118383365
NMSSM explanations of the Galactic center gamma ray excess and promising LHC searches
The Galactic Center Excess (GCE) is explained in the framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) with a $Z_3$ discrete symmetry. We show that a resonant CP-odd Higgs boson with mass twice that of the Dark Matter (DM) candidate is favoured. Meanwhile, the DM candidate is required to have relatively large coupling with the $Z$ boson through its Higgsino component in order to obtain correct DM relic density. Its LHC discovery potential via four signatures is discussed in detail. We find that the most sensitive signals are provided by the Higgsino-like chargino and neutralino pair production with their subsequent decays into $W$ bosons, $Z$ bosons, and DM. The majority of the relevant parameter space can be probed at the Large Hadron Collider with a centre-of-mass energy of 14 TeV and an integrated luminosity 1000 fb$^{-1}$.
118485854
Natural NMSSM confronting with the LHC7-8
Taoli Cheng, Jinmian Li, Tianjun Li, and Qi-Shu Yan 1State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China 2School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China 3George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA 4School of Physics Sciences, University of Chinese Academy of Sciences, Beijing 100049, China and 5Center for High Energy Physics, Peking University, Beijing 100871, China
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.
119234621
A Rediatively Light Stop Saves the Best Global Fit for Higgs Boson Mass and Decays
The LHC discovered the Standard Model (SM) like Higgs boson with mass around 125 GeV. However, there exist hints of deviations from Higgs decays. Including the Tevatron data, the deviations can be explained by the extremely mixed stop sector in the sense of best global fit (BGF). We analyze the relations among the competing reduced coupling hGG, Higgs boson mass,and LHC stop mass m_{\wt t_1} lower bound at the tree- and one-loop level. In particular, we point out that we use the light stop running mass in the Higgs boson mass calculation while the light stop pole mass in the Higgs decays. So the gluino radiative correction on the light stop mass plays the crucial role. Its large negative correction saves the GBF in the Minimal Supersymmetric SM (MSSM) and the next to the MSSM (NMSSM) constrained by the perturbativity. Moreover, a light stop is predicted: in the MSSM if we set the gluino mass M_3\lesssim4 TeV, we have m_{\wt t_1}<m_t; while in the NMSSM, imposing the least tuning condition we get m_{\wt t_1}\simeq130 GeV for M_3\simeq1.5 TeV.
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.
119198715
Electroweak supersymmetry around the electroweak scale
Inspired by the phenomenological constraints, LHC supersymmetry and Higgs searches, dark matter search as well as string model building, we propose the electroweak supersymmetry around the electroweak scale: the squarks and/or gluinos are around a few TeV while the sleptons, sneutrinos, bino and winos are within 1 TeV. The higgsinos can be either heavy or light. We consider the bino as the dominant component of dark matter candidate, and the observed dark matter relic density is achieved via the neutralino–stau coannihilations. Considering the Generalized Minimal Supergravity (GmSUGRA), we show explicitly that electroweak supersymmetry can be realized, and gauge coupling unification can be preserved. With two scenarios, we study the viable parameter spaces that satisfy all the current phenomenological constraints, and we present the concrete benchmark points. Furthermore, we comment on the fine-tuning problem and LHC searches.
119583997
Extended domain of validity of the Hauser-Feshbach formula in the framework of the statistical theory
It is shown that in the domain of overlapping resonances the Hauser-Feshbach formula can be derived in the framework of the statistical theory of nuclear reactions even when the energy dependence of the characteristic quantities (e.g., level density and widths) is not neglected.
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.
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.
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.
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.