121182373
Anticorrelated angular-momentum distributions in heavy-ion collisions
Abstract The angular-momentum distributions of the fragments in deeply inelastic heavy-ion collisions are shown to be anti-correlated. We derive the correlation coefficient in a transport model. The correlation angle increases towards mass symmetry and reaches —45° for symmetric fragmentation.
124105774
THE ANGULAR-MOMENTUM CORRELATION COEFFICIENT IN DISSIPATIVE HEAVY-ION COLLISIONS
Based on a transport equation of the Fokker-Planck type the correlations in theangular-momentum distributions of binary fragments in deeply inelastic heavy-ion col-lisions are investigated. A strong anticorrelation is found due to the centrifugal part ofthe driving potential. The correlation angle increases towards mass symmetry andreaches 45° for symmetric fragmentation.
119856045
Distribution of the dissipated angular momentum in heavy-ion collisions
The angular-momentum distributions of both fragments in low-energy heavy-ion collisions are calculated in a nonequilibrium-statistical model. The distribution functions are obtained analytically via moment expansion on the basis of a transport equation. They include the correlations between the two fragments. In conjunction with a phenomenological model for the description of the relative motion we compute fragment angular-momentum distributions as a function of energy loss and compare with experimental data.
119232543
On naturalness of the MSSM and NMSSM
A bstractWith a bottom-up approach, we consider naturalness in the MSSM and NMSSM. Assuming the light stops, the LHC gluino search implies that the degree of fine tuning in both models is less than 2.5%. Taking the LHC hints for the SM-like Higgs boson mass mh ~ 125 GeV seriously, we find that naturalness will favor the NMSSM. We study the Higgs boson mass for several scenarios in the NMSSM: (1) A large λ and the doublet-singlet Higgs boson mixing effect pushing upward or pulling downward mh. The former case can readily give the di-photon excess of the Higgs boson decay whereas the latter case can not. However, we point out that the former case has a new large fine-tuning related to strong λ−RGE running effect and vacuum stability. (2) A small λ and the mixing effect pushing mh upward. Naturalness status becomes worse and no significant di-photon excess can be obtained. In these scenarios, the lightest supersymmetric particle (LSP) as a dark matter candidate is strongly disfavored by the XENON100 experiment. Even if the LSP can be a viable dark matter candidate, there does exist fine-tuning. The above naturalness evaluation is based on a high mediation scale for supersymmetry breaking, whereas for a low mediation scale, fine-tuning can be improved by about one order.
120078295
A plastic scintillating fiber position detector in vacuum for the test beam facility at BEPC II -LINAC
Two plastic scintillating fiber position detectors for charged particles have been designed, built and installed inside the vacuum tube near two sides of the DM2 deflection magnet on the E3 beam line of the test beam facility at the BEPC-LINAC. A one-dimensional position resolution of similar to 1 mm with a sensitive area of 60 mm x60 mm has been obtained for this detector.
118439743
Implications of Higgs Sterility for the Higgs and Stop Sectors
The LHC data implies that the newly discovered Higgs boson h may be sterile (highly SM-like). In supersymmetric SMs (SSMs), Higgs couplings are often modified by Higgs mixing and stop loop corrections, so we study the Higgs sterility in the Higgs and stop sectors in two SSMs: (I) The Minimal SSM (MSSM). In the nearly decoupling region, the doublet-doublet mixing effect can only enhance C_{hb\bar b} by 2m_Z^2/M_A^2. Sterility places M_A\gtrsim 900 GeV. But it hardly constrains the stop sector due to the heaviness of Higgs boson mass m_h; (II) The next to MSSM(NMSSM). In the presence of doublet-singlet mixing, the mixing structure is complicated. We find a simple approximation to understand Higgs sterility and its implications, says the amount of pushing-up m_h\lesssim 5 GeV while the pulling-down scenario is favored. Stops can be light here, so Higgs sterility significantly constrains them directly and indirectly except for blind spots. We also study the LHC features of the whole stop sector facing a sterile Higgs and find that, in virtue of decays between stops and sbottom, characteristic signatures like same-sign leptons and multi b-jets are promising probes.