these constraints to evaluate the LFV Higgs decays, which reach branching ratios that could be tested at the LHC.
Having a precise knowledge of the charm quark component can lead to a better understanding of the fundamental structure of the nucleon. Furthermore, the charm quark distribution function plays an important role in the study of many processes which are sensitive to the charm quark content of the nucleon. In the standard global analysis of parton distribution functions (PDFs), the charm quark distribution arises perturbatively through the splitting of the gluon int→charm-anticharm pairs in the DGLAP evolution equations. Nevertheless, the existence of nonperturbative intrinsic charm quarks in the proton has also been predicted by QCD. In this paper, we study some phenomenological models within the light-cone framework to predict the nonperturbative intrinsic charm quark content of the nucleon. We investigate the impact of these models on the prediction of γ+c-jet production in pp collisions at the LHC and compare our results on pp→γ+c-jet with the experimental data of D0.
In this paper, we investigate the decay of the Higgs boson to J/ψ(Υ) plus a photon based on NRQCD factorization. For the direct process, we calculate the decay width up to QCD NLO. We find that the decay width for process H→J/ψ(Υ)+γ direct production at the LO is significantly reduced by the NLO QCD corrections. For the indirect process, we calculate the H→γ*γ with virtual γ substantially decaying to J/ψ(Υ), including all the SM Feynman diagrams. The decay width of indirect production is much larger than the direct decay width. Since it is very clean in experiment, the H→J/ψ(Υ)+γ decay could be observable at a 14 TeV LHC and it also offers a new way to probe the Yukawa coupling and New Physics at the LHC.
The extrapolation of nucleon axial charge gA is investigated within the framework of heavy baryon chiral effective field theory. The intermediate octet and decuplet baryons are included in the one loop calculation. Finite range regularization is applied to improve the convergence in the quark-mass expansion. The lattice data from three different groups are used for the extrapolation. At physical pion mass, the extrapolated gA are all smaller than the experimental value.
Excited states in the odd-proton nucleus 125Cs were investigated by means of in-beam γ-ray spectroscopy. The πg7/2 band is observed to fork into a ΔI=1 coupled band and a ΔI=2 decoupled band at high spins. To assign the possible configurations of these two bands, experimental B(M1)/B(E2) ratios and signature splittings have been evaluated for the ΔI=1 band, and calculations based on the geometrical model, cranked shell model and total Routhian surfaces model have been performed. They are suggested to be a near-oblate band built on the (πg7/2/d5/2)⊗(νh11/2)2 configuration and a prolate band built on the πg7/2⊗(π h11/2)2 configuration, respectively.
We have reanalyzed reaction cross sections of 16N on a 12C target. The nucleon density distribution of 16N, especially surface density distribution, was extracted using the modified Glauber model. On the basis of dilute surface densities, the 15N(n, γ)16N reaction is discussed within the framework of the direct capture reaction mechanism. The calculations agree quite well with the experimental data.
In the framework of Strutinsky's approach, we calculated the shell and the residual pairing correction energies for 5569 even-even nuclei in the range 72≤Z≤282 and 96≤N≤540. Quasi-magic numbers and deformed islands of stability that reside in a range defined by Green's formula and the two-neutrons drip line are introduced. We present 36 quasi-magic proton and 53 quasi-magic neutron magic numbers that contribute to the formation of 133 deformed islands of stability along the N-Z space. The quasi-magic proton and neutron magic numbers volatile as the mass number increases and other magic numbers take over. Consequently, the deformed islands of stability fail to exhibit a pattern along the search space covered.
Multiple chiral doublet bands (MχD) in the 80, 130 and 190 mass regions are studied by the model of γ=90° triaxial rotor coupled with identical symmetric proton-neutron configurations. By selecting a suitable basis, the calculated wave functions are explicitly exhibited to be symmetric under the operator Â, which is defined as rotation by 90° about the 3-axis with the exchange of valance proton and neutron. We found that both M1 and E2 transitions are allowed between levels with different values of A, while they are forbidden between levels with same values of A. Such a selection rule holds true for MχD in different mass regions.
