121169679
What does the observed rapidity dependence of the multiplicity distribution in e+e− annihilation processes tell us?
Abstract The recent multiplicity distribution data from PEP-HRS for limited rapidity intervals in e + e − annihilation processes at 29 GeV is analysed in a model-independent way. It is shown that the observed rapidity dependence can be reproduced by using standard statistical procedures without introducing any adjustable parameter. Implications of this fact, and the KNO scaling/nonscaling problem, are discussed in connection with present and future experiments.
119827604
A model for the peripheral process in ultrarelativistic nucleus-nucleus collisions
A model for the peripheral process in ultrarelativistic nucleus-nucleus collisions is proposed to explain the first experimental results of interactions of oxygen nuclei in nuclear emulsions at the highest energy now available. The fraction of the interactions producing `white' stars and the mean value of NH for different incident energies and colliding nuclei are given.
117789207
Massive meson fluctuation in NJL model
Based on the self-consistent scheme beyond the mean-field approximation in the large N-c expansion, including current quark mass explicitly, a general scheme of SU(2) NJL model is developed. To ensure the quark self-energy expanded in the proper order of N-c, an approximate internal meson propagator is deduced, which is in order of O(1/N-c). In our scheme, adopting the method of external momentum expansion, all the Feynman diagrams are calculated in a unified way by only expanding the quark propagator. Our numerical results show that, different from the mean-field approximation in which the explicitly chiral symmetry breaking is invisible, the effect of finite pion mass can be seen clearly when beyond the mean-field approximation.
123725926
Quark propagator with a quark mass term in the color-superconducting phase
18431189
Nuclear Effects on Charmonium Production
$J/\psi$ and $\psi'$ production cross sections in fixed-target experiment is calculated, considering the contributions from both color-singlet and color-octet mechanisms.The results are applied to the investigations of the $J/\psi$ suppression and the $\psi'/\psi$ ratio problems in p-A collisions. The results agree with the experimental data as the $(c \bar c)-$nucleon absorption cross sections $\sigma_{abs}^8\simeq 10mb $ for $(c \bar c)_8$ and $\sigma_{abs}^1\simeq 0mb $ for $(c \bar c)_1$. The model is further used to investigate A-A collisions when comover absorption mechanism is also considered. It is found that the observed experiment data of $J/\psi$ and $\psi'/\psi$ ratio in S-U collisions and Pb-Pb collisions can not be explained consistently within this model. The possibility of QGP formation in S-U and Pb-Pb collisions is also discussed.
118203227
Meson effects on the chiral symmetry breaking and restoration
Based on the self-consistent chiral symmetric scheme of the SU(2) Nambu-Jona-Lasinio model, the meson effects have been investigated on the chiral symmetry breaking vacuum and chiral symmetry restoration by exactly calculating the next-to-leading (NLO) order Feynman diagrams in the 1/Nc expansion.
119308558
Vacuum stability and Higgs diphoton decay rate in the Zee-Babu model
A bstractAlthough recent Higgs data from ATLAS and CMS are compatible with a Standard Model (SM) signal at 2σ level, both experiments see indications for an excess in the diphoton decay channel, which points to new physics beyond the SM. Given such a low Higgs mass mH ~ 125 GeV, another sign indicating the existence of new physics beyond the SM is the vacuum stability problem, i.e., the SM Higgs quartic coupling may run to negative values at a scale below the Planck scale. In this paper, we study the vacuum stability and enhanced Higgs diphoton decay rate in the Zee-Babu model, which was used to generate tiny Majorana neutrino masses at two-loop level. We find that it is rather difficult to find overlapping regions allowed by the vacuum stability and diphoton enhancement constraints. As a consequence, it is almost inevitable to introduce new ingredients into the model, in order to resolve these two issues simultaneously.
117946473
Black-hole creation in quantum cosmology
— It is proven that the probability of a black hole created from the de Sitter space-time background, at the WKB level, is the exponential of one quarter of the sum of the black hole and cosmological horizon areas, or the total entropy of the universe. This is true not only for the spherically symmetric cases of the Schwarzschild or Reissner-Nordstrom black holes, but also for the rotating case of the Kerr black hole and the rotating charged case of the Newman black hole. The de Sitter metric is the most probable evolution at the Planckian era of the universe.
119230665
TeV-scale Type-II Seesaw Models and Possible Collider Signatures
A natural extension of the standard model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a 6×6 neutrino mass matrix. We show that three light Majorana neutrinos (i.e., the mass eigenstates of νe, νμ and ντ) are exactly massless, if and only if $M_{L} = M_{\rm D}M^{-1}_{\rm R}M^{T}_{\rm D}$ exactly holds in this seesaw model. We propose three simple Type-II seesaw scenarios with broken A4 × U(1)x flavor symmetry to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the 3 × 3 neutrino mixing matrix in the future long-baseline neutrino oscillation experiments.
124312353
The Hierarchy Problem and Lifshitz Type Quantum Field Theory
We study the Lifshitz type extension of the standard model (SM) at UV, with dynamical critical exponent z=3. One loop radiative corrections to the Higgs mass in such a model is calculated. Our result shows that, the Hierarchy problem, which has initiated many excellent extension of the minimal SM, can be weakened in the z=3 Lifshitz type quantum field theory.
119269487
Relatively large Theta13 from modification to the tri-bimaximal, bimaximal and democratic neutrino mixing matrices
A bstractInspired by the indication of a relatively large θ13 from accelerator and reactor neutrino oscillation experiments, we provide a systematic study of general modifications to the three well-studied neutrino mixing patterns, i.e., tri-bimaximal, bimaximal and democratic lepton mixing matrices. The correlation between θ13 and the other two neutrino mixing angles are derived for each types of additional rotations. Predictions on θ12 and θ23 are also studied. Our study shows that, although some types of additional rotations are already excluded by the current global fit data of neutrino mixing angles, several types of additional rotations still survive. Our results may provide a guideline for the model building in neutrino physics.