We report on a theoretical study of the hidden charm N*cc states in the γp→D*0Λc+ reaction near threshold within an effective Lagrangian approach. In addition to the contributions from the s-channel nucleon pole, the t-channel D0 exchange, the u-channel Λc+ exchange and the contact term, we study the contributions from the N*cc states with spin-parity JP=1/2- and 3/2-. The total and differential cross sections of the γp→D*0Λc+ reaction are predicted. It is found that the contributions of these N*cc states give clear peak structures in the total cross sections. Thus, this reaction is another new platform to study the hidden-charm states. It is expected that our model calculation may be tested by future experiments.
Within the framework of the dinuclear system (DNS) model, the fusion reactions leading to the compound nuclei 274Hs* and 286Cn* are investigated. The fusion probability as a function of DNS excitation energy is studied. The calculated results are in good agreement with the available experimental data. The obtained results show that the fusion probabilities are obviously enhanced for the reactions located at high place in potential energy surface, although these reactions may have small values of mass asymmetry. It is found that the enhancement is due to the large potential energy of the initial DNS.
The thermonuclear rate of the 50Fe(p, γ)51Co reaction in the Type I X-ray bursts (XRBs) temperature range has been reevaluated based on a recent precise mass measurement at CSRe Lanzhou, where the proton separation energy Sp=142±77 keV has been determined firstly for the 51Co nucleus. Comparing to the previous theoretical predictions, the experimental Sp value has much smaller uncertainty. Based on the nuclear shell model and mirror nuclear structure information, we have calculated two sets of thermonuclear rates for the 50Fe(p, γ)51Co reaction by utilizing the experimental Sp value. It shows that the statistical-model calculations are not ideally applicable for this reaction primarily because of the low density of low-lying excited states in 51Co. In this work, we recommend that a set of new reaction rates based on the mirror structure of 51Cr should be incorporated in future astrophysical network calculations.
The discovery of the neutrino mixing angle θ13 opens new opportunities for the discovery of leptonic CP violation at high intensity neutrino beams. MOMENT, a future neutrino facility with a high-power proton beam of 15 MW from a continuous-wave linac, is focused on that discovery. The high power of the proton beam causes extreme radiation conditions for the facility and especially for the target station, where the pion capture system of five superconducting solenoids is located. In this paper initial studies are performed for the effects of the radiation on the solenoid structure and the area surrounding it. A concept cooling system is also proposed.
Hefei Light Source (HLS) has been upgraded to improve the quality and stability of the synchrotron light, and the new facility is named HLSII. However, a final accurate adjustment is required to smooth the beam orbit after the initial instalment and alignment of the magnets. We implement a reliable smoothing method for the beam orbit of the HLSII storage ring. In addition to greatly smoothing and stabilizing the beam orbit, this method also doubles the work efficiency and significantly reduces the number of magnets adjusted and the range of the adjustments.
With the advances in accelerator science and technology in recent decades, the accelerator community has focused on the development of next-generation light sources, for example diffraction-limited storage rings (DLSRs), which require precision control of the electron beam energy and betatron tunes. This work is aimed at understanding magnet hysteresis effects on the electron beam energy and lattice focusing in circular accelerators, and developing new methods to gain better control of these effects. In this paper, we will report our recent experimental study of the magnetic hysteresis effects and their impacts on the Duke storage ring lattice using the transverse feedback based precision tune measurement system. The major magnet hysteresis effects associated with magnet normalization and lattice ramping are carefully studied to determine an effective procedure for lattice preparation while maintaining a high degree of reproducibility of lattice focusing. The local hysteresis effects are also studied by measuring the betatron tune shifts which result from adjusting the setting of a quadrupole. A new technique has been developed to precisely recover the focusing strength of the quadrupole by returning it to a proper setting to overcome the local hysteresis effect.
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